Electronic Engineering Glossary Terms

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Electronic Engineering Glossary Terms

ABSORPTION. Dissipation of radio or sound waves as they interact with matter. The absorbing of light waves without reflection or refraction.

ABSORPTION, LAW OF. In Boolean algebra, the law which states that the odd term will be absorbed when a term is combined by logical multiplication with the logical sum of that term and another term, or when a term is combined by logical addition with the logical product of one term and another term (for example, A(A + B) = A + AB = A).

ABSORPTION WAVEMETER. An instrument used to measure audio frequencies. Refer to Manufacturers of Test Equipment.

ABS PLASTIC. A type of plastic formed by Acrylonitrilt Butadiene Styrene and other chemicals. See [Fire Retardant Materials]

ACCELERATING ANODE. An electrode charged several thousand volts positive and used to accelerate electrons toward the front of a cathode-ray tube.

ACCELERATION SERVOSYSTEM. A servo-system that controls the acceleration (rate of change in velocity) of a load.

ACCELEROMETER. A device that measures the acceleration to which it is subjected and develops a signal proportional to it. Manufacturers of Accelerometers and other sensor vendors.

ACCEPTOR IMPURITY. An impurity which, when added to a semiconductor, accepts one electron from a neighboring atom and creates a hole in the lattice structure of the crystal. Also called Trivalent Impurity.

ACCESS BUS. Is a low speed 4-wire serial bus once used on Personal Computers. Access.Bus uses the I2C [IIC] bus as the electrical hardware interface. The Access bus has a maximum speed is 100kbps over a maximum cable distance of 10 meters, however a repeater may be used. The 4 wires of the interface bus are power/ground, Send Data [SDA] and Serial Clock [SCL]. Refer to the following page for a description of the Access Bus interface page.

ACCESSORY. An assembly of a group of parts or a unit which is not always required for the operation of a set or unit as originally designed but serves to extend the functions or capabilities of the set, such as headphones for a radio set supplied with a loudspeaker, a separate power unit for use with a set having a built-in power supply, or a remote control unit for use with a set having integral controls.

ACCESS TIME. The difference in time between when data is requested and when data is delivered. The time lapsed between a given command and when the function is performed.

AC COUPLING. The interconnection between two circuits through a capacitor or other device which passes AC voltage but blocks any DC component. In the circuit below C3 blocks the DC component of Q1 from effecting the operation of Q2.

 

AC Coupled Transistor Amplifier

ACORN TUBE. A very small tube with closely spaced electrodes and no base. The tube is connected to its circuits by short wire pins that are sealed in a glass or ceramic envelope. The acorn tube is used in low power uhf circuits.

ACOUSTIC NOISE. The unintended sound a component produces while operating. Some fields apply this to mean an audible sound, while other fields take it to mean any sound.

ACOUSTICS. The science of sound.

ACTIVE HIGH. Refers to a non-inverted output, the output is true when high and false when low. When the Sum-of-Products expression is true the output is high.

ACTIVE LOW. Refers to an inverted output, the output is true when low and false when high. When the Sum-of-Products expression is true the output is low.

ACTIVE SATELLITE. A satellite that amplifies the received signal and retransmits it back to earth.

ACTIVE SERIAL INTERFACE. A term used with programming an FPGA. In the Active Serial [AS] configuration scheme, Altera FPGAs are configured with serial configuration devices. Also called Active Serial Mode, or Active Serial Scheme; where Active Serial may be Abbreviated as AS. Related terms include Passive Serial Interface, and JTAG Interface.

Actuating force. The force applied to the actuator to operate the contacts.

ACTUATOR. The part of a switch that is acted upon to cause the switch to change contact connections; for example, toggle, pushbutton, and rocker.

ADAPTER. A component that translates from one type of fixture to another. As in a connector that translates from an SMA to BNC connector.

BNC Adapter

However there are adapters that mate to the same styles, as in BNC-to-BNC adapters.

ADB. The ADB or Apple Desktop Bus was a serial bus used by Apple computer to drive the mouse and keyboard interfaces. The cable consisted of one data line [ADB], a power line [+5v] and a ground line. The maximum data rate was 125kbps, actual bus speed was much lower. The ADB bus was rendered obsolete by the introduction of the Firewire interface on Apple Computer products.

AES/AES-256. Advanced Encryption Standard used by the US government.

AES/EBU. Audio Engineering Society/European Broadcasting Union. AES/EBU is one of the common names for a digital audio transfer standard. The standard is also known as XLR because the AES/EBU digital interface is usually implemented using 3-Pin XLR connectors, which happens to be the same type connector used in a professional microphone. One cable carries both left and right-channel audio data. AES/EBU is an alternative to the S/PDIF [Sony/Philips Digital Interface] standard. S/PDIF is a an audio transfer file format which uses an RCA connector.

 

AGP BUS. The Accelerated Graphics Port bus was widely used as a video expansion bus on personal computers from 1997 to 2006. The AGP electrical standard was derived from the Parallel PCI bus. The fastest speed; AGP 8x used a 533MHz clock with 32 bytes/clock transfers, with a Bandwidth of 2.1GBps. The AGP Bus was rendered obsolete by the introduction of the PCIe interface [PCI Express].

AIR-CONTROL PANEL. Panel that monitors the dry-air input at each user equipment. [Manufacturers of Environmental Alarms]

AIR-CORE INDUCTOR. An inductor composed of two or more coils that are wound around a non-metallic core. [Manufacturers of Inductors]

AIR-CORE TRANSFORMER. A transformer composed of two or more coils that are wound around a non-metallic core. [Manufacturers of Transformers]

Inductor

A-LAW. A companding algorithm used in digital communications systems. Refer to the telcom section for A-Law IC Functions.

ALIASING. See Nyquist Sampling Rate

ALLIGATOR CLIP. See Types of Alligator Clips

Alloy. A mixture of two or more materials, at least one of which is a metal.

ALLOYED JUNCTION. A junction formed by re-crystallization of a molten region of P-type material on an N-type substrate, or vice versa.

ALPHA. The emitter-to-collector current gain in a common-base circuit of a transistor. Also refer to the section covering Transistor Terms. [Transistor Manufacturers]

ALTERNATING CURRENT. [AC] An electrical current that constantly changes amplitude and changes polarity at regular intervals.

ALTITUDE. The vertical distance of an aircraft or object above a given reference, such as ground or sea level. Additional reference information may be obtained via Airborne Environment Classification per MIL-HDBK-217.

ALUMINUM CREEP. The movement of aluminum wire from a point where pressure is applied. The "retreat" of heated aluminum wire as it cools.

 

AMBIENT TEMPERATURE. The temperature of the air or liquid surrounding any object. The surrounding temperature such as the temperature of air surrounding a conductor in a compartment or within a piece of equipment.

AMERICAN WIRE GAUGE (AWG). The standards adopted in the United States for the measurement of wire sizes. AWG Chart

AMMETER. An instrument for measuring the amount of electron flow (in amperes). The instrument may measure direct current flow, alternating current flow or both depending on its construction. [Companies that produce Test Equipment]

AMPACITY. Current-carrying capacity of electric conductors expressed in amperes [see AWG Copper Wire table]. The current in amperes that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. Also refer to the AWG Aluminum Wire table for conductor ampacity.

AMPERE. The basic unit of electrical current. Applying one volt across a one ohm resistor will cause a current of one ampere to flow. The letter 'I' is used to denote current.

AMPERE-HOUR. Defined as a current of one ampere flowing for one hour. Multiply the current in amperes by the time of flow in hours, the result is the total number of ampere-hours.

AMPERE-TURN. The magnetomotive force developed by 1 ampere of current flowing through a coil of one turn.

AMPERITE (BALLAST) TUBE. A current-controlling resistance device designed to maintain substantially constant current over a specified range of variation in applied voltage or resistance of a series circuit.

AMPLIDYNE. A DC generator in which a small dc voltage applied to field windings controls a large output voltage from the generator. In effect, an amplidyne is a rotary amplifier that often times produces gain of approximately 10,000.

AMPLIFICATION. The process of increasing a signal in amplitude (as of voltage or current). The ratio of output magnitude to input magnitude in a device that is intended to produce an output that is an enlarged reproduction of its input.

AMPLIFICATION FACTOR. The voltage gain of an amplifier with no load on the output.

AMPLIFIER. The device that provides amplification (the increase in current, voltage, or power of a signal) without appreciably altering the original signal. Refer here for Transistor Amplifier Circuits

AMPLITUDE. The size of a signal as measured from a reference line to a maximum value above or below the line. Generally used to describe voltage, current, or power.

AMPLITUDE DISTORTION. Distortion that is present in an amplifier when the amplitude of the output signal fails to follow exactly any increase or decrease in the amplitude of the input signal.

AMPLITUDE MODULATION. Any method of varying the amplitude of an electromagnetic carrier frequency in accordance with the intelligence to be transmitted.

Amplitude Modulation

AMPLITUDE STABILITY. Amplitude stability refers to the ability of the oscillator to maintain a constant amplitude in the output waveform.

AM Receiver Block Diagram

AM Receiver. A receiver that decodes an Amplitude Modulated signal to recover encoded information.

 

AND GATE. An electronic gate whose output is energized only when every input is in its prescribed state. An AND gate performs the function of the logical "AND"; also called an AND circuit. A binary circuit, with two or more inputs and a single output, in which the output is a logic 1 only when all inputs are a logic 1 and the output is a logic 0 when any one of the inputs is a logic 0. [IC Manufacturers]

AND Gate Symbol

ANGLE. Refer to this page for terms relating to Angle Definitions.

ANGSTROM. 10^-10 meter.

ANGSTROM UNIT. The unit used to define the wavelength of light waves.

ANISOTROPIC. The property of a radiator that allows it to emit strong radiation in one direction.

ANODE. A positive electrode of an electrochemical device (such as a primary or secondary electric cell) toward which the negative ions are drawn. The semiconductor-diode terminal that is positive with respect to the other terminal when the diode is biased in the forward direction. Also refer to Diode Definitions.

 

Diode

ANNEAL. To soften and relieve strains in any solid material, such as metal or glass, by heating to just below its melting point and then slowly cooling it. This also generally lowers the tensile strength of the material, while improving its flex life.

ANNULAR RING. The portion of a conductive material that completely surrounds a hole. See Minimum Annular Ring for more data and a graphic

ANSI. American National Standards Institute.

ANTENNA. A conductor or set of conductors used to radiate RF energy into space or to collect RF energy from space or to do both. [Antenna Manufacturers], [Antenna Terms]

Antenna

ANTENNA BEAM WIDTH. Width of a radar beam measured between half-power points. [Radar Terms]

ANTENNA COUPLER. A device used for impedance matching between an antenna and a transmitter or receiver.

ANTENNA SYSTEM. Routes RF energy from the transmitter, radiates the energy into space, receives echoes, and routes the echoes to the receiver. [Antenna Tracking Systems]

ANTIPADS. are clearances to provide separation between vias and voltage planes to avoid shorting the signals to the voltage rails as the via traverses the Printed Wiring Board. The diameter of the Antipad should be minimized to reduce EMI effects, but maximized to decrease shorting and voltage breakdown of adjacent signals. Definitions of Printed Wiring Board Terms

ANTISEIZE COMPOUND. A silicon-based, high-temperature lubricant applied to threaded components to aid in their removal after they have been subjected to rapid heating and cooling.

ANTITRANSMIT-RECEIVE TUBE (atr). A tube that isolates the transmitter from the antenna and receiver. Used in conjunction with a tr tube.

 

Aperature Time. The time it takes for a switch to turn from ON to OFF.

APPARENT DRIFT. The effect of the earth’s rotation on a gyro that causes the spinning axis to appear to make one complete rotation in one day.

APPARENT POWER. That power apparently available for use in an ac circuit containing a reactive element. It is the product of effective voltage times effective current expressed in volt-amperes. It must be multiplied by the power factor to obtain true power available.

ARBITRATION. The process of selecting one communication node on a bus over another.

ARC. A visible electrical discharge between separated contacts.

ARCHITECTURE. Defines how a system is connected or interconnected and in some cases how the components are interconnected.

ARMATURE. In a relay, the movable portion of the relay. The windings in which the output voltage is generated in a generator or in which input current creates a magnetic field that interacts with the main field in a motor.

ARMATURE LOSSES. Copper losses, eddy current losses, and hysteresis losses that act to decrease the efficiency of armatures.

ARMATURE REACTION. The effect in a dc generator of current in the armature creating a magnetic field that distorts the main field and causes a shift in the neutral plane.

ARMOR. A flexible metal 'shield' that protects a component from damage. Refer to Cable Armor definition.

ARRAY. A group of devices or components. A number of devices contained within a single package, but not connected to each other. Also see Transistor Arrays. Types of Diode Arrays, or Resistor Arrays. Graphic; Transistor Array in an LCC package. Also see Antenna Array [within the Antenna Dictionary].

Transistor Array

 

ARMSTRONG OSCILLATOR. A type of oscillator. The ARMSTRONG OSCILLATOR is used to produce a sine-wave output of constant amplitude and of fairly constant frequency within the rf range. Types of Oscillator Vendors.

Armstrong Osc

ARTIFICIAL TRANSMISSION LINE. An LC network that is designed to simulate characteristics of a transmission line.

ASCII. The American Standard Code for Information Interchange. A common method used by computers to code alphabetic letters into a binary code. Refer to table of ASCII Codes.

ASPECT RATIO. The ratio between the width of an object and the height of the object.

ASSEMBLY. A number of parts or subassemblies, or any combination thereof, joined together to perform a specific function. As in a Printed Wiring Board Assembly, which comprises the Printed Wiring Board [PWB] and all the components attached to the PWB. Also refer to PWB Terms [within the PCB Dictionary].

ASTABLE MULTIVIBRATOR. A multivibrator that has no stable state. Also called free-running because it alternates between two different output voltage levels during the time it is on. The frequency is determined by the RC time constant of the coupling circuit. Also refer to a 555 Astable Circuit, or Transistor Astable Multivibrator Circuit.

 

Astable Multivibrator

ASTIGMATISM. An aberration of a lens with spherical surfaces such that the image of a point not lying on the optical axis is a pair of short lines normal to each other and at slightly different distances from the lens. Radial and tangential lines are in focus in different image planes.

ASYMMETRICAL MULTIVIBRATOR. A multivibrator that generates rectangular waves.

ASYNCHRONOUS COMMUNICATION. Communication in which no clocking information is passed between stations.

ASYNCHRONOUS LOGIC. A Digital circuit whose output only depends on the combination logic gates used and the propagation delay through those gates. A logic circuit that does not use a Flip Flop or other synchronizing element.

ASYNCHRONOUS TRANSMISSION. Parallel Information is synchronized individually [per transfer] by hand-shaking as in DAV [Data Available] and DAC [Data Accepted], or REQ and ACK lines. Serial Information is synchronized individually [per block] via 'START' and 'STOP' bits. Information is passed between nodes with out a separate clock signal to indicate when data on the transmission line is valid.

 

ATTENUATION. The decrease in magnitude of a signal as it travels through any transmitting medium, such as a cable or circuitry. The ability of a filter circuit to reduce the amplitude of unwanted frequencies to a level below that of the desired output frequency. More detail on 24AWG twisted pair copper wire attenuation
[Resistor Chip Attenuator Manufacturers, RF Attenuator Manufacturers]

 

L-Pad Attenuator Circuit

ATTENUATOR PAD. A component inserted into a transmission path to introduce transmission loss.

ATTRACTION. The force that tends to make two objects approach each other. Attraction exists between two unlike magnetic poles (north and south) or between two unlike static charges.

AUDIO. Sound between the range of 15 hertz (15 Hz) and 20 kilohertz (20 kHz).

AUDIO AMPLIFIER. An amplifier designed to amplify frequencies between 15 hertz (15 Hz) and 20 kilohertz (20 kHz). The transistor Q1 is the amplifier in the circuit to the right.

Audio Amplifier

AUDIO-FREQUENCY-TONE SHIFT. A system that uses amplitude modulation to change dc mark and space impulses into audio impulses.

AUTOMATIC GAIN CONTROL. [AGC] A circuit used to limit variations in the output signal strength of a receiver.

Auto Ranging. A method of automatically changing the characteristics of a circuit to accommodate changes in the input which would other wise not be within the operational range of the amplifier.

AUTO-TRANSFORMER. A transformer with only one winding. The secondary side [same winding] has two or more fixed taps or a movable tap and a common point with the primary. Also refer to Transformer Terms

Autotransformer

AVALANCHE EFFECT. A reverse breakdown effect in diodes that occurs at reverse voltages beyond 5 volts. The released electrons are accelerated by the electric field, which results in a release of more electrons in a chain or "avalanche" effect. Zener Diode Definitions

AVERAGE POWER. The peak power value averaged over the pulse-repetition time. Output power of a transmitter as measured from the start of one pulse to the start of the next pulse.

AVERAGE SEEK TIME. For Hard Disk Drives [HDD] the average seek time is the amount of time it takes for a head to seek out the specified address, which is calculated over a large number of random seeks.

AVERAGE VALUE (OF AC). The average of all the instantaneous values of one-half cycle of alternating current.

AXIAL LEAD. An electrical component that has its terminals [leads] protruding out two sides of the component body, along the devices axis. A through-hole component.

AXIS. A straight line passing through an object to denote its center.

AZIMUTH. Angular measurement in the horizontal plane in a clockwise direction.

BACKBONE. A high traffic connectivity portion of any communications network. In packet-switched networks, a primary forward direction path traced sequentially through two or more major relay or switching stations. In packet-switched networks, a backbone consists primarily of switches and inter-switch trunks. Also refer to the glossary of Network Topologies.

BACKGROUND NOISE. The total system noise in the absence of a signal [information transmission].

BACK RESISTANCE. The larger resistance value observed when you are checking the resistance of a semiconductor.

BACK SHELL. The rear portion of a connector.
Read more regarding Back Shell Definition.

BAD BLOCK / BAD SECTOR. An area on a hard disk drive that is damaged or detected as reliable.

BALANCED CODE. In PCM systems, a code constructed so that the frequency spectrum resulting from the transmission of any code word has no DC component. A code that has a finite digital sum variation [PCM]. A number of additional terms are related, use the search bar, below right, to find the correct definition.

BALANCED LINE. A cable or circuit having two identical conductors with the same electromagnetic characteristics in relation to other conductors and to ground, as in a pair of conductors.

Balanced Circuit

A transmission line consisting of two conductors in the presence of ground, capable of being operated so that when the voltages of the two conductors at all transverse planes are equal in magnitude and opposite in polarity with respect to ground, the currents in the two conductors are equal in magnitude and opposite in direction. Also refer to the Detailed Twisted-Pair definition

BALANCED MIXER. A circuit or device that generates the sum and difference frequencies of two input signals. RF Mixer Manufacturers

BALANCED PHASE DETECTOR. A circuit that controls the oscillator frequency (afc). RF Phase Detector Manufacturers

BALUN. An acronym for Balanced/Unbalanced. A device used to couple a balanced system to an un-balanced system. Read more Balun Definition. RF Transformer Manufacturers

BANANA JACK. A type of connector. The Banana Jack may be a male on one end and a female on the other end, or a completely different style connector. Read more on Banana Jack Definition.

BNC to Banana Jack Connector

BANDPASS FILTER. A filter that allows a narrow band of frequencies to pass through the circuit. Rejects or attenuates frequencies that are either higher or lower than the desired band of frequencies. A filter that ideally passes all frequencies between two non-zero finite limits and bars all frequencies not within the limits. The cutoff frequencies are normally taken to be the 3-dB points.

BAND-REJECT FILTER. A tuned circuit that does not pass a specified band of frequencies. Refer to the entry on Passive Filters.

BANDWIDTH. The width of a communication channel, measured as frequency. The difference between the highest usable frequency of a device (upper frequency limit) and the lowest usable frequency of the device (lower frequency limit) - measured at the half-power points. The difference between the limiting frequencies within which performance of a device, in respect to some characteristic, falls within specified limits. The difference between the limiting frequencies of a continuous frequency band. The capacity of a telecom line to carry signals. The necessary bandwidth is the amount of spectrum required to transmit the signal without distortion or loss of information.

BARRETTER. A type of bolometer characterized by an increase in resistance as the dissipated power rises. A Thermistor.

BASE. A reference value. A number that is multiplied by itself as many times as indicated by an exponent. Same as radix. The region between the emitter and collector of a transistor that receives minority carriers injected from the emitter. The element in a transistor that controls the flow of current carriers. The element that corresponds to the control grid of an electron tube.

Transistor Base

BASE-INJECTION MODULATOR. Similar to a control-grid modulator. The gain of a transistor is varied by changing the bias on its base.

BASIC. Beginner's All-purpose Symbolic Instruction Code, a non-graphical programming language. Also refer to a short example of HP BASIC

BATTERY. A device for converting chemical energy into electrical energy. A group of two or more connected voltaic cells. Electronic Battery Manufacturers, Industrial Battery Manufacturers

BATTERY CAPACITY. The amount of energy available from a battery. Battery capacity is expressed in ampere-hours.

BAUD. A measurement of speed based on the number of code elements or units per second. Refer to Definition of Baud.

BEAM: A column of light. The main lobe of an antenna radiation pattern. Also refer to the section covering Antenna Terms.

BEAM-LEAD CHIP. Semiconductor chip with electrodes (leads) extended beyond the wafer.

BEAM-POWER TUBE. An electron tube in which the grids are aligned with the control grid. Special beam-forming plates are used to concentrate the electron stream into a beam. Because of this action, the beam-power tube has high power-handling capabilities.

BEAM SPLITTER: A device for dividing an optical beam into two or more separate beams. Note: An example of a beam-splitter is a partially reflecting mirror.

BEARING. An angular measurement of the direction of an object from a reference direction, such as true north.

BEAT FREQUENCIES. Difference and sum frequencies, which result from the combination of two separate frequencies.

BEAT FREQUENCY. The frequency produced when two signals are mixed or combined. The beat frequency equals the difference or offset between the two frequencies. The difference between the oscillator frequency and the unknown audio frequency.

BEAT-FREQUENCY OSCILLATOR. An additional oscillator used in a receiver when it is receiving a cw signal. It provides an audible tone. Oscillator Manufacturers

BEL. A unit of measure of ratios of power levels. The unit that expresses the logarithmic ratio between the input and output of any given component, circuit, or system. bel; [B] = log 10(P1/P2) where P1 and P2 are power levels. The dB, equal to 0.1 B, is a more commonly used unit.

Bend Radius. The minimum radius to which a cable, without tensile load, can be bent for its lifetime without causing broken wires or fibers, a localized weakening of the fibers, or a permanent increase in attenuation.

BETA. The ratio of a change in collector current to a corresponding change in base current when the collector voltage is constant in a common-emitter circuit.

BIAS. Difference of potential applied to a vacuum tube or transistor to establish a reference operating level.

 

Transistor Bias Circuit

BIAS CURRENT. Current that flows through the base-emitter junction of a transistor and is adjusted to set the operating point of the transistor. Transistor Schematics

BIAS RESISTOR. A resistor used to bias a circuit. Also refer to Bias Resistor from the resistor dictionary section.

Bifilar Winding. Two or more windings with the wire of each winding alongside the other, matching turn for turn; may be either inductive or noninductive [Relays].

BIG-ENDIAN. A format for storage or transmission of binary data in which the most significant byte appears first. In a multi-byte value, the byte containing the most significant bit is stored in the lowest memory address and transmitted first, and the byte containing the least significant bit is stored in the highest memory address and transmitted last.

BINARY. A number system that uses a base, or radix, of 2. Refer to this page for terms related to Binary Definitions.

BINARY CODED DECIMAL. [BCD] A four bit binary code that only counts from 0 to 9, because decimal only counts from 0 to 9.

BIOS. [Basic Input/Output system], firmware that is permanently stored in the memory on the computer. The BIOS ROM first performs test routines when a system is switched on. The BIOS then searches for and loads the operating system from a hard disk, floppy disk, CD ROM or some other peripheral device.

BIPOLAR SIGNAL. A signal that is symmetrical around a reference point, normally ground. A signal that transitions between a positive and negative voltage [logic 1] and a reference point [logic 0]. While a Polar signal might do the same but use the positive voltage as a logic 1 [high] and a negative voltage as a logic 0 [low].

BISTABLE. A device that is capable of assuming either one of two stable states. A Flip Flop has two stable output states.

BISTABLE MULTIVIBRATOR. A multivibrator that has two stable states. It remains in one of the states until a trigger is applied. It then flips to the other stable state and remains there until another trigger is applied. Also referred to as a FLIP-FLOP. Transistor Bistable Multivibrator Circuit.

Bistable Multivibrator

BIT. A binary digit.

BIT RATE. In a bit stream, the number of bits occurring per unit time, usually expressed in bits per second.

BIT SLIP. In digital transmission, the loss of a bit or bits, caused by variations in the respective clock rates of the transmitting and receiving devices.

BLACK. The reference color of equipment that passes unclassified information. It normally refers to patch panels or sections of a circuit that work only on unclassified information.

Blade Fuse. A style of fuse that attach to the fuse holder using flat metal blades. Blade fuses are widely used in automotive applications. The fusible link is held within the plastic housing between the two blade terminals. The color of the plastic case determines the current capability. Fuse Vendors and Data.

Blade Fuse

BLEEDER CURRENT. The current through a bleeder resistor. In a voltage divider, bleeder current is usually determined by the 10 percent rule of thumb.

BLEEDER RESISTOR. A resistor used to draw a fixed current. Also refer to the dictionary of Resistor Terms.

BLOCK. A block of data moved over a bus as a unit in one transfer, using one address cycle. A group of data transferred in a group to reduce bus over-head. A Block Transfer.

BLOCK DIAGRAM. A diagram in which the major components of an equipment or a system are represented by squares, rectangles, or other geometric figures, and the normal order of progression of a signal or current flow is represented by lines. [Block Diagram example].

BLOCKED-GRID KEYING. A method of keying in which the bias is varied to turn plate current on and off.

Blocking. A condition in an amplifier, caused by over driving one or more stages, in which the amplifier is insensitive to small signals immediately after reception of a large signal. A term describing the state of a semiconductor device or junction which eventually prevents the flow of current.

Blocking Oscillator. A type of wave generator used to produce a narrow pulse, or trigger.

Block Transfer. The process, initiated by a single action, of transferring one or more blocks of data. Many electrical interfaces use Block Transfers, the VME interface being just one.

BNC Connector. A style of coaxial connector. Refer to the BNC Connector Definition [in a different dictionary].

BNC Barrel. A Female-to-Female BNC connector. Also refer to the BNC Connector Definition [in a different dictionary].

BNC TERMINATION. A resistive termination used with BNC connectors, normally 50 ohms. Also refer to Dummy Load.   BNC Termination
BOB CARD. A Break-Out-Board is used to 'break out' or separate one style of interface into another via a Printed Wiring Board.	BOB

For example a BOB card may hold some type of connector [D-sub], but break those lines out to different headers or separate screw terminals. So a normal system cable will still connect to the BOB card using the connector, but each of the lines are now accessible for debug off the individual terminals.

BODE PLOT. A graph of a linear, time-invariant system versus frequency.

BOLOMETER. A loading device that undergoes changes in resistance as changes in dissipated power occur.

BOND. The permanent joining of metallic parts or circuits assuring electrical continuity and capacity to safely conduct any current likely to be imposed.

BONDING WIRES. Fine wires connecting the bonding pads of the chip to the external leads of the package.
Refer to terms used with PWB Definitions.

BOOLEAN. Pertaining to the operations of formal logic.

BOOLEAN ALGEBRA. A system of logic dealing with on-off circuit elements associated by such operators as the AND, OR, NAND, NOR, and NOT functions.

Bootstrapping. TBD

BOUNCE TIME. The time interval between first make of the contact until the uncontrolled making and breaking of the contact ceases [switch or relays]. Also refer to Debouncing Definition

BOUNDARY CONDITIONS. The two conditions that the E-field and H-field within a waveguide must meet before energy will travel down the waveguide. The E-field must be perpendicular to the walls and the H-field must be in closed loops, parallel to the walls, and perpendicular to the E-field.

Braid. A fibrous or metallic group of filaments interwoven to form a protective covering over one or more wires. Also refer to the Cable Armor Definition.

BRANCH. An individual current path in a parallel circuit.

BREAK. An interruption in a circuit is known as a break. In a switch, the number of breaks refers to the number of points at which the switch opens the circuit; for example, single break and double break.

Break-before-Make. Contacts which interrupts one circuit before establishing the previous one.

BREAKDOWN. The phenomenon occurring in a reverse-biased semiconductor diode. The start of the phenomenon is a transition from a high dynamic resistance to one of substantially lower dynamic resistance.

BREAKDOWN VOLTAGE. The breakdown voltage is the maximum instantaneous voltage, including repetitive and non-repetitive transients, which can be applied across a junction in the reverse direction without an external means (circuit) of limiting the current. It is also the instantaneous value of reverse voltage at which a transition commences from a region of high small-signal impedance to a region of substantially lower small-signal impedance.

BRIGHTNESS CONTROL. The name given to the potentiometer used to vary the brightness of a monitor. Also refer to the Potentiometer Definition, within the dictionary of resistor terms.

BROADSIDE ARRAY. An array in which the direction of maximum radiation is perpendicular to the plane containing the elements.

BRUSHES. Sliding contacts, usually carbon, that make electrical connection to the rotating part of a motor or generator.

BUCK REGULATOR. A buck converter is a step-down DC to DC converter. Voltage Regulator Manufacturers.

BUFFER. An IC that isolates one circuit from another, as in a 7404 or 74244 Octal Buffer, [TTL vendors]. A voltage amplifier used between the oscillator and power amplifier. An allocation of memory space for temporary storage. A component or circuit that compensates for a difference in data transfer rates and data processing rates [a FIFO for example].

BUFFER AMPLIFIER. An amplifier that isolates one circuit from another. A Buffer decreases the loading effect on an oscillator by reducing the interaction between the load and the oscillator. A Transistor Buffer circuit.

BUFFERED DELAY LINE. An analog delay line with a buffered output. A Delay Line that is compatible with digital logic by buffering the input and output so normal digital logic may interface with the I/O. A delay line that uses a buffer to compensate for the signal lose as it passed through the delay circuit. Related terms; Tapped Delay Line, UnTapped Delay Line.

 

Buffered Delay Line

BUILT-IN TEST EQUIPMENT (BITE). A permanently mounted device that is used expressly for testing an equipment or system. Also refer to System Test Acronyms

BUNCHER CAVITY. The input resonant cavity in a conventional klystron oscillator.

BUNCHER GRID. In a velocity-modulated tube, the grid that concentrates the electrons in the electron beam into bunches.

BURIED VIA. A via hole which does not extend to the surface. A via that only runs between two internal layers. Additional terms related to PWB Definitions and topics.

BURN-IN. The process of screening out marginal component parts by exposing them to elevated temperatures and voltage stress. This test is performed to eliminate marginal devices or those with defects resulting from manufacturing aberrations that are evidenced as time and stress dependent failures. Without the burn-in, these defective devices would be expected to result in early lifetime failures under normal use conditions. It is the intent of this test to operate the semiconductor device at specified conditions to reveal electrical failure modes that are time and stress dependent.

BURNISHING TOOL. A tool used to clean and polish contacts on a relay.

BUS. One or more conductors or optical fibers that serve as a common connection for a group of related devices. More information on Bus Topologies. A line shared by more than one device or component so that information can be passed between devices.

 

Common Bus Topologies

BUS BAR. A heavy copper strap or bar used to connect several circuits together when a large current carrying capacity is required.

BUTTERWORTH FILTER. The type of filter with a particula output response of either an active or passive filter. Refer to the definition of Filter for the different types. The graph shows the different orders of a Butterworth Filter, 1st order filter through a fifth order filter.

Butterworth Filter

BYPASS CAPACITOR. A capacitor used to transfer [Bypass] unwanted signals out of a circuit; for example, coupling an unwanted signal to ground. A capacitor connected across the power and ground pins of an IC. Also called a Decoupling Capacitor.
Definitions only related to Capacitor related Terms.

BYTE. A sequence of adjacent bits (usually considered as a unit [character]. Ten bit bytes are also common, as in 8B/10B. BY-WIRE. A "by-wire" term denotes a control system that replaces traditional mechanical or hydraulic linkages with electronic connections between control units that drive electro-mechanical actuators. Originally used in the aerospace industry as Fly-By-Wire; [Avionic Bus Descriptions], by-wire technology is making its way into the ground transportation sector, as Drive-By-Wire; [Automotive Bus Descriptions]. Automotive by-wire includes three categories: throttle by-wire, steer by-wire, and brake by-wire.

 

CABLE. An assembly of one or more insulated conductors, or optical fibers, or a combination of both, within an enveloping jacket. Either a stranded conductor (single-conductor cable) or a combination of conductors insulated from one another (multiple conductor cable). Small sizes are commonly referred to as stranded wire or as cords.

 

Coax Cable

CABLE ASSEMBLY. A cable that is ready for installation in specific applications and usually terminated with connectors. Manufacturers

CABLE CARRIER. A device that holds a cable. Also refer to a detailed definition of Cable Carrier. In some case it may be called a cable retracter.

Cable Clamp. A mechanical clamp attached to the wire entrance of a connector to support the cable or wire bundle, provide stress relief, and absorb vibration and shock.

Cable, Coaxial. A cable in which an insulated conductor is centered inside another. The outer conductor is usually a metal braid or metal sheath. Braided cables usually have an outer insulating jacket over the braid. Coaxial cables are used primarily for transmission of RF signals. Refer to the main Definition of Coax Cable

CABLE HARNESS. A group of wires or ribbons of wiring used to interconnect electronic systems and subsystems. ALso refer to more detail on Specifying a Cable Harness, part of the equipment chassis design section.

CABLE SHEATH. A conductive protective covering applied to cables. See the diagram for a Coax Cable with armor above.

CACHE. A small portion of memory used as temporary storage, normally having a faster access time than the main memory bank.

CAGE CODE. Commercial and Government Entity Code. A five-position alphanumeric code with a numeric in the first and last positions (e.g. 27340, 2A345, or 2AAA5), assigned to United States and Canadian organizations which manufacture and/or control the design of items supplied to a Government Military or Civil Agency or assigned to United States and foreign organizations, primarily for identifying contractors in the mechanical interchange of data. Read the MIL-STD-100 definition.

CAN BUS. A differential 2-wire interface running over either a Shielded Twisted Pair (STP), Un-shielded Twisted Pair (UTP), or Ribbon cable. A number of different Protocols are used with CAN bus. The CanBus is primarly used as an Automotive Bus, but is also one of the major Field Buses. CanBus

CAPACITANCE. The property of an electrical circuit that opposes changes in voltage. Also refer to the dictionary of Capacitor Terms

CAPACITIVE REACTANCE. The opposition, expressed in ohms, offered to the flow of an alternating current by capacitance. The symbol for capacitive reactance is XC.

 

Disk Capacitor

CAPACITOR. An electrical device capable of storing electrical energy in an electrostatic field. [Capacitor Terms, Capacitor Manufacturers]

CAPACITOR FILTER. This filter is used on extremely high-voltage, low-current power supplies and also where the ripple frequency is not critical. Also see the entry on Passive Filters.

CAPACITOR-START MOTOR. A type of single-phase, ac induction motor in which a starting winding and a capacitor are placed in series to start the motor. The values of XC and R are such that the main-winding and starting-winding currents are nearly 90 degrees apart and the starting torque is produced as in a two-phase motor.

CARBON MICROPHONE. A microphone in which sound waves vary the resistance of a pile of carbon granules. May be single-button or double-button. DYNAMIC MICROPHONE Definition. Microphone Manufacturers

CARDBUS. One of the different types of PCMCIA interfaces. CardBus implements the 32-bit PCI bus standard into the PCMCIA form factor.

CARRIER FREQUENCY. The base frequency of a transmitted electromagnetic pulse or wave on which information can be imposed by varying the signal strength, varying the base frequency, varying the wave phase, or other means. The frequency of an unmodulated transmitter output.

Caster. A wheel mounted in a swivel frame. Caster Manufacturers

CATCHER GRID. In a velocity-modulated tube, a grid on which the spaced electron groups induce a signal. The output of the tube is taken from the catcher grid.

CATEGORY 3. The ANSI/EIA/TIA-568 designation for 100-ohm unshielded twisted-pair cables and associated connecting hardware whose characteristics are specified for data transmission up to 16 Mb/s. [EIA568 Bus Description]

CATHODE. In an electron tube the electrode that is the source of current flow. The general name for any negative electrode. The negative terminal of a forward-biased semiconductor diode, which is the source of the electrons.

CATHODE BIAS. The method of biasing a vacuum tube in which the biasing resistor is placed in the common-cathode return circuit, thereby making the cathode more positive with respect to ground.

CATHODE KEYING. A system in which the cathode circuit is interrupted so that neither grid current nor plate current can flow.

CATHODE MODULATOR. Voltage on the cathode is varied to produce the modulation envelope.

CATHODE-RAY TUBE (CRT). An electron tube that has an electron gun, a deflection system, and a screen. This tube is used to display visual electronic signals. [CRT Graphic]

CATHODE SPUTTERING. A process of producing thin film components.

CAVITY RESONATOR. A space totally enclosed by a metallic conductor and supplied with energy in such a way that it becomes a source of electromagnetic oscillations. The size and shape of the enclosure determine the resonant frequency.

Cavity Up / Cavity Down. The orientation of the package body cavity opening, away from the seating plane for cavity-up or toward the seating plane for cavity-down. See Cavity Orientation Graphic

CAVITY WAVEMETER. An instrument used to measure microwave frequencies.

 

Battery Cell

CELL. A single unit that transforms chemical energy into electrical energy. Batteries are made up of cells. [Battery Manufacturers]

CENTER-FEED METHOD. Connecting the center of an antenna to a transmission line which is then connected to the final (output) stage of the transmitter.

CENTER-TAPPED TRANSFORMER. A Transformer with a tap on the secondary winding mid-way between the winding producing half the available output voltage.

Transformer

CENTIMETER CUBE. A unit of volume of large rectangular or square conductors. The cross-sectional area equals 1 square centimeter with a length of 1 centimeter. Also refer to the Centimeters Squared to Inches Squared Conversion table.

CENTRAL PROCESSING UNIT. [CPU] In Personal Computers {PCs] the microprocessor chip that executes programmed instructions.

CHANNEL. A carrier frequency assignment, usually with a fixed bandwidth.

CHARACTER. A letter, digit, or other symbol that is used as part of the organization, control, or representation of information. [ASCII Code Table]

CHARACTERISTIC IMPEDANCE. [Zo] The ratio of voltage to current at any given point on a transmission line represented by a value of impedance. A measure of the electromagnetic coupling between the signal conductor and its return path. The impedance of a circuit that, when connected to the output terminals of a uniform transmission line of arbitrary length, causes the line to appear infinitely long. A uniform line terminated in its characteristic impedance will have no standing waves, no reflections from the end, and a constant ratio of voltage to current at a given frequency at every point on the line.

CHARGE. Represents electrical energy. A material having an excess of electrons is said to have a negative charge. A material having a shortage of electrons is said to have a positive charge.

CHARGE CYCLE. The period of time that a capacitor in an electrical circuit is storing a charge.

CHASSIS. An equipment case. An equipment enclosure used to hold circuit boards or other components. Also refer to Styles of Equipment Enclosures.

CHASSIS GROUND. The potential of an equipment chassis. The attached graphic shows how to connect a printed wire board [PWB] ground to chassis ground. Additional information may be found on Grounding in Chassis Design.

Circuit Ground with Chassis Ground

Chatter, Contact. The undesired opening of mating contacts resulting from uncompensated AC operation, or external shock and vibration [Relay]. Relay Manufacturers

CHECK BIT. A bit, such as a parity bit, derived from and appended to a bit string for later use in error detection and possibly error correction.

CHECK-SUM. A number that has been calculated as a function of some message, by adding up the bytes in the message. The [message] data is summed with out regard overflow. Perhaps this was what early checksums were. Today, however, although more sophisticated formulae are used, the term "checksum" is still used and interchangeable with the term CRC.

CHIP INDUCTOR. A surface mount inductor. Refer to MIL-PRF-83446; Coils, Chip, Fixed or Variable, General Specification. Inductor Manufacturers

Chip Inductor

Chip Carrier. A low-profile four-sided (rectangular) part package, whose semiconductor chip cavity or mounting area is a large fraction of the package size.

CHOKE. An inductor used to impede the flow of pulsating dc or ac by means of self-inductance. A choke is designed to have a high reactance to a particular frequency. Common-mode chokes are used to protect from EMI. High frequency chokes may be called ferrite chokes or choke baluns. RF chokes normally have air core, while low frequency chokes have ferromagnetic iron cores. [Choke Manufacturers]

Choke

CHOKE JOINT. A joint between two sections of waveguide that provides a good electrical connection without power losses or reflections.

Circuit. The complete path of an electric current. A group of electrical components connected together to perform some function.

Circuit Breaker.

Circuit Breaker

A device designed to open and close a circuit by non-automatic means and to open the circuit automatically on a predetermined over-current without injury to itself when properly applied within its rating. Manufacturers of Circuit Breakers.

Circular DIN. A type of connector. Definition of Circular DIN Connector.

Circular MIL. An area equal to that of a circle with a diameter of 0.001 inch. It is used for measuring the cross-sectional area of wires.

Circular MIL-FOOT. A unit of volume of a conductor having a cross-sectional area of 1 circular mil and a length of 1 foot.

Cladding. The dielectric material surrounding the core of an optical fiber.

Clamper. A circuit in which either the upper or lower extremity of a waveform is fixed at a desired value.

Clam Shell. A hinged style of connector backshell, strain relief or safety shield. This particular plastic clam shell strain relief is being used with the Molex style of power connector. Metal clam shells are also possible. Other styles of Connector Back-Shells.

CLASS A Amplifier Operation. The type of operation in which the amplifier is biased so that variations in input signal polarities occur within the limits of cutoff and saturation.

CLASS AB Amplifier Operation. The type of operation in which the amplifier is biased so that collector current is cut off for a portion of the alternation of the input signal.

CLASS B Amplifier Operation. The type of operation in which the amplifier is biased so that collector current is cut off for one-half of the input signal.

CLASS C Amplifier Operation. The type of operation in which the amplifier is biased so that collector current is cut off for more than one-half of the input signal.

Clock. A device that generates periodic, accurately spaced signals used for timing applications. Related; Manufacturers of Integrated Circuit Timers, Manufacturers of Integrated Circuit Real Time Clocks

COAXIAL CABLE. Cable in which the center conductor is separated from an outer conductor by a dielectric material; used in RF transmission. A longer description may be found in the Radar section; Coaxial Cable Definition. Manufacturers of Coax, Twinax, Triax Cable

Coax Cable

COAXIAL LINE. A type of transmission line that contains two concentric conductors.

CODE. Code is a combination of mark and space conditions representing symbols, figures, or letters.

CODEC: Acronym for coder-decoder. An assembly consisting of an encoder and a decoder in one piece of equipment. A circuit that converts analog signals to digital code and vice versa. An electronic device that converts analog signals, such as video and voice signals, into digital form and compresses them to conserve bandwidth on a transmission path. Note: Codecs in this sense are used in this sense for video conferencing systems. Manufacturers of CODEC ICs.

CODER-DECODER: See Codec.

COEFFICIENT OF COUPLING. An expression of the extent to which two inductors are coupled by magnetic lines of force. This is expressed as a decimal or percentage of maximum possible coupling and represented by the letter K.

COHERENCE. A definite phase relationship between two energy waves, such as transmitted frequency and reference frequency.

COHERENT. Radiation on one frequency.

COHERENT OSCILLATOR. An oscillator that supplies phase references. Radar Dictionary

Coil. An inductive device made by looping turns of wire around a core. The picture shows two different through-hole style inductors. Surface Mount Coils are also possible. Also refer to Coil manufacturers and vendors.

Through-Hole Coils

COLD-CATHODE TUBE. A gas-filled electron tube that conducts without the use of filaments. Cold-cathode tubes are used as voltage regulators.

COLLECTOR. The element in a transistor that collects the current carriers. [Transistor Definitions, Manufacturers of Transistors]

COLLECTOR-INJECTION MODULATOR. The transistor equivalent of a plate modulator. Modulating voltage is applied to a collector circuit.

COLLINEAR ARRAY. An array with all the elements in a straight line. Maximum radiation is perpendicular to the axis of the elements.

COMB Filter. An N-Path filter response which contains a sequence of equally spaced passbands forming a comb.

COMBINATIONAL LOGIC. A logic subsystem with no memory.

COMBINATION ARRAY. An array system that uses the characteristics of more than one array.

COMBINATION CIRCUIT. A series-parallel circuit. [Antenna Terms]

COMBINATION PEAKING. A technique in which a combination of peaking coils in series and parallel (shunt) with the output signal path is used to improve high-frequency response.

COMBINATORIAL LOGIC. A logic subsystem that contains no memory who's output is a function of the present input.

COMMERCIAL-OFF-THE-SHELF. [COTS] item is defined as any item that can be purchased and does not need to be designed. [Detailed Definition of COTS]

COMMON BASE. The Base element is common to both the input and output circuit, normally grounded. See Transistor Terms.

COMMON-BASE DETECTOR. An amplifying detector in which detection occurs in the emitter-base junction and amplification occurs at the output of the collector junction.

COMMON CARRIER. In the telecommunications area, the term used to describe a telephone company.

COMMON COLLECTOR. A transistor circuit which has the collector of the transistor grounded or common between the input and output of the transistor circuit. See Transistor Terms.

COMMON EMITTER. See Transistor Terms. [Common Emitter BJT Schematics]

COMMON-EMITTER DETECTOR. Often used in receivers to supply detected and amplified output. The emitter-base junction acts as the detector.

COMMON IDENTITIES LAW. In Boolean algebra this law states that anytime the expression A(A + B) = AB or A + AB = A + B appears, it can immediately be simplified to AB without going through the process of using the distributive law, complementary law, or the law of union to simplify.

COMMUTATION. The act of a commutator in converting generator output from an ac voltage to a dc voltage.

COMMUTATIVE LAW. In Boolean algebra this law states that changing the order of the terms in an equation will not affect the value of the equation. Example: A + B = B + A; A • B = B • A.

COMMUTATOR. A mechanical device that reverses armature connections in motors and generators at the proper instant so that current continues to flow in only one direction. In effect, the commutator changes ac to dc. Motor Vendors

Motor Commutator

CompactPCI. Compact Peripheral Component Interface. An industrial version of the PCI standard [Peripheral Component Interface]. CompactPCI uses the Euro board format/size, but uses the same electrical standard as the consumer PCI interface bus. CompactPCI Bus.

COMPANDER. An acronym for COMpressor-exPANDER. A circuit that compresses and then expands the signal in amplitude.

COMPENSATING WINDINGS. Windings embedded in slots in pole pieces, connected in series with the armature, whose magnetic field opposes the armature field and cancels armature reaction.

COMPENSATION. The process of overcoming the problems associated with high frequencies in an amplifier.

COMPLEMENT. A number or state that is the opposite of a specified number or state. The negative of a number is often represented by its complement.

COMPLEMENTARY (SECONDARY) COLORS OF LIGHT. The colors of light produced when two of the primaries are mixed in overlapping beams of light. The complementary colors of light are magenta, yellow, and cyan.

COMPLEMENTARY LAW. In Boolean algebra this law states that the logical addition of a quantity and its complement will result in 1 and the logical multiplication of a quantity and its complement will result in a product of 0.

COMPLEMENTARY Metal Oxide Semiconductor. [CMOS] A type of Integrated Circuit structure. Also see Standard CMOS Logic IC Vendors.

COMPLEMENT NUMBER. A number that when added to another number gives a sum equal to the base of the number system of operation. For example, in the decimal number system, the complement of 1 is 9.

COMPLEX WAVE. A waveform other than a sine wave. A wave that is produced by combining two or more pure tones at the same time.

COMPLIANT PIN. A pin used with a Printed Circuit Board [PCB] as an interconnect. The pin is press-fit and solder-free. In most cases the pin[s] are the board mount side of a connector. Read more on Compliant Pins.

COMPOUND-WOUND MOTORS AND GENERATORS. Machines that have a series field in addition to a shunt field. Such machines have characteristics of both series- and shunt-wound machines. [Manufacturers of Motors]

COMPRESSION WAVES. Longitudinal waves that have been compressed (made more dense) as they move away from the source.

COMPUTER. A data processing unit that can perform computation, including numerous arithmetic or logic operations, without intervention by a human. Computer Manufacturers

CONCURRENT. Pertaining to the occurrence of two or more events or activities within the same specified interval of time.

CONDUCTANCE. The ability of a material to conduct or carry an electric current. It is the reciprocal of the resistance of the material and is expressed in mhos or siemens.

Conduction. The transfer of heat in a substance from a higher temperature to a lower temperature. Heat Conduction is the most effective method of moving heat from the junction to the case and the case to a heat-sink [if installed] in semiconductors.

Conduction Band. A partially filled energy band in which electrons can move freely.

CONFORMAL COATING. An insulative coating that conforms to the configuration of the object being coated. [Coating Supplies]

CONDUCTIVITY. The ease with which a substance transmits electricity.

CONDUCTOR. A material with a large number of free electrons. A material that easily permits electric current to flow. Any wire, cable, or substance capable of carrying an electrical current. Wire Manufacturers

CONDUIT. A tubular raceway, usually metal or plastic, for holding wires or cables. Also refer to MIL-PRF-24758. All conduit, whether used for power distribution wiring, or for signal and control wiring, shall be grounded.

CONICAL SCANNING. Scanning in which the movement of the beam describes a cone, the axis of which coincides with that of the reflector.

CONNECTED ARRAY. Another term for Driven Array.

Connector Adaptor. See Adaptor

Constant Current Source. A current source is considered constant if halving the generator impedance does not produce a change in the parameter being measured that is greater than the required precision of the measurement. A source of current that remains constant.

Constant Voltage Source. A voltage source shall be considered constant if doubling the generator impedance does not produce a change in the parameter being measured that is greater than the required precision of the measurement.

CONTACT ARRANGEMENT. Also called Insert Arrangements. The number, spacing and location of the contacts of a connector. For reference see the MIL-32139 diagram.

CONTACT BOUNCE. The uncontrolled making or breaking of a contact, normally in a switch or relay when the position is changed. Sometimes called Contact Chatter. Also refer to Switch Debounce

Bounce

CONTACT STYLES. The different types of Contact Styles found on connectors; Crimp, Solder, Printed Circuit Solder, Printed Circuit Press Fit, Thermocouple, Wire Wrap, Co-Ax, Insulation Displacement, Pre-Terminated, Fiber Optic, High Voltage, First-Make Last-Break. Related topic, Manufacturers of Connectors

Contaminant. An impurity or foreign substance present in a material that affects one or more properties of the material. CONTENTION. A condition that occurs when more than one device on a bus tries to access the bus at the same time. A condition when two or more devices require access to a shared resource at the same time.

CONTIGUOUS. Two items place one after another, next to each other. Adjacent.

CONTINUITY. An uninterrupted, complete path for current flow. Continuity Testers, or the general page for Test Equipment Manufacturers.

CONTINUOUS-WAVE KEYING. The on-off keying of a carrier.

CONTRAST RATIO. The ratio of two luminances.

CONTROL DIFFERENTIAL TRANSMITTER (CDX). A type of synchro that transmits angular information equal to the algebraic sum or difference of the electrical input supplied to its stator, the mechanical input supplied to its stator, and the mechanical input supplied to its rotor. The output is an electrical voltage taken from the rotor windings.

CONTROL FIELD. In a protocol data unit (PDU), the field that (a) contains data interpreted by the receiving destination logical-link controller (LLC) and (b) may be the field immediately following the destination service access point (DSAP) and source service access point (SSAP) address fields of the PDU. [Protocol Terms]

CONTROL GRID. The electrode of a vacuum tube, other than a diode, upon which a signal voltage is impressed to regulate the plate current. Also refer to the Definition of Vacuum Tube

CONTROL-GRID MODULATOR. Uses a variation of grid bias to vary the instantaneous plate voltage and current. The modulating signal is applied to the control grid.

CONTROL SYNCHRO SYSTEMS. Synchro systems that contain control synchros and are used to control large amounts of power with a high degree of accuracy. The electrical outputs of these systems control servosystems, which in turn generate the required power to move heavy loads. Also refer to the Definition of Synchro

CONTROL SYSTEM. A group of components systematically organized to perform a specific control purpose. These systems are categorized as either closed- or open-loop systems. The main difference between the two is that the closed-loop system contains some form of feedback.

CONTROL TRANSFORMER (CT). A type of synchro that compares two signals: the electrical signal applied to its stator and the mechanical signal applied to its rotor. The output is an electrical voltage, which is taken from the rotor winding and is used to control a power-amplifying device. The phase and amplitude of the output voltage depends on the angular position of the rotor with respect to the magnetic field of the stator.

CONTROL TRANSMITTER (CX). A type of synchro that converts a mechanical input, which is the angular position of its rotor, into an electrical output signal. The output is taken from the stator windings and is used to drive either a CDX or CT.

Convection. The transfer of heat through air or liquids. Heat convection is the method of heat transfer from the body of an IC, case of a semiconductor, or heat sink to the surrounding air. CONVERTER. In Digital electronics a circuit or IC that converts an Analog signal into a digital signal [ADC], or converts a digital signal into an Analog signal [DAC]; Manufacturers of IC Converters.
In DC power electronics, a DC to DC converter circuit which converts a source of direct current (DC) from one voltage level to another [DC Regulator manufacturers].
In communications, equipment that changes the audio output of a receiver to dc pulses. These pulses are fed to a tty to indicate marks and spaces [Obsolete definition].

COOKIE-CUTTER TUNER. A mechanical magnetron tuning device that changes the frequency by changing the capacitance of the anode cavities.

Copper Loss (I2R Loss). The power lost because of the resistance of the conductors. In transformers the power lost because of current flow (I) through the resistance (R) of the windings.

Cord, Electrical. Two or more insulated conductors contained within a common covering, or twisted together without a common covering.

Core. Any material that affords a path for magnetic flux lines in a coil. Transformer Core Manufacturers

CORONA. The discharge of electricity from a conductor with a high potential.

CORRESPONDENCE. The term given to the positions of the rotors of a synchro transmitter and a synchro receiver when both rotors are on 0 degree or displaced from 0 degree by the same angle. See synchro.

COTS. Commercial off-the-shelf equipment that can be purchased through commercial retail or wholesale distributors as is (i.e., equipment that is available as a cataloged item) or with only minor modifications that does not alter its form, fit or functional characteristics. Detailed Definition of COTS.

COULOMB. A measure of the quantity of electricity. One coulomb is equal to 6.28 x 1018 electrons.

COULOMB'S LAW. Also called the LAW OF ELECTRIC CHARGES or the LAW OF ELECTROSTATIC ATTRACTION. Coulomb’s Law states that charged bodies attract or repel each other with a force that is directly proportional to the product of their individual charges and inversely proportional to the square of the distance between them.

COUNTER. A device that counts input pulses. An IC or circuit that counts clock pulses [74190, 74191 Logic Gates]. A piece of test equipment that counts incoming pulses, as in a Frequency Counter.

COUNTER EMF. The voltage generated within a coil by a moving magnetic field cutting across the coil itself. This voltage is in opposition (counter) to the moving field that created it. Counter emf is present in every motor, generator, transformer, or other inductance winding whenever an alternating current flows.

COUNTERPOISE. A network of wire connected to a quarter-wave antenna at one end. The network provides the equivalent of an additional one-fourth wavelength.

COUPLING. The process of transferring energy from one point in a circuit to another point, or from one circuit to another.

COUPLING CAPACITOR. A capacitor used to couple signals. Also refer to the section on Capacitor Terms. Reference Capacitor Manufacturers

COUPLING DEVICE. A coupling coil that connects the transmitter to the feeder.

COVALENT BOND. A type of linkage between atoms in which the atoms share valence electrons.

CRASH. The breakdown in a hardware system [ie Disk Crash] or software system [ie OS Crash, Blue screen].

CRC - This stands for "Cyclic Redundancy Code". The term "CRC" seems to be reserved for algorithms that are based on the "polynomial" division. The essential mathematical operation in the calculation of a CRC is binary division, and the remainder from the division determines the CRC. CRC's cannot, however, be safely relied upon to verify data integrity. CRC types are often identified by the polynomial, which is the number used as the divisor. A number of pages on this site make reference to the CRC used for different electronic Interface Buses.

CREST (TOP). The peak of the positive alternation (maximum value above the line) of a wave.

Crimp. The physical compression (deformation) of a contact barrel around a conductor to make an electrical and mechanical connection to the conductor [Wire Crimp shown right]. Crimp contacts are assembled to conductors outside of the connector and are subsequently installed into the connector body. When a connector is properly assembled, contacts are captured inside the connector. Retaining clips are one means of securing contacts in place inside connector cavities. When retaining clips are present, contacts shall be fully seated and locked into place by the clip. Improperly seated contacts can "push back" causing intermittent and open circuits. In all instances, non-metal contact insertion and removal tools shall be used to prevent damage to connectors, contacts, or conductors.

CRITICAL ANGLE. The maximum angle at which radio waves can be transmitted and still be refracted back to earth.

CRITICAL FREQUENCY. The maximum frequency at which a radio wave can be transmitted vertically and still be refracted back to earth.

CROSSBAR SWITCH. A number of switches formed into a matrix so that may interconnect with another allowing any input line to connect to any output line..

CROSSED-FIELD AMPLIFIER. A high-power electron tube that converts dc to microwave power by a combination of crossed electric and magnetic fields.

CROSSED-OVER ADAPTER. A networking module that internally swaps the Transmit and Receive wires. CROSSED-OVER CABLE. A networking cable that internally swaps the Tx and Rx wires, allowing direct connection between devices.

Crossover Adapter

CROSS-SECTIONAL AREA. The area of a "slice" of an object. When applied to electrical conductors it is usually expressed in circular mils.

CROSS-TALK. The unintended or undesired capacitive, inductive, or conductive coupling from one circuit, or channel to another. Unwanted sound in a voice channel cross-coupled from another voice channel.

CROWBAR. A method of shorting out a power supply when an over-voltage occurs to protect the electronics being supplied. A term used to indicate that something is being shorted as in placing a crowbar between the terminals. A circuit form by an over-voltage sense circuit and an SCR. The gate of the SCR connects to the sense circuit while the anode and cathode are connected to the supply rails.

 

SCR Crowbar Circuit

CRT. Cathode Ray Tube [Dictionary of Radar Terms].

CRYSTAL. A natural substance, such as quartz or tourmaline, that is capable of producing a voltage when under physical stress or of producing physical movement when a voltage is applied. XTAL Manufacturers

CRYSTAL FURNACE. A device for artificially growing cylindrical crystals to be used in the production of semiconductor substrates.

CRYSTAL MICROPHONE. A microphone that uses the piezoelectric effect of crystalline matter to generate a voltage from sound waves. [Microphone Manufacturers]

CRYSTAL OVEN. A closed oven maintained at a constant temperature in which a crystal and its holder are enclosed to reduce frequency drift. Companies making Temperature Controlled Oscillators.

CURRENT. The movement of electrons past a reference point. The passage of electrons through a conductor. Measured in amperes.

CURRENT RATING. The safe current-carrying capacity of a wire or cable on a continuous basis. See AWG [wire gauge].

CURRENT REGULATOR. A circuit that provides a constant current output. Refer to Constant Current Source

CURRENT STANDING-WAVE RATIO (ISWR). The ratio of maximum to minimum current along a transmission line.

CUTOFF. The condition in a tube or transistor whereby the reverse bias prevents current flow.

CUTOFF FREQUENCY. The 3dB point of a filter at which point the filter starts to attenuate the signal. The frequency at which the attenuation of a waveguide increases sharply and below which a traveling wave in a given mode cannot be maintained. A frequency with a half wavelength that is greater than the wide dimension of a waveguide.

CW DEMODULATOR. A circuit that detects the presence of RF oscillations and converts them into a useful form.

CYCLE. One complete positive and one complete negative alternation of a current or voltage. A 360-degree rotation of a vector generating a sine wave. A cycle is measured in Hertz, Hz.

Cycle

Cyclic Redundancy Code. See CRC.

D Flip Flop. A style of flip flop who's output follows the input when the device is clocked. The Truth Table for a D-Type flip flop is shown to the right. The output changes on the edge of the clock. The most common IC is the 7474; Dual Positive-Edge-Triggered D-Type Flip-Flops with Set and Reset. IC Vendors.

Truth Table

74374 Functional Block Diagram

DAMPED WAVE. A sinusoidal wave in which the amplitude steadily decreases with time. Often associated with energy loss.

DAMPING. The process of smoothing out oscillations. The progressive decay with time in the amplitude of the free oscillations in a circuit. The progressive diminution with time of certain quantities characteristic of a phenomenon. In a meter, this process is used to keep the pointer of the meter from over-shooting the correct reading. A mechanical or electrical technique used in synchro receivers to prevent the rotor from oscillating or spinning. Damping is also used in servosystems to minimize overshoot of the load.

 

Damping

D'ARSONVAL METER MOVEMENT. The permanent-magnet moving-coil movement used in most analog meters. Note that most meters use digital displays.

DATA ENCRYPTION STANDARD {DES}. A cryptographic algorithm for the protection of unclassified computer data and published by the National Institute of Standards and Technology in Federal Information Processing Standard Publication 46-1.

DATA PROCESSING. The execution of a systematic sequence of operations performed upon data. Synonymous with information processing.

DATA TRANSFER RATE. The average number of bits, characters, or blocks per unit time passing between corresponding equipment in a data transmission system.

DATA TRANSMISSION. The transfer of information from one place to another or from one part of a system to another. The sending of data from one place to another by means of signals over a channel.

Datum. A datum is the origin from which the location or geometric characteristics of features of a part are established.

dB. An abbreviation for decibel(s). One tenth of the common logarithm of the ratio of relative powers, equal to 0.1 B (bel). Note 1: The decibel is the conventional relative power ratio, rather than the bel, for expressing relative powers because the decibel is smaller and therefore more convenient than the bel.

dBa. An abbreviation for decibels adjusted. Weighted absolute noise power, calculated in dB referenced to 3.16 picowatts (–85 dBm), which is 0 dBa.

dBm. An abbreviation used to represent power levels above or below a 1-milliwatt reference.

DCE. An abbreviation for data circuit-terminating equipment. In a data station, the equipment that performs functions, such as signal conversion and coding, at the network end of the line between the data terminal equipment (DTE) and the line, and that may be a separate or an integral part of the DTE or of intermediate equipment. The interfacing equipment that may be required to couple the data terminal equipment (DTE) into a transmission circuit or channel and from a transmission circuit or channel into the DTE.

Dead Short. A short circuit having minimum resistance. A direct connection between two points.

Debounce. A circuit which reduces the signalling from a switches spring-back or vibration. Refer to the Switch Debounce definition.

Debug. To examine, test, locate and isolate a circuit fault. Related; Device Under Test

DECIMAL. Pertaining to the number representation system with a radix of ten. Refer here for more definitions relating to the term Decimal.

DECOUPLING CAPACITOR. A capacitor used to transfer unwanted signals out of a circuit; for example, coupling an unwanted signal to ground. Also called a Bypass Capacitor. [Capacitor Terms]. A capacitor that De-Couples an IC from its supply voltage by supplying a voltage charge when required reducing the time lag from a distant power supply [IC Decoupling].

DEEMPHASIS. In FM transmission, the process of restoring (after detection) the amplitude-vs.frequency characteristics of the signal.

Deenergized. Free from any electrical connection to a source of potential difference and from electric charge; not having a potential different from that of the earth. Note: The term is used only with reference to current-carrying parts, which are sometimes energized (alive).

DEFLECTION COILS. In a cathode-ray tube, coils used to bend an electron beam a desired amount. Also refer to the CRT Definition.

DEFLECTION PLATES. Two pairs of parallel electrodes, one pair set forward of the other and at right angles to each other, parallel to the axis of the electron stream within an electrostatic cathode-ray tube.

DEGENERATION. The process whereby a part of the output signal of an amplifying device is returned to its input circuit in such a manner that it tends to cancel part of the input.

DEGENERATIVE FEEDBACK. Feedback in which the feedback signal is out of phase with the input signal; also called NEGATIVE FEEDBACK.

DEGREE-OF-FREEDOM. The number of axes about which a gyro is free to precess.

DEIONIZATION POTENTIAL. The potential at which ionization of the gas within a gas-filled tube ceases and conduction stops; also referred to as extinction potential.

DEIONIZATION TIME. In a spark gap, the time required for ionized gas to return to its neutral state after the spark is removed.

DELAY EQUALIZER. A device that adds delay to only certain frequencies in a circuit to reduce delay distortion.

DELAY LINE. A transmission line, or equivalent passive component, used to delay a signal. A component or device either active or passive used to delay a signal. Related term, Programmable Delay Line. IC Delay Line Manufacturers [active or passive components].

 

Tapped Delay Line

DELAY RELAY. See Time Delay Relay.

DELAYED SWEEP. In an oscilloscope when a horizontal sweep is delayed by some amount of time after a trigger is received. Related term CRT Definition.

DELIMITER. A character used to indicate the beginning and end of a character string, i.e., a symbol stream, such as words, groups of words, or frames. A flag that separates and organizes items of data.

DELTA. A three-phase connection in which windings are connected end-to-end, forming a closed loop that resembles the Greek letter delta. A separate phase wire is then connected to each of the three junctions.

DEMODULATION. The removal of intelligence from a transmission medium. The recovery, from a modulated carrier, of a signal having substantially the same characteristics as the original modulating signal.

DEMODULATOR. A circuit used in servo-systems to convert an ac signal to a dc signal. The magnitude of the dc output is determined by the magnitude of the ac input signal, and its polarity is determined by whether the ac input signal is in or out of phase with the ac reference voltage.

DeMORGAN'S THEOREM. A theorem which states that the inversion of a series of AND applications is equal to the same series of inverted OR applications, or the inversion of a series of OR applications is equal to the same series of inverted AND applications. Also refer to Timing Hazards for applications

DENSITY. The compactness of a substance. Mass per unit volume.

DEPLETION REGION. The region in a semiconductor where essentially all free electrons and holes have been swept out by the electrostatic field which exists there.

DERATING. The process of reducing a components power dissipation with increasing temperature to insure that the component remains at the same temperature. Derating applies to any device that allows current flow, Active, Passive or Mechanical. Guideline for Derating Electronic Components. The method of reducing stress and/or making quantitative allowances for a part’s functional degradation. Consequently, derating is a means to reduce failures and extending part life. In addition, derating helps protect parts from unforeseen application anomalies and over-stresses.

DETECTION. The separation of low-frequency (audio) intelligence from the high-frequency carrier.

DETECTOR. A mixer or converter in a superheterodyne receiver. A simple diode circuit used to detect the presents of a signal. [RF Phase Detector Manufacturers].

DEVICE UNDER TEST. A component or device under going testing. [Example DUT Circuit]

DIBIT: A group of two bits. Note: The four possible states for a dibit are 00, 01, 10, and 11.

DIE BONDING. Process of mounting a chip to a package. Also reference the page covering PCB Terms and Definitions

DIELECTRIC. An insulating (nonconducting) medium. A substance in which an electric field may be maintained with zero or near-zero power dissipation, i.e., the electrical conductivity is zero or near zero. An insulator; a term applied to the insulating material between the plates of a capacitor.

DIELECTRIC CONSTANT. The ratio of a given dielectric to the dielectric value of air. The property of an insulation which determines the electrostatic energy stored per unit volume for unit potential gradient.

DIELECTRIC BREAKDOWN. The rupture of an insulating material when the electric stress exceeds the dielectric strength.

DIELECTRIC FIELD. The space between and around charged bodies in which their influence is felt. Also called ELECTRIC FIELD OF FORCE or an ELECTROSTATIC FIELD.

DIELECTRIC HEATING. The heating of an insulating material by a high-frequency electric field.

DIELECTRIC HYSTERESIS LOSS. Power loss of a capacitor because of the changes in orientation of electron orbits in the dielectric; the changes in orientation are caused by rapid reversal in polarity of line voltage. The higher the frequency, the greater the loss.

DIELECTRIC LEAKAGE. Power loss of a capacitor because of the leakage of current through the dielectric. Also relates to leakage resistance; the higher the leakage resistance, the lower the dielectric leakage.

DIELECTRIC LOSSES. The losses resulting from the heating effect on the dielectric material between conductors.

DIELECTRIC STRENGTH. The ability of an insulator to withstand a potential difference without breaking down (usually expressed in terms of voltage). The maximum potential gradient that a material can withstand without rupture. As a material property it usually is calculated by dividing the breakdown voltage by the thickness of the material between a pair of test electrodes.

DIFFERENCE FREQUENCY. Beat Frequency. The difference between the oscillator frequency and the unknown audio frequency.

DIFFERENCE OF POTENTIAL. A voltage between two points.

DIFFERENTIAL AMPLIFIER. A circuit that amplifies the difference between two input signals.

 

Op Amp Differential Circuit

Differential Pair. A pair of conductors with one line carrying the true version and the other line carrying the inverted version of the signal. Differential Pair Layout Guidelines.

Differential Interface. See Differential Pair.

Differential Transceiver. A buffer or amplifier that transmits and receives differential signals.

Differential Transceiver

 

DIFFERENTIATING AMPLIFIER. A circuit that performs the derivative of an input signal. An Operational Amplifier [Op-Amp] is shown in the graphic.

Op Amp Differentiating Circuit

DIFFRACTION. The bending of waves (as light or RF) when the waves are met with some form of obstruction.

DIFFUSION. The scattering of reflected light waves from an object, such as white paper. Controlled application of impurity atoms to a semiconductor substrate.

DIGIT. A symbol that represents one of the nonnegative integers smaller than the radix. For example, in decimal notation a digit is one of the characters from 0 through 9.

DIGITAL SUBSCRIBER LINE (DSL). In Integrated Services Digital Networks (ISDN), equipment that provides full-duplex service on a single twisted metallic pair at a rate sufficient to support ISDN basic access and additional framing, timing recovery, and operational functions.

DIGITIZE. Conversion of an analog signal into a digital signal carrying equivalent information.

 

Diode Schematic Symbols

DIODE. A two element, solid-state device made of either germanium or silicon; it is primarily used as a switching device. [Diode Manufacturers]. An electron tube containing two electrodes: a cathode and a plate. Description of different Diode Types and definitions.

DIODE DETECTOR. A demodulator that uses one or more diodes to provide a rectified output with an average value that is proportional to the original modulation.

Diode ORing. Diode ORing is normally used when two different power supplies are connected in parallel and separated by diodes so that if one supply fails the other begins to supply power to the circuit. The diodes stop one supply from feeding current into the other supply while still allowing current from either supply to feed the circuits being powered. Each leg of a diode is tied to a supply while the other sides of the diodes are connected together and to the load. The return path also have separate diodes in each leg of a return path and with the ends of other side connected together and to the return side of the load.

DIODE TRANSISTOR LOGIC. [DTL] A style of digital logic that used both diodes and transistors to perform the logic function. Diode Transistor Logic was used up to the early to mid seventies when it was replaced by TTL logic. Diode Transistor Logic is obsolete and should not be used in new designs, it's doubtful any DTL devices could be procured in any event.

Diode Transistor Logic

 

DIP IC. Dual Inline Package IC. A style of Integrated Circuit that has its pins on either side of a rectangular shaped package. Normally a DIP IC refers to a through-hole component, while a surface mound device would be called an SOIC [for example].

DIP ICs

DIPOLE. A common type of half-wave antenna made from a straight piece of wire cut in half. Each half operates at a quarter wavelength of the output. [Antenna Terms.]

DIRECT CURRENT. [DC] An electric current that flows in one direction only.

DIRECTIONAL COUPLER. A device that samples the energy traveling in a waveguide in one direction only.

DIRECTIVITY. The ability of an antenna to radiate or receive more energy in some directions than in others. The degree of sharpness of the antenna beam.

DIRECTLY HEATED CATHODE. A wire, or filament, designed to emit the electrons that flow from cathode to plate. The filament is designed so that a current is passed through it; the current heats the filament to the point where electrons are emitted.

DIRECTOR. The parasitic element of an array that reinforces energy coming from the driver element.

DIRECT MEMORY ACCESS. [DMA] a means of data transfer directly between a peripheral and the system memory without passing through the CPU. A transfer of multiple bytes of data in a system, but supervisory over-head only occurs on the first byte or the start of the transfer [all other bytes are transferred directly with system control] as in a Block Transfer.

DIRECT SHORT. Same as Short Circuit.

DISCIPLINED OSCILLATOR. [DO] An oscillator whose output frequency is continuously steered [often via a phase locked loop] to agree with an external reference.

DISCRETE COMPONENTS. Individual transistors, diodes, resistors, capacitors, and inductors.

DISCRIMINATOR. A circuit in which amplitude variations are derived in response to phase or frequency variations. The part of an FM receiver that extracts the desired signal from an incoming FM wave by changing frequency variations into amplitude variations.

DISH. A microwave antenna shaped like a dish. For more detail refer to the Antenna Dictionary.

DISKETTE. The same as a Floppy Disk, or just Floppy. A removable disk cartridge. The Diskette is out-dated and obsolete.

DISPERSION. The refraction of light waves that causes the different frequencies to bend at slightly different angles.

DISPLACEMENT CURRENT. The current that appears to flow through a capacitor.

DISTILLED WATER. Water that has been purified through a process of evaporation and condensation.

DISTORTION. Any unwanted change between an input signal and output signal. An undesired change between a transmitted signal and the received signal. Read more on Distortion.

DISTRIBUTED CONSTANTS. The constants of inductance, capacitance, and resistance in a transmission line. They are spread along the entire length of the line and cannot be distinguished separately.

DISTRIBUTIVE LAW. In Boolean algebra the law which states that if a group of terms connected by like operators contains the same variable, the variable may be removed from the terms and associated with them by the appropriate sign of operation (for example, A(B + C) = AB + AC).

DOMAIN NAME SERVER. A server that retains the addresses and routing information for TCP/IP LAN users.

DOMAIN THEORY. A theory of magnetism based upon the electron-spin principle. Spinning electrons have a magnetic field. If more electrons spin in one direction than another, the atom is magnetized.

DOMINANT MODE. The easiest mode to produce in a waveguide, and the most efficient mode in terms of energy transfer.

DONOR. An impurity that can make a semiconductor material an N-type by donating extra "free" electrons to the conduction band.

DON'T CARE. The variable may take any logic state without effecting circuit operation, logical operation.

DOORKNOB TUBE. An electron tube that is similar to the acorn tube but larger. The doorknob tube is designed to operate, at high power, in the uhf frequencies.

DOPING. The process of adding impurities to semiconductor crystals to increase the number of free charges that can be moved by an external, applied voltage. Doping produces N-type or P-type material.

DOPPLER EFFECT. The apparent change in frequency or pitch when a sound source moves either toward or away from a listener.

DOPPLER FREQUENCY. The difference between transmitted and reflected frequencies; caused by the Doppler effect.

DOPPLER SHIFT. The apparent change of frequency caused by the motion of the frequency source (transmitter) relative to the destination (receiver). Refer to Doppler Frequency Shift.

DOS. [Disk Operating System]. A text oriented program that operates between the computer and the user.

DOUBLE-MODING. In a transmitter output tube, the abrupt and random change from one frequency to another.

DOUBLE NEGATIVE LAW. In Boolean algebra, the law which states that the complement of a complement is the equivalent of the original term.

DOUBLE RECEIVER. A fine and coarse synchro receiver enclosed in a common housing with a two-shaft output (one shaft inside the other).

DOUBLET. Another name for the dipole antenna. Also refer to a separate dictionary of Antenna Terms.

DOUBLING UP. This is a type of two-equipment installation where one unit can be substituted for another in the event of failure. Also Hot-Swap.

DOWN LINK. The frequency used to transmit an amplified signal from a satellite or other craft back to earth.

DRAIN WIRE. An uninsulated wire in contact with a cable shield throughout its length, used for terminating the shield. A Drain Wire may form part of a cable bundle or cable assembly. A wire that runs linearly along a foil shield wire or cable and is used to make contact with the shield. Grounding of foil shields is done with drain wires.

DRAM. A type of RAM that maintains its content as long as the data stored in the device is refreshed at regular intervals. DRAM requires a refresh cycle every few milliseconds in order to retain its data. The data is stored in a capacitor which slowly leaks, the refresh cycle re-charges the capacitor. DRAM is cheaper and slower than SRAM because of the longer access times. [DRAM Manufacturers]

DRIFT SPACE. In an electron, a region free of external fields in which relative electron position depends on velocity.

DRIVE-BY-WIRE. A control system that replaces traditional mechanical or hydraulic linkages with electronic connections between control units that drive electro-mechanical actuators. Automotive by-wire includes three categories: throttle by-wire, steer by-wire, and brake by-wire. Related data; Automotive Bus Descriptions.

DRIVER. An IC used to switch on a heavily loaded net, as in bus driver [74244]. The final stage of amplification.

Droop Rate. A circuits ability to hold a stored voltage over a defined period of time. Also see Pulse Droop.

Dropout Voltage. The input-output voltage differential at which a regulator ceases to regulate against further reduction in input voltage. Dropout voltage is dependent upon load current and junction temperature. Related topics include Voltage Regulator Manufacturers, and Low Dropout Voltage Regulators.

DRUM-TYPE ARMATURE. An efficient, popular type of armature designed so that the entire length of the winding is cutting the field at all times. Most wound armatures are of this type.

DRY-AIR SYSTEM. Provides dehumidified air for electronic equipment that is moisture critical.

DRY CELL. An electrical cell in which the electrolyte is not a liquid. In most dry cells the electrolyte is in the form of a paste. [Battery Manufacturers]

D-Sub. Short for D Sub-miniature. A style of connector with the mating end shaped like the letter 'D'. For reference see; D-Sub connector pin locations. Also refer to Companies producing D-Sub connectors.

DUAL-GATE MOSFET. A two-gate MOSFET in which either gate can control the conductor independently, a fact which makes this MOSFET very versatile.

DUAL IN-LINE PACKAGE (DIP). IC package having two parallel rows of performed leads. [IC Package Type Definitions]

 

Dual In-Line Package

DUCT. In interfacility cabling, a conduit, which may be direct-earth buried or encased in concrete, used to enclose communications or power cables.

DUCTILE. The propagation of radio waves within an atmospheric duct. Easily drawn out (as to form filaments or wires).

DUCTING. Trapping of an RF wave between two layers of the earth’s atmosphere or between an atmospheric layer and the earth.

DUMMY LOAD. A dissipative but non-radiating device that has the impedance characteristics of an antenna or transmission line. Also called ARTIFICIAL LOAD. More information on [Dummy Load]

DUPLEX CIRCUIT. A circuit that permits transmission in both directions. Example RS485 Duplex Schematic. Note that the two types of duplex operation include Full-Duplex [transmission in both directions at the same time], and Half-Duplex [transmission in both directions one at a time].

DUPLEXER. A radar device that switches the antenna from the transmitter to the receiver and vice versa. Refer to the separate Dictionary of Radar Terms.

DUTY CYCLE. In a transmitter, ratio of time on to time off.

DYNAMIC MICROPHONE. A device in which sound waves move a coil of fine wire that is mounted on the back of a diaphragm and located in the magnetic field of a permanent magnet.

DYNAMIC RAM. [DRAM] A type of Volatile memory. A direct accessible memory (RAM) where the information is usually stored in the form of charges in a capacitor, DRAM must be continually powered and periodically refreshed, hence the name dynamic. Also see Volatile Memory IC Vendors

EARPHONE. A receiver placed near the ear. A transducer.

EARTH GROUND. The connection to earth. Ground. The most common connection to earth is via a water pipe. The graphic shows how to connect a Printed Circuit Board [PCB] ground to chassis ground. In many cases chassis ground will also connect to earth ground.

ECHO. The reflection of the original sound wave as it bounces off a distant surface. The RF signal reflected back from a radar target. Radar definitions are located in their own section; Radar Terms.

ECHO BOX. A resonant cavity device that is used to check the overall performance of a radar system. It receives a portion of the transmitted pulse and retransmits it back to the receiver as a slowly decaying transient.

ECL. Emitter Coupled Logic, a type of digital logic using transistors that do not go into saturation, allowing the devices to operate faster. For more detail on switching speed, ECL circuit diagram and logic family comparisons see ECL IC Manufacturers.

ECLIPSE. A condition in which the satellite is not in view or in direct line of sight with the sun. This happens when the earth is between them.

E-CORE. E-Cores expose the winding to so so heat does not get trapped inside and also makes it easier to bring out connections from several windings. See E-Transformer.

EDDY CURRENT. Induced circulating currents in a conducting material that are caused by a varying magnetic field.

EDDY CURRENT LOSS. Losses caused by random current flowing in the core of a transformer. Power is lost in the form of heat.

EDGE TRIGGERED FLIP FLOP. A type of Flip Flop [FF] that requires either a rising edge or falling edge of a clock edge to force the output to change to the level of the input signal [D].

Also refer to the 8-bit D type FF diagram.

EDISON CAP. Also called an Edison Base. A type of screw cap used with light bulbs. Also refer to Solid-state lighting for more detail and a graphic.

EDISON EFFECT. Also called Richardson Effect. The phenomenon wherein electrons emitted from a heated element within a vacuum tube will flow to a second element that is connected to a positive potential.

EEPROM. or an Electrically Erasable PROM is the same as an EPROM except that an EEPROM may be erased via an electric field, hence the term Electrically Erasable. Because these devices are erased via a voltage and not light they do not require a window like EPROMs do. A Flash EPROM is about the same as an EEPROM but does not require an addition special voltage to be erased, and may be erased all at once and not on a byte bases. Memory]. Read more; EEPROM Definition.

EFFECTIVE VALUE. Same as ROOT-MEAN-SQUARE.

EFFICIENCY. The ratio of output-signal power compared to the total input power, generally expressed as a percentage.

E-FIELD. Electric field that exists when a difference in electrical potential causes a stress in the dielectric between two points.

EIA INTERFACE. Any of a number of equipment interfaces compliant with voluntary industry standards developed by the Electronic Industries Association (EIA) to define interface parameters.

ELASTICITY. The ability of a substance to return to its original state. The force-displacement characteristic of a material.

ELECTRIC CURRENT. The flow of electrons.

ELECTRIC (E) FIELD. The field of force that is produced as a result of a voltage charge on a conductor or antenna.

ELECTRICAL CHARGE. Symbol Q, q. Electric energy stored on or in an object. The negative charge is caused by an excess of electrons; the positive charge is caused by a deficiency of electrons.

ELECTRICAL CHEMICAL. The action of converting chemical energy into electrical energy.

ELECTRICAL-LOCK. A synchro zeroing method. This method is used only when the rotors of the synchros to be zeroed are free to turn and their leads are accessible. Refer to Synchro Diagram.

ELECTRICAL POWER SYSTEM. Provides the necessary input power.

ELECTRICAL SYMBOLS. Graphic symbols used to illustrate the various electrical or electronic components of a circuit.

ELECTRICAL ZERO. A standard synchro position, with a definite set of stator voltages, that is used as the reference point for alignment of all synchro units. Refer to Synchro Diagram

ELECTRODE. The terminal at which electricity passes from one medium into another, such as in an electrical cell where the current leaves or returns to the electrolyte.

ELECTRODYNAMIC METER MOVEMENT. A meter movement using fixed field coils and a moving coil; usually used in analog ammeters and wattmeters. However digital meters have all but replaced the analog meter movement.

ELECTRODYNAMOMETER. A meter using an electrodynamic movement to measure an electric current.

ELECTROLYSIS. The process of changing the chemical composition of a material by passing an electric current through it.

ELECTROLYTE. A solution of a substance that is capable of conducting electricity. An electrolyte may be in the form of either a liquid or a paste.

ELECTROMAGNET. An electrically excited magnet capable of exerting mechanical force or of performing mechanical work.

ELECTROMAGNETIC. The term describing the relationship between electricity and magnetism. A quality that combines both magnetic and electric properties.

ELECTROMAGNETIC FIELD. The combination of an electric (E) field and a magnetic (H) field.

ELECTROMAGNETIC INDUCTION. The production of a voltage in a coil because of a change in the number of magnetic lines of force (flux linkages) passing through the coil.

ELECTROMAGNETIC INTERFERENCE. Man-made or natural interference that degrades the quality of reception of radio waves.

ELECTROMAGNETIC RADIATION. The radiation of radio waves into space.

ELECTROMAGNETIC SPEAKER. A speaker that uses an electro-magnet. Refer to Graphic of an Electromagnet Speaker.

ELECTROMAGNETISM. The generation of a magnetic field around a current-carrying conductor.

ELECTROMOTIVE FORCE (emf). The force (voltage) that produces an electric current in a circuit.

ELECTRON. The elementary negative charge that revolves around the nucleus of an atom. Additional terms relating to Electron Definitions

ELECTRONIC-EQUIPMENT DEHYDRATOR. A device that provides an alternate dry-air input in the event of failure of the central dry-air system. It may include a compressor.

ELECTRONIC FREQUENCY COUNTER. An instrument that counts the number of cycles (pulses) occurring during a precise time interval. [Frequency Counter Manufacturers]

ELECTRONICS. The term electronics as defined is a system, or equipment, with the primary purpose of which is the transmission or reception, of intelligence, and includes or comprises, communications or signal equipment, radio, radar, radiation, radio-controlling devices, meteorological, fire-control, bombing, flight and navigational instruments, power plant controls, synchronizers, photographic and test equipment [adopted from a Military airbourne specification]. Electronics employ circuits which utilize a combination of electrical or electronic devices to generate,control,indicate,or record any form of alternating or direct currents,or both.

ELECTRONIC SCANNING. Scanning in which the axis of the beam is moved, relative to the antenna axis, in a desired pattern. Also see Technical Radar Terms

ELECTRONICS DRY-AIR BRANCH. A common line for providing dry air to various electronic equipment, such as search radar, fire-control radar, and repeaters.

ELECTRONIC SWITCH. A circuit that causes a start-and-stop switching action by electronic means.

ELECTRONIC TUNING. In a reflex klystron, changing the frequency and output power of the tube by altering the repeller voltage.

ELECTROSTATIC. Pertaining to electricity at rest, such as charges on an object (static electricity).

ELECTROSTATIC DEFLECTION. The method of deflecting an electron beam by passing it between parallel charged plates mounted inside a cathode-ray tube [CRT Internal View and definitions].

Electrostatic Discharge Sensitive. (ESDS). The level of susceptibility of devices to damage by static electricity, found by classification testing, is used as the basis for assigning an ESDS class. Electronic parts having sensitive characteristics (e.g., thin-layered internal composition) and delicate, miniaturized construction which are susceptible to damage or degradation, in various degrees, from environmental field forces (electrostatic, electromagnetic, magnetic, or radioactive). This susceptibility also extends to the standard electronic modules, printed circuit boards, printed wiring boards, and circuit card assemblies containing one or more of these sensitive electronic parts. [ESD Terms]

ELECTROSTATIC FIELD. The field of influence between two differently charged bodies.

ELECTROSTATIC METER MOVEMENT. A meter movement that uses the electrostatic repulsion of two sets of charged plates (one fixed and the other movable). This meter movement reacts to voltage rather than to current and is used to measure high voltage.

ELECTROSTATIC STRESS. The force exerted on an insulator by the voltage in a conductor.

ELEMENT. A substance, in chemistry, that cannot be divided into simpler substances by any means ordinarily available. A constituent of a device that contributes directly to its operation (e.g., chip resistor, capacitor, diode, transistor, integrated circuit, surface acoustic wave (SAW), substrate, package, etc., incorporated into a device), is an element of the device. A part of an antenna that can be either an active radiator or a parasitic radiator.

EMERGENCY POWER. Temporary source of limited electrical power used upon the loss of the normal power source.

EMF (ELECTROMOTIVE FORCE). The force that causes electricity to flow between two points with different electrical charges or when there is a difference of potential between the two points. The unit of measurement is volts.

EMITTER. The element in a transistor that emits current carriers (electrons or holes). [Transistor Definitions, Transistor Manufacturers]. Transistor graphic, Common Emitter Circuit, showing bias currents.

Emitter

EMITTER-INJECTION MODULATOR. The transistor equivalent of the cathode modulator. The gain is varied by changing the voltage on the emitter.

ENAMEL. A synthetic compound of cellulose acetate (wood pulp and magnesium). Used to insulate wire in meters, relays, and motor windings.

ENCAPSULATED. Imbedded in solid material or enclosed in glass or metal.

ENCODE. To use a code to represent individual characters in a message. Here are a number of Encoding Terms.

ENCODER. A device used to encode a signal or character from one format to another. Example IC Encoder; 74HCT147, 10-to-4 line priority encoder. Encoder Schematics.
Also refer to Manufacturers of Optical Encoders, or Manufacturers of Linear Encoders.

END OF LIFE. A part or device is no longer being manufactured, however there may or may not be inventory still in stock or carried by a distributor. Also refer to Component Life Cycle Definition, or Obsolete Parts Distributors.

Energized. (alive, live) Electrically connected to a source of potential difference, or electrically charged so as to have a potential significantly different from that of earth in the vicinity.

ENERGY. The ability or capacity to do work.

EPHEMERIS. A table showing the pre-calculated position of a satellite at any given time.

Ep-Ip CURVE. The characteristic curve of an electron tube used to graphically depict the relationship between plate voltage (Ep) and plate current (Ip).

EPITAXIAL PROCESS. A method of depositing a thin, uniformly doped crystalline region (layer) on a substrate.

EPROM. EPROM. or an Erasable PROM [Programmable Read Only Memory]. Read more; EPROM Definition, Manufacturers of EPROMs.

EQUATORIAL ORBIT. An orbit that occurs when the plane of a satellite coincides with the plane of the earth at the equator.

EQUIPMENT. A general term characterizing the broad category of electronic items (units,subsystems,systems,etc.).

EQUIVALENT RESISTANCE (Req). A resistance that represents the total ohmic values of a circuit component or group of circuit components. Usually drawn as a single resistor in a simplified circuit.

ERROR. Refer to the page covering Error Terms.

ESD. ELECTROSTATIC DISCHARGE. Refer to the ESD page.

ESD STRAP. A device to ground and discharge static electricity from a person.

 

ESD Wrist Strap

Ethernet MAC Address (MAC Address): A unique 6-byte address that identifies an Ethernet device on the network. In an Ethernet packet, a MAC address is used twice, first to identify the packet's destination, and second to identify the packet's sender or source. An Ethernet MAC address is normally specified in hexadecimal, using dashes to separate bytes. For example, 08h-00h-28h-32h-17h-42h. The first three bytes normally designate the manufacturer of the device. However, when the first byte of the address is odd (LSB is 1), the address is a group address (broadcast or multicast). The second bit specifies whether the address is globally or locally administrated.

E-TRANSFORMER. A special form of differential transformer employing an E-shaped core. The secondaries of the transformer are wound on the outer legs of the E, and the primary is wound on the center leg. An output voltage is developed across the secondary coils when its armature is displaced from its neutral position. This device is used as an error detector in servo-systems that have limited load movements.

 

E-Transformer

E-TYPE T-JUNCTION. A waveguide junction in which the junction arm extends from the main waveguide in the same direction as the E-field in the waveguide. [WaveGuide Manufacturers]

Eurocard. European Packaging Specifications (IEC 60297, IEEE 1101.1, IEEE 1101.10, IEEE 1101.11). Refer to BackPlane Buses

EUTECTIC ALLOY. An alloy that changes directly from a solid to a liquid with no plastic or semi-liquid state.

EUTECTIC SOLDER. An alloy of 63 percent tin and 37 percent lead. Melts at 361º F. Note RoHS limits the amount of lead in production.

EXCESS-3 CODE. Text is in review. For a functional diagram refer to the Excess-3 to Decimal Decoder Schematic.

EXCITATION VOLTAGE. The supply voltage required to activate a circuit.

EXCITING CURRENT. The current that flows in the primary winding of a transformer when the secondary is open-circuited; it produces a magnetic flux field. Also called magnetizing current.

EXCLUSIVE OR. A function whose output is a 1 if one and only one of the input variables is a 1.

EXCLUSIVE-OR GATE. A gate that produces a logic 1 output when the inputs are different, but not when they are the same. Symbol and Truth Table below right. Standard Exclusive-OR gates include 7486, 74136, 7411086 ICs. CMOS Exclusive-OR logic gates include 4030 and 4070 ICs. Glue Logic Vendors.

EXCLUSIVE-NOR GATE. A gate that produces a logic 0 output when the inputs are different, but not when they are the same. Symbol and Truth Table below right. Standard Exclusive-NOR gates include 74266 ICs. CMOS Exclusive-NOR logic gates include 4077 ICs. Glue Logic Vendors.

EXPONENT. The numeral written in superscript (10²) which indicates the power to which the base is to be raised. Also refer to SI Prefixes.

EXPRESSION. A validated series of variables, constants, and functions that can be connected by operating symbols to describe a desired computation.

EXTERNALLY EXCITED METER. A term used to describe meters that get their power from the circuit to which they are connected.

EXTREMELY HIGH FREQUENCY. The band of frequencies from 30 gigahertz to 300 gigahertz. Table of Frequency Bands

EXTREMELY LOW FREQUENCY. The band of frequencies up to 300 hertz.

EXTRINSIC. A semiconductor in which impurities have been added to create certain charge carrier concentrations.

EYE PATTERN. An oscilloscope display in which a pseudorandom digital data signal from a receiver is repetitively sampled and applied to the vertical input, while the data rate is used to trigger the horizontal sweep.

FACTOR. Any of the elements, quantities, or symbols that, when multiplied together, form a product.

FAILSAFE. Built-in safety characteristics of a unit or system so that unit or system failure or a loss of control power will not result in an unsafe condition. The design feature of a part, unit or equipment which allows the item to fail only into a non-hazardous mode.

FAN. A component designed to move air. A set of axial fans are shown to the right, plastic box type. Fan Manufacturers. Fans may be operated of either AC or DC voltage, each has its own befits or pitfalls.

Fans

FANOUT. The number of IC gates an Integrated circuit can drive is determined by the current it can source and sink. Expanded FanOut definition.

FARAD. The basic unit of capacitance. A capacitor has a capacitance of 1 farad when a voltage potential of 1 volt across it produces a charge of 1 coulomb. [Dictionary of Capacitor Terms]

FARADAY ROTATION. The rotation of the plane of polarization of electromagnetic energy when it passes a substance influenced by a magnetic field that has a component in the direction of propagation.

FARADAY SHIELD. A common conductor connection at one end to provide electrostatic shielding without effecting electromagnetic waves. The common point connection is normally grounded. An example Graphic of Faraday Shielding

FAST BUS. IEEE Std 960-1993, FastBus Defined the Mechanical, Electrical, and Protocol for a board-to-backplane interface. This interface is obsolete.

FAST-TIME-CONSTANT CIRCUIT. Differentiator circuit in the first video amplifier that allows only the leading edges of target returns, no matter how small or large, to be used.

FAULT INDICATOR. A component or device that indicates a failure or defect in the equipment being monitored either by audio or visual indication.

 

Fault Indicator

FDDI. Fiber Distributed Data Interface is a Local Area Network [LAN] using Fiber-Optic cable in a Dual Token Ring topology. FDDI is defined in ISO 9314-1/2/3.

Feed-Thru Capacitor. A bulk-head mount filter used to pass signals into an enclosure. The most common filter element is a shunt capacitor. Read more on Feed-Thru Capacitors showing different styles.

FEP. Fluorinated Ethylene Propylene, A synthetic type of insulation.

FERRITE. A powdered and compressed ferric oxide material that has both magnetic properties and light resistance to current flow.

FERRITE SWITCH. A ferrite device that blocks the flow of energy through a waveguide by rotating the electric field 90 degrees. The rotated energy is then reflected or absorbed.

FERROMAGNETIC MATERIAL. A highly magnetic material, such as iron, cobalt, nickel, or their alloys.

FERRULE. A short metal tube used to make crimp connections to shielded or coaxial cables. The cylindrical metallic ends of a cartridge fuse or wire. Definition of a Ferrule and Manufacturers of Ferrules

Fiber Optic Cable. A fiber, multiple fiber or fiber bundle in a cable structure fabricated to meet optical mechanical and environmental specifications.

Fiber Optic Connector. A fiber optic component normally assembled onto a cable and attached to a piece of apparatus for the purpose of providing interconnecting/disconnecting of fiber optic cables.

FIBER OPTICS. Conductors or optical waveguides that readily pass light. Fiber Optic Connector Manufacturers. Also refer to Fiber Optic Connector, or Fiber Optic Cable.

Optical Fiber

FIBROUS BRAID. An outer covering used to protect a conductor’s insulating material. Commonly made from cotton, linen, silk, rayon, or fiberglass. Cable braid is also made off metal and used as a conductor shield or signal conductor. Also refer to Cable Armor

FIDELITY. The faithful reproduction of a signal. The accuracy with which a system reproduces a signal at its output that faithfully maintains the essential characteristics of the input signal.

FIELD. The electromagnet which furnishes the magnetic field that interacts with the armature in motors and generators.

FIELD-EFFECT TRANSISTOR (FET). A transistor consisting of a source, a gate, and a drain. Current flow is controlled by the transverse electric field under the gate. A transistor in which the conduction is due entirely to the flow of majority carriers through a conduction channel controlled by an electric field arising from a voltage applied between the gate and source terminals. [FET Manufacturers]

JFET

FIELD EXCITATION. The creation of a steady magnetic field within the field windings by the application of a dc voltage either from the generator itself or from an external source.

FIELD OF FORCE. A term used to describe the total force exerted by an action-at-a-distance phenomenon such as gravity upon matter, electric charges acting upon electric charges, and magnetic forces acting upon other magnets or magnetic materials.

FIELD-PROGRAMMABLE LOGIC ARRAY. FPLA. See Programmable Logic Terms and Definitions. Also refer to Manufacturers of Programmable Logic.

FILAMENT. The cathode of a thermionic tube, usually a wire or ribbon, which is heated by current passing through it. Also refer to the listing on Vacuum Tube.

FILM ICs. Conductive or non-conductive material deposited on a glass or ceramic substrate. Used for passive circuit components, resistors, and capacitors.

FILTER. A selective network of resistors, capacitors, and inductors that offers comparatively little opposition to certain frequencies, while blocking or attenuating other frequencies. In electronics, a device that transmits only part of the incident energy and may thereby change the spectral distribution of energy: (a) high-pass filters transmit energy above a certain frequency; (b) low-pass filters transmit energy below a certain frequency; (c) bandpass filters transmit energy of a certain bandwidth; (d) band-stop filters transmit energy outside a specific frequency band. Refer to the entry on Passive Filters.

 

Low Pass PI Filter

 

FILTER RESPONSE. The output response of an active or passive filter. Refer to the definition of Filter for the different types. The graph shows the different orders of a Butterworth Filter, 1st order filter to fifth order.

Butterworth Filter

FINAL POWER AMPLIFIER (FPA). The final stage of amplification in a transmitter.

FIRMWARE. A software program which is permanently stored in Non-Volatile Memory [ROM].

FIRST DETECTOR. See MIXER.

FIXED BIAS. A constant value of bias voltage.

FIXED RESISTOR. A resistor having a definite resistance value that cannot be adjusted. Also refer to Resistor Definitions. Resistor Manufacturers

FIXED SPARK GAP. A device used to discharge the pulse-forming network. A trigger pulse ionizes the air between two contacts to initiate the discharge.

FLAG. In data transmission or processing, an indicator, such as a signal, symbol, character, or digit, used for identification. A flag may be a byte, word, mark, group mark, or letter that signals the occurrence of some condition or event, such as the end of a word, block, or message. Also see Protocol Definitions

FLAT LINE. A transmission line that has no standing waves. This line requires no special timing devices to transfer maximum power.

FLAT PACK. An IC package. IC Package Type Definitions

FLEMING VALVE. A two-electrode vacuum tube used as a detector. Also refer to the listing on Vacuum Tubes.

FLEXIBLE COAXIAL LINE. A line made with an inner conductor that consists of flexible wire insulated from the outer conductor by a solid, continuous insulating material. Refer to the Definition of Coax Cable. Manufacturers of Coax Cable

FLIP CHIP. A monolithic IC packaging technique that eliminates the need for bonding wires.

FLIP-FLOP. A device having two stable states and two input terminals (or types of input signals), each of which corresponds with one of the two states. The circuit remains in either state until caused to change to the other state by application of a voltage pulse. A similar bistable device with an input that allows it to act as a single-stage binary counter. The four basic types of Flip Flops include a D Flip Flop, a T flip flop, an RS flip flop and a JK Flip Flop. Also refer to Multivibrator.

FLOATING INPUT. An input pin that is not tied to a supply rail and could float to an invalid logic level. An input pin that does not have an internal pull-up or pull-down and requires an external pull-up resistor which is not present. An input pin with no defined logic level and will float to any voltage, however most pins slowly drift high.

FLOPPY. The Floppy disk drive stored data on a small, circular piece of metal-coated plastic. A Floppy disk drive could read and write data to/from the disk and it's controller. The transfer speed of a FDD is relatively slow, and the data storage capacity vary low. Data transfer speeds for Floppy Disk Drives [FDD] normally are 250KBps for the 720KB disk size and 500KBps for the 1.44MB disk size. Two common size devices are produced for the 3.5 inch floppy drive; the standard version 25.4 x 101.6 x 146mm [H x W x D], and a reduced size version 12.7 x 96 x 126mm [H x W x D]. FDD devices are obsolete and were replaced in 2005 by USB flash drives. [FDD Manufacturers]

FLUX. In electrical or electromagnetic devices, a general term used to designate collectively all the electric or magnetic lines of force in a region. A solution that removes surface oxides from metals being soldered.

FLUX DENSITY. The number of magnetic lines of force passing through a given area.

FLY-BY-OPTIC. An avionics bus that uses fiber-optic interfaces and fiber cable to replace copper wire. See Fly-By-Wire.

FLY-BY-WIRE. A term used in the aerospace industry that denotes a control system that replaces traditional mechanical or hydraulic linkages with electronic connections between control units that drive electro-mechanical actuators. Also refer to; Avionic Bus Descriptions.

F-22 Flight Displays

FLYWHEEL EFFECT. The ability of a resonant circuit to operate continuously because of stored energy or energy pulses.

FM Receiver. A receiver that decodes a Frequency Modulated signal to recover encoded information.

FM Receiver Block Diagram

FOCUSING ANODE. An electrode of a CRT that is used to focus the electrons into a tight beam.

FOLDED DIPOLE. An ordinary half-wave antenna (dipole) that has one or more additional conductors connected across the ends parallel to each other. Antenna Dictionary

FORBIDDEN BAND. The energy band in an atom lying between the conduction band and the valence band. Electrons are never found in the forbidden band but may travel back and forth through it. The forbidden band determines whether a solid material will act as a conductor, a semi-conductor, or an insulator.

FORWARD AGC. The type of AGC that causes an amplifier to be driven towards saturation. Also see the Radar section for AGC.

FORWARD BIAS. An external voltage that is applied to a PN junction in the conducting direction so that the junction offers only minimum resistance to the flow of current. Conduction is accomplished by majority current carriers (holes in P-type material; electrons in N-type material). Refer to the graph to the right.

FORWARD RESISTANCE. The smaller resistance value observed when you are checking the resistance of a semiconductor.

FOSTER-SEELEY DISCRIMINATOR. A circuit that uses a double-tuned RF transformer to convert frequency variations in the received FM signal to amplitude variations. Also known as a phase-shift discriminator.

FRACTIONAL T1. In the North American or Japanese hierarchies, the tariffed use of a data rate corresponding to fewer than the 24 channels served by a T1 line.

FRAME. A portion of a message. The frame is any construction system fitted and united together, designed for mounting or supporting electrical or electronic parts or units.

FRAME RELAY. An interface protocol for statistically multiplexed packet-switched data communications in which (a) variable-sized packets (frames) are used that completely enclose the user packets they transport, and (b) transmission rates are usually between 56 kb/s and 1.544 Mb/s (the T-1 rate).

FRAMING. The process of synchronizing a facsimile receiver to a transmitter. This allows proper picture reproduction.

FREE-SPACE LOSS. The loss of energy of radio waves caused by the spreading of the wavefront as it travels from the transmitter.

Frequency (f). The number of complete cycles per second existing in any form of wave motion, such as the number of cycles per second of an alternating current. The rate at which the vector that generates a sine wave rotates.

FREQUENCY COMPENSATION NETWORK. A circuit modification used to improve or broaden the linearity of its frequency response.

FREQUENCY CUTOFF. The frequency at which the filter circuit changes from an action of rejecting the unwanted frequencies to an action of passing the desired frequencies. Conversely, the point at which the filter circuit changes from an action in which it passes the desired frequencies to an action in which it rejects the undesired frequencies.

FREQUENCY-DETERMINING NETWORK. A circuit that provides the desired response (maximum or minimum impedance) at a specific frequency.

FREQUENCY DEVIATION. The amount the frequency varies from the carrier frequency.

FREQUENCY DIVERSITY. Transmitting (and receiving) of radio waves on two different frequencies simultaneously.

FREQUENCY-DIVISION MULTIPLEXING. Multiplexing that transmits and receives the full 360 degrees of each sine wave.

Frequency Doubler. A circuit that doubles the frequency of the input. A Frequency Doubler Circuit. A Frequency Doubler circuit may also be called a Second Harmonic Generator or a Frequency Multiplier; however a Frequency Multiplier could generate any harmonic.

FREQUENCY METER. A meter used to measure the frequency of an ac signal. An electronic instrument that displays the frequency of an incoming signal. The frequency is determined by comparing the signal to the counter's time base oscillator. [Frequency Meter Manufacturers]

FREQUENCY MIXER. A circuit that accepts two input signals at two different frequencies, and produces an output frequency equal to the difference of the two inputs. [Frequency Meter Manufacturers]

FREQUENCY MODULATION (fm). A signaling method that varies the carrier frequency in proportion to the amplitude of the modulating signal. Angle modulation in which the modulating signal causes the carrier frequency to vary. The amplitude of the modulating signal determines how far the frequency changes, and the frequency of the modulating signal determines how fast the frequency changes.

 

Frequency Modulation

FREQUENCY MULTIPLIERS. Special RF power amplifiers that multiply the input frequency. A circuit that converts an incoming signal to a higher frequency by adding a fixed multiple of cycles or pulses to the signal. [RF Frequency Doubler Manufacturers].

FREQUENCY RESPONSE. The measurement of how a circuit or device reacts to different frequencies that are applied to it. The part of a frequency regain than can be sensed by a device. The measure of a servo’s ability to respond to various input frequencies.

FREQUENCY-RESPONSE CURVE. A curve showing the output of an amplifier (or any other device) in terms of voltage or current plotted against frequency with a fixed-amplitude input signal.

FREQUENCY SCANNING. Varying the output frequency to achieve electronic scanning.

FREQUENCY-SHIFT KEYING (fsk). Frequency modulation somewhat similar to continuous-wave (cw) keying in AM transmitters. The carrier is shifted between two differing frequencies by opening and closing a key.

FREQUENCY STABILITY. Refers to the ability of an oscillator to accurately maintain its operating frequency. The degree to which an oscillating signal produces the same frequency for a specified interval of time [short-term stability, or long-term stability].

FREQUENCY STANDARD. An oscillator used as a reference source for frequency measurements.

FREQUENCY SYNTHESIS. A process that uses hetrodyning and frequency selection to produce a signal.

FREQUENCY SYNTHESIZER. A frequency source of high accuracy. A bank of oscillators in which the outputs can be mixed in various combinations to produce a wide range of frequencies.

FRONT-TO-BACK RATIO. The ratio of the energy radiated in the principal direction compared to the energy radiated in the opposite direction.

FUEL CELL. A fuel cell converts energy generated by chemical reaction into electrical energy. Its function is similar to a battery, except that the chemicals generally are supplied from outside the cell.

FULL-DUPLEX CIRCUIT. A circuit that permits simultaneous transmission in both directions. A number of interface buses use a Full-Duplex Circuits, Communication over Gigabit Ethernet is one example.

FULL-WAVE RECTIFIER. A circuit that uses both positive and negative alternations in an alternating current to produce direct current. There are two general circuit configurations; A two diode circuit that requires a center tapped transformer and a four diode approach that does not require a center tapped transformer. [Full-Wave Rectifier Circuit Schematic]

 

Full-Wave Rectifier Circuit

FULL-WAVE VOLTAGE DOUBLER. Consists of two half-wave voltage rectifiers and is used to reduce the output ripple amplitude.

FUNCTION. A specific purpose of an entity; its characteristic action.

FUNDAMENTAL FREQUENCY. The basic frequency or first harmonic frequency.

Fungus-inert material. A material which, in all modified states and grades, is not a nutrient to fungi.

FUSE. A device that has as its critical component a metal wire or strip that will melt when heated by a prescribed (design) amperage, creating an open in the circuit of which it is a part, thereby protecting the circuit from an over current condition. Note on operating AC Fuses in DC circuits; Maximum Fuse Voltage. [Fuse Manufacturers]

 

Axial Leaded Fuse

FUSED-ALLOY JUNCTION. See ALLOYED-JUNCTION.

FUSED HOLDER. A device used to hold a fuse. The shape of the fuse holder used is determined by the style of fuse being used. Two common style of fuse holders include Block Fuse Holders, and Panel Mount Fuse Holders. Refer here for Manufacturers of Fuse Holders.

Fuse Holder

FUTUREBUS. IEEE-896. Futurebus is a back-plane bus standard that defines both the Physical and Electrical layers for the interface. The follow-on specification was called Futurebus+, which was an upgrade.

GAIN. Any increase in the strength of a signal. The ratio between the amount of energy propagated from an antenna that is directional compared to the energy from the same antenna that would be propagated if the antenna were not directional.

GAIN-BANDWIDTH PRODUCT. The number that results when the gain of a circuit is multiplied by the bandwidth of that circuit. For an operational amplifier, the gain-bandwidth product for one configuration will always equal the gain-bandwidth product for any other configuration of the same amplifier.

GALVANOMETER. A meter used to measure small values of current by electromagnetic or electrodynamic means.

GAMMA. The transistor emitter-to-base current ratio in a common-collector configuration. Gamma Ray; Emissions of a specific frequency produced from sub-atomic particle interaction.

GANGED TUNING. The process used to tune two or more circuits with a single control.

GATE. As applied to logic circuitry, one of several different types of electronic devices that will provide a particular output when specified input conditions are satisfied. Gate; as in AND Gate, OR Gate, NOR Gate, or NAND Gate. Also, a circuit in which a signal switches another signal on or off.

GATED AGC. Circuit that permits automatic gain control to function only during short time intervals.

GATED-BEAM DETECTOR. An FM demodulator that uses a special gated-beam tube to limit, detect, and amplify the received FM signal. Also known as a quadrature detector.

GATING. The process of selecting those portions of a wave that exist during one or more selected time intervals or that have magnitudes between selected limits. Also, the application of a specific waveform to perform electronic switching.

GENDER CHANGER. A component that changes the Gender of a connector or cable assembly. Refer to the full Gender Changer Definition.

 

SMA Gender Changer

GENERATOR. A machine that converts mechanical energy to electrical energy by applying the principle of magnetic induction. A machine that produces ac or dc voltage, depending on the original design.

GERMANIUM. Symbol Ge in the periodic table. A grayish-white metal having semiconductor properties, similar to tin.

GFI. See Ground Fault Interrupter.

GIMBAL. A mechanical frame, with two perpendicular intersecting axes of rotation, used to support and furnish a gyro wheel with the necessary freedom to tilt in any direction.

GLOBAL POSITIONING SYSTEM (GPS). A US satellite system that lets those on the ground, on the water or in the air determine their position using GPS receivers. Additional GPS data and links.

GLOW DISCHARGE. Discharge of electricity through a gas in an electron tube.

GRAY CODE. A positional binary number notation in which any two numbers whose difference is one is represented by expressions that are the same except in one place. Refer to the Gray Code listing for more information.

GRAMME-RING ARMATURE. An inefficient type of armature winding in which many of the turns are shielded from the field by its own iron ring.

GRID BIAS. A constant fixed potential applied between the grid and the cathode of a vacuum tube to establish an operating point.

GRID CURRENT. The current that flows in the grid-to-cathode circuit of a vacuum tube.

GRID-GAP TUNING. A method of changing the center frequency of a resonant cavity by physically changing the distance between the cavity grids.

GRID-LEAK BIAS. A self-bias provided by a high resistance connected across the grid capacitor or between the grid and cathode.

Grommet. An insulator that covers sharp edges of holes through panels and partitions to protect wire insulation from cut-through damage.

Grommet, Connector. An elastomeric seal used on the cable side of a connector body to seal the connector against contamination and to provide stress relief.

GROUND. The point in a circuit used as a common reference point for measuring purposes. To connect some point of an electrical circuit or some item of electrical equipment to earth or to the conducting medium used in lieu thereof. A conducting connection, whether intentional or accidental, between a circuit or piece of equipment and the earth, or some body serving as earth; a place of zero electrical potential.

GROUND BOUNCE. Ground bounce refers to the ringing on an output signal when one or more outputs on the same device are being switched from HIGH to LOW. Ground bounce is associated with the inductance and resistance of the ground connection in the integrated circuit. More detailed definition of Ground Bounce.

GROUND CLUTTER. Unwanted echoes, from surrounding land masses, that appear on a radar indicator. [Radar terms, and definitions]

GROUND-CONTROLLED APPROACH. A radar system used to guide aircraft to safe landings in poor visibility conditions.

GROUND FAULT INTERRUPTER. [GFI] A protective device that detects abnormal current flowing to ground and then interrupts the circuit. Detailed Ground Fault Interrupter definition

GROUND ISLAND . A small copper layer contained on one or more layers of a Printed Wiring Board which is only connected to ground. A Ground Island is always much smaller than a ground plane. Ground Islands may be 100% copper fill or hatched to reduce the amount of copper. Refer to PWB terms and definitions.

PWB Ground Islands

GROUND PIN CURRENT. [Voltage Regulator] is the regulator quiescent current plus pass transistor base current. Ground Pin Current is defined as the amount of current required by the regulator when driving a load. Ground Pin Current varies with regulator input voltage and regulator load. The lower the Ground Pin Current the more efficient the device is. Power consumption of a voltage regulator may be found by multipling the Ground Pin Current and the difference in voltage across the device [Vo/Vi]. [IC General] the current flowing through the ground pin; however this is not a definition in common usage.

GROUND PLANE. A large copper layer contained on one or more layers of a Printed Wiring Board [PWB] which is only connected to ground. In most cases a ground plane covers most if not all of the PWB layer it resides on. The portion of a ground-plane antenna that acts as ground.

GROUND-PLANE ANTENNA. A type of antenna that uses a ground plane as a simulated ground to produce low-angle radiation. [Antenna terms, and definitions]

GROUND PLANES. Copper planes used to minimize interference between circuits and from external sources. The large islands or complete planes are connected to ground.

GROUND POTENTIAL. Zero potential with respect to the ground or earth.

GROUND RANGE. The distance on the surface of the earth between a radar and its target. Equal to slant range only if both radar and target are at the same altitude.

GROUND REFLECTION LOSS. The loss of RF energy each time a radio wave is reflected from the earth’s surface.

GROUND ROD. An earth electrode subsystem installed by the responsible facilities engineering activities at each facility to provide a low resistance path to earth for lightning and power fault currents and ensure that hazardous voltages do not occur within the facility. This subsystem shall be capable of dissipating to earth the energy of direct lightning strokes with no ensuing degradation to itself. This system shall also interconnect all driven electrodes and underground metal objects of the facility. The earth electrode [Ground Rod] subsystem shall not degrade the quality of signals in the signal circuits connected to it. The rods shall be interconnected with a 1/0 AWG (American Wire Gage) bare copper cable buried at least .45m (1.5 feet) below grade level. Larger size cables as well as greater burial depths shall be specified where earth and atmosphere considerations so dictate. The interconnecting cable shall be brazed or welded to each ground rod and shall close on itself to form a complete loop with the ends brazed or welded together.

GROUND SCREEN. A series of conductors buried below the surface of the earth and arranged in a radial pattern. Used to reduce losses in the ground.

GROUND WAVES. Radio waves which travel near the surface of the earth.

GROUP. A collection of units, assemblies, sub-assemblies, and parts. It is a subdivision of a set or system but is not capable of performing a complete operational function.

GROUP VELOCITY. The forward progress velocity of a wave front in a waveguide.

GROWN JUNCTION. A method of mixing P-type and N-type impurities into a single crystal while the crystal is being grown.

GUIDANCE RADAR. A system which provides information that is used to guide a missile to a target. [Radar terms, and definitions]

GYROSCOPE. A mechanical device containing a spinning mass mounted so that it can assume any position in space. The Abbreviation for gyroscope is Gyro.

HALF-Duplex. Data flow in either direction, but not in both directions at the same time. There are a number of interface buses that only allow Half-Duplex operation, while some bus networks just add a redundant path in the opposite direction to allow communication in either direction at the same time. Operation in both directions at the same time is called Full-Duplex. An Abbreviation for half duplex is HDX.

HALF-POWER POINT. A point on a waveform or radar beam that corresponds to half the power of the maximum power point.

HALF-WAVE RECTIFIER. A rectifier using only one-half of each cycle to change ac to pulsating dc. Half-Wave Rectifier Circuit.

HALF-WAVE VOLTAGE DOUBLER. Two half-wave voltage rectifiers connected to double the input voltage.

HAND-SHAKE. The interchange of signals between a 'talker' and a 'listener' to exchange data on a bus. During a Handshake a listener [slave] indicates ready for data, a talker [master] indicates data ready, the slave then indicates data received. Read more on the Handshaking Protocol.

Hard Disk. [HD] A flat, circular, rigid plate with a magnetizable surface on one or both sides used to store data. Also called a Hard Disk Drive [HDD]. Note: A hard disk is distinguished from a diskette [floppy Disk] by virtue of the fact that it is rigid and not considered removable. Manufacturers of Hard Disk Drives.

Hard Disk Drive

HARD-TUBE MODULATOR. A high-vacuum electron tube modulator that uses a driver for pulse forming. See Vacuum Tube.

Harmonic. A frequency that is a whole-number multiple of a smaller base frequency. Of a sinusoidal wave, an integral multiple of the frequency of the wave. Harmonic percentages of a half sine wave; 2nd, 21.2%, 3rd, 0%, 4th 4.2%, 5th, 0% and 6th harmonic is 1.8%.

Harmonic Distortion. A ratio of 100 times the sum of all the harmonics to the fundamental.

HARNESS. An assembly of wires or cables, or wires and cables arranged so it may be installed or removed as a unit in the same electronic or electrical equipment. One or more insulated wires or cables, with or without helical twist; with or without common covering, jacket, or braid; with or without breakouts; assembled with two or more electrical termination devices; and so arranged that as a unit it can be assembled and handled as one assembly. Also refer to Cable Harness Discussion for additional information.

HDLC. High-level Data Link Control is a group of protocols for transmitting [synchronous] data Packets between Point-to-Point nodes. Data is organized into a frame in HDLC. HDLC protocol resides with Layer 2 of the OSI model, the data link layer.

HEADER. Normally a male connector having exposed pins which are molded into a plastic base. Headers are produced in either signal row or double row having a minimum of two pins. A 1-pin header would just a test-point. Common Headers are 0.1 inch spacing, pin-to-pin. Female connectors having the same spacing are used to interface. Headers are common in PC motherboards, and are very common as Jumper blocks. For more information and some graphics refer to Standard Headers. Also see Header Manufacturers

HEAD ROOM. Safety Margin. High-Temperature Operation

HEATER. Same term as a Filament.

HEAT SHUNT. A device (preferably a clip-on type) used to absorb heat and protect heat-sensitive components during soldering.

HEAT SINK. A metallic device that dissipates or radiates into the surrounding air the heat that is generated from an integrated circuit or other device. [Heat Sink Manufacturers]. The point of the heat sink is to increase the surface area effected by the surrounding air. Most air cooled heat sinks are convection limited, and the overall thermal performance of an air cooled heat sink can often be improved significantly if more surface area can be exposed to the air stream.

 

TO-3 Heat Sink

HELIX. A spirally wound transmission line used in a traveling-wave tube to delay the forward progress of the input traveling wave. A large coil of wire. It acts as a coil and is used with variable inductors for impedance matching of high-power transmitters.

HELIX HOUSE. A building at a transmitter site that contains antenna loading, coupling, and tuning circuits.

HENRY (H). The electromagnetic unit of inductance or mutual inductance. The inductance of a circuit is 1 henry when a current variation of 1 ampere per second induces 1 volt. In electronics, smaller units are used, such as the millihenry (mH), which is one-thousandth of a henry (H), and the microhenry (µH) which is one-millionth of a henry.

HERMETIC. Sealed so that an object is gas-tight to a specific rate, normally less than 1 x 10-6 cc/sec of helium.

HERMETIC SEAL. A hermetic seal results from fusing metal-to-metal, ceramic-to-metal, or glass-to-metal only. Hermetic sealing is the process by which an item is totally enclosed by a suitable metal structure or case by fusion of metallic or ceramic materials. This includes the fusion of metals by welding,brazing, or soldering; the fusion of ceramic materials under heat or pressure; and the fusion of ceramic material on to a metallic support.

HERTZ (Hz). A unit of frequency equal to one cycle per second.

HETERODYNE. To generate new frequencies by mixing two or more signals in a nonlinear device.

HETERODYNE DETECTION. The use of an a.f. voltage to distinguish between available signals. The incoming cw signal is mixed with locally generated oscillations to give an a.f. output.

HETERODYNING. The process of mixing two frequencies across a nonlinear impedance. The process of mixing the incoming signal with the local oscillator frequency. This produces the two fundamentals and the sum and difference frequencies.

HEXADECIMAL. Same as SEXADECIMAL. A number system with a base of sixteen; also pertains to conditions, choices, or selections that have sixteen possible values or states.

HEXADECIMAL SYSTEM. Pertaining to the number system with a radix of sixteen. It uses the ten digits of the decimal system and the first six letters of the English alphabet. [Hex Table]

H-Field. Any space or region in which a magnetic force is exerted. The magnetic field may be produced by a current-carrying coil or conductor, by a permanent magnet, or by the earth itself.

HIC. Heterogeneous Interconnect bus provides a bidirectional serial interconnect which builds a scalable parallel system using pairs of unidirectional lines. IEEE-1355 defines the physical and Logic Link layers between a Chip-to-Chip, Board-to-Board, or Chassis-to-Chassis interface. The HIC interface is obsolete.

High Frequency. The band of frequencies from 3 megahertz to 30 megahertz.

High Frequency Compensation. See Peaking Coil.

High Frequency Distortion. Frequency distortion which effects higher frequencies. Distortion

High-Level Modulation. Modulation produced in the plate circuit of the last radio stage of the system.

High-Pass Filter. A filter that passes a majority of the high frequencies on to the next circuit and rejects, or attenuates, the lower frequencies. Also called a Low-Frequency Discriminator. Refer to the entry on Passive Filters.

HIPPI. [High-Performance Parallel Interface] The HIPPI specification defines the mechanical, electrical and signalling protocol for a high performance simplex interface [data transmits in one direction only]. An additional HPPI interface is required to transmit data in a full-duplex mode. The HIPPI interface is obsolete. HIPPI Description

Holding Coil. A separate coil within a relay that stays energized after the original current has been removed.

Hold Time. The time required to keep the data at the input to a register stable, after the device has been clocked. Also refer to Metastability.

HOLE FLOW. In the valence band, a process of conduction in which electrons move into holes, thereby creating other holes that appear to move toward a negative potential. (The movement of holes is opposite the movement of electrons.)

HOOKUP WIRE. Hookup wire refers to an insulated conductor free at both ends and used for chassis wiring and interconnecting wiring. Manufacturers of Hookup wire.

HORIZONTAL AXIS. On a graph, the straight line axis that is plotted from left to right.

HORIZONTAL-DEFLECTION PLATES. A pair of parallel electrodes that moves the electron beam from side to side in a CRT.

HORIZONTALLY POLARIZED. Waves radiated with their E field component parallel to the earth’s surface.

HORIZONTAL PATTERN. The part of a radiation pattern that is radiated in all directions along the horizontal plane.

HORIZONTAL PLANE. An imaginary plane that is tangent (or parallel) to the earth’s surface at a given location.

HORN SPEAKER. A type of speaker. Refer to Manufacturers of Speakers for additional information and vendors.

 

Horn Speaker

HORSEPOWER. The English unit of power equal to work done at the rate of 550 foot-pounds per second; equal to 746 watts of electrical power.

HORSESHOE MAGNET. A permanent magnet or electromagnet bent into the shape of a horseshoe or having a U-shape to bring the two poles near each other.

HOT CARRIER. A carrier, which may be either a hole or an electron, that has relatively high energy with respect to the carriers normally found in majority-carrier devices.

HOT-CARRIER DIODE. A semiconductor diode in which hot carriers are emitted from a semiconductor layer into the metal base. Also called HOT-ELECTRON DIODE. An example is the Schottky barrier diode.

Hot-Plug Slot. A chassis slot designed to allow the insertion and removal of add-in cards without powering down the Platform or restarting the operating system. A Hot-Plug controller is used to control signals on the bus's slot while the card is removed and replaced.

Hot Swap. The generic ability to remove and replace a component or piece of gear while it is still powered up with in a chassis. Commonly used to replace operational boards that have failed within a chassis. The cards have power and ground pins that are longer than the bus interface pins so the board is already powered by the time the interfacing pins make contact with the chassis.

HOT-WIRE METER MOVEMENT. A meter movement that uses the expansion of a heated wire to move the pointer of a meter; measures dc or ac.

HPIB. Hewlett-Packard Interface Bus. Another name for the GPIB interface, see also IEEE-488

HSSI. High Speed Serial Interface. The HSSI interface uses differential ECL lines to transmit data at 52Mbps out to a maximum distance of 50 feet, also EIA613.

H-TYPE T-JUNCTION. A waveguide junction in which the junction arm is parallel to the magnetic lines of force in the main waveguide.

HUB. A multi-port device that acts as a switch or repeater connecting one incoming port to another. The Hub may be wired or wireless.

Ethernet Hub

HYBRID CIRCUIT. A circuit where passive components (resistors, capacitors) are deposited onto a substrate made of glass, ceramic, or other insulating material. Then the active components (diodes, transistors) are attached to the substrate and connected to the passive components on the substrate with a very fine wire.

HYBRID ICs. Two or more integrated circuit types, or one or more integrated circuit types and discrete components on a single substrate.

Hybrid IC PWB

HYBRID JUNCTION. A waveguide junction that combines two or more basic T-junctions.

HYBRID MIXER. See BALANCED MIXER. RF Mixer Manufacturers

HYBRID NETWORK. A communication network that uses more than one network topology. For additional information refer to the page covering Information network topologies.

HYBRID RING. A hybrid-waveguide junction that combines a series of E-type T-junctions in a ring configuration. When properly terminated, energy is transferred from any one branch into any two of the remaining three branches. A type of network topology.

HYDROMETER. An instrument used to measure specific gravity. In batteries hydrometers are used to indicate the state of charge by the specific gravity of the electrolyte.

HyperTransport. A Point-to-Point interface with at least two unidirectional links. The HyperTransport has a data rate of 800M Bytes/ps using 8 bit pairs and a 400MHz clock.

HYSTERESIS. The time lag of the magnetic flux in a magnetic material behind the magnetizing force producing it. Caused by the molecular friction of the molecules trying to align themselves with the magnetic force applied to the material.

HYSTERESIS LOOP. [B-H Loop]. A Hysteresis loop showing the relationship between [B] Flex Density and [H] Magnetizing Force.

HYSTERESIS LOSS. The power loss in an iron-core transformer or other alternating-current device as a result of magnetic hysteresis.

HZ. Hertz. A unit of frequency equal to one cycle per second.

I2C. Originally designed to be a battery control interface, now used in micro-controller based [uP] professional, consumer and telecommunications control, diagnostic and power management buses. The I2C bus uses a bi-directional Serial Clock Line [SCL] and Serial Data Lines [SDA]. Three speed modes are specified: Standard; 100kbps [Bits per Second], Fast mode; 400kbps, High speed mode 3.4Mbps. I2C is short for Inter-IC.

I2R LOSS. I-Squared-R losses, or Current [squared] x Resistance. Also called Copper Losses. The power lost because of the current through a resistanc.

IC. Refer to the definition of Integrated Circuit.

IC SYNCHROS. Obsolete, synchros with reverse rotation and limited torque capabilities.

IDE. Integrated Drive Electronics (Advanced Technology Attachment). A series of standards released between 1999 and 2005 which defined the electrical and mechanical interfaces between a personal computer's mother board and a Hard Disk Drive. Maximum bus speed of the IDE bus is 133MBps over an 18 inch Parallel cable. The IDE interface is also known as the ATA interface. The ATA interface was rendered obsolete by the introduction of the Serial ATA [SATA] interface in 2005.

IDEMPOTENT LAW. In Boolean algebra, combining a quantity with itself either by logical addition or logical multiplication will result in a logical sum or product that is the equivalent of the quantity (for example, A + A = A; A • A = A).

IDENTITY LAW. In Boolean algebra, the law which states that any expression is equal to itself.

IDLE-CHANNEL NOISE. Noise that is present in a communications channel when no signals are applied. The channel conditions and terminations must be stated for idle-channel noise measurements to be meaningful.

IDLER FREQUENCY. In a parametric amplifier, the difference between the input signal and the pump signal frequency. Also called the LOWER-SIDEBAND FREQUENCY.

IEEE-1284. A personal Computer interface that defined a parallel printer bus specification at 1MBps. IEEE-1284 defines a Point-To-Point asynchronous bi-directional interface. Devices may be either 1284 compatible {the older parallel port devices} or 1284 compliant. The maximum length for a printer cable is 25 feet, 32 feet maximum. Centronics parallel cables run out to 12 feet. The IEEE1284 cable replaced the 'Centronics' cable which is obsolete.

IF AMPLIFIER. Usually a narrow-bandwidth IF amplifier that is tuned to one of the output frequencies produced by the mixer.

IGFET. Insulated Gate Field-Effect Transistor. Any FET that has an insulated gate. Also see FET manufacturers.

IMAGE FREQUENCY. An undesired frequency capable of producing the desired frequency through heterodyning.

IMPEDANCE. The total opposition offered to the flow of an alternating current. It may consist of any combination of resistance, inductive reactance, and capacitive reactance. The symbol for impedance is Z.

IMPLOSION. The inward bursting of a CRT because of high vacuum [Definition of CRT]. The opposite of explosion.

IMPULSE WAVEFORM. A short duration pulse. The pulse duration is defined from the peak duration to 50 percent of peak.

 

Impulse Duration

INCIDENT WAVE. The wave that strikes the surface of a medium. The wave that travels from the sending end to the receiving end of a transmission line.

IN-CIRCUIT METER. A meter permanently installed in a circuit; used to monitor circuit operation.

INCOHERENT. Refers to radiation on a broad band of frequencies.

INDEX OF REFRACTION. The degree of bending of an RF wave when passing from one medium to another.

INDIRECTLY HEATED CATHODE. Same as the directly heated cathode with one exception: The hot filament raises the temperature of the sleeve around the filament; the sleeve then becomes the electron emitter.

INDUCED-CHANNEL MOSFET. A MOSFET in which there is no actual channel between the source and the drain. This MOSFET is constructed by making the channel of the same type of material as the substrate.

INDUCED CHARGE. An electrostatic charge produced on an object by the electric field that surrounds a nearby object.

INDUCED CURRENT. Current caused by the relative motion between a conductor and a magnetic field.

INDUCED ELECTROMOTIVE FORCE. The electromotive force induced in a conductor because of the relative motion between the conductor and a magnetic field.

INDUCED VOLTAGE. See INDUCED ELECTROMOTIVE FORCE.

INDUCTANCE. The property of a circuit that tends to oppose a change in the existing current flow. The symbol for inductance is L.

INDUCTANCE BRIDGE. An ac bridge circuit used to measure an unknown value of inductance.

INDUCTION. The act or process of producing voltage and current by the relative motion of a magnetic field across a conductor.

INDUCTION FIELD. The electromagnetic field that is produced about an antenna when current and voltage are present on the same antenna.

INDUCTION LOSSES. The losses that occur when the electromagnetic field around a conductor cuts through nearby metallic objects and induces a current into that object.

INDUCTION MOTOR. A simple, rugged, ac motor with desirable characteristics. The rotor is energized by transformer action (induction) from the stator. Induction motors are used more than any other type. [Motor Manufacturers]

INDUCTIVE COUPLING. The transfer of energy from one circuit to another by virtue of the mutual inductance between the circuits. Coupling of two coils by means of magnetic lines of force. In transformers, coupling applied through magnetic lines of force between the primary and secondary windings.

INDUCTIVE REACTANCE. The opposition to the flow of an alternating current caused by the inductance of a circuit, expressed in ohms. Identified by the symbol X L.

Inductor. A 2-terminal passive device having a coil of wire wound wrapped around a core [which may be magnetic metal or air] to produce a high inductance in the wire.

INERTIA. The physical tendency of a body in motion to remain in motion and a body at rest to remain at rest unless acted upon by an outside force (Newton’s First Law of Motion).

INFINITE. Extending indefinitely, endless. Boundless, having no limits. An incalculable number.

INFRALOW FREQUENCY. The band of frequencies from 300 Hz to 3,000 Hz.

INFRARED. The region of the electromagnetic spectrum bounded by the long-wavelength extreme of the visible spectrum (approximately 0.7 µm) and the shortest microwaves (approximately 0.1 mm).(IR)

INFRASONIC. Sounds below 15 Hz. (SUBSONIC)

IN PHASE. Applied to the condition that exists when two waves of the same frequency pass through their maximum and minimum values of like polarity at the same instant. Voltage and current are in-phase across a resistor but out of phase in a capacitor or Inductor. Note the maximum value of the current wave or voltage may be any value, as long as they reach their maximum point at the same time.

In-Phase waves

INPUT. The current, voltage, power, or driving force applied to a circuit or device. The input signal applied to an IC.

INPUT END. The end of a two-wire transmission line that is connected to a source.

INPUT IMPEDANCE. Impedance presented to the transmitter by the transmission line and its load.

INPUT/OUTPUT. Pertaining to either input or output or both, especially in data processors.

Insertion Loss. The difference in power level between a device being inserted in the transmission path and, not being inserted in the transmission path.

Isolation. The RF leakage from the path in use to another device outside the path.

INSTANTANEOUS AMPLITUDE. The amplitude at any given point along a sine wave at a specific instant in time.

INSTANTANEOUS AUTOMATIC GAIN CONTROL. [IAGC] A circuit that can vary the gain of the radar receiver with each input pulse to maintain a nearly constant output peak amplitude.

INSTANTANEOUS VALUE. The magnitude at any particular instant when a value is continually varying with respect to time.

INSTRUMENTATION AMPLIFIER. A differential amplifier utilizing an input buffer on both the positive and negative input lines. This example uses operational amplifies and its associated resistors required to produce gain.

 

Instrumentation Amplifier

INSULATED. Separated from other conducting surfaces by a dielectric (including air space) offering a high resistance to the passage of current. Note: When any object is said to be insulated, it is understood to be insulated for the conditions to which it is normally subjected. Otherwise, it is, uninsulated.

INSULATION. A material used to prevent the leakage of electricity from a conductor and to provide mechanical spacing or support as protection against accidental contact with the conductor.

INSULATION DISPLACEMENT CONNECTION. [IDC] A connector that cuts through the insulation of a conductor to make contact with the wire. Detailed definition of an IDC Connector. [Example IDC Connector]

INSULATION RESISTANCE. The resistance offered by an insulating material to current leakage.

INSULATOR. Material of such low conductivity that the flow of current through it can usually be neglected. A device having high electrical resistance; used for supporting or separating conductors so as to prevent undesired flow of current from the conductors to other objects.

INTEGRATED CIRCUIT. [IC] A circuit in which many elements are fabricated and interconnected by a single process (into a single chip), as opposed to a "nonintegrated" circuit in which the transistors, diodes, resistors, and other components are fabricated separately and then assembled. Elements inseparably associated and formed on or within a single substrate.

Integrated Circuit Cut-away view

 

INTEGRATOR. A circuit that takes performs an integration on the input signal. The circuit example shows an Operational Amplifier used as an integrator. For reference, Companies making Op-Amps.

Op-Amp Integrator

INTENSITY (OF SOUND). The measurement of the amplitude of sound energy. Generally synonymous with loudness.

INTERACTION SPACE. The region in an electron tube where the electrons interact with an alternating electromagnetic field.

INTERELECTRODE CAPACITANCE. The capacitance between the electrodes of an electron tube.

INTERFERENCE. Any disturbance that produces an undesirable response or degrades a signal. Any unwanted radio frequency signal.

INTERLOCK. An interlock is an automatic switch which eliminates all power from the equipment when an access door, cover or plate is removed.

INTERMEDIATE FREQUENCY. [IF] A lower frequency to which an RF echo is converted for ease of amplification.

INTERMEDIATE POWER AMPLIFIER. The amplifier between the oscillator and final power amplifier.

INTERPOLES. Small auxiliary poles, placed between main field poles, whose magnetic field opposes the armature field and cancels armature reaction. Interpoles accomplish the same thing as compensating windings.

INTERSECTION LAW. In Boolean algebra, the law which states that if one input to an AND gate is already TRUE, then the output will depend upon the state of the other inputs only.

INTRINSIC FAILURE RATE. The intrinsic failure rate is usually defined by the Failure-In-Time (FIT)—a FIT being 1 failure in 1 billion device hours of operation.

INVERSELY. Inverted or reversed in position or relationship.

INVERT. To change a physical or logical state to its opposite state.

INVERTER. A circuit with one input and one output. Its function is to invert or reverse the input. When the input is high, the output is low, and vice versa. The inverter is sometimes called a NOT circuit, since it produces the reverse of the input [7405 Inverter].

Inverter

 

INVERTING AMPLIFIER. A circuit that inverts the input signal. The operation amplifier shown will invert the incoming signal and provide gain based in the ratio of Rf and Ri.

Op Amp Inverting Circuit

IONIZATION. The process of producing ions. The electrically charged particles produced by high-energy radiation, such as light or ultraviolet rays, or by the collision of particles during thermal agitation.

IONIZATION POINT. The potential required to ionize the gas of a gas-filled tube. Sometimes called firing potential.

IONIZE. To make an atom or molecule of an element lose an electron, as by X-ray bombardment, and thus be converted into a positive ion. The free electron may attach itself to a neutral atom or molecule to form a negative ion.

IONOSPHERE. The most important region of the atmosphere extending from 31 miles to 250 miles above sea level. Contains four cloud-like layers that affect radio waves.

IONOSPHERIC STORMS. Disturbances in the earth’s magnetic field that make communications practical only at lower frequencies.

IRIS. A metal plate with an opening through which electromagnetic waves may pass. Used as an impedance-matching device in waveguides. [Waveguide Manufacturers]

ISDN. Integrated Services Digital Network. An integrated digital network in which the same time-division switches and digital transmission paths are used to establish connections for different services. [ISDN Description]

ISOLATION. The prevention of unwanted interaction or leakage between components.

ISOLATOR. A device or material used to reduce the severity of applied shock and/or vibration to a packaged item.

ISOTROPIC RADIATION. The radiation of energy equally in all directions.

J1850. An automotive bus used for diagnostics and data sharing applications in vehicles. J1850 may use either a single or differential wire approach. [J1850 Bus Description]

Jabber. A condition wherein a station transmits for a period of time longer than the maximum permissible packet length, usually due to a fault condition.

 

Phone Jack

JACK. A socket. A receptacle. Audio Jack, see graphic above

JACKET. The outermost layer of insulating material of a cable or harness. The outer sheath which protects a cable. The outer sheath or covering material,such as natural or synthetic rubber, lead sheath,steel tape, or a thermoplasitc compound, applied over a single-insulated conductor or over an assembly of insulated conductors for protection against crushing,cutting,and abrasion of the conductors and their insulation.

 

Jacketed Twisted Pair Cable

JACKETED CABLE. A bundle of insulated wires encased in a common sheath. Also refer to Cable Armor

JAN. Joint Army Navy specification.

JEDEC. Joint Electron Device Engineering Council.

JFET. Junction FET [Field Effect Transistor], a voltage controlled transistor and not current controlled. [FET Manufacturers] and vendors. An N-Channel FET is shown to the right.

JFET

JITTER. Jitter is the difference [deviation] between the expected occurrence of a signal edge and the time the edge actually occurs [phase variation]. Jitter may also be expressed as the movement of a signal edge from its ideal position in time [the expected position]. Abrupt and unwanted variations of one or more signal characteristics, such as the interval between successive pulses, the amplitude of successive cycles, or the frequency or phase of successive cycles.

JK FLIP FLOP. A style of flip flop that has a J input and a K input, and also may have a Set [S] and Reset [R] input. No change occurs when J and K are low. When the K is low the output is low and when the J is low the output goes high. When both J and K are high the output toggles.

JK FF

JTAG. Joint Test Action Group. IEEE Std 1149.1-1990, Test Access Port and Boundary-Scan Architecture (3) The JTAG interface is a serial bus with four signals: Test Clock (TCK), Test Mode Select (TMS), Test Data Input (TDI), and Test Data Output (TDO).
[JTAG Bus Description]

JOHNSON NOISE. Thermal Noise.

JOULE. The work done by a force of one newton acting through a distance of one meter.

JOYSTICK. A peripheral device used with personal computers to translate physical movement in two axis into electrical signals used by the computer. JoyStick PinOut

JUMPER. A short length of wire used to complete a circuit. A small plastic case with two female receptacles [shunt] used to short two adjacent contacts or pins, normally on 0.1 inch centers. The term may also describe a Zero Ohm Resistor. A jumper is usually used with a 2-pin header. Header Manufacturers. The graphic shows two male board headers, with jumpers or shunts installed on three pairs of the pins.

Jumper Block

JUNCTION. The connection between two or more conductors. The contact between two dissimilar metals or materials, as in a thermocouple.

JUNCTION BOX. A box with a cover that serves the purpose of joining different runs of wire or cable and provides space for the connection and branching of the enclosed conductors.

JUNCTION DIODE. A two-terminal device containing a single crystal of semi-conducting material that ranges from P-type at one terminal to N-type at the other. [Diode Manufacturers]

JUNCTION FET. JFET [Field Effect Transistor]. [FET Manufacturers]

JUNCTION TRANSISTOR. A bipolar transistor constructed from interacting PN junctions. The term is used to distinguish junction transistors from other types, such as field-effect and point-contact. Transistor Terms, [BJT Manufacturers]

Karnaugh map Example

KARNAUGH MAP. A graphical method of representing a Boolean function. A True Table displayed so that a circuit reduction can take place. [Timing Hazards]

KC. Kilocycle {the term is obsolete, use kHz}.

KEEP-ALIVE CURRENT. See KEEP-ALIVE VOLTAGE.

KEEP-ALIVE VOLTAGE. DC voltage applied to a tr gap electrode to produce a glow discharge that allows the tube to ionize faster when the transmitter fires.

KELVIN. A unit of temperature equal to 10 Celsius.

KERNEL. A module of a program that forms a logical entity or performs a unit function.

KEYBOARD. A peripheral device used with a personal computer which allows data entry. [Keyboard Manufacturers]

KEY-CLICK FILTERS. Filters used in keying systems to prevent key-click interference.

KEY CLICKS. Interference in the form of "clicks" or "thumps" caused by the sudden application or removal of power.

KEYED-OSCILLATOR TRANSMITTER. A transmitter in which one stage is used to produce the RF pulse.

KEYER. A device that changes dc pulses to mark and space modulation for teletypewriter transmissions. A synchronizer. This term is obsolete.

KEYING RELAYS. Relays used in radio transmitters where the ordinary hand key cannot accommodate the plate current without excessive arcing. [Manufacturers of Relays]

KILO. A prefix meaning one thousand, 10³.
Refer to the table of SI Units.

KINETIC ENERGY. Energy that a body possesses by virtue of its motion.

KIRCHHOFF'S LAWS. The algebraic sum of the current flowing toward any point in a circuit and the current flowing away from it is zero. The algebraic sum of the products of the current and resistance in each of the conductors in any closed path in a network is equal to the algebraic sum of the electromotive forces in the path.

KLYSTRON POWER AMPLIFIER. A multicavity microwave electron tube that uses velocity modulation.
Also see Manufacturers of RF Amplifiers

KNEE OF THE CURVE. The point of maximum curvature of a magnetization curve.

LADDER. See R2R Ladder.

LAG. The amount one wave is behind another in time; expressed in electrical degrees. Also refer to Phase [Angle].

LAMINATE. A product made by bonding two or more layers together, usually of different materials, under heat and pressure to form a single structure.

LAMINATED CORE. A core built up from thin sheets of metal insulated from each other and used in transformers.

LAN. See Local Area Network.

LANDS. Conductors or runs on Printed Circuit Boards [PCB's]. However runs are normally called Traces, while pads are referred to as lands. Also refer to a separate dictionary of terms relating to Printed Wiring Board Definitions.

PWB Lands

LAP SPLICE. A joint formed by the connecting of two or more conductors. The Lap splice is one of a number of different styles of wire splices.

 

Wire Lap Splice

LAP WINDING. An armature winding in which opposite ends of each coil are connected to adjoining segments of the commutator so that the windings overlap.

LASER. An acronym for light amplification by stimulated emission of radiation. Laser Diode Vendors.

LATCH. A circuit designed to store information. The output of a latch will change when the clock goes high but will not latch until the clock goes low. As a normal process in the design a Latch will not be permitted to passed a design review. Normally when found in an FPGA a latch will not pass a design review, Latches are considered bad design practice because they are unusable in synchronous logic circuits. List of FPGA Vendors.

NOR Latch

Latching Switch. [pulse latching], A switch that remains in a preselected position whenever the actuating voltage is removed or interrupted, and holds that preselected position until a voltage is applied to another position. A mechanical switch that remains in its present position until pushed again. Related Manufacturers;
Companies making Mechanical Switches
Companies making Semiconductor IC Switches

LAW OF MAGNETISM. Like poles repel; unlike poles attract.

LC CAPACITOR-INPUT FILTER. This is the most common type of filter. It is used in a power supply where output current is low and load current is relatively constant.

LC CHOKE-INPUT FILTER. This filter is used in power supplies where voltage regulation is important and where the output current is relatively high and subject to varying load conditions. Also see the section on Passive Filter Definitions. Related; Choke Manufacturers.

LEAD. The opposite of lag. Also a WIRE or CONNECTION.

LEAD-ACID CELL. A cell in an ordinary storage battery in which electrodes are grids of lead containing an active material consisting of certain lead oxides that change in composition during charging and discharging. The electrodes or plates are immersed in an electrolyte of diluted sulfuric acid. [Battery Manufacturers].

LEAD INDUCTANCE. The inductance of the I/O pins of an IC. The inductance of the lead wires connecting the internal components of an electron tube. Lead Inductance in IC pins can cause Ground Bounce.

LEAD SHEATH. A continuous jacket of lead molded around a single conductor or multiple conductor cable. Generally used to ensure conductors are protected from water or extensive moisture.

LEAKAGE CURRENT. The small amount of current that flows through the dielectric between the conductors of a transmission line. Leakage current is that current which flows through the equipment conductive paths to a solidly grounded source.

LEAKAGE FLUX. Magnetic flux lines produced by the primary winding that do not link the turns of the secondary winding.

LEAKAGE RESISTANCE. The electrical resistance that opposes the flow of current through the dielectric of a capacitor. The higher the leakage resistance, the slower the capacitor discharges or leaks across the dielectric.

LEAST SIGNIFICANT DIGIT (LSD). The LSD is the digit whose position within a given number expression has the least weighting power.

LEFT-HAND RULE FOR GENERATORS. A rule or procedure used to determine the direction of current flow in a generator. Also refer to Right-Hand Rule.

LEG. A current-carrying conductor intended to deliver power to or from a load normally at an electrical potential other than ground.

LEGACY. An out-of-date system or component that is still being used. Which could also be a device or component still being used after it's useful life.

LENZ'S LAW. The current induced in a circuit, caused by its motion in a magnetic field or a change in it’s magnetic flux, in such a direction as to exert a mechanical force opposing the motion or to oppose the change in flux.

LIFE CYCLE. The stages that a product goes through from conception to obsolescence, following a bell curve. There are six distinct phases of a Products Life Cycle:
Stage 1; Product Introduction.
Stage 2; Product Growth [rapid sales growth]
Stage 3; Product Maturity [sales grow stable, left of curve peak]
Stage 4. Product Saturation [sales begin to level out, right of peak]
Stage 5. Product Decline [Sales begin to decline, Obsolete]
Stage 6. Product Phase-Out Sales continue decline, Lifetime buys]
Products in either stage 5 or 6 are not recommended for new designs. Stage 6 is also called End-Of-Life.

LIGHT-EMITTING DIODE (LED). A PN-junction diode that emits visible light when it is forward biased. Depending on the material used to make the diode, the light may be red, green, or amber. More LED Terms, [LED Manufacturers].

Types of LEDs

LIGHTHOUSE TUBE. An electron tube shaped like a lighthouse that is designed to handle large amounts of power at uhf frequencies.

LIGHT-PIPE. A cylindrical tube or fiber used to pass light from one location to another. [Light Pipe Manufacturers].

LIGHT RAYS. Light waves emitting from a source in straight lines.

LIMITER. A device that prevents (limits) a waveform from exceeding a specified value.

LINE CODES. The codes used when converting a bit stream for data transmission over a communication line. Example line codes include unipolar binary signaling [0 to + DC], Polar [-DC to +DC], or AMI for Alternate Mark Inversion [bipolar] to name just a few possible line code.

LINEAR. Having an output that varies in direct proportion to the input.

LINEAR IMPEDANCE. An impedance in which a change in current through a device changes in direct proportion to the voltage applied to the device.

LINE-MAN SPLICE. A joint formed by the connecting of two or more conductors. The Lineman splice is one of a number of different styles of wire splices.

 

Lineman Wire Splice

LINE OF FORCE. A line in an electric or magnetic field that shows the direction of the force.

LINE-PULSING MODULATOR. Circuit that stores energy and forms pulses in the same circuit element, usually the pulse-forming network (pfn).

Line Regulation. The change in output voltage for a change in the input voltage of a circuit.

LIN-LOG AMPLIFIER. An amplifier in which the response is linear for weak signals and logarithmic for large signals.

LIQUID-COOLING SYSTEM. Source of cooling for high-heat producing equipments, such as microwave components, radar repeaters, and transmitters.

LISSAJOUS PATTERN. A combined, simultaneous display of the amplitude and phase relationships of two input signals on a CRT.

LITHIUM-ION BATTERY. A Battery that uses lithium metallic oxide in its positive electrode (cathode) and carbon material in its negative electrode (anode). More data on Lithium Batteries.

 

 

LOAD. A device through which an electric current flows and which changes electrical energy into another form. Power consumed by a device or circuit in performing its function. A load my be represented by a resistor and capacitor. TTL Load Circuit Schematics

Load

 

 

BNC 50 Ohm Load

LOAD Cell. A transducer which converts force into an electrical output. [Load Cell Manufacturers]

LOADING EFFECT. The effect of a load on a transmitting interface. The effect of connecting one device to another. The effect of a voltmeter upon the circuit being measured that results in an inaccurate measurement. Loading effect is minimized by using a voltmeter with an internal resistance many times higher than the resistance of the circuit being measured. Obsolete reference, as a digital voltmeter has Meg Ohms of input resistance.

LOAD ISOLATOR. A passive attenuator in which the loss in one direction is much greater than that in the opposite direction. One example is a ferrite isolator for waveguides that allows energy to travel in only one direction. [Waveguide Vendors]

Load Regulation. The change in output voltage for a change in load current, at constant chip temperature.

LOCAL ACTION. A continuation of current flow within a battery cell when there is no external load. Caused by impurities in the electrode. [Battery Producers and Data]

Local Area Network. A network which only operates or spans a small area, although there is no strict size to the operational area. A network which only operates within a particular building.

LOCAL LOOP. The voice-band telco channel between the central office [local office] and the subscriber [home].

LOGARITHMIC RECEIVER. Receiver that uses a linear logarithmic amplifier (lin-log) instead of a normal linear amplifier.

LOGICAL BLOCK ADDRESSING. [LBA] The LBA is the address that the operating system uses to read or write a block of data on the flash drive. A common scheme used for specifying the location of blocks of data stored on computer storage devices.

LOGIC. The basic principles and applications of truth tables, interconnections of off-on circuit elements, and other factors involved in mathematical computation in automatic data processing systems and other devices.

LOGIC CIRCUIT. The primary control information processor in digital equipment; made up of electronic gates and so named because their operation is described by simple equations of a specialized logic algebra.

LOGIC DIAGRAM. In computers and data processing equipment, a diagram representing the logical elements and their interconnections without necessarily expressing construction or engineering details.

 

NOT Logic Gate

LOGIC ELEMENT. The smallest building blocks that can be represented by operators in an appropriate system of symbolic logic. Typical logic elements are the AND-gate and the flip-flop, which can be represented as operators in a suitable symbolic logic. Also a device that performs the logic function.

LOGIC INSTRUCTION. Any instruction that executes a logic operation that is defined in symbolic logic, such as AND, OR, NAND, or NOR.

LOGIC OPERATION. A non-arithmetical operation in a computer, such as comparing, selecting, making references, matching, sorting, and merging, where the logical YES or NO quantities are involved.

LOGIC SWITCH. A diode matrix or other switching arrangement that is capable of directing an input signal to one of several outputs.

LOGIC SYMBOL. A symbol used to represent a logic element graphically. Also a symbol used to represent a logic operator.

LONGITUDINAL WAVES. Those waves in which the disturbance (back and forth motion) takes place in the direction of propagation. Sometimes called compression waves.

LOOP. A curved conductor that connects the ends of a coaxial cable or other transmission line and projects into a waveguide or resonant cavity for the purpose of injecting or extracting energy.

LOOSE COUPLING. Inefficient coupling of energy from one circuit to another that is desirable in some applications. Also called weak coupling.

LOSS. The signal reduction due to attenuation. The loss of a signal.

LOWER-FREQUENCY CUTOFF. The lowest frequency a circuit will pass.

LOWER SIDEBAND. All difference frequencies below that of the carrier.

LOWEST REPLACEABLE UNIT. An LRU is the lowest possible unit to be replaced within the system component during site level maintenance activities. It is a separate, installable physical package performing a single function or group of closely related functions.

LOWEST USABLE FREQUENCY. The minimum operating frequency that can be used for communications between two points.

Low Frequency. The band of frequencies from 30 kHz to 300 kHz.

Low Frequency Distortion. Frequency distortion which effects lower frequencies. Distortion

LOW-LEVEL MODULATION. Modulation produced in an earlier stage than the final.

LOW-NOISE AMPLIFIER. See PREAMPLIFIER.

LOW-PASS FILTER. A filter that passes a majority of the low frequencies on to the next circuit and rejects, or attenuates, the higher frequencies. Also called a high-frequency discriminator. Refer to the entry on Passive Filters. A via in a Printed Circuit Board [PCB] also acts as a low pass filter. Related definitions; PCB Definitions.

 

Passive RC Low Pass Filter

LOW POWER FM RADIO. [LPFM] A broadcast service that permits the licensing of 50-100 watt FM radio stations within a service radius of up to 3.5 miles and 1-10 watt FM radio stations within a service radius of 1 to 2 miles.

LUMPED CONSTANTS. The properties of inductance, capacitance, and resistance in a transmission line.

LUMPED IMPEDANCE TUNING. The insertion of an inductor or capacitor in series with an antenna to electrically lengthen or shorten the antenna.

MAGIC-T JUNCTION. A combination of H-type and E-type T-junctions style of waveguide.

MAGNET WIRE. Wire coated with an enamel insulation and used in coils, relays, transformers, motor windings, and so forth. Also refer to MIL J-W-1177; Wire, Magnet, Electrical, General Specification [cancelled in 2000, with no replacement].

MAGNETIC AMPLIFIER. An electromagnetic device that uses one or more saturable reactors to obtain a large power gain. This device is used in servosystems requiring large amounts of power to move heavy loads.

MAGNETIC FIELD. The region in which the magnetic forces created by a permanent magnet or by a current-carrying conductor or coil can be detected. The field that is produced when current flows through a conductor or antenna.

MAGNETIC INDUCTION. Generating a voltage in a circuit by the creation of relative motion between a magnetic field and the circuit. The relative motion can be the result of physical movement or the rise and fall of a magnetic field created by a changing current.

MAGNETIC LINES OF FORCE. Imaginary lines used for convenience to designate the direction in which magnetic forces are acting as a result of magnetomotive force.

MAGNETIC MICROPHONE. A microphone in which the sound waves vibrate a moving armature. The armature consists of a coil wound on the armature and located between the pole pieces of a permanent magnet. The armature is mechanically linked to the diaphragm.

MAGNETIC POLES. The section of a magnet where the flux lines are concentrated; also where they enter and leave the magnet.

MAGNETIC TRIP ELEMENT. A circuit breaker trip element that uses the increasing magnetic attraction of a coil with increased current to open the circuit.

MAGNETISM. The property possessed by certain materials by which these materials can exert mechanical force on neighboring masses of magnetic materials and can cause currents to be induced in conducting bodies moving relative to the magnetized bodies.

MAGNETRON OSCILLATOR. An electron tube that provides a high power output. Theory of operation is based on interaction of electrons with the crossed electric and magnetic fields in a resonant cavity.

MAGNITUDE COMPARATOR. A circuit that compares one value with another. In digital logic a circuit that compares two binary numbers. Also refer to IC Magnitude Comparator Chips [for schematic and part numbers].

Manchester Encoding. A method of binary encoding, see Manchester Encoding listing.

MARK. An interval during which a signal is present. Also the presence of an RF signal in cw keying. The key-closed condition (presence of data) in communications systems. A high level in an RS232 System [the opposite of a Space].

MASTER OSCILLATOR. In a transmitter, the oscillator that establishes the carrier frequency of the output.

MASTER OSCILLATOR POWER AMPLIFIER (MOPA). A transmitter in which the oscillator is isolated from the antenna by a power amplifier.

Maximum Power Dissipation. The maximum total power dissipation a component will operate at within specification.

MAXIMUM SAFE OPERATING AREA. Refer to Maximum Transistor Safe Operating Area [located on a different site page].

MAXIMUM USABLE FREQUENCY. Maximum frequency that can be used for communications between two locations for a given time of day and a given angle of incidence.

MAXTERM. A sum term containing every variable once and only once.

MECHANICAL-ROTATION FREQUENCY. The speed in revolutions per minute of armatures in electric motors and engine-driven generators; blade speed in turbines.

MECHANICAL SCANNING. The reflector, its feed source, or the entire antenna is moved in a desired pattern.

MEDIUM. The vehicle through which a wave travels from one point to the next. Air, water, and wood are examples.

MEDIUM ALTITUDE ORBIT. An orbit from 2,000 to 12,000 miles above the earth. The rotation rate of the earth and satellite are quite different, and the satellite moves quickly across the sky.

MEDIUM FREQUENCY. The band of frequencies from 300 kHz to 3 MHz.

MEGA. A prefix meaning one million, 10⁶; also MEG.

MEGOHMMETER. A meter that measures very large values of resistance; usually used to check for insulation breakdown in wires.

METAL ELECTRODE LEADLESS FACE. Surface Mount Components that have metallized terminals at each end of a cylindrical body. MELF components are designed to fit the same footprints as flat components, i.e.: 0805 (.08" x .05") and the 0603 (.06" x .03"). MELF devices may be Fuses, Resistors, or Diodes.

MELF

METALLIC ARMOR. A protective covering for wires or cables. Made as a woven wire braid, metal tape, or interlocking metal cover. Types include wire braid, steel tape and wire armor. Made from steel, copper, bronze, or aluminum. Read more Cable Armor

 

Cable Metallic Armor

METALLIC, INSULATOR. A shorted quarter-wave section of transmission line.

METALLIC RECTIFIER. Also known as a DRY-DISC RECTIFIER. A metal-to-semiconductor, large area, contact device in which a semiconductor is sandwiched between two metal plates. This asymmetrical construction permits current to flow more readily in one direction than the other.

METAL-OXIDE SEMICONDUCTOR FIELD-EFFECT TRANSISTOR. See MOSFET. [FET Manufacturers]

METER. A device used to measure a specific quantity, such as current, voltage, or frequency. A panel mount analog meter is shown. However a digital meter may be more common these days.

Meter

METASTABILITY. A circuit condition that could cause a digital logic IC to reside in an invalid state [not high or low]. Refer to the expanded Metastability Definition.

METER MOVEMENT. The part of the meter that moves to indicate some value. Obsolete reference, all equipment is digital, there are no analog meters being used, unless legacy units which have not been discarded.

METER SHUNT. A resistor placed in parallel with the meter terminals; used to provide increased range capability. Obsolete reference; a meter shunt was only required with analog meters which are in decline.

MEZZANINE. The termed used to describe a daughter card which plugs into another card [motherboard] which is then plugged into a backplane. [Mezzanine Card Manufacturers]

MHO. Unit of conductance; the reciprocal of the ohm.

MICRO. A prefix meaning one-millionth, 10^-6.

MICROCIRCUIT. A circuit having high equivalent-circuit-element density, considered as a single part composed of interconnected elements on or within a single substrate to perform an electronic-circuit function.

MICROCIRCUIT MODULE. An assembly of microcircuits or a combination of microcircuits and discrete components that perform one or more distinct functions.

MICROELECTRONICS. The solid-state concept of electronics in which compact semiconductor materials are designed to function as an entire circuit or sub-assembly rather than as circuit components [ICs].

MICROPHONE. An energy converter that changes sound energy into electrical energy. [Microphone Manufacturers].

MICROSTRIP. Traces that are adjacent to a continuous reference plane. In a Printed Circuit Board [PCB] stackup, the microstrips are on the primary and secondary layers [Top and Bottom layers]. [Related definition see Stripline]

 

Microstrip Traces

MICROWAVE REGION. The portion of the electromagnetic spectrum from 1,000 MHz to 100,000 MHz.

MIDRANGE SPEAKER. A speaker designed to reproduce sound in the ranges of 500Hz to 5kHz.

MIL. The diameter of a conductor equal to 1/1000 (.001) inch.

MIL FOOT. A unit of measurement for conductors (diameter of 1 mil, 1 foot in length).

MILITARY SPECIFICATIONS (MIL-SPEC). Technical requirements and standards adopted by the Department of Defense that must be met by vendors selling materials to DOD.

MILITARY STANDARDS (MILSTD). Standards of performance for components or equipment that must be met to be acceptable for military systems.

MILLER OSCILLATOR. A Crystal-controlled oscillator in which the crystal oscillates at its parallel resonant frequency. [Crystal Oscillator Manufacturers].

MILLI. A prefix meaning one-thousandth, 10^-3.

MINIATURE ELECTRONICS. Modules, packages, pcbs, and so forth, composed exclusively of discrete components.

MINIMUM ANNULAR RING. The minimum distance between the edge of a PCB pad and its via. Refer to this page for Minimum Annular Ring Graphics.

MINIMUM DISCERNIBLE SIGNAL (MDS). The weakest input signal that produces a usable signal at the output of a receiver. The weaker the input signal, the more sensitive the receiver.

MINORITY CARRIERS. Either electrons or holes, whichever is the less dominant carrier in a semiconductor device. In P-type semiconductors, electrons are the minority carriers; in N-type semiconductors, the holes are the minority carriers.

MINORITY CURRENT. A very small current that passes through the base-to-collector junction when this junction is reverse biased.

MINOR LOBE. The lobe in which the radiation intensity is less than that of a major lobe.

MINTERM. A product term containing every variable once and only once.

MIXER. A circuit that combines the outputs of two or more circuits into a common output. RF Mixer Manufacturers.

MLC. MultiLevel Cell: involves storing multiple bits of information on a single memory transistor. Storing two bits per memory cell instantly doubles the density in the same space and lowers the cost-per-Mbyte. MLC technology enables storage of multiple bits per memory cell by charging the polysilicon floating gate of a transistor to different levels. This technology takes advantage of the analog nature of a traditional flash cell by assigning a bit pattern to a specific voltage range.

MODE SHIFTING. In a magnetron, the inadvertent shifting from one mode to another during a pulse.

 

MODE SKIPPING. Operation in which the magnetron fires randomly, rather than firing on each successive pulse as desired.

 

MODULAR CIRCUITRY. A technique where printed circuit boards are stacked and connected together to form a module.

 

MODULAR PACKAGING. Circuit assemblies or sub-assemblies packaged to be easily removed for maintenance or repair.

 

MODULATED WAVE. A complex wave consisting of a carrier and a modulating wave that is transmitted through space.

 

AM Waveform-Modulated Wave

 

MODULATING WAVE. An information wave representing intelligence.

 

MODULATOR. A device that imposes a signal on a carrier.

 

MODULATION. The process of impressing intelligence upon a transmission medium, such as radio waves.

MODULATION FACTOR (M). An indication of relative magnitudes of the RF carrier and the modulating signal.

MODULATION INDEX. The ratio of frequency deviation to the frequency of the modulating signal.

MODULATOR. A device that produces modulation; that is, a device that varies the amplitude, frequency, or phase of an ac signal. A circuit used in servo-systems to convert a dc signal to an ac signal. The output ac signal is a sine wave at the frequency of the ac reference voltage. The amplitude of the output is directly related to the amplitude of the dc input. The circuit’s function is opposite to that of a DEMODULATOR. In radar, it produces a high-voltage pulse that turns the transmitter on and off. Also see the separate section on Definitions relating to Radar

MODULATOR SWITCHING DEVICE. Controls the on (discharge) and off (charge) time of the modulator.

MODULE. A circuit or portion of a circuit packaged as a removable unit. A separable unit in a packaging scheme displaying regularity of dimensions.

MONO JACK. A jack designed to handle one channel of sound. There are many different sizes and styles of mono jacks, one example is shown below.

 

1/8 inch Mono Phono Jack

MONOLITHIC CIRCUIT. A circuit where all elements (resistors, transistors, and so forth) associated with the circuit are fabricated in-separably within a continuous piece of material (called the substrate), usually silicon.

MONOLITHIC IC. ICs that are formed completely within a semiconductor substrate. Silicon chips.

MORSE CODE. An out-dated form of communication using 'dot' and 'dashes'. Refer to the Table of Morse Codes.

MONOSTABLE MULTIVIBRATOR. A multivibrator that has one steady state. A signal (trigger) must be applied to cause change of states. Also refer to a 555 Monostable Circuit, or Transistor Monostable Multivibrator Circuit.

 

Monostable Multivibrator

 

MOSFET. A semiconductor device that contains diffused source and drain regions on either side of a P- or N-channel area. Also contains a gate insulated from the channel area by silicon-oxide. Operates in either the depletion or the enhancement mode. FET Manufacturers

MOSFET

MOST SIGNIFICANT DIGIT (MSD). The MSD is the digit whose position within a given number expression has the greatest weighting power.

MOTOR. A machine that converts electrical energy to mechanical energy. It is activated by ac or dc voltage, depending on the design. Manufacturers of Motors

 

Electrical Motor

MOTOR LOAD. Any device driven by a motor. Typical loads are drills, saws, water pumps, rotating antennas, generators, and so forth. The speed and power capabilities of a motor must be matched to the speed and power capabilities of the motor load.

MOTOR REACTION. The force created by generator armature current that tends to oppose the normal rotation of the armature.

MOTOR STARTERS. Large resistive devices placed in series with dc motor armatures to prevent the armature from drawing excessive current until armature speed develops counter emf. The resistance is gradually removed from the circuit either automatically or manually as motor speed increases.

MOUNTING HARDWARE. Any hardware required to secure a device or component to another device in the system. Companies making mounting hardware.

 

Mounting Hardware

MOV. Metal Oxide Varistor. A resistor that changes value with applied voltage. A varistor may also be called a VDR [Voltage Dependent Resistor]. Varistors will have a negative voltage coefficient. MOV devices are used in parallel with the load. Read more on Varistor Details, or Varistor Manufacturers.

Varistor

MOVING-IRON METER MOVEMENT. Moving-Vane Meter Movement.

MOVING-VANE METER MOVEMENT. A meter movement that uses the magnetic repulsion of the like poles created in two iron vanes by current through a coil of wire; most commonly used movement for ac meters. This is an Obsolete terms, most meters being produce are digital, there is no meter movement.

MULTICONDUCTOR. More than one conductor, as in a cable. Two or more insulated conductors (solid or stranded) contained in a common covering or jacket. A Multi-conductor cable may be round [shown] or flat.

Multi-Wire Cable

MULTICOUPLERS. Couplers that patch receivers or transmitters to antennas. They also filter out harmonics and spurious responses and impedance-match the equipment.

MULTIELECTRODE TUBE. An electron tube normally classified according to its number of electrodes (the multi-electrode tube contains more than three electrodes). Vacuum Tube graphic

MULTIELEMENT ARRAY. An array that consists of one or more arrays and is classified as to directivity. Also refer to the Antenna Dictionary

MULTILOOP SERVOSYSTEM. A servo-system that contains more than one servo loop; each loop is designed to perform its own function.

 

HP Multimeter

MULTIMETER. A single meter combining the functions of an ammeter, a voltmeter, and an ohmmeter. Test Equipment Manufacturers

MULTIPATH. The multiple paths a radio wave may follow between transmitter and receiver.

MULTIPHASE. Polyphase. Having more than one phase.

MULTIPLICATION FACTOR. The number of times an input frequency is multiplied.

MULTIPLEXING. A method for simultaneous transmission of two or more signals over a common carrier wave. The T1 Interface uses multiplexing to transmit data over trunk lines. An IC circuit that transmits one of two signals from the input to the output, refer to IC Multiplexers. Multiplexing is used when driving many single channels to a remote location, but installing a separate line for each channel would be prohibitive.

MULTISPEED SYNCHRO SYSTEMS. Systems that transmit data at different transmission speeds; for example, dual-speed and tri-speed synchro systems. See synchro.

MULTI-UNIT TUBE. An electron tube containing two or more units within the same envelope. The multi-unit tube is capable of operating as a single-unit tube, or each unit can operate as a separate tube.

MULTIVIBRATOR. A form of relaxation oscillator which comprises two stages that are coupled so that the input of one is derived from the output of the other. Related topics include Transistor Multivibrator, or 555 Circuits.

MULTIVIBRATOR MODULATOR. An astable multivibrator used to provide frequency modulation. The modulating af voltage is inserted in series with the base return of the multivibrator transistors to produce the frequency modulation.

MUTUAL FLUX. The total flux in the core of a transformer that is common to both the primary and secondary windings. The flux links both windings.

MUTUAL INDUCTANCE. A circuit property existing when the relative position of two inductors causes the magnetic lines of force from one to link with the turns of the other. The symbol for mutual inductance is M. Also refer to Transformer Manufacturers.

NAND. A logic function of A and B that is true if either A or B is false. A 7400 Glue logic function.

 

True Table, NAND Gate

NAND CIRCUIT. A combination of a NOT function and an AND function in a binary circuit that has two or more inputs and one output. The output is logic 0 only if ALL inputs are logic 1; it is logic 1 if ANY input is logic 0.

NATURAL FREQUENCY. See RESONANT FREQUENCY.

NATURAL HORIZON. The line-of-sight horizon.

N-CHANNEL FET. A type of Field Effect Transistor, which is voltage controlled. Also refer to Field Effect Transistor.

NEAR END. The originating side of a circuit. The opposite of Far End [terminating side of a circuit].

NEAR SYNCHRONOUS ORBIT. An orbit in which the satellite rotates close to but not exactly at the same speed as the earth.

NEGATION. The process of inverting the value of a function or variable.

NEGATIVE ALTERNATION. That part of a sine wave that is below the reference level.

NEGATIVE CLAMPER. A circuit that clamps the upper extremity of the output waveshape to a dc potential of 0 volts.

NEGATIVE ELECTRODE. A terminal or electrode having more electrons than normal. Electrons flow out of the negative terminal of a voltage source.

NEGATIVE FEEDBACK. Feedback in which the feedback signal is out of phase with the input signal. Also called DEGENERATIVE FEEDBACK.

NEGATIVE LOGIC. The form of logic in which the more positive voltage level represents a logic 0, FALSE, or LOW and the more negative voltage represents a logic 1, TRUE, or HIGH.

NEGATIVE-RESISTANCE ELEMENT. A component having an operating region in which an increase in the applied voltage increases the resistance and produces a proportional decrease in current. Examples include tunnel diodes and silicon unijunction transistors.

NEGATIVE TEMPERATURE COEFFICIENT. A characteristic of a semiconductor material, such as silver sulfide, in which resistance to electrical current flow decreases as temperature increases.

NETWORK. A combination of electrical components. In a parallel circuit it is composed of two or more branches. Network Topologies

 

Bus Networks

A Network is any connection of two or more computers that enables them to communicate. Networks may include transmission devices, servers, cables, routers and satellites. The phone network is the total infrastructure for transmitting phone messages.

NEUTRAL. In a normal condition, hence neither positive nor negative. A neutral object has a normal number of electrons (the same number as protons). A current-carrying conductor normally tied to ground so that the electrical potential is zero.

NEUTRALIZATION. The process of counteracting or "neutralizing" the effects of inter-electrode capacitance.

NEWTON'S SECOND LAW OF MOTION. If an unbalanced outside force acts on a body, the resulting acceleration is directly proportional to the magnitude of the force, is in the direction of the force, and is inversely proportional to the mass of the body.

 

NODE. A connection point in a circuit or on a bus. The fixed minimum points of voltage or current on a standing wave or antenna.

Noise. In reference to sound, an unwanted disturbance caused by spurious waves that originate from man-made or natural sources. In radar, erratic or random deflection or intensity of the indicator sweep that tends to mask small echo signals. Thermal noise, crosstalk, leakage currents, switching transients.

Noise Bandwidth. TBD.

Noise Figure. The ratio of output noise to input noise in a receiver.

Noise Limiter. Circuit that clips the peaks of the noise spikes in a receiver.

Noise Margin. The noise margin in digital logic is the difference between the maximum output of an IC compared to the minimum input the receiving IC will accept as a logic level. Read more on Noise Margin Details

Noise Suppressor. See Noise Limiter.

NO-LOAD CONDITION. The condition that exists when an electrical source or secondary of a transformer is operated without an electrical load.

NONDEGENERATIVE PARAMETRIC AMPLIFIER. A parametric amplifier that uses a pump signal frequency that is higher than twice the frequency of the input signal.

NONDIRECTIONAL. See Omidirectional.

NON-INVERTING AMPLIFIER. An amplifier that does not invert the incoming signal at the output. The circuit example shows a Non-inverting Op Amp

Non-Inverting Op-Amp

NONLINEAR DEVICE. A device in which the output does not rise and fall in direct proportion to the input. [Nonlinear Resistors].

NONLINEAR IMPEDANCE. An impedance in which the resulting current through the device is not proportional to the applied voltage.

NONREPAIRABLE. A system or assemble that can not be repaired. Subassemblies of high reliability or relatively low cost shall be constructed as non-repairable [MIL-E-5400].

NONRESONANT LINE. A transmission fine that has no standing waves of current or voltage.

NONTRIP-FREE CIRCUIT BREAKER. A circuit breaker that can be held in the ON position during an over-current condition. Circuit Breakers

NOR. A logic function of A and B that is true if both A and B are false.

NOR GATE. An OR gate that is followed by an inverter to form a binary circuit in which the output is a logic 0 if ANY of the inputs is a logic 1 and the output is a logic 1 only if all the inputs are a logic 0.

 

NOR Gate IC Pin-Out

NORMAL. The imaginary line perpendicular to the point at which the incident wave strikes the reflecting surface. Also called the perpendicular.

NOT CIRCUIT. A binary circuit with a single output that is always the opposite of the input. Also called an Inverter Circuit.

NPN. An NPN transistor is formed by introducing a thin region of P-type material between two regions of N-type material. [Transistor Terms] / [Transistor Manufacturers]

NPN

 

NULL. A balanced condition of a circuit that represents zero output, as in Off-Set Null of an Op Amp. The minimum output amplitude of a circuit. On a polar-coordinate graph, the area that represents minimum or 0 radiation.

Off-Set Null

Null Modem. A connector adapter or cable that cross connects the Tx and Rx lines of an RS232 interface. Null Modem Adapter and Pinout.

NUMBER. A mathematical entity that may indicate quantity or amount of units. An abstract mathematical symbol for expressing a quantity. Also Hex.

NUMBER REPRESENTATION. The representation of numbers by agreed sets of symbols according to agreed rules. Also ASCII.

NUMBER SYSTEM. A number representation system. Any system for the representation of numbers. Also Base Number Conversion.

NUMERAL. A discrete representation of a number. For example, twelve, 12, XII, are three different numerals that represent the same number. A numeric word that represents a number.

NYQUIST. A theorem that determines the minimum sampling rate of a signal. See Nyquist Sampling Rate

 

OBSOLETE. Products that have been replaced by a newer or more advanced function. Products that have been discontinued or no longer being manufactured. Also refer to Part Life Cycle Definition, or Distributors of Obsolete Components

OCTAL NUMBER SYSTEM. A number system based on powers of eight. Refer to the Octal Conversion Table.

Octave. The interval between any two frequencies having a ratio of 2:1.

OFF-LINE TEST EQUIPMENT. Equipment that tests and isolates faults in modules or assemblies removed from systems.

OFF-SET NULL. A two terminal balance adjustment on an Op-Amp used to zero or null the output. A balanced condition of a circuit that represents zero output, as in Off-Set Null of an Op Amp. A related term; Null. Note the Off-set adjustment in the graphic, a 1K potentiometer connected between the two Balance terminals [BAL a and BAL B] of an Op-Amp.

Off-Set Null

OHM. The unit of electrical resistance. That value of electrical resistance through which a constant potential difference of 1 volt across the resistance will maintain a current flow of 1 ampere through the resistance.

OHMIC VALUE. Resistance in ohms. Also refer to Resistor Definitions OHMMETER. A meter used to measure resistance. Ohmmeters normally also measure the reciprocal of resistance, in Mhos. An Ohm-meter is called a multimeter when it also measures current and voltage. Refer to the Test Equipment Manufacturers page.

Ohm Meter

OHM'S LAW. The current in an electrical circuit is directly proportional to the electromotive force in the circuit. The most common form of the law is E = IR, where E is the electromotive force or voltage across the circuit, I is the current flowing in the circuit, and R is the resistance of the circuit.

OHMS PER SQUARE. The resistance of any square area of thin film resistive material as measured between two parallel sides.

OILCAN TUBE. A type of planar tube, similar to the lighthouse tube, which has cooling fins. The oilcan tube is designed to handle large amounts of power at uhf frequencies.

 

OPAQUE. Those substances that do not transmit (pass) any light rays; that is, the light rays are either absorbed or reflected.

OPEN CIRCUIT. The condition of an electrical circuit caused by the breaking of continuity of one or more conductors of the circuit; usually an undesired condition. A circuit that does not provide a complete path for the flow of current.

OPEN-ENDED LINE. A transmission fine that has a terminating impedance that is infinitely large.

OPERATIONAL AMPLIFIER (OP AMP). An amplifier designed to perform computing or transfer operations and that has the following characteristics:

(1) very high gain (2) very high input impedance (3) very low output impedance. OpAmp Manufacturers

OpAmp

OP iLINK. Another term which refers to the FireWire interface used by Sony. FireWire is also known by the term IEEE-1394

OPTICAL COUPLER. A coupler composed of an LED and a photodiode and contained in a light-conducting medium. Suitable for frequencies in the low-megahertz range. [Manufacturers of Opto-Coupler ICs]

OPTIMUM WORKING FREQUENCY. The most practical operating frequency that can be used with the least amount of problems and is roughly 85 percent of the maximum usable frequency.

 

Opto Device

OPTOELECTRONIC DEVICES. Devices that either produce or use light in their operation.

 

ORDER-WIRE CIRCUIT. A circuit between operators used for operations control and coordination.

OR GATE. A gate that performs the logic OR function. It produces an output 1 whenever any or all of its inputs is/are 1. Glue Logic

ORIGIN. The point on a graph where the vertical and horizontal axes cross each other.

ORing. When two circuits are ORed together so that if one fails the other circuit takes over, as in diode ORing.

OSCILLATOR. An oscillator is a non-rotating device that produces alternating current. The frequency is determined by the characteristics of the device. Oscillator manufacturers.

Colpitts Osc

Oscilloscope. An instrument used to plot voltage over time.

 

Oscilloscope

OUT-OF-CIRCUIT METER. A meter that is not permanently installed in a circuit. Usually portable and self-contained, these meters are used to check the operation of a circuit or to isolate troubles within a circuit.

OUTPUT END. The end of a transmission line that is opposite the source; receiving end.

OUTPUT IMPEDANCE. The impedance that is presented to the load by the transmission line and its source.

OVERCURRENT: Any current in excess of the rated current of equipment or the ampacity of a conductor. It may result from overload, short circuit, or ground fault. A current in excess of rating may be accommodated by certain equipment and conductors for a given set of conditions. Hence the rules for over-current protection are specific for particular situations.

OVERDRIVEN. When the input signal amplitude is increased to the point that the transistor goes into saturation and cutoff.

OVERLOAD: Operation of equipment in excess of normal, full load rating, or of a conductor in excess of rated ampacity which, when it persists for a sufficient length of time, would cause damage or dangerous over-heating. A fault, such as a short circuit or ground fault, is not an overload.

OVERMODULATION. A condition that exists when the peaks of the modulating signal are limited.

Overstress. A condition that occurs when a higher than normal rated voltage or current induces a hot-spot temperature beyond specifications in the junction of a semiconductor or some other device.

 

PACKET. A sequence of binary digits, including data and control signals, that is transmitted and switched as a composite whole, for data communications.

PACKET FORMAT. The structure of data, address, and control information in a packet.

PACKET SWITCHING. The process of routing and transferring data by means of addressed packets so that a channel is occupied during the transmission of the packet only, and upon completion of the transmission the channel is made available for the transfer of other traffic.

PAD. See Attenuator Pad, or PCB Pad, or Resistor Pad Schematics

PARALLAX ERROR. The error in meter readings that results when you look at a meter from some position other than directly in line with the pointer and meter face. A mirror mounted on the meter face aids in eliminating parallax error. Digital meters don't have this issue.

 

Analog Meter Display

 

PARALLEL CIRCUIT. Two or more electrical devices connected to the same pair of terminals so separate currents flow through each; electrons have more than one path to travel from the negative to the positive terminal.

Parallel RC

PARALLEL PORT. A port through which two or more data bits are passed simultaneously, such as all the bits of an 8-bit byte, and that requires as many input channels as the number of bits that are to be handled simultaneously. Centronics, IEEE-1284

PARALLEL-NEGATIVE LIMITER. A resistor and diode, connected in series with the input signal, in which the output is taken across the diode and the negative alternation is eliminated.

PARALLEL-POSITIVE LIMITER. A resistor and diode connected in series with the input signal, in which the output is taken across the diode and the positive alternation is eliminated.

PARALLEL-RESONANT CIRCUIT. A resonant circuit in which the source voltage is connected across a parallel circuit (formed by a capacitor and an inductor) to furnish a high impedance to the frequency at which the circuit is resonant. Often referred to as a tank circuit.

Oscillator

PARITY. A method of checking the accuracy of binary data. In binary-coded data, a condition that is maintained such that, in any permissible coded expression, the total number of 1s, or 0s, is always odd or always even. A binary digit appended to a group of digits or character so that there are an even number of 1s or 0s in the stream, or an odd number of 1s or 0s in the data field. Sometimes abbreviated as PAR. Related term; CRC Definition

PARITY CHECK. The process of checking the accuracy of binary data, by counting the total number of 1s, or 0s, to insure that there is always odd or always even amount depending on the parity. For reference see Manufacturers of Error correction ICs

Parity Checker IC Schematic

PARITY ERROR. A condition that occurs when the received number of 1s, or 0s do not equal the expected value. A signal output from a device that indicates the parity or number of 1s or 0s do not match the expected count. Sometimes abbreviated as PERR.

PASSIVE FILTER. A filter that does not use active components. Refer to the main entry on Passive Filters.

PASSIVE SATELLITE. A satellite that reflects radio signals back to earth.

PASSIVE SERIAL INTERFACE. A term used with programming an FPGA. In the Passive Serial [PS] interface, an external host (configuration device, embedded processor, or host PC) controls configuration of the FPGA. Also called Passive Serial Mode, or Passive Serial Scheme; where Passive Serial may be Abbreviated as PS. Related terms include Active Serial Interface, and JTAG Interface.

PATCH PANEL. A Panel used to tie different circuitry together by means of Patch Cords, usually of the same or similar type, appearing on jacks for monitoring, interconnecting, and testing purposes. Patch Panels facilitate flexibility in the use, routing or restoration of a variety of circuit types. There are a number of standard patch panels; Bantam, 1/4" Longframe , Mini WECO, XLR Patchbays, Telecom Patchbays. Also called a Patch Bay, Although sometimes a patch panel is referred to as a part of a patch bay. Refer to the graphic, right. Patch Panel Recommendations.

 

PEAK AMPLITUDE. The maximum value above or below a reference line.

PEAK CURRENT. The maximum current that flows during a complete cycle.

PEAK DETECTION. Detection that uses the amplitude of pam or the duration of pdm to charge a holding capacitor and restore the original waveform.

PEAKING COIL. An inductor used in an amplifier to provide high-frequency compensation, which extends the high-frequency response of the amplifier.

PEAK POWER. The maximum value of the transmitted pulse.

PEAK-REVERSE VOLTAGE. The peak ac voltage that a rectifier tube will withstand in the reverse direction.

PEAK-TO-PEAK. The measure of absolute magnitude of an ac waveform, measured from the greatest positive alternation to the greatest negative alternation.

Peak-to-Peak

PEAK VALUE. The maximum instantaneous value of a varying current, voltage, or power. It is equal to 1.414 times the effective value of a sine wave.

PEAK VOLTAGE. The maximum value present in a varying or alternating voltage. This value may be positive or negative.

PENTODE TUBE. A five-electrode electron tube containing a plate, a cathode, a control grid, and two grids.

PERCENT OF MODULATION. The degree of modulation defined in terms of the maximum permissible amount of modulation.

PERIGEE. The point in the orbit of a satellite closest to the earth [center].

PERIOD TIME. The time required to complete one cycle of a waveform.

PERIODIC WAVE. A waveform that undergoes a pattern of changes, returns to its original pattern, and then repeats the same pattern of changes. Examples are square waves, rectangular waves, and sawtooth waves.

PERIPHERAL DEVICE. In a data processing system, any equipment, distinct from the central processing unit, that may provide the system with additional capabilities.

PERISCOPE. An optical instrument, housed in a long tube; used to translate the observer's line of sight in a vertical direction.

PERMANENT MAGNET SPEAKER. A speaker with a permanent magnet mounted on soft iron pole pieces. Refer here for a enhanced definition and larger graphic; Definition of Permanent Magnet Speaker. [Speaker Manufacturers].

Permanent Magnet Speaker

PERMANENT MAGNET MOTOR. A PM motor uses a permanent magnet instead of armature windings. The permanent magnets are mounted [embedded] on the rotor. Permanent Magnet [PM] motors are normally small and produce little horsepower. Manufacturers of Motors

PERMEABILITY. The measure of the ability of a material to act as a path for magnetic lines of force.

PERSISTENCE. The length of time a phosphor dot glows on a CRT before disappearing. [CRT Definition]

 

PHASE. The angular relationship between two alternating currents or voltages when the voltage or current is plotted as a function of time. When the two are in phase, the angle is zero; both reach their peak simultaneously. When out of phase, one will lead or lag the other; that is, at the instant when one is at its peak, the other will not be at peak value and (depending on the phase angle) may differ in polarity as well as magnitude.

 

Sine Wave Phase Angle

PHASE ANGLE. The number of electrical degrees of lead or lag between the voltage and current waveforms in an ac circuit.

PHASE-LOCKED LOOP. [PLL] An electronic circuit that controls an oscillator so that it maintains a constant phase angle relative to a reference signal. An electronic circuit with a voltage or current-driven oscillator that is constantly adjusted to match in phase (and thus lock on) the frequency of an input signal.

PHASE MODULATION. [PM] Angle modulation in which the phase of the carrier is controlled by the modulating waveform. The amplitude of the modulating wave determines the amount of phase shift, and the frequency of the modulation determines how often the phase shifts.

PHASE NOISE. The rapid short-term, random fluctuations in the phase of a wave.

PHASE SHIFTER. A device used to change the phase relationship between two ac signals. Manufacturers of RF Phase Shifters

PHASE-SHIFT KEYING. Similar to ON-OFF cw keying in AM systems and frequency-shift keying in FM systems. Each time a mark is received, the phase is reversed. No phase reversal takes place when a space is received.

PHASE SPLITTER. A device that provides two output signals from a single input signal. The two output signals differ from each other in phase (usually by 180 degrees). The graphic shows a transistor phase splitter circuit.

Phase Splitter

PHASE VOLTAGE. The greatest root mean square (effective) difference of potential between any two legs of the circuit.

PHOSPHOR. The material used to convert the energy of electrons into visible light.

PHOTOCELL. A light-controlled variable resistor which has a light-to-dark resistance ratio of 1:1000.

PHOTODIODE. A light-controlled PN junction. Current flow increases when the PN junction is exposed to an external light source. A semiconductor diode that produces, as a result of the absorption of photons, (a) a photovoltage or (b) free carriers that support the conduction of photocurrent. Photodiodes are used for the detection of optical communication signals and for the conversion of optical power to electrical power. [Diode Manufacturers]

PHOTOELECTRIC VOLTAGE. A voltage produced by light.

PHOTOETCHING. Chemical process of removing unwanted material in producing printed circuit boards. Also refer to PCB Terms.

PHOTOTRANSISTOR. An optoelectronic device that conducts current when exposed to light. Produces more current and is much more sensitive to light than the photodiode.

 

Photo-Transistor

PHOTOVOLTAIC CELL (SOLAR CELL). A device that acts much like a battery when exposed to light and converts light energy into electrical energy.

PHYSICAL BLOCK ADDRESS. [PBA] The PBA is the fixed, physical address of a block of data on the flash drive.

 

pi. A mathematical constant whose value is the ratio of any circle's circumference to its diameter.

pi Filter. A filter circuit whose passive elements are arranged in the form of the mathematical symbol for pi.

 

Low Pass pi Filter

Pick-Up Noise. See Cross-Talk.

PICO. A prefix adopted by the National Bureau of Standards meaning 10^-12. Engineering Notation

PIEZOELECTRIC EFFECT. The effect of producing a voltage by placing a stress, either by compression, expansion, or twisting, on a crystal and, conversely, producing a stress in a crystal by applying a voltage to it.

PIEZOELECTRIC SPEAKER. A speaker that uses a piezo element as the transducer. Also refer to Piezo Speaker Manufacturers.

Pigtail. Short wires which are connected to terminals on receptacles or switches.

PIN DIODE. Acronym for Positive-Intrinsic-Negative Diode. A photodiode with a large, neutrally doped intrinsic region sandwiched between p-doped and n-doped semiconducting regions. Note: A PIN diode exhibits an increase in its electrical conductivity as a function of the intensity, wavelength, and modulation rate of the incident radiation. Diode Manufacturers Listing

Pink Noise. Noise that is inversely proportional to frequency, 1/f.

PITCH. A term used to describe the frequency of a sound heard by the human ear.

PLA. Programmable Logic Array. Refer to Programmable Logic Terms.

PLANAR TUBE. An electron tube, constructed with parallel electrodes and a ceramic envelope, that is used at uhf frequencies. It is commonly referred to as a lighthouse tube.

PLANE OF POLARIZATION. The plane (vertical or horizontal), with respect to the earth, in which the E field propagates.

PLANE WAVEFRONTS. Waves of energy that are flat, parallel planes and are perpendicular to the direction of propagation.

PLATE. One of the electrodes in a storage battery. One of the electrodes in a capacitor. The principal electrode to which the electron stream is attracted in an electron tube.

PLATE DISSIPATION. The amount of power lost as heat in the plate of a vacuum tube.

PLATE KEYING. A keying system in which the plate supply is interrupted.

PLATE MODULATOR. An electron-tube modulator in which the modulating voltage is applied to the plate circuit of the tube.

PLATE RESISTANCE. The plate voltage change divided by the resultant plate current change in a vacuum tube, all other conditions being fixed.

PLD. Acronym for Programmable Logic Device. PLDs are devices that are programmed by the OEM customer or manufacturer. A PLD IC is normally considered to be one of the more basic Programmable Logic Devices having only a few logic elements to several dozen logic elements How ever, some consider FPGA devices to also be a PLD, even with several thousand logic elements. There are two main types of PLD devices; Simple PLD [SPLD], and Complex PLD [CPLD]. The most widely know PLD is the 22V10, having 10 Flip Flop I/O programmable blocks. [PLD Dictionary], [PLD Manufacturers].

PLENUM. The air return path of a central air handling system, either ductwork or open space over a suspended ceiling. In a building, an enclosure, created by building components such as a suspended ceiling or false floor, and used for the movement of environmental air. A plenum may be used to contain communications and power cables, e.g., to reach equipment installed in open office or laboratory space. Cables installed in plenums must meet applicable environmental and fire protection regulations.

PLENUM CABLE. Cable approved by a recognized agency such as UL for installation in plenums without the need for conduit. Plenum Wire Manufacturers

 

POINT-OF-LOAD. [POL] a term used to indicate that a voltage regulator [voltage source] is place near the load that requires the voltage. On a single Printed Wiring Board [PWB], Point-of-Load means that the regulator is placed right next to the components requiring the voltage [load], as opposed to having the voltage regulator separated on the other side of the PWB [as some design practices would indicate].

In a system the term Point-of-Load means the voltage regulation [generation] is done in the same system block, at the card level and not the IC level, it just depends on the prospective. In many cases the term Point-of-Load refers to the same thing as Point-of-Source [POS], as in the regulator is placed next to the source that requires it. Related; Manufacturers of Voltage Regulators.

POINT-CONTACT DIODE. A diode in which the end of a fine wire is pressed against a semiconductor. Used as a detector or mixer over the microwave region. Manufacturers of Diodes.

POLAR RELAY. A dc relay in which the direction of movement of the armature depends on the direction of the current flow. Manufacturers of Relays.

POLARITY. The condition in an electrical circuit by which the direction of the flow of current can be determined. Usually applied to batteries and other direct voltage sources. Two opposite charges, one positive and one negative. A quality of having two opposite magnetic poles, one north and the other south.

POLE. The number of points at which current can enter a switch; for example, single pole, double pole, and three pole. The sections of a field magnet where the flux lines are concentrated; also where they enter and leave the magnet.

POLE PIECE. A piece of ferromagnetic material used to control the distribution of magnetic lines of force; that is, it concentrates the lines of force in a particular place or evenly distributes the lines of force over a wide area. The shaped magnetic material upon which the stator windings of motors and generators are mounted or wound.

POLYPHASE. A term that describes systems or units of a system that are activated by or which generate separate out-of-phase voltages. Typical polyphase systems are 2-phase and 3-phase; their voltages are 90- and 120-degrees out of phase, respectively. This term means the same as MULTIPHASE.

 

3-Phase Sine-wave

PORT. A connection point to an interface bus. A connector on a computer that receives an interconnecting cable from a peripheral device.

POSITION SENSOR. A component in a servosystem that measures position and converts the measurement into a form convenient for transmission as a feedback signal. [Sensor Manufacturers].

POSITION SERVOSYSTEM. A servo-system whose end function is to control the position of the load it is driving.

POSITIVE CLAMPER. A circuit that clamps the lower extremity of the output waveshape to a dc potential of 0 volts.

POSITIVE FEEDBACK. Feedback in which the feedback signal is in phase with the input signal. Also called Regenerative Feedback.

POSITIVE LOGIC. The form of logic in which the more positive logic level represents 1 and the more negative level represents 0. The opposite of Negative true logic.

POSITIVE TEMPERATURE COEFFICIENT. [PTC] The characteristic of a conductor in which the resistance increases as temperature increases.

POTENTIAL ENERGY. Energy caused by the position of one body with respect to another body or to the relative parts of the same body.

 

Potentiometer

POTENTIOMETER. A variable resistor, used as a volume control or a position sensor in servo-systems, having a terminal connected to each end of a resistive element and a third terminal connected to a wiper contact. The output is a voltage that is variable depending upon the position of the wiper contact. The potentiometer is commonly referred to as a variable voltage divider. It, in effect, converts mechanical information into an electrical signal. Potentiometer Manufacturers

POTS. Plain Old Telephone Service. An acronym used to describe normal residential phone service.

 

POWER. The rate of doing work or the rate of expending energy. The unit of electrical power is the watt.

POWER AMPLIFIER. An amplifier in which the output-signal power is greater than the input-signal power.

POWER-AMPLIFIER (CHAIN) TRANSMITTER. Transmitter that uses a series of power amplifiers to create a high level of power.

POWER FACTOR. The ratio of the actual power of an alternating or pulsating current, as measured by a wattmeter, to the apparent power, as indicated by ammeter and voltmeter readings. The power factor of an inductor, capacitor, or insulator is an expression of their losses.

POWER LOSS. The electrical power, supplied to a circuit, that does no work and is usually dissipated as heat. The heat loss in a conductor as current flows through it.

POWER METER. A device used to measure power. Also refer to Manufacturers of Power Meters, or Manufacturers of Optical Power Meters.

POWER PENTODE. A special purpose tube used to provide high-current gain or power amplification. Each grid wire is directly in line with the one before and after it, a fact which allows more electrons to reach the plate. Also refer to Vacuum Tube

POWER STANDING-WAVE RATIO (PSWR). The ratio of the square of the maximum and minimum voltages of a transmission line.

POWER SUPPLY. A unit that supplies electrical power to another unit. It changes ac to dc and maintains a constant voltage output within limits. [Power Supply Manufacturers]

 

PRBS. Refer to Pseudo Random Binary Sequence Definition.

PREAMPLIFIER. [Preamp] An amplifier that raises the output of a low-level source for further processing without appreciable degradation of the signal-to-noise ratio. A first stage amplifier that feeds a higher power amplifier.

PreAmp

PREFETCH. Saving data to a queue for later processing.

PRIMARY CELL. An electrochemical cell in which the chemical action eats away one of the electrodes, usually the negative electrode.

PRIMARY WINDING. The winding of a transformer connected to the electrical source. Refer to Transformer Terms

PRIME MOVER. The source of the turning force applied to the rotor of a generator. This may be an electric motor, a gasoline engine, a steam turbine, and so forth.

PRINTED CIRCUIT BOARD. [PCB] A flat, insulating surface upon which printed wiring and miniaturized components are connected in a predetermined design and attached to a common base.

Printed Circuit Board

Also refer to Printed Circuit Card Definitions. A PCB is also called Printed Wiring Board [PWB data].

PROBE COUPLER. A resonant conductor placed in a waveguide or cavity to insert or extract energy.

PRODUCT-OF-SUMS. A sum term or several sum terms logically multiplied together.

PRODUCT TERM. A single variable product term, or the logical product of several variables.

PRODUCTION LOT. A production lot shall consist of devices manufactured on the same production line(s) by means of the same production technique, materials, controls, and design.

PROGRAMMABLE DELAY LINE. A delay line with a selectable amount of delay with out the need to change taps. The example below shows a passive delay line with a fixed input and output using three control lines to change the amount of delay via a multiplexer. Related term, Delay Line. Also Delay Line vendors.

 

Programmable Delay Line

PROGRAMMABLE LOGIC ARRAY. PLA. See Programmable Logic Terms and Definitions.

PROGRAMMABLE LOGIC DEVICE. A Programmable Logic Device [PLD], or sometimes called a Programmable Logic Array [PLA] is essentially a group of uncommitted logic gates contained within an Integrated Circuit [IC]. Similar topics include; Programmable Logic Device Terms, and Programmable Logic Element Terms.

22V10 PLD IC 24-pin DIP Package

Related page, Programmable Logic Device Manufacturers.

PROPAGATION. Waves traveling through a medium.

PROTOCOL. A formal set of conventions governing the format and control of interaction among communicating functional units. [Protocol Dictionary, Protocol Acronyms]

Pseudo Random Binary Sequence. [PRBS]. Refer to this page; PRBS Definition.

PULSE. Signal characterized by a steep rise from and decay toward an initial level. Pulse Shape definitions. A flow of electrical energy of short duration.

PULSE-AMPLITUDE MODULATION (PAM). Pulse modulation in which the amplitude of the pulses is varied by the modulating signal.

PULSE-CODE MODULATION (PCM). A modulation system in which the standard values of a quantized wave are indicated by a series of coded pulses. PCM Code Definitions

PULSE-DURATION MODULATION (PDM). Pulse modulation in which the time duration of the pulses is changed by the modulating signal.

PULSE-FREQUENCY MODULATION (PFM). Pulse modulation in which the modulating voltage varies the repetition rate of a pulse train.

PULSE MODULATION. A form of modulation in which one of the characteristics of a pulse train is varied.

 

Pulse Modulation

PULSE OSCILLATOR. A sine-wave oscillator that is turned on and off at specific times. Also known as a ringing oscillator. Transistor Pulsed Oscillator Also refer to the Oscillator Manufacturers page.

PULSE-POSITION MODULATION (PPM). Pulse modulation in which the position of the pulses is varied by the modulating voltage.

PULSE-REPETITION FREQUENCY (PRF). The rate, in pulses per second, at which the pulses occur. Same as PULSE-REPETITION RATE (PRR).

PULSE-REPETITION TIME (PRT). Interval between the start of one pulse and the start of the next pulse; reciprocal of pulse-repetition frequency.

PULSE-RESPONSE. The resultant output from a circuit or system from receiving a pulsed waveform as an input. The circuit below shows a schematic of a test setup to measure the pulse response of a 2N718 transistor. The schematic provides the test points and input and output waveforms, and additional circuitry.

 

2N718 Pulse Response Test Circuit

PULSE-TIME MODULATION (PTM). Pulse modulation that varies one of the time characteristics of a pulse train (pwm, pdm, ppm, or pfm).

PULSE WIDTH. Duration of time between the leading and trailing edges of a pulse.

PULSE-WIDTH MODULATION (PWM). Pulse modulation in which the duration of the pulses is varied by the modulating voltage.

PUSH BUTTON SWITCH. A style of switch that is actuated by depressing a button. The graphic shows a Panel Mount [chassis mount] Push-Button Switch. Styles of Push-Button switches include Momentary and Latching switches. Also see Push-Button Switch Manufacturers.

Switch

PUSH-PULL AMPLIFIER. An amplifier that uses two transistors (or electron tubes) whose output signals are in phase opposition. [Transistor Manufacturers]

 

Push-pull Transistor Amplifier

 

Q. Figure of merit of efficiency of a circuit or coil. Ratio of inductive reactance to resistance in servos. Relationship between stored energy (capacitance) and rate of dissipation in certain types of electric elements, structures, or materials.

Q-BAND. A band of frequencies in the range of 36GHz to 46GHz. Note that letter designations are no longer used.

Q-METER. A device used to measure the Quality factor [Q] of a circuit. The Q-meter is not in wide spread use.

QUADRATURE. The state of being separated in phase by 90 degrees. Pertaining to the phase relationship between two periodic quantities varying with the same period, that is, with the same frequency or repetition rate, when the phase difference between them is one-quarter of their period.

QUADRATURE AMPLITUDE MODULATION. Quadrature modulation in which the two carriers are amplitude modulated. (QAM).

QUADRATURE PHASE-SHIFT KEYING. Phase-shift keying in which four different phase angles are used. In QPSK, the four angles are usually out of phase by 90 degrees. Synonyms quadriphase, quaternary phase-shift keying. quadrature phase-shift keying (QPSK).

QUALITY FACTOR: [Q]. The ratio of capacitive reactance to resistance.

QUALITY (OF SOUND). The factor that distinguishes tones of pitch and loudness.

QUANTIZE: The process of restricting a variable to a number of discrete values.

 

Sine Wave Sampling

QUANTIZED WAVE. A wave created by the arbitrary division of the entire range of amplitude (or frequency, or phase) values of an analog wave into a series of standard values. Each sample takes the standard value nearest its actual value when modulated.

QUANTIZING NOISE. Distortion introduced by quantizing the signal.

QUANTUM-MECHANICAL TUNNELING. The action of an electron crossing a PN junction because of tunnel effect.

QUARTZ. A mineral.

QUARTZ CRYSTAL. Also called a crystal. [Oscillator Manufacturers]

QUARTZ OSCILLATOR. An oscillator in which a quartz crystal is used to stabilize the frequency.

QUICK CONNECT TERMINAL. A terminal or receptacle used for rapid inter-connection. Normally a flat metal blade is used as a quick connect terminal, the receptacle slides over metal blade using pressure to make the connection. Similar; Quick Disconnect.

QUIESCENCE. The state of an amplifier with no signal applied. The operating conditions that exist in a circuit when no input signal is applied to the circuit.

QUIESCENT CURRENT. The current flowing in a circuit during a period in which a circuit element is not performing an active function in the system. The part of input current to a regulator which is not delivered to the load [less common definition].

QUIESCENT STATE. The period when a transistor, tube, or other circuit element is not performing an active function in the circuit.

 

R2R LADDER. A resistor network made by individual resistors or a resistor package.

R2R Resistor Network

RACE CONDITION. defines a condition when a device's output depends on two or more nearly simultaneous events to occur at the input. Logic Race Conditions.

RACEWAY. A channel designed expressly for holding wires, cables, or busbars, with additional functions as permitted in this subpart. Raceways may be of metal or insulating material, and the term includes rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, liquid-tight flexible metal conduit, flexible metallic tubing, flexible metal conduit, electrical metallic tubing, under-floor raceways, cellular concrete floor raceways, cellular metal floor raceways, surface raceways, wireways, and busways.
Also refer to MIL-PRF-24758, for flexible weatherproof conduit.

RACK. A vertical frame that holds or supports equipment. If the rack uses side panels, than it's called a rack enclosure. Refer to Rack Design.

RADAR. An acronym for RAdio Detecting And Ranging. Refer to the Dictionary of Radar Terms.

RADIATION FIELD. An Antenna Term.

RADIATION LOSSES. The losses that occur when magnetic lines of force about a conductor are projected into space as radiation and are not returned to the conductor as the cycle alternates.

RADIATION RESISTANCE. The resistance that if inserted in place of the antenna would consume the same amount of power as that radiated by the antenna.

RADIATION, Space. Radiation from space. Refer to the Space Radiation Dictionary.

RADIO COMMUNICATIONS. The term describing teletypewriter, voice, telegraphic, and facsimile communications.

RADIO FREQUENCY (RF). Any frequency of electromagnetic energy capable of propagation into space. The frequencies that fall between 3 kilohertz and 300 gigahertz used for radio communications.

RADIO FREQUENCY CARRIER SHIFT. The system that uses a keyer to shift a radio frequency signal above or below an assigned frequency. These shifts correspond to marks and spaces.

RADIO HORIZON. The boundary beyond the natural horizon in which radio waves cannot be propagated over the earth’s surface.

RADIO SET CONTROL UNIT. Equipment used to remotely control certain transmitter and receiver functions.

RADIO WAVES. A form of radiant energy that can neither be seen nor felt. An electromagnetic wave that is generated by a transmitter.

RADIX. Also called the base. The number of distinct symbols used in a number system. For example, since the decimal number system uses ten symbols (0, 1, 2, 3, 4, 5, 6, 7, 8, 9), the radix is 10. In the binary number system, the radix is 2 because it uses only two symbols (0, 1).
Table of Numbering Systems.

RADIX POINT. Also called BINARY POINT, OCTAL POINT, DECIMAL POINT, and so forth, depending on the number system.

 

Rail-to-Rail. An active circuit that switches within a few tenth of a volt to the supply rails [Vcc, Vdd].

RAISED-COSINE FILTER. A type of Low-Pass Filter.

RANGE. The length of a straight line between a radar transmitter and a target. [Radar Terms]

RANGE MARKER. A movable vertical pulse on an A-scope [switches to the Radar Dictionary] or a ring on a PPI scope used to measure the range of an echo or to calibrate the range scale.

RANGES. The several upper limits a meter will measure as selectable by a switch or by jacks; for example, a voltmeter may have ranges of 1 volt, 2.5 volts, 10 volts, 25 volts, and 100 volts.

RANGE STEP. On an A-scope sweep, a vertical displacement used to measure the range of an echo.

RAREFIED WAVE. A longitudinal wave that has been expanded or rarefied (made less dense) as it moves away from the source.

RATE GYRO. A gyro used to detect and measure angular rates of change.

RATIO. The value obtained when one number is divided by another. This value indicates the relative proportions of the two numbers.

RATIO DETECTOR. A detector that uses a double-tuned transformer to convert the instantaneous frequency variations of the FM input signal to instantaneous amplitude variations.

RATIO OF TRANSMITTED POWERS. The power ratio (FSK versus AM) that expresses the overall improvement of FSK transmission when compared to AM under rapid-fading and high-noise conditions.

RC CONSTANT. Time constant of a resistor-capacitor circuit; equal in seconds to the resistance value in ohms multiplied by the capacitance value in farads. [RC Voltage Graph]

RC DIFFERENTIATOR. An RC circuit in which the output is taken from the resistor.

RC FILTER. A filter used in applications where load current is low and constant, and voltage regulation is not necessary. An RC filter is comprised of some number of Resistors and Capacitors. Also refer to the entry on Passive Filters.

RC INTEGRATOR. An RC circuit in which the output is taken from the capacitor.

RC NETWORK. A circuit containing resistance and capacitance arranged in a particular manner to perform a specific function.

RC OSCILLATOR. An oscillator in which the frequency is determined by resistive and capacitive elements. [Oscillator Manufacturers]

REACTANCE. The opposition offered to the flow of an alternating current by the inductance, capacitance, or both, in any circuit.

REACTANCE AMPLIFIER. A low-noise amplifier that uses a nonlinear variable reactance as the active element instead of a variable resistance. Also called a parametric amplifier.

REACTANCE TUBE. A tube connected in parallel with the tank circuit of an oscillator. Provides a signal that will either lag or lead the signal produced by the tank.

REACTANCE-TUBE MODULATOR. An FM modulator that uses a reactance tube in parallel with the oscillator tank circuit.

 

RECEIVER. [DETECTOR]. Electronic Equipment that converts electromagnetic energy into a visible or an audible form. As in FM Receiver, AM Receiver or Radar Receiver. The electromagnetic component used in a telephone handset to convert electrical energy into sound energy.

RECEIVER SENSITIVITY. The degree to which a receiver can usefully detect a weak signal. The lower limit of useful signal input to the receiver.

RECEIVING ANTENNA. The device used to pick up the RF signal from space. Also refer to the dictionary of Antenna Terms. [Antenna Manufacturers]

RECOVERY TIME. The time required for a device to return to its previous state after a change.

Rectifier. A device [diode] used to convert ac to pulsating dc. Also refer to Half-Wave Rectifier Circuit, or Full-Wave Rectifier Circuit [Diode Manufacturers]

Rectifier Circuit. A circuit used to convert ac to pulsating dc; Half-wave [single diode], Full-wave Center Tapped Transformer [two diodes], Full-wave Bridge [four diodes], Dual Complementary Center Tapped Transformer [four diodes]

REFERENCE LINE. The position of zero displacement in a wave.

REFERENCE POINT. A point in a circuit to which all other points in the circuit are compared. Normally the reference point in a circuit is grounded, so the reference would be ground [which does not have to be zero volts].

REFLECTED WAVE. The wave that reflects back from a medium. The wave moving back to the source from the termination of a transmission line after reflection has occurred.

REFLECTION WAVES. Waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter.

REFLECTOR. The parasitic element of an array that causes maximum energy radiation in a direction toward the driven element.

REFLEX KLYSTRON. A klystron with a reflector (repeller) electrode in the place of a second resonant cavity used to redirect the velocity-modulated electrons back through the cavity that produced the modulation. A microwave oscillator that is tuned by changing the repealer voltage.

REFRACTION. The changing of direction of a wave as it leaves one medium and enters another medium of a different density.

REFRACTIVE INDEX. In a wave-transmission medium, the ratio between the phase velocity in free space and in the medium.

REGENERATIVE DETECTOR. A detector circuit that produces its own oscillations, heterodynes them with an incoming signal, and deflects them.

REGENERATIVE FEEDBACK. The process by which a portion of the output signal of an amplifying device is fed back in phase to reinforce the input. [POSITIVE FEEDBACK].

REGULATOR. The section in a power supply that maintains the output of the power supply at a constant level in spite of large changes in load current or input line voltage. There are two main styles; Switching Regulators and Linear Regulators. [Regulator Manufacturers]

 

Voltage Regulator

RELATIVE BEARING. Bearing of a target measured in a clockwise direction from "dead ahead" of a ship or plane.

 

RELAY. An electromagnetic device with one or more sets of contacts that change position by the magnetic attraction of a coil to an armature. [Relay Manufacturers]

Relay

 

 

Relay Schematic

RELIABILITY. The probability of a part performing its specified purpose for the period intended under the operating conditions encountered, expressed as failure rate. Also refer to MTBF

RELUCTANCE. A measure of the opposition that a material offers to magnetic lines of force.

REMOTE-CUTOFF TUBE. An electron tube in which the control grid wires are farther apart at the centers than at the ends. This arrangement allows the tube to amplify large signals without being driven into cutoff. [VARIABLE-MU TUBE].

REPEATER. A station that receives a signal [on one frequency] and re-transmits the signal [on another frequency] over the air. A device that regenerates the incoming signal to the original signal level, and than retransmits that signal to increase the distance the signal can travel.

 

Differential Repeater

REPELLER. [REFLECTOR]. An electrode in a reflex klystron with the primary purpose of reversing the direction of the electron beam.

REPRODUCTION. The process of converting electrical signals to sound waves. This sound is speech, music, and so on.

REPULSION. The mechanical force tending to separate bodies having like electrical charges or like magnetic polarity.

RERADIATION. The reception and retransmission of radio waves that is caused by turbulence in the troposphere.

RESIDUAL MAGNETISM. Magnetism remaining in a substance after removal of the magnetizing force.

RESISTANCE. The opposition a device or material offers to the flow of current. The effect of resistance is to raise the temperature of the material or device carrying the current. A circuit element designed to offer a predetermined resistance to current flow. A resistance of 1 ohm will allow a current of 1 ampere to flow through it when a potential of 1 volt is applied.

RESISTIVITY. The reciprocal of conductivity.

RESISTOR. The electrical component that offers resistance to the flow of current. It may be a coil of fine wire or a composition rod. [Resistor Definitions, Resistor Manufacturers]

 

Axial Leaded Resistor

RESOLUTION. The degree to which a measurement can be determined.

RESOLVER. A rotary, electromechanical device used to perform trigonometric computations by varying the magnetic couplings between its primary and secondary windings. It is generally used in circuits that solve vector problems, such as analog computers and conversion equipment. The resolver solves three different type problems: (1) Resolution - separating a vector into two mutually perpendicular components; (2) Composition - combining two components of a vector to produce a vector sum; and (3) Combination - the process of resolution and composition taking place simultaneously.

 

RESONANCE. The condition in a circuit containing inductance and capacitance in which the inductive reactance is equal and opposite to the capacitive reactance. This condition occurs at only one frequency and the circuit in that condition is said to be in resonance. Resonance of a system exists when any change in the forcing frequency results in an extremely large vibration output. Resonance of a system also occurs when the forcing frequency equals the natural frequency.

RESONANT CIRCUIT. A circuit that contains both inductance and capacitance and is resonant at one frequency (XL = XC).

RESONANT FREQUENCY. The natural frequency of an oscillator. That frequency in a given resonant circuit at which the inductive and capacitive reactance values are equal and cancel each other.

RESONANT LINE. A transmission line that has standing waves of current and voltage.

RESONATOR. A device designed to oscillate near it's own frequency. Also refer to Manufacturers of Resonators

REST FREQUENCY. The carrier frequency during the constant-amplitude portions of a phase modulation signal.

REST TIME (RT). The time when there is no pulse; nonpulse time.

RESULTANT MAGNETIC FIELD. The magnetic field produced in a synchro by the combined effects of the three stator magnetic fields. [Synchro Definition]

RETENTIVITY. The ability of a material to retain its magnetism.

REVERBERATION. The echo effect associated with a sound after it has stopped being generated. The multiple reflections of sound waves.

REVERSE AGC. The type of AGC that causes an amplifier to be driven toward cut-off.

REVERSE BIAS. An external voltage applied to a diode or semiconductor junction to reduce the flow of electrons across the junction. Also called BACK BIAS.

RF RADIATION HAZARD. A health hazard caused by exposure to electromagnetic radiation or high energy particles (ions). Also just called RADHAZ. The FCC’s limits for maximum permissible exposure [MPE] to RF emissions depend on the frequency or frequencies that a person is exposed to. Different frequencies may have different MPE levels. Radar Definitions

RF (RADIO FREQUENCY) AMPLIFIER. An amplifier designed to amplify signals with frequencies between 10 kilohertz (10 kHz) and 100,000 megahertz (100,000 MHz).

 

RF Amplifier Circuit

RF (RADIO FREQUENCY) TRANSFORMER. A transformer specially designed for use with RF (radio frequencies). An RF transformer is wound onto a tube of nonmagnetic material and has a core of either powdered iron or air.

RGK. The symbol used to express the resistance between the grid and the cathode of an electron tube.

RHEOSTAT. A variable resistor used for the purpose of adjusting the current in a circuit.

RHO. Greek letter "rho" (.). Used in the field of electricity and electronics to represent the specific resistance of a substance.

 

RIGHT HAND RULE. Indicates the relationship that exists between the direction of the current in a conductor and the direction of the magnetic field surrounding the conductor. More information on the Right Hand Rule page.

RIGID COAXIAL LINE. A coaxial line consisting of a central insulated wire (inner conductor) mounted inside of a tubular outer conductor.

RIGIDITY. The tendency of the spin axis of a gyro wheel to remain in a fixed direction in space if no force is applied to it.

RINGING. RF oscillations caused by shock excitation of a resonant circuit or cavity.

Ripple Factor. The ratio of effective value of the alternating components of the rectified voltage or current to the average value; rf = Irms/Idc.

RIPPLE FREQUENCY. The frequency of the ripple current. In a full-wave rectifier it is twice the input-line frequency. [Full-wave Rectifier Circuit and waveform]

Ripple Rejection. The ratio of rms input ripple voltage to the rms output ripple voltage.

RIPPLE VOLTAGE. The alternating component of unidirectional voltage. (This component is small compared to the direct component.)

 

Ripple Voltage Waveform

RLC CIRCUIT. An electrical circuit that has the properties of resistance, inductance, and capacitance.

RL DIFFERENTIATOR. An RL circuit in which the output is taken from the inductor.

RL INTEGRATOR. An RL circuit in which the output is taken from the resistor.

RMS. Abbreviation of root mean square. The Direct Current [DC] equivalent of an Alternating Current [AC] waveform. The voltage equivalent of an AC waveform.

 

Square Wave: I_RMS = (Tp/T)^1/2
Sawtooth: I_RMS = Ipk / (3)^1/2
Clipped Sawtooth: I_RMS = Ipk * (Tp/3T)^1/2 [even pulses missing]
Half Sine Wave: I_RMS = Ipk * (Tp/2T)^1/2 [even pulses missing]
Full Sine Wave Rectified: I_RMS = Ipk / (2)^1/2
Alternating Sine Wave: I_RMS = Ipk / (2)^1/2
Square Wave: I_RMS = Ipk
Triangle Wave: I_RMS = Ipk * (Tp/3T)^1/2

Tp = Pulse Width, T = Period, Ipk = Peak Current value

ROCKER SWITCH. A style of mechanical switch that uses a rocking action to turn the switch on and off. A rocker switch may control on or more circuits. Refer here for a listing of Rocker Switch Manufacturers.

Rocker Switch

ROOT MEAN SQUARE (RMS). The equivalent heating value of an alternating current or voltage, as compared to a direct current or voltage. It is 0.707 times the peak value of a sine wave.

ROOT-RAISED-COSINE FILTER. A type of low-pass filter.

ROTARY CAP. A spark gap, similar to a mechanically driven rotary switch, used to discharge a pulse forming network.

ROTARY SWITCH. A multicontact switch with contacts arranged in a circular or semi-circular manner. A the switch is rotated the contacts are engaged or disengaged. Rotary Switch Manufacturers.

ROTATING FIELD. The magnetic field in a multi-phase ac motor that is the result of field windings being energized by out-of-phase currents. In effect, the magnetic field is made to rotate electrically rather than mechanically. Motor Manufacturers.

ROTATING JOINT. A joint that permits one section of a transmission line or waveguide to rotate continuously with respect to another while passing energy through the joint. Also called a rotary coupler.

ROTOR. The revolving part of a rotating electrical machine. The rotor may be either the field or the armature, depending on the design of the machine. The rotating member of a synchro that consists of one or more coils of wire wound on a laminated core. Depending on the type of synchro, the rotor functions similarly to the primary or secondary winding of a transformer.

ROUTER. In data communications, a functional unit used to interconnect two or more networks. Routers operate at the network layer (layer 3) of the ISO Open Systems Interconnection. A router reads the network layer address of all packets transmitted by a network, and forwards only those addressed to another network. Manufacturers of Routers

Wireless Router

RUBIDIUM CLOCK. A clock containing a quartz oscillator stabilized by a rubidium standard. Sometimes referred to as an Atomic Clock. [Rubidium Oscillator Manufacturers]

RUBIDIUM STANDARD. A frequency standard in which a specified hyper-fine transition of electrons in rubidium-87 atoms is used to control the output frequency. A rubidium standard consists of a gas cell, which has an inherent long-term instability. This instability relegates the rubidium standard to its status as a secondary standard behind Cesium. [Rubidium Stability]

SAFETY FACTOR. The amount of a devices characteristic(s) which may be increased over and above the components normal operating rating with out causing damage to the device. In some respects a Safety Factor is the opposite of Component Derating.

Sample and Hold. A circuit that holds a sample of a signal for a short amount of time. More detail on Sample and Hold Circuits.

SAMPLE RATE. The rate at which a signal is sampled. The frequency at which an analog signal is sampled, as in a Digital-to-Analog Converter. See D/A Converter manufacturers.

SAMPLING OSCILLOSCAPE. An oscilloscope that samples the measured signal and reconstructs it as a visual representation. All Oscilloscopes produced for the last few decades are Sampling Scopes [Digital instead of Analog].

SATELLITE. A radio relay station that orbits the earth. A complete satellite communications system also includes earth stations that communicate with each other via the satellite. The satellite receives a signal transmitted by an originating earth station and retransmits that signal to the destination earth station(s). Satellites are used to transmit telephone, television and data signals originated by common carriers, broadcasters and distributors of cable TV program material.

SATELLITE ECLIPSE. An eclipse where the rays of the sun do not reach the satellite. This prevents recharging of the solar cells of the satellite and decreases the power to the transmitter.

SATELLITE-SUN CONJUNCTION. A period when the satellite and sun are close together and the noise from the sun prevents or hampers communications.

SATURABLE-CORE REACTOR. A coil in which the reactance is controlled by changing the permeability of the core.

SAW TOOTH. A waveform that appear like teeth on a saw. A Saw-Tooth waveform has a slow linear rise time and fast fall time.

SATURATION. The condition existing in any circuit in which an increase in the input signal produces no further change in the output. The operating point of a vacuum tube or transistor at which a further increase in grid or base current no longer produces an increase in plate or collector current. In a magnetic core, the condition in which a magnetic material has reached a maximum flux density and the permeability has decreased to a value of approximately 1.

SCALING FACTOR. The term used to describe the use of unequal resistors in a servo’s summing network to compensate for differences between input and output signal levels.

 

Schematic Diagram

SCHEMATIC. A diagram which shows, by means of graphic symbols, the electrical connections and functions of a specific circuit arrangement. Schematic Tools

SCHEMATIC SYMBOLS. A letter, abbreviation, or design used to represent specific characteristics or components on a schematic diagram.

SCHMITT TRIGGER. An integrated circuit which has hystersis between an upper voltage limit and lower voltage limit and does not switch until one of those limits are reached.

Schmitt

SCHOTTKY DIODE. A junction diode with the device junction formed between the semiconductor and a metal contact rather than between dissimilar semiconductor materials. Diode Manufacturers

SCR. Refer to Silicon Controlled Rectifier. SCR Vendors.

SCREEN GRID. A grid placed between a control grid and the plate and usually maintained at a fixed positive potential. Used with Vacuum tubes or CRTs.

SCREENING. Process of applying nonconductive or semiconductive materials to a substrate to form thick film components.

SECONDARY. The output coil of a transformer. Refer to Transformer Terms. Manufacturers of Transformers.

SECONDARY CELL. A cell that can be recharged by a current being passed through the cell in a direction opposite to the discharge current. Battery Manufacturers

SECONDARY EMISSION. The liberation of electrons from an element, other than the cathode, as a result of being struck by other high-velocity electrons.

SECONDARY LOOP. In a cooling system, the loop that transfers the heat from the heat source, such as electronic equipment, to the primary loop; usually distilled water.

SECOND DETECTOR (DEMODULATOR). The part of the receiver that separates the audio or video component from the modulated intermediate frequency.

 

SELECTIVITY. The ability of a receiver to select the desired signal and reject unwanted signals.

SELENIUM. A chemical element with light-sensitive properties that makes it useful as a semiconductor material in metallic rectifiers.

SELF-BIAS. In a transistor circuit, the voltage developed across a resistor connected between the collector and base [Rb in the schematic]. In a vacuum tube circuit, the voltage developed by the flow of current through a resistor in the grid or cathode leads.

Self-Bias

SELF-EXCITED GENERATORS. DC generators in which the generator output is fed to the field to produce field excitation.

SELF-EXCITED METER. A term used to describe meters that operate from their own power sources.

SELF-INDUCTION. The production of a counter-electromotive force in a conductor when its own magnetic field collapses or expands with a change in current in the conductor. The phenomenon caused by the expanding and collapsing fields of an electron that encircle other electrons and retard the movement of the encircled electrons.

SENSE LINES. One or more lines running from a power supply to the load. The Sense Lines differ from the normal power supply output lines in that they supply no current. Sense Lines are used to read the voltage level at the load and adjust the output of the supply as required to maintain the correct voltage level. Sense Lines provide an accurate voltage reading because the lines do no incur a voltage drop due to the low current drain. Generally it is recommended to interconnect sense lines directly at the female connector to their respective power output terminals since sense lines in general may cause trouble.

SENSITIVITY. For an ammeter, the amount of current that will cause full-scale deflection of the meter. For a voltmeter, the ratio of the voltmeter resistance divided by the full-scale reading of the meter; expressed in ohms per volt. The ability of a receiver to reproduce very weak signals. The greater the receiver sensitivity, the weaker the signal that can be reproduced. Efficiency of a microphone. Describes microphone power delivered to a matched-impedance load as compared to the sound level being converted. Usually expressed in terms of the electrical power level.

SENSOR. A device, usually electronic, that extends man's natural senses by means of emitted or reflected energy. The energy may be nuclear, electromagnetic including the visible and invisible portions of the spectrum, chemical, biological, thermal, or mechanical. Related page; Sensor Manufacturers.

SERIES CIRCUIT. An arrangement where electrical devices are connected so that the total current must flow through all the devices; electrons have one path to travel from the negative terminal to the positive terminal.

SERIES-CONNECTED DUPLEXER. A configuration in which the tr spark gap is connected in series in one leg of the transmission line one-half wavelength away from the T-junction.

SERIES-DIODE DETECTOR. The semiconductor diode in series with the input voltage and the load impedance. Sometimes called a Voltage-Diode Detector.

SERIES-FED OSCILLATOR. An oscillator in which dc power is supplied to the amplifier through the tank circuit or a portion of the tank circuit.

SERIES LIMITER. A diode connected in series with the output, in which the output is taken across the resistor. Either the positive or negative alternation of the input wave is eliminated.

SERIES-NEGATIVE LIMITER. A diode connected in series with the output, in which the output is taken across the resistor. It eliminates the negative alternation of the input wave.

SERIES-PARALLEL CIRCUIT. A circuit that consists of both series and parallel networks.

 

SERIES PEAKING. A technique used to improve high-frequency response in which a peaking coil is placed in series with the output signal path.

SERIES-POSITIVE LIMITER. A diode connected in series with the output, in which the output is taken across a resistor. It eliminates the positive alternation of the input wave.

SERIES-RESONANT CIRCUIT. A resonant circuit in which the source voltage is connected in series with a capacitor and an inductor (also in series) to furnish a low impedance at the frequency at which the circuit is resonant.

SERIES VOLTAGE REGULATOR. A regulator with a regulating device that is in series with the load resistance. Voltage Regulator Manufacturers

SERIES-WOUND MOTORS AND GENERATORS. Machines in which the armature and field windings are connected in series with each other.

SERVER. A computer attached to a network that provides a location for the shared storage of computer files. A computer or device that manages network resources. There are a number of types of servers; for instance, a network server manages network traffic.

SERVO. A short notation for Servomotor.

SERVOAMPLIFIER. Either ac or dc amplifiers used in servosystems to build up signal strength. These amplifiers usually have relatively flat gain versus frequency response, minimum phase shift, low output impedance, and low noise level.

SERVOMOTOR. An ac or dc motor used in servo-systems to move a load to a desired position or at a desired speed. The ac motor is usually used to drive light loads at a constant speed, while the dc motor is used to drive heavy loads at varying speeds. Another name for a Error Reducer. Motor Manufacturers

SERVOSYSTEM. An automatic feedback control system that compares a required condition (desired value, position, and so forth) with an actual condition and uses the difference to drive a control device to achieve the required condition.

SHAPING CIRCUIT. A circuit that alters the shapes of input waveforms.

SHARP-CUTOFF TUBE. The opposite of a remote-cutoff tube. An electron tube that has evenly spaced grid wires. The amplification of the sharp-cutoff tube is limited by the bias voltage and tube characteristics.

SHELF LIFE. The period of time that a cell or battery may be stored and still be useful. Shelf Life applies to ICs, capacitors and other electronic devices. [Related topics; Capacitor Aging]

SHIELDED CABLE. Cable surrounded by a metallic covering intended to minimize the effects of electrical crosstalk interference or signal radiation.

SHIELDED PAIR. A line consisting of parallel conductors separated from each other and surrounded by a solid dielectric.

 

Shielded Twisted Pair Cable

SHIELDED TWISTED PAIR. [STP] A cable consisting of parallel conductors separated from each other and surrounded by a solid dielectric, and twisted together. The number of times the two conductors are twisted together per inch varies with different cables. Shielded Twisted Pair cables are much more common than simple Shielded Pair cables. The diagram above shows a Shielded Twisted Pair cable. Refer to the main listing on Twisted Pair cable.

SHIELDING. A metallic covering used to prevent magnetic or electromagnetic fields from affecting an object. Technique designed to minimize internal and external interference. Shielding is required in electrical and electronic equipments to prevent the equipment from propagating interference and to protect the equipment from the effects of interference propagated by other electrical and electronic devices. [EMI Shielding Techniques].

SHOCK RATING. Measurement (in Gs) indicating how much shock a device or component can sustain before damage could occur. Also refer to MIL-STD-901 for shock testing.

SHORT CIRCUIT. An unintentional current path between two components in a circuit or between a component and ground; usually caused by a circuit malfunction.

SHORT-CIRCUITED LINE. A transmission line that has a terminating impedance equal to 0. Also refer to Continuity Testers [vendor listing].

Shot Noise. Noise generated by a charge crossing a potential barrier, common in transistors and Op amps at higher frequencies.

 

SHUNT. A small plastic female Jumper [picture to right]. A shunt is normally a two terminal component on 0.1 inch centers which is fitted over a dual-row headed with the same dimensions.

2-Terminal Shunt

In some cases a Shunt could be a wire, in other cases a shunt may be a resistor. A resistive device placed in parallel with another component. Appreciable current may flow through it and an appreciable voltage may exist across it. Also see Resistor Shunt [Dictionary of Resistor Terms].

SHUNT-DIODE DETECTOR. A diode detector in which the diode is in parallel with the input voltage and the load impedance. Also known as a current detector because it operates with smaller input levels.

SHUNT-FED OSCILLATOR. An oscillator that receives its dc power for the transistor or tube through a path both separate from and parallel to the tank circuit.

SHUNT PEAKING. A technique used to improve high-frequency response in which a peaking coil is placed in parallel (shunt) with the output signal path.

SHUNT RESISTOR. A resistor in parallel with another component or device. In an ammeter, shunt resistors are used to provide multiple ranges.

SHUNT VOLTAGE REGULATOR. A regulator whose regulating device is in parallel with the load resistance. 3-Terminal Shunt Regulator shown.

SHUNT-WOUND MOTORS AND GENERATORS. Machines in which the armature and field windings are connected in parallel (shunt) with each other.

SIEMENS. The preferred term for MHO.

SIGNAL. A general term used to describe any ac or dc of interest in a circuit; for example, input signal.

SIGNAL DISTORTION. Any unwanted change to the signal.

SIGNIFICANT SIDEBANDS. Those side-bands with significantly large amplitude.

SILENT DATA CORRUPTION. [SDC] Data corruption that occurs in a computing system without any error being logged, no CRC error, or Parity error or any other indication that an error occurred. SDC may occur from any cause.

SILICON. A metallic element which, in its pure state, is used as a semiconductor.

SILICON-CONTROLLED RECTIFIER. [SCR] A semiconductor device that functions as an electrically controlled switch. A 3-terminal semiconductor device consisting of a Gate, Anode and, Cathode. SCR Vendors.

Simultaneous Switching. The condition when more than one outputs of an IC are switching at the same time. Also refer to Ground Bounce

SINE WAVE. The curve traced by the projection on a uniform time scale of the end of a rotating arm, or vector. Also known as a sinusoidal wave. The basic synchronous alternating waveform for all complex waveforms.

SINGLE-ENDED MIXER. See Unbalanced Crystal Mixer. Manufacturers of RF Mixers

SINGLE LINE DIAGRAM. A diagram which shows, by means of single lines and graphic symbols, the course of an electric circuit or system of circuits and the component devices or parts used therein.

SINK CURRENT. An integrated circuit sinks current when current is flowing from a load [another device] into the circuits output. This is considered negative current to the IC. FanOut is a related term.

SKEW. The time delay between two related signals. See Timing Skew.

SKIN EFFECT. The tendency for alternating current to concentrate in the surface layer of a conductor. The effect increases with frequency and serves to increase the effective resistance of the conductor.

SKIP DISTANCE. The distance from a transmitter to the point where the sky wave is first returned to earth. Refer to Antenna definitions [in a separate dictionary].

SKIP ZONE. A zone of silence between the point where the ground wave becomes too weak for reception and the sky wave is first returned to earth.

 

SLEW RATE. The rate of change of the out put of an integrated circuit, as it switches. A separate page covers this topic in greater detail; Slew Rate.

SLIP. The difference between rotor speed and synchronous speed in an ac induction motor.

SLIP RINGS. Contacts that are mounted on the shaft of a motor or generator to which the rotor windings are connected and against which the brushes ride. Devices for making electric connections between stationary and rotating contacts.

SLOPE DETECTOR. A tank circuit tuned to a frequency, either slightly above or below an FM carrier frequency, that is used to detect intelligence.

SLOT. Narrow opening in a waveguide wall used to couple energy in or out of the waveguide. Also called an aperture or a window.

SMA. A style of threaded coaxial connector. SMA Definition [located in the Radar dictionary]

SNAP-ACTING. Changing position quickly with the aid of a spring.

SOFT-ERROR. A data error which can be corrected by attempting to re-read or re-writing the data.

SOLDER-CUP. A type of connector pin with a cup on one end to accept a wire and solder as a connection point. [graphic lower right]

SOLDER HOOK. A type of terminal shaped like a hook. The component may have any number of hook shaped terminals.

Solder Cup Pin

SOLDER SLEEVE. A heat-shrinkable solder termination device with meltable sealing preforms at ends.

SOLENOID. An electro-magnetic device that changes electrical energy into mechanical motion; based upon the attraction of a movable iron plunger to the core of an electromagnet.

SOLID. One of the three states of matter; it has definite volume and shape.

SOLID-STATE DEVICE. An electronic device that operates by the movement of elections within a solid piece of semiconductor material.

SOLID-STATE LIGHTING. SSL is an umbrella term encompassing both light-emitting diodes (LEDs) and organic light emitting diodes (OLEDs). [read more about SSL].

SONIC. Pertaining to sounds capable of being heard by the human ear.

SOURCE. The object that produces the waves or disturbance. The name given to them end of a two-wire transmission line that is connected to a source. The device which furnishes the electrical energy used by a load.

SOURCE CURRENT. An integrated circuit sources current when current is flowing from the IC into another device [Load]. Source-ing current is considered to be positive current flow from the ICs prospective. Source current is the opposite to Sink Current.

SPACE. Absence of an RF signal in cw keying. Key-open condition or lack of data in communications systems. Also a period of no signal.

SPACE CHARGE. An electrical charge distributed throughout a volume or space.

SPACE DIVERSITY. Reception of radio waves by two or more antennas spaced some distance apart.

SPACE WAVE. Radio waves that travel directly from the transmitter to the receiver and remain in the troposphere.

SPARK-GAP MODULATOR. A modulator that consists of a circuit for storing energy, a circuit for rapidly discharging the storage circuit (spark gap), a pulse transformer, and a power source.

SPEAKER. A device that radiates acoustic energy into the air. More detail on Speaker Types. The graphic shows a 5.1 speaker system.

Speaker System

SPECIFIC GRAVITY. The ratio between the density of a substance and that of pure water at a given temperature.

SPECIFIC RESISTANCE. The resistance measured in ohms of a unit volume of a substance to the flow of electric current. (The unit volume used is generally the circular mil-foot.)

SPECTRUM. The entire range of electromagnetic waves arranged in order of their frequencies. The range of frequencies considered in a system. The range of electromagnetic radio frequencies used in the transmission of sound, data and television [TV].

SPECTRUM ANALYSIS. The display of electromagnetic energy arranged according to wavelength or frequency.

 

Spectrum Analyzer

SPECTRUM ANALYZER. A test instrument that provides a visual display of the frequency distribution of an RF signal such as a transmitter output. Refer here for Manufacturers of Spectrum Analyzers.

Speed-up Capacitor. A capacitor in parallel with another component, which acts as a 'short'. Also refer to the dictionary of Capacitor Terms.

 

SPIKE. A spike is a transient of duration less than 10 percent of pulse width during which the amplitude appreciably exceeds the average amplitude of the pulse.

SPINDLE MOTOR. A type of motor used with disk drives to rotate the platter.

SPIN VECTOR. In a gyro, a vector representing the angular velocity of the gyro rotor. The spin vector lies along the spin axis of the rotor.

SPHERICAL WAVEFRONTS. Waves of energy that spread out in concentric circles.

Spike. A spike is a transient of very short duration, during which the amplitude appreciably exceeds the average amplitude of the pulse.

SPLATTER. Unwanted sideband frequencies that are generated from over-modulation.

SPLICE. A joint formed by the connecting of two or more conductors. There are a number of different styles of wire splices.

 

Wire Splice

SPORADIC E LAYER. Irregular, cloud-like patches of unusually high ionization. Often forms at heights near the normal E layer.

SPREADER. Insulator used with transmission lines and antennas to keep the parallel wires separated.

SPROCKET TUNER. A mechanical tuning device for magnetron tubes that changes the frequency of the cavities by changing the inductance. Also called a CROWN-OF-THORNS TUNER.

SQUARE MIL. The area of a square, the sides of which are each equal to 1 mil. One square mil is equal to 1.2732 circular mils.

SQUARE WAVE. A rectangular shaped periodic waveform which switches between to fixed values.

Square Wave

SQUELCH. A circuit that cuts off the output of a receiver when there is no input.

SQUIRREL-CAGE WINDINGS. A type of rotor winding in which heavy conductors are imbedded in the rotor body. The conductors are shorted together at the ends by continuous rings. It is widely applied in ac induction motors. Physically, it appears as a rotating squirrel-cage, thus the name.

SR LATCH. Set-Reset Latch. A style of latch where one line sets the latch and the other line resets the latch. Examples include; 74279, 4043, 4044 logic ICs. The SR latch in the graphic uses NOR gates.

SR Latch Circuit

STABILITY. An inherent characteristic of an oscillator that determines how well it can produce the same frequency over a given time interval. In a magnetron, the ability to maintain normal operating characteristics.

STAGE. One of a series of circuits within a single device or circuit; for example, first stage of amplification.

STAGGER TUNING. A method of klystron tuning in which the resonant cavities are tuned to slightly different frequencies to increase the bandwidth of the amplifier.

STANDING WAVE. The distribution of voltage and current, formed by the incident and reflected waves, that has minimum and maximum points on a resultant wave that appear to stand still.

STANDING-WAVE RATIO (SWR). The ratio of the maximum (voltage, current) to the minimum (voltage, current) points of a transmission line. Indicates the impedance matching quality of the termination of the line.

STATIC. A fixed non-varying condition, without change, without motion.

STATIC ELECTRICITY. Stationary electricity that is in the form of a charge. The accumulated electric charge on an object. Also refer to the dictionary of ESD Terms

STATOR. The stationary part of a rotating electrical machine. The stator may be either the field or the armature, depending on the design of the machine. The stationary member of a synchro that consists of a cylindrical structure of slotted laminations on which three Y-connected coils are wound with their axes 120 degrees apart. Depending on the type of synchro, the stator’s functions are similar to the primary or secondary windings of a transformer.

STATUTE MILE. 5,280 feet.

 

STEPPER MOTOR. A motor that operates in discrete angular motions of uniform magnitude. [Stepper Motor Manufacturers]

STEP-TRANSMISSION SYSTEM. A data transmission system that operates on direct current. It consists of a step transmitter (rotary switch) and a step motor interconnected to transmit data (information) between remote locations.

STEP-UP TRANSFORMER. A transformer that Steps up the secondary voltage compared to the primary voltage. A transformer with a higher secondary voltage. Also refer to Transformers Definitions, or Manufacturers producing Step Up Transformers.

STEREO. Short for Stereophonic, basically sound that is reproduce in two or more channels.

STEREO JACK. A jack designed to handles two channels. There are many different sizes and styles of stereo jacks, one example. Audio Connectors

1/4 inch Stereo Phono Jack

STICKOFF VOLTAGE. A low voltage used in multi-speed synchro-systems to prevent false synchronizations. refer to synchro.

STORAGE TEMPERATURE. The minimum or maximum temperature a device may be safely stored while not in use. Storage temperature is normally higher or lower than a devices operating temperature range. Storage temperature is a temperature at which the device may be stored without any power being applied.

Strain Relief. A connector device that prevents the disturbance of the contact and cable terminations. Strain Relief vendors.

STRANDED CONDUCTOR. A conductor composed of a group of wires. The wires in a stranded conductor are usually twisted together and not insulated from each other.

STRANDS. Fine metallic filaments twisted together to form a single wire.

STRATOSPHERE. Located between the troposphere and the ionosphere; it has little effect on radio waves.

STRATUM CLOCK. A clock in a telecommunications system or network that is assigned a number that indicates its quality and position in the timing hierarchy. The highest quality clocks, called stratum 1 clocks, have a frequency offset of 1 x 10-11 or less, which means that they can keep time to within about one microsecond per day. stratum clocks specifications; ANSI standards T1.101-1999 and T1.105.09-1997.

STRIPLINE. Traces routed in inner layers and have two reference planes. In a Printed Circuit Board [PCB] stack-up, striplines are on internal layers. Related definition Microstrip

 

Stripline Traces

STROBOSCOPE. An instrument that allows viewing of rotating or reciprocating objects by producing the optical effect of a slowing down or stopping motion.

STUB. Short section of a transmission line used to match the impedance of a transmission line to an antenna. Can also be used to produce desired phase relationships between connected elements of an antenna. Related pages Terminating Traces, Dictionary of PCB Terms.

SUBASSEMBLY. Consists of two or more parts that form a portion of an assembly or a unit.

SUBHARMONIC. An exact submultiple of the fundamental frequency. Even sub-harmonics are one-half, one-quarter, and so on. Odd subharmonics are one-third, one-fifth, and so on of the fundamental frequency.

SUBSTRATE. Mounting surface for integrated circuits. May be semiconductor or insulator material depending on type of IC.

SUDDEN IONOSPHERIC DISTURBANCE. An irregular ionospheric disturbance that can totally blank out hf radio communications.

Summing Amplifier. A circuit that performs both a summing function and amplification. Using the Summing Op-Amp circuit below; the summing circuit may also be a Summing Amplifier depending on the value of Rf and Rn [the input resistors].

Summing Circuit. See Summing Network.

Summing Network. A combination of two or more parallel resistors used in servosystems as an error detector. The output of the network is the algebraic sum of the inputs. The circuit example shows an Op Amp summing circuit.

Op-Amp Summing Circuit

SUM-OF-PRODUCTS. A product term of several product terms logically added together.

SUM TERM. A single term or the sum of several variables.

SUPERHETERODYNE RECEIVER. A type of receiver that uses a mixer to convert the RF echo to an IF signal for amplification.

SUPERHIGH FREQUENCY. The band of frequencies from 3 gigahertz to 30 gigahertz.

Super-Multiplexing. A method of increasing channel capacity by multiplexing multi-levels.

SUPPRESSION. The process of eliminating an undesired portion of a signal.

SURFACE WAVE. Radio waves that travel along the contours of the earth, thereby being highly attenuated.

SURGE. The sudden change in voltage or current in a circuit.

SWAMPING RESISTOR. A resistor used to limit current. Detailed definition of Swamping Resistor.

SWITCH. A device used to connect, disconnect, or change the connections in an electrical circuit. A device used to open or close a circuit. [Switch Manufacturers]. A Toggle switch is shown as an example.

Switch

Switch Bounce. The mechanical chatter or oscillation of the switch contacts as they attempt to move from the open and closed position [or closed to open]. There is no way to stop a switch from bouncing, it's due to the design of the switch. However a Switch Debouncer circuit may be designed so that the bounce [on-off oscillations] are not seen by the connecting circuit ~ see Switch Debounce.

SWITCH DEBOUNCE. Refer to the Switch Debounce Definition.

SWITCHING REGULATOR. A regulator that converts the incoming DC to a switched voltage applied to a transistor or FET with a feed-back path to keep the output voltage constant. Read more on Switching Regulators.

SWITCHING TIME. The interval of time between when the input of a device switches states and the output of that device switches state [or referenced at defined levels].

SWR METER. A device that measures the Standing Wave Ratio on a line.

 

SYMMETRICAL MULTIVIBRATOR. A circuit that generates square waves. Also refer to Definitions of Transistor Multivibrator Circuits.

SYNCHRO. A small motor-like analog device that operates like a variable transformer and is used primarily for the rapid and accurate transmission of data among equipments and stations. More on Synchro's.

 

 

Synchro Schematic

SYNCHRO CAPACITOR. A unit containing three delta-connected capacitors. The synchro capacitor is used in synchro systems to increase the system’s accuracy by cancelling or reducing the phase shift introduced by synchro inductance. Also refer to Definitions of Capacitor Terms.

SYNCHRO SYSTEM. Two or more synchros interconnected electrically. The system is used to transmit data among equipments and stations.

SYNCHRO TESTER. A synchro receiver with a calibrated dial. This receiver is used primarily for locating defective synchros. It can also be used for zeroing synchros.

SYNCHRONIZER. A clocking circuit that supplies timing pulses to another circuit. A circuit that supplies timing signals to other radar components.

SYNCHRONIZING NETWORK. A circuit, also called a crossover or switching network, used in servo-systems to sense how far the load is from the point of correspondence; it then functions to switch the appropriate signal into control.

SYNCHRONOUS. One or more circuits operating under the same clock relationship.

SYNCHRONOUS MOTOR. An ac motor whose rotor is activated by dc. It is characterized by constant speed and requires squirrel-cage windings or some other method to be self-starting. [Motor Manufacturers]

SYNCHRONOUS ORBIT. An orbit in which the satellite moves or rotates at the same speed as the earth.

SYNCHRONOUS SPEED. The speed at which the rotating field in an ac motor revolves. This speed is a function of the number of poles in the field and the frequency of the applied voltage.

SYNCHRONOUS TUNING. In a klystron amplifier, a method of tuning that tunes all the resonant cavities to the same frequency. High gain is achieved, but the bandwidth is narrow.

SYNTAX. The make up of expressions or the rules that govern a language.

SYNTHESIZER. A device that can generate a number of controlled frequencies.

SYSTEM. A combination of sets, units, assemblies, sub-assemblies, and parts joined together to form a specific operational function or several functions.

 

TACHOMETER. A small ac or dc generator, sometimes referred to as a rate generator, that converts its shaft speed into an electrical output. The tachometer is frequently used in servo-systems to sense the velocity of a load. An instrument that measures the rate at which a shaft is turning.

TANK CIRCUIT. A tuned circuit used to temporarily store energy. Also referred to as a parallel-resonant circuit. The components are placed in parallel in a Tank circuit. Also refer to Frequency Doubler using a tank circuit.

TAPPED DELAY LINE. A delay line with multiple tapped outputs so the amount of delay may be selected by choosing another tap or point on the delay line. To change the delay on this type of circuit the output needs to be taken from a different output pin. Related terms, Delay Line, Programmable Delay Line.

 

Tapped Delay Line

TAPPED RESISTOR. A wire-wound, fixed resistor having one or more additional terminals along its length, generally for voltage-divider applications. Potentiometer Manufacturers.

Tee CONNECTOR. A style of connector shaped like a 'T'. The connectors may be any gender in any combination. A BNC style Tee is shown to the right, but a Tee connector could be almost any style. More Tee Connector Graphics [BNC, TNC]. Manufacturers of Coax Connectors

BNC Tee Connector

TELECOMMUNICATIONS. The transmission, emission, or reception of signs, signals, writings, images, or sounds. This is done by visual, oral, wire, radio, or other means. The term Telecommunications may also be abbreviated as Telcom.

TEMPERATURE COEFFICIENT. The ratio of the change in a parameter to the change in temperature. The amount of change of resistance in a material per unit change in temperature.

TEMPERATURE INVERSION. The condition in which warm air is formed above a layer of cool air that is near the earth’s surface.

TEMPEST. A term normally used to describe compromising emanations. These emanations are unintentionally radiated signals that could disclose classified information.

TENTED VIA. A via with dry film solder mask which completely covers both the via pad and its plated-through hole [PTH]. In the example to the right, the via pad and PTH is yellow while the solder mask is off-set in color. Also refer to the definition of Via. Definitions of PWB Terms

Tented Via

TENSILE STRENGTH. The greatest stress a substance can withstand along its length without tearing apart.

TERMINAL. An electrical connection.

TERMINAL BOARD. Also called a terminal strip. An insulating base or slab equipped with terminals for connecting wiring.

TERMINAL DIAGRAM. A diagram of a switch, relay, terminal board, or other component showing the connections to the equipment.

TERMINAL LUG. A device attached to a conductor to permit connection to a terminal. [Terminal Lug Definition]

Tertiary Winding. A Tertiary winding is a third winding on a transformer, having the same turns ratio as the second winding. A Transistor Blocking Oscillator using a Tertiary Winding. The word Tertiary means third.

TEST EQUIPMENT. A general term applied to devices used to test electrical and electronic circuits. [Manufacturers of Test Equipment]

TEST POINTS. Locations in equipment or devices that are accessible to the technician’s test probes where operating voltages or signals can be monitored. In this example, a Header, but a test point could just be a via or pad on the Printed Wiring Board [PWB].

Test Points

TETRODE TUBE. A four-electrode electron tube containing a plate, a cathode, a control grid, and a screen grid. [Vacuum Tube]

T FLIP FLOP. A style of flip flop that toggles on a clock edge, with the input high and does not change when the T input is low. A T flip flop can be produced by using a JK flip flop.

T Flip Flop

Thermal Impedance. The resistance to heat transfer. Also refer to 2N3439 Thermal Impedance Graph and definition.

Thermal Inertia. The capacity of a soldering iron to generate and maintain a satisfactory soldering temperature while giving up heat to the material being soldered.

Thermal-Magnetic Trip Element. A single circuit breaker trip element that combines the action of a thermal and a magnetic trip element.

Thermal Noise. The white noise generated by a passive component.

Thermal Resistance. A figure of merit for heat transfer [temperature drop divided by power dissipation] between two points in a conductive system.
(T1 - T2)/Pd [in C/W]. The temperature rise, per unit power dissipation, of a junction above the temperature of a stated external reference point under conditions of thermal equilibrium. Thermal Resistance data.

Thermal Runaway. A conduction that exists when heat causes more electron-hole pairs to be generated, which, in turn, causes more heat and which may eventually cause component destruction [in diodes and transistors]. Several semiconductor characteristics are a function of temperature, power loses increase with increasing temperature causing more and more heat to build within the device until the junction temperature is exceeded.

Thermal Trip Element. A circuit breaker trip element that uses the increased bending of a bimetallic strip caused by increased current to open a circuit.

Thermal Via. A via in the Printed Wiring Board [PWB] to effectively transfer heat from the top copper layer of the Printed Circuit Board [PCB] to the inner or bottom copper layers. The thermal vias should make their connection to the internal ground plane with a complete connection around the entire circumference of the plated through hole. Do not use a thermal relief web or spoke connection which impedes the conduction path into the inner copper layer. Also refer to the definition of Via, or dictionary of PWB Terms.

THERMIONIC EMISSION. Emission of electrons from a solid body as a result of elevated temperature.

 

THERMISTOR. A semiconductor device whose resistance varies with temperature. A type of bolometer characterized by a decrease in resistance as the dissipated power increases. [Thermistor Manufacturers]

THERMOCOUPLE. A junction of two dissimilar metals that produces a voltage when heated. [Thermocouple Wire Manufacturers]

THERMOCOUPLE METER MOVEMENT. A meter movement that uses the current induced in a thermocouple by the heating of a resistive element to measure the current in a circuit; used to measure ac or dc.

THERMOPLASTIC. A synthetic mixture of rosins that is flexible and used as an insulting material. Generally used as an insulator for low- and medium-range voltages. [ABS Plastic]

THETA.The Greek letter used to represent phase angle.

THICK FILM COMPONENTS. Passive circuit components (resistors and capacitors) having a thickness of 0.001 centimeter.

THIN FILM COMPONENTS. Passive circuit elements (resistors and capacitors) deposited on a substrate to a thickness of 0.0001 centimeter.

THROW. In a switch, the number of different circuits each pole can control; for example, single throw and double throw.

THYRATRON TUBE. A gas-filled triode in which a sufficiently large positive pulse applied to the control grid ionizes the gas and causes the tube to conduct, after which the control grid has no effect in conduction. A gas tube used as a modulator switching device. Thyratron Schematic.

Thyristor. A bi-stable semiconductor device that comprises three or more junctions and can be switched from the off-state or on-state to the opposite state. Manufacturers that produce Thyristors

TICKLER COIL. A small coil connected in series with the collector or plate circuit of a transistor or tube and inductively coupled to the base or grid-circuit coil to establish feedback (regeneration).

TIME BASE. An oscillator found inside an electronic instrument that serves as a reference for all of the time and frequency functions performed by that instrument.

TIME CODE. A code (usually digital) that contains enough information to synchronize a clock to the correct time-of-day. [IRIG Standards].

TIME CONSTANT. Time required for an exponential quantity to change by an amount equal to 63.2 percent of the total change that can occur.

TIME DELAY RELAY. A relay in which its contacts are delayed from opening or closing after the relay has been energized or de-energized. Also see Relay Manufacturers.

TIME-DIVISION MULTIPLEXING. The process that periodically samples the full 360 degrees of each sine wave. The sample can be of a received signal or of a signal to be transmitted.

TIME DOMAIN. The measurement domain where voltage and power are measured as functions of time.

TIME INTERVAL. The elapsed time between two events.

TIME LAG. The delay in a servosystem between the application of the input signal and the actual movement of the load.

TIMER. A circuit used to track the passage of time. A 555 IC is a common integrated circuit used as a timer via the charging rate of an RC circuit. Also refer to following 555 circuit descriptions; 555 Monostable Circuit, 555 Astable Circuit, and 555 50% Duty Cycle Circuit. See SYNCHRONIZER. [IC Clocks and Timers]. Also see Watchdog Timer.

555 Timer

TIMING SKEW. The difference in time between a pulse edge and a reference pulse or its expected transition.

TIN WHISKER. Tin whiskers are electrically conductive, crystalline structures of tin that sometimes grow from surfaces where tin (especially electroplated tin) is used as a final finish."NASA". [Tin Whisker Growth].

TINNING. The coating of a surface with a uniform layer of solder. Read more on Tinning

TNC Connector. A style of threaded coaxial connector. Refer to the TNC Connector Definition.

TOGGLE SWITCH. A mechanical switch that uses a toggle action to actuate the switch. A toggle throw may be maintained or momentary, vertical and right angle mounting, through hole or surface mount. Also see Companies making Toggle Switches

Toggle

TOLERANCE. The maximum permissible error or variation from the standard in a measuring instrument. A maximum electrical or mechanical variation of specifications that can be tolerated without impairing the operation of a device. A documented range over which a specified value may vary. Resistor Tolerance.

TOPOLOGIES. The layout of a network. The method that devices are connected together Network Topologies.

 

TORQUE. A measure of how much load a machine can turn. This measurement is expressed either in ounce-inches for torque synchro systems or in pound-feet for heavy machinery.

TORQUE DIFFERENTIAL RECEIVER (TDR). A type of differential synchro that takes two electrical inputs, one to the rotor and one to the stator, and produces a mechanical output. The output is the angular position of the rotor that represents the algebraic sum or difference of the two electrical inputs.

TORQUE DIFFERENTIAL SYNCHRO SYSTEM. A synchro system containing either a TDX or a TDR. This system is used in applications where it is necessary to compare two signals, add or subtract the signals, and furnish an output proportional to the sum or difference between the two signals.

TORQUE DIFFERENTIAL TRANSMITTER (TDX). This type of synchro is functionally the same as the CDX, except that it is used in torque systems rather than control systems.

TORQUE GRADIENT. A term used in the rating of torque synchros. It is expressed in the number of inch-ounces of torque required to pull a specific synchro 1 degree away from its normal position; for example, 0.4 inch-ounce per degree.

TORQUE RECEIVER (TR). A type of synchro that converts the electrical input supplied to its stator back to a mechanical angular output through the movement of its rotor.

TORQUE SYNCHRO SYSTEM. A synchro system that uses torque synchros to move light loads such as dials, pointers, and other similar devices.

TORQUE TRANSMITTER (TX). This type of synchro is functionally the same as the CX, except that it is used in torque synchro systems.

TORQUE VECTOR. In a gyro, a vector representing the rotary motion applied to change the direction of the rotor axis. The torque vector represents the axis about which the applied force is felt.

TOROID. A Toroidal Inductor, a round shaped magnetic core with windings forming an inductor. The graphic shows a Toroidal choke Inductor, dual winding wound around the same core.

TOROID

TOTAL RESISTANCE. (RT) The equivalent resistance of an entire circuit. For a series circuit: RT = R1 + R2 + R3 ...Rn. For parallel circuits: TOXIC VAPORS.Vapors emitted by a substance that can do bodily harm.

TPMS. Tire Pressure Monitoring System. A system mandated by the National Highway Traffic Safety Administration to automatically monitor tire pressure in vehicles.

TR RECOVERY TIME. Time required for a fired tr or atr tube to deionize to a normal level of conductance.

TRANSCONDUCTANCE. Transconductance is a ratio of the change in plate current to a change in grid voltage with the plate voltage held constant. Transconductance (gm) is usually expressed in micromhos or millimhos.

TRANSCEIVER. A circuit that Transmits and Receives [Trans-Ceives] a signal on the same line. The diagram is a 4-bit wide digital transceiver in a 14-pin DIP package, with the input and output of each pair connected together. Note the symbols within the inverting drivers indicates a Schmitt Trigger.

Transceiver

TRANSDUCER. An instrument that converts shock and vibration or other phenomena to a corresponding electrical or mechanical signal. Also refer to Sensor Manufacturers which by definition uses Transducers.

TRANSFORMER. A device composed of two or more coils, linked by magnetic lines of force, used to transfer energy from one circuit to another. Refer here for more detail, Transformer Symbols. [Transformer Manufacturer]

 

Transformer Symbol

TRANSFORMER EFFICIENCY. The ratio of output power to input power, generally expressed as a percentage.

TRANSFORMER, STEP-DOWN. A transformer so constructed that the number of turns in the secondary winding is less than the number of turns in the primary winding. This construction will provide less voltage in the secondary circuit than in the primary circuit.

TRANSFORMER, STEP-UP. A transformer so constructed that the number of turns in the secondary winding is more than the number of turns in the primary winding. This construction will provide more voltage in the secondary circuit than in the primary circuit.

 

TRANSFER RATE. The speed at which data is sent and received between two systems. The transfer rate may or may not be the same as the systems clock rate, if a clock is used. Because bus over-head is not accounted for in 'Transfer Rate' the actual through-put rate may be less [because of leading control words, framing words or CRC bytes].

TRANSISTOR. A semiconductor device with three or more elements, Emitter, Base, Collector. Also called a Bi-Polar Junction Transistor [BJT]. [Transistor Terms, BJT Manufacturers]

BJT

TRANSITION. The time it take for a signal to change from one logic level to another. The time it takes to shift from a mark to a space condition or from a space to a mark condition.

TRANSIT TIME. The time an electron takes to cross the distance between the cathode and the plate.

TRANSLATION. In a gyro, a force acting through the center of gravity of the gyro that causes no torque on the gyro rotor. Translation forces do not change the angle of the plane of rotation but move the gyroscope as a unit.

TRANSLUCENT. Those substances, such as frosted glass, through which some light rays can pass but through which objects cannot be seen clearly.

TRANSMISSION LINE. A device designed to guide electrical or electromagnetic energy from one point to another.

TRANSMISSION MEDIUM. A means of transferring intelligence from point to point; includes light, smoke, sound, wire lines, and radio-frequency waves.

TRANSMIT-RECEIVE TUBE. [TR] A gas-filled RF switch that is used as a duplexer.

TRANSMITTER. Equipment that generates and amplifies an RF carrier, modulates the RF carrier with intelligence, and radiates the signal into space.

TRANSMITTER END. Same as Input End.

TRANSMITTER FREQUENCY. [Carrier Frequency] The frequency of the unmodulated output of a transmitter.

TRANSMITTER TRANSFER SWITCHBOARD. Equipment that selectively transfers remote station functions and signals to transmitters.

TRANSPARENT. Those substances, such as glass, that pass almost all of the light waves falling upon them.

TRANSVERSE ELECTRIC MODE. A waveguide mode in which the entire electric field is perpendicular to the wide dimension and the magnetic field is parallel to the length. Also called the TE mode. Companies making Waveguide

TRANSVERSE MAGNETIC MODE. A waveguide mode in which the entire magnetic field is perpendicular to the wide dimension and some portion of the electric field is parallel to the length. Also called the TM mode.

TRANSVERSE WAVE MOTION. The up and down motion of a wave as the wave moves outward.

TREMENDOUSLY HIGH FREQUENCY. [THF] The band of frequencies from 300 gigahertz to 3,000 gigahertz.

Tremolo. Amplitude modulation of a signal by a low frequency oscillator.

 

TRIAC. A three-terminal device that is similar to two SCRs back to back with a common gate and common terminals. Although similar in construction and operation to the SCR, the triac controls and conducts current flow during both alternations of an ac cycle. [Manufacturers of Triacs]

TRIGGER. A short pulse, either positive or negative, that can be used to cause an electronic function to take place.

TRIGGER GENERATOR. A circuit that generates a trigger pulse. Refer to Synchronizer.

TRIGGER PULSES. A pulse used to cause a circuit to perform some function.

TRIODE TUBE. A three-electrode electron tube containing a plate, a cathode, and a control grid. Also see Vacuum Tube Definition

TRIP-ELEMENT. The part of a circuit breaker that senses any overload condition and causes the circuit breaker to open the circuit.

TRIP-FREE CIRCUIT BREAKER. A circuit breaker that will open a circuit even if the operating mechanism is held in the ON position. [Manufacturers of Circuit Breakers]

TRIVALENT IMPURITY. Acceptor impurities containing only three valence electrons.

TROPOSPHERE. The portion of the atmosphere, closest to the earths surface, where all weather phenomena take place.

TROPOSPHERIC SCATTER. The propagation of radio waves in the troposphere by means of scatter.

TROUBLE INDICATORS. Signal lights used to aid maintenance personnel in locating troubles quickly.

TROUBLESHOOTING. The process of locating and diagnosing faults in equipment by means of systematic checking or analysis.

TROUBLE TABLES. Tables of trouble symptoms and probable causes, furnished by many manufacturers to help technicians isolate problems.

TROUGH (BOTTOM). The peak of the negative alternation (maximum value below the line) of a sine wave.

TRUE NORTH. Geographic north. For reference also refer to Definition of Magnetic Declination, which has a relationship to the term.

TRUE POWER. The power dissipated in the resistance of the circuit, or the power actually used in the circuit.

TRUNCATED PARABOLOID. A paraboloid reflector that has been cut away at the top and bottom to increase beam width in the vertical plane.

TRUNK. A telephone circuit or channel running between two central offices operating in the public phone system.

TRUTH TABLE. A table that describes a logic function by listing all possible combinations of input values and indicating, for each combination, the true output values. [Logic Truth Tables]

TUBE DYNAMIC CONDITION. Refers to the testing condition in which a vacuum tube is actually performing its function.

TUBE STATIC CONDITION. Refers to the testing condition in which a tube has certain voltages applied but is not in its normal operating condition.

 

TUNED CIRCUIT. A circuit consisting of inductance and capacitance that can be adjusted for resonance at a desired frequency. A circuit that is used as a filter which passes or rejects specific frequencies. An LC circuit used as a frequency-determining device.

TUNED LINE. Another name for the resonant line. This line uses tuning devices to eliminate the reactance and transfer maximum power from the source to the line.

TUNNEL DIODE. A heavily doped semiconductor device that has high gain and fast switching capabilities. Also See Negative-Resistance Element. Refer to Definition of Diode Terms.

TUNNELING. The piercing of a potential barrier in a semiconductor by a particle (current carrier) that does not have sufficient energy to go over the barrier.

TURN. One complete loop of a conductor about a core.

TURNS RATIO. The ratio of the number of turns in the primary winding to the number of turns in the secondary winding of a transformer. Refer to Transformer Terms.

TWEETER. A speaker designed to operate in the higher frequency ranges, normally reproducing sound between 5K and 20KHz.

TWINAX. Twin-Axial. Dual Axial Leads. Normally meaning leads that follow the axis of the component, protruding out both ends. In this case, two leads that follow the axis. For more detail refer to the Twinax Connector Definition [which is located in the dictionary of Radar Terms].

TWISTED PAIR. A line consisting of two insulated wires twisted together to form a flexible line without the use of spacers. A cable may hold one or more Twisted Pair sets. Read more Detailed Twisted Pair definition.

Twisted Pair Cable

TWO-WIRE OPEN LINE. A parallel line consisting of two wires that are generally spaced from 2 to 6 inches apart by insulating spacers.

 

Twin Lead Cable

TWO-WIRE RIBBON. [Twin Lead] A parallel two-wire line in which uniform spacing is assured by two wires embedded in a low-loss dielectric. Design note; Replace any twin-lead cable with a coaxial cable; a coaxial cable offers the best protection from all types of outside interference.

 

UDIMM. UnBuffered DIMM [Dual In-Line Memory Module]. A type of DIMM memory stick; the front side PWB pins are not connected to the rear side pins, pins used for different functions. Also refer to Definitions of Memory Modules.

UJT. Uni-Junction Transistor. A three-terminal semiconductor device having one junction and a stable negative-resistance characteristic over a wide temperature range. [Transistor Manufacturers]

u-LAW. A companding algorithm used in digital communications to reduce the dynamic range of an audio signal. Refer to the telcom section for u-Law IC Functions.

ULP. Upper Level Protocol. The protocol which runs on top of Fibre Channel through the FC-4 layer. Typical ULPs running over Fibre Channel are Small Computer System Interface (SCSI), Internet Protocol (IP), High Performance Parallel Interface (HIPPI), and Intelligent Peripheral Interface (IPI).

ULTRAHIGH FREQUENCY. The band of frequencies from 300 megahertz to 3 gigahertz.

ULTRASONIC. Sounds above 20,000 hertz. Supersonic.

UMOS. A type of MOS [Metal-Oxide-Semiconductor] FET [Field Effect Transistor]. Refer to FET Manufacturers.

UNBALANCED CRYSTAL MIXER. A circuit consisting of a section of coaxial transmission line one-half wavelength long that is tuned to the difference (intermediate) frequency between the local oscillator and RF echo signals.

UNBALANCED LINE. A transmission line, such as a coaxial cable, in which the magnitudes of the voltages on the two conductors are not equal with respect to ground.

Uncertainty. An expression of the combined errors in a test measurement process.

UNIDIRECTIONAL. In one direction only.

UNIJUNCTION TRANSISTOR (UJT). A three-terminal, semiconductor device with a negative resistance characteristic that is used in switching circuits, oscillators, and wave-shaping circuits. The leads are Anode, Gate, and Cathode.

UJT Symbol

UNINTERRUPTIBLE POWER SUPPLY. A device that is inserted between a primary power source, such as a commercial utility, and the primary power input of equipment to be protected, e.g., a computer system, for the purpose of eliminating the effects of transient anomalies or temporary outages. (UPS vendors).

UNIT. An assembly or any combination of parts, subassemblies, and assemblies mounted together. Normally capable of independent operation. A single object or thing.

UNIT SIZE. The standards adopted to make comparisons between things of like value (for example, the unit size for conductors is the mil-foot).

Unity Gain. A gain of one. An amplifier that appears like a buffer. The graphic shows an Op-Amp configured as a Unity Gain amplifier. Note RL and CL are not required, but are shown to represent the load.

OpAmp

UNIVERSAL TIME CONSTANT CHART. A chart used to find the time constant of a circuit if the impressed voltage and the values of R and C or R and L are known. [Time Constant Chart]

UNTAPPED DELAY LINE. A simple fixed circuit delay with out adjustment or programmability. Related terms; Tapped Delay Line, Programmable Delay Line

 

Untapped Delay Line

UNTUNED LINE. Another name for the flat or non-resonant line.

UP LINK. The frequency used to transmit a signal from earth to a satellite.

UPPER-FREQUENCY CUTOFF. The highest frequency a circuit can pass.

UPPER SIDEBAND. All of the sum frequencies above the carrier.

USB. Universal Serial Bus, a computer bus which provides two-way communication between the PC and peripheral devices, over a differential 4-wire serial interface cable. [Universal Serial Bus]

 

USB Type A/B Connectors

Utopia Bus. A Bus Standard used as the Test and Operations Physical Interface for ATM [Asynchronous Transfer Mode] standard. [UTOPIA Bus]

UXGA. Ultra Extended Graphics Array. A video resolution of 1600 x 1200 pixels. [PC Video Monitor Buses]

 

VACUUM. An enclosed space which contains no air.

VACUUM EVAPORATION. Process of producing thin film components.

VACUUM TUBE. An electron tube evacuated such that its electrical characteristics are essentially unaffected by the presence of residual gas.

      
Vacuum Tube Graphic and Photo

VANE ATTENUATOR. A waveguide component used to provide attenuation.

VAR. Abbreviation for Volt-Amperes Reactive.

VARACTOR. A PN junction semiconductor, designed for microwave frequencies, in which the capacitance varies with the applied voltage. 'Varicap' or 'VVC', Voltage [dependent] variable capacitor [varies in picofarads]. [Varactor Diode Manufacturers]

VARACTOR FM MODULATOR. An FM modulator that uses a voltage-variable capacitor (varactor).

VAR HOUR. [VARhour] The reactive power, Volt-Ampere used within an hour; as measured by a VAR Hour meter.

VARIABLE. A representative symbol that can assume any of a given set of values.

VARIABLE ATTENUATOR. An attenuator for reducing the strength of an ac signal either continuously or in steps, without causing signal distortion.

VARIABLE CAPACITANCE DIODE. See Varactor.

VARIABLE-MU-TUBE. Same term as Remote-Cutoff Tube.

Variable Capacitor

VARIABLE CAPACITOR. An adjustable Capacitor. In this example the dielectric is air, other dielectrics are possible and additional package styles. Also refer to the section on Capacitor Definitions.

VARIABLE RESISTOR. A wire-wound or composition resistor, the value of which may be changed over a designed range. Also refer to the section on Resistor Definitions. [Potentiometer Manufacturers]

VARIAC. An autotransformer that contains a toroidal winding and a rotating carbon brush so that the output voltage is continuously adjustable from zero to line voltage

VARISTOR. A resistor that changes value with applied voltage. A varistor may also be called a VDR [Voltage Dependent Resistor]. Varistors will have a negative voltage coefficient. What is a Varistor. [Varistor Manufacturers]

VARNISHED CAMBRIC. Cotton cloth coated with insulation varnish. An insulation used on high-voltage conductors.

VD. Voltage DMOS. In a power supply circuit, voltage supplied by a MOS circuit, measured next to the MOS device.

VDD. In a power supply circuit supplied by a MOS circuit, the voltage supplied by a MOS device but referenced next to the power supply and not next to the DMOS device.

 

VECTOR. A line used to represent both direction and magnitude.

VEHICLE BUS. An electrical interface bus used in Vehicles; refer to a description of Automotive Buses.

VEITCH DIAGRAM. A diagram consisting of joined squares, which is used to give a graphic representation of basic logic relations.

VELOCITY. The rate at which a disturbance travels through a medium.

VELOCITY MODULATION. Modification of the velocity of an electron beam by the alternate acceleration and deceleration of electrons.

VELOCITY SERVOSYSTEM. A servo-system which controls the speed of the load it is driving.

VENN DIAGRAM. A diagram that uses circles to represent logic functions and logic relationships to one another.

VERTICAL AXIS. On a graph, the straight line axis that is plotted from bottom to top.

VERTICAL DEFLECTION PLATES. A pair of parallel electrodes in a CRT that moves the electron beam up and down.

VERTICAL PATTERN. The part of a radiation pattern that is radiated in the vertical plane.

VERTICAL PLANE. An imaginary plane that is perpendicular to the horizontal plane.

VERTICALLY POLARIZED. Waves that are radiated with the E field component perpendicular to the earth’s surface.

VERY HIGH FREQUENCY. The band of frequencies from 30 megahertz to 300 megahertz. The part of the radio spectrum from 30 to 300 megahertz, which includes TV Channels 2-13, the FM broadcast band and some marine, aviation and land mobile services. Refer to the Table of Frequency Bands

VERY LOW FREQUENCY. The band of frequencies from 3 kilohertz to 30 kilohertz.

 

VIA. A plated-thru hole in a printed wiring board. A via may exist between one or more adjacent board layers, or through the entire board. A blind via runs vertically between the top [or bottom] side and through one or more adjacent board layers, but not through the entire board. A buried via runs between one or more adjacent internal layers, but does not run to the top or bottom layer. Also refer to Thermal Via. [PWB Design].

VIA STUB. the portion of the via that is not in series with the signal. When a signal pin does not traverse the entire via, or when the signal layer using the via is not the bottom layer of the PWB. Two methods may be used to over come a via stub; Counter Boring, and Blind Vias, in both cases the via is terminated at its destination and not allowed to continue to the other side of the PWB.

Vias on a PCB

VIBRATION. The oscillation of an element of a mechanical system about a set point.

VIDEO AMPLIFIER. An amplifier designed to amplify the entire band of frequencies from 10 hertz (10Hz) to 6 megahertz (6 MHz). Also called a Wide-Band Amplifier, or Video Line Driver. Related; Manufacturers of Video Interface ICs.

 

Video Amplifier

The normal impedance for a video amplifier is 75 ohms.

VIDEO ENHANCEMENT FEATURES. Similar to Anti-Jamming Circuit
[Radar Dictionary].

VINCULUM. A straight horizontal line placed over one or more members of a compound logic expression to negate or complement. Also, used to join two or more members together.

VIRTUAL GROUND. A point in a circuit that is at ground potential (0 V) but is not connected to ground.

VISIBLE SPECTRUM. The portion of the electromagnetic spectrum that can be seen. The visible spectrum extends between 0.37um to 0.75um. Refer to the Optical Spectrum Chart

VOICE COIL. A coil attached to the speaker cone [diaphragm] of an electromagnetic speaker. Read more on Manufacturers of Speakers.

VOICE FREQUENCY. The frequency range of the human voice ranging from 32Hz to around 16KHz. Note that telephone lines only transmit voice between 300Hz to 3500Hz.

VOICE OVER INTERNET PROTOCOL (VoIP). A technology for communicating using “Internet protocol” instead of traditional analog systems. Read more on VoIP.

VOLATILE MEMORY. A type of memory circuit that does not retain its data after power is removed. Volatile memory are primarily the RAM style memory. Read more on Manufacturers of Volatile Memory ICs.

VOLT. The unit of electromotive force or electrical pressure. One volt is the pressure required to send 1 ampere of current through a resistance of 1 ohm.

VOLTAGE. The term used to signify electrical pressure. Voltage is a force that causes current to flow through an electrical conductor. The voltage of a circuit is the greatest effective difference of potential between any two conductors of the circuit.

VOLTAGE AMPLIFIER. An amplifier in which the output-signal voltage is greater than the input-signal voltage.

VOLTAGE BREAK-DOWN. The voltage magnitude required to cause insulation failure.

VOLTAGE COMPARATOR. A circuit used to compare one or more voltages to another voltage. Typically a voltage comparator is accomplished by an Operation Amplifier, normally just called a comparator. Also refer to IC comparator manufacturers.

VOLTAGE CONTROLLED OSCILLATOR. [VCXO] An oscillator that uses a external voltage to tune or change the frequency of the oscillator's output. Also refer to Voltage Controlled Oscillator Manufacturers.

VOLTAGE DEPENDENT RESISTOR. Refer to the Varistor Definition.

VOLTAGE-DIODE DETECTOR. A series-diode detector in which the diode is in series with the input voltage and the load impedance.

VOLTAGE DIVIDER. A series network in which desired portions of the source voltage may be tapped off for use in the circuit. Resistors R1 and R2 form the voltage divider, with the tapped point being between the two resistors. A voltage divide could consist of a number of different components, another common voltage divider could be formed by two capacitors in series. A Potentiometer could be used as a voltage divider by applying an input to the two ends and taking the output from the center tap and one end. Shunt Resistor applied to a Potentiometer.

R1/R2 Voltage Divider

VOLTAGE DROP. The difference in voltage between two points. It is the result of the loss of electrical pressure as a current flows through a resistance.

VOLTAGE-FEED METHOD. Same as End-Feed Method [Antenna Dictionary].

VOLTAGE GAIN. The ratio of output voltage to input voltage in an amplifier.

VOLTAGE MULTIPLIERS. Methods of increasing voltages; used primarily where low current is required.

VOLTAGE REGULATION. A measure of the ability of a generator or power supply to maintain a constant output voltage from no-load to full-load operation. Expressed as a percentage of full-load voltage; the better the regulation, the lower the percent. [IC Voltage Regulators]

VOLTAGE STANDING WAVE RATIO (VSWR). In a waveguide, the ratio of the electric field (voltage) at a maximum point to that of an adjacent minimum point.

VOLTAIC CELL. A combination of materials used to convert chemical energy into electrical energy. A voltaic or chemical cell consists of two electrodes made of different types of metals or metallic compounds placed in an electrolyte solution

VOLTMETER. A meter used to measure voltage. [Test Equipment Manufacturers]

 

WAFER. A slice of semiconductor material upon which monolithic ICs are produced.

WAFER SWITCH. A rotary switch in which the contacts are arranged on levels. Each level (wafer) is electrically independent but mechanically connected by the shaft of the switch. Rotary Switch vendors.

WatchDog Timer. A timer used by a cpu that will cause the cpu to reset if the cpu does not service [signal] the watchdog time at certain intervals. If the WatchDog Timer does not receive a signal within a certain length of time it will cause the processor to reset itself.

Watchdog Timer

WATT. The unit of electrical power that is the product of voltage and current.

WATTAGE RATING. A rating expressing the maximum power that a device can safely handle.

WATT-HOUR. A practical unit of electrical energy equal to one watt of power for one hour.

WATT-HOUR METER. A meter used to measure electrical energy.

WATTMETER. A meter used to measure electrical power.

WAVEFORM. The shape of the wave obtained when instantaneous values of an ac quantity are plotted against time in rectangular coordinates.

WAVEFORM ANALYSIS. Observation displays of voltage and current variations with respect to time or by harmonic analysis of complex signals.

WAVEFRONT. A small section of an expanding sphere of electromagnetic radiation that is perpendicular to the direction of travel of the energy.

WAVEGUIDE. A rectangular, circular, or elliptical metal pipe designed to transport electromagnetic waves through its interior. [WaveGuide Manufacturers]

WAVEGUIDE DUPLEXER. TR and atr tubes housed in a resonant cavity attached to a waveguide system.

WAVEGUIDE MODE OF OPERATION. Any particular field configuration in a waveguide that satisfies the boundary conditions. Usually divided into two broad types: the transverse electric (TE) and the transverse magnetic (TM) modes.

WAVEGUIDE POST. A rod of conductive material used as impedance changing devices in waveguides.

WAVEGUIDE SCREW. A screw that projects into a waveguide for the purpose of changing the impedance.

WAVELENGTH. The distance, usually expressed in meters, traveled by a wave during the time interval of one complete cycle. It is equal to the velocity divided by the frequency.

 

Signal Wavelengths

WAVEMETERS. Calibrated resonant circuits that are used to measure frequency. An instrument for measuring the wavelength of an RF wave. [Test Equipment Manufacturers]

WAVE MOTION. A recurring disturbance advancing through space with or without the use of a physical medium.

WAVE TRAIN. A continuous series of waves with the same amplitude and wavelength.

WAVE WINDING. An armature winding in which the two ends of each coil are connected to commutator segments separated by the distance between poles.

 

WEBER'S THEORY. A theory of magnetism which assumes that all magnetic material is composed of many tiny magnets. A piece of magnetic material that is magnetized has all of the tiny magnets aligned so that the north pole of each magnet points in one direction.

WEATHERPROOF: So constructed or protected that exposure to the weather will not interfere with successful operation. Rain-proof, rain-tight, or water-tight equipment can fulfill the requirements for weatherproof where varying weather conditions other than wetness, such as snow, ice, dust, or temperature extremes, are not a factor.

WHEATSTONE BRIDGE. An ac bridge circuit used to measure unknown values of resistance, inductance, or capacitance. The resistor labeled Rx in the diagram is the component to be measured.

wheatstone

WHITE NOISE. Noise having a frequency spectrum that is continuous and uniform over a specified frequency band.


WIDE-BAND AMPLIFIER. An amplifier designed to pass an extremely wide band of frequencies, such as a video amplifier.

Wire. An insulated or un-insulated conductor, with low resistance to current flow, that is either solid or stranded. [Wire Manufacturers]

Wire Bond. A wire for connecting the semiconductor Die to the Lead frame which forms part of the package terminal. Wire-Bond Failures by Temperature

3-Terminal WireBond Semiconductor

Wire Braid. Flexible wire constructed of small size strands in tubular form. Used for shielding or connections where constant flexing is required. A wire braid may also be used as a Drain Wire. Also refer to a Wire Braid Graphic.

Wire Bundle. Two or more wires bundled or grouped together to form a cable or group of wires.

 

Cable Wire Bundle

Wire Crimp. See Crimp.

Wire Wrapping. A method of attaching a wire between components with out using traces on a Printed Wiring Board [PWB]. The components are placed in a socket or pin which have a wire wrap terminal, while the board it self is blank with either holes or plated-through holes to accept the pins. The components are then interconnected by twisting wires around the wire wrap pins attached to the components.

Wire Wrap Terminal

WIRING DIAGRAM. A diagram that shows the connections of an equipment or its component devices or parts. It may cover internal or external connections, or both, and contains such detail as is needed to make or trace connections that are involved. Similar to or identical to a schematic diagram.

WOBBLE FREQUENCY. The frequency at which an electron wobbles on its axis under the influence of an external magnetic field of a given strength.

WOOFER. A speaker designed to operate in the low frequency ranges, producing sound normally between 20Hz and 500Hz.

WORK. The product of force and motion.

WORKING VOLTAGE. The maximum voltage that a capacitor may operate at without the risk of damage. [Dictionary of Capacitors]

 

WYE Connection Schematic

WYE (Y). A 3-phase connection in which one end of each phase winding is connected to a common point. Each free end is connected to a separate phase wire. The diagram of this connection often resembles the letter Y.

 

X. Symbol for Reactance.

X. -SERIES. Sets of data telecommunications protocols and interfaces defined by CCITT Recommendations.

X-AXIS. The horizontal axis of a chart or graph. In a gyro, the spin axis of the gyro.

X-BAND. A radio frequency band from 5200MHz to 11,000MHz
Additional Frequency Bands [Obsolete terms].

X_C. Symbol Capacitive reactance. [Capacitor Manufacturers]

XENON A rare gas. [Xenon Lamp Manufacturers]

XENON ARC LAMP. A high intensity light that excites xenon gas between two electrodes.

X_L. Symbol inductive reactance. [Inductor Manufacturers]

XLR CONNECTOR. A shielded 3-conductor microphone plug. [Connector Manufacturers]

XOFF. An abbreviation for the ASCII transmission-control character meaning “Transmitter off.”

XON. An abbreviation for the ASCII transmission-control character meaning “Transmitter on.”

X-RAY EMISSION. Penetrating radiation similar to light, but with shorter wavelength, that can penetrate human tissue.

XOR. Short for Exclusive-OR, see that term. A logic function and a logic gate [7486 XOR gate].

XNOR. Short for Exclusive-NOR, refer to that term. A logic function and a logic gate [74266 XNOR gate].

XTAL Short for crystal. [Crystal Oscillator Manufacturers]

 

Y [WYE].

 

AC WYE Power

Y-Amplifier The vertical amplifier of an oscilloscope.
[Test Equipment Manufacturers]

YAG Yttrium-Aluminum-Garnet.

Yagi antenna: A combination of dipoles to increase the gain. [Antenna Manufacturers]

YAW Side to side motion in a vehicle. The rotation of an object in a plane around a vertical axis.

Y-AXIS. In a gyro, an axis through the center of gravity and perpendicular to the spin axis. The vertical axis on a chart.

YIG Yttrium-Iron-Garnet.

YIG Crystal A crystal made of Yttrium, Iron, Garnet. [Crystal Manufacturers]

YOKE A set of coils placed over the neck of a Cathode Ray Tube [CRT] to move the electron beam position as it points at the face of the CRT.

Y-TILT. In aerial photography, the deviation of a camera from the vertical caused by the pitch of the aircraft.

 

Z. Symbol used to indicate impedance.

Z-AXIS. In a gyro, an axis through the center of gravity and mutually perpendicular to both the X (spin) and Y axes.

ZENER DIODE. A PN-junction diode designed to operate in the reverse-bias breakdown region. More Zener Diode data. [Zener Diode Manufacturers]

ZENER EFFECT. A reverse breakdown effect in diodes in which breakdown occurs at reverse voltages below 5 volts. The presence of a high energy field at the junction of a semiconductor produces the breakdown.

ZERO Adjustment. The process of Nulling out a circuit or system. Setting a circuit to a zero output condition. Related term Null

ZERO-bit Insertion. A transmission process when additional "zeros" are inserted after a fixed number of "ones" in a transmission sequence to ensure that data will not be misinterpreted as controlling information.

Zero-Buffer DDR. [ZB-DDR] A type of Double-Data-Rate [DDR] memory. [DDR Memory Manufacturers]

ZEROFILL. To fill unused storage locations with the representation of the character denoting “0”. [memory]

ZEROING. The process of adjusting a synchro to its electrical zero position. [Synchro Definition]

Zero insertion force Socket. A ZIF socket requires no force to install an IC into the socket. A spring actuated level is used to clamp the device in place once it has been installed. [Socket Manufacturers].

ZIG ZAG PACKAGE. A component package style that has alternating terminals which are off-set from one another. Refer to Zig Zag package drawing

ZINC. Symbol Zn. Atomic Number 30. Melting Point 419.5⁰C.

ZOOM. To change the magnification and focal length of a zoom lens.

ZOOM LENS. A lens having internal movable elements that allow the focal length to be changed without changing the image plane.

ZONE OF MUTUAL VISIBILITY. The area where the satellite can be seen by both the up- and down-link earth terminals.

ZONE OF SILENCE. Skip zone. The region between alternate reflections of a radio wave, in which no signal is detectable.

ZONE PLATE. A flat glass plate with concentric opaque rings that forms an image caused by diffraction rather than reflection.

ZULU TIME. [Coordinated Universal Time]. Formerly a synonym for Greenwich Mean Time. Abbreviation; Z Time. [Military].