Home

Calculations
Contacts
Conversions
Help
Links
Subjects

Electronics Topics

A: The abbreviation of Ampere, the SI unit of Electric current.
ab: A prefix indicating that an electrical unit is part of the CGS absolute electromagnetic system.
Abampere: The CGS electromagnetic unit of current equal to 10 Amperes.
Abcoulomb: The CGS unit of electric charge equal to 10 Coulomb.
Abfarad: The CGS unit of capacitance equal to 1.0x10⁹Farad.
Abhenry: The CGS unit of inductance equal to 1.0x10^-9Henry.
Abmho: The CGS unit that is the reciprocal of the ohm equal to 1.0x10⁹Siemens.
Abohm: The CGS unit of electrical resistance equal to 1.0x10^-9Ohms.
Absolute Accuracy: A measure of the uncertainty of an instrument reading compared to that of a primary standard traceable to a National standard.
Absolute Delay: The time interval between the transmission of sequential signals.
Absorbed Glass Mat Battery: A type of lead acid battery where the electrolyte is absorbed in a matrix of glass fibres holding the electrolyte next to the lead plates.
Abvolt: The CGS unit of electromotive force equal to 1.0x10^-9Volt.
AC Brownout: The condition that exists when the ac line voltage drops below some specified value.
AC coupling: Circuit that passes an AC signal while blocking a DC voltage.
AC Voltage: The AC voltage is normally given as the RMS value.
AC: An electric current whose direction changes direction with a frequency independent of circuit components.
Acausal: If a system is acausal it means the output begins before the input.
Accelerating Electrode: An electrode in an electron tube which is maintained at a positive potential with respect to the cathode and any other electrodes situated between the cathode and the accelerating electrode, thus imparting acceleration to electrons in the direction away from the cathode.
Accelerating Grid: An accelerating electrode in the form of a grid.
Accelerometer: An instrument for measuring acceleration, as of aircraft or guided missiles.
Accumulator: A device by which energy or power can be stored.
ACK: In telecommunications, this is the acknowledge character in many data codes; used most commonly for an affirmative response of correct receipt.
Acorn Valve: An acorn valve is a form of thermionic valve used at ultra-high frequencies.
Acoustic Coupler: An acoustic coupler is means of connecting external devices to a telephone handset avoiding direct electrical connection.
Active Device: A component that has gain or operates in a non-linear fashion to change the basic character of an electric signal by, for example, amplification or rectification.
Active High: The active, true, one, or asserted case of a binary signal is the high or most positive voltage level.
Active Leg: An electrical element within a transducer which changes its electrical characteristics as a function of the application of a stimulus.
Active Low: The active, true, one, or asserted case of a binary signal is the low or less positive voltage level.
Active Network: A circuit that produces gain.
Actuating System: A mechanical system that supplies and transmits energy for the operation of other mechanisms or systems.
ADC: Abbreviation of Analogue to Digital converter.
Adcock Aerial: An Adcock aerial is a radio aerial system consisting of two vertical open-spaced dipoles with screened horizontal connections.
Adjustable Resistor: A resistor whose value can be mechanically changed, usually by the use of a sliding contact.
Admittance: The ratio of current to voltage, the reciprocal of impedance.
Aerial: Another name for an antenna.
AGC: Abbreviation of Automatic Gain Control.
Air Capacitor: A capacitor, which uses air as the dielectric between the plates.
Alternating Current: An electric current whose direction changes direction with a frequency independent of circuit components.
AM: Where audio signals increase and decrease the amplitude of the "carrier wave".
Ammeter: Instrument for measuring the current in amps, milliamps or microamps.
Ammeter Shunt: A low-resistance conductor, placed in parallel with an ammeter movement, so that most of the current flows through the shunt, and only a small portion flows through the ammeter.
Amorphous Solar Cell: These cells are not as efficient as the monocrytalline cells but they do perform better in low light levels.
Ampere: The SI unit of Electric current.
Ampere-Turn: The magnetomotive force developed by 1 ampere of current flowing through a coil of one turn.
Amplidyne: A special 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: Amplifiers are used to provide a number of functions.
Amplification Factor: The voltage gain of an amplifier with no load on the output.
Amplifier: A circuit or element that provides gain.
Amplitude Modulation: Where audio signals increase and decrease the amplitude of the "carrier wave".
Amplitude Stability: The ability of the oscillator to maintain a constant amplitude in the output waveform.
Analogue: Any representation of a physical quantity in terms of a continuous variation of a second physical quantity.
Analogue to Digital converter: A circuit that converts an analog signal, having a continuously varying amplitude, to a digitally quantized representation using binary output signals.
ANC: This is an electronic method of reducing or removing unwanted sound by the production of a pressure wave of equal amplitude but opposite sign to the nwanted sound.
AND Gate: Gate that produces a logic 1 when all of its inputs are 1. In all other cases the output is 0.
Angle Modulation: Modulation in which the angle of a sine-wave carrier is varied by a modulating wave.
Antenna: A length of wire or similar that radiates (such as a transmitting antenna) or absorbs (such as a radio antenna) radio waves.
Antenna Beam Width: Width of a radar beam measured between half-power points.
Antenna Coupler: A device used for impedance matching between an antenna and a transmitter or receiver.
Antistatic: Of or pertaining to the ability to either prevent the accumulation of or to enable the dissipation of static charge.
Antitransmit Receive Tube: A tube that isolates the transmitter from the antenna and receiver.
Aperture Delay: In an analog-to-digital converter, the delay in time from when the user requests the analog input to be sampled and the actual time when this occurs.
Aperture Jitter: The amount of variance in the aperture delay.
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.
Application Specific Integrated Circuit: An integrated circuit designed for a custom requirement, frequently implemented in a gate array or field programmable array.
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.
Artificial Transmission Line: An LC network that is designed to simulate characteristics of a transmission line.
ASIC: An abbreviation of Application Specific Integrated Circuit.
Asserted High: The asserted, true, one, or active case of a binary signal is the high or most positive voltage level.
Asserted Low: The asserted, true, one, or active case of a binary signal is the low or less positive voltage level.
Astable: A circuit that has no stable state and thus oscillates at a frequency dependent on component values.
Astable Multivibrator: A multivibrator that has no stable state.
Asymmetrical Multivibrator: A multivibrator that generates rectangular waves.
Attenuator: A two port circuit or device that reduces the amplitude of an input signal by a desired amount typically expressed in decibels.
Audio Amplifier: An amplifier designed specifically for amplifying audio signals in the frequency range 20Hz to 20kHz.
Automatic Gain Control: A circuit that adjusts the gain of a stage so that the volume is constant even though the input signal may vary over a wide range.
Avalanche: A cumulative ionization process.
B: An abbreviation of bel, the logarithm of the ratio of two powers. The decibel is one tenth of a bel.
Back Bias: An external voltage applied to a diode or semiconductor junction to reduce the flow of electrons across the junction.
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.
Balun: A transformer circuit that couples a balanced transmission line to an unbalanced transmission line.
Band Gap Energy: For semiconductors and insulators, the energies that lie between the valence and conduction bands.
Band Reject Frequencies: A tuned circuit that does not pass a specified band of frequencies.
Base Terminal: That electrode of a transistor which compares generally to the grid of a vacuum tube.
Battery: A device for converting chemical energy into electrical energy.
Battery Capacity: The amount of energy available from a battery. Battery capacity is expressed in ampere-hours.
Battery Charger: A device capable of supplying electrical energy to a battery.
Battery Cycle Life: How many charge/discharge cycles the battery can endure before it loses its ability to hold a useful charge.
Bay: A subdivision of the interior space of a building.
Beam Power Tube: An electron tube in which the grids are aligned with the control grid.
bel: The bel is the logarithm of the ratio of two powers, and the decibel is one tenth of a bel.
Beta: The current gain in a grounded-emitter transistor amplifier.
Beverage Antenna: A horizontal, long-wire antenna designed for reception and transmission of low-frequency, vertically polarized ground waves.
Bias: Used in recording signals on a magnetic media (tape). As the tape passes the recording head, the head generates a varying magnetic field corresponding to the analogue signal to be recorded.
Bias Current: Current that flows through the base-emitter junction of a transistor and is adjusted to set the operating point of the transistor.
Bidirectional Array: An array that radiates in opposite directions along the line of maximum radiation.
Bifilar Winding: Two conductors wound in parallel.
Biot-Savart Law: A law describing the magnetic flux density at a distance r away from an electrical conductor.
Bipolar: A signal that swings both above and below analog ground, thus having positive and negative values.
Bistable: Circuit that has two stable states.
Bistable Multivibrator: A multivibrator that has two stable states.
Bit: Binary Digit - the smallest unit of binary data.
Bitrate: The rate at which the compressed bitstream is delivered from the storage medium to the input of a decoder.
Bitstream: An ordered series of bits that forms the coded representation of the data.
BLDC Motor: Abbreviation of Brushless DC Motor.
Bleeder Current: A current drawn continously from a souce.
Bleeder Resistor: A resistor that allows a small current drain on a power source to discharge filter capacitors or to stabilize an output.
Blocking: A condition in an amplifier, caused by overdriving one or more stages, in which the amplifier is insensitive to small signals immediately after reception of a large signal.
BNC Connector: A twist lock bayonet coaxial connector commonly used in applications involving small coaxial cables.
Bonding Wires: Fine wires connecting the bonding pads of the chip to the external leads of the package.
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.
Bottoming: A transistor in the fully conducting state.
Breadboard: An assembly of preliminary circuits.
Breakdown Voltage: Voltage at which the breakdown of a dialectric or insulator occurs.
Bridge Rectifier: A full-wave rectifier in which there are four arms - each containing a diode.
Broad Band Signal: A random signal containing a wide range of frequency components. Some types of electrical noise in a cable and acoustic noise from turbulent flow tend to be broad band.
Brush DC Motors: The Brush DC motors use commutators and carbon brushes to apply current through the windings as the motor rotates.
Brushes: Sliding contacts, usually carbon, that make electrical connection to the rotating part of a motor or generator.
Brushless DC Motors: The BLDC motor uses electronic commutation to control the current through the windings.
Buffer Amplifier: An amplifier that isolates one circuit from another.
Built in Test Equipment: A permanently mounted device that is used expressly for testing a sensor or system.
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.
Burn In: The operation of a newly fabricated device or system prior to application with the intent to stabilize the device, detect defects, and expose infant mortality.
Bus: Transmission medium for electrical or optical signals that perform a particular function, such as computer control.
Busbar: Copper bar or section used for carrying heavy currents, generally rigid when compared to cables.
By-Pass Capacitor: A capacitor that provides a path of low impedance - low resistance to AC signals.
Cable: Either a stranded conductor or a combination of conductors insulated from one another.
Cable Harness: A group of wires or ribbons of wiring used to interconnect electronic systems and subsystems.
Capacitance: The capacitance is defined as the total electric charge on a body divided by its potential.
Capacitative Coupling: The transfer of energy within an electrical network by means of the capacitance between circuit nodes. This coupling can be an intentional or accidental effect.
Capacitive Reactance: The opposition, expressed in ohms, offered to the flow of an alternating current by capacitance.
Capacitor: An electrical component that passes alternating currents but blocks direct currents.
Capacitor Microphone: Microphone whose operation depends on variations in capacitance caused by varying air pressure on the movable plate of a capacitor.
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.
Carbon Microphone: Microphone whose operation depends on pressure variation in carbon granules causing a change in resistance.
Carrier Frequency: The frequency of an unmodulated transmitter output.
Carrier Suppression: The degree to which the carrier signal is reduced in amplitude in a modulator or mixer.
Catcher Grid: In a velocity-modulated tube, a grid on which the spaced electron groups induce a signal.
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: An evacuated tube containing an anode and a cathode that generates cathode rays when operated at a high voltage.
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.
Cavity Wavemeter: An instrument used to measure microwave frequencies.
CCD: Abbreviation of Charge Coupled Device.
cdrom: Abbreviation that stands for Compact Disc Read Only Memory.
Central Processing Unit: The computer chip primarily responsible for executing instructions.
Centre Feed Method: Connecting the center of an antenna to a transmission line which is then connected to the output stage of the transmitter.
Centre Frequency: Frequency to which an amplifier is tuned. The frequency half way between the cut-off frequencies of a tuned circuit.
Centre Tap: Midway connection between the two ends of a winding.
Ceramic Capacitor: Generally a single layer capacitor that is flat and has a brown coating, Also have the name monoblock or monolithic in which the capacitor is made even smaller by creating multy-layers and coated in orange or blue paint.
Channel: A frequency interval or frequency band assigned for communications.
Characteristic Impedance: The ratio of voltage and current at every point along a transmission line on which there are no standing waves.
Charge Coupled Device: A self-scanning semiconductor imaging device which uses metal-oxide-semiconductor, surface storage and information transfer technologies.
Charge Cycle: The period of time that a capacitor in an electrical circuit is storing a charge.
Chip: A piece of semiconductor substrate on which active and/or passive circuit elements have been fabricated.
Choke: An inductor designed to present a high impedance to alternating current.
Circuit: Interconnection of components to provide an electrical path between two or more components.
Circuit Breaker: A protective device used to open a circuit when current exceeds a maximum value.
Circular Mil: An area equal to that of a circle with a diameter of 0.001 inch.
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.
Clamper: A circuit in which either the upper or lower extremity of a waveform is fixed at a desired value.
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.
Clipper Circuit: A circuit that blocks or removes the portion of a voltage waveform above some threshold voltage.
Closed Loop: A system in which the output is used to control the input.
Clutter: Confusing, unwanted echoes that interfere with the observation of desired signals on a radar indicator.
CMOS: Family of logic devices that uses p-type and n-type channel devices on the same IC.
Coaxial Cable: A round cable with a central conductor and screening around with a insulating medium between.
Coaxial Line: A type of transmission line that contains two concentric conductors.
Coil: An inductive device made by looping turns of wire around a core.
Cold Cathode Tube: A gas-filled electron tube that conducts without the use of filaments.
Colinear Array: An array with all the elements in a straight line. Maximum radiation is perpendicular to the axis of the elements.
Collector: One terminal of a transistor.
Collector Injection Modulator: The transistor equivalent of a plate modulator.
Combination Array: An array system that uses the characteristics of more than one array.
Common Base Connection: Same as ground base connection. A mode of operation of a transistor in which the base is common to both the input and output circuits and is usually earthed.
Common Collector Connection: A mode of operation of a transistor in which the collector is common to both the input and the output circuits and is usually connected to one of the power rails.
Common Emitter Connection: A mode of operation for a transistor in which the emitter is common to the input and output circuits. The base is the input terminal and the collector is the output terminal.
Common Return: return conductor common to two or more circuits.
Common-Mode Rejection Ratio: The ability of the differential amplifier to obtain the difference between the + and - inputs whilst rejecting the signal common to both.
Common-Mode Signal: A signal applied simultaneously to both inputs of a differential amplifier.
Commutator: An electrical switch that periodically reverses the current direction in an electric motor or electrical generator.
Compensation 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.
Complementary Transistor: A PNP and NPN pair used in a push-pull circuit.
Compliance Voltage: The output dc voltage of a constant current supply.
Complimentary Metal Oxide Semiconductor: Family of logic devices that uses p-type and n-type channel devices on the same IC. It has the advantage of offering medium speed and very low power requirements.
Compound Wound Motors and Generators: Machines that have a series field in addition to a shunt field.
Condenser: An old fashioned name for a capacitor.
Conduction Band: Lowest empty or partially filled band in a semiconductor.
Conductivity: The ease with which a substance transmits electricity.
Conductor: A material that allows the passage of electric charge or the easy transfer of thermal energy.
Conduit: A tubular raceway, usually metal or plastic, for holding wires or cables.
Continuity: An uninterrupted, complete path for current flow.
Control Grid: The electrode of a vacuum tube, other than a diode, upon which a signal voltage is impressed to regulate the plate current.
Control Grid Modulator: Uses a variation of grid bias to vary the instantaneous plate voltage and current.
Control Loop: Feedback circuit used to control an output signal.
Control System: A group of components systematically organized to perform a specific control purpose.
Control Variable: The inputs and outputs which a control system manipulates and measures to keep proper control.
Cookie Cutter Tuner: A mechanical magnetron tuning device that changes the frequency by changing the capacitance of the anode cavities.
Copper Loss: The power lost because of the resistance of the conductors.
Cordwood Module: A method of increasing the number of discrete components in a given space.
Corner Frequency: The frequency at which linear extrapolations of two contiguous sections of a device's or component′s transfer function drop by 3 decibels.
Corner Reflector Antenna: A half-wave antenna with a reflector consisting of two flat metal surfaces meeting at an angle behind the radiator.
Counter: A circuit that counts input pulses.
CPU: Abbreviation of Central Processing Unit, the computer chip primarily responsible for executing instructions.
Cross Talk: Unwanted breakthrough of one channel into another.
Crossover Frequency: In a loudspeaker with multiple radiators, the crossover frequency is the 3dB point of the network dividing the signal energy.
Crowbar: Circuit used to protect the output of a source from a short circuited load.
Crown of Thorns Tuner: A mechanical tuning device for magnetron tubes that changes the frequency of the cavities by changing the inductance.
CRT: An evacuated tube containing an anode and a cathode that generates cathode rays when operated at a high voltage.
Crystal Controlled Oscillator: Oscillator that uses a quartz crystal in its feedback path to maintain a stable output frequency.
Crystal Oven: A closed oven maintained at a constant temperature in which a crystal and its holder are enclosed to reduce frequency drift.
Current: Current is often used to transmit signals in noisy environments because it is much less affected by environmental noise pick-up.
Current Density: Amperes per unit area.
Current Rating: The safe current-carrying capacity of a wire or cable on a continuous basis.
Current Regulator: A circuit that provides a constant current output.
Current Sink: This refers to a sensor output configuration which switches a voltage to the negative side of the power supply.
Current Source: This refers to a sensor output configuration which provides a source of current to the load.
Current Standing Wave Ratio: The ratio of maximum to minimum current along a transmission line.
Cutoff: A transistor operating mode where very little current flows between the collector and emitter.
Cylindrical Parabolic Reflector: A parabolically shaped reflector that resembles part of a cylinder.
DAQ: Abbreviation of Data Acquisition.
Darlington Pair: Two directly coupled transistors in which the emitter of the first drives the base of the second.
DC: A current that does not change in direction.
DC DC Converter: A circuit or device that changes a dc input signal value to a different dc output signal value.
Dead Short: A short circuit having minimum resistance.
Deflection Coils: In a cathode-ray tube, coils used to bend an electron beam a desired amount.
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.
Deionization Potential: The potential at which ionization of the gas within a gas-filled tube ceases and conduction stops.
Delay Line: A transmission line or circuit that imposes a desired amount of propagation delay on an incident signal.
Delta-Sigma Modulating ADC: A high-accuracy circuit that samples at a higher rate and lower resolution than is needed and pushes the quantization noise above the frequency range of interest.
Demodulation: The process of recovering intelligence from a signal, some parameter of which was modified to carry the intelligence.
Depth of Discharge: The amount of energy that has been removed from a battery.
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.
Dielectric Losses: Power losses due to the conductance of dielectric materials.
Differential Amplifier: One whose output is proportional to the difference between two inputs.
Differential Input: Often used to reduce noise picked up by the signal leads.
Differential Voltage: The difference in voltages at two points as measured with respect to a common reference.
Digital Circuit: A collection of logic gates used to process or generate digital signals.
Digital Signal Processing: The term used for calculations performed on digital signals.
Digital Visual Interface: A video interface standard designed to provide very high visual quality on digital displays.
Digital-to-Analogue Converter: Converts a digital number into a corresponding analogue voltage or current.
Diode: A semiconductor that allows current to flow in one direction only.
Diode Drop: The forward voltage developed across a diode when it is operating.
Diode Transistor Logic: Logic gates implemented using particular configurations of diodes and bipolar junction transistors.
DIP: Abbreviation of Dual Inline Package.
Diplexer: A circuit or system that allows the ability to transmit and receive two distinct signals simultaneously.
Direct Coupled Amplifier: An amplifier in which the output of one stage is coupled to the input of the next without the use of a capacitor.
Direct Current: A current that does not change in direction.
Direct Current Amplifier: A direct coupled amplifier that can provide gain for zero-frequency signals.
Direct Short: A short circuit.
Directional Antenna: An antenna that radiates most effectively in only one direction.
Discrete Components: Individual transistors, diodes, resistors, capacitors, and inductors.
Displacement Current: The current that appears to flow through a capacitor.
Distributed Capacitance: Capacitance that is not concentrated within a lumped capacitor, but spread over a circuit or group of components.
Distributed Constants: The constants of inductance, capacitance, and resistance in a transmission line.
Distributed Inductance: Inductance that is not concentrated within a lumped inductor, but spread over a circuit or group of components.
Dither: The noise added to a signal prior to quantization which reduces the distortion and noise modulation resulting from the quantization process.
DPDT Switch: Abbreviation of Double-Pole, Double-Throw switch.
DPST Switch: Abbreviation of Double-Pole, Single-Throw switch.
Drift: Motion of carriers caused by an electric field.
Driven Element: The element of an antenna connected directly to the transmission line.
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.
DSP: Abbreviation of Digital Signal Processing, the term used for calculations performed on digital signals.
D-Sub Connector: A connector whose male end has a D shaped raised shield that protects the connecting pins.
DTL: Logic gates implemented using particular configurations of diodes and bipolar junction transistors.
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 Inline Package: IC package having two parallel rows of preformed leads.
Dummy Load: A dissipative but nonradiating device that has the impedance characteristics of an antenna or transmission line.
Duty Cycle: The ratio of operating to non-operating time for a device.
DVI: Abbreviation of Digital Visual Interface.
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 Range: The power range over which a component or system functions properly.
earth: Can mean a connection to the earth itself or the negative lead to the chassis or any point to zero voltage.
Eddy Currents: Circulating currents within inductor core material caused by magnetic lines of force cutting across the core in a direction which induces a voltage in the core material.
Electric Current: A flow of electric charges.
Electric Motor Noise: There are numerous applications of electric motors and the type of noise produced by each may be very specific to the installation and type of motor.
Electric Motor Starter: Large resistive devices placed in series with dc motor armatures to prevent the armature from drawing excessive current until armature speed develops counter emf.
Electric Motors: There are a number of different types of electric motor: AC Induction Motors, Brush Direct Current Motors, Brushless Direct Current Motors and Stepper Motors.
Electrical Engineer: An engineer concerned with electrical devices and systems and with the use of electrical energy.
Electrical Impedance: Impedance of a linear circuit element with two terminals is the ratio of the complex sinusoidally varying voltage applied across the terminals to the complex current that flows in response.
Electrical Length: Physical length expressed in terms of the wavelength of a signal for the medium in which the component or structure is situated.
Electrical Screen: A metal shield which isolates a device from external fields.
Electrical Symbols: Graphic symbols used to illustrate the various electrical or electronic components of a circuit.
Electrodynamic Meter Movement: A meter movement using fixed field coils and a moving coil; usually used in ammeters and wattmeters.
Electrodynamometer: A meter using an electrodynamic movement to measure an electric current.
Electrolytic Capacitor: A type of capacitor that has a liquid or paste between the plates to increase its capacitance.
Electromagnetic Compatibility: The capability of different electrical systems to coexist in the electromagnetic environment without causing or being subjected to interference.
Electromagnetic Field: Electric and magnetic forces that exist in a physical volume.
Electromagnetic Radiation: The emanation of an electromagnetic field from a source through space.
Electromagnetism: The generation of a magnetic field around a current-carrying conductor.
Electron Flow: The direction in which electrons flow. This is from negative to positive - as electrons are negatively charged.
Electron Gun: An electrode of a CRT that is equivalent to the cathode and control grid of conventional tubes.
Electronic Frequency Counter: An instrument that counts the number of cycles occurring during a precise time interval.
Electrostatic Meter Movement: A meter movement that uses the electrostatic repulsion of two sets of charged plates.
Electrostatic Sensitivity: The degree to which a component or device is susceptible to damage by electrostatic discharge.
Electrostatic Stress: An electrostatic field acting on an insulator, which produces polarization in the insulator and causes electrical breakdown if raised beyond a certain intensity.
Emergency Power: Temporary source of limited electrical power used upon the loss of the normal power source.
Emitter: One terminal of a transistor. Compares generally to the cathode of a tube.
Emitter Coupled Logic: Where transistors are held in the turned-on state to increase the speed of the gate.
Emitter Follower: A transistor circuit comparable to the cathode-follower tube circuit. (Also called grounded collector.)
End Fire Array: An array in which the direction of radiation is parallel to the axis of the array.
Engineering: A profession in which a knowledge of math and natural science is applied to develop ways to utilize the materials and forces of nature for the benefit of all human beings.
Equivalent Resistance: A resistance that represents the total ohmic values of a circuit component or group of circuit components.
Error Detector: The component in a servosystem that determines when the load has deviated from its ordered position, velocity, and so forth.
Error Signal: The signal whose amplitude and polarity or phase are used to correct the alignment between the controlling and the controlled elements.
E-Transformer: A special form of differential transformer employing an E-shaped core.
Excitation Voltage: The supply voltage required to activate a circuit.
Exclusive Or Gate: Logic element that features two inputs. The output will be 1 only when one or the other (but not both) is logic 1. In all other cases the output is 0.
Externally Excited Meter: A term used to describe meters that get their power from the circuit to which they are connected.
Externally Sychronized Radar: A radar system in which timing pulses are generated by a master oscillator external to the transmitter.
Far Field: The distribution of sound energy at a very much greater distance from a sources than the linear dimensions of the source and in which the sound waves can be considered to be plane waves.
Faraday Cage: An earthed metallic wire or gauze screen enclosing electrical equipment to shield it from the influence of external electric fields.
Faraday Screen: An earthed wire screen placed in an equipment so as to prevent electrostatic but not electromagnetic coupling between components.
Feedback: Occurs when some or all of the output of the device (such as an amplifier) is taken back to the input.
Feeder: A transmission line that carries energy to the antenna.
Feedhorn: A horn radiator used to feed a reflector.
Ferrite: A solid solution of one or more elements in body-centered cubic iron.
Ferrite Rod Aerial: A coil of wire wound on a ferrite material to increase the inductance of the coil. It's signal capturing capability.
Ferromagnetic Material: A highly magnetic material, such as iron, cobalt, nickel, or their alloys.
Fibre Washer: Used in many different applications for electrical or thermal insulation, to distribute the load or to add some complaince to the bolted structure.
Field Effect Transistor: A transistor that makes use of the field established in a p-type channel semiconductor material to control the flow of current through the channel.
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.
Filter: Any of various electric, electronic, acoustic, or optical devices used to reject signals, vibrations, or radiation of certain frequencies while passing others.
Finite Impulse Response Filter: A commonly used type of digital filter. Digitized samples of the audio signal serve as inputs, and each filtered output is computed from a weighted sum of a finite number of previous inputs.
Fir: A light coloured and soft wood. Needs to be dried very well before use.
FIR Filter: A commonly used type of digital filter. Digitized samples of the audio signal serve as inputs, and each filtered output is computed from a weighted sum of a finite number of previous inputs.
Fixed Resistor: A resistor having a definite resistance value that cannot be adjusted.
Fleming Valve: An earlier name for a diode, or a two-electrode vacuum tube used as a detector.
Flexible Coaxial Cable: A line made with an inner conductor that consists of flexible wire insulated from the outer conductor by a solid, continuous insulating material.
Flip Chip: A monolithic IC packaging technique that eliminates the need for bonding wires.
Flip Flop: An astable multivibrator.
Flywheel Battery: A battery in which the energy is stored in a flywheel, electrical energy is added or removed from the rotating flywheel using an electric motor.
Flywheel Effect: The continuous interchange of electric energy between the capacitor and inductor of a parallel resonant circuit wherein the energy level is diminished only by circuit resistance and radiated energy.
FM: An abbreviation of Frequency Modulation where the information signal is used to vary the carrier signal frequency.
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 that has one or more additional conductors connected across the ends parallel to each other.
Footprint: The area occupied by a device or machine.
Forward Bias: The bias applied between the base and emitter of a transistor to coincide with the P and N zone polarities.
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.
Foucault Currents: Also known as Eddy Currents.
Four Element Array: An antenna array with three parasitic elements and one driven element.
Framing: The process of synchronizing a facsimile receiver to a transmitter allowing proper picture reproduction.
Frequency Compensation Network: Circuit modification used to improve or broaden the linearity of its frequency response.
Frequency Counter: Counts digital pulses over a defined gate time.
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.
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 Meter: A meter used to measure the frequency of an ac signal.
Frequency Modulation: The information signal is used to vary the carrier signal frequency.
Frequency Multipliers: Special RF power amplifiers that multiply the input frequency.
Frequency Spectrum: The entire range of frequencies contained in a pulse or signal.
Frequency Stability: The ability of an oscillator to accurately maintain its operating frequency.
Frequency Synthesis: A process that uses hetrodyning and frequency selection to produce a signal.
Frequency Synthesizer: A frequency source of high accuracy.
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 device that converts the chemical energy obtained from a redox reaction directly into electrical energy.
Full Duplex: Operational mode of a communication circuit in which each end can simultaneously transmit and receive data.
Full Wave Voltage Doubler: Consists of two half-wave voltage rectifiers and is used to reduce the output ripple amplitude.
Fuse: A short length of wire that will easily burn out when excessive current flows.
Gain: The ratio of the output level of a circuit to the input. This will be positive for an amplifier and negative for an attenuator.
Gain Bandwidth Product: The number that results when the gain of a circuit is multiplied by the bandwidth of that circuit.
Galvanometer: An instrument for detecting and measuring a small electric current by movements of a magnetic needle or of a coil in a magnetic field.
Gamme Ring Armature: An inefficient type of armature winding in which many of the turns are shielded from the field by its own iron ring.
Ganged Tuning: The process used to tune two or more circuits with a single control.
Gate: One of the terminals of a Field Effect Transistor (FET).
Gated Automatic Gain Control: Circuit that permits automatic gain control to function only during short time intervals.
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.
Getter: An alkali metal introduced into a vacuum tube during manufacture.
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.
Greencap Capacitor: A type of polyester capacitor that the manufacturer dips in green paint to make it distinctive from all other capacitors.
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 centre 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.
Ground: 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.
Ground Clutter: Unwanted echoes, from surrounding land masses, that appear on a radar indicator.
Ground Plane: The earth or negative rail of a circuit. A large or significant mass that presents the effect of earth (ground) to a signal.
Ground Plane Antenna: A type of antenna that uses a ground plane as a simulated ground to produce low-angle radiation.
Ground Potential: Zero potential with respect to the ground or earth.
Ground Reflection Loss: The loss of RF energy each time a radio wave is reflected from the surface of the earth.
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.
Grounded Base: A transistor amplifier circuit comparable to the grounded-grid (signal ground) tube circuit.
Grounded Collector: A transistor circuit comparable to the cathode-follower tube circuit. (Also called emitter follower.)
Grounding: Establishing an electric connection to the Earth in order to neutralize an object.
Half Duplex: Describes a circuit capable of transmitting in either direction, but only one direction at a time.
Half Wave Dipole Antenna: An antenna, consisting of two rods in a single line, that radiates electromagnetic energy.
Half Wave Rectifier: A tube or solid-state diode which passes current in only one direction and thus converts ac to pulsating dc by rectification of one alternation of each cycle.
Hall Effect: The phenomenon whereby a force is brought to bear on a moving electron or hole by a magnetic field that is applied perpendicular to the direction of motion.
Hall Mobility: A measure of the flow of charged particles perpendicular to both a magnetic and an electric field.
Handshaking: The initial exchange between two communications systems prior to and during transmission to ensure proper data transfer.
HDMI: Abbreviation of High-Definition Multimedia Interface.
Headroom: A term related to dynamic range, used to express in dB, the level between the typical operating level and the maximum operating level above which the signal will be clipped.
Heat Pipe: A device that can transfer large amounts of heat with a small difference in temperature between the hot and cold interface.
Heat Shunt: A device used to absorb heat and protect heat-sensitive components during soldering.
Heat Sink: A structure that is mechanically attached to a device that generates heat.
Heaviside Oliver: An English electrical engineer who introduced Laplace transforms into electrical engineering.
Heptode: A high-vacuum thermionic valve having seven electrodes.
Hertz: The SI unit of frequency indicating the number of cycles per second (symbol Hz).
Hertz Antenna: A half-wave antenna that is installed some distance above ground and positioned either vertically or horizontally.
Hertz Heinrich: A German physics professor who did the first experiments with generating and receiving electromagnetic waves, in particular radio waves.
Hertzian Waves: Now generally called radio waves.
Heterodyning: The process of mixing the incoming signal with the local oscillator frequency. This produces the two fundamentals and the sum and difference frequencies.
High Tension: A comparative term used in electronics to denote high voltages.
High-Definition Multimedia Interface: A compact audio visual interface for transmitting uncompressed digital data.
Hits Per Scan: The number of times an RF beam strikes a target per antenna revolution.
Horizontal Deflection Plates: A pair of parallel electrodes that moves the electron beam from side to side in a CRT.
Horn Radiator: A tapered, tubular or rectangular microwave antenna that is widest at the open end.
Hot Carrier Diode: A semiconductor diode in which hot carriers are emitted from a semiconductor layer into the metal base.
Hot Spot: A region of high heat flow.
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.
Hybrid Circuit: A circuit made with a mixture of passive and active components.
Hybrid IC: Two or more integrated circuit types, or one or more integrated circuit types and discrete components on a single substrate.
IC: An abbreviation of Integrated Circuit, first proposed by G. W. A. Dunner in 1952.
Idler Frequency: In a parametric amplifier, the difference between the input signal and the pump signal frequency.
IEE: The IEE is an innovative international organisation for electronics, electrical, manufacturing and IT professionals.
IGFET: Any field-effect transistor that has an insulated gate.
IIR: Abbreviation of Infinite Impulse Response filter, a commonly used type of digital filter.
Image Frequency: An undesired frequency capable of producing the desired frequency through heterodyning.
Impedance: Mechanical impedance is the ratio of a force-like quantity to a velocity like quantity when the arguments of the real (or imaginary) parts of the quantities increase linearly with time.
Impulse: The product of the force and the time during which it acts.
In Circuit Meter: A meter permanently installed in a circuit; used to monitor circuit operation.
In Phase: Two periodic waves reaching peaks and going through zero at the same instant are said to be "in phase."
Induced Channel MOSFET: A MOSFET in which there is no actual channel between the source and the drain.
Induced Current: Current that flows as a result of an Induced EMF.
Inductance: The property of an electric circuit to store magnetic energy when carrying a current.
Inductance Bridge: An AC bridge circuit used to measure an unknown value of inductance.
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: The rotor is energized by transformer action from the stator.
Inductive Coupling: Coupling of two coils by means of magnetic lines of force.
Inductive Load: Load whose voltage and current are out-of-phase.
Inductive Reactance: The opposition to the flow of an alternating current caused by the inductance of a circuit, expressed in ohms.
Inductor: A magnetic device that stores energy in a magnetic field produced by flowing current.
Infinite Impulse Response Filter: A commonly used type of digital filter. This recursive structure accepts as inputs digitized samples of the audio signal, and then each output point is computed on the basis of a weighted sum of past output (feedback) terms, as well as past input values.
Insertion Loss: This may be applied to a silencer or other sound-reducing element, in a specified frequency band, the decrease in sound power level, measured at the location of the receiver, when a sound insulator or a sound attenuator is inserted in the transmission path between the source and the receiver.
Institution of Electrical Engineers: The IEE is an innovative international organisation for electronics, electrical, manufacturing and IT professionals, with specifically tailored products, services and qualifications to meet the needs of today′s technology industry.
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 Resistance: The resistance offered by an insulating material to current leakage.
Integrated Circuit: First proposed by G. W. A. Dunner in 1952.
Integrating ADC: An ADC whose output code represents the average value of the input voltage over a given time interval.
Interelectrode Capacitance: The capacitance between the electrodes of an electron tube.
Interference: The combining of two or more signals results in an interaction called interference.
Interpoles: Small auxiliary poles, placed between main field poles, whose magnetic field opposes the armature field and cancels armature reaction.
Intersection Law: 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 Carrier Density: The density of electrons and holes in an intrinsic semiconductor.
Intrinsic Semiconductor: A semiconductor free of defects or impurities.
Inverter: A circuit in both analogue and digital systems that provides an output that is inverse to the input. Also a circuit that converts DC to AC.
Isolation: The prevention of unwanted interaction or leakage between components.
Isometric Diagram: A diagram showing the outline of a ship, aircraft, or equipment and the location of equipment and cable runs.
ISWR: Abbreviation of Current Standing Wave Ratio.
JFET: A three-terminal transistor device where the output current flowing between the source and drain terminals is controlled by a variable electric field applied to the gate terminal. The gate design determines the type of FET: either JFET (junction FET) or MOSFET (metal-oxide semiconductor FET).
J-Type Thermocouple: Iron-constantan thermocouple with a temperature range of 0 to 750�C.
Junction: A connection between two or more parts.
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 semiconducting material that ranges from P-type at one terminal to N-type at the other.
Junction Transistor: A bipolar transistor constructed from interacting PN junctions.
Key Clicks: Interference in the form of "clicks" or "thumps" caused by the sudden application or removal of power.
kilowatt: One thousand watts.
Klystron Power Amplifier: A multicavity microwave electron tube that uses velocity modulation.
K-Type Thermocouple: Chromel-Alumel thermocouple with a temperature range of -200 to 1200�C.
Laminated Core: A core built up from thin sheets of metal insulated from each other.
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.
Large Scale Integration: An integrated circuit containing 1,000 to 2,000 logic gates or up to 64,000 bits of memory.
LC Capacitor Input Filter: Used in a power supply where output current is low and load current is relatively constant.
LC Choke Input Filter: Used in power supplies where voltage regulation is important and where the output current is relatively high and subject to varying load conditions.
LCD: Abbreviation of Liquid Crystal Display.
LDR: A layer of Cadmium Sulphide material that changes resistance according to the amount of light falling on it.
Lead Acid Battery: A battery with electrodes of lead oxide and metallic lead that are separated by an electrolyte of sulphuric acid.
Lead Inductance: Inductance of the lead wires connecting the components.
Lead Sheath: A continuous jacket of lead moulded around a single conductor or multiple conductor cable.
Lead: A wire or connection.
Leakage Current: The small amount of current that flows through the dielectric between the conductors of a transmission line.
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.
LED: A diode that emits light when current is passed through it.
Lenzs Law: A basic law which states that an induced current set up by the relative motion of a conductor and a magnetic field always flows in such a direction as to form a magnetic field which opposes the motion.
Light Dependent Resistor: A layer of Cadmium Sulphide material that changes resistance according to the amount of light falling on it.
Light Emitting Diode: A diode that emits light when current is passed through it.
Lighthouse Tube: An electron tube shaped like a lighthouse that is designed to handle large amounts of power at uhf frequencies.
LiIon: Abbreviation of Lithium Ion Battery.
Lin Log Amplifier: An amplifier in which the response is linear for weak signals and logarithmic for large signals.
Linear Impedance: An impedance in which a change in current through a device changes in direct proportion to the voltage applied to the device.
Linear Variable Differential Transformer: An inductance element that produces an electrical output proportional to the displacement of a separate movable core; used to measure position.
Liquid Crystal Display: A thin and flat display device made up of a number of colour or monochrome pixels arrayed in front of a light source or reflector.
Lissajou′s Figures: The pattern traced out when the displacements of two simple harmonic motions are traced in the x and y direction.
Lithium Ion Battery: Lithium ions are added to a carbon electrode instead of using metallic lithium as the anode.
Lithium Polymer Battery: The battery has a lithium anode that is separated from the cathode by a thin polymer electrolyte.
Load: The weight supported by a structure.
Load Isolator: A passive attenuator in which the loss in one direction is much greater than that in the opposite direction.
Loading Effect: The effect of a voltmeter upon the circuit being measured that results in an inaccurate measurement.
Lobe: An area of greater signal strength in the transmission pattern of an antenna.
Logarithmic Receiver: Receiver that uses a linear logarithmic amplifier instead of a normal linear amplifier.
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: Representing the logical elements and their interconnections without necessarily expressing construction or engineering details.
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 nonarithmetical 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.
Long Wire Antenna: An antenna that is a wavelength or more long at its operating frequency.
Loose Coupling: Inefficient coupling of energy from one circuit to another that is desirable in some applications.
Loudspeaker: An electroacoustical transducer that changes electrical energy to acoustical energy.
Lower Frequency Cutoff: The lowest frequency a circuit will pass.
Lower Sideband: All difference frequencies below that of the carrier.
LSB: Abbreviation of Least Significant Bit, the bit within a digital word that represents the smallest possible coded value.
LSI: Abbreviation of Large Scale Integration.
LVDT: An inductance element that produces an electrical output proportional to the displacement of a separate movable core; used to measure position.
Machine: Any mechanical or electrical device that performs a task for people.
Magnet Wire: Wire coated with an enamel insulation and used in coils, relays, transformers and motor windings.
Magnetic Trip Element: A circuit breaker trip element that uses the increasing magnetic attraction of a coil with increased current to open the circuit.
Mains Noise: Unwanted noise in electrical signals related to mains signals.
Majority Carriers: The term used in transistor design to indicate the primary current-movement process.
Marconi Antenna: A quarter-wave antenna that is operated with one end grounded and is positioned perpendicular to the earth.
Mark: An interval during which a signal is present.
Mask: A device used to deposit materials on a substrate in the desired pattern.
Mayer Method: A method of evaluating the propagation delay of a transmission line.
Mean Time Between Failure: The average time between failures for a continuously operating system.
Mean Time to Failure: The measured operating time of a system or component divided by the number of failures that occurred during that time.
Megohm: One million ohms.
Memory: In a computer system memory is used to store data temporarily or permanently. The capacity of the memory is normally measured in bytes.
MEMS: Abbreviation of Micro Electro Mechanical Systems.
Metal-Oxide-Silicon-Field-Effect-Transistor: In a MOSFET device the gate is insulated from the channel by a very thin (typically less than the wavelength of light) layer of glass (silicon dioxide) and the gate is either metal or doped silicon (polysilicon), hence the acronym metal-oxide semiconductor.
Meter: A device used to measure a specific quantity, such as current, voltage, or frequency.
Meter Movement: The part of the meter that moves to indicate some value.
Meter Shunt: A resistor placed in parallel with the meter terminals; used to provide increased range capability.
Mho: The unit of conductance, transconductance, or admittance; it is the word ohm spelled backwards.
Micro Electro Mechanical Systems: A technology dealing with building mechanical structures on silicon wafers using integrated circuit processing techniques.
Microcircuit: A small circuit having high equivalent-circuit-element density.
Microelectronics: The solid-state concept of electronics in which compact semiconductor materials are designed to function as an entire circuit or subassembly rather than as circuit components.
microvolt: One millionth of a volt.
milliamp: One thousandth of an amp.
millivolt: A unit of electrical potential equal to one thousandth of a volt.
Miniature Electronics: Modules, packages, pcbs, and so forth, composed exclusively of discrete components.
Minimum Discernible Signal: The weakest input signal that produces a usable signal at the output of a receiver.
Minority Carriers: The conduction band holes in n-type material and valence band electrons in p-type material.
Mismatch Loss: The loss of power delivered into a load as a result of the interconnection of devices having unequal impedances.
Modem: A device whose name combines the term modulate with demodulate which refers to its ability to transmit and receive data superimposed on a carrier frequency.
Modulator: A device that produces modulation.
Monocrystalline Solar Cell: More expenive to make as the crystals are grown under carefully controlled conditions.
Monolithic Circuit: A circuit where all elements associated with the circuit are fabricated inseparably within a continuous piece of material.
Monostable: Circuit with two states. Only one state is stable.
Moore′s Law: This states that the number of devices on a silicon chip could double each year.
MOSFET: In a MOSFET device the gate is insulated from the channel by a very thin (typically less than the wavelength of light) layer of glass (silicon dioxide) and the gate is either metal or doped silicon (polysilicon), hence the acronym metal-oxide semiconductor.
Most Significant Bit (MSB): The bit within a digital word that represents the biggest possible single-bit coded value.
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.
MSB: Abbreviation of Most Significant Bit, the bit within a digital word that represents the biggest possible single-bit coded value.
MTBF: The average time between failures for a continuously operating system.
MTTF: The measured operating time of a system or component divided by the number of failures that occurred during that time.
MU: Symbol for Amplification Factor.
Multi Element Array: An array that consists of one or more arrays and is classified as to directivity.
Multi Element Parasitic Array: An array that contains two or more parasitic elements and a driven element.
Multi Unit Tube: An electron tube containing two or more units within the same envelope.
Multiconductor: More than one conductor, as in a cable.
Multicouplers: Couplers that patch receivers or transmitters to antennas.
Multiloop Servosystem: A servosystem that contains more than one servo loop.
Multimeter: Electronic meter that displays voltage, current and resistance.
Multiplexing: A method for simultaneous transmission of two or more signals over a common carrier wave.
Multivibrator: A building block in which the output is either High or Low. There are three foms of multivibrator: Monostable, bi-stable and astable. The monostable has only one stable state, the bi-stable has two stable states and the astable is free-running (no stable states).
Mutual Conductance: The ratio of the current at the output port and the voltage at the input ports.
Mutual Flux: The total flux in the core of a transformer that is common to both the primary and secondary 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.
mV: An abbreviation of millivolt, a unit of electrical potential equal to one thousandth of a volt.
Nand Gate: Gate whose output is 0 when both input are 1 and 1 in all other cases.
NdFeB: Abbreviation of Neodymium Iron Boron.
Negative Alternation: That part of a sine wave that is below the reference level.
Negative Electrode: A terminal or electrode having more electrons than normal.
Negative Feedback: Feedback from the output of an analogue circuit that tends to oppose the input.
Negative Ground: A system where the negative terminal of the source is connected to the system′s metal chassis.
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: A device having negative voltage-current characteristics.
Negative Temperature Coefficient: A term used to describe a component whose resistance or capacitance decreases when temperature increases.
Neon Bulb: Glass envelope filled with neon gas which when ionized by an applied voltage will glow red.
Nicad: Abbreviation of Nickel Cadmium Battery.
Nickel Cadmium Battery: The battery has a nickel-hydroxide cathode, a cadmium anode, and aqueous potassium hydroxide electrolyte.
Nickel Metal Hydride Battery: The battery has a nickel-hydroxide cathode, a metal hydride anode, and aqueous potassium hydroxide electrolyte.
NiMH: A common abbreviation for Nickel Metal Hydride Battery.
N-JFET: A three-terminal transistor device where the output current flowing between the source and drain terminals is controlled by a variable electric field applied to the gate terminal. The gate design determines the type of FET: either JFET (junction FET) or MOSFET (metal-oxide semiconductor FET).
N-MOSFET: In a MOSFET device the gate is insulated from the channel by a very thin (typically less than the wavelength of light) layer of glass (silicon dioxide) and the gate is either metal or doped silicon (polysilicon), hence the acronym metal-oxide semiconductor.
Noise: Noise is any undesired signal.
Noise Floor: Normally the lowest threshold of useful signal level.
Nondegenerative Parametric Amplifier: A parametric amplifier that uses a pump signal frequency that is higher than twice the frequency of the input signal.
Nonlinear Device: A device in which the output does not rise and fall in direct proportion to the input.
Nonlinear Impedance: An impedance in which the resulting current through the device is not proportional to the applied voltage.
Nor Gate: Gate whose output is 0 if any of its inputs is a 1.
Not Gate: Logic element that acts as an inverter.
Notch Filter: An electronic network which passes signals having frequencies above and below the band-elimination frequency span.
NPN Transistor: Type of bipolar transistor using n-type p-type n-type material in its manufacture.
N-Type Thermocouple: Nicrosil-Nisil thermocouple with a temperature range of -200 to 1200�C.
Nutating: Moving an antenna feed point in a conical pattern so that the polarization of the beam does not change.
Nyquist Frequency: Half the sampling frequency. Any analog frequency component above the Nyquist frequency will, after sampling, be converted (aliased) to a frequency below the Nyquist frequency.
Off Line Test Equipment: Equipment that tests and isolates faults in modules or assemblies removed from systems.
Offset Error: If you get a reading other than zero for a zero condition then you have an offset error.
Ohmmeter: Device used to measure electrical resistance.
Ohms per Square: The resistance of any square area of thin film resistive material as measured between two parallel sides.
Omnidirectional Antenna: An antenna that radiates and receives equally in all directions.
On Line Test Equipment: Continuously monitors the performance of electronic systems.
Open Circuit: A circuit that does not provide a complete path for the flow of current.
Open Circuit Voltage: The voltage between the terminals of a battery or power source when no current is flowing.
Open Loop: A system operating without feedback.
Open Loop Gain: Gain of an amplifier when no feedback is present.
Operating Point: That point in the characteristics of a tube or transistor around which the signal voltages vary.
Operational Amplifier: One of the basic building blocks of analogue circuits.
Optical Coupler: A coupler composed of an LED and a photodiode and contained in a lightconducting medium.
Optimum Working Frequency: The most practical operating frequency that can be used with the least amount of problems.
Or Gate: Logic gate whose output will be a 1 if any of it imputs is at 1.
Oscillator: A regenerative circuit which has signal-generating characteristics.
Oscilloscope: An instrument using a cathode-ray tube for visual display of electric signals.
Output Impedance: The impedance that is presented to the load by the transmission line and its source.
Overdriven: When the input signal amplitude is increased to the point that the transistor goes into saturation and cutoff.
Overmodulation: A condition that exists when the peaks of the modulating signal are limited.
PAM: Abbreviation of Pulse Amplitude Modulation
Parabolic Reflector: An antenna reflector in the shape of a parabola.
Parallel Circuit: Two or more electrical devices connected to the same pair of terminals so separate currents flow through each.
Parallel Limiter: A resistor and diode, connected in series with the input signal, in which the output is taken across the diode.
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 to furnish a high impedance to the frequency at which the circuit is resonant.
Parametric Amplifier: A low-noise amplifier that uses a nonlinear variable reactance as the active element instead of a variable resistance.
Parasitic Array: An antenna array containing one or more elements not connected to the transmission line.
Parasitic Element: The passive element of an antenna array that is connected to neither the transmission line nor the driven element.
Patch Panel: A panel used to tie electronics components together.
PCB: Abbreviation of Printed Circuit Board.
PCM: Coding where the input signal is represented by a given number of fixed-width samples per second.
PDM: Abbreviation of Pulse Duration Modulation.
Peak Current: The maximum current that flows during a complete cycle.
Peak to Peak Value: The over-all amplitude of a signal measured from its lowest peak to its most highest peak.
Peak Value: The instantaneous maximum value of a waveform.
Peak Voltage: The maximum value present in a varying or alternating voltage.
Peaking Coil: An inductor used in an amplifier to provide high-frequency compensation, which extends the high-frequency response of the amplifier.
Pentode Tube: A five-electrode electron tube containing a plate, a cathode, a control grid, and two grids.
Permanent Magnet Speaker: A speaker with a permanent magnet mounted on soft iron pole pieces.
pF: Abbreviation of picofarad, the farad is the SI unit of capacitance.
PFM: Abbreviation of Pulse Frequency Modulation.
Phantastron: A monostable pentode circuit used to generate sharp pulses at an adjustable and accurately timed interval after receipt of a triggering signal.
Phase: Phase identifies the position at any instant which a periodic wave occupies in its cycle. A portion of a material system whose properties and composition are homogeneous and which is physically distinct from other parts of the system.
Phase Angle: The number of electrical degrees of lead or lag between the voltage and current waveforms in an ac circuit.
Phase Shifter: A device used to change the phase relationship between two ac signals.
Photo Etching: Chemical process of removing unwanted material in producing printed circuit boards.
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.
Photoelectric Effect: The ejection of electrons from metallic surfaces by illuminating light.
Photoelectric Voltage: A voltage produced by light.
Phototransistor: A transistor with a window on the top face to allow light to fall on the active surface.
Photovoltaic Cell: A unit which generates a voltage related to the light intensity impinging on it.
Piezoelectric: Any material which provides a conversion between mechanical and electrical energy.
Pixel: Single picture element of a detection device.
P-JFET: A three-terminal transistor device where the output current flowing between the source and drain terminals is controlled by a variable electric field applied to the gate terminal. The gate design determines the type of FET: either JFET (junction FET) or MOSFET (metal-oxide semiconductor FET).
Planar Tube: An electron tube, constructed with parallel electrodes and a ceramic envelope, that is used at uhf frequencies.
Plate: One of the electrodes in a storage battery.
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.
P-MOSFET: In a MOSFET device the gate is insulated from the channel by a very thin (typically less than the wavelength of light) layer of glass (silicon dioxide) and the gate is either metal or doped silicon (polysilicon), hence the acronym metal-oxide semiconductor.
PNP Transistor: Type of bipolar transistor using p-type, n-type, n-type semiconductor material.
Point Contact Diode: A diode in which the end of a fine wire is pressed against a semiconductor.
Point to Point Wiring: Individual wires run from terminal to terminal to complete a circuit.
Pole Piece: The shaped magnetic material upon which the stator windings of motors and generators are mounted or wound.
Polycrystalline Solar Cell: Cheap to make as the conditions required to produce the silicon wafers do not need to be so tightly controlled.
Position Sensor: A component in a servosystem that measures position and converts the measurement into a form convenient for transmission as a feedback signal.
Position Servosystem: A servosystem 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.
Positive Logic: The form of logic in which the more positive logic level represents 1 and the more negative level represents 0.
Positive Temperature Coefficient: The characteristic of a conductor in which the resistance increases as temperature increases.
Potentiometer: A variable resistor with three terminals-one on each end of the resistor and one "wiper" which contacts the resistor midpoint to indicate a variable position.
Potting Compound: An insulating material for encapsulating one or more circuit elements.
Power Amplifier: An amplifier in which the output-signal power is greater than the input-signal power.
Power Gain: In an antenna, the ratio of its radiated power to that of a reference.
Power Loss: The electrical power, supplied to a circuit, that does no work and is usually dissipated as heat.
Power Pentode: A special purpose tube used to provide high-current gain or power amplification.
Power Standing Wave Ratio: The ratio of the square of the maximum and minimum values of a wave.
Power Supply: A unit that supplies electrical power to another unit.
PPM: Abbreviation of Pulse Position Modulation.
Preamplifier: An amplifier that raises the output of a low-level source for further processing without appreciable degradation of the signal-to-noise ratio.
Primary Cell: A cell or battery which is not intended to be recharged and is discarded when the cell or battery has delivered all its electrical energy.
Primary Winding: The winding of a transformer connected to the electrical source.
Printed Circuit Board: A flat, insulating surface upon which printed wiring and miniaturized components are connected in a predetermined design and attached to a common base.
Protocol: The set of conventions that govern the treatment and formatting of data in an electronic communications system.
PSWR: Abbreviation of Power Standing Wave Ratio.
PTM: Abbreviation of Pulse Time Modulation.
Pulse Amplitude Modulation: Pulse modulation in which the amplitude of the pulses is varied by the modulating signal.
Pulse Code Modulation: Coding where the input signal is represented by a given number of fixed-width samples per second.
Pulse Duration: The period of time during which a pulse is present.
Pulse Duration Modulation: Pulse modulation in which the time duration of the pulses is changed by the modulating signal.
Pulse Forming Network: An LC network that alternately stores and releases energy in an approximately rectangular wave.
Pulse Frequency Modulation: 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 Oscillator: A sine-wave oscillator that is turned on and off at specific times.
Pulse Position Modulation: Pulse modulation in which the position of the pulses is varied by the modulating voltage.
Pulse Time Modulation: Pulse modulation that varies one of the time characteristics of a pulse train.
Pulse Width: Duration of time between the leading and trailing edges of a pulse.
Pulse Width Modulation: Pulse modulation in which the duration of the pulses is varied by the modulating voltage.
Pump: Electrical source of the energy required to vary the capacitance of a parametric amplifier.
Push Pull Amplifier: An amplifier that uses two transistors whose output signals are in phase opposition.
PV Cell: Abbreviation of Photovoltaic Cell.
PWM: Abbreviation of Pulse Width Modulation.
Q: The quality factor defines the sharpness of resonance.
Quality Factor: The quality factor defines the sharpness of resonance.
Quantization Error: When a continuous time signal is digitized, because there isn′t an infinite number of discrete digital levels, the difference between the actual analog value and the digital representation of that value is defined as the quantization error.
Quarter Wave Antenna: A quarter-wave antenna that is operated with one end grounded and is positioned perpendicular to the earth.
Quiescence: The operating conditions that exist in a circuit when no input signal is applied to the circuit.
Quiescent Current: The standing current that flows in a circuit when the signal is not applied. The quiescent current is usually very low or lower than when processing a signal.
Quiescent State: The period during which a transistor, tube, or other circuit element is not performing an active function in the circuit.
Radar Altimeter: Airborne radar that measures the distance of the aircraft above the ground.
Radar Beam: The space in front of a radar antenna where a target can be effectively detected or tracked.
Radar Detector: A detector that, in its simplest form, only needs to be capable of producing an output when RF energy is present at its input.
Radar Mile: Time interval, 12.36 microseconds, for RF energy to travel out from a radar to a target and back to the radar.
Radiation Field: The electromagnetic field that radiates from an antenna and travels through space.
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 Pattern: A plot of the radiated energy from an antenna.
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.
Radio: Communication by electromagnetic waves, without a connecting wire.
Radio Frequency: Any frequency of electromagnetic energy capable of propagation into space.
Radio Frequency Choke: A choke coil with a high impedance at radio frequencies.
Radio Frequency Interference: This is unwanted Electromagnetic Emissions in the radio reception bands.
Radio Horizon: The boundary beyond the natural horizon in which radio waves cannot be propagated over the earth′s surface.
Radio Waves: Electromagnetic radiation in the region of the spectrum smaller than about 3 x 10⁸Hz and wavelengths greater than about 1 m.
RAM: Abbreviation of Random Access Memory, a data storage device for which the order of access to different locations does not affect the speed of access, except for bursts.
Random Access Memory: A data storage device for which the order of access to different locations does not affect the speed of access, except for bursts.
Range: The maximum and minimum allowable full-scale signal.
Rate Gyroscope: A gyroscope used to detect and measure angular rates of change.
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.
RC Constant: Time constant of a resistor-capacitor circuit.
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.
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.
Reactance: The opposition to the flow of electricity posed by capacitors and inductors.
Reactance Amplifier: A low-noise amplifier that uses a nonlinear variable reactance as the active element instead of a variable resistance.
Reactance Tube: A tube connected in parallel with the tank circuit of an oscillator.
Reactance Tube Modulator: An FM modulator that uses a reactance tube in parallel with the oscillator tank circuit.
Receiver: Equipment that converts electromagnetic energy into an electrical signal that can be further processed.
Receiver Antenna: The device used to pick up the RF signal from space.
Receiver Sensitivity: The degree to which a receiver can usefully detect a weak signal.
Reciprocity: If in a space filled with air which is partly bounded by finitely extended fixed bodies and is partly unbounded, sound waves being excited at any point A, the resulting velocity-potential at a second point B is the same both in magnitude and phase, as it would have been at A, had B been the source of the sound.
Recursive Filter: A filter in which there is no need to store past measurements for the purpose of calculating current estimates.
Reflex Klystron: A klystron with a reflector electrode in the place of a second resonant cavity used to redirect the velocity-modulated electrons back through the cavity that produced the modulation.
Regenerative Detector: A detector circuit that produces its own oscillations, heterodynes them with an incoming signal, and deflects them.
Regenerative Feedback: Feedback in which the feedback signal is in phase with the input signal.
Regulator: The section in a basic 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.
Remote Cutoff Tube: An electron tube in which the control grid wires are farther apart at the centres than at the ends.
REN: Abbreviation of Ringer Equivalence Number.
Repeller: An electrode in a reflex klystron with the primary purpose of reversing the direction of the electron beam.
Resistance: The electrical resistance of a conductor.
Resistivity: The resistance measured in ohms of a unit volume of a substance to the flow of electric current.
Resistor: Passive component with a known resistance. The value of resistance is usually shown by a set of coloured bands on the body of the component.
Resolver: A rotary, electromechanical device used to perform trigonometric computations by varying the magnetic couplings between its primary and secondary windings.
Resonant Circuit: A circuit that contains both inductance and capacitance and is resonant at one frequency.
Resonant Line: A transmission line that has standing waves of current and voltage.
Rest Frequency: The carrier frequency during the constant-amplitude portions of a phase modulation signal.
Reverse Bias: An external voltage applied to a diode or semiconductor junction to reduce the flow of electrons across the junction.
RF: Abbreviation of Radio Frequency.
RF Amplifier: An amplifier designed to amplify signals with frequencies between 10 kilohertz and 100000 megahertz.
RF Choke: A choke coil with a high impedance at radio frequencies.
Rf Transformer: A transformer specially designed for use with radio frequencies.
Rheostat: A device to regulate the flow of electric current by transforming part or all of it into heat.
Rhombic Antenna: A diamond-shaped antenna used widely for long-distance, high-frequency transmission and reception.
Ribbon Cable: Any cable constructed as a ribbon with parallel elements.
Rigid Coaxial Line: A coaxial line consisting of a central insulated wire mounted inside of a tubular outer conductor.
Ringer Equivalence Number: Denotes the electrical load that a telephone has on the line, the maximum REN for the UK is 4.
Ringing Oscillator: A sine-wave oscillator that is turned on and off at specific times.
Ripple Frequency: The frequency of the ripple current.
Ripple Voltage: The alternating component of unidirectional voltage.
Rise Time: The time required for the output of a transducer to rise from 10% to 90% of its final value, as it responds to a step change in the measurand.
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.
RLC Circuit: An electrical circuit that has the properties of resistance, inductance, and capacitance.
Rotary Switch: A multicontact switch with contacts arranged in a circular or semicircular manner.
Rotating Field: The magnetic field in a multiphase ac motor that is the result of field windings being energized by out-of-phase currents.
Rotor: A rotating part.
RS232: Serial communications system.
Saturable Core Reactor: A coil in which the reactance is controlled by changing the permeability of the core.
Saturation: An overwhelming concentration.
SCART Connector: French-originated standard and associated 21-pin connector for connecting audio-visual equipment together.
SCR: Abbreviation of Silicon Controlled Rectifier.
SDRAM: Abbreviation for Synchronous Dynamic Random Access Memory, SDRAM delivers bursts of data at high speeds using a synchronous interface.
Secondary Cell: A galvanic battery which, after discharge, may be restored to the fully charged state by the passage of an electric current though the cell in the opposite direction to that of discharge.
Secondary Coil: The output coil of a transformer
Selectivity: The ability of a receiver to select the desired signal and reject unwanted signals.
Self Bias: In a vacuum tube circuit, the voltage developed by the flow of current through a resistor in the grid or cathode leads.
Self Discharge: The loss of useful capacity of a cell or battery due to internal chemical action.
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.
Semiconductor: An element, such as silicon, that is intermediate in electrical conductivity between conductors and insulators, through which conduction takes place by means of holes and electrons.
Sensitivity Time Control: A circuit that varies the gain of a receiver as a function of time.
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 Diode Detector: The semiconductor diode in series with the input voltage and the load impedance.
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.
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 Resonant Circuit: A resonant circuit in which the source voltage is connected in series with a capacitor and an inductor 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.
Series Wound Motor and Generator: Electric motor in which the armature and field windings are connected in series with each other.
Servo Amplifier: Either ac or dc amplifiers used in servosystems to build up signal strength.
Servo Motor: An ac or dc motor used in servo systems to move a load to a desired position or at a desired speed.
Servo System: An automatic feedback control system that compares a required condition with an actual condition and uses the difference to drive a control device to achieve the required condition.
Set Point: Value of a controlled variable, departure from which causes a controller to operate to reduce the error and restore the intended steady state.
Settling Time: When a change in a signal occurs, this is the time taken for it to settle to its new value.
Shake Table Test: A laboratory test for vibration tolerance, in which the device to be tested is placed on a vibrator.
Shaping Circuit: A circuit that alters the shapes of input waveforms.
Sharp Cutoff Tube: An electron tube that has evenly spaced grid wires.
Shielded Pair: A line consisting of parallel conductors separated from each other and surrounded by a solid dielectric.
Shielding: Technique designed to minimize internal and external interference.
Short Circuited Line: A transmission line that has a terminating impedance equal to 0.
Shunt Diode Detector: A diode detector in which the diode is in parallel with the input voltage and the load impedance.
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 with the output signal path.
Shunt Resistor: A resistor in parallel. 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.
Shunt Wound Motor and Generator: Machines in which the armature and field windings are connected in parallel with each other.
Signal Generator: A circuit that produces a variable and controllable signal.
Signal Ground: The common return or reference point for analog signals.
Signed Binary Coding: A coding scheme in which the Most Significant Bit represents the sign of a binary number.
Silicon Controlled Rectifier: A semiconductor device that functions as an electrically controlled switch.
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.
Single Pole Switch: A switch in which only one circuit is controlled.
Single-Ended Input: An analogue input measured with respect to a common ground.
Skin Effect: In the case of high frequency signals, electrons are only conducted on the outer surface, or skin, of a conductor.
Skip Distance: The distance from a transmitter to the point where the sky wave is first returned to earth.
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.
Sky Waves: Radio waves reflected back to earth from the ionosphere.
Slip: The difference between rotor speed and synchronous speed in an ac induction motor.
Slip Rings: Devices for making electric connections between stationary and rotating contacts.
SNR: Abbreviation of Signal to Noise Ratio. The ratio between a recorded signal and spurious background noise.
SoC: Abbreviation of State of Charge.
Sodium Nickel Chloride Battery: This consists of a negative liquid sodium electrode and a solid positive electrode containing nickel chloride and nickel.
Solder: A low melting point alloy that can wet copper, conduct current, and mechanically join conductors.
Soldering: Process of joining metallic surfaces with solder without melting the base material.
Solenoid: An electromagnetic device that changes electrical energy into mechanical motion.
Solid State Device: An electronic device that operates by the movement of electrons within a solid piece of semiconductor material.
Source: The object that produces the wave or disturbance.
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, a pulse transformer, and a power source.
SPDT Switch: Abbreviation of Single-Pole, Double-Throw switch.
Specific Resistance: The resistance measured in ohms of a unit volume of a substance to the flow of electric current.
Spiral Wound Lead Acid Battery: Instead of having the electrodes as flat plates, the electrodes are rolled up in a spiral.
Sprocket Tuner: A mechanical tuning device for magnetron tubes that changes the frequency of the cavities by changing the inductance.
SPST Switch: Abbreviation of Single-Pole, Single-Throw switch.
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 embedded in the rotor body.
SRAM: An integrated circuit similar to a DRAM with the exception that the memory does not need to be refreshed.
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 Ratio: The ratio of the maximum to the minimum points of a wave.
Statampere: The unit ofcurrent in the obsolete electrostatic system of units.
State of Charge: The amount of electrical charge in the battery, expressed as a percentage of the difference between the fully-charged and fully-discharged states.
Statfarad: The unit of capacitance in the obsolete electrostatic system of units.
Stathenry: The unit of inductance in the obsolete electrostatic system of units.
Static Random Access Memory: An integrated circuit similar to a DRAM (dynamic random access memory) with the exception that the memory does not need to be refreshed.
Stator: The stationary part of a rotating electrical machine.
Statvolt: The unit of electromotive force in the obsolete electrostatic system of units.
Statwatt: The unit of power in the obsolete electrostatic system of units.
Step by Step Counter: A counter that provides an output for each cycle of the input in one-step increments.
Step Down Transformer: A transformer so constructed that the number of turns in the secondary winding is less than the number of turns in the primary winding.
Step Response: The response of a system to an instantaneous jump in the input signal.
Step Up Transformer: A transformer so constructed that the number of turns in the secondary winding is more than the number of turns in the primary winding.
Stepper Motors: Stepper motors are a special case of Brushless DC Motors.
Stickoff Voltage: A low voltage used in multispeed synchrosystems to prevent false synchronizations.
Stranded Conductor: A conductor composed of a group of wires.
Subatomic Erosion: A process in which structures on an integrated circuit′s substrate are eroded by the flow of electrons in much the same way as land is eroded by a river.
Subharmonic: Sinusoidal quantity of a frequency that is an integral submultiple of a fundamental frequency.
Summing Network: A combination of two or more parallel resistors used in servosystems as an error detector.
Super High Frequency: Radio Frequencies between 3 GHz and 30 GHz.
Superconductivity: The phenomena by which, at sufficiently low temperatures, a conductor can conduct charge with zero resistance.
Superheterodyne Receiver: A type of receiver that uses a mixer to convert the RF echo to an IF signal for amplification.
Surface Mount Technology: The technology used when components are mounted to the surface of circuit boards.
Surge Protector: A device for protecting electronic equipment from damaging voltage levels sometimes occurring in electrical transients.
Swamping Resistor: A resistor used to increase or broaden the bandwidth of a circuit.
Switch: Mechanical switches are used to permit or interrupt the flow of current in a circuit.
Switching Time: The time required for the output of a switch to attain 90 percent of its steady-state level referenced to the 50 percent level of the command signal.
SWR: Abbreviation of Standing Wave Ratio.
Symmetrical Multivibrator: A circuit that generates square waves.
Symptom Elaboration: Using built-in indicating instruments or other aids to define equipment malfunction.
Symptom Recognition: Recognition of a situation in equipment operation that is not normal.
Synchro: A small motorlike analog device that operates like a variable transformer and is used primarily for the rapid and accurate transmission of data among equipments and stations.
Synchro Capacitor: A unit containing three delta-connected capacitors.
Synchronous Dynamic Random Access Memory: SDRAM delivers bursts of data at high speeds using a synchronous interface.
Synchronous Motor: An AC motor whose rotor is activated by DC.
Synchronous Speed: The speed at which the rotating field in an ac motor revolves.
Synchronous Tuning: In a klystron amplifier, a method of tuning that tunes all the resonant cavities to the same frequency.
Tachometer: An instrument that measures the rate at which a shaft is turning.
Tank Circuit: A tuned circuit used to temporarily store energy.
Tapped Resistor: A wire-wound, fixed resistor having one or more additional terminals along its length, generally for voltage-divider applications.
Target Resolution: The ability of a radar to distinguish between two or more targets that are close to each other
Telecommunications: The transmission, emission, or reception of signs, signals, writings, images, or sounds.
Television: Telecommunication medium for transmitting and receiving moving images and sound.
Temperature Range: The minimum to maximum temperature over which a piece of equipment will operate.
Terminal: A point at which electrical connections can easily be made or broken.
Terminal Board: 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.
Tertiary Logic: An experimental technology in which logic gates are based on three distinct voltage levels.
Tetrode Tube: A four-electrode electron tube containing a plate, a cathode, a control grid, and a screen grid.
Thermal Magnetic Trip Element: A single circuit breaker trip element that combines the action of a thermal and a magnetic trip element.
Thermal Resistance: The property of a material, device or system that impedes the flow of heat.
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 diode destruction.
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.
Thermion: A thermion is an electrically charged particle emitted from a heated body.
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.
Thevenin′s Theorem: Theorem that replaces any complex network with a single voltage source in series with a single resistance.
Thick Film Components: Passive circuit components having a thickness of 0.00001m
Thin Film Components: Passive circuit elements deposited on a substrate to a thickness of 0.000001m
Three Dimensional Radar: A radar set that measures the range, bearing and altitudes of a target.
Three Element Array: An array with two parasitic elements and a driven element.
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.
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 Lag: The delay between the application of the input signal and the response.
Tinning: The process of applying a thin coat of solder to materials prior to their being soldered.
Toggle: A word meaning to reverse or complement the state of something.
Tone Terminal Set: Equipment that converts TTY dc pulses into audio tones for modulation of a transmitter in audio-frequency-tone shift transmissions.
Top Hat Antenna: An antenna that is centre-fed and capacitively loaded.
Torque Differential Receiver: A type of differential synchro that takes two electrical inputs, one to the rotor and one to the stator, and produces a mechanical output.
Total Harmonic Distortion: The RMS value of the distortion appearing at multiples of the input frequency to the RMS value of the input sine wave.
Track Radar: Radar that provides continuous range, bearing, and elevation data by keeping the RF beam on the target.
Tracking Filter: A low-pass or band-pass filter which automatically tracks the input signal.
Traction Battery: A battery designed to be used to provide the power to move a vehicle.
Transceiver: A device that both transmits and receives data.
Transconductance: The ratio of the current at the output port and the voltage at the input ports.
Transformer: A transformer is a device used for converting an alternating electric current from one voltage to another.
Transformer Efficiency: The ratio of output power to input power, generally expressed as a percentage.
Transistor: A three leaded device (Collector, Base, Emitter) used for amplifying or switching.
Transistor-Transistor Logic (TTL): Referring to logic circuits consisting of two or more directly interconnected transistors, to provide conditional switching capability.
Transmission Line: A structure that guides electromagnetic energy.
Transmit Receive Tube: A gas-filled Radio Frequency switch that is used as a duplexer.
Transmitter: Equipment that generates and amplifies an Radio Frequency carrier, modulates the Radio Frequency carrier with intelligence, and radiates the signal into space.
Transmitter Frequency: The frequency of an unmodulated transmitter output.
Transmitting Antenna: The device used to send the transmitted signal energy into space.
Triatic: A special type of monopole antenna array.
Trigger: A short pulse, either positive or negative, that can be used to cause an electronic function to take place.
Triode: An electronic amplifying valve with three main electrodes.
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.
Trivalent Impurity: Acceptor impurities containing only three valence electrons.
Tropospheric Scatter: The propagation of radio waves in the troposphere by means of scatter.
Trouble Tables: Tables of trouble symptoms and probable causes, furnished by many manufacturers to help technicians isolate problems.
True Power: The power dissipated in the resistance of the circuit, or the power actually used in the circuit.
Tuned Circuit: A circuit consisting of inductance and capacitance that can be adjusted for resonance at a desired frequency.
Tuned Line: A transmission line that has standing waves of current and voltage.
Tunnel Diode: Heavily doped junction diode that has negative resistance in the forward direction of its operating range.
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.
Turnstile Antenna: A type of antenna used in VHF communications that is omnidirectional and consists of two horizontal half-wave antennas mounted at right angles to each other in the horizontal plane.
Twisted Pair: Cable that consists of individual wires wrapped around each other for carrying telephone or computer data.
Two Wire Open Line: A parallel line consisting of two wires that are generally spaced from 50 to 150mm apart by insulating spacers.
Two Wire Ribbon: A parallel two-wire line in which uniform spacing is assured by two wires imbedded in a low-loss dielectric.
UHF: Radio frequencies that are between 300 to 3000 MHz.
ULSI: Abbreviation of Ultra Large Scale Integration.
Ultra High Frequency: Radio frequencies that are between 300 to 3000 MHz.
Ultra Large Scale Integration: A chip with over 1,000,000 components.
Unbalanced Crystal Mixer: A circuit consisting of a section of coaxial transmission line one-half wavelength long that is tuned to the difference frequency between the local oscillator and RF echo signals.
Unijunction Transistor: A trigger device that has an emitter lead (e) and two bases B1 and B2.
Uninterruptible Power Supply: A type of power supply designed to support the load for specified periods when the line varies outside specified limits.
Unit: A standard for comparison in measurements. For example, the metre is a standard length which may be compared to any object to describe its length.
Upper Frequency Cutoff: The highest frequency a circuit can pass.
Upper Sideband: All of the sum frequencies above the carrier.
UPS: A type of power supply designed to support the load for specified periods when the line varies outside specified limits.
VAC: Abbreviation of Voltage Alernating Current, normally given as the RMS value.
Valve: In electronics, a valve is a device consisting of two or more metal plates enclosed in an evacuated glass bulb.
V Antenna: A bidirectional antenna, shaped like a V, which is widely used for communications.
VAr: Abbreviation of Volt Amperes Reactive.
Varactor: A p-n junction diode that is designed to act as a voltage controlled capacitance when it is operated under reverse bias.
Varactor Modulator: An FM modulator that uses a voltage-variable capacitor.
Variable Attenuator: An attenuator for reducing the strength of an AC signal either continuously or in steps, without causing signal distortion.
Variable Mu Tube: An electron tube in which the control grid wires are farther apart at the centres than at the ends.
Variable Resistor: A wire-wound or composition resistor, the value of which may be changed over a designed range.
Varistor: A two-electrode semiconductor device having a voltage- dependent nonlinear resistance.
Varnished Cambric: Cotton cloth coated with insulation varnish.
V-Band: the frequency band from 46,000 to 56,000Mhz employed in radar.
Veitch Diagram: A diagram consisting of joined squares, which is used to give a graphic representation of basic logic relations.
Velocity Servosystem: A servosystem which controls the speed of the load it is driving.
Vertical Deflection Plates: A pair of parallel electrodes in a CRT that moves the electron beam up and down.
Very High Frequency: Radio frequencies that are between 30 to 300 MHz.
Very Large Scale Integration: An integrated crcuit with 100,000 to 1,000,000 components.
Very Low Frequency: Radio Frequencies from 3 kHz to 30 kHz.
Vestigial Sideband: The transmitted portion of the sideband which has been largely suppressed by a transducer.
VHF: Radio frequencies that are between 30 to 300 MHz.
Video: The technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.
Video Amplifier: An amplifier designed to amplify the entire band of frequencies from 10Hz to 6MHz.
Vidicon: A television pickup tube utilizing a photoconductor as the sensing element.
Virtual Ground: A point in a circuit that is at ground potential but is not connected to ground.
VLF: Radio Frequencies from 3 kHz to 30 kHz.
VLSI: Abbreviation of Very Large Scale Integration, an integrated crcuit with 100,000 to 1,000,000 components.
Voice Coil: Coil attached to the diaphragm of a moving coil loudspeaker.
Volt Amperes Reactive: Unit used to measure reactive power in an AC electric power system.
Volta, Alessandro, Count (1745-1827): He invented the first practical battery using cells made from two kinds of metals; this verified his theory of differing electrical potentials for unlike metals.
Voltage: A potential difference causes current to flow in a circuit, no voltage no current.
Voltage Amplifier: An amplifier in which the output-signal voltage is greater than the input-signal voltage.
Voltage Diode Detector: The semiconductor diode in series with the input voltage and the load impedance.
Voltage Divider: A precision resistor network that reduces the output voltage of a device.
Voltage Drop: Voltage or difference in potential developed across a component due to current flow.
Voltage Gain: Ratio of amplifier output voltage to input voltage usually expressed in decibels.
Voltage Multiplier: Rectifier circuit using diodes and capacitors to produce a DC output voltage that is some multiple of the peak value of AC input voltage.
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.
Voltaic Cell: Or more commonly known as a battery.
Voltmeter: A device for measuring voltage across a component in a circuit.
VSB: The transmitted portion of the sideband which has been largely suppressed by a transducer.
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.
Watt Hour Meter: A meter used to measure electrical energy.
Wattage Rating: A rating expressing the maximum power that a device can safely handle.
Wattmeter: A meter used to measure electrical power.
Wave Antenna: Same as a Beverage Antenna.
Wave Winding: An armature winding in which the two ends of each coil are connected to commutator segments separated by the distance between poles.
Waveform: The shape of a time domain signal as seen on an oscilloscope screen.
Waveform Analysis: Observation displays of voltage and current variations with respect to time or by harmonic analysis of complex signals.
Wavemeter: An instrument for measuring the wavelength of an RF wave.
Wheatstone Bridge: Four arm bridge circuit used to measure resistance, inductance or capacitance.
White Room: A clean and dust-free room used for assembly and repair of precision equipment.
Wideband Amplifier: An amplifier designed to pass an extremely wide band of frequencies, such as a video amplifier.
Wire: A metal strand, normally pliable.
Wireless: A communications, monitoring, or control system in which a signal is carried through atmospheric space rather than along a wire.
Wiring Diagram: A diagram that shows the connections of an equipment or its component devices or parts.
Woofer: Large loudspeaker designed primarily to reproduce low frequency audio signals.
Working Voltage: The maximum voltage that a capacitor may operate at without the risk of damage.
XLR Connector: A three pin connector widely used in the audio industry.
Yagi Antenna: A directional antenna consisting of a rod pointed in the direction of the transmission/reception and several cross bars.
Zener Voltage: reverse voltage at which breakdown occurs in a zener diode.
Zeroing: The process of adjusting a synchro to its electrical zero position.
Zinc Air Battery: Uses a zinc anode, a porous carbon cathode which absorbs oxygen from the air and a base electrolyte.
Zinc Bromide Battery: Two oppositely charged liquids are passed through an ion-exchange membrane to produce electricity.