E 1. Symbol for voltage or emitter. 2. Abbreviation for illumination.

E and M leads In a signaling system, the output and input leads, respectively.

E- and M-lead signaling Communications between a trunk circuit and a separate signaling unit by way of two leads: an M lead over which battery or ground signals are transmitted to the signaling equipment, and an E lead over which open or ground signals are received from the signaling unit.

early failure A failure that occurs during the initial life phase and is generally caused by initial production, assembly, test, installation, or commissioning errors.

early-failure period Also called debugging period, burn-in period, or infant-mortality period. The period of equipment life, starting immediately after final assembly, during which equipment failures initially occur at a higher than normal rate due to the presence of defective parts and abnormal operating procedures.

early-warning radar A radar that usually scans the sky in all directions in order to detect approaching enemy planes and/or missiles at distances far enough away that interceptor planes can be in the air to meet their approach before they are near their target.

EAROM Abbreviation for electrically alterable ROM. 1. A read-only memory (ROM) that can be erased and reprogrammed any number of times. 2. Device that resembles an EPROM except that electric current rather than ultraviolet light does the erasing. This is an expensive type of PROM because it requires complete read/write control logic. Use is restricted mainly to applications such as machine controllers in which operators must change programs regularly. 3. Similar to the EPROM, the EAROM can be erased by a sort of reversed programming with a high voltage. The EAROM is thus like a RAM that will not lose its data if power is removed.

earphone Also called receiver. 1. An electroacoustic transducer intended to be placed in or over the ear. 2. An electroacoustic device that transforms electric waves into sound waves. It is intended to be closely coupled, acoustically, to the ear.

earth Term used in Great Britain for ground.

earth conductivity The conductance between opposite faces of a unit cube (usually cubic meter) of a given earth material (loam, clay, sand, rock, etc.). The volume conductivity of this earth sample is the reciprocal of its volume (not to be confused with surface) resistivity.

earth current Also called ground current. 1. Current in the ground as a result of natural causes and affecting the magnetic field of the earth, sometimes causing magnetic storms. 2. Return, fault, leakage, or stray current passing from electrical equipment through the earth.

earthed A British term meaning grounded.

earth ground 1. A connection from an electrical circuit or equipment to the earth through a water pipe or a metal rod driven into the earth. This connection reduces shock hazards from faulty equipment. Water pipes may no longer be reliable grounds because of the use of transite pipe, neoprene gaskets, and other nonconducting links. Any ground rods driven under the interior of a large building may gradually become ineffective because the building may drive the local water table down so far that the rod is essentially surrounded by dry soil. 2. An actual connection into the surface of the earth by way of a metal or chemical rod or a wire connected to such a conductor.

earth inductor See generating magnetometer.

earth-layer propagation 1. Propagation of electromagnetic waves through layers in the atmosphere of the earth. 2. Propagation of electromagnetic waves through layers below the surface of the earth.

earth oblateness The slight departure from a perfect spherical shape of the earth and the form of its gravity field.

earth permittivity The ratio of a capacitor’s capacitance using our earth sample as a dielectric to that with air as a dielectric. Permittivity has also variously been termed dielectric constant, specific inductive capacity, and capacitivity.

earth station The term used to describe the combination of antenna, low-noise amplifier (LNA), down-converter, and receiver electronics; used to receive a signal transmitted by a satellite. Earth station antennas vary in size from the 2-foot to 12-foot (65 centimeters to 3.7 meters) diameter size used for TV reception to those as large as 100 feet (30 meters) in diameter sometimes used for international communications. The typical antenna used for INTELSAT communication today is 13 to 18 meters or 40 to 60 feet in diameter.

EAS Abbreviation for extensive area service.

EAX Abbreviation for electronic automatic exchange.

EBCDIC Abbreviation for extended binary coded decimal interchange code. A coding scheme wherein letters, numbers, and special symbols are represented as unique eight-bit values, allowing for standardization between data communications devices; popularized by IBM. The code can accommodate 256 characters.

E-bend See E-plane bend.

ebiconductivity Conductivity induced as the result of electron bombardment.

ebmd Abbreviation for electron-beam mode discharge.

EBS amplifier Abbreviation for electron-bombarded semiconductor amplifier.

ec Abbreviation for enamel covered.

eccentric circle See eccentric groove.

eccentric groove Also called eccentric circle. An off-center locked groove for actuating the trip mechanism of an automatic record changer at the end of a recording.

eccentricity In disc recording, the displacement of the center of the recording-groove spiral with respect to the record center hole.

Eccles-Jordan circuit A flip-flop consisting of a two-stage, resistance-coupled amplifier. Its output is coupled back to its input, two separate conditions of stability being achieved by alternately biasing the two stages beyond cutoff.

ECCM Abbreviation for electronic counter-countermeasures.

ECG See electrocardiogram.

echelon One of a series of levels of accuracy of calibration, the highest of which is represented by an accepted national standard. There may be auxiliary levels between two successive echelons.

echo 1. In radar, that portion of the energy reflected to the receiver from a target. 2. A wave that has been reflected or otherwise returned with sufficient magnitude and delay to be distinguishable from the directly transmitted wave. 3. In facsimile, a multiple reproduction on the record sheet caused by the arrival of the same original facsimile signal at different times over transmission paths of different lengths. 4. In a radio system, an electronic condition that causes a signal such as a voice signal to be reflected from some point or points in the circuit back to the point of origination of the signal. 5. A delayed repetition (sometimes several rapid repetitions) of the original sound or signal. 6. In tape recording, refers to a provision for picking up some of the sound from a play head while recording, and feeding it back to the record head to produce a rapidly periodic repetition of each sound. Correct echo-volume adjustment causes a decay of the repeated sounds to simulate acoustical reverberation. 7. A special recording effect, in which a portion of the recorded program is taken from the playback head, a short interval after being recorded, and mixed with the incoming program. Principally used at tape speeds greater than 3¾ ips (9.5 cm/s), where the delayed signal is not heard as a separate sound. 8. An instantaneous repetition of the sound heard in playing some tapes or other recordings. This is caused by print through. 9. A portion of the transmitted signal returned from a distant point to the transmitted source with sufficient time delay to be received as interference. 10. A signal that has been reflected at one or more points during transmission with sufficient magnitude and time difference as to be detected as a signal distinct from that of the primary signal. Echoes can either lead or lag the primary signal and appear as reflections or ghosts. 11. Displaying information sent or received on a terminal, to visually detect transmission errors. Remote echo comes from the host computer. Local echo comes from the sender’s transmission. 12. The distortion created when a signal is reflected back to the originating station.

echo area Equivalent echoing area of a radar target (i.e., the relative amount of radar energy the target will reflect).

echo attenuation In a four-wire (or two-wire) circuit equipped with repeater or multiplex equipment in which the two directions of transmission can be separated from each other, the attenuation of the echo currents (which return to the input of the circuit under consideration) is determined by the ratio of the transmitted power to the echo power received.

echo box Also called phantom target. A device for checking the overall performance of a radar system. It comprises a resonant cavity that receives a portion of the pulse energy from the transmitter and retransmits it to the receiver as a slowly decaying transient. The time required for this transient response to decay below the minimum detectable level on the radar indicator is known as the ring time and is indicative of the overall performance of the radar set.

echo cancellation 1. A circuit that uses digital signal processing technology in a full-duplex communications node to remove echoes of the transmitted signal from the received signal. 2. The technique used in modems to filter out unwanted signals.

echo canceller An electronic circuit that attenuates or eliminates the echo effect on satellite telephony links. Echo cancellers are largely replacing obsolete echo suppressors.

echocardiogram Ultrasound image of the structure and motions of the heart.

echocardiography A sonarlike noninvasive method of diagnosing cardiac malfunctions. A pulsed ultrasound beam is directed through the chest wall and echoes reflected from differing tissue interfaces (e.g., soft tissue and blood; tissue and bone, etc.) are detected by the barium titanate transducer that originated the pulse. Echoes are recorded against a linear time base to provide a hard-copy record of cardiac structure movement in a given time span, generally defined by the ECG.

echo chamber A reverberant room or enclosure used for adding hollow effects or actual echoes to radio or television programs.

echo check A method of checking the accuracy of transmission of data in which the received data is returned to the sending end for comparison with the original data.

echo checking A method of checking in which transmitted information is reflected back to the transmitting point and compared with what was sent.

echo distortion 1. A modulation-related impairment created when one or more delayed echo signals introduce a phase-sensitive delay ripple across the FM portion of a system. The amplitude of this distortion is a complex function involving the relative magnitude and delay time of the echo signal with respect to the main signal, the level of baseband loading present, and the relative position of the channel in the baseband. 2. A telephone-line impairment caused by electrical reflections at distant points where line impedances are dissimilar.

echoencephaloscope An ultrasonic instrument for use in brain studies. A transducer that generates a series of ultrasonic pulses and detects the returning echoes is placed against the patient’s head. Each pulse is displayed together with its associated echoes on a cathode-ray tube.

echo intensifier A device, located at the target, that is used to increase the amplitude of the reflected energy to an abnormal level.

echo matching Rotating an antenna to a position in which the pulse indications of an echo-splitting radar are equal.

echo splitting In certain radar equipment, the echo return is split and appears as a double indication on the screen of the radar indicator. This splitting is accomplished by special electronic circuits associated with the antenna lobe switching mechanism. When the two echo indications are of equal height, the target bearing is read from a calibrated scale.

echo suppression 1. A control used to disable a responder for a short interval of time so that reception of echoes of the interrogator pulse from nearby targets is prevented. 2. A circuit used to eliminate reflected waves.

echo suppressor 1. A voice-operated device that is connected to a two-way telephone circuit to attenuate echo currents in one direction caused by telephone currents in the other direction. 2. In navigation, a circuit that desensitizes the equipment for a fixed period after the reception of one pulse, for the purpose of rejecting delayed pulses arriving from indirect reflection.

echo talker A portion of the transmitted signal returned from a distant point to the transmitting source with sufficient time delay to be received as interference.

ECL Abbreviation for emitter-coupled logic. 1. A type of unsaturated logic performed by emitter-coupled transistors. Higher speeds may be achieved with ECL than are obtainable with standard logic circuits. 2. An IC logic family characterized by its very high speed of operation, low circuit density per chip, and very high power dissipation when compared with other IC logic families. Used mainly in large, very high-speed digital computers and sold mainly on a custom-designed basis. 3. A type of current-mode logic in which the circuits are coupled with one another through emitter followers at the input or output of the logic circuit. 4. A bipolar digital IC family that uses a more complex design than TTL to speed up IC operations. Emitter-coupled logic is costly, power hungry, and difficult to use, but it is four times faster than TTL. 5. A family of nonsaturated logic devices that operate at very high speed. ECL logic dissipates relatively large amounts of power, requires a bias supply, and is characterized by low component density.

ECL bipolar memories Very high-speed cache, writable control stores, and processing sections of large computers.

ECM Abbreviation for electronic countermeasures.

ECO Abbreviation for electron-coupled oscillator.

E-core The laminated configuration resembling the capital letter E in some transformers and inductive transducers.

ECU Abbreviation for electronic control unit. 1. Electronic ignition system (Chrysler Corp.) that replaced the breaker-point ignition system. Provides spark timing to the high-energy coil and spark plugs. 2. A high-energy ignition system using a Hall effect semiconductor pickup in the distributor instead of the conventional reluctance pickup.

EDC Abbreviation for error detection code. 32 bits in each sector that are used to detect errors in the sector data of a CD.

EDCT Abbreviation for electrochemical diffused-collector transistor. A pnp transistor in which all the mass of p material is etched off and replaced with metal, which acts as a heat sink. It is suitable for high-current, high-speed core driver and computer-memory applications.

eddy current clutch A device that permits connection between a motor and a load by electrical (magnetic) means — no physical contact is involved. This method is also used for speed control by clutch slippage.

eddy-current heating Synonym for induction heating.

eddy-current loss The core loss that results when a varying induction produces electromotive forces that cause a current to circulate within a magnetic material.

eddy currents Also called Foucault currents. 1. Those currents induced in the body of a conducting mass by a variation in magnetic flux. 2. Circulating currents induced in conducting materials by varying magnetic fields. Usually undesirable because they represent loss of energy and cause heating. 3. Induced currents through an iron core in a transformer. They cause a waste of power.

edge-board connector Also called card-edge connector. A connector that mates with printed wiring leads running to the edge of a printed circuit board.

edge-board contact A series of contacts printed on or near any edge of a printed board and intended for mating with an edge connector.

edge connector 1. A one-piece receptacle, containing female contacts, designed to receive the edge of a printed circuit board and interconnect on which the male contacts are etched or printed. The connector may contain either a single or double row of female contacts. Both thermoplastic and thermosetting insulating materials are used. 2. A connector designed to mate with printed circuit boards. May be equipped with a polarizing pin or a key to ensure correct polarity. 3. A row of etched lines on the edge of a printed circuit board that is inserted into a motherboard or an expansion slot of a computer.

edge effect 1. See following blacks; following whites; leading blacks; leading whites. 2. Nonuniformity of electric fields between two parallel plates caused by an outward bulging of electric flux lines at the edges of the plates. 3. The bulging out of the lines of the electric field at the edges of two parallel electrodes, created by a potential difference between the electrodes.

edge-triggered flip-flop A type of flip-flop in which some minimum clock-signal rate of change is one necessary condition for an output change to occur.

edging Undesired coloring around the edges of different-colored objects in a color television picture.

EDI Abbreviation for electronic data interchange. A format in which business data is represented using national or international standards.

Edison base Standard screw-thread base used for ordinary electric lamps.

Edison distribution system A three-wire direct-current, distribution system, usually 120 to 240 volts, for combined light and power service from a single set of mains.

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

Edison storage cell A storage cell having negative plates of iron oxide and positive plates of nickel oxide immersed in an alkaline solution. An open-circuit voltage of 1.2 volts per cell is produced.

E-display In a radar, a rectangular display in which targets appear as blips with distance indicated by the horizontal coordinate and elevation by the vertical coordinate.

edit 1. To arrange or rearrange output information from a digital computer before it is printed out. Editing may involve deleting undesired information, selecting desired information, inserting invariant symbols, such as page numbers and typewriter characters, and applying standard processes such as zero suppression. 2. To deliberately modify the user program in a memory.

editing 1. The rearrangement of recorded material to provide a change of content or form, or for replacement of imperfect material. Usually accomplished by cutting and splicing the tape. 2. Revising text with a word processor to create an updated document.

editor 1. A program allowing such text editing functions as addition of a line or character, insertion, or deletion to permit altering of a program. Input data can be anything from programs or reports to raw instrument data. 2. Program that permits data or instructions to be manipulated and displayed. Most common use is in the preparation of new programs. 3. Program that takes the source program, written by the programmer in assembly or high-level language and entered through a keyboard or paper tape, and transfers it to a file in the computer’s auxiliary memory, such as magnetic disk or tape. The editor also acts on special commands from the user to add, delete, or replace portions of the source program in the auxiliary memory. Editors can vary significantly in the ease with which they permit a user to make changes in the program. For example, some editors can operate only on entire lines in a program, whereas others can add, delete, or replace arbitrary character strings in the program. However, the less-sophisticated editors are usually easier to learn to use. 4. An interactive software subsystem that allows users to modify test programs directly on an automatic system. 5. A program that permits a user to create new files in symbolic form or to modify existing files. 6. A program that permits a series of mnemonic instructions comprising a user program to be displayed, analyzed, corrected, and otherwise modified quickly and easily on a CRT screen or other terminal device.

EDP Abbreviation for electronic data processing.

EDP center See electronic data-processing center.

EDPM Abbreviation for electronic data-processing machine.

EEC Abbreviation for electronic engine control. Precision control of engine spark timing and exhaust gas recirculation for emissions control and good fuel mileage (Ford Motor). Uses a microprocessor chip.

EEC IV The fourth progressive version of the electronic engine control (Ford Motor) using the latest technology of microprocessor chips to control engine spark timing, EGR, and feedback carburetor fuel management.

EED Abbreviation for electroexplosive device. An electroexplosive device for use with an air cushion that automatically inflates to protect the driver when an automobile equipped with such a cushion is involved in a collision.

EEG See electroencephalograph and electroencephalogram.

EEG electrode Electrode that attaches to scalp for detecting brain waves.

EEPROM or E²PROM Abbreviation for electrically erasable programmable read-only memory. 1. A field-programmable read-only memory in which cells may be erased electrically and each cell may be reprogrammed electrically. The number of times the E²PROM can be reprogrammed (write/erase cycles) ranges from 10 times to 10⁶ times. 2. Similar to PROM, but with the capability of selective erasure of information through special electrical stimulus. Information stored in EEPROM chips is retained when the power is turned off (compare with PROM). See also electronically programmable read-only memory.

effective acoustic center Also called apparent source. The point from which the spherically divergent sound waves from an acoustic generator appear to diverge.

effective actuation time The sum of the initial actuation time and the contact chatter intervals of a relay following such actuation.

effective address The address that is actually used in carrying out a computer instruction.

effective ampere That alternating current which, when flowing through a standard resistance, produces heat at the same average rate as 1 ampere of direct current flowing in the same resistance.

effective antenna length The length that, when multiplied by the maximum current, will give the same product as the length and uniform current of an elementary electric dipole at the same location, and the same ratio field intensity in the direction of maximum radiation.

effective aperture delay In a sample-and-hold circuit, the time difference between the hold command and the time at which the input signal is at the held voltage.

effective area The effective area of an antenna in any specified direction is equal to the square of the wavelength multiplied by the power gain (or directive gain) in that direction, divided by 4π.

effective bandwidth For a bandpass filter, the width of an assumed rectangular bandpass filter having the same transfer ratio at a reference frequency and passing the same mean-square value of a hypothetical current and voltage having even distribution of energy over all frequencies.

effective capacitance The total capacitance existing between any two given points of an electric circuit.

effective conductivity The conductance between the opposite parallel faces of a portion of a material having unit length and unit cross section.

effective confusion area Amount of chaff whose radar cross-sectional area equals the radar cross-sectional area of a particular aircraft at a particular frequency.

effective current That value of alternating current that will give the same heating effect as the corresponding value of direct current. For sine-wave alternating currents, the effective value is 0.707 times the peak value.

effective cutoff See effective cutoff frequency.

effective cutoff frequency Also called effective cutoff. The frequency at which the insertion loss of an electric structure between specified terminating impedances exceeds the loss at some reference point in the transmission band.

effective facsimile band A frequency band equal in width to the difference between zero frequency and the maximum keying frequency of a facsimile signal.

effective field intensity Root-mean-square value of the inverse distance fields 1 mile from the transmitting antenna in all directions horizontally.

effective height 1. The height of the antenna center of radiation above the effective ground level. 2. In loaded or nonloaded low-frequency vertical antennas, a height equal to the moment of the current distribution in the vertical section divided by the input current.

effective irradiance to trigger The minimum effective irradiance required to switch a light-activated silicon-controlled rectifier from the off state to the on state.

effective isotropically radiated power See EIRP.

effectively grounded Grounded through a ground connection of sufficiently low impedance (inherent and/or intentionally added) so that fault grounds that may occur cannot build up voltages that are dangerous to connected equipment.

effectiveness The capability of the system or device to perform its function.

effective parallel resistance The resistance considered to be in parallel with a pure dielectric.

effective percentage modulation For a single sinusoidal input component, the ratio between the peak value of the fundamental component of the envelope and the direct-current component in the modulated conditions, expressed as a percentage.

effective radiated power 1. The product of the radio-frequency power, expressed in watts, delivered to an antenna and the relative gain of the antenna over that of a half-wave dipole antenna. 2. The product of the antenna power (transmitter power less transmission-line loss) times either the antenna power gain or the antenna field gain squared. Where circular or elliptical polarization is employed, the term effective radiated power is applied separately to the horizontal and vertical components of radiation. For allocation purposes, the effective radiated power authorized is the horizontally polarized component of radiation only. If specified for a particular direction, it is the antenna power gain in that direction only.

effective radius of the earth A value used in place of the geometrical radius to correct the atmospheric refraction when the index of refraction in the atmosphere changes linearly with height. Under conditions of standard refraction, the effective radius is one and one-third the geometrical radius.

effective resistance 1. The average rate of dissipation of electric energy during a cycle divided by the square of the effective current. 2. The equivalent pure dc resistance that, when substituted for the winding of a motor being checked, will draw the same power. It is also equivalent to the impedance of a circuit having a capacitor connected in parallel with the winding and the capacitor adjusted to unity power factor for the circuit.

effective series resistance A resistance considered to be in series with an assumed pure capacitance inductance.

effective sound pressure The root-mean-square value of the instantaneous sound pressure at one point over a complete cycle. The unit is the dyne per square centimeter.

effective speed The speed (less than rated) that can be sustained over a significant period of time and that reflects slowing effects of control codes, timing codes, error detection, retransmission, tabbing, hand keying, etc.

effective speed of transmission Also called average rate of transmission. The average rate over some specified time interval at which information is processed by a transmission facility. Usually expressed as average characters or average bits per unit time.

effective thermal resistance Of a semiconductor device, the effective temperature rise per unit power dissipation of a designated junction above the temperature of a stated external reference point under conditions of thermal equilibrium.

effective value Also called the rms (root-mean-square) value. The value of alternating current that will produce the same amount of heat in a resistance as the corresponding value of direct current. For a sine wave, the effective value is 0.707 times the peak value.

effective wavelength The wavelength corresponding to the effective propagation velocity and the observed frequency.

efficiency 1. Ratio of the useful output of a physical quantity that may be stored, transferred, or transformed by a device to the total input of the device. 2. Ratio of the output power to the input power of a power supply, usually expressed as a percentage of the input power measured at nominal line and load conditions. That part of the input not appearing in the output is converted into heat, which must be conducted away from the power supply circuitry. Efficiency is determined to a great extent by the method of regulation and is expressed as a percentage. In the absence of statements to the contrary, it is assumed to be taken at nominal input and output levels and full load conditions. 3. The percentage of the electrical input power to a speaker that is converted to acoustic energy. Varies from a small fraction of 1 percent to as much a 10 percent or more, depending on the design of the speaker. Higher efficiency means that less electrical amplifier power is required for a given listening volume, but it is not directly related to sound quality.

efficiency of a source of light The ratio of the total luminous flux to the total power consumed. In the case of an electric lamp, it is expressed in lumens per watt.

efficiency of rectification Ratio of direct-current power output to alternating-current power input of a rectifier.

E-field sensor A passive sensor that detects changes in the earth’s ambient electric field caused by the movement of an intruder. See also H-field sensor.

EFTS Abbreviation for electronic funds transfer system. A payments system in which the processing and communications necessary to effect economic exchange and the processing and communications necessary for the production and distribution of services incidental or related to economic exchanges are dependent wholly or in large part on the use of electronics.

EGA Abbreviation for enhanced graphics adapter. A color graphics system for IBM PCs and compatibles that supports 16 colors. Provides higher resolution than CGA, lower than VGA.

EHF Abbreviation for extremely high frequency.

E-H tee A waveguide junction composed of a combination of E- and H-plane tee junctions that intersect and the main guide at a common point.

E-H tuner An E-H tee having two arms terminated in adjustable plungers. It is used for impedance transformation.

EIA See Electronic Industries Association.

EIA interface 1. A set of signal properties (time duration, voltage, and current) specified by the Electronic Industries Association for business machine/data set connections. 2. A standardized set of signal characteristics for connection of terminals to modem units.

EIA RS-232-C standard A set of specifications used throughout the data communications industry to define the interconnection of data terminal equipment (DTE) and data communication equipment (DCE) for the exchange of serial binary data. This standard defines electrical signal characteristics, mechanical interface characteristics, and circuits.

EIC Abbreviation for electronic instrument cluster (Chrysler Corp.). Digital instrument display for speed, miles, fuel level, fuel consumption clock, etc.

eight-bit chip A CPU chip that processes data eight bits at a time.

eight-bit color The color range possible with an eight-bit-graphics system. In such a system, each pixel can display one of 256 colors at any given time.

eight-level code A code in which eight impulses are utilized for describing a character. Start and stop elements may be added for asynchronous transmission. The term is often used to refer to the U.S. ASCII code.

eight-track Most commonly, a cartridge tape system having eight narrow tracks on ¼-inch (6.35-mm) tape wound in a continuous loop around a single hub.

eight-track tape-recording format Either of two professional tape recording formats (half-track or quarter-track) in which eight independent channels can be recorded in the same direction.

E-indicator A rectangular radar display in which the horizontal coordinate of a target blip represents range and the vertical coordinate represents elevation.

einstein A unit of energy equal to the amount of energy absorbed by one molecule of material undergoing a photochemical reaction, as determined by the Stark-Einstein law.

Einthoven string galvanometer A moving-coil type of galvanometer in which the coil is a single wire suspended between the poles of a powerful electromagnet.

E-I pick-off An assembly of transformer-like laminations, the output coils of which develop a voltage proportional to the displacement of a magnetic element from the neutral position for limited rotary as well as angular travel.

EIRP Abbreviation for effective (or equivalent) isotropically radiated power. 1. A measure of the signal strength that a satellite transmits toward the earth below. The EIRP is highest at the center of the beam and decreases at angles away from the boresight. 2. The gain of an antenna in a given direction, multiplied by the net power accepted by the antenna from the transmitter.

EKG Abbreviation for electrocardiograph.

elastance 1. Symbolized by S. In a capacitor, the ratio of potential difference between its electrodes to the charge in the capacitor. It is the reciprocal of capacitance. The unit of measure is the daraf.

S(daraf) = V/Q

2. A measure of the difficulty of placing an electric charge in a capacitor.

elasticity The resistance of an electrostatic field. It is the reciprocal of permittivity.

elastic wave A pure acoustic wave; a moving lattice distortion without a magnetic component.

elastomer 1. A material that has the ability to recover from extreme deformation, in the order of hundreds of percent. It may be thermosetting or thermoplastic. 2. A material that at room temperature stretches under low stress to at least twice its length and snaps back to the original length on release of stress.

E layer 1. One of the regular ionospheric layers, with an average height of about 100 kilometers or 60 to 70 miles. This layer occurs during daylight hours, and its ionization is dependent on the sun’s angle. The principal layer corresponds roughly to what was formerly called the Kennelly-Heaviside layer. 2. The lowest layer of the ionosphere that supports long-distance radio communication.

elbow In a waveguide, a bend with a relatively short radius and an angle normally of 90° but sometimes, for acute angles, down to 15°.

el casel A tape system that uses a cassette similar in plan to the compact cassette, but holding ¼-inch (6.35-mm) tape running at 3¾ inches per second (9.5 cm/s); the tape is looped out of the cassette to reach the heads and capstan during recording and playback. In other cassette systems, the heads contact the tape through windows in the cassette shell.

electra A specific radionavigational aid that provides a number (usually 24) of equasignal zones. Electra is similar to sonne except that in sonne the equasignal zones as a group are periodically rotated in bearing.

electret 1. A permanently polarized piece of dielectric material produced by heating the material and placing it in a strong electric field during cooling. Some barium titanate ceramics can be polarized in this way, and so can carnauba waxes. The electric field of an electret corresponds somewhat to the magnetic field of a permanent magnet. 2. A special plastic piezoelectric element, polarized during manufacture to become the equivalent of a permanently charged capacitor. Generates an amplitude-responsive output voltage, like a ceramic element, but requires less energy from the stylus system. By loading with an appropriate resistance, its output can be converted to the equivalent of a magnetic cartridge’s velocity-responding output characteristic.

electric Containing, producing, arising from, actuated by, or carrying electricity, or designed to carry electricity and capable of so doing. Examples: electric eel, energy, motor, vehicle, wave.

electrical Related to, pertaining to, or associated with electricity but not having its properties or characteristics. Examples: electrical engineer, handbook, insulator, rating, school, unit.

electrical angle A quantity that specifies a particular instant in a cycle of alternating current. One cycle is considered to be 360°, so a half cycle is 180° and a quarter cycle is 90°. If one voltage reaches its peak value a quarter cycle after another, the phase difference, or electrical angle between the voltages, is 90°.

electrical bail A switch action in which, upon actuation of one station, the switch changes the contact position, electrically locks the switch in that position, and releases any station previously actuated.

electrical bias An electrically produced force tending to move the armature of a relay toward a given position.

electrical boresight The tracking axis as determined by an electrical indication, such as the null direction of a conical scanning or monopulse antenna system or the beam maximum direction of a highly directive antenna.

electrical bridging The formation of a conductive path between conductors.

electrical center 1. The point approximately midway between the ends of an inductor or resistor. This point divides the inductor or resistor into two equal electrical values (e.g., voltage, resistance, inductance, or number of turns). 2. The center established by the electromagnetic field distribution within a test coil. A constant-intensity signal, irrespective of the circumferential position of a discontinuity, is indicative of electrical centering. The electrical center may be different from the physical center of the test coil.

electrical charge The excess on (or in) a body of one kind (polarity) of electricity over the other kind. A plus sign indicates that positive electricity predominates, and a minus sign indicates that negative electricity predominates. Symbol: Q or q.

electrical conductivity 1. The reciprocal of the resistance in ohms measured between opposite faces of a centimeter cube of an aqueous solution at a specified temperature. 2. The property of a fluid or solid that permits the passage of an electrical current as a result of an impressed emf. It is measured by the quantity of electricity transferred across unit area per unit potential gradient per unit time. In sampling and analysis, changes in this property are utilized to measure the presence of certain ions and compounds such as sulfur dioxide.

electrical coupling Coupling discrete elements with either electrical conductors or reactances.

electrical degree One 360th part of a cycle of alternating current.

electrical discharge machining Machining in which metal is removed by a controlled electrical spark in a dielectric.

electrical distance The distance between two points, expressed as the length of time an electromagnetic wave in free space takes to travel between them.

electrical element The concept in uncombined form of any of the individual building blocks from which electronic circuits are synthesized. Examples of basic electrical elements are insulation, conductance, resistance, capacitance, and inductance.

electrical erosion The loss of contact material due to action of an electrical discharge.

electrical forming The application of electric energy to a semiconductor device in order to permanently modify the electrical characteristics.

electrical gearing A term used to describe the action of a system in which the output shaft rotates at a different speed from the input shaft, the ratio being established by electrical means.

electrical generator A machine that converts mechanical energy into electrical energy.

electrical glass insulation Insulating materials made from glass fibers of varying diameters, lengths, compositions, etc., including yarns, rovings, slivers, cords, and sheets or mats, bounded or treated only as necessary to their manufacture.

electrical ground The zero voltage reference for the power supply in an electronic device, usually connected to the equipment chassis. May also be connected to the power mains or earth ground.

electrical-impedance cephalography A method of evaluating blood circulation in the brain by measuring changes in the impedance between two surface electrodes attached to the head. This impedance decreases when the blood volume in the brain increases. The technique is also known as rheoencephalography.

electrical inertia Inductance that opposes any change in current through an inductor.

electrical initiation Any source of electrical power used to start a function or sequence.

electrical interlocks Switches mounted on contactors or other devices and operated by rods or levers. These interlocks open or close depending on the open or closed position of the contact or device with which they are associated, and are used to govern succeeding operations of the same or allied devices.

electrical length Length expressed in wavelengths, radians, or degrees. Distance in wavelengths × 2π = radians; distance in wavelengths × 360 = degrees.

electrical load A device (e.g., a speaker) comprising resistive and/or reactive components into which an amplifier, generator, etc., delivers power.

electrically alterable read-only memory Abbreviated EAROM. An electrically erasable programmable read-only memory built using metal-nitride-oxide-semiconductor (MNOS) technology. The term electrically alterable read-only memory (EAROM) is being replaced by electrically erasable programmable read-only memory (EEPROM or E²PROM). However, the MNOS technology devices should always be referred to as EAROMs.

electrically connected Joined through a conducting path or a capacitor, as distinguished from being joined merely through electromagnetic induction.

electrically erasable programmable read-only memory Abbreviated EEPROM or E²PROM.

electrically operated rheostat A rheostat used to vary the resistance of a circuit in response to some means of electrical control.

electrically operated valve A solenoid- or motor-operated valve used in vacuum, air, gas, oil, water, or similar lines.

electrically variable inductor An inductor in which the inductance can be controlled by a current or a voltage. It is usually made in the form of a saturable reactor with two windings. One is called the signal, or tuned winding, corresponding to the ac or load winding of a power-handling saturable reactor; the other is the control winding and corresponds to the dc winding of the saturable reactor.

electrical noise Unwanted electrical energy other than crosstalk in a transmission system.

electrical overstress The operation of an electronic device beyond its normal range of voltage, current, and power when abnormal electric signals are presented to it.

electrical radian 57.296°, or 1/2π (or 1/6.28) of a cycle of alternating current or voltage.

electrical ratings The combinations of voltage and current under which a device or component will operate satisfactorily in specified circuits under standard atmospheric conditions.

electrical reset A term applied to a relay to indicate that it is capable of being electrically reset after an operation.

electrical resistivity The resistance of a material to passage of an electric current through it. Expressed as ohms (units of resistance) per mil foot or as microhms (millionths of an ohm) per centimeter cubed (cm³) at a specified temperature.

electrical resolver Special type of synchro having a single winding on the stator and two windings whose axes are 90° apart on the rotor.

electrical scanning Scanning accomplished through variation of the electrical phases or amplitudes at the primary radiating element of an antenna system.

electrical service entrance A combination of intake wires and equipment including the service entrance wires, electric meter, main switch or circuit breaker, and main distribution or service panel through which the supply of power enters the home.

electrical sheet Iron or steel sheets from which laminations for electric motors are punched.

electrical shielding Copper screen, a wire braid, or any conducting material that surrounds a circuit or cable conductors to exclude electrostatic or radio-frequency noises.

electrical switch A device that makes, breaks, or changes the connections in an electric circuit.

electrical system The organized arrangement of all electrical and electromechanical components and devices in a way that will properly control the particular machine tool or industrial equipment.

electrical twinning See twinning.

electrical zero A standard synchro position at which electrical outputs have defined amplitudes and time phase.

electric arc A discharge of energy through a gas.

electric bell An audible signaling device consisting of one or more gongs and an electromagnetically actuated striking mechanism.

electric brazing A brazing (alloying) process in which the heat is furnished by an electric current.

electric breakdown voltage See dielectric breakdown voltage.

electric breeze or wind The emission of electrons from a sharp point of a conductor that carries a high negative potential.

electric charge 1. Electric energy stored on the surface of an object. 2. A property of electrons and protons. Similarly charged particles repel one another. Particles having opposite charges attract one another. 3. Electric energy that is stored as stress on the surface of a dielectric.

electric chronograph A highly accurate apparatus for measuring and recording time intervals.

electric circuit A continuous path consisting of wires and/or circuit elements over or through which an electric current can flow. If the path is broken at any point, current can no longer flow and there is no circuit.

electric coil Successive turns of insulated wire that create a magnetic field when an electric current is passed through them. It may also consist of a number of separately insulated sections that lie side by side around the same magnetic circuit.

electric contact A separable junction between two conductors that is designed to make, carry, or break (in any sequence or singly) an electric circuit.

electric controller A device that governs the amount of electric power delivered to an apparatus.

electric current Electricity in motion. In the atoms of metallic substances, there are a number of free electrons, or negatively charged particles that wander in the spaces between the atoms of the metal. The electron movement is normally without any definite direction and cannot be detected. The connection of an electric battery produces an electric field in the metal and causes the free electrons to move or drift in one direction; it is this electron drift that constitutes an electric current. Electrons, being of negative polarity, are attracted to the positive terminal of the battery, and so the actual direction of flow of electricity is from negative to positive, that is, opposite to the conventional direction usually adopted.

electric delay line A delay line using properties of lumped or distributed capacitive and inductive elements. Can be used as a storage medium by recirculating the information-carrying signal.

electric dipole Also called a doublet. A simple antenna comprising a pair of oppositely charged conductors capable of radiating an electromagnetic wave in response to the movement of an electric charge from one conductor to the other.

electric-discharge lamp 1. A sealed glass enclosure containing a metallic vapor or an inert gas through which electricity is passed to produce a bright glow. 2. A lamp in which light (or radiant energy) is produced by the passage of an electric current through a vapor or a gas. Electric discharge lamps may be named after the filling gas or vapor that is responsible for the major portion of the radiation, e.g., mercury lamps, sodium lamps, neon lamps, and argon lamps.

electric displacement See electric-flux density.

electric-displacement density See electric-flux density.

electric eye 1. The layman’s term for a photoelectric cell. 2. The cathode-ray, tuning-indicator tube used in some radio receivers.

electric field 1. The region about a charged body. Its intensity at any point is the force that would be exerted on a unit positive charge at that point. 2. A condition detectable in the vicinity of an electrically charged body such that forces act on other electric charges in proportion to their magnitudes. 3. Field of force that exists in the space around electrically charged particles. Lines of force are imagined to originate at the protons or positively charged particles and to terminate on electrons or negatively charged particles.

electric-field intensity A measure of the force exerted at a point by a unit charge at that point.

electric-field strength The magnitude of the electric field in an electromagnetic wave. Usually stated in volts per meter. See also dielectric strength.

electric-field vector At a point in an electric field, the force on a stationary positive charge per unit charge. May be measured in either newtons per coulomb or volts per meter. This term is sometimes called the electric-field intensity, but such use of the word intensity is deprecated in favor of field strength, since intensity denotes power in optics and radiation.

electric-filament lamp A glass bulb either evacuated or filled with an inert gas and having a resistance element electrically heated to, and maintained at, the temperature necessary to produce incandescence.

electric filter 1. Device for rejecting or passing a specific band of signal frequencies. 2. See electric-wave filter.

electric-flux density Also called electric-displacement density or electric displacement. At a point, the vector equal in magnitude to the maximum charge per unit area that would appear on one face of a thin metal plate introduced in the electric field at that point. The vector is normal to the plate from the negative to the positive face.

electric force Electric field intensity measured in dynes.

electric furnace A furnace in which electric arcs provide the source of heat.

electric generator A machine that transforms mechanical power into electrical power.

electric governor-controlled series-wound motor A series-wound motor having an electric speed governor connected in series with the motor circuit. The governor is usually built into the motor.

electric-heat soldering Soldering by heating the joint with an electric current.

electric hygrometer An instrument for indicating humidity by electric means. Its operation depends on the relationship between the electric conductance and moisture content of a film of hygroscopic material.

electric hysteresis Internal friction in a dielectric field (e.g., the paper or mica dielectric of a capacitor in an ac circuit). The resultant heat generated can eventually break down the dielectric and cause the capacitor to fail.

electrician A person engaged in designing, making, or repairing electric instruments or machinery. Also, one who sets up an electrical installation.

electric image The electrical counterpart of an object; i.e., the fictitious distribution of the same amount of electricity that is actually distributed on a nearby object.

electricity 1. The property of certain particles to possess a force field that is neither gravitational nor nuclear. The type of force field associated with electrons is defined as negative and that associated with protons and positrons as positive. The fundamental unit is the charge of an electron: 1.60203 × 10^–19 coulomb. Electricity can be further classified as static electricity or dynamic electricity. Static electricity in its strictest sense refers to charges at rest, as opposed to dynamic electricity, or charge in motion. Static electricity is sometimes used as a synonym for triboelectricity or frictional electricity. 2. A basic property of all matter, which consists of negative and positive charges (electrons and protons) that attract each other. 3. The potential energy of electrons at rest. 4. The kinetic energy of electrons in motion. 5. A manifestation of free electrons that can be generated by induction, friction, or chemical action. It is recognized by its magnetic, chemical, and radiant effects.

electric lamp Any lamp whose emission of radiant energy is dependent on the passage of an electrical current through the emissive medium.

electric light Light produced by an electric lamp.

electric lines of force In an electric field, curves whose tangents at any point give the direction of the fields at that point.

electric meter A device that measures and registers the amount of electricity consumed over a certain period of time.

electric mirror See dynode.

electric moment For two charges of equal magnitude but opposite polarities, a vector equal in magnitude to the product of the magnitude of either charge by the distance between the centers of the two charges. The direction of the vector is from the negative to the positive charge.

electric motor A device that converts electrical energy into rotating mechanical energy.

electric network A combination of any number of electric elements, having either lumped or distributed impedances, or both.

electric oscillations The back-and-forth flow of electric charges whenever a circuit containing inductance and capacitance is electrically disturbed.

electric potential A measure of the work required to bring a unit positive charge from an infinite distance or from one point to another (the difference of potential between two points).

electric precipitation The collecting of dust or other fine particles floating in the air. This is done by inducing a charge in the particles, which are then attracted to highly oppositely charged collector plates.

electric probe A rod inserted into an electric field during a test to detect dc, audio, or rf energy.

electric reset A qualifying term indicating that the contacts of a relay must be reset electrically to their original positions following an operation.

electric robot Programmable machine that is powered by servomotors or stepping motors.

electric service panel The main cabinet where electricity is brought into a building, then distributed to branch circuits. The panel usually contains the main circuit breaker for shutting down the entire system, and circuit breakers or fuses for shutting down each independent circuit.

electric shield A housing, usually aluminum or copper, placed around a circuit to provide a low-resistance path to ground for high-frequency radiations and thereby prevent interaction between circuits.

electric strain gage A device that detects the change in shape of a structural member under load and causes a corresponding change in the flow of current through the device.

electric strength The maximum electric charge a dielectric material can withstand without rupturing. See also dielectric strength; insulating strength. The value obtained for the electric strength will depend on the thickness of the material and on the method and conditions of test.

electric stroboscope An instrument for observing or for measuring the speed of rotating or vibrating objects by electrically producing periodic changes in the intensity of light used to illuminate the object.

electric tachometer A tachometer (rpm indicator) that utilizes voltage or electrical impulses.

electric telemeter A system consisting of a meter that measures a quantity, a transmitter that sends the information to a distant station, and a receiver that indicates or records the quantity measured.

electric transcription In broadcasting, a disc recording of a message or a complete program.

electric transducer A device actuated by electric waves from one system and supplying power, also in the form of electric waves, to a second system.

electric tuning A system by which a radio receiver is tuned to a station by pushing a button (instead of, say, turning a knob).

electric vector 1. A component of the electromagnetic field associated with electromagnetic radiation. The component is of the nature of an electric field. The electric vector is supposed to coexist with, but act at right angles to, the magnetic vector. 2. The electric field associated with an electromagnetic wave and thus with a light wave. The electric vector specifies the direction and amplitude of this electric field.

electric watch A timepiece in which a battery replaces the mainspring as the prime energy source of the watch, and in which an electromagnet impels the balance wheel through a mechanical switching-contact arrangement.

electric wave Another term for the electromagnetic wave produced by the back-and-forth movement of electric charges in a conductor.

electric-wave filter Also called electric filter. 1. A device that separates electric waves of different frequencies. 2. A frequency-selective device, usually passive, made up of resistance, capacitance, and inductance elements having signal transmission characteristics that are a function of frequency. Basically, filters are used to pass desired signals and reject unwanted or interfering signals. Bandpass filters are used when the desired signals encompass a frequency band that does not contain any unwanted signals.

electrification 1. The process of establishing an excess of positive or negative charges in a material. 2. The process of applying a voltage to a component or device.

electrification time The time during which a steady direct potential is applied to electrical insulating materials or before the current is measured.

electroacoustic Pertaining to a device (e.g., a speaker or a microphone) that involves both electric current and sound-frequency pressures.

electroacoustic device One that employs phonon propagation or vibrations of a material’s crystal lattice structure as the basic energy transport mechanism. Electrical energy is converted into acoustic energy by the material’s piezoelectric properties.

electroacoustic transducer A device that receives excitations from an electric system and delivers an output to an acoustic system, or vice versa. A speaker is an example of the first, and a microphone is an example of the second.

electroanalysis The process of determining the quantity of an element or compound in an electrolyte solution by depositing the element or compound on an electrode by electrolysis.

electrobiology The science concerned with electrical phenomena of living creatures.

electrobioscopy The application of a voltage to produce muscular contractions.

electrocardiogram Abbreviated EKG or ECG. 1. Essentially an electromyogram of the heart muscle. All muscular activity in the body is characterized by the discharge of polarized cells, the aggregate current from which causes a voltage drop that can be measured on the skin. A changing emf will appear between electrodes connected to the arms, legs, and chest, which rises and falls with heart action such that the period of the resulting waveform is the time between heartbeats. Various positive and negative peaks within one cycle of this waveform have been lettered P, Q, R, S, and T, a notation that aids in subsequent analysis and diagnosis. 2. A hardcopy record of heart action potentials obtained by measuring instantaneous potential differences at the surface of the body. In general, the recording describes the depolarization of myocardial muscle cell masses, providing a graphic, but indirect, view of the heart’s competence. 3. Graphic tracing of the electric current that is produced by the rhythmic contraction of the heart muscle. Visually, a periodic wave pattern is produced. Changes in the wave pattern may appear in the course of various heart diseases; the tracing is obtained by applying electrodes on the skin of the chest and limbs.

electrocardiograph A medical instrument for detecting irregularities in the action of a human heart. It measures the changes in voltage occurring in the human body with each heartbeat. Abbreviated EKG or ECG.

electrocardiography Recording and interpretation of the electrical activity of the heart. The voltage generated by the heart is picked up by surface electrodes on the limbs and chest, amplified, and applied to a strip-chart recorder.

electrocardiophonograph An instrument that records heart sounds.

electrochemical cell An electrochemical system consisting of an anode and a cathode in metallic contact and immersed in an electrolyte. The anode and cathode may be different metals or dissimilar areas on the same metal surface.

electrochemical deterioration A process in which autocatalytic electrochemical reactions produce an increase in conductivity and in turn ultimate thermal failure.

electrochemical device A device that operates on both electrical and chemical principles, e.g., a lead-acid storage battery.

electrochemical diffused-collector transistor See EDCT.

electrochemical equivalent The weight of an element, compound, radical, or ion involved in a specified electrochemical reaction during passage of a specified quantity of electricity such as a coulomb.

electrochemical junction transistor A junction transistor produced by etching an n-type germanium wafer on opposite sides with jets of a salt solution such as indium chloride.

electrochemical potential Also called electrochemical tension. The partial derivative of the total electrochemical free energy of the system with respect to the number of moles of the constituent except that it includes the electrical as well as the chemical contributions to the free energy.

electrochemical recording A recording made by passing a signal-controlled current through a sensitized sheet of paper. The paper reacts to the current and thereby produces a visual record.

electrochemical tension See electrochemical potential.

electrochemical transducer A device that uses a chemical change to measure the input parameter, and the output of which is a varying electrical signal proportional to the measurand.

electrochemical valve Electric valve consisting of a metal in contact with a solution or compound, across the boundary of which current flows more readily in one direction than in the other direction and in which the valve action is accompanied by chemical changes.

electrochemistry 1. That branch of science concerned with reciprocal transformations of chemical and electrical energy. This includes electrolysis, electroplating, the charge and discharge of batteries, etc. 2. The study of the reversible conversion of chemical energy into electrical energy. Electroplating is an electrochemical process.

electrochromic display A passive solid-state display that is made from a material whose light-absorption properties are changed by an externally applied electric field. Ordinarily electrochromic materials do not absorb light in the visible range of the spectrum, so they are completely transparent. When a moderate electric field is applied, the material develops an absorption band in the visible spectrum and takes on a color that remains even after the electric field is removed and lasts from minutes to months. The color change can be reversed and the display returned to its original state when the polarity of the applied electric field is simply reversed.

electrocoagulation The process of solidifying tissue by means of a high-frequency electrical current.

electrocution Killing by means of an electric current.

electrode 1. In an electronic tube, the conducting element that does one or more of the following: emits or collects elections or ions, or controls their movement by means of an electric field on it. 2. In semiconductors, the element that does one or more of the following: emits or collects electrons or holes, or controls their movements by means of an electric field on it. 3. In electroplating, the metal being plated. 4. A conductor by means of which a current passes into or out of a fluid or an organic material, such as human skin; often one terminal of a lead. 5. A metallic conductor such as in an electrolytic cell, in which conduction by electrons is changed to conduction by ions or other charged particles. 6. A conductor, not necessarily metal, through which a current enters or leaves an electrolytic cell, arc, furnace, vacuum tube, gaseous discharge tube, or any conductor of the nonmetallic class. 7. That part of a semiconductor device providing the electrical contact between the specified region of the device and the lead to its terminal. 8. In a spark plug, the center rod passing through the insulator forms one electrode. The rod welded to the shell forms another. They are referred to as the center and side electrodes. 9. A conducting element at whose surface electricity passes into another conducting medium.

electrode admittance The alternating component of the electrode current divided by that of the electrode voltage (all other electrode voltages maintained constant).

electrode capacitance The capacitance between one electrode and all the other electrodes connected together.

electrode characteristic The relationship, usually shown by a graph, between the electrode voltage and current, all other electrode voltages being maintained constant.

electrode conductance The quotient of the in-phase component of the electrode alternating current divided by the electrode alternating voltage, all other electrode voltages being maintained constant. This is a variational and not a total conductance.

electrode current Current passing into or out of an electrode.

electrode dark current Also called dark current. 1. In phototubes, the component of electrode current that flows in the absence of ionizing radiation and optical photons. 2. The current that flows in a photodetector when there is no incident radiation on the detector.

electrode dissipation The power that an electrode dissipates as heat when bombarded by electrons and/or ions and radiation from nearby electrodes.

electrode drop The voltage drop produced in an electrode by its resistance.

electrode impedance The reciprocal of electrode admittance.

electrode inverse current Current through a tube electrode in the direction opposite to that for which the tube was designed.

electrodeless discharge A luminous discharge produced by means of a high-frequency electric field in a gas-filled glass tube that has no internal electrodes.

electrodeless discharge tube Abbreviated EDT. A device consisting of an airtight quartz tube that holds the material to be analyzed. When a high-frequency electrostatic field, generated by microwaves, is applied to the tube, it emits energy of a wavelength identical with that of the contained material.

electrodeposition Also called electrolytic deposition. See also electroplating.

electrode potential 1. The instantaneous voltage on an electrode. Its value is usually given with respect to the cathode of a vacuum tube. 2. The difference in potential between an electrode and the immediately adjacent electrolyte referred to some standard electrode potential as zero. 3. The potential in volts that an electrode has when immersed in an electrolyte, compared to the zero potential of a hydrogen electrode. The potential depends on the material of which the electrode is made.

electrode reactance The imaginary component of electrode impedance.

electrode resistance The reciprocal of electrode conductance. It is the effective parallel resistance, not the real component of electrode impedance.

electrodermography The recording of the electrical resistance of the skin, which is a sensitive indicator of the activity of the autonomic nervous system.

electrode voltage The voltage between an electrode and the cathode or a specified point of a filamentary cathode. The terms grid voltage, anode voltage, plate voltage, etc., designate the voltage between these electrodes and the cathode. Unless otherwise stated, electrode voltages are measured at the available terminals.

electrodialytic process A process for producing fresh water by using a combination of electric current and two types of chemically treated membranes.

electrodynamic Pertaining to electric current, electricity in motion, and the actions and effects of magnetism and induction.

electrodynamic braking A method of stopping a tape-deck motor gently by the application of a predetermined voltage to the motors.

electrodynamic instrument An instrument that depends for its operation on the reaction between the current in one or more moving coils and the current in one or more fixed coils.

electrodynamic machine Electric generator or motor in which the output load current is produced by magnetomotive currents generated in a rotating armature.

electrodynamics 1. The science dealing with the various phenomena of electricity in motion, including interactions of currents with each other, with their associated magnetic fields, and with other magnetic fields. 2. The study of the generation of electromagnetic power by radiation from high-energy beams.

electrodynamic speaker A speaker consisting of an electromagnet called the field coil, through which a direct current flows.

electrodynamometer 1. An instrument for detecting or measuring an electric current by determining the mechanical reactions between two parts of the same circuit. 2. A meter movement consisting of a rotatable (moving) wire coil suspended between two fixed (field) wire coils. The three coils can be connected in various configurations, so that rotation of the moving coil is proportional to applied ac or dc voltage or current, to power, power factor, etc.

electroencephalogram 1. A waveform obtained by plotting brain voltages (available between two points on the scalp) against time. An electroencephalogram is not necessarily a periodic function, although it can beparticularly if the patient is unconscious. These voltages are of extremely low level and require recording apparatus that displays excellent noise rejection. 2. The tracing of brain waves made by an electroencephalograph.

electroencephalograph Abbreviated EEG. An instrument for measuring and recording the rhythmically varying potentials produced by the brain by the use of electrodes applied to the scalp.

electroencephalography 1. Recording and interpretation of the electrical activity of the brain. Voltage (typically 50 microvolts) picked up by electrodes on the scalp is amplified and applied to a strip-chart recorder. 2. Recording of electric currents developed in the brain by means of electrodes applied to the scalp, to the surface of the brain, or placed within the substance of the brain.

electroencephaloscope An instrument for detecting brain potentials at many different sections of the brain and displaying them on a cathode-ray tube.

electroexplosive device See EED.

electrofluid dynamics generator Abbreviated EFD. A generator in which the only moving parts are wind-driven charged particles. Their movement from electrode to electrode is analogous to the spinning of an armature. Ideally suited for use at sea or at the seaside, bladeless windmills could be used anywhere there is a source of moisture. Principal advantages of the concept include efficiency and low cost.

electroforming Also called electrodeposition and electroplating. 1. Making a metal object by using electrolysis to deposit a metal on an electrode. 2. Creating a pn junction by passing a current through point contacts on a semiconductor. 3. The production or reproduction of articles by electrodeposition on a mandrel or mold that is subsequently separated from the deposit. 4. The process of depositing a substance on an electrode by electrolysis, as in electroplating, electroforming, electrofining, or electrotinning.

electroforming process An electrochemical process of metal fabrication using an electrolyte, an anode to supply the metal, and a control of the electrical current and of the deposition of metal on the matrix of a reflector.

electrogalvanizing Electrodeposition of zinc coatings.

electrogastrogram The graphic record that results from synchronous recording of the electrical and mechanical activity of the stomach.

electrograph 1. A plot, graph, or tracing made by means of the action of an electric current on sensitized paper or other material, or by means of an electrically controlled stylus or pen. 2. Equipment for facsimile transmission.

electrographic process See dielectric process.

electrographic recording Also called electrostatography. The producing of a visible record by using a gaseous discharge between two or more electrodes to form electrostatically charged patterns on an insulator. See also electrostatic electrography.

electrokinetics The branch of physics concerned with electricity in motion.

electroless deposition The deposition of conductive material from an autocatalytic plating solution without application of electrical current.

electroless plating 1. A method of metal deposition by means of a chemical reducing agent present in the processing solution. The process is further characterized by the catalytic nature of the surface, which enables the metal to be plated to any thickness. 2. A chemical process by which certain metals can be plated without electrical current. Tin may be plated onto copper in this manner. 3. The controlled autocatalytic reduction of a metal ion on certain catalytic surfaces.

electroluminescence 1. Luminescence resulting from a high-frequency discharge through a gas or from application of an alternating current to a layer of phosphor. 2. Direct conversion of electrical energy into light energy in a liquid or solid; for example, photoemission as a result of electron-hole recombination in a pn junction. This is the mechanism employed by the injection laser. The standard abbreviation for the effect is written EL. (This process is not to be confused with the ordinary tungsten filament bulb, where there is an intermediate stage of heat, making the process thermoluminescent.) 3. Light produced in a phosphor that is in an alternating electric field. Consists of a phosphor a few mils thick placed between two metal films, one of which is transparent. Alternating current is applied to the plates through a current-limiting resistor.

electroluminescent display 1. A display, designated EL, whose segments or elements consist of transparent conductive electrodes separated by a dielectric containing a luminescent phosphor. Application of ac voltage to opposing electrodes causes the dielectric between them to glow with a characteristic blue-green light. 2. The utilization of the light produced when electrical energy is directly converted into light within devices used for visual readout displays or as complex logic-circuit elements. The display devices may be flat, giving a wide viewing angle without parallax, and may have low power needs. Can yield blue, green, yellow, and white colors.

electroluminescent lamp A lamp in the shape of a panel that is decorative as well as illuminative. It consists primarily of a capacitor having a ceramic dielectric with electroluminescent phosphor. The amount of illumination is determined by the voltage across the layer and by the frequency applied to it.

electroluminescent-photoconductive image intensifier A panel, made up of electroluminescent and photoconductive (EL-PC) layers, used as either a positive or negative image intensifier, depending on amplitude and phase of its two power supply voltages. The photoconductive layer receives the image and converts it to electrical signals; subsequently, the electroluminescent layer converts the signals to visible, brighter light.

electrolysis 1. The process of changing the chemical composition of a material (called the electrolyte) by sending an electric current through it. 2. The decay of an underground structure by chemical action due to stray electrical currents. 3. Production of chemical changes of the electrolyte by the passage of current through an electrochemical cell. 4. Conduction of an electric current through a chemical compound in its natural state, solution or as a molten, to decompose the compound.

electrolyte 1. A substance in which the conduction of electricity is accompanied by chemical action. 2. The paste that forms the conducting medium between the electrodes of a dry cell, storage cell, or electrolytic capacitor. 3. A substance that, when dissolved in a suitable liquid (often water), dissociates into ions, thus rendering the liquid electrically conducting. 4. The current-conducting substance (liquid or solid) between two capacitor electrodes, at least one of which is covered by a dielectric film. 5. A conducting medium in which current is accompanied by movement of matter. Most often an aqueous solution of acids, bases, or salts, but includes many other media, such as fused salts, ionized gases, some solids, etc. 6. A substance that is capable of forming a conducting liquid medium when dissolved or melted.

electrolyte conductivity Also called specific conductance. A measure of the ability of a solution to carry an electric current. Defined as the reciprocal of the resistance in ohms of a 1-cm cube of the liquid at a specified temperature. The units of specific conductance are the reciprocal ohm-cm (or siemens/cm) and one millionth of this. High-quality condensed steam and distilled or demineralized water have specific conductances at room temperatures as low as or lower than 1 microsiemens/cm.

electrolyte recording A form of facsimile recording in which ionization causes a chemically moistened paper to undergo a change.

electrolytic 1. Pertaining to or made by electrolysis; deposited by electrolysis; pertaining to or containing an electrolyte. 2. Said of an electrical device that contains an electrolyte.

electrolytic capacitor 1. A capacitor consisting of two conducting electrodes, with the anode having a metal oxide film formed on it. The film acts as the dielectric or insulating medium. The capacitor is operable in the presence of an electrolyte, usually an acid or salt. Generally used for filtering, bypassing, coupling, or decoupling. 2. A capacitor in which the dielectric is a film of oxide electrolytically deposited on a plate or slug of aluminum or tantalum. The thinness of the film permits a high capacitance-to-volume ratio. The oxide acts as a dielectric in one direction only. The device is, therefore, polarized. (A nonpolarized electrolytic capacitor is, in effect, two polarized types in series with their like terminals connected together.) 3. A fixed capacitor, having a relatively high capacitance-to-volume ratio due to a very thin electrically formed, nonconducting chemical dielectric (oxide) film. 4. A capacitor in which the electrolytically formed oxide layer on the surface of the anode serves as a dielectric, with a solid or nonsolid electrolyte forming the cathode, thus giving the capacitor polar properties.

electrolytic capacitor paper Very pure, porous paper, 17 to 100 micrometers thick, used to separate the metallic electrodes in electrolytic capacitors.

electrolytic cell 1. In a battery, the container, two electrodes, and the electrolyte. 2. A unit apparatus in which electrochemical reactions are produced by applying electrical energy, or which supplies electrical energy as a result of chemical reactions and which includes two or more electrodes and one or more electrolytes contained in a suitable vessel.

electrolytic cleaning A process of removing soil, scale, or corrosion products from a metal surface by subjecting it as an electrode to an electric current in an electrolytic bath.

electrolytic conduction The flow of current between electrodes immersed in an electrolyte. It is caused by the movement of ions from one electrode to the other when a voltage is applied between them.

electrolytic corrosion Corrosion by means of electrochemical erosion. See corrosion.

electrolytic deposition See electrodeposition.

electrolytic development The method of developing a photographic image by means of an applied electric field. The systems used include electrolysis and photoconductive systems.

electrolytic dissociation The breaking up of molecules into ions in a solution.

electrolytic interrupter A device that is tilted to change the current through it.

electrolytic iron Iron obtained by an electrolytic process. The iron possesses good magnetic qualities and is exceptionally free of impurities.

electrolytic plating A method of metal deposition employing the work or cathode, the anode, the electrolyte, a solution containing dissolved salts of the metal to be plated, and a source of direct current. The anode metal is dissolved by chemical and electrical means; subsequently, cations are deposited onto the cathode. Electric current is the reducing agent. Copper, nickel, chromium, zinc, brass, cadmium, tin, gold, and silver are the metals most commonly electroplated.

electrolytic potential The difference in potential between an electrode and the immediately adjacent electrolyte, expressed in terms of some standard electrode difference.

electrolytic rectifier A rectifier consisting of metal electrodes in an electrolyte, in which rectification of alternating current is accompanied by electrolytic action. A polarization film formed on one of the electrodes permits current in one direction but not in the other.

electrolytic refining The refining or purifying of metals by electrolysis.

electrolytic shutter A high-speed shutter, similar to a Kerr cell, that uses the birefringence produced in a liquid during the passage of an electric current through it to change the liquid’s optical transmission characteristics.

electrolytic switch A switch having two electrodes projecting into a chamber containing a precisely measured quantity of a conductive electrolyte, leaving an air bubble of predetermined width. When the switch is tilted from true horizontal, the bubble shifts position and changes the amount of electrolyte in contact with the electrodes, thereby changing the amount of current passed by the switch. Used as a leveling switch in gyro systems.

electrolyzer An electrolytic cell that produces alkalies, metals, chlorine, or other allied products.

electromagnet 1. A temporary magnet consisting of a solenoid with an iron core. A magnetic field exists only while current flows through the solenoid. 2. A magnet, consisting of a solenoid with an iron core, that has a magnetic field existing only during the time of current flow through the coil. 3. A coil of wire, usually wound on an iron core, that produces a strong magnetic field when current is sent through the coil. 4. A magnet created by inserting a suitable metal core within or near a magnetizing field that is usually formed by passing electric current through a coil of insulated wire. 5. A soft iron core that becomes a magnet temporarily when current flows through a coil of wire that surrounds it.

electromagnetic 1. Having both magnetic and electric properties. 2. Pertaining to the mutually perpendicular electric and magnetic fields associated with the movement of electrons through conductors, as in an electromagnet. 3. Pertaining to the combined electric and magnetic fields associated with radiation or with movements of charged particles. 4. Pertaining to or caused by the combined electric and magnetic fields that are always associated with an electric current. 5. Pertaining to the relationship between currents and magnetic fields.

electromagnetic amplifying lens A system made up of a large number of waveguides symmetrically arranged with respect to an excitation medium so that they are excited with equal amplitude and phase in order to provide an effective gain in energy.

electromagnetic bonding Method for joining thermoplastics in which a metallic preform is placed in the joint area to convert electromagnetic energy into heat for fusion bonding.

electromagnetic cathode-ray tube A cathode-ray tube that uses electromagnetic deflection to deflect the electron beam.

electromagnetic communications The electromagnetic wave conductor is space itself. The electromagnetic frequencies available today for communications fall into two categories: frequencies that form “wireless” communications (such as visual light of fairly high frequency), and frequencies that humans use for wireless communications (such as radio, shortwave, and microwave transmitting, of relatively lower frequencies). In communicating by radio, shortwave, and microwave frequencies, translators similar in principle to those used in electrical communications are needed, although the equipment requirement increases.

electromagnetic compatibility Abbreviated EMC. 1. The ability of electronic devices and communications equipment, subsystems, and systems to operate in their intended environments without suffering or causing unacceptable degradation of performance as a result of unintentional electromagnetic radiation or response. 2. A directive that specifies the acceptable limits for electromagnetic emissions from an electronic device, and how much electromagnetic interference the device should tolerate. 3. Abbreviation for electronic message center (Ford Motor). Digital dashboard electronics displaying digital readouts of speed, miles, fuel, clock, etc.

electromagnetic complex The electromagnetic configuration of an installation, including all radiators of significant amounts of energy.

electromagnetic coupling The mutual relationship between two separate but adjacent wires when the magnetic field of one induces a voltage in the other.

electromagnetic crack detector An instrument for detecting hidden cracks in iron or steel objects by magnetic means.

electromagnetic deflection The deflection of an electron stream by means of a magnetic field. In a television receiver, the magnetic field for deflecting the electron beam horizontally and vertically is produced by two pairs of coils, called the deflection yoke, around the neck of the picture tube.

electromagnetic deflection coil A coil around the neck of a CRT, for deflecting the electron beam.

electromagnetic delay line A delay line whose operation is based on the time of propagation of electromagnetic waves through distributed or lumped capacitance and inductance.

electromagnetic energy Forms of radiant energy, such as radio waves, heat waves, light waves, X-rays, gamma rays, and cosmic rays.

electromagnetic environment The rf field or fields existing in an area or desired in an area to be shielded.

electromagnetic field 1. The field of influence produced around a conductor by the current flowing through it. 2. A rapidly moving electric field and its associated magnetic field. The latter is perpendicular to both the electric lines of force and their direction. 3. The field associated with radio or light waves, consisting of a magnetic and an electric field at right angles to each other and to the direction of wave propagation.

electromagnetic focusing In a television picture tube, the focusing produced by a coil mounted on the neck. Direct current through the coil produces magnetic field lines parallel to the tube axis.

electromagnetic horn A horn-shaped structure that provides highly directional radiation of radio waves in the 100-megahertz or higher frequency range.

electromagnetic induction The voltage produced in a coil as the number of magnetic lines of force (flux linkages) passing through the coil changes.

electromagnetic inertia 1. The characteristic delay of a current in an electric circuit in reaching its maximum or zero value after application or removal of the source voltage. 2. The property of self-induction.

electromagnetic interference Abbreviated EMI. 1. Unintentional interfering signals generated within or external to electronic equipment. Typical sources could be power-line transients, noise from switching-type power supplies, and/or spurious radiation from oscillators. EMI is suppressed with power-line filtering, shielding, etc. EMI suppression requirements are frequently specified for military equipment. 2. Electromagnetic phenomena which, either directly or indirectly, can contribute to a degradation in performance of an electronic receiver or system. (The terms radio interference, radio-frequency interference, noise, emi, and rfi have been employed at various times in the same context.) 3. Disturbances caused by electromagnetic waves (radio, heat, light, etc.) that can impair the reception of the desired transmitted signal. 4. Unwanted electromagnetic emissions, generated by lightning or by electronic or electrical devices, that degrade the performance of another electronic device. Interference may be reduced by shielding. Maximum acceptable levels of EMI from electronic devices are detailed by the Federal Communications Commission.

electromagnetic lens 1. An electron lens in which the electron beams are focused electromagnetically. 2. An electromagnet that produces a suitably shaped magnetic field for the focusing and deflection of charged particles in electron-optical systems. 3. An electron lens consisting of a homogeneous axial electric field and a magnetic field, used in high-quality image tubes for high MTF and small geometrical distortion requirements.

electromagnetic mirror A surface or region capable of reflecting radio waves, such as one of the ionized layers in the upper atmosphere.

electromagnetic oscillograph An oscillograph in which a mechanical motion is derived from electromagnetic forces to produce a record.

electromagnetic pollution The effects of electromagnetic interference (EMI) produced by human-made apparatus. The seriousness of this interference ranges from annoying interference that affects a radio or television channel to interference that causes failure of an important communication channel or a cardiac pacemaker.

electromagnetic pulse Abbreviated EMP. A reaction of large magnitude resulting from the detonation of nuclear weapons.

electromagnetic radiation 1. That form of energy which is characterized by transversely oscillating electric and magnetic fields and which propagates at velocity c in free space. At a sufficient distance from the source, the electric-field vector and the magnetic field vector are at right angles to each other, forming a right-handed (coordinate) system. In an ionized medium, a longitudinal component may be present. 2. A form of power emitted from vibrating charged particles. A combination of oscillating electric and magnetic fields, electromagnetic radiation propagates through otherwise empty space with the velocity of light. This (constant) velocity equals the alternation frequency multiplied by the wavelength; hence the frequency and wavelength are inversely proportional to each other. The spectrum of electromagnetic radiation is continuous over all frequencies. 3. Abbreviated EMR. When discussing shielding, describes radiation generated by electrical means, ranging from a stationary magnetic or electrostatic field to high-frequency changing fields and transmitted plane waves of radio frequency.

electromagnetic reconnaissance Activity conducted to locate and identify potential hostile sources of electromagnetic radiation, including radar, communication, missile-guidance, and air-navigation equipment.

electromagnetic relay 1. Device that opens or closes contacts by setting “moving” contacts against “fixed” contacts when current passes through an electromagnet. Current sets up a magnetic attraction between the core of the electromagnet and a hinged arm to the tip of which is attached the moving contact. The movement of the arm toward the core of the electromagnet brings moving and fixed contacts together. When current is withdrawn, a spring returns the arm to its original position and the contacts separate. 2. A mechanical switch operated by electric power.

electromagnetic repulsion The repelling action between like poles of electromagnets.

electromagnetics In physics, the branch concerned with the relationships between electric currents and their associated magnetic fields.

electromagnetic spectrum 1. A chart or graph showing the relationships among all known types of electromagnetic radiation classified by wavelengths. 2. The continuous range of frequencies, from 0.1 to 10²² hertz, of which a radiated signal is composed. Spectral dimensions are more conveniently described in terms of wavelength (angstroms), where 1 angstrom is equivalent to 10^–7 mm. The electromagnetic spectrum includes radio-frequency waves, light waves, microwaves, infrared, X-rays (Roentgen rays), and gamma rays. 3. The ordered array of known electromagnetic radiations, extending from the shortest wavelengths, cosmic rays, through gamma rays, X-rays, ultraviolet radiation, visible radiation, and infrared, and including microwave and all other wavelengths of radio energy. 4. The entire range of wavelengths, extending from the shortest to the longest or conversely, that can be generated physically. This range of electromagnetic wavelengths extends almost from zero to infinity and includes the visible portion of the spectrum known as light. See also visible spectrum. 5. The total range of wavelengths or frequencies of electromagnetic radiation, extending from the longest radio waves to the shortest known cosmic rays.

electromagnetic tester A nondestructive test method for engineering materials, including magnetic materials, that uses electromagnetic energy having frequencies less than those of visible light to yield information regarding the quality of the tested materials.

electromagnetic theory The theory of propagation of energy by combined electric and magnetic fields included in Maxwell’s equations.

electromagnetic theory of light The theory that states that electromagnetic and light waves have identical properties.

electromagnetic transduction 1. Conversion of the measurand into the output induced in a conductor by a change in magnetic flux. 2. A wave produced by the oscillation of an electric charge. 3. A wave in which there are both electric and magnetic displacements. 4. A transverse wave associated with the transmission of electromagnetic energy.

electromagnetic-type microphones Microphones in which the voltages are varied by an electromagnet (namely, ribbon or velocity, dynamic or moving-coil, and reluctance or moving-vane microphones).

electromagnetic unit Abbreviated emu. A unit of electricity based primarily on the magnetic effect of an electric current. The fundamental centimeter-gram-second unit is the abampere. Now considered obsolete.

electromagnetic vibrator A mechanical device for interrupting the flow of direct current and thereby making it a pulsating current. This is done where a circuit requires an alternating current to operate. A reed within the vibrator is alternately attracted to two electromagnets.

electromagnetic wave 1. The radiant energy produced by oscillation of an electric charge. It includes radio, infrared, visible and ultraviolet light waves, and X-, gamma, and cosmic rays. 2. A wave in which both electric and magnetic displacement are present. 3. Waves of radiation identified by individual fluctuations of electric and magnetic fields. All such waves propagate at the speed of light in free space, which includes most realistic atmospheric conditions. Three material parameters are necessary and sufficient to describe electromagnetic waves in a given medium: dielectric constant (or permittivity), permeability, and conductivity.

Electromagnetism 1. The magnetic field around a wire or other conductor when, and only when, current passes through it. 2. Magnetism caused by an electric current in a conductor.

electromanometer Instrument used for measuring pressure of gases or liquids by electronic methods.

electromechanical Any device using electrical energy to produce mechanical movement.

electromechanical bell A bell with a prewound spring-driven clapper that is tripped electrically to ring the bell.

electromechanical breakdown A mechanical runaway that occurs when the mechanical restoring force fails to balance the electrical compressive force.

electromechanical chopper See contact modulator.

electromechanical diffused-collector transistor See EDCT.

electromechanical energy Energy present in an induction coil or solenoid.

electromechanical frequency meter A meter that uses the resonant properties of mechanical devices to indicate frequency.

electromechanical recorder A device that transforms electrical signals into equivalent mechanical motion that is transferred to a medium by cutting, embossing, or writing.

electromechanical timer Usually refers to a motor-driven timer, with or without an electrically operated clutch. Can also apply to pneumatic and thermal timers, or slow pull-in or drop-out relays.

electromechanical transducer A device that transforms electrical energy into mechanical energy and vice versa. A speaker is an example of the first, and a microphone of the second.

electromechanics That branch of electrical engineering concerned with machines producing or operated by electric currents.

electrometallurgy That branch of science concerned with the application of electrochemistry to the extraction or treatment of metals.

electrometer 1. An electrostatic instrument that measures a potential difference or an electric charge by the mechanical force exerted between electrically charged surfaces. 2. A dc voltmeter with an extremely high input resistance, usually around 10¹⁰ megohms, as opposed to 10 megohms or less for a conventional type.

electrometer amplifier An amplifier circuit having sufficiently low current drift and other noise components, sufficiently low amplifier input-current offsets, and adequate power and current sensitivities to be usable for measuring current variations of considerably less than 10^–12 A.

electrometer tube A vacuum tube having a very low control-electrode conductance, to facilitate the measurement of extremely small direct currents and voltages.

electromigration Motion of ions of a metal conductor (such as aluminum) in response to the passage of high current through it. Such motion can lead to the formation of “voids” in the conductor, which can grow to a size such that the conductor is unable to pass current. Electromigration is aggravated at high temperature and high current density and therefore is a reliability “wear-out” process. Electromigration is minimized by limiting current densities and by adding metal impurities such as copper or titanium to aluminum.

electromotive force Abbreviated emf. 1. The force that causes electricity to flow when there is a difference of potential between two points. The unit of measurement is the volt. 2. Electrical pressure at the source. Not to be confused with potential difference, which is the voltage developed across a resistance or impedance due to current flowing through it. Both are measured in volts. 3. Electric pressure that causes a current to flow in a circuit; it is the energy put into the circuit by the source per unit electric charge that it supplies to the circuit. The unit of emf is the volt, being the electromotive force required to cause a current of 1 ampere to flow in a resistance of 1 ohm. 4. The difference of electrical potential found across the terminals of a source of electrical energy; more precisely, the limit of the potential difference across the terminals of a source as the current between the terminals approaches zero.

electromotive force series A list of elements arranged according to their standard electrode potentials, with noble metals, such as gold, being positive and active metals, such as zinc, being negative.

electromotive series A list of metals arranged in decreasing order of their tendency to pass into ionic form by losing electrons.

electromyogram A waveform of the contraction of a muscle as a result of electrical stimulation. Usually the stimulation comes from the nervous system (normal muscular activity). The record of potential difference between two points on the surface of the skin resulting from the activity or action potential of a muscle.

electromyograph An instrument for measuring and recording potentials generated by muscles.

electromyography Abbreviated EMG. Recording and interpretation of the electrical activity of muscle tissue. A single electrical spike potential is generated when a muscle fiber contracts. The magnitude of the spike potentials is roughly proportional to the amount of muscular tension. Surface detecting electrodes (for many muscle fibers) or needle electrodes (for one or a few fibers) provide a signal that is amplified and displayed on a cathode-ray tube.

electron An elementary atomic particle that carries the smallest negative electric charge (1.6 × 10^–19 coulombs). Electrons are light in mass (1/1840 of the mass of the hydrogen atom, or 9.107 × 10^–28 gram), highly mobile, and orbit the nucleus of an atom. Electrons are responsible for the bonds between atoms. Positive electrons, or positrons, also exist.

electronarcosis 1. The induction of unconsciousness by passage of a weak current through the brain. 2. Anesthesia induced by the passage of a precisely controlled electric current through the brain.

electron attachment Process by which an electron is attached to a neutral molecule to form a negative ion. Often characterized by the attachment coefficient η, which is the number of attachments per centimeter of drift. Also characterized by the ratio h = σ/θ, where σ is the attachment cross section and θ the total cross section.

electron avalanche The chain reaction started when one free electron collides with one or more orbiting electrons and frees them. The free electrons then free others in the same manner, and so on.

electron band A spectrum band composed of molecules that is usually found in the visible or the ultraviolet because of the electron transition taking place with the molecule.

electron beam 1. A narrow stream of electrons moving in the same direction under the influence of an electric or magnetic field. 2. A stream of electrons, emitted by a single source, that move in the same direction and at the same speed. 3. The electrons emitted by the cathode in a picture tube and focused into a beam that is deflected line by line across the phosphor screen to produce an image.

electron-beam bonding Process using a stream of electrons to heat and bond two conductors within a vacuum.

electron-beam evaporation An evaporation technique in which the evaporant is heated by electron bombardment.

electron-beam generator A velocity-modulated generator, such as a klystron tube, used to generate extremely high frequencies.

electron-beam gun A device generally used in a cathode-ray or camera tube to emit a stream of electrons moving at uniform velocity in a straight line. It consists of an emitting cathode and an anode, with an aperture for passage of some of the electrons.

electron-beam instrument Also called a cathode-ray instrument. An instrument in which a beam of electrons is deflected by an electric or magnetic field (or both). Usually the beam is made to strike a fluorescent screen so the deflection can be observed.

electron-beam machining A process in which controlled electron beams are used to weld or shape a piece of material.

electron-beam magnetometer An instrument that measures the intensity and direction of magnetic forces by the immersion of an electron beam into the magnetic field.

electron-beam mode discharge Abbreviated ebmd. A form of discharge produced by a perforated-wall hollow cathode operating under conditions of pressure, voltage, and geometry usually associated with the abnormal glow discharge.

electron-beam recording The recording of the information contained in a modulated electron beam onto photographic or silicon-resin-coated materials.

electron-beam tube An electron tube that depends for its operation on the formation and control of one or more electron beams.

electron-beam welding 1. The process of using a focused beam of electrons to heat materials to the fusion point. 2. Process in which a welder generates a stream of electrons traveling at up to 60 percent of the speed of light. It focuses the beam to a small, precisely controlled spot in a vacuum and converts the kinetic energy into an extremely high temperature on impact with the work piece.

electron-bombarded semiconductor amplifier Abbreviated EBS amplifier. An amplifier consisting of an electron-gun modulation system, semiconductor target, and output coupling network all within a glass or ceramic envelope. The semiconductor target is a pair of silicon diodes, each consisting of two metallic electrodes with a pn junction under the top contact. Amplifier operation is based on the fact that a modulated electron beam can control the current in a reverse-biased semiconductor junction.

electron-bombardment-induced conductivity In a multimode display storage tube, a process by which the image on the surface of the cathode-ray tube is erased by the use of an electron gun.

electron charge Also called elementary charge. The charge of a single electron. Its value is 1.602189 × 10^–19 coulomb. The fundamental unit of electrical charge.

electron-coupled oscillator Abbreviated ECO. A circuit using a multigrid tube in which the cathode and two grids operate as a conventional oscillator and the electron stream couples the plate-circuit load to the oscillator.

electron coupling In vacuum (principally multigrid) tubes, the transfer of energy between electrodes as electrons leave one and go to the other.

electron device Any device in which the passage of electrons through a vacuum, gas, or semiconductor is the device’s principal means of conduction.

electron diffraction 1. The phenomenon or the technique of producing diffraction patterns through the incidence of electrons on matter. 2. The bending of an electron stream that occurs when the stream travels through a medium such as very thin metal foil.

electron-diffraction camera A special evacuated camera equipped with means for holding a specimen and bombarding it with a sharply focused beam of electrons. A cylindrical film placed around the specimen records the electrons that may be scattered or diffracted by it.

electron drift The movement of electrons in a definite direction through a conductor, as opposed to the haphazard transfer of energy from one electron to another by collision.

electronegative Having an electric polarity that is negative.

electronegative developer A developer containing negatively charged toner particles.

electron emission The freeing of electrons into space from the surface of a body under the influence of heat, light, impact, chemical disintegration, or a potential difference.

electron emitter In a cathode tube, the electrode that serves as a source for electrons.

electron filter lens An electrostatic device that uses an electric potential barrier to allow the transmittance of electrons at or above a set level of energy while stopping the passage of those below it.

electron flow The movement of electrons from a negative to a positive point in a metal or other conductor, or from a negative to a positive electrode through a liquid, gas, or vacuum.

electron gun 1. An electrode structure that produces and may control focus and may deflect and converge one or more electron beams. 2. A device for producing and accelerating a beam of electrons. 3. The portion of a TV picture tube or cathode-ray tube that produces the stream of electrons and may also focus and center the stream. 4. The source of the electron beam in a picture tube, comprising a cathode plus several focusing electrodes that collimate and focus the electron beam into a spot on the screen. In a color tube there may be three electron guns usually integrated into a single unit (unitized gun), or a single gun for the three colors.

electronic 1. Pertaining to that branch of science which deals with the motion, emission, and behavior of currents of free electrons, especially in vacuum, gas, or phototubes and special conductors or semiconductors. This is contrasted with electric, which pertains to the flow of large currents in metal conductors. 2. Of or pertaining to devices, circuits, or systems using the principle of electron flow through a conductor. Examples: electronic control, electronic equipment, electronic instrument, electronic circuit.

electronic autopilot An arrangement of gyroscopes, electronic amplifiers, and servomotors for detecting deviations in the flight of an aircraft and applying the required corrections directly to its control cables.

electronic balance Weighing balance that uses forces produced by known currents to balance unknown currents, and thereby unknown weights, very accurately to within parts of a microgram.

electronic “bug” A keying system that converts the Morse signals from a hand key into correctly proportioned and spaced dots and dashes.

electronic bulletin board A shared file where users can enter information for other users to read or download. Many bulletin boards are set up according to general topics and are accessible throughout a network.

electronic calculator Electronic device for arithmetic and logarithmic computations; may also include digital printer and computer.

electronic camouflage Use of electronic means or exploitation of electronic characteristics to reduce, submerge, or eliminate the radar-echoing properties of a target.

electronic carburetor A fuel-metering actuator in which the air/fuel ratio is controlled by continual variations of the metering rod position in response to an electronic control signal.

electronic charge The quantity of charge represented or possessed by one electron. It is equal to 1.602189 × 10^–19 coulomb.

electronic circuit A circuit containing one or more electron tubes, transistors, integrated circuits, magnetic amplifiers, etc.

electronic commutator A type of switch that provides a continuous switching or sampling of a number of circuits by means of a radial-beam electronic tube or electronic switching circuit.

electronic confusion area Amount of space that a target appears to occupy in a radar resolution cell, as it appears to that radar beam.

electronic control Also called electronic regulation. The control of a machine or condition by electronic devices.

electronic control unit See ECU.

electronic counter An instrument capable of counting up to several million electrical pulses per second.

electronic counter-countermeasures Abbreviated ECCM. 1. Equipment and techniques that allow electronic systems such as radar and communication systems to operate effectively while attempts are made to disrupt or jam their operation. 2. That division of electronic warfare involving actions taken to ensure friendly and effective use of the electromagnetic spectrum despite the enemy’s use of electronic warfare. 3. Retaliatory tactics used to reduce the effectiveness of electronic countermeasures.

electronic countermeasures Abbreviated ECM. 1. All measures taken to reduce the effectiveness of enemy electronic systems such as radar and communications. There are two distinct areas: passive measures, or reconnaissance, and active measures, such as jamming. 2. That division of electronic warfare involving actions taken to prevent or reduce an enemy’s effective use of the electromagnetic spectrum. Includes techniques such as chaff and barrage jamming as well as sophisticated methods to deceive the systems without indication to the opposing operators that their systems are being affected. 3. Methods of jamming or otherwise hindering the operation of enemy electronic equipment.

electronic countermeasures control 1. Collection and sorting of large quantities of data for the purpose of measuring and defining radar signals. 2. Examination of the data received in order to determine selection and switching of countermeasure devices with little or no time delay.

electronic coupling The method of coupling electrical energy from one circuit to another through the electron stream in a vacuum tube.

electronic crowbar An electronic switching device generally used in a power supply to divert a fault current from more delicate components until a fuse, circuit breaker, or the like has time to respond.

electronic data exchange See EDI.

electronic data processing Abbreviated EDP. 1. Operations on data carried out mainly by electronic equipment. 2. Use of electronic memories to store, update, and read information automatically, and using that information in accounting, filing, etc. 3. Any computerized information system and the equipment used in that system.

electronic data-processing center Abbreviated EDP center. A place in which is kept automatically operated equipment, including computers, designed to simplify the interpretation and use of data gathered by instrumentation installations or information-collection agencies.

electronic data-processing machine Abbreviated EDPM. A machine or its device and attachments used primarily in or with an electronic data-processing system.

electronic data-processing system Any machine or group of automatically intercommunicating machines capable of entering, receiving, sorting, classifying, computing, and/or recording alphabetical or numerical accounting or statistical data (or all three).

electronic deception Deliberate radiation, reradiation, alteration, absorption, or reflection of electromagnetic radiations in a manner intended to cause the enemy to obtain misleading data or false indications from his electronic equipment. There are two categories of electronic deception: (a) Manipulative deception — the alteration or simulation of friendly electromagnetic radiation to accomplish deception. (b) Imitative deception — the introduction into enemy channels of radiations that imitate the enemy’s own emissions.

electronic device 1. A device in which conduction is principally by the movement of electrons through a vacuum, gas, or semiconductor. 2. An electronic tube or valve, transistor, or other semiconductor device. This definition excludes inductors, capacitors, resistors, and similar components.

electronic differential An input or output type of circuit that only amplifies or responds to the difference of two signals, and does not respond to the signal with respect to ground or a supply voltage.

electronic differential analyzer A form of analog computer using interconnected electronic integrators to solve differential equations.

electronic digital computer A machine that uses electronic circuitry in the main computing element to perform arithmetic and logical operations on digital data (i.e., data represented by numbers or alphabetic symbols) automatically by means of an internally stored program of machine instructions. Such devices are distinguished from calculators, on which the sequence of instructions is externally stored and is impressed manually (desk calculators) or from tape or cards (card-programmed calculators).

electronic efficiency The ratio of (a) the power at the desired frequency delivered by the electron stream to the oscillator or amplifier circuit to (b) the direct power supplied to the stream.

electronic engine control See EEC.

electronic engineering A branch of electrical engineering that applies the principles of electronics to the solution of practical problems. See also electronics.

electronic flash Also called strobe. 1. The firing of special light-producing, high-voltage, gas-filled glass tubes with a high instantaneous surge of current furnished by a capacitor or bank of capacitors that have been charged from a high-voltage source (usually 450 volts or higher). 2. A device that upon command produces a pulse of luminous energy caused by a discharge of electrical energy through a gas. The term usually implies the use of a flash tube and associated power source and trigger circuit.

electronic flash tube See flash tube.

electronic flash unit A small xenon-filled tube with metal electrodes fused into the ends. The gas flashes brilliantly when a capacitor is discharged through the tube. The duration of the flash primarily depends on the capacitance of the capacitor. As a rule of thumb, flash time is approximately equal in microseconds to capacitance in microfarads. Sometimes the flash recurs at a specified frequency, which may reach many thousands per second; such a device is called a strobe unit because it produces stroboscopic effects and makes rapidly moving parts appear to stand still.

electronic frequency synthesizer A device that generates two or more selectable frequencies from one or more fixed-frequency sources.

electronic funds transfer system See EFTS.

electronic gate A device in which diodes and/or transistors provide input-output relations that correspond to a Boolean-algebra function (AND, OR, etc.).

electronic heating Also called high-frequency heating. A method of heating a material by inducing a high-frequency current in it or having the material act as the dielectric between two plates charged with a high-frequency current.

electronic hookup wires Wires used to make the internal connections between the various electrical parts of electronic assemblies.

electronic industries Industrial organizations engaged in the manufacture, design, development, and/or substantial assembly of electronic equipment, systems, assemblies, or the components thereof.

Electronic Industries Association Abbreviated EIA. A trade association of the electronics industry. Some of its functions are the formulation of technical standards, dissemination of marketing data, and the maintenance of contact with government agencies in matters relating to the electronics industry. The association was originally known as the Radio Manufacturers Association (RMA), and later as the Radio-Electronics-Television Manufacturers Association (RETMA).

electronic instrument Any instrument that depends for its operation on the action of either one or more electron devices.

electronic instrument cluster See EIC.

electronic intelligence The technical and intelligence information derived from foreign noncommunications electromagnetic radiations emanating from other than nuclear detonations or radioactive sources.

electronic interference Electrical or electromagnetic disturbances that result in undesired response in electronic equipment.

electronic jamming Intentional radiation, reradiation, or reflection of electromagnetic energy for the purpose of reducing the effectiveness of enemy electromagnetic devices or impairing the use of any electronic devices, equipment, or systems being used by an enemy.

electronic keyboard A keyboard that is used to generate characters through electronic means rather than through mechanical linkages.

electronic keying A method of keying whereby the dots and dashes are produced solely by electronic means.

electronic line scanning Facsimile scanning in which a spot on a cathode-ray tube moves across the copy electronically while the record sheet or subject copy is moved mechanically in a perpendicular direction.

electronic mail Abbreviated e-mail or email. 1. Electronic messages that can be sent over a communications network from one computer to another. 2. Sending messages electronically between computers or terminals.

electronic microphone A device that depends for its operation on the generation of a voltage by the motion of one of the electrodes in a special electron tube.

electronic mine detector See mine detector

electronic multimeter A device employing the characteristics of an electron-tube circuit for the measurement of electrical quantities, at least one of which is voltage or current, on a single calibrated scale.

electronic music The electronic generation and processing of audio signals, or the electronic processing of natural sound, and the manipulation and arrangement of these signals via tape recorders into a finished musical composition.

electronic music synthesizer An audio signal processor that contains sound generators (oscillators) and additional circuitry such as filters to produce familiar sounds, such as those produced by conventional musical instruments, or to create unique sounds and effects.

electronic news-gathering Abbreviated ENG. The use of video cameras, recording, and other ancillary electronic gear to collect news stories for TV airing.

electronic organ The electronic counterpart of the pipe organ. All tones and tone variations, such as vibrato, tremolo, etc., are produced by electronic circuits instead of by pipes.

electronic pacemaker Also called a pacemaker. An electrical device, usually with electrodes planted in the myocardium, that performs the pacing function in a diseased heart no longer capable of pacing itself. Electronic pacemakers can receive power from implanted batteries, radio-frequency signals, biological energy sources, etc.

electronic packaging The coating or surrounding of an electronic assembly with a dielectric compound.

electronic part A basic circuit element that cannot be disassembled and still perform its intended function. Examples of electronic parts are capacitors, connectors, filters, resistors, switches, relays, transformers, crystals, electron tubes, and semiconductor devices.

electronic photometer Also called photoelectric photometer. A photometer with a photocell, phototransistor, or phototube for measuring the intensity of light.

electronic power supply A circuit that transforms electrical input energy, that is, alternating or direct current. (Sources operating on rotating machine principles, or deriving electrical power from other energy forms such as batteries and solar cells, are excluded.) Supplies covered by this definition fall into one of four groups: 1) ac in, dc out — most common supplies. 2) ac in, ac out — line regulators, variable-frequency supplies. 3) dc in, dc out — converters. 4) dc in, ac out — inverters.

electronic products Materials, parts, components, subassemblies, and equipment that employ the principles of electronics in performing their major functions. These products may be used as instruments and controls in communications, detection, amplification, computation, inspection, testing, measurement, operation, recording, analysis, and other functions employing electronic principles.

electronic profilometer An electronic instrument for measuring surface roughness. The diamond-point stylus of a permanent-magnet dynamic pickup is moved over the surface being examined. The resultant variations in voltage are amplified and then measured with a meter calibrated to read directly in microinches of deviation from smoothness.

electronic raster scanning Scanning by electronic means so that substantially uniform coverage of an area is provided by a predetermined pattern of scanning lines.

electronic reconnaissance Search for electromagnetic radiations to determine their existence, source, and pertinent characteristics for electronic warfare purposes.

electronic rectifier A rectifier using electron tubes or equivalent semiconductor elements as rectifying elements.

electronic regulation See electronic control.

electronic relay An electronic circuit that provides the functional equivalent of a relay but has no moving parts.

electronics 1. The field of science and engineering concerned with the behavior of electrons in devices and the utilization of such devices. 2. Of or pertaining to the field of electronics, such as electronics engineer, course, laboratory, committee. 3. Name given to that branch of electrical engineering which deals with devices whose operation depends upon the movement of electrons in space as opposed to the movement of electrons in liquids or solid conductors, e.g., radio tubes, photoelectric cells. It includes the study of radio, radar, television, sound films, and control of industrial processes. 4. That branch of science involved in the study and utilization of the motion, emissions, and behaviors of currents of electrical energy through gases, vacuums, semiconductors, and conductors; not to be confused with electrics, which deals primarily with the conduction of large currents of electricity through metals. 5. That branch of science and technology which deals with the study, application, and control of the phenomena of conduction of electricity in a vacuum, in gases, in liquids, in semiconductors, and in conducting and superconducting materials.

electronic search reconnaissance The determination of the presence, source, and significant characteristics of electromagnetic radiations.

electronic security Protection resulting from measures designed to deny to unauthorized persons information of value that might be obtained by interception and analysis of noncommunications electromagnetic radiations.

electronic shock absorption An integrated data bit storage buffer inside a CD portable, which receives information at twice the normal speed but supplies information to the digital-to-analog converter at normal speed, ensuring that any interruption of the data flow caused by shocks or bumps does not result in interruption of play.

electronic shutter A mechanical shutter with an electronic timing circuit. This circuit allows a wider range of exposure times, can be more accurate, and, placed in a circuit with a photconductive cell, allows automatic setting of shutter speeds.

electronic sky screen equipment An electronic device for indicating the departure of a missile from a predetermined trajectory.

electronic speed control 1. A system whereby a motor’s speed is controlled by feedback from a frequency-sensing circuit attached to the device being powered; changes from the desired speed cause corrective signals to speed up or slow down the motor. 2. Changes in speed in a record player, whether gross (as from 33⅓ to 45 rpm) or small (as an order of ±3 percent), can be made by alternating components in the external speed-regulation circuit, rather than by mechanically shifting belts or idler wheel.

electronic sphygmomanometer Device that measures and/or records blood pressure electronically.

electronic stethoscope An electronic amplifier of sounds within a body. Its selective controls permit tuning for low heart tones or high pulmonary tones. It has an auxiliary output for recording or viewing audio patterns.

electronic stimulator A device for applying electronic pulses or signals to activate muscles, or to identify nerves, or for muscular therapy, etc.

electronic surge arrestar A device used to switch high-energy surges to ground so as to reduce the transient energy to a level that is safe for secondary protectors (e.g., zener diodes, silicon rectifiers).

electronic switch 1. A circuit element causing a start and stop action or a switching action electronically, usually at high speeds. 2. An electronic circuit used to perform the function of a high-speed switch. Applications include switching a cathode-ray oscilloscope back and forth between two inputs at such high speed that both input waveforms appear simultaneously on the screen.

electronic switching Electronic circuits and solid-state devices used to perform most telephone central office switching functions.

electronic switching system Abbreviated ESS. 1. A telephone switching system that uses a computer with a storage containing program switching logic. The output of the computer actuates reed or electronic switches that establish telephone connections automatically. 2. A system that uses solid-state switching devices and computerlike operations to accomplish switching of telephone calls. 3. A type of telephone switching system that uses a special-purpose digital computer to direct and control the switching operation. ESS permits custom-calling services such as speed dialing, call transfer, and three-way calling.

electronic thermal conductivity The part of thermal conductivity due to the transfer of thermal energy by means of electrons and holes.

electronic timer 1. A synchronizer, pulse generator, modulator, or keyer that originates a series of continuous control pulses at an unvarying repetition rate known as the pulse-recurrence frequency. 2. A timer using electronic circuits (either tube or transistor type) to control a time period, in place of a motor or other means.

electronic tube relay A relay that employs electronic tubes as components.

electronic tuning 1. Altering the frequency of a reflex klystron oscillator by changing the repeller voltage. 2. Frequency changing in a transmitter or receiver by changing a control voltage rather than circuit components.

electronic video recording The recording of video images by means of photographic film, or magnetic tape or disk, so that the image’s record can be played back in a video format at a later time.

electronic viewfinder Also called viewfinder monitor. 1. A small TV screen attached to a video camera that allows the operator to view a given scene exactly as it is being viewed by the camera. 2. A small television camera that replaces the reflex viewfinder of a motion picture camera. This permits the image photographed to be viewed simultaneously by a number of people, since the TV image may be transmitted to several receivers.

electronic voltmeter Also called vacuum-tube voltmeter. A voltmeter that utilizes the rectifying and amplifying properties of electron tubes or semiconductors and their circuits to secure such characteristics as high input impedance, wide frequency range, peak-to-peak indications, etc.

electronic volt-ohmmeter A device employing the characteristics of an electron-tube or semiconductor circuit for the measurement of voltage and resistance on a single-calibrated scale.

electronic warfare Abbreviated EW. 1. Military usage of electronics to reduce an enemy’s effective use of radiated electromagnetic energy and to ensure our own effective use. 2. Military action involving the use of electromagnetic energy to determine, exploit, reduce, or prevent hostile use of the electromagnetic spectrum, and action that retains friendly use of the electromagnetic spectrum. There are three divisions within electronic warfare: electronic warfare support measures (ESM), electronic countermeasures (ECM), and electronic counter-countermeasures (ECCM).

electronic warfare support measures Abbreviated ESM. That division of electronic warfare involving actions taken to search for, intercept, locate, and immediately identify radiated electromagnetic energy for the purpose of immediate threat recognition. Thus, ESM provides a source of information required for immediate action involving electronic countermeasures, electronic counter-countermeasures, avoidance, targeting, and other tactical employment of forces.

electronic watch A timepiece in which a battery replaces the mainspring, and semiconductor elements replace the mechanical switching-contact arrangement.

electronic waveform synthesizer An instrument using electron devices to generate an electrical signal of a desired waveform.

electron image A representation of an object formed by a beam of electrons focused by an electron optical system.

electron image tube 1. A cathode-ray tube having a photoemissive mosaic upon which an optical image is projected, and an electron gun to scan the mosaic and convert the optical image into corresponding electrical current. 2. A cathode-ray tube that increases the brightness or size of an image, or forms a visible image from invisible radiation. The focal plane for the optical image is a large, light-sensitive cold cathode. The emission from the cathode is first accelerated through a suitable lens system and then strikes a fluorescent screen, where an image is formed that is an enlarged and brightened reproduction of the original image.

electron lens 1. The convergence of the electrons into a narrow beam in a cathode-ray tube by deflecting them electromagnetically or electrostatically. So called because its action is analogous to that of an optical lens. 2. A system of deflecting electrodes or coils designed to produce an electric field that influences a beam of electrons in the same manner in which a lens affects a light beam.

electron metallurgy That branch of metallurgy that uses electron microscopic techniques in the examination of the nature of metals.

electron micrograph A reproduction of an image formed by the action of an electron beam on a photographic emulsion.

electron micrography The photographic recording of images produced by the electrons from an electron microscope. The electron beam carries the images through an array of lenses, and an enlarged electron image is used to stimulate a fluorescent screen that is photographed by a camera system.

electron microradiography The photographic recording and later enlarging of very thin specimens, using an electron beam to form the image.

electron microscope A device utilizing an electron beam for the observation and recording of submicroscopic samples with the aid of photographic emulsions or other short-wavelength sensors. Useful magnification is over 300,000.

electron microscopy The study of materials by means of the electron microscope.

electron mirror An electron instrument used to totally reflect an electron beam.

electron multiplier A vacuum tube in which electrons liberated from a photosensitive cathode are attracted to a series of electrodes called dynodes. In doing so, each electron liberates others by secondary emission and thereby greatly increases the number of electrons flowing in the tube.

electron-multiplier section A section of an electron tube in which an electron current is amplified by one or more successive dynode stages.

electron optical system A combination of parts capable of producing and controlling a beam of electrons to produce an image of an object.

electron optics 1. The branch of electronics concerned with the behavior of the electron beam under the influence of electrostatic and electromagnetic forces. 2. The control of free electron movement through the use of electric or magnetic fields, and use of the electron movement in research investigation of electronic diffraction phenomena, directly analogous to the control of light through use of lenses. 3. The area of science devoted to the directing and guiding of electron beams using electric fields in the same manner as lenses are used on light beams. 4. Pertaining to devices whose operation relies on modification of a material’s refractive index by electric fields, for example, image-converter tubes and electron microscopes.

electron-pair bond A valence bond formed by two electrons, one from each of two adjacent atoms.

electron paramagnetic resonance A condition in which a paramagnetic solid subjected to two magnetic fields, one of which is fixed and the other normal to the first and varying at the resonance frequency, emits electromagnetic radiation associated with changes in the magnetic quantum number of the electrons.

electron probe A narrow beam of electrons used to scan or illuminate an object or screen.

electron-ray tube Also called a magic eye. 1. A tube that indicates visibly on a fluorescent target the effects of changes in control-grid voltage applied to the tube. Used as a tuning indicator in receivers. 2. A type of recording-level indicator using a luminous display in a special tube. The display is typically like an “eye” with a keyhole in the middle, and maximum recording level corresponds to the closing-up of a slot at the bottom of the keyhole (largely superseded by meters in current-model recorders).