. 13
( 42)


dual gate 1. A digital integrated circuit (IC) con- example, a common-emitter, current-sensitive,
sisting of two logic gate units. 2. Pertaining to a bipolar-transistor circuit is the dual of a com-
field-effect transistor (FET) with two gates or gate mon-source, voltage-sensitive, field-effect-tran-
electrode connections. sistor (FET) circuit. Also see DUALITY.
dual-gate FET A field-effect transistor with two dual operation In digital logic, the operation re-
gate (input) electrodes. sulting from inverting all of the digits. Every 1 is
dual-gate MOSFET A metal-oxide-semiconductor replaced with a 0, and vice versa.
field-effect transistor (MOSFET) with two gate (in- dual-output power supply A power supply with
put) electrodes. two outputs. Often, one output is positive and the
dual-inline package Abbreviation, DIP. A flat, other is negative. In some cases, one output con-
molded integrated-circuit (IC) package having ter- sists of alternating current (ac) and the other con-
minal pins along both long edges. sists of direct current (dc).
dual pickup In disk reproduction, a pickup having
two styli, one for large-groove records and one for
fine-groove records.
dual potentiometer A ganged assembly of two po-
tentiometers. The resistance values might or
might not be the same.
dual preset counter A preset counter that will set
alternately to two different numbers.
dual rail See DOUBLE RAIL.
dual resistor See DUAL POTENTIOMETER and
dual rheostat A ganged assembly of two rheo-
stats. The resistance values might or might not
be the same.
dual stereo amplifier 1. A two-channel audio am-
plifier for stereophonic audio applications. 2. A
Pins two-channel linear integrated circuit (IC) for
stereophonic audio applications.
dual-system loudspeaker See TWO-WAY
dual-inline package
dual trace In a cathode-ray oscilloscope, the use of
two separate electron beams, which can show two
duality 1. The condition of being dual (see DUAL).
different signals simultaneously on a single
This can be an aid in the design of certain circuits
requiring complementary parameters, e.g., cur-
dual-trace recorder See DOUBLE-TRACK RE-
rent-operated circuit analogs of voltage-operated
circuits. 2. See DUALITY OF NATURE.
dual-track recorder See DOUBLE-TRACK RE-
duality of nature 1. Any of various situations in
which a phenomenon exhibits two distinct and
dual recording In digital computer operations, up-
different natures. A commonly cited example is
dating two sets of master files simultaneously.
the dual model of light. In some instances, visible
dual use The use of a communications system for
light behaves like a barrage of particles, but in
two modes of data transfer at the same time.
other environments it appears to be a wave effect.
Duant electrometer See BINANT ELECTROMETER.
Another example is the dual model of electro-
218 duct • dump check

back. In a simple application of multiple feed-
back, a single external loop is augmented with
unbypassed emitter resistors in the amplifier
Channel 1
Duerdoth™s stability margin A feedback-amplifier
stability margin equal to a 6-dB increase in gain
at low and high frequencies over beta values be-
tween 0.3 and somewhat less than 2. For higher
beta values, Duerdoth adopts an angular margin
(for example, 15°); below β = 0.3, no danger of in-
Channel 2 stability is present.
dummy 1. A nonoperative model of a piece of
equipment, usually assembled with dummy com-
ponents (see DUMMY COMPONENT, 1) for the
purpose of developing a layout. 2. DUMMY AN-
dual trace
LOAD. 3. Part of a computer program that, rather
than being useful for the problem at hand, only
serves to satisfy some other format or logic re-
duct 1. A narrow propagation path, sometimes
traveled by microwaves, created by unusual at-
dummy antenna 1. A nonradiating device that
mospheric conditions. 2. A pipe or channel for ca-
serves as a load for a transmitter (i.e., it takes the
bles and wires.
place of the regular antenna during tests and ad-
dubbing The adding of sound to a recorded mag-
justments of the transmitter). 2. A device
netic tape, record disk, or film (e.g., replacing the
containing a network of discrete inductive,
sound track of a film in one language with that of
capacitive, and resistive elements, inserted be-
another language).
tween a radio-frequency signal generator and re-
dubnium Symbol, Db. Also clalled unnilpentium
ceiver to simulate a standard antenna.
(Unp) and hahnium (Ha). Atomic number, 105.
dummy component 1. A nonoperative compo-
The most common isotope has atomic weight
nent used in developing a layout or package. 2.
262. Classified as a transition metal. It has a
A nonoperative component fraudulently in-
half-life on the order of a few seconds to a few
cluded in a piece of equipment (e.g., an unwired
tenths of a second (depending on the isotope), is
transistor in a receiver circuit, a common occur-
human-made, and is not known to occur in na-
rence during the early days of the transistor,
when a 10-transistor radio brought more money
duct 1. A narrow propagation path, sometimes
than an 8-transistor radio, without regard to the
traveled by microwaves, created by unusual at-
circuit itself).
mospheric conditions. 2. A pipe or channel for ca-
dummy instruction In a computer, a command
bles and wires. 3. An opening, vent, or other
that serves no operational purpose, other than to
airway used for various purposes, such as cooling
fill a format requirement.
and acoustic wave transmission.
dummy load 1. A load device, usually consisting of
ducted port An opening in a speaker cabinet that
resistance without reactance, used to terminate a
has an airway (duct) extending several inches
power generator or power amplifier during ad-
into the cabinet. It improves the quality of sound
justments and tests. The load resistance is equal
from a speaker system by equalizing the air pres-
to the output impedance of the generator or am-
sure inside and outside the cabinet. Also provides
plifier. 2. See DUMMY ANTENNA.
resonant audio effects at frequencies that depend
dummy resistor A power-type resistor used as a
on the dimensions of the duct.
dummy load.
dump 1. In digital-computer operations, to trans-
ductilimeter An instrument used for measuring
fer, completely or partially, the contents of mem-
the ductility of metals.
ory into a peripheral. 2. To switch off all power to
ducting The confinement of a radio wave to a duct
a computer, deliberately or accidentally, thereby
(see DUCT, 1) between two layers of the atmo-
losing what is in the volatile memory.
sphere or between an atmospheric layer and the
dump and restart During a halt in a computer
program run, to backtrack to the last dump point
Duddell arc A carbon copper arc circuit that pro-
and use the data there to resume the run. Also
duces audible continuous waves. Consists of a
series inductance-capacitance (LC) circuit shunt-
dump check In digital-computer operations, the
ing an electric arc.
checking of all digits being transferred (see
Duerdoth™s multiple feedback system In an am-
DUMP, 1) to prevent errors when they are re-
plifier, feedback through several paths to improve
response over that afforded by single-path feed-
dumping • dust cover

duplexing assembly In a radar system, a device
dumping To transfer the output at various stages
that automatically makes the receiver unrespon-
in a computer program run to an external storage
sive to the outgoing transmitted signal while al-
medium, so it will be available (in case of a fail-
lowing incoming signals to reach the receiver
ure) for the program™s resumption from a point
other than at the beginning.
duplex computer system An installation of two
dump point In writing a computer program, a point
computer systems, one standing by to take over
at which instructions are given to transfer data
in case the other fails.
processed thus far to a storage medium that would
duplex operation The simultaneous operation of a
be unaffected by a software or hardware failure.
transmitter and receiver at a single location. This
becomes possible (without mutual interference)
dumping resistor 1. See BLEEDER. 2. A resistor
through the use of two sufficiently separated car-
having the minimum resistance permissible in a
rier frequencies.
given situation. Used to discharge a capacitor, it
duplex system A system composed of two identical
acts to provide an alternative path to a potentially
equipment sets”either of which will perform the
destructive short circuit.
intended function while the other stands by.
duo Any pair of matched components, usually in a
duplication check In digital-computer operations,
single package.
the checking of an operation by doing it twice, us-
duodecal CRT base The 12-pin base of a cathode-
ing different methods in each case, to ensure the
ray tube. Also see BIDECAL, DIHEPTAL, and
accuracy of results.
duplication house A professional person or com-
duodecal socket A 12-pin tube socket. Also see
pany who makes high-quality copies of tape
recordings (either audio or video). Charges vary,
duodecimal 1. Having 12 possibilities, states,
depending on the type and length of the record-
choices, etc. 2. Pertaining to the DUODECIMAL
NUMBER SYSTEM. 3. A number or numeral in
duplicate To transfer data from one storage loca-
tion to another. Compare DUMP, 1.
duodecimal number system A system of number-
dural See DURALUMIN.
ing in which the radix, also called the base or
duralumin An alloy of aluminum, copper, magne-
modulus, is 12. The system uses the digits 0
sium, manganese, and silicon. It offers strength
through 9, plus two other characters (usually A
with minimal weight.
and B) to represent 10 and 11. Thus, counting
duration control A potentiometer or variable ca-
proceeds as 0, 1, 2, . . . , 9, A, B, 10, 11, 12, . . . , 19,
pacitor for adjusting the duration of a pulse.
1A, 1B, 20, 21, 22, etc. At one time, some people
duration time The period during which a pulse is
seriously proposed that this system replace the
sustained (i.e., the interval between turn-on and
DECIMAL NUMBER SYSTEM for general use.
turn-off time).
duodiode See DUAL DIODE.
duolateral coil A multilayer, lattice-wound coil
(see UNIVERSAL WINDING) in which the turns in
successive layers are staggered slightly. Also
called honeycomb coil.
duopole A two-pole all-pass device.

duplex 1. A mode of communication in which two time
channels are used so that either operator in a
conversation can interrupt the other at any time.
2. The transmission of two messages over a single
circuit, at the same time.
duplex artificial line In wire telephony, a balanc-
ing network that simulates the impedance of the
duration time
actual line and the remote terminal equipment; it
prevents an outgoing transmission from interfer-
ing with the local receiver. during cycle The interval during which a timer is
duplex cable A cable consisting of a twisted pair of in operation.
insulated stranded-wire conductors. durometer An instrument for measuring the hard-
duplex channel A channel used for wire or radio ness of a material.
duplex communication See DUPLEX OPERA- dust core A magnetic core for radio-frequency coils
TION. consisting of very minute particles of iron or an
duplex diode See DUAL DIODE. alloy, such as Permalloy.
duplexer In radar operations, a device operated by dust cover A removable, usually plastic cover for
the transmitted pulse to automatically switch the electronic and computer equipment, to protect
antenna from the receiver to the transmitter. hardware during periods of nonuse.
220 dust-ignition-proof motor • dynamic debugging

dust-ignition-proof motor A motor whose hous- dynamic acceleration Acceleration whose magni-
ing completely prevents the entry of dust, virtu- tude and direction are constantly changing.
ally eliminating the danger of fine dust sparking dynamic allocation In multiprogramming, a sys-
inside the machine. tem in which a monitor program assigns periph-
dust precipitator An electrostatic device for re- erals and areas of memory to a program.
moving dust, lint, and other particles from the dynamic analogy A mathematical similarity be-
air. It consists essentially of a pair of screens or tween or among various phenomena involving the
wires through which the air passes; a potential of motion of particles.
several thousand volts is maintained between dynamic base current See AC BASE CURRENT.
them. The particles acquire a charge, then stick dynamic base resistance See AC BASE RESIS-
to the oppositely charged screen. TANCE.
Dutch metal A copper-zinc alloy. dynamic base voltage See AC BASE VOLTAGE.
duty cycle 1. The proportion or percentage of dynamic behavior 1. The behavior of a component,
time during which a device, circuit, or system is device, or system when signals are applied, as
operating or handling power. For example, when opposed to static behavior under no-signal condi-
a radiotelegraph transmitter is keyed on and off tions. 2. The behavior of a device or system involv-
to send Morse code, the duty cycle is approxi- ing the motion of particles over a period of time.
mately 50 percent; with frequency-shift keying, dynamic braking A technique for stopping a motor
the duty cycle is 100 percent. 2. The conditions quickly using a resistor (the dynamic braking re-
under which an electrochemical cell or battery sistance) connected across the spinning arma-
is used. In particular, the proportion or percent- ture. The resistor dissipates the energy generated
age of time during which current is drawn from by the motor, producing a damping action that
the cell or battery for the purpose of operating results in braking.
an electrical or electronic circuit, device, or dynamic characteristic The performance charac-
system. teristic of a device or circuit under alternating-
duty cyclometer A direct-reading instrument for current (ac) operating conditions, as opposed to
measuring duty cycle. the static characteristic, when only direct current
duty factor 1. The ratio Pavg/Ppk, where Pavg is the (dc) flows.
average power in a system and Ppk is the peak dynamic check 1. A test made under actual oper-
power. 2. The product of the duration and the ating conditions of a device or circuit. 2. A test
repetition rate of regularly recurring pulses com- made with an alternating-current (ac) applied sig-
prising a carrier. nal, rather than with direct-current (dc) quanti-
duty ratio See DUTY FACTOR, 1. ties.
DVM Abbreviation of DIGITAL VOLTMETER. dynamic collector current See AC COLLECTOR
MILLIAMMETER. dynamic collector resistance See AC COLLEC-
dwell meter An instrument that shows the period TOR RESISTANCE.
(or angle) during which contacts remain closed. dynamic collector voltage See AC COLLECTOR
dwell switching Switching action in which the VOLTAGE.
contacts are held closed (or a circuit kept on) for dynamic contact resistance In relay or switch
specified periods, as opposed to MOMENTARY contacts, variation in the electrical resistance of
SWITCHING. the closed contacts because of variations in con-
dwell tachometer A combination dwell meter/ tact pressure.
tachometer for automobile engine testing and ad- dynamic convergence In a color picture tube, the
justment. The dwell meter allows observation and meeting of the three beams at the aperture mask
adjustment of the ignition point cam angle; the during scanning.
tachometer shows the motor speed in revolutions dynamic current amplification Abbreviation,
per minute (rpm). DCA. An expression of gain in a bipolar transistor.
DX 1. Radiotelegraph abbreviation meaning long Specified as the ratio of the difference in collector
distance or foreign country. 2. A communication current IC to the difference in base current IB
or broadcast station located far away and/or in a
foreign country. 3. Abbreviation of DUPLEX.
DXer An amateur radio operator who prefers to Geometrically, the dynamic current amplification
communicate with stations far away and/or in at a given bias point is the slope of a line tangent
foreign countries. to the IC-versus-IB curve at that point.
Dy Symbol for DYSPROSIUM. dynamic curve A characteristic curve that ac-
dyadic operation A binary operation (i.e., one us- counts for the presence of resistance in series
ing two operands). with the device to which the curve applies.
dyn Abbreviation of DYNE. dynamic debugging Any debugging operation per-
dyna- A prefix (combined form) meaning power formed on a computer system during a normal-
(e.g., dynamometer and dynatron). speed program run.
dynamic decay • dynamic range

dynamic limiter A limiter, such as is used in fre-
dynamic decay Decay resulting from such factors
quency-modulation (FM) receivers, that main-
as ion charging in a storage tube.
tains the output-signal level, despite appreciable
dynamic demonstrator A teaching aid consisting
excursions of input-signal amplitude.
of a board displaying an electronic circuit, behind
dynamic loudspeaker See DYNAMIC SPEAKER.
which is mounted the actual circuit. Various cir-
dynamic magnetic field A magnetic field whose
cuit components (especially adjustable ones) are
intensity is constantly changing, either periodi-
mounted on the front of the board, in clear view
cally or in a complex way.
at places where their circuit symbols appear. Pin
dynamic memory A usually random-access data
jacks at important test points in the circuit allow
storage method in which the memory cells must
connection of a meter, signal generator, and os-
be electrically refreshed periodically to avoid the
cilloscope leads for testing or demonstrating the
loss of held data.
dynamic microphone A microphone in which a
dynamic deviation The difference between ideal
small coil attached to a vibrating diaphragm or
output and actual output of a circuit or device op-
cone moves in a uniform magnetic field to gener-
erating with a reference input that changes at a
ate the output signal.
constant rate and is free of transients.
dynamic diode tester An instrument that displays
the response curve (or family of curves) of a diode
on a calibrated oscilloscope screen. The horizon-
tal axis of the screen indicates voltage, the verti-
cal axis shows current, and zeros for both
quantities are at center screen. Also see DY-
dynamic drain current See AC DRAIN CURRENT.
Sound waves
dynamic drain resistance See AC DRAIN RESIS-
dynamic drain voltage See AC DRAIN VOLTAGE. Output
dynamic dump A dump that occurs during a pro-
gram run. See DUMPING. dynamic microphone
dynamic electric field An electric field whose in-
tensity is constantly changing, either periodically
or in a complex way. dynamic mutual conductance See DYNAMIC
dynamic emitter current See AC EMITTER CUR- TRANSCONDUCTANCE.
RENT. dynamic noise suppressor A noise limiter consist-
dynamic emitter resistance See AC EMITTER ing of an audio filter whose bandwidth is directly
RESISTANCE. proportional to signal strength (i.e., it is varied
dynamic emitter voltage See AC EMITTER VOL- automatically by signal amplitude).
TAGE. dynamic operating line A curve displaying the
dynamic equilibrium 1. The state of balance be- control function of a device. For example, the
tween constantly varying quantities. 2. The ten- collector-current-versus-base-current curve of a
dency of two current-carrying circuits to maintain bipolar transistor is drawn between the limits of
at a maximum the magnetic flux linking them. saturation and cutoff.
dynamic error In a periodic signal delivered by a dynamic output impedance The output impe-
transducer, an error resulting from the restricted dance of a power supply, as “seen” by the load.
dynamic response of the device. dynamic pickup A phonograph pickup whose sty-
dynamic flip-flop A flip-flop (bistable multivibra- lus causes a small coil to vibrate in the field of a
tor) that is kept on by recirculating an alternat- permanent magnet. Works on the same principle
ing-current (ac) signal. The device can be as the DYNAMIC MICROPHONE.
switched on or off by a single pulse. Compare dynamic printout A printout that occurs as a sin-
STATIC FLIP-FLOP. gle function, actuated by one command, and
dynamic focus Compensation for defocusing, completing itself in one operation.
caused by the electron beam sweeping in an arc dynamic problem checking A method of checking
across a flat color picture-tube screen; the the solution obtained by an analog computer, to
method uses an alternating-current (ac) focus- see that it makes sense (is not absurd).
ing-electrode voltage. dynamic programming A method of problem
dynamic gate voltage See AC GATE VOLTAGE. solving in which continual checks are made to
dynamic impedance The impedance of a device ensure accuracy or conformance to a certain set
(such as a transistor or diode) when it is operat- of rules.
ing with an applied alternating-current (ac) sig- dynamic range 1. In high-fidelity audio, the ratio
nal, as opposed to its static resistance with only of the loudest sound to the faintest sound that
direct current (dc) applied. can be reproduced without significant distortion
222 dynamic range • dynatron

or noise. It is usually expressed in decibels. 2. In dynamic stop As caused by a computer program
a communications receiver, a measure of the instruction, a loop indicating the presence of an
ability to receive both weak and strong signals error.
without excessive noise, distortion, desensitiza- dynamic storage See DYNAMIC MEMORY.
tion or other undesirable effects. It is expressed dynamic subroutine A form of computer subrou-
in various ways, typically in decibels. 3. The ratio tine that allows the derivation of other subrou-
between the loudest and faintest sounds, or be- tines in various forms.
tween the strongest and weakest signals, encoun- dynamic test See DYNAMIC CHECK.
tered in a given environment or situation. It is dynamic transconductance Transconductance
usually expressed in decibels. determined from alternating-current (ac) signal
dynamic rectifier tester An instrument that dis- parameters, rather than from direct-current (dc)
plays the response curve of a rectifier on a cali- parameters.
brated oscilloscope screen. During the test, the dynamic transducer A coil-and-magnet device
rectifier receives an alternating-current (ac) that converts mechanical vibration into electric
voltage with a low positive peak and high nega- currents, or vice versa. Common examples in-
tive peak, both corresponding to the rated for- clude most microphones, headphones, and loud-
ward and reverse voltages (respectively) of the speakers.
rectifier. The horizontal axis of the screen indi- dynamic transfer characteristic An input-output
cates voltage, the vertical axis indicates current, characteristic determined, with respect to the
and zeros for both quantities are at center load of a transfer device. Also see DYNAMIC
dynamic regulation In an automatically regulated dynamic transistor tester 1. An instrument for
system, such as a voltage-regulated power sup- checking the alternating-current (ac) gain of a
ply, the transient response of the system. Dy- transistor, rather than its direct-current (dc)
namic regulation is determined from maximum beta. 2. An instrument for determining the condi-
overshoot and recovery time when the load or line tion of a transistor from its performance in a sim-
value is suddenly changed. ple oscillator circuit. 3. An instrument that
dynamic regulator A circuit or device providing displays a transistor response curve, or a family
dynamic regulation. of such curves, on a calibrated oscilloscope
dynamic reproducer 1. See DYNAMIC MICRO- screen. Also see DYNAMIC DIODE TESTER and
NAMIC SPEAKER. dynamo A mechanical generator of electricity; typ-
dynamic resistance See DYNAMIC IMPEDANCE. ically a rotating machine.
dynamic run See DYNAMIC CHECK, 1. See also dynamoelectric machinery Rotating electric ma-
DYNAMIC DEBUGGING. chinery. Examples: amplidynes, generators, dy-
dynamics The study of bodies, charges, fields, namotors, rotary converters.
forces, or pulses in motion. Compare STATICS. dynamometer 1. See ELECTRODYNAMOMETER.
dynamic sequential control In digital computer 2. A device for mechanically measuring the out-
operation, the computer™s changing the sequence put power of a motor.
of instructions during a run. dynamometer ammeter See ELECTRODYNA-
dynamic source current See AC SOURCE CUR- MOMETER.
RENT. dynamometer voltmeter See ELECTRODYNA-
dynamic source resistance See AC SOURCE RE- MOMETER.
SISTANCE. dynamophone A dynamometer (see DYNAMO-
dynamic source voltage See AC SOURCE VOLT- METER, 2) that uses two telephone circuits to
AGE. measure the twist of a shaft.
dynamic spatial reconstructor Abbreviation, dynamostatic machine A machine driven by al-
DSR. An advanced x-ray machine, developed at ternating-current (ac) or direct-current (dc) power
the Mayo Clinic, that displays organs in three- for the generation of static electricity.
dimensional views in motion, and allows them to dynamotor A (usually small) self-contained
be electronically dissected without actually motor-generator. The motor and generator
operating on the patient. portions are enclosed in a common housing,
dynamic speaker A loudspeaker in which a small giving the machine the appearance of a simple
coil (voice coil), attached to a diaphragm or cone motor.
and carrying an audio-frequency signal current, dynaquad A pnpn four-layer semiconductor device
moves back and forth in a permanent magnetic with three terminals, similar to the silicon-
field and, accordingly, causes the diaphragm or controlled rectifier or thyristor.
cone to vibrate (emit sound). Compare MAG- dynatron A form of vacuum tube that displays a
NETIC SPEAKER. negative-resistance characteristic, resulting in
dynamic stability A measure of the ability of a oscillation at ultra-high and microwave frequen-
robot to maintain its balance while in motion. cies.
dynatron frequency meter • dysprosium

dynatron frequency meter A heterodyne-type fre-
quency meter using a dynatron oscillator. Dynodes
dyne Abbreviation, d. A unit of force. One dyne

(10“5 newton) is the force that will give a mass of Load
1 gram an acceleration of 1 centimeter per second
per second. Compare NEWTON.
dyne-centimeter See ERG.
dyne-five In the Giorgi mks system, a unit of force
equal to 1 newton. Visible
dyne per square centimeter Abbreviation, d/cm2. light
A unit of pressure equal to 0.1 pascal (9.869 —
10-7 atmosphere).
dyne-seven A unit of force equal to 107 dynes.
dynistor A semiconductor diode that continues to
conduct after the forward voltage is reduced be-
low the normal threshold point. To stop the con-
duction, a reverse voltage must be applied, or
voltage must be entirely removed from the device.
It is used in switching applications.
dynode In a photomultiplier tube, any of several cathode is greatly amplified when it reaches the
slanting electrodes that receives a beam of elec- plate.
trons generated by the light-sensitive cathode dysprosium Symbol, Dy. An element of the rare-
and reflects it, along with secondary electrons. earth group. Atomic number, 66. Atomic weight,
This amplifies the beam; the process is repeated 162.50. Dysprosium is a highly magnetic sub-
several times. Thus, the emission from the stance.
E 1. Symbol for VOLTAGE. 2. Symbol for ELEC- earth currents 1. Electric currents induced in the
TRIC FIELD STRENGTH. 3. Abbreviation of earth by current flowing through underground or
EMITTER. 4. Symbol for prefix EXA. 5. Symbol underwater cables. 2. Electric currents flowing
for ENERGY. through the earth between ground connections of
e 1. Symbol for VOLTAGE. 2. Abbreviation of electrical equipment.
EMITTER. 3. Symbol for ELECTRON CHARGE. 4. earth ground 1. A common connection to an elec-
Symbol for the natural logarithm base (approxi- trode buried in the earth so that good conductiv-
mately equal to 2.71828). 5. Symbol for ECCEN- ity is maintained between the common circuit
TRICITY. 6. Abbreviation of ERG. point and the earth itself. 2. A rod driven into the
EAM Abbreviation of electronic accounting machine. surface of the earth for use as a common circuit
E and M terminals The output and input leads in connection.
some signaling systems. Also called E and M earth inductor A magnetometer consisting of a
leads. coil that is rotated in the earth™s magnetic field. It
early early sound Sound propagated through delivers an alternating-current (ac) voltage pro-
solids and/or liquids that reaches a pickup de- portional to the field strength. Also called gener-
vice (such as a microphone) before the sound ating magnetometer.
propagated through the air. In general, sound earth-moon-earth See MOONBOUNCE.
waves travel faster as the medium becomes more earth resonance A resonant effect at extremely low
dense. frequencies, caused by reflection of currents
early-failure period The period immediately after within the earth. Resonant currents have been
manufacture of a device, during which the failure tested as a means of communicating with sub-
rate (caused by defects in equipment or work- marines worldwide.
manship) is high. earth™s magnetic field Also called geomagnetic
early-warning radar Abbreviation, EWR. A radar field. The natural magnetic field whose lines of flux
system that produces immediate warning when extend from north to south. The earth™s magnetic
enemy aircraft enter the monitored area. poles, also called the geomagnetic poles, do not ex-
earphone 1. Headphone (usually a single unit). actly coincide with the geographic poles. The field
2. Telephone receiver. 3. A miniature acoustic somewhat resembles that of a bar magnet.
transducer that is small enough to be inserted Eastern Standard Time Abbreviation, EST. Local
into the ear. mean time at the 75th meridian west of Green-
earpiece See EARPHONE, 3. wich.
earth 1. The ground. 2. An electrical connection to east-west effect The phenomenon in which the
the earth (see GROUND CONNECTION, 2). 3. In number of cosmic rays approaching earth near
space communications, the planet Earth. the equator from the west is greater than that
earth connection See GROUND CONNECTION, 2. from the east by 10 percent.

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Eavg • echo

becomes elliptical and deviates more and more
Magnetic pole
from a perfect circle, the eccentricity increases.
When the eccentricity reaches 1, the object takes
a parabolic path through space. If the eccentricity
Flux lines exceeds 1, the path is a hyperbola.
ECDC Abbreviation of electrochemical diffused col-
ECG Abbreviation of electrocardiogram. (Also,
ECG telemetry Use of a radio telemetering system
to monitor the heart function of a person from a
echelon 1. A level of calibration accuracy, the
Magnetic pole highest echelon being the national standard for
the particular measurement involved. 2. A level of
earth™s magnetic field maintenance in which lower ordinal numbers re-
fer to less-critical tasks, and higher ordinal num-
bers refer to tasks requiring progressively higher
skills and technological expertise.
Eavg Symbol for AVERAGE VOLTAGE.
echelon grating A diffraction grating with ex-
tremely high resolution. Generally useful only
E bend In a waveguide, a smooth change in the di-
over a small range of wavelengths.
rection of the axis, which remains parallel to the
echo 1. A signal that is reflected back to the point
direction of polarization.
of origin. 2. A reflected or delayed signal compo-
nent that arrives at a given point behind the main
component. 3. A radar blip, indicating an object
ebiconductivity Conductivity resulting from elec-
or thundershower. 4. Reflection of the signal on a
tron bombardment.
telephone line, caused by improper impedance
ebonite Hard rubber used as an insulant. Dielec-
matching, or by overload of the system by too
tric constant: 2.8. Dielectric strength: 30 to 110
many subscribers attempting to use the system
at the same time. 5. In audio systems, a circuit
that causes sounds to repeat one or more times,
at intervals ranging from a fraction of a second to
several seconds. 6. The effect produced by a cir-
cuit, as defined in 5.
EBS amplifier An amplifying device using an elec-
tron-bombarded semiconductor. The electron
beam is modulated by the input signal, and the
modulated resistance of the semiconductor target Short path
modulates a relatively heavy current to provide
an amplified output. Current gains on the order Ionosphere
of 2000 are possible.
ec Abbreviation of ENAMEL-COVERED (in refer-
ence to wire).
eccentric circle See ECCENTRIC GROOVE.
eccentric groove On a phonograph record, an off-
center groove in which the stylus rides at the end
of the recording, where it causes the tone arm to Earth
trip the record-changing mechanism.
eccentricity 1. The condition of being off center,
intentionally or not. It is often a consideration in
the behavior of dials, potentiometers, and ser-
vomechanisms. 2. On a phonograph record, the
condition in which the spiral recording groove
and the center hole of the disk are not concentric.
3. A quantitative expression for the extent to
which an ellipse is elongated.
Long path (echo)
eccentricity of orbit The extent to which the orbit
or path of a satellite differs from a circle. A
circular orbit has eccentricity zero. As the orbit
226 echo area • eddy-current loss

echo area The area of a target that will return a echo suppression In a telephone circuit, a device
radar signal as an echo. that chokes off reflected waves, thereby minimiz-
echo attenuation In a bidirectional wire- ing audible echo.
communication circuit equipped with repeaters echo suppressor See ECHO ELIMINATOR.
or multiplexers, the attenuation of echo currents echo talk Echo in a telephone system that results
set up by conventional operation. in distracting interference.
echo box A resonant-cavity device used to test a echo wave A reflected wave, such as a radio wave
radar set. Part of the transmitted energy enters reflected alternately between earth™s surface and
the box, which retransmits it to the receiver. The the ionosphere.
signal reaching the receiver is a slowly decaying ECL Abbreviation of EMITTER-COUPLED LOGIC.
transient whose intensity eventually falls below eclipse effect A decrease in the critical frequency
the level that can be displayed on the screen; the of the E and F1 layers of the ionosphere during a
time required to reach this level indicates radar solar eclipse.
performance. ecliptic orbit Any orbit that lies in the same plane
echo chamber A reverberation chamber, electronic as the orbit of the earth around the sun (the eclip-
recording device, or room for acoustic tests or for tic plane). The ecliptic plane is slanted about
simulating sonic delays. 23.5° from the plane of the earth™s equator.
echo check In data communication, a means of ECM Abbreviation of ELECTRONIC COUNTER-

checking the accuracy of received data by send- MEASURES.
ing it back to the transmitting station for com- ECO Abbreviation of ELECTRON-COUPLED OS-

parison with the original data. CILLATOR.
echo depth sounder See ACOUSTIC DEPTH econometer An instrument for continuously mon-
SOUNDER. itoring the amount of carbon dioxide in (factory)
echo eliminator 1. A device that quiets a naviga- flue gases.
tional instrument after receipt of a pulse, to pre- E core A transformer or transducer core having the
vent reception of a subsequent, delayed pulse. 2. shape of an E. Coils can be wound on one, two, or
In a two-way telephone circuit, a voice-operated all three of the crosspieces.
device that suppresses echo currents caused by
conversation currents going in the opposite direc-

echoencephalograph An ultrasonic medical in-
strument that allows viewing of internal organs.
Used for diagnostic purposes in certain situa-
tions, instead of the X-ray machine.
echogram In acoustics, a graph of the sound
decrement in an enclosure. Time is plotted on
the horizontal axis; signal amplitude is plotted
on the vertical axis. An intense pulse is transmit-
ted from a speaker; a microphone picks up the
echoes and sends them to a pen recorder or mi-
echo intensifier A device used at a radar target to
E core
boost the intensity of reflected energy.
echo interference Radio interference resulting
from a reflected signal arriving slightly later than ECPD Abbreviation of Engineer™s Council for Profes-
the direct signal. sional Development.
echo matching In an echo-splitting radar system, ECTL Abbreviation of emitter-coupled transistor logic.
the trial-and-error orientation of the antenna to EDD Abbreviation of ENVELOPE-DELAY DISTOR-
find the direction from which the pulse indica- TION.
tions are identical. eddy current A circulating current induced in a
echo ranging An ultrasonic method of determining conducting material by a varying magnetic field,
the bearing and distance of an underwater object. often parasitic in nature. Such a current can, for
echo send In an audio mixer, an output for deliv- example, flow in the iron core of a transformer.
ering signals to external systems, such as an eddy-current device A brake, coupling, clutch,
echo box (see ECHO, 5). It can also provide an drag cup, drive unit, or similar device whose op-
auxiliary output for a second set of speakers, a eration is based on the generation of torque, pull,
tape recorder, etc. or opposition by the action of eddy currents.
echo sounder See ACOUSTIC DEPTH SOUNDER. eddy-current heating Heating caused by eddy-
echo splitting Separating a radar echo into two current loss in a material.
parts so that a double indication appears on the eddy-current loss Power loss resulting from eddy
radar screen. currents induced in nearby structures by an

eddy-current loss • effective acoustic center

electromagnetic field. Eddy currents in the core of circuit voltage of the cell is typically 1.2 V at full
a transformer give rise to such loss. charge.
edge connector A terminal block with a number of Edison distribution system A three-wire, 110- to
contacts, attached to the edge of a printed-circuit 250-volt direct-current (dc) power-distribution
board for easy plugging into a foundation circuit. system.
edge control In the manufacture of paper, a Edison effect Thermionic emission of negatively
robotic system for maintaining the width of a charged particles (electrons) from a hot filament
sheet by sensing the edges and correcting the sealed in an evacuated bulb; they are attracted by
machine accordingly. Transducers that sense the a cold, positively charged metal plate in the bulb.
passing edges deliver output signals proportional E display A radar display in which the horizontal
to variations from standard width. coordinate indicates distance, and the vertical co-
edge detection The ability of a machine vision sys- ordinate indicates elevation.
tem to locate and follow boundaries. Used exten- edit 1. In tape recording, the modifying of the
sively in mobile robots. recorded material by deleting (cutting out or eras-
edge effect The extension of electric lines of flux ing), adding (splicing or overrecording), or chang-
between the outer edges of capacitor plates. This ing the sequence of the material by physically or
portion of the interplate field contributes a small magnetically altering the tape. 2. In digital com-
amount of capacitance. Because the lines of flux puter operations, to make data ready for process-
are not confined to the space between plates, they ing.
can cause capacitive coupling with external edit decision list In the editing of a digital au-
bodies. dio/video presentation, a record of every change
(cut and paste). The list is automatically made by
the computer and stored on disk for later refer-
ence if needed.
editing 1. Alteration of a magnetic-tape recording
Positive plate of capacitor by means of splicing. 2. Alteration of data stored
in memory, either by adding information, remov-
ing information, changing information, or (usu-
ally) a combination of these operations.
Negative plate of capacitor
EDP Abbreviation of electronic data processing.
edge effect
edge-punched card In digital computer opera-
tions, a punched card whose edge is perforated in
a narrow column, the center being used for writ-
ten annotation.
EDT 1. Abbreviation of ethylene diamine tartrate (a
edgewise meter A meter having a curved horizon-
synthetic piezoelectric material). 2. Abbreviation
tal scale; this arrangement allows mounting the
of Eastern Daylight Time.
instrument edgewise in a panel.
EDU Abbreviation of electronic display unit.
edgewise-wound coil A coil made of a flat metal
educational robot A robot that can be programmed
strip cut in the shape of a coil spring. The design
for the purpose of teaching its users something.
allows the use of clips to vary the inductance, but
Popular as an educational toy for children.
this advantage is often offset by the coil™s high
EDVAC Acronym for Electronic Discrete Variable
distributed capacitance.
Automatic Computer, a development of the Uni-
edging In a color television picture, extraneous
versity of Pennsylvania.
color of a different hue than the objects around
whose edges it appears.
Edison base A threaded base on light bulbs, cone-
type heaters, and some pilot lamps.
Edison battery A group of Edison cells connected
in series, parallel, or both, and contained in a sin-
gle package with two electrodes.
Edison cell A secondary (storage) cell in which the
active positive plate material consists of nickel
EES Abbreviation of EARLY EARLY SOUND.
hydroxide held in steel tubes assembled into a
effective acoustic center The apparent point of
steel grid; the active negative plate material is
propagation of spherically divergent sound waves
powdered iron oxide mixed with cadmium; the
radiated by an acoustic generator.
electrolyte is potassium hydroxide. The open-
228 effective actuation time • effective phase angle

effective actuation time The total actuation time effective cutoff frequency For a filter or similar
of a relay (i.e., the sum of the initial actuation device operated between specified impedances,
time and subsequent intervals of contact the frequency at which insertion loss is higher
chatter). than the loss at a specified reference frequency in
effective address The address a computer uses in the passband.
implementing an instruction (i.e., one not neces- effective field intensity The root-mean-square
sarily coinciding with the address given in the in- (rms) value of the field-strength voltage, averaged
struction). for all points at a horizontal distance of one mile
effective ampere An effective current of 1 ampere. from a transmitting antenna.
Also see EFFECTIVE CURRENT. effective height The height of an antenna in terms
effective antenna length See ELECTRICAL of its performance as a transmitter or receiver of
LENGTH. electromagnetic energy.
effective antenna resistance The radiation resis- effective input capacitance The actual operative
tance of an antenna, as measured at the input capacitance present at the input terminals of a
point. circuit or device, caused by the shunt capaci-
effective bandwidth The bandwidth of an ideal tance of the terminals themselves and the net
bandpass filter, which, at a reference frequency, capacitance of the circuit connected to the
has the same transfer ratio as an actual band- terminals.
pass filter under consideration; it also has the effective internal resistance In an electrochemi-
same current and voltage characteristics. cal cell or battery, a resistance that originates
within the electrolyte and electrodes. This resis-
tance is low when the current drain is low; it rises
Effective as the current drain increases. It limits the max-
bandwidth imum current that the cell or battery can deliver.
effective isolation The condition of components
or circuits being so well isolated or shielded that
Theoretical no significant direct coupling, capacitive cou-
pling, or inductive coupling exists between them.
effective instruction The machine-language ver-
sion of an instruction given in a computer pro-
gram, as produced by resident software.

effectively bonded The condition afforded by an
extremely low-resistance union between two con-
ducting surfaces that are solidly fastened to-
effectively grounded The condition of being con-
nected to earth or to the low-potential end of a
circuit by means of an extremely low-resistance
effective parallel capacitance Inherent capaci-
tance that manifests itself in parallel with two cir-
cuit points in combination with any lumped
effective bandwidth
effective parallel resistance 1. The leakage resis-
tance that manifests itself in parallel with a
effective capacitance The actual capacitance be-
dielectric (e.g., the leakage resistance of a
tween two points in a circuit resulting from the
capacitor). 2. Parallel-resistance effects caused
combination of inherent, lumped, and stray ca-
by stray shunt-resistance components.
effective percentage of modulation For a com-
effective conductivity Conductivity measured be-
plex waveform, an expression of the equivalent
tween the parallel faces of a unit cube of a mate-
percentage of modulation by a pure sine wave.
Given a certain proportion of power in the side-
effective confusion area In a radar system, an
bands with modulation by a complex signal, the
area in which interference makes it impossible to
effective percentage of modulation is that per-
see whether a target is present.
centage which, when the modulating signal is si-
effective current Symbol, Ieff. The root-mean-
nusoidal, results in the same proportion of power
square (rms) value of alternating current (see
in the sidebands.
EFFECTIVE VALUE). For a sinusoidal current,
effective phase angle In alternating-current (ac)
Ieff = 0.707Imax, where Imax is the maximum value
circuits, the phase angle, with respect to wave-
of the current. Also called rms current.
forms for current and voltage. When both wave-
effective cutoff See EFFECTIVE CUTOFF FRE-
forms are sinusoidal, the effective phase angle is
effective phase angle • eight-level code

the actual phase angle. But when harmonics are effective value an alternating current produces in
present in current or voltage, the angles differ, a pure resistance has the same heating effect as
the difference being greater in capacitive circuits the equivalent direct current. See also ROOT
than in inductive circuits. MEAN SQUARE.
effective radiated power Abbreviation, ERP or effective volt An effective potential of one root-
PER. 1. A measure of the performance of a wireless mean-square (rms) volt. Also see EFFECTIVE
transmitting antenna. Suppose a test antenna, VOLTAGE.
AT, is set up and the field strength in its favored effective voltage Symbol, Eeff. The root-mean-
direction at a frequency f is measured at a dis- square value of alternating-current (ac) voltage
tance d in free space. Let the field strength thus (see EFFECTIVE VALUE). For a sinusoidal volt-
measured be F watts per square meter. Suppose age, Eeff = 0.707Emax, where Emax is the maximum
AT is replaced with an isotropic radiator, AI, and value of the voltage. Also called rms voltage.
the field strength at the same frequency f is mea- effective wavelength Wavelength in terms of mea-
sured at the same distance d in free space. Let sured frequency and effective propagation velocity.
the radio-frequency (RF) power at the feed point effects processor In audio systems, a circuit that
of the isotropic radiator AI be varied until the field produces various sound effects via digital signal
strength is F, the same as it was with the test an- processing.
tenna AT. Let this RF power be symbolized P. efficiency 1. The ratio of useful power or energy
Then P is defined as the effective radiated power output to total power or energy input to a device
(ERP or PER) of the test antenna, AT. 2. The figure or system. 2. The proportion of applied audio-
defined as in (1), measured in some direction frequency (AF) power that a loudspeaker converts
other than the favored direction of a test antenna. into acoustic energy. 3. See ELECTRICAL EFFI-
effective resistance 1. In a coupled circuit, the CIENCY.
sum of the actual resistance of the circuit and the efficiency modulation A system of amplitude
reflected resistance of the load. 2. See EFFEC- modulation in which the efficiency of a radio-
TIVE ANTENNA RESISTANCE. frequency (RF) power amplifier is varied at an au-
effective series inductance Inherent (distribu- dio-frequency (AF) rate.
ted) inductance acting in series with other com- efficiency of rectification For a rectifier, the ratio
ponents in a circuit. The inherent inductance of of the direct-current (dc) output voltage to the
the wire in a wirewound resistor, for example, peak value of alternating-current (ac) input volt-
manifests itself in series with the resistance of the age. For percent efficiency, the ratio is multiplied
device. by 100.
effective series resistance Inherent (distributed) efflorescence The giving up of water by a sub-
resistance acting in series with other components stance upon exposure to air. Some materials used
in a circuit. Thus, the inherent resistance of the in electronics exhibit this property. Common efflo-
wire in a coil appears in series with the induc- rescent compounds are hydrated ferrous carbon-
tance of the coil. Likewise, a capacitor has an ef- ate, ferrous sulfate, and sodium carbonate.
fective series resistance because of the resistance efflorescent material A material exhibiting efflo-
of the leads, plates, and connections. rescence. Compare DELIQUESCENT MATERIAL.
effective shunt capacitance See EFFECTIVE E field 1. An electric field. 2. the electric-field com-
PARALLEL CAPACITANCE. ponent of an electromagnetic wave.
effective shunt resistance See EFFECTIVE PAR- EFL Abbreviation of emitter-follower logic.
effective sound pressure The root-mean-square EHD Abbreviation of electrohydrodynamic(s).
(rms) value of instantaneous sound pressure at EHF Abbreviation of EXTREMELY HIGH FRE-
one point in a sound cycle. QUENCY.
effective speed of transmission In telegraphy EHP Abbreviation of effective horsepower.
(wire or radio) and in electronic data transmis- E-H tee A waveguide junction in which E- and
sion, the transmission speed (characters per H-plane tee junctions intersect the main wave-
minute, bits per second, etc.) that can be reliably guide at the same point. Also see WAVEGUIDE
maintained for a given period. TEE.
effective thermal resistance The effective tem- E-H tuner An impedance-transforming E-H tee
perature rise (in degrees per watt of dissipation) with two arms that are terminated in tunable
of a semiconductor junction above an external plungers for critical adjustments. See WAVE-
reference temperature that is at equilibrium. GUIDE PLUNGER.
effective time For a computer, the time during EHV Abbreviation of extra-high voltage.
which useful work is performed. Ei Symbol for INPUT VOLTAGE.
effective transmission speed See EFFECTIVE EIA Abbreviation of Electronics Industries Associa-
effective value The root-mean-square (rms) value eight-level code A code, such as the American
of an alternating-current (ac) quantity. The Standard Code for Information Interchange (ASCII),
230 eight-level code • electret microphone

in which each character is represented by eight tolerated by a material without being perma-
bits. nently deformed.
E indicator A radar elevation display, in which the elastic wave A wave in an elastic medium, such as
horizontal scale shows range and the vertical air or water; thus, a wave that is mechanically
scale shows elevation. produced.
Einstein equation The equation depicting the
interconversion of mass and energy; E = mc2,
where E is energy (ergs), m is mass (grams), and c
is the speed of light in a vacuum (centimeters per
einsteinium Symbol, Es. A radioactive element
produced artificially. Atomic number, 99. Atomic
weight, 252.
Einstein/Dehaas effect The tendency for an iron
or steel cylinder to become magnetized as it ro-
Einstein shift The decrease in frequency and loss
of energy experienced by quanta acted upon by
Einthoven string galvanometer A simple gal-
vanometer in which a silvered glass filament car-
rying current is mounted in a magnetic field set
up by either a permanent magnet or an electro-
elastic waves
magnet. The current causes the filament to be de-
flected through a distance proportional to current
strength, the deflection being observed through a elastivity 1. Specific elastance (i.e., the elastance
microscope. in darafs per cubic unit of a dielectric). 2. The ra-
EIT Abbreviation of engineer-in-training. tio of electric stress to displacement.
either-or operation The logical inclusive-OR oper- elastomer A compressible, conducting substance
ation. used in pressure sensing. In one arrangement, an
EJC Abbreviation of Engineers™ Joint Council. array of electrodes is connected to each side of a
eka-aluminum See GALLIUM. pad of the material. When pressure appears at
eka-silicon See GERMANIUM. some point, the material compresses, lowering
EKG Abbreviation of ELECTROCARDIOGRAM. the resistance in the pressure zone. A micropro-
(Also, ECG.) cessor determines the location and extent of the
EKG telemetry See ECG TELEMETRY. pressure.
EL Abbreviation of ELECTROLUMINESCENCE. E layer A layer in the ionosphere that is 50 to 90
elapsed time 1. In data-processing and computer miles above the surface of the earth, and is noted
operations, what appears to be the duration of a for returning radio waves at high and very-high
process, compared with actual processing time, frequencies.
as measured by internal clocks, for example. elbow bend A 90-degree bend in a waveguide.
2. The accumulated time, usually expressed in ELD Abbreviation of edge-lighted display.
hours, minutes, and seconds, that an operation electra A radio-navigational system in which
takes or a machine runs. equal-intensity signal zones (usually 24) are pro-
elapsed-time meter An instrument that indicates vided.
the time an electronic device or system has been electralloy A nonmagnetic alloy used in the manu-
in operation. Most such meters are based on elec- facture of radio hardware, such as chassis.
tric clockwork that runs only while the system is electre See ELECTRUM.
in operation, holding the count during shutdown electrepeter A device used to change the direction
periods. Also see ELECTROLYTIC ELAPSED- of an electric current.
TIME METER. electret A device whose heart is a dielectric disk or
elastance Unit, daraf. The opposition of a capaci- slab that is permanently polarized electrically,
tor to being charged. It is the reciprocal of capac- and so possesses a permanent electric field. The
itance. electrical equivalent of the permanent magnet.
elastic collision A collision between two charged Certain waxes, ceramics, and plastics acquire
particles in which neither loses energy”even permanent polarization after they have been
though they are deflected from their normal paths. heated, then cooled slowly in an intense electric
elasticity 1. The ability of a body to return to its field.
original shape after being deformed. See electret microphone Also called electret capacitor
YOUNG™S MODULUS. 2. See ELASTIVITY. microphone. A microphone in which sound
elastic limit The maximum stress that can be waves cause an electret to vibrate and generate
electret microphone • electrical engineer

audio-frequency (AF) output current. An inter- electrical bias A current maintained in a relay coil
nal power supply (such as a battery) supplies (sometimes an auxiliary coil) to keep the relay
the necessary voltage. partially closed, thus sensitizing it. Compare ME-
electric 1. Pertaining to electricity and its various CHANICAL BIAS.
manifestations. 2. See ELECTROSTATIC. electrical boresight In radar operations, the
electric absorption See DIELECTRIC ABSORP- tracking axis, as determined by an electrical test,
TION. such as one involving a sharp null or sharp peak
electric accounting machine A self-contained response.
data-processing machine that is neither a com- electrical center The point at which an adjustable
puter nor a computer peripheral. component (variable resistor, variable inductor,
electrical-acoustical transducer A transducer, etc.) has exactly half its total value. This point
such as a headphone, sonic applicator, or buzzer, does not always coincide with the physical center.
that converts electrical energy into sound energy. electrical conductance See CONDUCTANCE.
Compare ACOUSTICAL-ELECTRICAL TRANS- electrical conduction The flow of charge carriers
DUCER. through a material. The degree of conduction is
electrical angle The angle assumed at any instant indicated by the material™s value of conductance.
by the rotating vector representing an alternating electrical conductivity See CONDUCTIVITY.
current or voltage. A complete cycle is divided electrical coupling The coupling of two or more
into 360 electrical degrees. Thus, for an alternat- circuits or elements by means of electric-field ef-
ing-current (ac) sine wave, the angle is 0 degrees fects.
for zero and positive-going, 90 degrees for positive electrical degree 1. In a periodic waveform, the
length of time corresponding to 1„360 of the time for
maximum, 180 degrees for zero and negative-
going, and 270 degrees for negative maximum. completion of one cycle. 2. In space, that dis-
tance representing 1„360 of the wavelength in the
medium through which electromagnetic energy
electrical discharge The flow of current out of a
+ voltage reservoir, such as a battery or capacitor.
electrical discharge in gases The phenomenon of
electric conduction (current) by a gas, caused by
sudden breakdown as a result of gas ionization.
θ The discharge is often accompanied by light, as in
’ + Rate of the red glow of a neon bulb.
electrical-discharge machining A method of ma-
chining metals in which the metal is vaporized by
an arc formed between an electrode and the metal
workpiece (anode). In this way, metal is removed
in tiny bits from the surface of the workpiece.
’ electrical distance Distance in terms of the time
required for an electromagnetic wave to travel be-
electrical angle tween two points in a particular medium.
electrical drainage The diversion of electric cur-
rents away from underground pipes to prevent
electrical attraction The attraction between two
corrosion by electrolysis.
oppositely charged bodies or particles. Compare
electrical efficiency The ratio of the output of an
electrical or electronic device to the total input. It
electrical axis In a quartz crystal, the axis through
can be expressed as a decimal or percentage. For
opposite corners of the hexagonal cross section.
example, for a bipolar transistor amplifier, the
The various electrical axes are x, x™, and x” (or x-
percent efficiency is equal to 100(Pout/Pin), where
x, x™-x™, and x”-x”). The electrical axis is perpen-
Pin is the collector input in volt-amperes, and Pout
dicular to the mechanical axis, which runs
is the output power in watts.
through the crystal™s length. Also see CRYSTAL
electrical elasticity See CAPACITANCE.
AXES and X-AXIS, 2.
electrical element See ELEMENT, 2.
electrical bail An action in which a special switch
electrical energy Energy in the form of electricity
changes contact position and locks itself in that
(see ELECTRICITY, 1). The term is often used in
position after a station has been actuated, at the
same time releasing a previously actuated sta-
electrical engineer Abbreviation, EE. A trained
professional skilled in applying physics and math-
electrical bandspread In a tuned circuit, band-
ematics to electricity, and in the theory and appli-
spread obtained by changing values of induc-
cation of basic engineering and related subjects.
tance or capacitance, rather than by mechanical
Of particular interest to the EE are the generation
232 electrical engineer • electrical transducer

and distribution of electrical energy and the de- electrical network A circuit containing two or
sign and application of electromechanical devices. more components (including generators and
Compare ELECTRONICS ENGINEER. loads), usually arranged in some pattern.
electrical erosion In electrical contacts, the loss of electrical noise Extraneous currents and/or volt-
metal as a result of the evaporation or transfer of ages that interfere with desired electrical quanti-
metal during switching. ties. Compare ACOUSTIC NOISE.
electrical filter A bandpass, band-rejection, high- electrical polarity The distinct difference observ-
pass, or low-pass filter that operates by electrical able in electrification, designated positive (or
means. Examples: Butterworth filter and Cheby- plus) and negative (or minus). Negative electrifi-
shev filter. cation is generally characterized by a surplus of
electrical forming See ELECTROFORM, 1. electrons; positive electrification is characterized
electrical gearing In an electromechanical sys- by a deficiency of electrons.
tem, such as a servo, the condition in which an electrical quantity 1. See COULOMB and QUAN-
output shaft is electrically rotated at a speed dif- TITY, 3. 2. An electrical unit (e.g., AMPERE,
ferent from that of an input shaft. OHM, VOLT, and WATT).
electrical glass High-temperature insulating ma- electrical repulsion The mutual repulsion of bod-
terials made from glass fibers. ies or particles having similar electric charges.
electrical inertia See INDUCTANCE. Two positively charged objects will repel each
electrical initiation 1. Starting an action (electri- other, as will two negatively charged objects.
cal or nonelectrical) by means of an electrical sig- electrical reset An electromechanical device for
nal. 2. Using an enabling pulse. resetting a relay that ordinarily remains in the
electrical instrument A device for measuring an position resulting from actuation.
electrical quantity (such as voltage, current, or electrical resistance The in-phase current-
power). retarding effect that all conductors exhibit to
electrical interlock Also called an interlock switch some extent. Also see RESISTANCE.
or door-interlock switch. A door- or lid-operated electrical resistivity See RESISTIVITY.
switch connected in series with the power switch electrical resolver A synchro whose rotor has two
of a piece of equipment. The interlock causes perpendicular windings in addition to another
power to be removed from internal circuits when- winding.
ever the door is opened, the lid lifted, or the case electrical scan A method of changing the orienta-
removed. This minimizes the chance for electric tion of the major lobe of an antenna. The antenna
shock to occur to service personnel. is kept physically stationary, but the phase/
electrical length The length, in wavelengths, of an amplitude relationships of the signals applied to
antenna or transmission line. The electrical different driven elements are varied.
length usually differs from the actual length be- electrical sheet Sheet iron or steel used for motor
cause of ground-capacitance effects, end effects, laminations.
and the speed of electromagnetic waves in con- electrical system 1. The overall configuration of
ductors and/or dielectrics. electrical elements for a set of apparatus. 2. The
electrical load A device connected to a source of wiring system that supplies power to a set of de-
electricity (generator, amplifier, network, etc.) for vices. 3. One of several methods of quantizing
a useful purpose (heat, work, etc.). electrical properties, such as METER-KILOGRAM-
electrically connected Connected via direct path, SECOND (mks), CENTIMETER-GRAM-SECOND
such as through a wire, resistance, inductance, (cgs) electromagnetic, cgs electrostatic, and the
electrically erasable PROM A programmable electrical taste See GALVANIC TASTE.
read-only memory (PROM) that can be erased by electrical technology The theory and practical
an electrical signal, rather than by exposure to application of electricity. Taught as a subengi-
ultraviolet light. Also see PROM and ROM. neering major, usually in two-year colleges that
electrically variable capacitor See VOLTAGE- award the degree of Associate in Arts (AA) or As-
VARIABLE CAPACITOR. sociate in Science (AS).
electrically variable inductor An inductor whose electrical time constant For a torque motor, the
value varies inversely with the amount of direct ratio of armature inductance to effective arma-
current that is caused to flow through it or ture resistance. Compare MECHANICAL TIME
through an auxiliary winding on the same core. CONSTANT.
electrically variable resistor See VOLTAGE- electrical transcription 1. A phonograph record
DEPENDENT RESISTOR. made electrically, as opposed to one made me-
electrical nature of matter The general behavior chanically. 2. A radio program in which such a
of matter as a complex interplay of waves and record is played. 3. Any direct mechanical or elec-
particles. Also see ELECTRON THEORY OF MAT- trical recording of an audio signal.
TER, WAVE MECHANICS, and WAVE THEORY electrical transducer 1. A transducer that converts
OF MATTER. a nonelectrical phenomenon into a proportional
electrical transducer • electric column

current, voltage, or frequency. 2. A transducer electric and magnetic double refraction See
that converts electricity in one form to electricity in KERR ELECTRO-OPTICAL EFFECT and KERR
another [e.g., a transducer actuated by direct- MAGNETO-OPTICAL EFFECT.
current (dc) voltage, delivering an alternating- electric arc A sustained luminous discharge in the
current (ac) output, whose frequency is space between two electrodes. Compare ELEC-
proportional to the dc input voltage]. TRIC SPARK.
electrical twinning A defect in which two quartz electric aura See ELECTRIC WIND.
crystals intergrow in such a way that the electri- electric balance See BRIDGE, 1 and 2.
cal sense of their axes becomes reversed. Com- electric bell See BELL.
pare OPTICAL TWINNING. electric brazing A method of brazing in which
electrical unit A standard for measuring an elec- electric current generates the required heat.
trical quantity (e.g., ampere, ohm, volt, watt, electric breakdown 1. The usually sudden ioniza-
siemens, etc.). tion of a gas by an electric field and the accompa-
electrical wavelength The distance between one nying heavy current flow through the gas. 2. The
point in an electromagnetic wave cycle and the (destructive) puncture of a dielectric by the strain
next identical point. This is usually expressed as produced by high voltage. Also see DIELECTRIC
the separation between points where the instan- STRENGTH. 3. The usually nondestructive,
taneous amplitude of the electric field is zero and abrupt increase in semiconductor junction cur-
increasing positively. This quantity depends on rent at a high reverse voltage. See, for example,
the velocity factor, ν, of the medium through, or AVALANCHE BREAKDOWN.
along, which the field propagates. The electrical electric breakdown voltage 1. The voltage at
wavelength also depends on the frequency, f, of which avalanche effect occurs. 2. Dielectric
the energy. In a transmission line with a velocity strength.
factor ν (given as a fraction rather than as a per- electric breeze See ELECTRIC WIND.
centage), the electrical wavelength » is given by electric buzzer See BUZZER. Compare ELEC-
» = 3.00 — 108 ν / f
electric calculator An electrically driven machine
where s is in meters, ν is in meters per second, for performing mathematical operations. Its elec-
and f is in hertz. Often, this formula is modified tromechanical nature distinguishes it from the
for values of f expressed in megahertz (Mhz) electronic calculator, which features no moving
rather than in hertz. The equation in this case parts, other than keys. Also see CALCULATOR.
becomes electric catfish A fish native to tropical and north-
» = 300 ν / f ern Africa, capable of delivering a strong electric
The wavelength of a signal in a radio-frequency
electric cell See CELL, 1.
(RF) transmission line is always less than the
electric chair An electrode-bearing chair used in
wavelength of the same signal in free space.
some states for administering the death penalty
via high-voltage electricity. See ELECTROCU-
electric charge Potential energy as the electrifica-
tion of a body or component. For a capacitance of
field intensity

C farads charged to a potential of E volts, the

Direction charge Q, in coulombs, is equal to the product
propagation electric chronograph An instrument for accu-
rately recording time intervals.
electric chronometer A precision electric or elec-
» tronic timepiece. Also see ELECTRIC CLOCK and

electric circuit A network of interconnected com-
electrical wavelength ponents and devices, often including a source of
electric power. Current flowing through a circuit
is acted on by components, which produce spe-
electrical zero 1. A zero-output or minimum-
cific desired effects.
output point resulting from the adjustment of a
electric clock A clock driven by electric current.
bridge or other zero-set circuit. 2. In a meter
Electric clocks fall into two categories: those
whose pointer is mechanically set to some point
driven by synchronous alternating-current (ac)
above or below the zero on the scale, the zero set-
motors, and those driven by stepping mecha-
ting obtained when the meter is deflected to scale
nisms that usually operate from direct current
zero by a current or voltage. 3. For a synchro, the
position at which the amplitudes and time phase
electric column See VOLTAIC PILE.
of the outputs are defined.
234 electric conduction • electric generator

electric conduction The flow of current carriers
through a conductor.
electric constant Also called permitivity of vac-
uum. The fixed electrical permitivity of free space,
the value of which is 8.8542 — 10“12 farad per
electric contact See CONTACT, 1, 2.
electric controller An adjustable device for modi-
fying the operating voltage or power of a com-
ponent or system. Compare ELECTRONIC
electric cooling 1. Cooling via PELTIER EFFECT.
cooling (of equipment) by electric blowers or fans.
electric current The phenomenon wherein charge
carriers move in a directed manner through a
material or vacuum. In most electrical conduc-
tors, current results from movement of electrons.
In a semiconductor material, electric current can
result from the movement of holes, as well as
electrons; the proportion of holes to electrons de-
pends on the nature of the semiconductor. In a
gas or electrolyte, current consists of a flow of electric fidelity The frequency response of a cir-
ions. In certain situations, electric currents can cuit or device.
result from the movement of positrons, protons, electric field The space surrounding an electric
anti-protons, alpha particles, and various atomic charge or charged body, in which electric energy
nuclei. acts (electric lines of flux fill the space).
electric current density See CURRENT DENSITY. electric field intensity See ELECTROSTATIC
electric delay line See DELAY LINE. FIELD INTENSITY.
electric density See ELECTRIC SPACE DENSITY electric field strength 1. Symbol, E. In an electro-
and ELECTRIC SURFACE DENSITY. magnetic wave, the amplitude of the electric com-
electric dipole A pair of equal charges having op- ponent of the field, expressed in volts per meter.
posite polarity and separated by a fixed distance. 2. Dielectric strength.
electric discharge See ELECTRICAL DISCHARGE. electric-field vector See ELECTRIC-FIELD
electric-discharge lamp See DISCHARGE LAMP. STRENGTH, 1.
electric disintegration See ELECTRIC DISPER- electric filter See ELECTRIC WAVE FILTER.
SION. electric fish Fish capable of generating intense elec-
electric dispersion In a colloidal suspension, dis- tric shocks (e.g., electric catfish and electric eel).
persion accomplished by passing an electric cur- electric flux See ELECTROSTATIC FLUX.
rent through the material. electric flux density Symbol, D. In an electric
electric displacement The movement of a body or field, the number of lines of flux per unit area,
particle in response to an electric current or field. usually expressed in coulombs per square meter.
electric double refraction See KERR ELECTRO- electric flux lines The direction of the electric field
OPTICAL EFFECT. in the vicinity of a charged object. The field is de-
electric dust precipitator See DUST PRECIPITA- noted by means of “lines of flux” or “lines of
TOR. force,” with each line representing a designated
electric eel An eel (fish) capable of delivering a dis- electric field intensity. The closer together the
abling shock on contact. lines, the more intense the field in a given region.
electric elasticity See ELASTIVITY, 1, 2. electric focusing See ELECTROSTATIC FOCUS-
electric endosmosis See ELECTRO-OSMOSIS. ING.
electric eye A sensing device that uses a radiant electric force The force exerted by an electrically
energy beam to detect objects. It generally uses a charged particle or an electric field.
laser diode as the beam source, and a photoelec- electric forces The forces exerted by electric
tric cell, phototransistor, or photovoltaic cell as charges or electric fields. Also see UNIT ELEC-
the beam detector. The output is used to control TROSTATIC CHARGE.
some external machine or system. electric furnace An electrically heated chamber
electric fence A wire fence through which an elec- (sometimes heated by an electric arc) used in ore
tric current is passed. Anyone touching the fence reduction, carbide manufacture, and other high-
will receive a shock. It is used in some prisons, temperature processes.
and also by cattle ranchers to keep people or an- electric generator A device for producing elec-
imals contained. tricity. Thus, many different devices, such as bat-
electric generator • electric residue

electric machine A mechanical device for generat-
ing static electricity. See, for example, ELEC-
electric meter 1. An instrument such as an am-
meter, voltmeter, or wattmeter, used to indicate
an electrical quantity (usually directly). 2. See
electric mirror See ELECTRON MIRROR.
electric moment In an electric field of unit inten-
+ ’
sity, the maximum torque exerted on an electric
electric motor A machine that converts electrical
energy into mechanical work. The familiar form is
a machine in which an armature rotates between
the poles of a field magnet, mechanical energy be-
Flux ing produced at the armature™s revolving shaft.
lines electric needle A needle electrode carrying high-
frequency current; it is used in surgery to cut tis-
sue and sear it immediately to prevent bleeding.
electric flux lines
electric network See ELECTRICAL NETWORK.
electric organ See ELECTRONIC ORGAN.
electric oscillations The alternate flow of electric
charges in opposite directions, occurring at a de-
teries, dynamos, oscillators, solar cells, and ther-
fined frequency or frequencies.


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