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( 42)


elemental area In a facsimile or television picture,
a scanning line segment as long as the line™s
elemental charge See ELEMENTARY CHARGE.
elemental semiconductor A semiconductor con-
taining one undoped chemical element.
elementary charge Symbol, e. Also called unit
electric charge. The electric charge of a single
electron or proton. This charge is approximately xo
equal to 1.6022 — 10“19 coulomb.
elementary particle 1. A minute charged or un-
charged particle within the atom (i.e., electron,
proton, neutron, quark, etc.). 2. In theory, a sub-
atomic particle that cannot be broken down into ellipse
smaller particles.
element error rate In communications or data
elliptically polarized wave An electromag-
transfer, the ratio ni/nt, where ni is the number of
netic wave in which the rotation of the electric-
elements received incorrectly and nt is the num-
intensity vector at one point describes an ellipse.
ber of elements transmitted.
elliptical orbit A satellite orbit that is not a perfect
element spacing 1. The spacing between radiator,
circle. In theory, all satellites deviate slightly from
director, and reflector elements in a directional
perfectly circular orbits. Sometimes a satellite is
antenna. 2. The spacing between the internal
deliberately put into an orbit that is greatly elon-
electrodes of a vacuum tube.
gated. The closer the satellite is to the earth, the
elevation Angular position (in degrees) of a point
faster it moves.
above the horizontal.
elliptical polarization Polarization characterized
elevation-position indicator A type of radar dis-
by elliptical rotation of the wave vector at a given
play simultaneously indicating the elevation of,
and the line-of-sight distance to, the target.
elliptical stylus In a phonograph (turntable) sys-
elevator control 1. An electronic system for auto-
tem, a stylus with a characteristic ellipsoidal
matically stopping an elevator and opening the
doors. Various safety functions are included, an
elliptic filter A band-pass, band-stop, high-pass,
example being the reopening of a closing door
or low-pass inductance-capacitance (LC) filter,
when a passenger steps into the car. 2. In an air-
designed according to an ELLIPTIC FUNCTION.
craft, the mechanical, electronic, or electrome-
Characterized by a steep attentuation-versus-
chanical devices or circuits involved in actuation
frequency cutoff response with ripple in both the
of the elevators.
passband and the stopband.
ELF Abbreviation for EXTREMELY LOW FRE-
elliptic function A function, similar to the
Chebyshev and Butterworth functions, used in
eliminator 1. A device or circuit acting as a surro-
the design of certain selective filters. The elliptic
gate for an inconvenient or undesirable compo-
function results in a better filter magnitude re-
nent (e.g., battery eliminator). 2. A device for
sponse than the Chebyshev or Butterworth
removing or minimizing an undesirable signal or
functions in some applications. See ELLIPTIC
quantity (e.g., harmonic eliminator); interference
elongation A form of modulation distortion result-
ell A coaxial fitting that is a right-angle line section
ing from multipath propagation. Some of the
with a coaxial connector at each end. It takes its
paths result in greater propagation delay than
name from its L shape.
other paths; this causes the modulation envelope
ellipse A geometric figure having the Cartesian-
plane formula (x “ x0)2/a2 + (y “ y0)2/b2 = 1, where to spread out. The higher the modulating fre-
quency, the greater the effect.
a and b are constants, and xo and y0 represent
ELSE A word used in a BASIC computer program
the center point.
that provides an instruction based on a relational
elliptical filter See ELLIPTIC FILTER.
test and, in this respect, is related to IF-THEN,
elliptical function See ELLIPTIC FUNCTION.
ON-GOTO, etc. It specifies the operation to be
elliptical load line For any amplifier with an out-
done if the conditions given in the same program
put transformer, a load line in the shape of an el-
line don™t occur.
lipse, obtained when the load connected to the
ELSIE Abbreviation of electronic letter-sorting and
output element is reactive, rather than purely re-
indicator equipment.
EM • emissivity

EM 1. Abbreviation of EFFICIENCY MODULATION. emergency service A communications service de-
2. Abbreviation of ELECTROMAGNETIC(S). 3. Ab- voted exclusively to emergency communication.
breviation of electromagnetic iron. 4. Abbreviation EMF, emf Abbreviation of ELECTROMOTIVE
of ELECTROMAGNETIZER. 5. Abbreviation of FORCE.
ELECTRON MICROSCOPE. 6. Abbreviation of EX- emf standard See STANDARD CELL.
POSURE METER. 7. Abbreviation of electromotive. EMG 1. Abbreviation of ELECTROMYOGRAM. 2.
Em 1. Symbol for MAXIMUM VOLTAGE. 2. Symbol Abbreviation of ELECTROMYOGRAPH.
emanation 1. Emission of electrons. 2. Emission FERENCE.
of radioactive particles or ionizing radiation. 3. E microscope See ELECTRON MICROSCOPE.
Emission of electromagnetic energy. emission 1. The ejection of particles, especially
Emax Symbol for MAXIMUM VOLTAGE. electrons, from a material. 2. Waves radiated
embedded path A means of guiding a mobile robot from any source (as from a transmitting antenna
along a specific route. One common scheme uses or from an amplifier stage). 3. The emanation of
a buried, current-carrying wire that produces a radiant, electromagnetic, acoustical, electrical, or
magnetic field. The robot can sense and follow magnetic energy.
this field. Colored paints and tapes can also be emission code A system of abbreviating the various
used in conjunction with machine vision sys- types of radio emission. See EMISSION MODE.
tems. Compare EDGE DETECTION. emission frequency 1. In communications, the
embedded training The inclusion of training/ carrier frequency of the transmitted signal as it is
tutorial programs in computerized equipment radiated from the antenna or fed into a transmis-
that assist users in the operation of the equip- sion line. 2. The actual frequency or frequency
ment. range of a signal as it is transmitted or radiated.
embedding See ENCAPSULATION. This might be the carrier frequency. 3. The fre-
embossed-foil printed circuit A printed circuit quency of energy in an emission band or bands in
made by pressing the pattern from metal foil into a spectrum.
the insulating substrate and then removing the emission lines In a spectrum, radiation intensity
surplus foil. peaks that appear as bright lines in a visible dis-
embossed-groove recording 1. A phonograph play. In a radio-frequency spectrum, the emission
record into which grooves are embossed, rather lines occur as sharp peaks in radiated energy at
than scribed. 2. Recording sound by embossing specific wavelengths.
grooves on record disks. emission mode Any of various official classifica-
embossing stylus The rounded-tip stylus used to tions of radio communication emission types.
make an embossed-groove recording. Emissions are designated according to the modu-
EMC Abbreviation of ELECTROMAGNETIC COM- lation method used (e.g., continuous waves,
PATIBILITY. amplitude modulation, single-sideband with
EME Abbreviation of earth-moon-earth. See MOON- suppressed carrier, frequency modulation, pulse
BOUNCE. modulation, etc.).
e/me The ratio of the elementary electron charge to emission power 1. The rate at which energy is ra-
its mass: 1.7588 — 1011 coulombs per kilogram. diated from an object. 2. In radio communication,
Also see CHARGE-MASS RATIO. the transmitter output power.
Emergency Broadcast System In the United emission spectrum The radiation spectrum of a
States, a general plan for dissemanating informa- substance that emits energy (e.g., the light spec-
tion via broadcast stations in the event of a na- trum of an incandescent metal).
tional emergency. emission types See EMISSION MODE.
emergency channel A communication channel al- emission velocity The initial velocity of an elec-
located for emergency service. tron as it leaves an emitting surface.
emergency communication Radio or other elec- emission wavelength 1. In communications, the
tronic transmission and reception of urgent mes- carrier wavelength of the transmitted signal as it
sages (e.g., distress signals, storm warnings, is radiated from the antenna or fed into a trans-
etc.). mission line. 2. The actual wavelength or wave-
emergency equipment 1. Apparatus kept in length range of a signal as it is transmitted or
standby status for immediate operation when radiated. This might or might not be the carrier
regularly used equipment fails. 2. Equipment, es- wavelength. 3. The wavelength of energy in an
pecially vehicular, for use in emergency situa- emission band or bands in a spectrum.
tions. Examples are ambulances, fire-fighting emissive power The rate at which a surface emits
trucks and equipment, etc. energy of all wavelengths in all directions, per
emergency power supply An alternating-current unit area of radiating surface, regardless of tem-
(ac) or direct-current (dc) power unit kept in perature.
standby status for immediate use when the regu- emissivity For a radiating source, the ratio
lar power supply fails. W1/W2, where W1 is the energy emitted by the
256 emissivity • empirical design

source at a particular temperature, and W2 is the current degeneration obtained by use of an unby-
energy emitted by a blackbody (i.e., a theoreti- passed emitter resistor. The arrangement results
cally perfect radiator) at the same temperature. in virtually distortion-free amplification at a sac-
emittance For an energy-radiating source, the ra- rifice in voltage gain.
diated power per unit area of radiating surface. emitter follower A transistor circuit in which the
emitted electron An electron that has left an atom input signal is applied to the base, and the output
of a material and has escaped into surrounding signal is taken from the emitter resistor. Gain is
space or entered a neighboring material. always less than unity; output impedance is low.
emitter 1. A body that discharges particles or
waves (see EMISSION). 2. In a semiconductor de-
vice, the area, region, or element from which cur-
rent carriers are injected into the device. In a
transistor symbol, the emitter is that electrode
shown with an arrowhead.
emitter-base junction In a bipolar transistor, the
boundary between base and emitter regions.
emitter bias Emitter current or voltage main-
tained to set the operating point of a bipolar tran-

emitter bulk resistance The portion of the resis-

tance of the semiconductor material in a transis-
tor that affects emitter resistance.
emitter-coupled logic A bipolar form of digital
logic, abbreviated ECL.
emitter-coupled multivibrator A two-transistor
multivibrator circuit in which the emitters share
a common resistor. emitter follower
emitter-coupled phase inverter A transistor
phase inverter in which the out-of-phase compo-

nent is taken from the collector and the in-phase emitter-input circuit See COMMON-BASE CIR-
component from the emitter resistor (of the same CUIT.
transistor). Another transistor is often used to emitter junction See EMITTER-BASE JUNCTION.
amplify the in-phase component so that both out- emitter resistance Symbol, RE. 1. The resistance
puts are equal in magnitude. of the emitter electrode in a bipolar transistor. 2.
External resistance connected to a transistor™s
emitter terminal.
+dc emitter stabilization In a common-emitter tran-
sistor stage, an emitter resistor that stabilizes the
circuit against temperature variations.
emitter-to-base junction See EMITTER-BASE
emitter voltage Symbol, VE. The voltage at the
emitter electrode of a bipolar transistor.
EMP, emp 1. Abbreviation of ELECTROMAGNETIC
PULSE. 2. Abbreviation of electromagnetic power.
emphasis Modification of the amplitude-versus-
frequency output or response of an audio circuit,
for the purpose of optimizing signal intelligibility.
emphasizer An audio-frequency device with a spe-
cially tailored response, intended to maximize in-
telligibility of a voice.
Empire cloth Varnished cambric used as an insu-
lating sheet or tape.
empirical Observable; derived from experimenta-
empirical curve A curve plotted from data ac-
emitter-coupled phase inverter
quired from observations, tests, and calculations,
rather than from mathematical laws or other the-
emitter current Symbol, IE. The current in the ory.
emitter electrode of a bipolar transistor. empirical design The design of electronic circuits
emitter degeneration In a transistor amplifier, by cut-and-try methods and, to some extent,

empirical design • end feed

through intuition arising from experience (i.e., encode 1. To convert signals or data into a desired
practical as opposed to theoretical design). (usually digital) form. Also called CODE. 2. To
empirical probability Probability estimated from equip a transmitter with a tone-producing device
experience and observations. This method is of- (encoder). 3. To develop and apply an encoding
ten used in quality-control and reliability proce- system to a group of transceivers or transmitters
dures. of a communications network.
empty medium A computer storage medium, such encoder 1. An analog-to-digital or digital-to-analog
as a magnetic tape or disk, that is ready to accept converter. 2. An electromechanical device for
data (i.e., rather than being completely blank, it translating the angular position of a rotating
contains the signals necessary for processing the shaft into a corresponding series of digital pulses.
to-be-added data). Also see SHAFT-ANGLE ENCODER. 3. A device
EMU, emu Abbreviation of ELECTROMAGNETIC for encoding data (see ENCODE). 4. A machine
UNIT(S). with a keyboard for printing characters that can
emulator In computer engineering, a sophisticated be read by optical character recognition (OCR)
device that substitutes for a similar device or equipment. 5. A tone generator used as a receiver
stage in the computer, and thereby provides a ba- enabler in the transmitters of a communications
sis for experimenting and troubleshooting without network.
disturbing the equivalent part of the computer. encoding 1. The translation, either by a machine
En Symbol for voltage remaining at null. or by a human operator, of a spoken or written
enable To initiate the operation of a circuit or de- language into digital code. 2. Any function per-
vice by applying a pulse or trigger signal. formed by an ENCODER.
enable pulse 1. A pulse that initiates the operation encryption The conversion of a signal from plain
of a circuit or device. 2. A binary pulse that aug- text, graphics, or other commonly recognizable
ments a write pulse to make a magnetic core form into a cipher. See also CIPHER. Compare
change state. DECRYPTION.
enabling gate A digital device that regulates the end-around carry In a computer, a carry produced
length of a pulse for specialized use. in the most significant position, causing a carry
enameled wire Wire that is insulated by a thin into the least-significant position.
coat of baked enamel. Commonly used in coil end-around shift In digital-computer operations,
winding because the thin enamel allows for a the transfer of characters from one end of a regis-
maximum number of turns in a given volume for ter to the other end. Also called LOGICAL SHIFT.
a given wire gauge. end bell 1. The part of a motor housing that sup-
encapsulant A material, such as potting resin, ports the bearing and protects internal rotating
used to embed (encapsulate) a component, cir- parts. 2. A clamping part fastened to the back of
cuit, or device. a plug or receptacle. 3. Either of the two frames of
encapsulated circuit A component, circuit, or de- a transformer that contains the mounting lugs.
vice embedded in plastic or wax (see ENCAPSU- end bracket See END BELL, 2.
LATION). end cell A cell intended for series operation in con-
encapsulated component An electronic part that junction with a storage battery. As the voltage of
is embedded in plastic or wax (see ENCAPSULA- the battery drops, the end cell can be added into
TION). the circuit.
encapsulating material See ENCAPSULANT. end effect 1. In a tapped coil, losses because of in-
encapsulation The embedding of a circuit or com- duced currents flowing in the inductance and
ponent in a solid mass of plastic or wax. The mold distributed capacitance of the unused end of the
or container remains as part of the assembly af- coil. 2. EDGE EFFECT in a capacitor. 3. An effec-
ter the plastic or wax has solidified. Protects tive capacitance at the ends of an antenna, re-
against the environment, and/or against the ef- sulting from air discharge. This lowers the
fects of physical vibration. Compare POTTING. resonant frequency slightly below that predicted
encephalogram See ELECTROENCEPHALO- by theory. The effect is exaggerated by the prox-
GRAM. imity of objects, such as trees and buildings, or
encephalograph See ELECTROENCEPHALO- when an antenna is placed close to the earth.
GRAPH. end effector The device or tool connected to the
enciphered facsimile Facsimile communications end of a robot arm (e.g., a gripper, screwdriver,
that have been rearranged or scrambled at the drill, or soldering iron).
transmitting location so that it cannot be inter- end-fed antenna An antenna whose lead-in or
cepted by a third party. A deciphering device is feeders are attached to an end of the radiator.
needed at the receiver end of the circuit. end feed A method of feeding electromagnetic
enclosure 1. A cabinet, case, or other housing for fields to an antenna by connecting the transmis-
electronic equipment, such as a receiver, trans- sion line to the end. Ordinarily, the antenna must
mitter, or test instrument. 2. A specially designed be a multiple of 0.5 wavelength long for end feed
housing for a loudspeaker. to be effective.
258 end-fire antenna • end point

end-fire antenna See END-FIRE ARRAY. endodyne reception See ZERO-BEAT RECEP-
end-fire array Also called end-fire antenna. A TION.
phased antenna in which the greatest radia- end-of-charge voltage For a rechargeable cell or
tion/response takes place off one or both ends. battery, the voltage at full charge (i.e., just after
The array consists of two or more parallel driven disconnection of the charging apparatus and be-
elements, all of which lie in a single plane. A typ- fore use).
ical system might consist of two half-wave end-of-data mark A code or character signaling
dipoles, fed 90 degrees out of phase and spaced that all the data in a computer storage medium
one-quarter wavelength apart in free space. This has been read or used.
produces a unidirectional directivity pattern. Two end-of-discharge voltage For a rechargeable cell
elements might be driven in phase and spaced or battery, the voltage at the termination of a dis-
1 wavelength apart, producing a bidirectional charging cycle, immediately before the unit is
pattern. These systems show some power gain, in taken out of use and the charging apparatus is
their favored directions, compared to a single connected.
half-wave dipole. The larger the number of ele- end-of-field mark In computer operations, a “flag”
ments, with optimum phasing and spacing, the code that signals when the end of a field has been
greater the gain. reached.
end-of-file mark In computer operations, a code
instruction that signals when the last record in a
file has been read.
end-of-line unit The last device or circuit in a
end-of-message character A character or code
signaling the end of a message.
end-of-run The end of a computer program or pro-
gram run, as indicated by the program.
end-of-tape mark A physical marker at the end of
a magnetic tape (e.g., something that can be
sensed by methods other than that used to read
the tape).
end-of-tape routine A computer program that
handles the processing needed after the last
record on a reel of magnetic tape has been
end-on armature A relay armature that moves in
the direction of the core™s axis.
end-on directional antenna See END-FIRE AN-
endoradiograph An X-ray picture, derived or en-
end-fire directivity In a directive antenna, beam- hanced by the introduction of substances into the
ing a signal along the plane of the antenna (i.e., body.
off its ends). endoradiosonde A tiny pill-enclosed transducer
end instrument A device capable of converting in- and radio transmitter for sensing physiological
telligence into electrical signals or vice versa, and conditions in the stomach and intestines; it
that needs to be connected to only one terminal of transmits corresponding signals to instruments
a loop. outside.
end item A final, completed product or component. endothermic reaction A chemical reaction pro-
endless loop Also called infinite loop. A computer ducing cold (i.e., one in which kinetic energy is
programming bug that causes the machine to go lost). Compare EXOTHERMIC REACTION.
in an indefinite, and often useless, logical circle. end-plate magnetron A magnetron whose oscilla-
For example, suppose that at line 180, the com- tion intensity is increased by a positive and a neg-
puter encounters the command GOTO 250, ative end plate, the electric field between them
meaning “Go to line 250,” but line 250 gives the causes the electrons to move axially while spin-
command GOTO 180. Once the computer gets to ning.
line 180, it enters a loop in which nothing is ac- end point 1. For a precision potentiometer, the
complished, and from which the only escape is shaft position between the last and first posi-
intervention by the operator (e.g., terminating the tions of measurement. 2. The point at which the
program). useful life of a device can be considered spent.
end mark In digital-computer operations, a signal 3. The point at which a time interval or opera-
or code indicating the close of an information tional sequence ends. 4. The end-point voltage
unit. of a primary or Edison storage cell. 5. For a
end point • energy-level diagram

energized The condition of a circuit or device that
Electron path
is powered or excited.
energy Symbol, W. Common units: joule, watt-
hour, and kilowatt-hour. 1. The capacity for do-
Magnet Magnet
ing work. Some common forms of energy are
electrical, mechanical, and chemical. Also see
Plate performed by electric power. The unit used by
Negative utility companies is the kilowatt-hour (kWh),
Electron path
electrode equal to the product Pt, where P is power in kilo-
watts and t is the period (hours) during which the
power is used.
Magnet energy-band diagram A diagram depicting the var-
ious energy levels within the atom of a conductor,
semiconductor, or insulator.
energy barrier The natural potential gradient
across a semiconductor junction. In the absence
of an applied voltage, the gradient, not measur-
able from the outside, prevents total interaction
end-plate magnetron
between the n- and p-type materials.
energy cell 1. A usually small primary or sec-
ondary cell”especially the kind used in hearing
lead-acid storage cell, the specific-gravity value
aids and electronic watches. 2. A capacitive-
of the electrolyte at which the cell is considered
type direct-current (dc) source (see ENERGY-
in need of recharging (nominally 1.150 to
energy consumption 1. The conversion of energy
end-point control A form of quality control in
from one form to another by a component, circuit,
which the end item is checked for defects.
system, or machine, in the process of performing
end-point sensitivity A means of expressing the
some useful task. 2. The amount of energy in-
sensitivity of a meter or other indicating device:
volved in the process defined in 1.
the ratio, in decibels, between the input signal
energy conversion The transformation of energy
required to produce a full-scale or maximum
from one form to another. See also CONSERVA-
reading and the smallest detectable input sig-
end-point voltage The voltage of a battery or cell
energy-conversion device A component, circuit,
terminal when the device is no longer useful.
system, or machine that changes energy from one
end resistance In a rheostat or potentiometer, the
form to another. See also CONSERVATION OF
resistance between the wiper and the end termi-
nal when the wiper is set to the end point of the
energy density 1. For an energy-producing cell,
such as an electrochemical cell, the ratio of avail-
end-resistance offset In a potentiometer, the re-
able energy to cell mass. It is expressed in joules
sistance between the wiper and an end terminal
per gram or in watt-hours per kilogram. 2. For
when they are in contact.
an energy-producing cell, the ratio of available
end-scale deflection See END-SCALE VALUE.
energy to cell volume. Expressed in joules per cu-
end-scale value For an indicating meter, the elec-
bic centimeter or in watt-hours per cubic cen-
trical quantity indicated at the last graduation on
the scale.
energy gap In the energy-level diagram for a semi-
end section Either the input or output section of a
conductor or insulator, the region between va-
multisection filter.
lence and conduction bands representing the
end setting 1. The fully clockwise or fully counter-
minimum energy required to make the electron
clockwise setting of a rotatable control. 2. The
pass from the valence to the conduction band
minimum or maximum setting of a control.
(i.e., to become a current carrier). Also called for-
end shield In a magnetron, a shield that confines
bidden energy band.
the space charge to the interaction space.
energy level A constant-energy state, such as one
end spaces The cavities at either end of the anode
of the energy levels of an electron in an atom.
block in a multicavity magnetron tube; they ter-
energy-level diagram 1. A diagram showing the
minate all the anode-block cavity resonators.
energy levels (in electronvolts) of electrons in the
end use The intended application of a circuit or de-
various shells of an atom. 2. A diagram showing
variations in power that correspond to variations
energize To apply operating power and input sig-
in current in a channel.
nals to a circuit or device.
260 energy loss • entladungsstrahlen

energy loss In any system, the energy that is un- power-supply filtering, and energy-cell service. Its
avoidably lost (i.e., it is not converted into useful active ingredients are compressed powders.
work). Also see ENTROPY and POWER LOSS. energy stored in capacitor The electrical energy
energy of a charge The energy level of an electro- in the field between the plates of a charged ca-
pacitor. In this instance, energy W = CE 2/2,
static charge. It is QV/2 ergs, where Q is the
quantity of electricity in coulombs, and V is the where W is the energy in joules, C is the capaci-
potential in volts. tance in farads, and E is the voltage in volts.
energy product An expression of the effectiveness energy stored in inductor The magnetic energy in
of a permanent magnet. The magnetic flux den- the field surrounding an inductor carrying cur-
rent. In this instance, energy W = LI 2/2, where W
sity is multiplied by the magnetic field strength to
obtain the energy product, specified in gauss- is the energy in joules, L is the inductance in hen-
oersteds. rys, and I is the current in amperes.
energy redistribution A mathematical process for energy transformation The conversion of one
determining the effective duration of an irregular form of energy into another, as with a transducer.
pulse. The instantaneous power output of the ir- engine analyzer An instrument for checking the
regular pulse is integrated from the start to the performance of an automobile engine. In addition
end of the pulse. Then, a rectangular pulse is to measuring voltage and resistance throughout a
constructed having the same peak power and the car™s electrical system, the instrument measures
same total energy content (area under the power engine speed, cam dwell angle, and other factors.
curve). The length of this rectangular pulse is engineer 1. A person who designs machines, cir-
considered to be the effective duration of the ir- cuits, and other devices. 2. A person who devel-
regular pulse. ops methods of utilizing machines, circuits, or
other devices more efficiently, or for new applica-
tions. 3. To design or implement an apparatus.
engineering The science of applying scientific laws
Equivalent rectangular
Max. to technical problems and designing practical de-
pulse (same start time)
vices. Also see ELECTRICAL ENGINEER and
enhanced-carrier demodulation A method of
reducing distortion in the demodulation of
amplitude-modulated (AM) signals. A properly
Instantaneous power

phased and synchronized local carrier is added to
the signal in the demodulator.
enhancement mode Operation characteristic of
enhancement-type MOSFET A metal-oxide semi-
conductor field-effect transistor (MOSFET) in
which the channel directly under the gate elec-
trode is widened (enhanced) by a negative gate
voltage in the n-channel unit or by a positive
gate voltage in the p-channel unit. Compare
0 ENIAC An electronic computer developed at the
Time University of Pennsylvania. The name is an
acronym for Electronic Numerical Integrator And
energy redistribution Calculator.
ENIC Abbreviation of voltage negative-impedance
energy state The condition of an electron, as ex- enrichment In a mixture of different isotopes of a
pressed by its position and velocity, with respect given element, the increase in the relative con-
to the position and velocity of other electrons. centration of one particular isotope.
energy-storage capacitor A usually high-value ca- ensemble 1. A collection of devices that functions
pacitor used primarily to store the charge used to together as a complete unit. 2. In music recording,
fire a lamp (as in a photoflash unit), create a the ability of all the musicians to hear each other
spark discharge (as in electronic ignition), or per- during the session. 3. A set of random mathemat-
form some similar function. ical functions, all starting at the same point.
energy-storage device 1. See CAPACITOR. 2. A ENSI Abbreviation of EQUIVALENT-NOISE-SIDE-
small, electrochemical component offering very BAND INPUT.
high capacitance (e.g., several farads) and low entladungsstrahlen Ultraviolet radiation emitted
leakage current (less than 1 pA). It has a number by electric arcs. At atmospheric pressure, the
of applications, including long-interval timing, wavelength is approximately 40 to 90 nanometers,
entladungsstrahlen • epitaxial deposition

depending on the arc length. The term is derived dust, light, moisture, noise, pressure, shock,
from the German word for discharge rays. temperature, and vibration.
entrainment Providing a path for gases to escape environmentally sealed Sealed against the effects
from an electrochemical cell or battery. of adverse environmental factors.
entrance delay In security applications, a delay environmental test chamber See CLIMATE
that allows authorized people time to leave the CHAMBER.
protected area after activating the alarm system, Eo 1. Symbol for OUTPUT VOLTAGE. 2. Symbol for
or to deactivate the system after entering the pro- zero reference voltage.
tected area. The delay is approximately 30 to 45 EOF Abbreviation of end of file.
seconds. EOL Abbreviation of end of line.
entropy 1. In all closed physical systems, the mea- EOLM Abbreviation of electro-optical light modula-
sure of energy wasted. According to the second tor.
law of thermodynamics, for example, supplied EOR Abbreviation of END OF (program) RUN.
heat can never be converted entirely into work. EOS Abbreviation of electro-optical system(s).
2. In communications, the amount of information EOT Abbreviation of end of tape.
in a message, defined as the base-10 logarithm of EOTS Abbreviation of electro-optical tracking sys-
the number of equivalent messages that can ex- tem.
ist. 3. A natural process in which the energy in EP 1. Symbol for PLATE VOLTAGE. 2. Symbol for
the universe tends to become more uniformly dis- PEAK VOLTAGE.
tributed with the passage of time. EP Abbreviation for EXTENDED PLAY.
entropy coding A form of digital encoding that ephemeris time Time measured with respect to
minimizes redundancy, thereby increasing the the orbit of the earth around the sun. Initiated in
amount of data in a given amount of memory or the year 1900 AD.
storage space. epipolar navigation A scheme for position sensing
entry 1. A unit of computer input or output infor- and navigation that uses an artificially intelligent
mation. 2. A data item in a table or list. 3. A com- vision system. Allows calculation of position and
puter source program statement. 4. In a computer velocity, based on changes in the visualized di-
program, the address of the first instruction. rection, size, and shape of an object whose actual
entry condition A condition that must be specified location, size, and shape are precisely known. It
before a computer program is run (e.g., establish- is used in some mobile robots.
ing operand values). episcotister A mechanical light beam modulator.
entry-level system 1. The least-sophisticated The device consists of a series of rotating disks
computer that will perform the things that a user having transparent and opaque sections that al-
requires. 2. A simple electronic or computer sys- ternately interrupt and pass the light beam at an
tem (e.g., an amateur radio transciever or per- audio-frequency rate.
sonal computer, intended for ease of operation,
and from which the user expects to upgrade to a
more powerful system at a later date).
entry point In a computer program, the first in-
struction to be implemented, or a point during
the run when data can be entered.
envelope 1. On a graph, the imaginary line joining
successive signal peaks. In the graph for an am-
Stationary disk
plitude-modulated signal, the line reproduces the
modulating wave. 2. The enclosure of a transistor
or integrated circuit. 3. The glass shell of a vac- Rotating
uum tube. disk
envelope delay In a tuned amplifier, time delay in-
troduced in the envelope of a modulated signal by
varying the phase of the envelope with the modu-
lating frequency. This delay varies directly with Modulated
the amount by which the sidebands shift, with re- light
spect to the carrier frequency.
enveloped file A computer file with labels permit- episcotister
ting it to be handled by a computer of a type dif-
ferent from that used to make the file.
epitaxial Pertaining to, or having the property of,
environmental conditions See ENVIRONMENTAL
epitaxial deposition The tendency of certain ma-
environmental factors Aspects of the space im-
terials to grow on a semiconductor substrate un-
mediately surrounding and sometimes influenc-
der certain conditions.
ing electronic equipment. Examples: altitude,
262 epitaxial device • equation solver

epitaxial device A semiconductor device built by equalization 1. The use of an EQUALIZER to make
means of EPITAXIAL GROWTH. the frequency response of a line, amplifier, or other
epitaxial film A film of single-crystal semiconduc- device uniform over a given frequency range.
tor material deposited onto a single-crystal semi- 2. The use of an EQUALIZER to modify the fre-
conductor substrate. quency response of a line, amplifier, or other device.
epitaxial growth Growing monocrystalline silicon equalizer A circuit or device, such as a compen-
on a silicon wafer by precipitating silicon from a sated attenuator, that allows the user to tailor the
gas in which the wafer is placed. Epitaxy is se- frequency response of a line, amplifier, or other
cured between the precipitate and the wafer. device. Sometimes used in sophisticated high-fi-
epitaxial layer A semiconductor layer exhibiting delity stereo amplifier systems, to obtain a de-
epitaxy. Also see EPITAXIAL GROWTH. sired bass/midrange/treble frequency output.
epitaxial mesa transistor See DOUBLE- equalizer circuit breaker A form of circuit breaker
DIFFUSED EPITAXIAL MESA TRANSISTOR. that trips in the event of unbalance in an electri-
epitaxial planar transistor A planar transistor cal system.
having an epitaxially grown collector on a low- equalizing current A current that flows in the cir-
resistivity substrate, and a diffused base and cuit of two compound generators connected in
emitter. parallel.
epitaxial process See EPITAXIAL GROWTH PRO- equalizing network A circuit used to equalize a
CESS. line.
epitaxial transistor A transistor in which an epi- equalizing pulses In a television signal waveform,
taxial layer (into which a base region later is dif- several pulses (preceding and following the vertical
fused and an emitter region alloyed) is grown on sync pulse and having a repetition rate of twice the
the face of a semiconductor wafer, which serves power-line frequency) that start the vertical re-
as the collector. Also see DOUBLE-DIFFUSED trace at the correct instant for good interlace.
epitaxy The condition in which atoms in a thin equal vectors Vectors having the same magnitude
film of single-crystal semiconductor material and the same direction. They do not necessarily
grown on the surface of the same kind of wafer originate at the same point. Compare IDENTICAL
continue their characteristic alignment. Also see VECTORS.
E plane The plane of an antenna containing the
electric field. X
E plane bend See E BEND.
E-plane tee junction A waveguide junction whose
structure changes in the plane of the electric
epoxy resin A synthetic resin used to encapsulate
electronic equipment, or as a cement. Epoxy
resins are based on ethylene oxide or its deriva-
EPROM Abbreviation of erasable programmable
read-only memory.
EPU 1. Abbreviation of electronic power unit. 2. Ab-
breviation of emergency power unit. Z
Eq 1. Abbreviation of equation. 2. Abbreviation of
equal alternations Positive and negative half-
cycles of a wave that have identical shape and
X = Y = Z
equal-energy source A light source that has a con-
stant emission rate (energy per unit wavelength).
equal-energy white The color of light emitted by a
source radiating equally the wavelengths of the
visible-light spectrum.
equal heterodyne In a beat-frequency system, the
equal vectors
condition in which the outputs of the two hetero-
dyning oscillators are identical.
equality circuit A logic circuit that, when two
equation solver A (usually analog) computer for
numbers are put into it, outputs logic 1 if the
solving linear simultaneous equations or for de-
numbers are equal, and logic 0 if the numbers are
termining the roots of polynomials.
not equal.
equatorial orbit • equivalent inductance

equatorial orbit A satellite orbit that lies in the action as the capacitance distributed throughout
plane of the earth™s equator. a circuit.
equiphase surface Any surface in a wave, over equivalent circuit A circuit that has the same
which the field vectors at a particular instant overall current, impedance, phase, and voltage
have either 0° or 180° phase difference. relationships as a more-complicated counterpart
equiphase zone The space region in which two ra- that it usually replaces for analysis.
dionavigation signals show no phase difference. equivalent component density For a circuit in
equipment 1. Collectively, apparatus or compo- which discrete components are not used or are
nents designated for a specific purpose (e.g., ra- not evident, the volume of that circuit divided by
dio equipment). 2. A functional electronic unit, the number of discrete components that would be
such as a test instrument, receiver, or memory required if the circuit used them.
unit. equivalent conductivity The conductivity of a so-
equipment chain A system consisting of series- lution that contains 1 gram equivalent of the so-
connected circuits or devices. lute in the space between electrodes 1 centimeter
equipment ground An electrical ground connec- apart.
tion intended to reduce the chances of electric equivalent dark-input current For a photoelectric
shock. An equipment ground does not necessar- device, the illumination required for an output
ily constitute a good radio-frequency ground; it current equal to the DARK CURRENT of the de-
serves only to eliminate potential differences vice.
among the individual units in a system. equivalent decrement The value of decrement in
equipment life The period during which electronic a damped wave that would result in the same
equipment functions according to specifications; amount of interference at a receiver as the inter-
it is terminated at an END POINT. ference caused by the sidebands of an amplitude-
equipment test A usually preliminary, qualifying modulated signal.
test of electronic equipment. equivalent delay line A comparatively simple net-
equipotential Having a potential difference of zero; work, such as a resistance-capacitance (RC) cir-
being at the same voltage level. cuit, that will provide the attenuation and phase
equipotential line Between two charged plates, characteristics of an ideal delay line.
the locus (an imaginary line) of points having the equivalent delta In a three-phase system, a delta-
same potential, with respect to the plates. connected circuit that is equivalent to a given
equipotential surface A surface on which all wye-connected circuit, from the standpoint of
points have the same electrical potential. impedance and phase. Also see DELTA CONNEC-
equisignal Pertaining to signals having equal in- TION and WYE CONNECTION. Compare EQUIV-
equisignal localizer See TONE LOCALIZER. equivalent differential input capacitance For a
equisignal radio-range beacon For aircraft guid- differential amplifier, the equivalent input capac-
ance, a radio-range beacon that transmits two itance (see EQUIVALENT CAPACITANCE) at one
distinct signals that are received by aircraft with input (inverting or noninverting) when the oppo-
equal intensity only in certain directions. site input is grounded.
equisignal surface The “surface” around a trans- equivalent differential input impedance For a
mitting antenna formed by points of equal field differential amplifier, the equivalent input
intensity. impedance at one input (inverting or noninvert-
equisignal zone The region in which two radionav- ing) when the other input is grounded.
igation signals have identical amplitude. equivalent differential input resistance For a
equivalence The condition existing when one net- differential amplifier, the equivalent input resis-
work can be substituted for another without dis- tance at one input (inverting or noninverting)
turbing currents, impedances, and voltages at when the other input is grounded.
the terminals. equivalent equations Two equations for an un-
equivalent absorbing power See EQUIVALENT known that have the same root.
STOPPING POWER. equivalent four-wire system A two-wire line over
equivalent absorption Unit, sabin. The rate at which full-duplex operation is obtained by use of
which a surface absorbs sound energy. frequency division.
equivalent binary digits For a given decimal num- equivalent height See VIRTUAL HEIGHT.
ber or specific character, the corresponding bi- equivalent impedance 1. The value of a single
nary digits (bits). lumped impedance that would cause the same
equivalent bit rate The number of binary digits action as the impedance distributed throughout a
(bits) that can be sent in a given unit of time, circuit. 2. An impedance that draws current of
such as one second, in a digital communications the same strength and phase as that drawn by an
system. impedance it replaces.
equivalent capacitance The value of a single equivalent inductance The value of a single
lumped capacitance, that would cause the same lumped inductance that would cause the same
264 equivalent inductance • equivalent wye

action as the inductance distributed throughout equivalent-noise-sideband input Abbreviation,
a circuit. ENSI. A specification for receiver noise character-
istics. Numerically, ENSI = 0.3Es(Pn/Ps) „2, where
equivalent input offset current For a differential
amplifier, the difference between currents flowing Es is the voltage of an unmodulated radio-
into the inverting and noninverting inputs when frequency (RF) carrier applied to the receiver, Pn
the output voltage is zero. is the resulting noise-output power of the receiver
equivalent input offset voltage For a differential (measured with an rms meter), and Ps is the
amplifier, the input voltage required to reduce the noise-output power measured with the RF signal
output voltage to zero. 30% amplitude modulated at 400 Hz with a 400-
equivalent input wideband noise voltage For a Hz bandpass filter inserted between the receiver
differential amplifier, the ratio Vo/Gv, where Vo is output terminals and the meter.
the root-mean-square (rms) output-noise voltage, equivalent noise temperature For a component
and Gv is the direct-current (dc) voltage gain. having resistance, the temperature (degrees ab-
equivalent length of antenna 1. The electrical solute) at which a theoretically perfect resistor
length of an antenna, as measured in degrees or having the resistance of the component would
wavelengths. 2. The free-space length of an an- generate the same noise the component gener-
tenna. 3. The length d (in feet) of a quarter-wave ates at room temperature.
resonant antenna at a specific frequency f (in equivalent optics The analogy between certain op-
megahertz), given by the formula d = 234/f. 4. tical lenses and prisms and the electrostatic de-
The length d (in feet) of a half-wave resonant an- flection of an electron beam. Thus, when the
tenna at a specific frequency f (in megahertz), upper deflecting plate in an electrostatic deflec-
given by the formula d = 468/f. tion system is made negative and the lower plate
equivalent length of electric dipole The distance, is positive, the beam is deflected downward, like
measured in a straight line, separating the points horizontal light rays bent by a prism. When both
that represent the charge centers of an electric plates are made equally negative, the beam con-
dipole. verges to a point, as light rays do when they pass
equivalent length of feed line The electrical through a double convex lens. When both plates
length of a feed line as measured in degrees or are made equally positive, the beam spreads out,
wavelengths. Generally, this is equal to 1/v times as do light rays passing through a double con-
the line length in free-space wavelengths, where v cave lens.
is the VELOCITY FACTOR of the line, expressed equivalent permeability The permeability of a
as a fraction between 0 and 1. component made of certain materials, compared
equivalent length of magnet The distance sepa- with that of a component having the same reluc-
rating the poles of a magnet. In a bar magnet, tance, shape, and size, but made of different ma-
these poles are not exactly at the ends. The actual terials.
equivalent length is about 83% of the length of equivalent reactance The value of a single lumped
the bar magnet. reactance that would cause the same action as
the reactance distributed throughout a circuit.
equivalent resistance The value of a single lumped
resistance that would cause the same action as
N the resistance distributed throughout a circuit.
equivalent series and parallel circuits Series and
parallel circuits in which current, voltage, phase,
Equivalent and frequency relationships are identical. Any se-
Flux Flux length ries circuit can be transformed into an equivalent
parallel circuit.
equivalent series resistance The equivalent resis-
S tance acting in series with circuit components.
equivalent sine wave A sine wave of the same fre-
equivalent length of magnet quency and effective voltage as a given wave.
equivalent stopping power For a material in the
path of radioactive particles, the thickness of the
equivalent loudness The actual intensity, in deci- material that produces the same energy loss as
bels, of a given sound whose apparent loudness that produced by one centimeter of air.
changes with frequency. equivalent time The effective duration of some
equivalent network A network that can replace a phenomenon, such as a pulse.
more-complex network for analysis purposes. equivalent volt See ELECTRONVOLT.
equivalent noise input The value of modulated lu- equivalent wye In a three-phase system, a wye-
minous flux that, when applied to a photoelectric connected circuit that is equivalent to a given
device, produces a root-mean-square (rms) output delta-connected circuit from a standpoint of
current equal to the device™s rms noise current. impedance and phase. Also see DELTA
equivalent wye • error correction

CONNECTION, EQUIVALENT DELTA, WYE CON- erase oscillator In a tape recorder, a high-
NECTION, and WYE-EQUIVALENT CIRCUIT. frequency (typically 30 to 80 kHz) oscillator that
equivalent Y See EQUIVALENT WYE. supplies erase current.
equivocation A condition in which the meaning of eraser See BULK ERASER.
data depends on certain parameters. erase signal A signal that causes recorded material
ER Abbreviation of ECHO RANGING. to be erased (see ERASE and ERASE CURRENT).
Er Symbol for ERBIUM. erasing speed The rate at which successive stor-
Er Symbol for voltage drop across a resistance. age elements are erased, as in a charge-storage
erasable storage In computer operations, any tube.
storage medium holding information that can be erasure 1. In tape-recording and digital-computer
erased. operations, the process of erasing a recorded sig-
erasable PROM A programmable read-only mem- nal (see ERASE). 2. An erasure accomplished by
ory (PROM) from which the data can be removed, the process described in 1, above.
usually by exposure to ultraviolet light. Also see erbium Symbol, Er. A metallic element of the rare-
PROM. earth group. Atomic number, 68. Atomic weight,
erase To obliterate or remove a signal, especially a 167.26.
recorded one, as in the erasure of recorded mate- E region See E LAYER.
rial from a magnetic tape or the data from a com- e register In a computer, a register used in double-
puter disk. precision calculations.
erase button A pushbutton that actuates the cir- Er-Ey signal In color television, the resultant signal
cuit supplying a signal that erases stored mate- that is the difference between the original full-red
rial (as the display on a storage oscilloscope). and Ey signals.
erase current In an electromagnetic erase head, ERG Abbreviation of ELECTRORETINOGRAPHY.
the current flowing through the coil of the head. erg Abbreviation, e. A unit of work. It is the work
done by a force of one dyne (10“5 newton) acting
In most instances, it is a high-frequency current
(usually the regular bias current), but it can be as through a distance of one centimeter.
low as 60 Hz, as long as the speaker does not re- ergograph An instrument used to measure and
spond to what remains of it on the tape after era- record work done by muscles.
sure. ergometer An instrument for measuring energy
erase head In a tape recorder, a head used to erase consumed or work accomplished.
recorded material from tape. It can contain a per- ergon See ERG.
manent magnet (see ERASE MAGNET) or an elec- Erms Symbol for ROOT-MEAN-SQUARE VOLTAGE.
tromagnet whose coil carries erase current. ERP Abbreviation of EFFECTIVE RADIATED
error 1. In calculations and measurements, the
Magnetic difference between a true value and an observed
Tape movement
tape or calculated value. 2. In electronic circuits, es-
pecially those of automatic control systems, the
difference between a required (or reference signal)
level and the actual signal level. 3. In communi-
cations, a discrepancy between the transmitted
data and the received data.
error accumulation The adding-up of maximum
possible error when measurements are repeat-
edly made. Generally, the maximum plus-or-
minus error per measurement is multiplied by
the number of measurements.
head error amplifier An amplifier for boosting error cur-
rent or voltage.
error-checking code An error-correcting or error-
detecting code.
error-correcting code An error-detecting code
that, in addition to the function indicated by its
name, indicates the correct code.
erase head
error-correcting telegraph A digital communica-
tions system in which an improbable or incorrect
erase magnet In a tape recorder, a magnet used to character is not accepted. In the event that such
erase recorded material from tape. Because the a character is received, the receiver instructs the
strength of the magnet is greater than that of the transmitter to send that character again.
magnetized areas on the tape, erasure is com- error correction 1. The restoration of mutilated,
plete (the tape left demagnetized). corrupted, or missing data in a digital system,
266 error correction • ET

especially in magnetic data storage media, such as appropriate action is taken (correct the error, re-
tapes and disks. 2. In digital communications, any peat the process, etc.).
scheme in which the receiver (destination) auto- error-sensing circuit A circuit that samples the
matically eliminates (to the greatest possible ex- output current or voltage of a power supply, am-
tent) errors in data from a transmitter (source). For plifier, or control system, compares this output
example, the destination can instruct the source with a standard value, and delivers a feedback
to repeat questionable characters or words. (correction) signal whose amplitude is propor-
error-correction routine In computer operations, tional to the difference (error).
a series of programmed instructions to detect and error signal In a servo system, an output signal
correct errors in files. A common example is a whose value is proportional to the difference be-
spell-checking program for word-processed docu- tween the actual operating quantity of the system
ment files. and a standard reference quantity. The signal is
error current An error signal that is a feedback fed back to the input of the system for automatic
current for automatically correcting a system. correction.
error curve A bell-shaped curve that describes the error tape In data processing, a record tape de-
distribution of errors in measurement around a signed and used for storing errors for subsequent
true value. study.
error-detecting code In computer operations, a error voltage An error signal that is a feedback

character-coding system that ensures that an im- voltage for automatically correcting a system.
possible combination (forbidden characters) will Es Symbol for EINSTEINIUM.

be generated by an error (for error detection). Esaki diode See TUNNEL DIODE.
error-detecting routine A computer program that E scope See E DISPLAY.
detects errors by checking the validity of data. escape character In computer operations, a char-
error detection and feedback In computer opera- acter indicating that the next character belongs
tions, a system in which an error (sensed by an in a new group.
error-detecting code) automatically generates a escapement A (usually oscillating) mechanical or
request to repeat the suspect signal. electromechanical device that stores energy (often
error detector A sensor that responds to an error in a spiral spring) on one swing, and returns that
signal by delivering a signal proportional to the energy on the next swing. Such a mechanism ad-

error. vances a shaft progressively in a clock or watch,
error diagnostics As performed by a compiler, de- and in some control equipment.
tecting and indicating the presence of errors in escape velocity 1. The minimum velocity (about
source language statements. 25,000 miles per hour or seven miles per second)
error interrupt A computer program halt caused required for a space vehicle to completely escape
by a software or hardware error and accompanied the gravitational field of the earth. 2. The mini-
by a display of what has happened. mum velocity required for a space vehicle to com-
error list As produced by a compiler, a list of pletely escape the gravitational field of a planet or
source language statement faults. star. 3. The minimum velocity required for an
error message During a computer program run, a electron to escape the electrical influence of an
statement (displayed on a peripheral) of what is atomic nucleus.
in error. escutcheon A usually decorative plate that
error of measurement The positive or negative dif- frames an opening or covers a panel in a piece of
ference between the value of an actual measure- equipment (e.g., the escutcheon of a radio tun-
ment and the true (or most probable) value. ing dial).
error range For a data item, the range of values ESD Abbreviation of ENERGY-STORAGE DEVICE.
over which it will cause an error. ESG Abbreviation of electronic sweep generator.
error rate In data transmission, the ratio of errors Esnault-Pelterie formula A formula for approxi-
transmitted to the data transmitted. mately calculating the inductance of a single-
error-rate damping Damping that involves adding layer solenoidal coil:
to an error signal another signal that is propor-
L = 0.1008(a2n2)/(s + 0.92a)
tional in rate of change.
error ratio 1. In a received message, the number of where L is the coil inductance in microhenrys, a
incorrect characters divided by the total number is the radius of the coil in inches, s is the length
of characters. Can be represented as a fraction of the coil in inches, and n is the number of turns
between 0 and 1 or as a percentage by multiply- in the winding. The formula is accurate to 0.1
ing the fraction by 100. 2. A measure of distortion percent for all values of 2a/s between 0.2 and
for digital signal communications. The number of 1.5.
inaccurately received bits divided by the total ESS Abbreviation of electronic switching system.
number of received bits. EST Abbreviation of EASTERN STANDARD TIME.
error routine A computer program segment that is esu Abbreviation of ELECTROSTATIC UNIT(S).
input when an error is detected so that an ET Abbreviation of EPHEMERIS TIME.

ETC • even-line field

ETC Abbreviation of electronic temperature control. Ettinghausen effect A phenomenon somewhat
etchant Any substance such as cupric chloride, like the HALL EFFECT. It occurs when a metal
ferrous chloride, or hydrochloric acid, used in strip, carrying current longitudinally, is placed
etching. into a magnetic field perpendicular to the plane of
etched circuit A circuit produced by etching the the strip: corresponding points on opposite edges
metallic coating of a substrate to provide the re- of the strip exhibit different temperatures.
quired pattern of conductors and terminals to Eu Symbol for EUROPIUM.
which discrete components are soldered. eudiometer 1. An instrument for measuring the
amount of oxygen in the air. 2. An instrument for
analyzing gases.
eureka 1. See CONSTANTAN. 2. The ground
transponder beacon in the British rebecca-
eureka radar navigational system (see REBECCA-
europium Symbol, Eu. An element of the rare-
earth group. Atomic number, 63. Atomic weight,
eutectic 1. A form of reaction in which mixed liq-
uids solidify when cooled. 2. The solid substance
resulting from a reaction as defined in 1.
eutectic alloy A metallic alloy with a specific melt-
ing point, made via eutectic process.
eutectic bond A connection between two dissimi-
lar metals, facilitated by a third metal alloyed, via
etched circuit
eutectic process, to the adjoining faces.
evacuation The removal of air or other gases from
etch factor The ratio of the depth to the width of
a tube or chamber, specifically, the envelope of a
an etched track in an etched circuit.
vacuum tube that houses the internal elements.
etching 1. Chemically eating away a metal to form
evaporation 1. A technique for electrically deposit-
a desired pattern, such as an etched circuit. 2.
ing a film of a selected metal on a metallic or non-
Thinning a quartz-crystal plate by slowly eroding
metallic surface. A filament of the metal to be
one or both of its faces with hydrofluoric acid to
deposited is heated by an electric current in a
fine-tune the resonant frequency.
vacuum chamber, which makes filament parti-
ET-cut crystal A piezoelectric plate cut from a
cles travel to the (nearby) object to be coated,
quartz crystal at an angle of +66°, with respect to
where they condense as a film. In an alternate
the z-axis. Also see CRYSTAL AXES and CRYS-
method, a piece of the metal to be deposited is
laid on or wrapped around a filament of some
ether 1. Also called luminiferous ether. A nonvis-
other metal. 2. Electron emission by a hot cath-
cous fluid once thought to fill space, convey
waves (radio, light, etc.), and sustain fields. 2. A
evaporation theory The theory that electrons will
volatile liquid occasionally used in electronics as
acquire sufficient escape velocity to leave a mate-
a solvent [e.g., ethyl oxide (C2H5)2O].
rial when the energy acquired by (or imparted to)
ether drift The postulated motion between a mate-
the electron exceeds the work function of the ma-
rial body and the ether (see ETHER, 1). The con-
terial. Also see WORK FUNCTION.
cept was checked by Michelson and Morley, who
E vector The vector that represents the electric
failed to find that the earth moves relative to the
component of an electromagnetic wave.
ether. This eventually led to scientific rejection of
even-even nucleus An atomic nucleus containing
the so-called ether theory of the propagation of
an even number of protons and an even number
of neutrons. An example is the alpha particle, or
ethical slave A machine, especially a smart robot,
helium nucleus, which contains two protons and
that is treated in the manner of a slave, based on
two neutrons.
the notion that a machine cannot have “feelings.”
even harmonic In a complex waveform, an even-
Some researchers fear that the use of ethical
numbered multiple of the fundamental fre-
slaves could lead to technological nightmares. For
quency. Compare ODD HARMONIC.
example, robots might be used as soldiers in a ma-
even line In a television picture, an even-
rauding offensive army; the commanders could ra-
numbered member of the 262.5 horizontal lines
tionalize that there is nothing immoral about the
scanned by the spot in developing the even-line
war because there is no loss of life on their side.
field. Compare ODD LINE.
E transformer A differential transformer whose
even-line field On a television screen, the com-
primary is wound on the center leg of an E core,
plete field obtained when the spot has traced all
the secondaries being wound on the outer legs.
268 even-line field • excited state

the even-numbered lines. Compare ODD-LINE is 1010 in the code (it is 0111 in binary). Unlike
FIELD. the binary representation for zero, the excess-
even parity check A check to verify the presence of three representation (0011) contains two ones, a
an even number of ones or zeros in a group of bits. feature that distinguishes actual zero from a ma-
event An occurrence that affects the state of a chine fault.
computer file. exchange 1. To reverse the contents of two mem-
event counter Any device that measures the num- ory banks. For example, if the memory banks are
ber of specified events taking place within a cer- called A and B, an exchange is the placing of the
tain interval of time. contents of memory A into memory B, and the
evolution Extracting a root of a number (e.g., placing of the contents of memory B into memory
square root, cube root, etc.). A. The original contents are removed. 2. A two-
E wave In microwave operations, the transverse way sequence of data transmissions. 3. A desig-
magnetic (TM) wave. Also see WAVEGUIDE nated location in a telephone circuit.
MODES. exchange line A telephone line.
EWR Abbreviation of EARLY-WARNING RADAR. exciplex In a laser, a method of adjusting the color
EWS Abbreviation of early-warning system. by means of chemical reactions in organic dyes.
EX 1. Symbol for voltage drop across a reactance. excitant The electrolyte in a voltaic cell.
2. Symbol for EXCITATION ENERGY. excitation 1. Supplying input-signal driving cur-
exa- Symbol, E. A prefix meaning 1018 (Interna- rent, driving power, or driving voltage. 2. Input-
tional System of Units). signal driving current, driving power, or driving
exalted-carrier reception In radio reception, over- voltage.
coming the effects of selective fading by maintain- excitation anode In a mercury-pool tube, an aux-
ing the carrier at a high amplitude. This is iliary anode whose operation maintains the cath-
accomplished before demodulation by removing ode spot when no output current is being drawn
the carrier from an amplitude-modulated or phase- from the tube.
modulated signal, amplifying it, and reinserting it excitation current 1. Input-electrode current in
at a higher amplitude with the sidebands. an excited transistor amplifier. 2. Grid current in
exc 1. Abbreviation of EXCITER. 2. Abbreviation of an excited vacuum-tube amplifier. 3. Current
EXCITATION. flowing in the circuit of the excitation anode of a
except gate A logic gate that delivers an output mercury-pool tube. 4. Current flowing in the ex-
pulse when an input pulse is present at one or citer circuit of an alternator. 5. Shunt-field cur-
more of a set of input terminals, and absent from rent in a motor.
one or more of another set of input terminals. excitation energy 1. Symbol, EX. In artificial
Also called exclusive-OR element. transmutation, the energy of a nucleus when pro-
excess charge The amount of overcharge for a tons of less than maximum energy have been
storage battery. emitted from the atom. 2. Electrical energy re-
excess conduction In a semiconductor, current quired by a transducer.
conduction by excess electrons. excitation purity In color television, complete sat-
excess electron 1. An electron that, when intro- uration of a hue (i.e., there is no contamination
duced into an atom, results in a negative ion. 2. by other colors, and the saturated hue is dis-
An electron resulting from the addition of a donor tributed uniformly).
impurity to a semiconductor substance. excitation voltage 1. The signal voltage that
excess meter A meter that integrates the amount achieves, or is required for, excitation (see EXCI-
of power in excess of some predetermined level. TATION, 1). 2. The value of driving voltage.
excess minority carriers The number of minority excitator An electrical discharger.
carriers in excess of the normal equilibrium num- excited atom An atom in which one or more
ber in a semiconductor material. electrons have been pushed out of their normal
excess modified index of refraction Symbol, M. orbits into higher ones by energy applied from the
For waves transmitted through a refracting outside.
medium, a modified index of refraction greater excited-field speaker A dynamic speaker in which
than unity. the magnetic field is provided, not by a perma-
excess noise Electrical noise caused by current in nent magnet, but by direct current flowing
a semiconductor material. through a large coil of wire wound around the
excess sound pressure Unit, dyne/cm2. In a speaker core. The coil usually acts as a filter
medium conducting sound waves, the quantity choke in the power supply of the attendant am-
Pi “ Ps, where Pi is total instantaneous pressure at plifier or receiver.
a given point in the medium, and Ps is static pres- excited state In artificial transmutation, the state
sure in the absence of the sound waves. of the nucleus when protons of less-than-maxi-
excess-three code A computer code derived from mum energy have been emitted from the atom.
binary notation by adding binary three (i.e., The energy of the protons, in this instance, is
0011) to each four-bit group. Thus, decimal seven greater than the ground state.
exciter • expandable

exciter 1. An amplifier or oscillator (or a system of A
such units) that supplies the input (driving) sig- C
nal to the output amplifier in a radio transmitter B
or similar device. 2. A small direct-current (dc)
generator that supplies direct current to the field
winding of an alternating-current (ac) generator. A B C
exciter lamp 1. A concentrated-filament, high- 0 0 0
intensity incandescent lamp used in sound- 0 1 1
on-film recording and reproduction and in some
1 0 1
types of electromechanical television. 2. In a
facsimile transmitter, the lamp illuminating what 1 1 0
is being scanned.
exciter relay In an electromechanical generator,
the relay that activates the direct-current (dc)
field excitation during machine startup.
exciter response 1. A change in the exciter voltage
of a motor when the field-circuit resistance
changes. 2. A change in the operating conditions Also called monitor program. Compare MONITOR
of a radio frequency exciter, as a result of a SYSTEM.
change in the impedance at the input of the final exhaust analyzer An instrument for examining
amplifier. the exhaust fumes of an internal combustion en-
exciter unit See EXCITER. gine, to measure the presence of noxious ma-
exciting current 1. The output current produced terials and to evaluate air-to-fuel ratio and
by the exciter of a generator (see EXCITER, 2). 2. combustion efficiency.
The field current of a dynamo-type generator. 3. exhaustion See EVACUATION.
Primary current in an unloaded transformer. exit 1. In computer operations, the last instruction
exciting power 1. The output power produced by in a program or program segment, often taking a
an exciter. 2. The input-signal power required for subroutine back to the main program. 2. To leave
full output from a power amplifier. Also called a computer application, routine or subroutine.
DRIVING POWER. exoskeleton A robot that resembles a suit of ar-
exciting voltage 1. Input-signal voltage. 2. The mor, and that greatly magnifies the force of phys-
input-signal-voltage amplitude required for full ical movements. A human operator occupies the
rated output from a power amplifier. Also called interior. Thus, for example, the operator might
DRIVING VOLTAGE. 3. The output voltage pro- use the machine to throw a football 2500 yards,
duced by an exciter. or to run 50 miles an hour, or to smash through
exciton In a semiconductor or dielectric, a bound walls. Primarily a tool of science fiction writers,
electron-hole pair. this machine is within the scope of current
excitron A mercury-pool rectifier whose arc is robotic technology.
initiated mechanically (e.g., by means of a exosphere The extreme outer layer of the earth™s
magnetic plunger in the tube). atmosphere.
exclusion principle The rule that only one particle exothermic Pertaining to a chemical or electro-
of a particular kind can occupy a given quantum chemical reaction in which heat is given off. Com-
state at one time. pare ENDOTHERMIC.
exclusive-NOR A logic function where the output exothermic reaction In a chemical reaction, the
is 1 if both inputs are 1 or both are 0 (same). The production of positive reaction energy (i.e., ki-
output is 0 if one input is 0 and the other is 1 (dif- netic energy is gained). Compare ENDOTHERMIC
ferent). Compare EXCLUSIVE OR. REACTION.
exclusive-OR A logic function in which the output exp 1. Symbol for EXPONENTIAL. 2. Abbreviation
is 1 when the two inputs are different, and is 0 of EXPERIMENT(AL).
when the two inputs are the same. expand 1. In communications, to increase the
excursion 1. A change in the value of a quantity in bandwidth of a signal, restoring it to normal
a given direction. 2. In an oscillatory system, a bandwidth after it has been compressed. 2. In
body™s moving away from the point of equilibrium communications, to increase the dynamic range
or mean position. of a signal. 3. In computer operations, to restore
execution A computer™s performance of the opera- a file to full or normal size after it has been com-
tions required by an instruction. pressed. 4. To widen the scale of a meter. 5. To
execution time The length of time required for a widen (or magnify a portion of) the trace of an os-
computer to complete a designated operation. cilloscope beam. Compare COMPRESS.
executive routine In computer operations, a pro- expandable Capable of being built up into larger
gram that controls and processes other routines. circuits or systems.
270 expandable gate • exponential horn

experiment One or a series of carefully planned
expandable gate In digital logic, a gate that can be
tests carried out under controlled conditions to
provided with an unlimited number of input lines
obtain data or to check performance.
by electrical interconnection with other gates.
experimental chassis See ELECTRONIC CHASSIS.
expanded memory In personal computer systems,
experimental model A prototype of an electronic
memory beyond the basic 640 kilobytes (640 kb),
circuit or device, produced solely for operational
up to one megabyte (1 MB). This memory resides
tests or as a model against which theory and de-
in integrated circuits (ICs) in the computer, and is
sign can be checked.
normally volatile (i.e., it is not retained when
experimental service A special, nonamateur radio
power is removed). Compare EXTENDED MEM-
service intended for on-the-air testing of new
methods and equipment.
expanded-scale meter A meter having a scale de-
experimental station A station specially licensed
signed to display a narrow range of values. Such
to operate on specific frequencies in the experi-
a meter used for monitoring the 117-V power line
mental service.
might have a scale reading 100 to 140 V, instead
expert system Also called rule-based system. A
of a conventional scale beginning at zero.
form of artificial intelligence (AI) that allows a
expanded sweep 1. In an oscilloscope, speeding
computer or smart robot to act as a highly tal-
up the deflection of the beam during a selected
ented specialist in a specific field. An example is
portion of the trace. 2. The circuit for the action
the use of a computer to help a physician diag-
described in 1.
nose a complex disease. A smart robot might be
expander A circuit for increasing the dynamic
used as a surgical assistant.
range over which a signal or quantity can vary. A
exploring coil A pickup coil for sensing a signal or
typical example is the volume expander, a device
magnetic field. Sometimes called a sniffer.
that greatly increases the amplitude of strong sig-
exploring electrode 1. A sampling electrode sealed
nals while weakening, or having no effect on, sig-
in a discharge tube for measuring ionization at
nals of low amplitude.
the point of insertion. 2. Broadly, a test probe.
expansion 1. In communications, the process of
explosion-proof device A device that is housed
increasing the bandwidth of a signal, restoring it
and operated so that its sparking, heating, or
to normal bandwidth after it has been com-
production of radiant energy will not cause mate-
pressed. 2. In communications, a process in
rials in the environment to explode.
which stronger components are amplified more
exponent A number written as a superscript indi-
than weak ones, restoring a signal to its normal
cating the power to which another number (called
dynamic range after it has been compressed.
the base) is to be raised. For example, 22 is the
3. In computer operations, the restoration of a file
square (second power) of 2; x3 is the cube (third
to full or normal size after it has been compressed.
power) of x.
4. The widening of a meter scale. 5. The widening
exponential 1. A base (such as the natural num-
or magnification of an oscilloscope trace. Com-
ber e) modified by an exponent. 2. Related to a
change in value as determined by an exponent.
expansion chamber A cloud chamber for viewing
Thus, using increments for x in the equation y =
the paths of radioactive particles. It consists of a
ex produces an exponential curve.
closed glass cylinder containing humid air and a
exponential curve A curve based on powers of a
piston. An electrostatic field is applied through
number (such as for y = ex). Also see EXPONEN-
the cylinder, the piston is pulled quickly, and the
volume of the chamber expands. The temperature
inside falls below the dew point, a cloud is
exponential damping Damping action described
formed, and droplets of water condense on ions,
by an exponential curve.
making their paths visible for observation or pho-
exponential decay See EXPONENTIAL DE-
tography through the cylinder walls.
expansion ratio In communications, the inverse of
exponential decrease The continuous reduction
in the value of a quantity, according to the equa-
expansion time For an expansion chamber, the
tion y = e-x, which depicts the natural decay
interval during which expansion occurs. The
interval is kept short to ensure that the temper-
exponential function A function, such as f (x) = ex,
ature will drop low enough for vapor condensa-
that varies exponentially. See, for example, EX-
tion, and to minimize the possibility of
continuing gas motion distorting the track of a
exponential horn A horn of circular or rectangular
expectation In probability theory, the middle
cross section, whose cross-sectional area S at any
value (average or mean) of a random variable.
point x feet along its axis is given by the formula
expendable A component or system that, for econ-
S = S0emx, where S0 is the cross-sectional area at
omy, is best discarded instead of repaired when it
the throat, e is the natural logarithm base
fails. Also called DISPOSABLE COMPONENT.
exponential horn • external damping device

(approximately 2.71828), and m is the horn flar- extended memory In personal computer systems,
ing constant. memory beyond the first megabyte (1 MB). There
exponential increase The continuous increase of is no limit in theory to the extent of this memory,
a quantity, according to the equation y = ex, although it is limited by current technology. Used
which depicts the natural growth curve. in high-level programs”especially those involv-
exponential line A transmission line whose char- ing graphical applications, artificial intelligence,
acteristic impedance varies exponentially with its or intensive calculations. Resides in integrated
electrical length. circuits (ICs) in the computer, and is normally
exponential quantity A quantity involving an ex- volatile (i.e., it is not retained when power is re-
ponential (e.g., 3ex). moved). Compare EXPANDED MEMORY.
exponential series A mathematical series based extended octaves Audio-frequency tones above or
on exponential expressions. Example: ex = 1 + x + below the normal range of an electronic musical
(x2/2!) + (x3/3!) + (x4/4!) + . . . instrument. Special circuits must be added to
exponential sweep In cathode-ray-tube (CRT) de- make the extended octaves available.
vices, such as oscilloscopes, a beam sweep that extended play Pertaining to a recorded phono-
starts fast and slows exponentially. graph disc that provides a longer playing time
exponential transmission line See EXPONEN- than conventional discs of the same size and
TIAL LINE. recording speed.
exponential waveform Any waveform in which the extender A substance added to an encapsulant to
rate of change in the amplitude is directly or in- make it go further.
versely proportional to the instantaneous ampli- extensimeter See EXTENSOMETER.
tude. The absolute value of the derivative of such extension cable A flexible, low-capacitance (usu-
a waveform is equal to the absolute value of the ally concentric) cable for connecting part of one
instantaneous amplitude, multiplied by a con- circuit to part of another. Extension cables are
stant that depends on the amplitude units. available with a variety of end connectors.
exposure 1. The total amount of radiation received extension cord A flexible power cord having a
in a given area, or by a given sample, or by a per- male plug on one end and female receptacle on
son, over a specified length of time. 2. The extent the other.
to which a photographic film has been darkened extension loudspeaker An auxiliary loudspeaker
or otherwise modified by visible light, infrared, ul- serving areas in which the main speakers can™t be
traviolet, or X rays. adequately heard.
exposure meter 1. A usually simple instrument extensometer An instrument used to measure
for measuring light intensity”especially for pho- small amounts of expansion, contraction, or de-
tographic purposes. A common form consists of a formation.
self-generating photocell connected to a direct- exterior label On a diskette or tape cartridge used
current microammeter. 2. A device that indicates for computer data storage, a written identification
the amount of ionizing radiation that has been re- on the housing or cartridge, as opposed to the la-
ceived over a given period of time. bel, which is recorded on the diskette or tape itself.


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