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folded horn.
tive connections between the generator and the
backloading In a cascaded series of amplifiers, the
load.
tendency of loading effects to be passed to earlier
back conduction Conduction of current in the re-
stages. A change in the output impedance of a fi-
verse direction, as across a semiconductor junc-
nal amplifier circuit, for example, could also re-
tion that is reverse-biased.
sult in a change in the output impedance of the
back contact A contact that closes a circuit when a
driver circuit, and perhaps even in a change in
relay, switch, or jack is in its normal rest position.
the output impedance of the predriver.
back current Symbol, Ib. The normally small cur-
back lobe In the pattern of a directional antenna,
rent flowing through a reverse-biased pn semicon-
the lobe directly opposite the major lobe, repre-
ductor junction. Also called reverse current and
senting the radiation or response in or from a di-
inverse current. Compare FORWARD CURRENT.
rection 180 degrees from that in which the gain is
back diode A semiconductor diode that is normally
greatest.
back-biased (reverse-biased).
back echo An echo resulting from the rear lobe of
an antenna radiation pattern.
back emf See BACK VOLTAGE.
Back-Goudsmit effect See ZEEMAN EFFECT.
background 1. The context or supporting area of a
picture (e.g., the background of a television pic-
ture). 2. Background noise.
background control In a color television receiver,
a potentiometer used to set the dc level of the
color signal at one input of the three-gun picture
tube.
background count Residual response of a ra-
dioactivity counter in an environment as free as
practicable of radioactivity. This background is
caused largely by cosmic rays and inherent ra-
dioactivity of surrounding buildings and other
bodies.
background job A low-priority, relatively long-
running computer program that can be inter-
rupted so that a higher-priority program can be
run.
background noise Electrical noise inherent to a
particular circuit, system, or device that remains
when no other signal is present. backplate A flat electrode in a television (TV) cam-
background processing In a computer, the run- era tube that receives the stored-charge image via
ning of programs having low priority. capacitive coupling.
background radiation Nuclear radiation from ma- back porch In a television (TV) horizontal sync
terials in the environment. Also see BACK- pulse, the time interval between the end of the
GROUND COUNT. rise of the blanking pedestal and the beginning of
background response The response of a radiation the rise of the sync pulse. That portion of the flat
detector to background radiation. top of the blanking pedestal behind the sync
backing store In a computer, a device that stores pulse. Compare FRONT PORCH.
large amounts of information. In most small com- back-porch effect In transistor operation, the con-
puters, this is done via MAGNETIC DISK and/or tinuation of collector-current flow for a short time
MAGNETIC TAPE. A backing store can also be an after the input signal has fallen to zero.
optical storage medium, such as CD-ROM (com- back-porch tilt The departure of the top edge of a
pact disk, read-only memory). back porch from true horizontal.
backlash 1. Slack or lag in action of moving parts. back pressure sensor A device that detects and
Example: delay between initial application of a measures the torque that a motor is applying,
force (such as that required to turn a knob) and and produces a signal whose amplitude is pro-
movement of a part or device (e.g., a potentiome- portional to the torque. This signal can be used
ter or variable capacitor). 2. On a mechanical for various purposes. In a robotic device, for ex-
analog tuning dial, an arc within which slack or ample, the sensor output can be fed back to the
lag is discernible. motor control to limit the applied force.
backloaded horn A loudspeaker enclosure in back resistance Symbol, Rb. The resistance of a re-
which the front of the speaker cone feeds sound verse-biased pn semiconductor junction. Also
directly into the listening area, and the rear of the called REVERSE RESISTANCE.
58 back scatter • bail


backup facility In an electrical or communications
system, a facility that is intended for use when
the primary, or main, facility is not operational.
back voltage 1. Voltage induced in an inductor by
the flow of current through the inductor, so called
because its polarity is opposite to that of the ap-
plied voltage. Also called counter emf. 2. A voltage
used to obtain bucking action (e.g., the voltage
used to zero the meter in an electronic voltmeter
circuit). 3. Reverse voltage applied to a semicon-
ductor junction.
backwall In a pot core, the plate or disk that con-
nects the sleeve and center post to close the mag-
netic circuit.
backward diode A semiconductor diode manufac-
tured in such a way that its high-current flow oc-
curs when the junction is reverse biased. Such a
diode is also a negative-resistance device.
backward-wave oscillator Abbreviation, BWO. A
back scatter Scattering of a wave back toward a
microwave oscillator tube similar to the traveling-
radio transmitter from points beyond the skip
wave tube. Like the traveling-wave tube, the BWO
zone. This phenomenon is caused by ionospheric
contains a helical transmission line. In the elec-
reflection. Compare FORWARD SCATTER.
tron beam, electron bunching results from inter-
backstop A contact or barrier (such as a screw or
action between the beam and the electromagnetic
post) that serves to limit the BACKSWING of the
field, and reflection occurs at the collector. The
armature of a relay.
wave moves backward from collector to cathode,
backswing 1. The tendency of a pulse to overshoot,
and oscillation is sustained because the back-
or reverse direction after completion. Backswing
ward wave is in phase with the input. Output is
is measured in terms of the overshoot amplitude
taken from the cathode end of the helix.
as a percentage of the maximum amplitude of the
pulse. 2. The extent to which a relay armature
moves back from a contact when the relay con-
Helical line
tacts are open.
Electron
back-to-back connection The connection of
gun
diodes or rectifiers in reverse parallel (i.e., the an-
ode of one to the cathode of the other) across a
signal line to pass both half cycles of ac in certain
control circuits. Output Collector
back-to-back sawtooth A symmetrical sawtooth
backward-wave oscillator
wave in which the rise slope is equal to the fall
slope. Also called triangular wave and pyramidal
wave. back wave The oscillator signal present in an am-
backup 1. An element, such as a circuit compo- plifier-keyed, continuous-wave (CW), Morse-code
nent, that is used to replace a main component, transmitter. Normally, this signal is at the same
in case of main-component failure. 2. Any pro- frequency as the transmitter output, but is not
cess or scheme that serves to maintain opera- sufficiently strong to be radiated over the air.
tion of a system in case of main-component back-wave radiation The condition wherein a back
failure. 3. A battery that maintains volatile wave is strong enough to be heard on a continu-
memory data stored in one or more integrated ous-wave (CW) keyed signal at the receiving sta-
circuits. 4. A computer file, or set of files, stored tion. This results from ineffective amplifier keying.
in a nonvolatile medium, such as diskettes or baffle A board on which a loudspeaker is mounted
magnetic tape, to prevent catastrophic data loss to separate acoustic radiation from the back of
in the event of hard-disk failure. 5. A battery or the cone from radiation emanating from the front.
alternative power source that keeps an alarm The baffle improves bass response by increasing
system operational in the event of a utility power the wavelength (lowering the frequency) at which
failure. phase cancellation occurs.
backup battery 1. In a computer or microcom- baffle plate 1. See BAFFLE. 2. A metal plate
puter-controlled electronic device, a source of mounted in a waveguide to reduce the cross-
voltage to preserve volatile memory data if the sectional area.
power is removed. 2. A battery used for powering bail A wire loop or chain that holds one member of
a system in the event that the main power source a two-member assembly to prevent loss (e.g., the
should fail. short chain holding the dust cap of a jack).
59
Bakelite • balanced low-pass filter


is a half-wave dipole at uniform height above elec-
Bakelite The trade name for a specialized plastic
trical ground, fed at the center with parallel-wire
dielectric material. Its chemical composition is
line. It is important that the transmission line
phenol-formaldehyde resin.
runs away from the antenna at a right angle for at
baker An obsolete phonetic alphabet code word for
least 1„4 wavelength, preferably 1„2 wavelength or
letter B. BRAVO is commonly used instead.
more, to prevent line imbalance caused by cur-
baking-out In the process of evacuating a system,
rents induced from the radiated field.
the procedure of heating the system to a high
balanced bridge Any four-leg bridge circuit in
temperature to drive out gases occluded in the
which all legs are identical in all electrical re-
glass and metal parts.
spects.
balance 1. See BRIDGE. 2. To null a bridge or sim-
balanced circuit 1. A circuit that has its electrical
ilar circuit. 3. To equalize loads, voltages, or sig-
midpoint grounded, as opposed to the single-
nals between two circuits or components. 4. In a
ended circuit, which has one side grounded. 2. A
high-fidelity stereo sound system, a control or set
bridge circuit in the condition of null.
of controls that adjusts the relative loudness of
balanced converter See BALUN.
the left and right channels. 5. Alignment of a bal-
balanced currents Currents with the same value.
anced modulator for minimum carrier output am-
In the two conductors of a balanced transmis-
plitude. 6. A condition in which two branches of a
sion line, these currents are equal in amplitude
circuit have identical impedances, relative to
and opposite in phase at every point along the
ground.
line.
balance coil 1. A type of autotransformer that en-
balanced delta A set of coils or generators in a
ables a three-wire ac circuit to be supplied from a
three-phase system, connected so that the cur-
two-wire line. A series of taps around the center of
rents in any two coils differ in phase by 120 de-
the winding enables the circuit to be compensated
grees.
for unequal loads. 2. See BALANCING COIL.
balanced detector A symmetrical demodulator,
balance control A variable component, such as a
such as a full-wave diode detector or a discrimi-
potentiometer or variable capacitor, that is used
nator.
to balance bridges, null circuits, or loudspeakers.
balanced electronic voltmeter An electronic volt-
balanced Having identical impedances, with re-
meter circuit in which two matched transistors
spect to ground.
are connected in a four-arm bridge arrangement.
balanced amplifier Any amplifier with two
The drift in one half of the circuit opposes that in
branches that have identical impedances, with
the other half; the resulting drift of the zero point
respect to ground. Usually, the two branches are
is virtually eliminated.
in phase opposition (180 degrees out of phase).
balanced filter A filter consisting of two identical
balanced antenna An antenna system where two
sections, one in each branch of a balanced sys-
halves are exact replicas of each other, geometri-
tem, such as a parallel-wire transmission line.
cally and electrically. Such an antenna normally
balanced input An input circuit whose electrical
must either be fed with a balanced transmission
midpoint is grounded. Compare SINGLE-ENDED
line or with a coaxial cable and balun.
INPUT.
balanced antenna system A balanced antenna, fed
balanced input transformer An input transformer
with a balanced transmission line, that has cur-
in which the center tap of the primary winding is
rents of equal magnitude in each side. An example
grounded.
balanced line A pair of parallel wires that pos-
Center-fed sesses a uniform characteristic impedance. The
horizontal two conductors are of the same material and have
radiator
identical diameters. The distance between them
is constant. In a balanced two-wire line, the cur-
rents in the two conductors are of equal ampli-
90° tude and opposite phase.
balanced lines In high-fidelity audio systems, a
cable that consists of two parallel conductors
surrounded by a single braid. The parallel wires
Two-wire carry the audio-frequency (AF) signals, and the
feed line braid is grounded for shielding.
balanced loop antenna A loop antenna with a
grounded electrical midpoint, determined by the
junction of two identical series-connected capaci-
Xmtr tors shunting the loop.
balanced low-pass filter A low-pass filter used in
a balanced system or balanced transmission
line.
balanced antenna system
60 balanced method • balun


balanced-to-unbalanced transformer See BALUN.
balanced method A system of instrumentation in
balanced transmission line See BALANCED LINE.
which a zero-center scale is used. The reading
balanced varactor tuning A two-varactor, back-
can be either side of the zero reading.
to-back circuit for adjusting the value of a ca-
balanced modulator A symmetrical modulator cir-
pacitor using an applied dc voltage. This
cuit using bipolar transistors, field-effect transis-
arrangement has an advantage over a single-
tors, an integrated circuit, or diodes as principal
varactor (unbalanced) circuit, because high-
components, that delivers an output signal con-
tuned-circuit Q is maintained and harmonic
taining the sidebands, but not the carrier. It is
generation is reduced.
commonly used to generate a double-sideband
balanced voltages In any symmetrical system,
(DSB) signal that can be filtered to obtain a
such as a balanced line or push-pull circuit, two
single-sideband (SSB) signal.
or more input or output voltages that are ad-
balanced multivibrator A switching oscillator cir-
justed to have the same amplitude and (usually)
cuit in which the two halves are identical in con-
opposite phase.
figuration, and as nearly identical as practicable
balanced-wire circuit A circuit or conductor sys-
in performance.
tem with identical halves that are symmetrical,
balanced network Any network intended to be
with respect to ground and to other conductors.
used with a balanced system or balanced trans-
balancing circuit See BUCKING CIRCUIT.
mission line. It is characterized by a pair of ter-
balancing coil In a receiver, a center-tapped an-
minals, each of which shows the same impedance
tenna coil that is balanced to ground to eliminate
with respect to ground.
MARCONI EFFECT.
balanced oscillator A PUSH-PULL OSCILLATOR.
ballast 1. A component that is used to stabilize the
balanced output Output balanced against ground
current flow through, or operation of, a circuit,
(e.g., where the electrical midpoint of the output
stage, or device. 2. An iron-core choke connected
circuit is grounded).
in series with one of the electrodes in a fluores-
balanced output transformer 1. A push-pull out-
cent or other gas-discharge lamp.
put transformer with a center-tapped primary
ballast resistor 1. A nonlinear inductive power re-
winding. 2. An output transformer with a
sistor whose voltage-current (EI) characteristic is
grounded center tap on its secondary winding.
such that current through the resistor is inde-
pendent of voltage over a useful range. This fea-
ture enables the ballast resistor to act as an
automatic voltage regulator when it is simply
connected in series with a power supply and load.
Input
Output 2. A small (usually high-resistance) resistor oper-
ated in series with a glow lamp, such as a neon
lamp, to prevent overload.
ballast transformer A misnomer often used in
place of BALLAST, 2.
ballistic galvanometer An undamped galva-
nometer that is used particularly to observe elec-
tric charges by noting the single throw resulting
from the momentary flow of current through the
galvanometer coil.
ballistics The electronics-supported science con-
balanced output transformer, 2.
cerned with the motion of projectiles and similar
bodies in air or space.
balloon antenna A vertical antenna consisting of a
balanced probe A probe, such as one for an elect-
wire or wires held aloft by a captive balloon. Occa-
ronic voltmeter or oscilloscope, that has a bal-
sionally, used by radio amateurs and shortwave
anced input and (usually) a single-ended output.
listeners at low and medium frequencies. A poten-
balanced-tee trap A wavetrap constructed in a T
tially dangerous antenna because of large static-
configuration, with a resonant section in each
electric buildup, a tendency to attract lightning,
conductor of a balanced transmission line.
the possibility of its breaking loose, and the risk of
balanced telephone line A telephone transmis-
accidental contact with high-voltage power lines.
sion line that has two sides, similar to a balanced
balop Contraction of BALOPTICON.
radio-frequency transmission line. Either side
balopticon An opaque-picture projecting system in
has the same impedance, with respect to ground.
which the picture is viewed by a television (TV)
balanced termination A load device (or the prac-
camera, such as a vidicon, and displayed by a
tice of using such a device) in which the sections
picture tube. Also called balop.
provide identical termination for each of the sec-
balun A specialized impedance-matching radio-
tions or conductors of a balanced system, such
frequency (RF) transformer. It is a wideband device,
as a balanced line.
61
balun • bandstop


usually providing a 1:1 or 1:4 impedance ratio against all frequencies except a specific frequency
and available in several different forms. It is so f0, or a band of frequencies between two limiting
called because it has an unbalanced input suit- frequencies f0 and f1. In a parallel inductance-
able for coaxial transmission lines, and a bal- capacitance (LC) circuit, the device exhibits high
anced output suitable for dipole, Yagi, and quad impedance at the desired frequency or frequen-
antennas. cies and a low impedance at unwanted frequen-
banana jack The female half of a two-part quick- cies. In a series configuration, the filter has a low
connector combination. Splicing of a circuit is impedance at the desired frequency or frequen-
completed by inserting a BANANA PLUG into this cies and a high impedance at unwanted freque-
jack. ncies. Compare BAND-REJECTION FILTER,
banana plug The male half of a two-part quick- HIGH-PASS FILTER, LOW-PASS FILTER.
connector combination, with sides usually com- bandpass flatness The degree to which a bandpass
posed of flat springs that ensure contact with the device™s attenuation-versus-frequency curve is a
female BANANA JACK into which it is inserted. straight line with zero slope within the passband.
band pressure level The net acoustic pressure of a
sound source within a specified frequency range
(band).
band-rejection filter Also called a band-stop filter.
Any resonant circuit, or combination of resonant
circuits designed to discriminate against a spe-
cific frequency f0, or a band of frequencies be-
banana jack and plug tween two limiting frequencies f0 and f1. In a
parallel inductance-capacitance (LC) circuit, the
device exhibits high impedance at the desired fre-
quencies, and a low impedance at the unwanted
band 1. A continuous range of radio or television
frequency or range of frequencies. In a series con-
communications frequencies or wavelengths,
figuration, the filter has a low impedance at the
usually designated by the lowest and highest fre-
desired frequencies and a high impedance at the
quencies, or the approximate wavelength (e.g.,
unwanted frequency or range of frequencies.
the 20-meter amateur radio band). 2. A set of dis-
Compare BANDPASS FILTER, HIGH-PASS FIL-
crete radio or television frequency channels
TER, LOW-PASS FILTER, NOTCH FILTER.
within a specified range (e.g., the standard AM
band selector Any switch or relay that facilitates
broadcast band). 3. A range of wavelengths for in-
switching the frequency of a radio transmitter, re-
frared, visible, ultraviolet, X-ray, or gamma-ray
ceiver, or transceiver among various bands.
energy. 4. A range of energy levels. 5. A colored
bandset capacitor In some older communications
stripe on a resistor or capacitor that forms part of
receivers, a variable capacitor is used to preset
the code that indicates component value and tol-
the tuning range in each band to correspond to
erance.
graduations on the tuning dial. This capacitor is
band center 1. In a given radio or television com-
a trimmer or padder operated in conjunction with
munications band, the arithmetic mean of the
the main tuning capacitor.
lowest and highest frequencies. 2. In a given
bandspreading In some older communications re-
band, the geometric mean of the longest and
ceivers, the process of widening the tuning range
shortest wavelengths.
within a given frequency band to cover the entire
band-elimination filter See BAND-REJECTION
dial. Otherwise, the band would occupy only a
FILTER.
portion of the dial, and tuning would be difficult.
band gap In any atom, the difference in electron en-
It is usually accomplished with a BANDSPREAD
ergy between the conduction and valence bands.
TUNING CONTROL whose range is preset via the
bandpass 1. The frequency limits between which a
main tuning control and/or a BANDSET CAPAC-
BANDPASS FILTER or BANDPASS AMPLIFIER
ITOR.
transmits ac energy with negligible loss. 2. The
bandspread tuning control An analog adjustment
ability to allow passage of signals at a given fre-
in some older communications receivers that al-
quency or band of frequencies while blocking
lows continuous tuning over a desired band of
other signals. Compare BANDSTOP.
frequencies. This control is separate from the
bandpass amplifier An amplifier that is tuned to
main tuning control.
pass only those frequencies between preset limits.
bandstop 1. The frequency limits between which a
bandpass coupling A coupling circuit with a flat-
BAND-REJECTION FILTER blocks, or greatly
topped frequency response so that a band of fre-
attenuates, ac energy. 2. The ability to suppress
quencies, rather than a single frequency, is
or block signals of a given frequency or band
coupled into a succeeding circuit. Also see BAND-
of frequencies, while allowing signals of other
PASS, 1.
frequencies to pass with little or no attenuation.
bandpass filter Any resonant circuit, or combina-
Compare BANDPASS.
tion of resonant circuits, designed to discriminate
62 bandstop filter • bar meter


bandstop filter See BAND-REJECTION FILTER. CODE. The laser beam moves across the tag. The
band suppression 1. The property of blocking, or beam is reflected from the white regions between
greatly attenuating, signals within a specific fre- the lines, but is absorbed by the dark lines them-
quency band. 2. The frequency limits between selves. This produces modulation of the reflected
which a device or circuit rejects or blocks ac en- beam by the data contained in the tag.
ergy, while passing energy at other frequencies bare conductor A conductor with no insulating cov-
with negligible loss. ering, a common example being bare copper wire.
band-suppression filter See BAND-REJECTION bar generator A special type of radio-frequency
FILTER. signal generator that produces horizontal or ver-
bandswitch A low-reactance selector switch (usually tical bars on the screen of a television receiver. It
rotary) that facilitates changing the tuning range of is used in adjustment of horizontal and vertical
a radio receiver, transmitter or transceiver from linearity.
one band of frequencies to another. bar graph A graphical presentation of data, in
bandswitching In a receiver, transmitter, or test which numerical values are represented by hori-
instrument, the process of switching self- zontal bars of width that correspond to the val-
contained tuned circuits to change from one fre- ues. This type of graph is nonstandard in the
quency spectrum to another within the range of sense that the ordinate is horizontal, whereas it is
the device™s intended operation. usually vertical. Compare COLUMNAR GRAPH.
bandwidth 1. For a communications or data sig- bar-graph meter See BAR METER.
nal, a measure of the amount of spectrum space barium Symbol, Ba. An elemental metal of the al-
the signal occupies. Usually, it is given as the dif- kaline-earth group. Atomic number, 56. Atomic
ference between the frequencies at which the sig- weight, 137.36. It is present in some compounds
nal amplitude is nominally 3 dB down with used as dielectrics (e.g., barium titanate).
respect to the amplitude at the center frequency. barium-strontium oxides The combined oxides of
These frequencies represent the half-power barium and strontium used as coatings of
points of the amplitude-versus-frequency func- vacuum-tube cathodes to increase electron emis-
tion. In general, the bandwidth increases as the sion at relatively low temperatures.
data rate (in bits per second, baud, or words per barium strontium titanate A compound of bar-
minute) increases. 2. Also called NECESSARY ium, strontium, oxygen, and titanium that is
BANDWIDTH. The minimum amount of spectrum used as a ceramic dielectric material. It exhibits
space normally required for effective transmis- ferroelectric properties and is characterized by a
sion and reception of a communications or data high dielectric constant.
signal. 3. See BANDPASS, 1. barium titanate Formula, BaTi02. A ceramic used
bank A collection of usually similar components as the dielectric in ceramic capacitors. It exhibits
used in conjunction with each other, usually in a high dielectric constant and some degree of ferro-
parallel configuration. Some examples are resis- electricity.
tor bank, lamp bank, and transformer bank. Barkhausen effect The occurrence of minute
banked transformers Parallel-operated trans- jumps in the magnetization of a ferromagnetic
formers. substance as the magnetic force is increased or
bankwound coil A coil wound in such a way that decreased over a continuous range.
most of its turns are not side by side, thus reduc- Barkhausen interference Interference that results
ing the inherent distributed capacitance. from oscillation because of the BARK-HAUSEN
bar 1. Abbreviation, b. The cgs unit of pressure, in EFFECT.
which 1 b = 105 pascals per square centimeter. 2. bar magnet A relatively long permanent magnet in
A horizontal or vertical line produced on a televi- the shape of a bar with a rectangular or square
sion (TV) screen by a bar generator and used to cross section.
check linearity. 3. A thick plate of piezoelectric bar meter A digital meter that displays a quan-
crystal. 4. A solid metal conductor, usually unin- tity, such as signal strength, incrementally, us-
sulated, of any cross section. 5. A silicon ingot ing a set of LEDs or LCDs arranged in a straight
from which semiconductor devices can be fabri- line. Its main advantage is that it has no moving
cated. parts, yet (unlike direct-readout digital meters)
BAR Abbreviation of BUFFER ADDRESS REGIS- gives the viewer some impression of the way a
TER. rapidly fluctuating quantity changes. Its chief
bar code A printed pattern that contains data that
can be recovered by laser scanning. It is com-
monly used for the pricing and identification of
store merchandise. It can also be used by an as-
sembly or maintenance robot as an aid to identi-
fying tools.
bar-code reader A laser scanning device that re-
covers the data from a tag that contains a BAR
63
bar meter • baseband frequency response


disadvantage is that it does not provide a precise barrier potential The apparent internal dc poten-
indication. tial across the barrier (see BARRIER, 1) in a pn
barn Symbol, b. A non-SI unit of nuclear cross sec- junction.
tion equal to 100 square femtometers or 10“ 24 barrier strip A terminal strip having a barrier (see
square centimeters. This unit is approved as BARRIER, 2) between each pair of terminals.
compatible with SI (International System of
Units).
Barnett effect The development of a small amount
of magnetization in a long iron cylinder that is ro-
tated rapidly about its longitudinal axis.
barograph A recording barometer, using either a
drum recorder (pen recorder) or a computer to
store the data as a function of atmospheric pres-
sure versus time.
barometer An instrument for measuring atmo-
spheric pressure.
barometer effect A relation that appears to exist
between the intensity of cosmic rays and the at- barrier strip
mospheric pressure. It is an inverse relation; that
is, increasing pressure seems to correlate with re-
duced intensity of cosmic rays. It is said to be ap- barrier voltage The voltage required for the initia-
proximately to 1 or 2% per centimeter of mercury. tion of current flow through a pn junction.
barometric pressure The atmospheric pressure, Bartlett force See EXCHANGE FORCE.
usually given in inches of mercury. The average baryon A subatomic particle made up of three
barometric pressure at the surface of the earth is quarks.
just under 30 inches of mercury. base 1. In a bipolar transistor, the intermediate re-
bar pattern A series of spaced lines or bars (hori- gion between the emitter and collector, which
zontal, vertical, or both) produced on a television usually serves as the input or controlling element
picture screen by means of a BAR GENERATOR. of transistor operation. 2. A substance that dis-
It is useful in adjusting horizontal and vertical sociates in water solution and forms hydroxyl
linearity of the picture. (OH) ions. For example, sodium hydroxide. 3. The
barrage array An antenna array in which a string constant figure upon which logarithms are com-
of collinear elements are vertically stacked. The puted (10 for common logs, 2.71828 for natural
end quarter wavelength of each string is bent in logs). 4. The radix of a number system (e.g., base
to meet the end quarter wavelength of the oppo- 10 for the decimal system, base 8 for the octal
site radiator to improve balance. system, base 16 for the hexadecimal system, and
barrage jamming The jamming of many frequen- base 2 for the binary system). 5. A fixed non-
cies, or an entire band, at the same time. portable radio communications installation.
barrell distortion Television picture distortion base address The number in a computer address
consisting of horizontal and vertical bulging. that serves as the reference for subsequent ad-
barrier 1. The carrier-free space-charge region in a dress numbers.
semiconductor pn junction. 2. An insulating par- baseband The frequency band of the modulating
tition placed between two conductors or termi- signal in a communications, broadcast, or data
nals to lengthen the dielectric path. transmitter. For voice communications, this is
barrier balance The state of near equilibrium in a generally the range of voice frequencies necessary
semiconductor pn junction (after initial junction for intelligible transmission. For high-fidelity mu-
forming), entailing a balance of majority and mi- sic broadcasting, it is approximately the range of
nority charge carrier currents. human hearing. For fast-scan television, it
barrier capacitance 1. The capacitance in a bipolar ranges up to several megahertz. It can be re-
transistor between the emitter and collector. It stricted or expanded, depending on the nature of
varies with changes in applied voltage, and also the transmitted signal. See BASEBAND FRE-
with the junction temperature. 2. The capacitance QUENCY RESPONSE.
across any pn junction that is reverse-biased. baseband frequency response 1. The amplitude-
barrier height The difference in voltage between versus-frequency characteristic of the audio-
opposite sides of a barrier in a semiconductor frequency (AF) or composite video section of a
material. transmitter that defines the BASEBAND, or range
barrier layer See BARRIER, 1. of modulating frequencies. 2. The range of fre-
barrier-layer cell A photovoltaic cell, such as the quencies over which a radio transmitter can be
copper oxide or selenium type, in which photons modulated to convey information. For single side-
striking the barrier layer produce the potential band (SSB), it is approximately 300 Hz to 3 kHz;
difference. for high-fidelity, frequency-modulated (FM) music
64 baseband frequency response • BASIC


transmission, it is about 10 Hz to 20 kHz or 30
kHz; for fast-scan television, it consists of fre-
quencies up to several megahertz. This range is
determined by bandpass and/or lowpass filters
in the AF or composite video section of the trans-
mitter.
base bias The steady dc voltage applied to the base
electrode of a transistor to determine the operat-
ing point along the transistor characteristic
curve.
base-bulk resistance The resistance of the semi-
conductor material in the base layer of a bipolar
transistor.
base-charging capacitance In the common-
emitter connection of a bipolar transistor, the in-
ternal capacitance of the base-emitter junction.
base current Symbol, IB. Current flowing through Base
the base electrode of a bipolar transistor. Also see line
AC BASE CURRENT and DC BASE CURRENT.
base electrode See BASE, 1. Also called base ele-
ment.
base element 1. Base electrode. 2. One of the ba-
sic metals, such as iron or tin, that are not gen-
erally considered precious (as opposed to
base line
NOBLE).
base-e logarithm See NAPIERIAN LOGARITHM.
base film The plastic substrate of a magnetic used to provide support for the device and to al-
recording tape. low a physical connection between the socket ter-
base frequency 1. The frequency of the principal, minal, into which it fits, and one of the internal
or strongest, component in a complex signal or electrodes of the device.
waveform; also called basic frequency. 2. The fre- base plate The chassis plate upon which compo-
quency of operation of a base-station transmitter nents are mounted before wiring.
when the receiver is tuned to a second channel. base potential See BASE VOLTAGE.
base-input circuit A common-collector circuit, base region See BASE, 1.
common-emitter circuit, or emitter follower. base resistance Symbol, RB. Resistance associated
base insulator A stout dielectric insulator, used to with the base electrode of a bipolar transistor.
support a heavy conducting element and keep the Also see AC BASE RESISTANCE and DC BASE
conductor isolated from other possible conduc- RESISTANCE.
tors or conductive paths. base resistor The external resistor connected to
base line In visual alignment procedures involving the base of a bipolar transistor. In the common-
an oscilloscope and radio-frequency (RF) sweep emitter circuit, the base resistor is analogous to
generator, a zero-voltage reference line developed the gate resistor of a field-effect transistor (FET)
by the generator as a horizontal trace on the os- circuit.
cilloscope screen. base spreading resistance Symbol, rBB. In a bi-
baseline stabilizer A clamping circuit that holds polar transistor, the bulk-material resistance of
the reference voltage of a waveform to a predeter- the base region between the collector junction
mined value. Also called DC RESTORER. and emitter junction.
base-loaded antenna A usually vertical antenna or base station The head station or fixed home sta-
radiating element, the electrical length of which is tion in a communication network.
adjusted by means of a loading coil or tuned cir- base-10 logarithm Abbreviation, log10. A logarithm
cuit in series with, and positioned at the bottom based on the decimal number 10. If log10 (x) = y,
then 10y = x. Base-10 logarithms are commonly
of, the antenna or radiator.
base material In printed circuits, the dielectric used in engineering. Compare NAPIERIAN LOGA-
material used as a substrate for the metal pat- RITHM.
tern. Also called base medium. base voltage Symbol, VB. The voltage at the base
base notation The numbering or radix system electrode of a bipolar transistor. Also see AC
used in any application (as octal, decimal, binary, BASE VOLTAGE and DC BASE VOLTAGE.
or hexadecimal). BASIC Acronym for BEGINNER™S ALL-PURPOSE
base number See BASE, 4. SYMBOLIC INSTRUCTION CODE, a relatively
base pin One of the straight prong-like terminals primitive, but versatile and easy-to-learn com-
on an electrical or electronic component; it is puter language developed at Dartmouth College.
65
basic frequency • battery


basic frequency 1. The FUNDAMENTAL FRE- the speech level to be increased without overmod-
QUENCY of a signal, as opposed to one of its har- ulating a transmitter. It also allows smaller audio
monics. 2. See BASE FREQUENCY, 1. transformers to be used because transformer
basic protection Devices and procedures essential core size must increase as the frequency it passes
to minimize the risk of damage to electronic decreases.
equipment, and/or injury or death to its opera- bassy In audio and high-fidelity applications, a
tors, as a result of lightning. Hardware provisions sound in which the low-frequency components,
include a substantial earth ground, heavy-gauge below about 500 Hz, are overly predominant.
grounding wire, lightning arrestors for antennas, BAT Abbreviation of BATTERY.
and transient suppressors for power connections. batch fabrication process The manufacture of de-
The safest procedure is to disconnect and ground vices in a single batch from materials of uniform
all antennas, and unplug all equipment from util- grade. Particularly, the manufacture of a large
ity outlets, during electrical storms and/or when number of semiconductor devices from one batch
the apparatus is not in use. Radio communi- of semiconductor material by means of carefully
cations equipment with outdoor antennas, in controlled, identical processes.
particular, should not be operated during batch processing In digital-computer operations,
thunderstorms. the processing of quantities of similar informa-
basket The structure that supports the cone in an tion during a single run.
acoustic loudspeaker. bat-handle switch A toggle switch, the lever of
basket-weave coil A type of single-layer inductor which is relatively long and thick, and is shaped
in which adjacent turns do not parallel each like a baseball bat.
other around the circumference, but zigzag oppo-
sitely as a strand does in the woven pattern of a
basket. This reduces distributed capacitance.
bass Low audio frequencies (AF) corresponding to
low-frequency musical notes or sounds.
bass boost 1. The special emphasis given to low
audio frequencies (the bass notes) by selective
circuits in audio systems. 2. The technique of in-
creasing the loudness of the bass, relative to the
higher audio frequencies, to render a more faith-
ful reproduction of sound at low volume levels.
bass compensation See BASS BOOST, 2.
bass control 1. A manually variable potentiometer
for adjusting bass boost of an amplifier or sound
system. 2. The arrangement of components that
are required to achieve amplitude variation of
bass in an audio signal.
bat-handle switch
bass port In a loudspeaker, a hole in the cabinet
that enhances the low-frequency (bass) sound
output. Used in high-fidelity audio systems. bathtub capacitor A (usually oil-filled) capacitor
bass-reflex enclosure A loudspeaker cabinet with housed in a metal can that looks like a miniature
a critically dimensioned duct or port that allows bathtub.
back waves to be radiated in phase with front bathyconductorgraph An instrument that is used
waves, thus averting unwanted acoustic phase to measure the electrical conductivity of seawa-
cancellation. ter.
bass-reflex loudspeaker A loudspeaker mounted bathythermograph An instrument that plots a
in a bass reflex enclosure. Also see ACOUSTICAL graph of temperature versus depth in a body of
PHASE INVERTER. water, such as a lake or an ocean.
bass-resonant frequency The low frequency at batten Supporting bars or braces that hold a loud-
which a loudspeaker or its enclosure displays speaker in place within its cabinet, and/or that
resonant vibration. hold the cabinet panels in place.
bass roll-off 1. The attenuation of the low-fre- battery Abbreviations, B, BA. BAT. A device con-
quency (bass) component in a high-fidelity audio sisting of two or more interconnected electro-
signal. 2. A control that allows adjustable attenu- chemical or photovoltaic cells that generate dc
ation of the low-frequency component in a high- electricity. The cells can be connected in series to
fidelity audio signal. supply a desired voltage, in parallel to supply a
bass suppression In speech transmission, the re- desired current-delivering capability, or in series-
moval of all frequencies below about 300 Hz, on parallel to obtain a desired voltage and current-
the assumption that those frequencies contribute delivering capability. Also see CELL, EDISON
little to intelligibility. This suppression permits BATTERY, LEAD-ACID BATTERY, PHOTO-
66 battery • beacon


VOLTAIC CELL, PRIMARY BATTERY, and STOR- length, the interpretation of which depends on
AGE BATTERY. the history of the previous transmission or an ad-
battery acid 1. A chemical acid, such as sulfuric ditional case bit.
acid, used as the electrolyte of a battery. 2. Collo- baud rate 1. A colloquial expression for data speed
quially, any cell or battery electrolyte, whether in BAUD. 2. Colloquial, and technically inaccu-
acid, base, or salt. rate, expression for data speed in BITS PER SEC-
battery capacity The current-supplying capability OND.
of a battery, usually expressed in ampere-hours Baume (Antione Baume, 1728“1804). Abbreviation,
(Ah). Be. Pertaining to the Baume scales for hydrome-
battery cell See CELL, 1. ters. The two such scales are for liquids heavier
battery charger 1. A specialized dc power supply, than water and for liquids lighter than water.
usually embodying a stepdown transformer, rec- bay One of several sections of a directional an-
tifier, and filter. It is used to charge a storage bat- tenna array.
tery from an ac power line. 2. A motor-generator bayonet base The insertable portion of a plug-in
combination used to charge a storage battery component (e.g., a lamp) that has a projecting pin
from an ac power line. 3. A combination of solar that fits into a slot or keyway in the shell of the
cells, generators, or other voltaic transducers, socket into which the component is inserted.
that are used to charge a storage battery with dc bayonet socket A socket with a suitably slotted




Y
obtained from a nonelectrical energy source. shell for receiving the bayonet base of a plug-in
battery clip 1. A heavy-duty metallic clamp that is component.




FL
used for quick, temporary connection to a large bazooka A linear BALUN, in which a quarter wave-
cell terminal, such as that of a lead-acid storage length of metal sleeving surrounds a coaxial
battery. 2. A small connector of the snap-fastener feeder, and is shorted to the outer conductor of
type, used for quick connection to a small power the feeder to form a shorted quarter-wave section.
AM
source, such as a transistor-radio battery. bb Abbreviation of BLACKBODY.
battery eliminator A specialized dc power supply, BBC Abbreviation of British Broadcasting Corpora-
usually embodying a transformer, rectifier, and tion.
filter, that permits battery-powered equipment to BBM Abbreviation of BREAK BEFORE MAKE.
be operated from an ac power line. b-box The index register of a computer.
TE

battery holder 1. A case or container of any kind BC Abbreviation of BROADCAST.
for holding a cell or battery. 2. A shelf for holding BCD Abbreviation of BINARY-CODED DECIMAL.
a cell or battery. 3. A small, metal bracket-type BCFSK Abbreviation of BINARY CODE FRE-
device for holding a cell or battery between two QUENCY-SHIFT KEYING.
contacts. B channel One of the channels of a two-channel
battery life 1. The ampere-hour or watt-hour ca- stereophonic system. Compare A CHANNEL.
pacity of a battery. 2. The number of times that a BCI Abbreviation of BROADCAST INTERFERENCE.
rechargeable electrochemical battery can be cy- BCL Amateur radio abbreviation of BROADCAST
cled before it becomes unusable. 3. The nominal LISTENER.
length of time (e.g., hours, days, or weeks) that an BCN Abbreviation of BEACON.
electrochemical battery will function effectively in BCO Abbreviation of BINARY-CODED OCTAL.
a given application before it must be discarded or BCST Abbreviation of BROADCAST.
recharged. BDC Abbreviation of BINARY DECIMAL COUNTER.
battery memory See MEMORY DRAIN. B display A radar display in which the target is
battery receiver A usually portable radio or televi- represented by a bright spot on a rectangular-
sion receiver operated from self-contained batter- coordinate screen. Compare A DISPLAY and J
ies. DISPLAY.
battery substitute See BATTERY ELIMINATOR. Be Symbol for BERYLLIUM.
bat wing On a television (TV) or frequency-modula- Be Abbreviation of BAUME.
tion (FM) broadcast receiving antenna, a metallic beacon 1. A beam of radio waves, or a radio signal,
element with a shape that resembles that of a that is used for navigation and/or direction find-
bat™s wing. ing. 2. A transmitter that radiates a beam of radio
baud A unit of communications processing speed waves, or a radio signal, as an aid in navigation
in telegraphy and digital data communications and/or direction finding. 3. A signal transmitted
systems. Often confused with bits per second continuously on a specific frequency, to help ra-
(bps). Baud refers to the number of times per sec- dio operators ascertain propagation conditions.
ond that a signal changes state. The speed in bps 4. A station or transmitter that generates and ra-
is generally higher than the speed in baud, some- diates a signal to help radio operators determine
times by a factor of several times. Compare BITS propagation conditions. 5. In robotics, a device or
PER SECOND. system that aids in navigation. For example, tri-
Baudot code A machine communications code corner reflectors can be positioned in strategic
that uses five parallel binary digits of equal locations, and a mobile robot equipped with a




Team-Fly®
67
beacon • beam parametric amplifier


television (TV) camera tube, the lining-up of the
scanning infrared laser. The robot controller de-
electron beam so that it is perpendicular to the
termines the distance to any given reflector by
target. 3. In a cathode-ray tube, the positioning of
measuring the time required for the laser beam to
the electron rays so that they converge properly
return. In this way, two mirrors can allow the
on the screen, regardless of the deflection path.
robot to locate its position in two dimensions;
beam angle In the radiation from an antenna, the
three mirrors can facilitate position determina-
direction of most intense radiation, the side limits
tion in three-dimensional space.
of which are determined by the points at which
beacon direction finder A direction finder using a
the field strength drops to half the value in the
signal received from a beacon station.
principal direction.
beacon receiver A receiver that is specially
beam antenna 1. A multielement directional an-
adapted for the reception of beacon signals (see
tenna, consisting of a half-wave driven dipole and
BEACON, 1 and 3).
one or more parasitic elements. See YAGI AN-
beacon station 1. A station broadcasting beacon
TENNA. 2. Any directional antenna used for
signals (see BEACON, 1 and 3) for direction find-
transmitting and receiving radio-frequency (RF)
ing, navigation, and/or determination of radio-
signals.
wave propagation conditions. 2. Sometimes, a
beam bender 1. In a television (TV) picture tube,
radar transmitting station.
the ion-trap magnet. 2. Deflection-plate correc-
beacon transmitter A transmitter specially
tion device or circuit.
adapted for the transmission of beacon signals
beam bending Deflection of an electron beam by
(see BEACON, 1 and 3).
electric or magnetic fields.
bead 1. A small ferromagnetic ring that is used as
beam blanking See BLANK, 2.
a passive decoupling choke by slipping it over the
beam convergence The meeting, at a shadow-
input power leads of a circuit or stage, or around
mask opening, of the three electron beams in a
a coaxial transmission line. 2. A magnetic mem-
three-color television picture tube. See BEAM
ory element in a ferrite-core matrix.
ALIGNMENT, 3.
beaded coax A low-loss, coaxial transmission line,
beam coupling A method of producing an alternat-
in which the inner conductor is separated from
ing current between two electrodes by passing a
the outer conductor by means of spaced dielectric
density-modulated beam of electrons between the
beads.
electrodes. This, in effect, demodulates the elec-
beaded support A plastic or dielectric bead that is
tron beam, recovering the information.
used to support the inner conductor of an air-
beam crossover Either of the half-power points
insulated transmission line of coaxial construction.
in the beam of a directional antenna, usually in
bead thermistor A thermistor consisting essentially
the horizontal plane. The reference point is con-
of a small bead of temperature-sensitive resistance
sidered to be the direction of maximum radia-
material into which two leads are inserted.
tion.
beam 1. The more-or-less narrow pattern of radia-
beam current The current represented by the flow
tion from a directional antenna. 2. A directional
of electrons in the beam of a cathode-ray tube.
antenna”especially a YAGI ANTENNA. 3. The
beam cutoff In an oscilloscope or television picture
stream or cloud of electrons emitted by the cath-
tube, the complete interruption of the electron
ode in an electron tube”especially a BEAM
beam, usually as a result of highly negative con-
POWER TUBE.
trol-grid bias.
beam alignment 1. The lining-up of a directional
beam deflector A deflection plate in an oscillo-
transmitting antenna with a directional receiving
scope tube.
antenna for maximum signal transfer. 2. In a
beam efficiency In a cathode-ray tube, the ratio of
the number of electrons generated by the gun to
the number reaching the screen. The efficiency is
high in electromagnetic-deflection tubes and
lower in electrostatic-deflection tubes.
beam lead In an integrated circuit, a relatively
thick and strong lead that is deposited in contact
with portions of the thin-film circuit. It provides
stouter connections than continuations of the
thin film would provide.
beam-lead isolation In an integrated circuit, re-
duction of distributed capacitance and other in-
teraction through use of beam leads.
beam modulation See INTENSITY MODULATION.
beam parametric amplifier A PARAMETRIC AM-
PLIFIER in which the variable-reactance compo-
nent is supplied by a modulated electron beam.
beam alignment
68 beam-positioning magnet • beat marker


tween the half-power points in the horizontal
beam-positioning magnet In a three-gun color
plane. Occasionally, it is measured in the verti-
television picture tube, a permanent magnet that
cal plane.
is used to position one of the electron beams cor-
bearing The direction of an object or point ex-
rectly, with respect to the other two.
pressed in degrees within a 360° horizontal clock-
beam power tube A tetrode or pentode vacuum
wise boundary, with the center of the circle
tube, in which special deflector plates concentrate
serving as the observation point.
the electrons into beams in their passage from
bearing resolution In radar operations, the mini-
cathode to plate. The beam action greatly increases
mum horizontal separation of two targets, in de-
plate current at a given plate voltage. It is used in
grees, that permits the individual targets to be
some radio-frequency (RF) power amplifiers.
displayed as two echoes, rather than one.
beam-rider control system A missile-guidance
beat Any one of the series of pulsations constitut-
system in which a control station sends a radio
ing a beat note, which results from heterodyning
beam to a missile. The beam is moved in such a
one signal against another.
way that as the missile stays within the beam, it
beat frequency Either of two frequencies fC1 and
hits the target.
fC2 resulting from the mixing of two signals of dif-
beam-rider guidance 1. An aircraft landing guid-
ferent frequencies fA and fB. Frequency fC1 is the
ance system, in which the aircraft follows a radio
sum of the two input frequencies; fC1 = fA + fB.
beam in its glide path. 2. The circuitry in a guided
Frequency fC2 is the difference; fC2 = fA “ fB when
missile using a beam-rider control system.
fA is the higher of the two input frequencies.
beam splitter A device used to divide a light beam
beat-frequency oscillator Abbreviation, BFO. An
(as by a transparent mirror) into two compo-
oscillator used to set up audible beat frequen-
nents, one transmitted and the other reflected;
cies with an incoming received signal and in-
hence, a BEAM-SPLITTING MIRROR.
stalled in the intermediate-frequency (IF) stages
beam splitting In radar, a method of calculating
of a superheterodyne communications receiver.
the mean azimuth of a target from the azimuth at
For single-sideband (SSB) reception, the BFO is
which the target is first revealed by one scan, and
set at the frequency of the received suppressed
the azimuth at which the target information
carrier. In continuous-wave (CW) Morse code re-
ceases.
ception, the BFO is set at a frequency that dif-
beam-splitting mirror In an oscilloscope-camera
fers from that of the incoming signal by about
system, a tilted, transparent mirror that allows
400 to 1000 Hz. The resulting tone has an audio
rays to pass horizontally from the oscilloscope
frequency equal to the difference between the
screen to the camera and to be reflected vertically
BFO frequency and the received signal carrier
to the viewer™s eye.
frequency. For reception of frequency-shift-
beamwidth of antenna The angular width of the
keyed (FSK) signals, the BFO is set to such a fre-
main lobe of the pattern of radiation from a di-
quency that the resulting audio beat notes are
rectional antenna. Generally, it is measured be-
appropriate for the mark and space inputs of a
terminal unit or modem.
Half-power
width

AF
IF
Mixer amp.
amp.


From
BFO
previous Audio
IF stage output

beat-frequency oscillator

beating 1. Also called heterodyning. The combina-
tion of signals of different frequencies resulting in
sum and difference frequencies. 2. The fluttering
noise heard when two audio tones, very close in
frequency and very similar in amplitude, are
emitted at the same time.
beat marker In the visual (oscilloscopic) alignment
of a tuned circuit, a marker pip that results from
the beat note between the sweep-generator signal
and the signal from a marker oscillator.
beamwidth of antenna
69
beat note • Be0


beat note The sum or difference frequency that re- a hollow metal sphere at the upper end, where
sults from the heterodyning of two signals or, un- they are removed and spread to the surface of the
der some conditions, of more than two signals. sphere, which they raise to a potential up to sev-
beat-note reception 1. Reception in which a ra- eral million volts.
dio-frequency carrier is made audible by hetero- benchmark A test standard to measure product
dyning it with a beat-frequency oscillator (BFO) to performance.
produce an audible beat note. 2. Superhetero- benchmark routine A routine designed to evaluate
dyne reception (see SUPERHETERODYNE CIR- computer software and/or hardware, producing a
CUIT). good indication of how well the software or hard-
beat tone A beat note in which the frequency is ware will perform in real-life situations. In par-
within the range of hearing. ticular, tests instructions per second and
beaver tail A flat or elongated radar beam, wide in throughput, thereby producing an indication of
the azimuth plane. Primarily used to determine the overall computer power in applications, such
the altitude of a target. The beam is moved up as word processing, database, spreadsheet,
and down to find the target elevation. graphics, animation, and mathematical calcula-
Becquerel effect A phenomenon in which a volt- tions.
age is produced when radiant energy, such as in- bench test An extensive checkout of a piece of
frared, visible light, ultraviolet, or X-rays, falls on equipment in the test laboratory”either to find
one electrode in an electrolytic cell. an intermittent problem, or to check for reliabil-
bedspring A directional antenna consisting of a ity.
broadside array with a flat reflector and one or bend An angular shift in the lengthwise direction of
more helical driven elements. a waveguide.
beep A test or control signal, usually of single tone bending effect 1. The downward refraction of a
and short duration. radio wave by the ionosphere. 2. The low-
beeper 1. A pocket- or hand-carried transceiver” atmosphere turning of a radio wave downward by
especially one for maintaining two-way contact temperature discontinuity and atmospheric in-
with personnel who are away from their base. 2. versions.
An acoustic transducer that produces a beep in Benito A continuous-wave method of measuring
response to an input signal. the distance of an aircraft from the ground, in-
beetle A urea formaldehyde plastic used as a di- volving the transmission of an audio-modulated
electric material and as a container material. signal from ground and the retransmission back
bel Abbreviation, B. The basic logarithmic unit to ground by the aircraft. The phase shift between
(named for Alexander Graham Bell) for express- the two signals is proportional to the distance to
ing gain or loss ratios. One bel is equivalent to a the aircraft.
power gain of 10. Also see DECIBEL. bent antenna An antenna that has its driven ele-
bell An electric alarm device consisting of a metal- ment bent, usually near the ends and at right an-
lic gong that emits a ringing sound when it is gles, to conserve space.
struck by an electrically vibrated clapper. bent gun A television picture tube neck arrange-
Bellini-Tosi direction finder A direction finder in ment having an electron gun that is slanted to di-
which the sensing element consists of two trian- rect the undesired ion beam toward a positive
gular vertical antennas crossed at right angles, electrode, but which allows the electron beam to
the antennas being open at the top and accord- pass to the screen. This prevents the ion beam
ingly not acting as conventional coil antennas. from “burning” a permanent spot on the phoso-
bell-shaped curve A statistical curve (so called por of the screen.
from its characteristic shape) that exhibits a nor- Be0 Formula for beryllium oxide. Also see BERYL-
mal distribution of data. Typically, the curve de- LIA.
scribes the distribution of errors of measurement
around the real value.
bell transformer A (usually inexpensive) stepdown Ion trap
transformer that operates an electric bell or simi- Cathode magnet
First anode
lar alarm or signaling device from the ac power
Second anode
line.
bell wire Insulated 18-gauge (AWG) solid copper
wire, so called because of its principal early use
Electron
in the wiring of electric-bell circuits.
beam
belt generator Also known as a Van de Graaff gen-
erator. A very-high-voltage electrostatic genera-
Control
tor, a principal part of which is a fast-traveling
grid
endless belt of dielectric material. At the lower
end, charges of one sign are sprayed on the belt
at 10 to 100 kV dc and are carried to the inside of bent gun
70 berkelium • biased off


berkelium Symbol, Bk. A radioactive elemental few feet above ground and run in a straight line
metal produced artificially. Atomic number, 97. for one to several wavelengths. It is generally
Atomic weight, 247. used for reception at low and medium frequen-
beryllia Formula, Be0. Beryllium oxide, used in cies, the best response is to vertically polarized
various forms as an insulator and structural ele- signals arriving from one or both directions in
ment (as in resistor cores). line with the wire. It can be left unterminated for
beryllium Symbol, Be. An elemental metal. Atomic bidirectional response, or it can be terminated at
number, 4. Atomic weight, 9.01218. Beryllium is its far end by a noninductive resistor of about 600
present in various dielectrics and alloys used in ohms for a unidirectional response.
electronic components. beyond-the-horizon propagation See FORWARD
Bessel functions Sophisticated mathematical SCATTER.
functions for dealing with periodic electronic phe- bezel A faceplate for an electronic instrument,
nomena in which the waveform often displays usually having a fitted rim and cutouts for knobs,
decrement. Also called cylindrical functions. switches, jacks, etc.
beta Symbol, β. The current gain of a common- BFO Abbreviation of BEAT-FREQUENCY OSCIL-
emitter bipolar transistor stage. It is the ratio of LATOR.
the induced change of collector current to the ap- BG Abbreviation of BIRMINGHAM WIRE GAUGE.
plied change of base current: β = dIC/dIB. Also abbreviated BWG.
beta circuit The output-input feedback circuit in B-H curve A plot showing the B and H properties of
an amplifier. a magnetic material. Magnetizing force H is plot-
beta cutoff frequency The frequency at which the ted along the horizontal axis, and flux density B
current amplification of a bipolar transistor falls is plotted along the vertical axis.
to 70.7% of its low-frequency value. B-H loop See BOX-SHAPED LOOP.
beta particles Minute radioactive subatomic bits B-H meter Any instrument for displaying or evalu-
identical to the electron or positron, and emitted ating the hysteresis loop of a magnetic material.
by some radioactive materials. Also see BETA bhp Abbreviation of brake horsepower.
RAYS. Bi Symbol for BISMUTH.
beta rays Rays emitted by the nuclei of radioactive bias 1. Any parameter of which the value is set to a
substances, consisting of a stream of beta parti- predetermined level to establish a threshold or
cles (i.e., electrons or positrons) that move at ve- operating point. Although it is common to think
locities up to 299.8 million meters per second. of bias currents and bias voltages, other parame-
Compare ALPHA PARTICLE and GAMMA RAYS. ters (e.g., capacitance, resistance, illumination,
beta-to-alpha conversion For a bipolar transistor, magnetic intensity, etc.) can serve as biases. 2. In
the conversion of current amplification expressed a high-fidelity audio system, a circuit in a tape
as beta (β) to current amplification expressed as recorder/player that optimizes performance for a
alpha (±): ± = β/(β + 1). particular type of recording tape.
betatron A particle accelerator in which injected bias current A steady, constant current that pre-
electrons are given extreme velocity by being pro- sets the operating threshold or operating point
pelled in circular paths in a doughnut-shaped of a circuit or device, such as a transistor,
glass container. The term comes from the fact diode, or magnetic amplifier. Compare BIAS
that high-speed electrons constitute BETA PAR- VOLTAGE.
TICLES. bias current drift The ratio of a change in input
beta videocassette recorder The earliest scheme bias current to a change in ambient temperature,
for videocassette recording, developed by Sony generally expressed in nanoamperes per degree
corporation in the 1970s. Compare VHS video- Celsius.
cassette recorder. bias distortion Distortion caused by operation of a
beta zinc silicate phosphor Formula, (Zn0 + tube or transistor with incorrect bias so that the
Si02):Mn. A phosphorescent substance used to response of the device is nonlinear.
coat the screen of a cathode-ray tube. The fluo- biased diode A diode having a dc voltage applied in
rescence is green-yellow. either forward or reverse polarity. Current flows
BeV Abbreviation of billion electronvolts. Also see readily through the forward-biased diode; the re-
ELECTRONVOLT, GEV, MEV, and MILLION verse-biased diode appears as an open circuit.
ELECTRONVOLTS. This abbreviation has been The biased diode is the basis of clippers, limiters,
supplanted by the SI (International System of slicers, and similar circuits.
Units) abbreviation GeV, for GIGAELECTRON- biased off In a circuit or device, the state of cutoff
VOLTS. caused by application of a control-electrode bias.
bevatron An accelerator (see ACCELERATOR, 1) Examples include collector-current cutoff (when
similar to the synchrotron, which accelerates the dc base bias of a bipolar transistor reaches a
particles to levels greater than 10 GeV. critical value), and drain-current cutoff (when the
Beverage antenna (Harold H. Beverage.) A nonres- dc gate bias reaches a critical value in a field-
onant, directional long-wire antenna, erected a effect transistor).
71
biased search • bifilar electrometer



N
N
P
P
»/4

Reverse Forward
bias bias
Feed
biased diodes

»/4
biased search A scheme that a mobile robot can
use to find its way to a destination or target, by
deliberately searching off to the side and then
homing in as the approach progresses. It is so
called because the general nature of the initial er-
ror (bias) is known, although its exact extent need biconical antenna
not be known.
bias oscillator In a magnetic recorder, an oscilla-
bidecal base The 20-pin base of a cathode-ray
tor operated at a frequency in the 40-kHz to 100-
tube. Also see DIHEPTAL, DUODECAL, and
kHz range to erase prerecorded material and bias
MAGNAL.
the system magnetically for linear recording.
bidirectional Radiating or receiving (usually
bias resistor A usually fixed resistor, such as the
equally) from opposite directions (e.g., front-and-
source resistor in a field-effect-transistor (FET) cir-
back radiation from an antenna or loudspeaker,
cuit or the emitter resistor in a bipolar-transistor
or front-and-back pickup with an antenna or mi-
circuit, across which a desired bias voltage is de-
crophone).
veloped by current flowing through the resistor.
bidirectional antenna An antenna with a direc-
bias set A control, such as a potentiometer or vari-
tional pattern that consists of maximum lobes
able autotransformer, that facilitates manual ad-
180 degrees apart.
justment of the dc bias of a circuit.
bidirectional bus In computers, a data path over
bias stabilization 1. The maintenance of a con-
which both input and output signals are routed.
stant bias voltage, despite variations in load
bidirectional bus driver In a microcomputer, a
impedance or line voltage. It is usually accom-
signal-driving device that permits direct connec-
plished by means of automatic voltage regulation.
tion of a buffer-to-buffer arrangement on one end
2. The stabilization of transistor dc bias voltage
(the interface to I/O, memories, etc.) and data in-
by means of resistance networks or through the
puts and outputs on the other. This device per-
use of barretters, diodes, or thermistors.
mits bidirectional signals to pass and provides
bias supply 1. Batteries that provide bias voltage
drive capability in both directions.
or current for bipolar or field-effect transistors. 2.
bidirectional counter A counter that can count
A line-operated unit for supplying dc bias and
consecutively up from a given number or down
consisting of a transformer, rectifier, and high-
from that number. Also called UP-DOWN
grade filter.
COUNTER.
bias voltage A steady voltage that presets the op-
bidirectional current A current that flows in both
erating threshold or operating point of a circuit or
directions. Utility alternating current (ac) is a
device, such as a transistor. Compare BIAS CUR-
common example.
RENT.
bidirectional loudspeaker A loudspeaker that de-
bias windings The dc control windings of a sat-
livers sound waves to the front and rear.
urable reactor or magnetic amplifier.
bidirectional microphone A microphone that
biconical antenna A form of broadband antenna,
picks up sound waves equally well from the front
consisting of two conical sections joined at the
and rear.
apexes. The cones are at least 1„4 wavelength in di-
bidirectional transistor A symmetrical transistor
agonal height. The vertex angles of the cones can
(i.e., one in which the two main current-carrying
vary, although the apex angle is usually the same
electrodes can be interchanged without influenc-
in each cone. The vertex angle affects the feed-
ing device performance). Some field-effect tran-
point impedance. Such an antenna radiates, and
sistors (FETs) are of this type; the drain and the
responds optimally to, signals with polarization
source can be interchanged.
parallel to the axis of the cones.
bifilar electrometer An electrometer in which the
biconical horn antenna A double-horn micro-
sensitive element consists of two long platinized-
wave antenna that radiates along relatively sharp
quartz fibers. When an electric potential is ap-
front and back beams.
72 bifilar electrometer • bimorphous cell


plied, the fibers separate by a distance propor-
tional to the voltage.
R1 R1
R3
bifilar resistor A wirewound resistor with two op-
positely wound filaments. The nature of the wind-
ing tends to cancel the inductance, making the R2 R2
device useful at a much higher frequency than an
ordinary wirewound resistor.
R1 R3 R1
bifilar transformer A transformer in which unity
coupling is approached by interwinding the pri-
mary and secondary coils (i.e., the primary and
secondary turns are wound side by side and in
the same direction).
bifilar winding 1. A method of winding a coil (such
as a resistor coil) in the shape of a coiled hairpin
so that the magnetic field is self-canceling and
the inductance is minimized. 2. A method of
winding transformers to minimize leakage reac-
tance. C1
C2
C1


L1
L1



bifilar winding


bifurcated contact A forked contact whose parts
act as two contacts in parallel for increased relia- bilateral network
bility.
bilateral amplifier An amplifier that transmits or
receives in either direction equally well (i.e., the half-wave dipole. But they can be at varying an-
input and output can be exchanged at will). gles, as in a long-wire antenna.
bilateral antenna A bidirectional antenna, such as bimetal A union of two dissimilar metals”espe-
a loop antenna or a half-wave dipole. cially those having a different temperature coeffi-
bilateral element A circuit element or component cient of expansion. The two are usually welded
(as a capacitor, resistor, or inductor) that trans- together over their entire surface.
mits energy equally well in either direction. Com- bimetallic element A strip or disk of bimetal.
pare UNILATERAL ELEMENTS. When the element is heated, it bends in the di-
bilateral network A network, usually passive and rection of the metal that has the lower tempera-
either balanced or unbalanced, that has BILAT- ture coefficient of expansion; when cooled, it
ERAL SYMMETRY. Thus, the input and output unbends. Usually, an electrical contact is made
terminals can be exchanged without affecting the at one extreme or the other so that the element
performance of the network in any way. can serve as a thermostat.
bilateral symmetry 1. Exhibiting symmetry, with bimetallic switch A temperature-sensitive switch
respect to a vertical line or plane. 2. For a net- based on a bimetallic element.
work, having the property that if the input and bimetallic thermometer A thermometer based on
output are reversed, the circuit behavior remains a bimetallic element that is mechanically coupled
precisely the same. See BILATERAL NETWORK. (as through a lever and gear system) to a pointer
3. For an amplitude-versus-frequency response that moves over a temperature scale.
curve, having the property that the right-hand bimetallic thermostat A thermostat in which a
and left-hand halves are mirror images of each bimetallic element closes or opens a pair of
other. switch contacts.
billboard antenna A phased group of dipole anten- bimorphous cell A piezoelectric transducer that
nas that lie in one plane. A reflector might be consists of two crystal plates, such as Rochelle
used behind the entire array. salt, bound intimately face to face. In a crystal
bilobe pattern An antenna radiation pattern con- microphone, vibration of the transducer results
sisting of two major lobes in a given plane, usu- in a voltage output; in a crystal headphone, an ac
ally the horizontal plane. Often the lobes exist in signal voltage impressed on the transducer
opposite directions relative to each other, as in a causes vibratory mechanical motion.
73
BiMOS • binaural


BiMOS A combination of bipolar and MOSFET circuit to be preset to deliver an output pulse only
transistors in an integrated circuit. Thus, a typi- after a predetermined number of input pulses.
cal BiMOS device can have MOSFET input for binary relay See BISTABLE RELAY.
high impedance and bipolar output for low binary scaler In its simplest form, a single two-
impedance. stage device, such as a flip-flop, which functions
binant electrometer An electrometer in which a as a divide-by-two counter, because one output
thin platinum vane (“the needle”) is suspended pulse results from every two input pulses.
within two halves of a metal pillbox-shaped con- Higher-order scaling is obtained by cascading
tainer. The halves or binants are biased with a dc stages.
voltage of 1 to 12 V, and the unknown voltage is binary search A system of search entailing the
applied to the vane. It is also called DUANT successive division of a set of items into two parts
ELECTROMETER and HOFFMAN ELECTROME- and the rejection of one of the two until all items
TER. of the sought-for kind are isolated.
binary 1. Pertaining to the base-2 number system.
Thus, binary arithmetic uses two digits: 0 and 1.
2. Pertaining to two-element chemical com-




{
pounds.
binary arithmetic Mathematical operations per-
formed using only the digits 0 and 1.
binary cell In a computer memory, an element
that can display either of two stable states.
binary chain A cascade of binary elements, such
as flip-flops, each unit of which affects the stable
state of the succeeding unit in sequence.




{
binary channel Any channel whose use is limited
to two symbols.
binary code A system of numbers representing
quantities by combinations of 1 and 0; a binary-
number system.
binary-coded decimal notation In digital com-
puter operations, a system of notation in which
each digit of a decimal number is represented by
its binary equivalent. Thus, the decimal number
327 in BCD notation becomes 0011 0010 0111.
(By contrast, in pure binary notation, 327 is
101000111.)
binary-coded octal notation A method of num-
binary search
bering in which each base-8 digit is represented
by a binary number from 000 to 111.
binary-controlled gate circuit A gate circuit con- binary signal Any signal that can attain either of
trolled by a binary stage. An example is a gating two states. Such a signal is always a digital sig-
transistor that receives its on/off pulses from a nal.
flip-flop. binary-to-decimal conversion 1. The automatic
binary counter A counter circuit consisting of a conversion of a number represented by a series of
cascade of bistable stages. Each stage is a scale- binary pulses into the corresponding decimal
of-two counter because its output is on for every number, which then is displayed by a readout de-

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