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universal receiver A radio receiver that can be op-
erated either from alternating current or direct
current (i.e., from utility power or battery power).
unity coupling
universal shunt See AYRTON-MATHER
GALVANOMETER SHUNT.
universal time See GREENWICH MEAN TIME.
unity gain The condition in which the output am-
universal transformer See UNIVERSAL OUTPUT
plitude is the same as the input amplitude; that
TRANSFORMER.
is, a gain factor of 1, or 0 dB.
universal transmitter A radio transmitter that
unity-gain bandwidth 1. For an active filter, the
can be operated either from alternating current or
bandwidth between the frequencies at which the
direct current (i.e., from utility power or battery
gain is 0 dB. 2. For an operational amplifier hav-
power).
ing a rolloff of 6 dB per octave, the frequency at
universal Turing machine In computer theory, a
which the open-loop gain is 0 dB.
TURING MACHINE capable of simulating other
uni-univalent electrolyte An electrolyte that dis-
Turing machines.
sociates into two univalent ions [e.g., sodium
universal vendor marking See UNIVERSAL
chloride (NaCl)].
PRODUCT CODE.
univ Abbreviation of universal.
universal winding A zigzag winding used to reduce
UNIVAC The name given to a family of digital com-
the distributed capacitance of multilayer coils.
puters and data-processing systems. The name is
Also called lattice winding and honeycomb wind-
an acronym for Universal Automatic Computer.
ing.
univalent Having a valence of 1. For example, in the
universal-wound coil A coil using a universal
compound sodium chloride (NaCl), the sodium ion
winding. Such coils are common in intermediate-
(Na+) and the chlorine ion (Cl“) are univalent.
frequency (IF) transformers and in radio-
universal bridge A bridge for the measurement of
frequency (RF) chokes.
capacitance (C), inductance (L), and resistance
712 univibrator • unsaturated operation


univibrator See MONOSTABLE MULTIVIBRATOR. data, it has been packed (as a memory-conserva-
unknown quantity Any variable quantity sought tion measure).
in calculations; it is usually represented by low- unpolarized light Light in which the wave orienta-
ercase italic letters from the second half of the al- tion is random around the axis of the beam.
phabet (e.g., x, y, z). unpolarized plug A plug that can be inserted into
unlike charges Dissimilar electric charges (i.e., a socket in two or more different ways, thus in-
positive and negative). creasing the likelihood of a wrong connection.
unlike poles Dissimilar poles, such as the north Compare POLARIZED PLUG.
and south poles of a magnet. unpolarized receptacle A receptacle into which a
unload 1. To remove data from a file. 2. To discon- plug can be inserted in two or more different
nect the load from a circuit. ways, thus increasing the likelihood of a wrong
unloaded amplifier See UNTERMINATED AMPLI- connection. Also called UNPOLARIZED SOCKET.
FIER. Compare POLARIZED RECEPTACLE.
unloaded antenna An antenna operated without unpolarized relay A relay that always closes in
added inductance or capacitance. the same direction, regardless of the direction of
unloaded-applicator impedance In dielectric- current in its coil. Also called nonpolarized
heating operations, the unloaded impedance of relay.
applicator electrodes placed in their normal unpolarized socket A socket into which a compo-
working position without the dielectric-material nent or plug can be inserted in two or more dif-
load in place. ferent ways, thus increasing the likelihood of
unloaded battery 1. A battery in the standby condi- wrong connections. Also called UNPOLARIZED
tion. 2. A battery tested for open-circuit terminal RECEPTACLE.
voltage (i.e., with no load, except the voltmeter). unprotected antenna An outside antenna oper-
unloaded generator See UNTERMINATED GEN- ated without a lightning arrester or grounding
ERATOR. switch. Increases the risk of damage to equip-
unloaded line See UNTERMINATED LINE. ment, such as radio receivers and transmitters,
unloaded potentiometer A potentiometer or volt- connected to the antenna. It also increases the
age divider with an open-circuited output. danger to personnel using the equipment.
unloaded Q The Q factor (degree of selectivity) of a unrationalized systems of units Collectively, the
coil or tuned circuit that is activated by a signal, absolute centimeter-gram-second (cgs) electro-
but that delivers no output to a load. static system of units, the absolute cgs electro-
unloaded transmitter A transmitter operated un- magnetic system of units, and the absolute
der open-circuit conditions (i.e., without an exter- meter-kilogram-second (mks) system of units.
nal load, such as an antenna or dummy resistor). unreflected ray See UNREFLECTED WAVE.
unmanned factory A manufacturing plant run unreflected wave 1. See DIRECT WAVE. 2. See
largely by robots and computers. There must GROUND WAVE. 3. An electromagnetic wave that
generally be at least one human being, whose penetrates the ionosphere and passes into space.
job(s) is/are to oversee and maintain the opera- unregulated Not held to a constant value. For ex-
tion of the machines. ample, an unregulated voltage is free to fluctuate
unmatched elements 1. Components (such as re- in value.
sistors, capacitors, semiconductors, etc.) having unregulated power supply A power supply whose
different values. 2. Mating elements or devices output current or voltage is not automatically
not having the same impedance. Also called held to a constant value. Compare CONSTANT-
MISMATCH. CURRENT SOURCE and CONSTANT-VOLTAGE
unmodulated carrier See CONTINUOUS WAVE. SOURCE.
unmodulated current A current whose character- uns Abbreviation of UNSYMMETRICAL.
istics (amplitude, phase, or frequency) are not unsaturated core A magnetic core operated below
varied by a signal or by noise. the point of saturation (i.e., below the point at
unmodulated voltage A voltage whose character- which an increase in coil current produces no
istics (amplitude, phase, or frequency) are not further increase in magnetization of the core).
varied by a signal or by noise. unsaturated logic A digital-logic scheme in which
unmodulated wave See CONTINUOUS WAVE. the switching devices operate between the satu-
unnilennium See MEITNERIUM. rated and cut-off conditions during either or both
unnilhexium See SEABORGIUM. of the high and low states.
unniloctium See HASSIUM. unsaturated operation Operation of a device at a
unnilpentium See DUBNIUM. point below saturation [i.e., below the point at
unnilquadium See RUTHERFORDIUM. which (1) an increase in voltage produces no fur-
unnilseptium See BOHRIUM. ther increase in current, or vice versa, or (2) an
unode See MONODE. increase in coil current produces no further in-
unpack In computer operations, to remove data crease in magnetization of a core]. Compare
from a storage location into which, with other SATURATED OPERATION.
713
unsaturated standard cell • ununoctium


unstable region The negative-resistance portion of
Unsaturated an N- or S-shaped response curve.
operation unstable servo A servo having unlimited output
drift.
unstable state A condition, such as a negative-
Saturation
Collector current

resistance region, that is difficult to maintain
point
and often results in oscillation. The negative-
resistance region of the tunnel diode forward-
conduction curve is evidence of such a state.
Compare STABLE STATE.
untapped winding A winding having two termi-
nals, one at either end, and no intermediate ter-
minals or connections. Also called untapped coil.
unterminated amplifier An amplifier operated
without a load device (i.e., under open-circuit
Base voltage
output conditions).
unterminated generator A generator operated
unsaturated operation
without a load device (i.e., under open-circuit
output conditions).
unterminated line A transmission line that is not
unsaturated standard cell See STANDARD CELL.
terminated with an impedance (i.e., an open-
unshielded cable A cable, such as a twisted pair or
ended line).
a multiwire twist, lacking a shielding jacket. Un-
untriggered flip-flop A flip-flop that, at a particu-
less special precautions are taken, such as trans-
lar instant, receives no actuating pulse, and that,
posing conductors, such a cable is susceptible to
therefore, does not change state.
stray pickup and is capable of radiation.
untuned amplifier A radio-frequency amplifier
unshielded choke An uncased choke (i.e., one with-
that is not tuned to a single frequency, but has
out a protective and shielding metal housing).
useful gain over a wide band of frequencies. Ex-
unshielded coil An inductor without a field-
amples are the distributed amplifier and the video
confining enclosure.
amplifier.
unshielded probe An instrument probe that has no
untuned filter See ALL-PASS FILTER.
shielding enclosure. Such a probe is desirable for
untuned line An aperiodic transmission line (i.e.,
some tests, but it is subject to antenna-pickup ef-
one that is only tuned to a particular frequency
fect, body capacitance, and stray-field pickup.
by its own distributed characteristics).
unshielded stage In electronic equipment, a stage
untuned transformer A transformer having sim-
operating entirely in the open (i.e., without elec-
ple primary and secondary windings and no tun-
trostatic or magnetic shielding enclosures). It is,
ing devices (such as capacitors in series or
therefore, susceptible to stray pickup and is ca-
parallel with the windings), and designed so that
pable of radiation.
its natural resonant frequency (because of dis-
unshielded transformer 1. An uncased trans-
tributed capacitance) lies outside the specified
former (i.e., one without a protective and shield-
range of operation.
ing metal housing). 2. A transformer having no
ununbium Symbol, Uub. Atomic number, 112.
electrostatic shield between its windings.
The most common isotope has atomic weight
unshift The mechanical action in a teletypewriter
277. Classified as a transition metal. It is human-
when the carriage moves from the figures position
made and not known to occur in nature.
to the letters position.
ununhexium Symbol, Uuh. Atomic number, 116.
unshunted current meter A single-range
The most common isotope has atomic weight
D™Arsonval milliammeter or microammeter that
289. First reported in January 1999. It is a de-
has no shunt resistor. The resistance of the in-
composition product of ununoctium, and it in
strument is, therefore, equal to the resistance of
turn decomposes into ununquadium. It is not
the movable coil.
known to occur in nature.
unsolder To separate wires, contacts, or fastenings
ununnilium Symbol, Uun. Atomic number, 110.
by melting the solder that holds them together.
The most common isotope has atomic weight
Also called DESOLDER.
269. Classified as a transition metal. It is
unsophisticated electronics Electronics theory
human-made and not known to occur in
and operations of the simplest kind, involving lit-
nature.
tle or no mathematics. It is generally intended for
ununoctium Symbol, Uuo. Atomic number, 118.
a hobbyist audience. Compare SOPHISTICATED
The most common isotope has atomic weight
ELECTRONICS.
293. It is the result of the fusion of krypton and
unstable oscillation 1. Relaxation oscillation.
lead, and decomposes into ununhexium. It is not
2. The periodically interrupted oscillation charac-
known to occur in nature.
teristic of a blocking oscillation.
714 ununquadium • uranium rays


ununquadium Symbol, Uuq. Atomic number, 114.
The most common isotope has atomic weight
285. First reported in January 1999. It is human-
made, and not known to occur in nature.
unununium Symbol, Uuu. Atomic number, 111.
The most common isotope has atomic weight
272. Classified as a transition metal. It is human-
made, and not known to occur in nature.
unused time See UNATTENDED TIME.
unweighted average In the statistical analysis of
data, an average calculated from terms not
weighted by a factor. Compare WEIGHTED AV-
ERAGE. Also see UNWEIGHTED TERM.
unweighted term In the statistical analysis of
data, a term not operated upon by a weighting
factor. Therefore, it has no extraordinary influ-
ence on a final result, such as an average. Com-
pare WEIGHTED TERM.
unwind To eliminate all redundant or unnecessary
operations in a computer system.
up-and-downer amplifier In broadcasting and
sound amplification, an auxiliary amplifier that
allows the level of sound effects and background
music to be controlled automatically without dis-
turbing the dialogue levels.
UPC Abbreviation of UNIVERSAL PRODUCT CODE.
upconv Abbreviation of UP CONVERTER.
up convert In superheterodyne conversion, to het-
erodyne a signal to an intermediate frequency suppressed. Compare DOUBLE SIDEBAND,
higher than the signal frequency. Compare SUPPRESSED CARRIER, LOWER SIDEBAND,
DOWN CONVERT. and SUPPRESSED CARRIER.
update In data-processing operations, to make a UPS Abbreviation for UNINTERRUPTIBLE POWER
file reflect the current status of pertinent infor- SUPPLY.
mation by using transactions for its modification. upside down 1. In radioteletype, a signal in which
up-down counter See BIDIRECTIONAL COUNTER. the MARK and SPACE signals are reversed in fre-
uplink 1. The signal sent up to a satellite quency. 2. In single sideband, reception of a sig-
transponder. 2. The frequency of the signal sent nal on the wrong sideband, resulting in “monkey
up to a satellite transponder. chatter.”
uplink frequency 1. The specific frequency of a up time See SERVICEABLE TIME.
given signal sent up to a satellite transponder. upturn A usually sudden rise in a performance
2. The band of frequencies sent up to a satellite curve. Compare DOWNTURN.
transponder. There can be many signals in an upward modulation Modulation in which the out-
uplink; there can also be many different stations put current of the modulated circuit increases
sending uplink signals within the band. during modulation. Compare DOWNWARD MOD-
uplink power 1. The power output of the transmit- ULATION.
ter sending the signal up to a satellite transpon- UR Abbreviation of ULTRARED.
der. 2. The effective radiated power of the station uranium Symbol, U. A radioactive metallic
sending the uplink signal. element. Atomic number, 92. Atomic weight,
uplink station Any station that transmits a signal, 238.03.
or group of signals, up to a satellite transponder. uranium 235 Symbol, U-235. An isotope of ura-
upper atmosphere See IONOSPHERE, STRATO- nium of mass number 235, used in atomic bombs
SPHERE, and TROPOSPHERE. and atomic power plants.
upper sideband Abbreviation, USB. In an ampli- uranium 238 Symbol, U-238. An isotope of uranium
tude-modulated wave, the component whose fre- of mass number 238, which, under fast-neutron
quency is the sum of the carrier frequency and bombardment, decays to become neptunium and
the modulation frequency. Compare LOW-ER then plutonium (of mass number 239).
SIDEBAND. uranium metals The group of heavy, radioactive
upper sideband, suppressed carrier Abbreviation, elements of atomic numbers 89 through 103.
USSC. A single-sideband transmission technique Also called the actinide series.
in which the upper sideband is transmitted, the uranium rays The ionizing radiation emitted by
lower sideband is suppressed, and the carrier is uranium. In 1896, Antoine Henri Becquerel
715
uranium rays • UVM


observed that uranium salts emit rays (later iden- and/or use of a specific brand of computer, and
tified as alpha, beta, and gamma) that can pass who meet or otherwise interact to share their ex-
through bodies opaque to light and are capable of pertise with, or programs, for, the machine. Also
exposing a photographic plate. Also called Bec- applicable to similar groups of programmable-
querel rays. calculator owners.
urea formaldehyde resin A thermosetting, syn- user™s library A compilation of programs supplied
thetic resin used in the manufacture of a number to (by the vendor) or generated by a user group.
of plastic dielectric bodies and formed by the re- USM Abbreviation of underwater-to-surface missile.
action of urea with formaldehyde. USSC Abbreviation of UPPER SIDEBAND, SUP-
urea plastic Any of several thermosetting plastics PRESSED CARRIER.
having a urea base and used as a dielectric and UTC Abbreviation of UNIVERSAL COORDINATED
as a molding material in electronics (e.g., urea TIME.
formaldehyde resin). utility 1. An organization providing a public ser-
URSI Abbreviation of Union Radio Scientifique Inter- vice, such as electric power or electronic commu-
nationale (International Radio Scientific Union). nications. 2. In computer operations, a program
ursigram A broadcast message giving information or set of programs intended for diagnosing
on sunspots, radio propagation, terrestrial mag- and/or correcting hardware and software prob-
netism, and related subjects. Also see URSI. lems.
usable frequency 1. Any frequency at which com- utility box A general-purpose aluminum or steel
munications can be maintained between two box, supplied in various convenient sizes (painted
points via ionospheric propagation. 2. Any fre- or unpainted), used as a housing or shield for
quency at which a communications system is op- electronic equipment.
erational. utility factor For a transformer used in a direct-
usable sample 1. The portion of an oscilloscope or current (dc) power supply, the ratio of dc output
monitor display that is visible on the screen. 2. In to required kilovolt-ampere (kVA) capacity.
statistics, a sample that is considered valid for utilization factor See UTILITY FACTOR.
calculation purposes. UTL Abbreviation of unit transmission loss.
USB Abbreviation of UPPER SIDEBAND. UUM Abbreviation of underwater-to-underwater
user friendliness 1. For electronic equipment and missile.
systems, the quality of being easy for people to UV 1. Abbreviation of ULTRAVIOLET. 2. Abbrevia-
operate. 2. The relative ease with which a ma- tion of UNDERVOLTAGE.
chine, especially a computer, can be operated by Uvicon A television camera tube in which a con-
people. ventional vidicon scanning section is preceded
useful life The elapsed time between the installa- by an ultraviolet-sensitive photocathode, an
tion of an expendable component, circuit, or sys- electron-accelerating section, and a special tar-
tem, and the time it must be replaced. get.
useful line In television, the portion of a scanning Uviol lamp An ultraviolet lamp using uviol glass”
line that can be used for picture signals. Also a special glass that is transparent to ultraviolet
called AVAILABLE LINE. rays.
user group A group of hobbyists or company rep- UVM Abbreviation of UNIVERSAL VENDOR
resentatives having in common the ownership MARKING.
Y
FL
AM
V 1. Abbreviation of VOLT. 2. Symbol (ital) for of an electron tube, are housed in an evacuated
VOLTAGE or POTENTIAL. 3. Symbol for VANA- space to protect them from the deterioration that
DIUM. 4. Symbol for VOLUME. 5. Symbol (ital) would result from open-air operation.
TE

for RELUCTIVITY. 6. Abbreviation of VERTICAL. vacuum capacitor A plate- or concentric-cylinder-
(Also, vert.) type capacitor sealed in an evacuated glass tube
v 1. Abbreviation of VELOCITY. 2. Abbreviation of or bulb. The vacuum acts as the dielectric and
VECTOR. provides a dielectric constant of 1 and very high
VA Abbreviation of VOLT-AMPERE. voltage breakdown.
V/A Abbreviation of volts per ampere (ohms). vacuum deposition The electrical application of a
VAC Abbreviation of vector analog computer. layer of one material (such as a metal) to the sur-
vac Abbreviation of VACUUM. face of another (the substrate), carried out in a
Vac Symbol for AC VOLTS. (Also, Vac.) vacuum chamber (e.g., evaporation and sputter-
vacancy In a crystal lattice, a position not occu- ing). Also see DEPOSITION and EVAPORATION,
pied by a nucleus. 1.
vacuum envelope The shell or tube of an electron
tube, X-ray tube, or other electron device that re-
quires a vacuum.
vacuum evaporation A method of manufacturing
thin-film circuits by vaporizing a substance, and
letting it accumulate or condense on a base.
vacuum gauge An instrument for measuring the
vacuum in a device being evacuated. One of the
Vacancies
several varieties of this gauge uses the elements
of a triode, which are sealed in part of the vac-
uum system, some characteristic of the tube be-
ing continuously monitored as the vacuum
pumping progresses. Another uses a thermistor
Bonds Nuclei
sealed in part of the system; the resistance of the
thermistor changes proportionately during the
vacuum pumping.
vacancy
vacuum impregnation The impregnation of a de-
vice (such as a capacitor, transformer, or choke
vacuum A space from which all air and other gases coil) in a vacuum chamber. The process causes
have been removed to the greatest practicable ex- the pores in the device and its insulating materi-
tent. Some electronic parts, such as the elements als to be completely filled with the impregnant.


Copyright © 2001 by The McGraw-Hill Companies, Inc.
Click here for Terms of ®
Use.
Team-Fly
717
vacuum level • V antenna


vacuum level 1. The pressure, in millimeters of val Abbreviation of VALUE.
mercury (mm/Hg). Normal atmospheric pressure valence A unit showing the degree to which ele-
is 760 mm/Hg. A perfect vacuum would be repre- ments or radicals (replaceable atoms or groups of
sented by 0 mm/Hg. 2. The proportion, or per- atoms) will combine to form compounds.
centage, of normal atmospheric pressure in a valence band In the energy diagram for a semicon-
given environment. ductor, the band of lowest energy. This band lies
vacuum phototube A phototube enclosed in an below the forbidden band (energy gap), which is
evacuated envelope, as opposed to one that is below the conduction band. Also see ENERGY
gas-filled. BAND DIAGRAM.
vacuum pump A pump for removing air and gases valence bond In a semiconductor material, an in-
from electron tubes, X-ray tubes, lamp bulbs, etc. teratomic path over which shared electrons
Such pumps include mechanical types, diffusion travel.
types, and combinations of these. Also see DIF- valence electrons Electrons in the outermost or-
FUSION PUMP. bits of an atom. These electrons determine the
vacuum range The range of a communications chemical and physical properties of a material.
system if propagation takes place through a Also see FREE ELECTRON.
perfect-vacuum (theoretical) medium. valence shells See ELECTRON SHELLS.
vacuum seal An airtight seal between adjoining validate To check data for correctness.
parts in an evacuation system. validity 1. Correctness or accuracy of data. 2. The
vacuum switch A switch that is enclosed in a vac- logical truth of a derivation or statement, based
uum bulb or tube to reduce contact sparking. on a given set of propositions.
vacuum thermocouple A thermocouple enclosed valley A dip between adjacent peaks in a curve or
in a vacuum bulb with a small heater element. wave.
Radio-frequency current passed through the valley current In a tunnel diode, the current at the
heater raises its temperature and causes the valley point.
thermocouple to generate a proportional direct- valley point The lowest point of finite current on
current voltage. the current-voltage response curve of a tunnel
vacuum tube An electron tube from which virtu- diode. Immediately before this point, current de-
ally all air and gases are removed. Also see ELEC- creases with increasing applied voltage (an indi-
TRON TUBE. cation of negative resistance). Beyond this point,
vacuum-tube amplifier An amplifier using one or however, the current again increases with in-
more vacuum tubes, rather than semiconductor creasing voltage. Compare PEAK POINT.
devices. valley voltage In a tunnel diode, the voltage at the
vacuum-tube bridge A special bridge for determin- valley point.
ing vacuum-tube characteristics by null meth- value 1. The level or magnitude of a quantity (e.g.,
ods. voltage value). 2. The worth of a system, proce-
vacuum-tube characteristics The operating pa- dure, device, etc., in terms of goal fulfillment or
rameters of a vacuum tube, such as plate cur- other criterion.
rent, grid voltage, input resistance, interelectrode valve Variation (Brit.) of ELECTRON TUBE. The
capacitances, amplification factor, transconduc- term was applied to the first tube, a diode (the
tance, etc., that describe tube performance. Fleming valve), and is descriptive of the action of
vacuum-tube coefficients See VACUUM-TUBE a tube (a controller of electric current), rather
CHARACTERISTICS. than its appearance.
vacuum-tube current meter An ammeter, mil- vanadium Symbol, V. A metallic element. Atomic
liammeter, microammeter, or nanoammeter em- number, 23. Atomic weight, 50.94.
bodying an amplifier that uses one or more Van Allen radiation belts Two high-altitude zones
vacuum tubes. Also see ELECTRONIC CURRENT that surround the earth and consist of high-
METER. energy subatomic particles. These belts were
vacuum-tube modulator A circuit using one or once thought to preclude space travel by humans
more vacuum tubes to impress a modulating sig- beyond the immediate vicinity of the earth.
nal on a carrier. Van de Graaff generator See BELT GENERATOR.
vacuum-tube rectifier 1. An alternating-to-direct- vane-anode magnetron A magnetron having plane
current converter circuit using one or more vac- parallel walls between adjacent cavities.
uum tubes, rather than gas tubes or vane attenuator A waveguide attenuator consist-
semiconductor devices. 2. A rectifier tube. ing essentially of a slab (vane) of resistive material
vacuum-tube sweep A sweep oscillator using a that slides laterally through the waveguide.
vacuum tube, rather than a gas tube. Also called vane instrument See IRON-VANE METER.
HARD-TUBE SWEEP. vane-type magnetron See VANE-ANODE MAG-
vacuum-tube voltmeter Abbreviation, vtvm. A NETRON.
voltmeter using a tube-type amplifier. Also see vane-type meter See IRON-VANE METER.
ELECTRONIC VOLTMETER. V antenna See VEE ANTENNA.
718 vapor lamp • variable inductor


vapor lamp A discharge lamp consisting essen- variable-capacitance transducer See CAPACI-
tially of a glass tube filled with a small amount of TIVE TRANSDUCER.
gas under low pressure and some element, such variable capacitor A capacitor that can be ad-
as mercury or sodium. A high voltage is applied justed from a low value (practically zero) to some
between electrodes sealed into each end of the maximum value. A step-type unit contains a
tube. The voltage causes the element to vaporize. number of fixed capacitors that can be switched
This, in turn, ionizes the gas, causing it to glow. in parallel with each other until, at the last step,
vapor pressure In a confined medium, the pres- all are in parallel. A continuously variable unit
sure of a gas, measured in atmospheres, pounds has a provision for moving one plate or set of
per square inch, or millimeters of mercury. plates, relative to another plate or set of plates; or
VAR Abbreviation of VOLT-AMPERES REACTIVE. one plate might be moved, with respect to an-
var Abbreviation of VARIABLE. other, so that the distance between them is
varactor A semiconductor-type voltage-variable changed. In a voltage-variable capacitor (such as
capacitor. Sometimes called a varactor diode. a varactor), capacitance varies in accordance
varactor amplifier A dielectric amplifier using a with an applied direct-current voltage.
varactor as the voltage-variable capacitor. variable-carrier modulation See QUIESCENT-
varactor flip-flop A bistable multivibrator based CARRIER OPERATION.
on the nonlinear performance of one or two var- variable connector In a flowchart, a path leading
actors. from a box in which a decision is made, to a num-
varactor frequency multiplier A frequency multi- ber of other points on the diagram.
plier (doubler, tripler, etc.) in which multiples of a variable coupling Coupling that is adjustable. In
fundamental frequency result from the nonlinear an inductively coupled circuit, the distance or an-
action of a varactor. gle between the coils is usually the adjustable
factor. In a capacitively coupled circuit, a variable
capacitor is generally used.
variable-density sound record In photographic
C1 and L1 tuned to f
sound-on-film recording, a sound track made by
C2 and L2 tuned to Fxn
varying, in sympathy with the sound frequency,
L1 the amount of light reaching the film. Compare
L2
C1 C2 VARIABLE-WIDTH SOUND RECORD.
variable-depth sonar A sonar device that can be
RF output (Fxn) placed far below the surface, for the purpose of
RF input (f )
detecting objects or terrain at greater depths than
would be possible with a surface-located sonar
device.
variable-efficiency modulation See EFFICIENCY
MODULATION.
variable-erase recording In magnetic-tape opera-
varactor frequency multiplier
tions, recording a signal by selectively erasing a
previously recorded signal.
varactor tuning A method of tuning a circuit or variable field 1. Any field with an intensity that
adjusting the frequency of an oscillator, using an changes with time. An electromagnetic field is a
inductor and a varactor to obtain the desired fre- common example. 2. In a computer record, a field
quency. The varactor acts as a variable capacitor. that is a variable block with a terminal symbol at
VAR-hour Abbreviation, VARh. Short for volt- the end.
ampere-reactive-hour, a unit of reactive energy; variable-frequency oscillator Abbreviation, VFO.
1 VARh can be represented by 1 VAR for 1 hour, An oscillator (usually self-excited) whose fre-
2 VAR for 0.5 hour, 0.5 VAR for 2 hours, etc. quency is continuously variable.
VAR-hour meter An instrument that measures re- variable-inductance pickup A phonograph pick-
active energy. up in which vibration of the stylus causes the in-
variable Abbreviation, var. A quantity whose value ductance of a small coil to vary in sympathy with
changes at some stated or calculable rate, and is the sound frequency.
given names in expressions or equations, such as variable-inductance transducer A transducer in
x, y, or z. Compare CONSTANT. Also see DEPEN- which a monitored quantity causes the induc-
DENT VARIABLE and INDEPENDENT VARIABLE. tance of a coil to vary proportionately. The coil
variable-area sound track See VARIABLE-WIDTH thereby offers a varying impedance to an
SOUND RECORD. alternating-current supply voltage.
variable block In computer operations, a unit of variable inductor An inductor whose value can be
data, such as a group of records, whose size is de- adjusted from zero to a certain maximum. The
pendent on data requirements (i.e., it is not fixed). variability might be in steps, provided by taps on
variable-capacitance diode See VARACTOR. the inductor, or a sliding contact can be used.
719
variable inductor • VATE


Several different inductors can be connected in Varicap A voltage-variable capacitor of the semi-
series and parallel combinations, with switches conductor-diode type. Also see VOLTAGE-
to facilitate variability. One type of variable in- VARIABLE CAPACITOR.
ductor uses a roller contact to allow continuous varicoupler An adjustable radio-frequency trans-
adjustment. See ROLLER INDUCTOR. Another former consisting of a primary coil (usually the
method of varying inductance is to change the rotor) and a secondary coil (usually the stator),
permeability of the core, such as by moving a rod the former being rotatable to vary the coupling
of ferrite or powdered iron in and out of the coil. between the coils. The inductance of the stator is
See VARICOUPLER and VARIOMETER. varied via a set of taps.
variable-pitch indication An audible signal used varindor A coil having a special core and whose in-
in lieu of, or in conjunction with, a meter to indi- ductance varies with the amount of direct current
cate voltage, current, logic state, etc. The higher flowing through the winding. Also see SAT-
the value of the measured quantity, the higher URABLE REACTOR.
the pitch. variocoupler A radio-frequency transformer in
variable-reluctance microphone A microphone in which one winding is rotatable, for the purpose of
which the impinging sound waves cause corre- adjusting the mutual inductance between the pri-
sponding variations in the reluctance of an inter- mary and secondary. It is used in certain an-
nal magnetic circuit. tenna-coupling applications.
variable-reluctance pickup A phonograph pick- variolosser A variable attenuator.
up in which the stylus causes an armature to vi- variometer A continuously variable inductor con-
brate in a magnetic field, and consequently the sisting of two coils connected in series or parallel
reluctance of the magnetic circuit varies in sym- and mounted concentrically”one rotating inside
pathy with the audio frequency. the other. Inductance is maximum when the coils
variable-reluctance transducer A transducer in are perpendicular to each other, and minimum
which the monitored quantity causes the reluc- when they are parallel.
tance of an internal magnetic circuit to vary pro- varioplex A time-sharing method of transmitting
portionately. and receiving wire telegraph signals. It allows the
variable-resistance pickup A phonograph pickup optimum usage of available lines.
in which the vibration of the stylus causes the re- varistor See VOLTAGE-DEPENDENT RESISTOR.
sistance of an internal resistive element to vary in Varley-loop bridge A four-arm, direct-current
sympathy with the sound frequency. bridge circuit in which one of the arms, a two-
variable-resistance transducer A transducer in wire line, is accidentally grounded at a distant
which a monitored quantity causes the resistance point. By adjustment of the bridge, the resulting
of an internal resistive element to vary propor- resistance indicates the distance to the fault.
tionately.
variable-resistance tuning Tuning of a selective
resistance-capacitance (RC) circuit, such as a
Wien bridge or parallel-tee network, by varying Line A
Lines tied
one or more of its resistance arms.
together
variable resistor A resistor whose value can be
for test
varied either continuously or in steps. Also see
POTENTIOMETER and RHEOSTAT. Line B
variable selectivity In a circuit or device, selec-
Accidental
tivity that is adjustable. Example: a variable- ground
selectivity intermediate-frequency (IF) amplifier.
variable-speed motor Any motor whose speed is
Varley loop bridge
adjustable, smoothly or in steps, under load.
variable transformer A transformer (often an au-
totransformer) whose output voltage is adjustable VAR meter An instrument for measuring the ap-
from zero (or some minimum value) to maximum. parent (VAR) power in a reactive circuit.
For this purpose, one winding (usually the sec- varnished cambric Cotton or linen fabric in
ondary in a two-winding transformer) can have a sheets, tape or tubes, that has been varnish-
number of taps. Smooth variation can be pro- impregnated and baked. A common form of this
vided by a wiper arm that slides over the turns of insulating material, the slender tubing known as
the winding. spaghetti, has largely been replaced by plastic
variable-width wound record In photographic tubing.
sound-on-film recording, a sound track made by varnished-cambric tubing Slender tubes of var-
varying the width of the track in sympathy with nished cambric slipped over bare wires and bus-
the sound variations. Compare VARIABLE- bars to insulate them. Also called spaghetti.
DENSITY SOUND RECORD. VATE Abbreviation of VERSATILE AUTOMATIC
Variac See VARIABLE TRANSFORMER. TEST EQUIPMENT.
720 VB • vector power factor


VB Symbol for BASE VOLTAGE of a bipolar transis- rically by constructing a parallelogram from the
tor. vectors, corresponding to the two known sides, as
VBB Symbol for base-voltage supply for a bipolar determined by the vectors. The sum is the vector
transistor. originating at the point where the two vectors
V beam system See VEE BEAM SYSTEM. originate, and extending the diagonal of the
VC Symbol for COLLECTOR VOLTAGE of a bipolar parallelogram.
transistor.
VCA Abbreviation of VOLTAGE-CONTROLLED AM-
y
PLIFIER.
(x1 x2, y1 y2)
VCC Symbol for collector-voltage supply of a bipolar
(x1, y1)
transistor.
VCCO Abbreviation of VOLTAGE-CONTROLLED
CRYSTAL OSCILLATOR. (Also, lowercase.)
VCD Abbreviation of VARIABLE-CAPACITANCE
DIODE.
VCG Abbreviation of VOLTAGE-CONTROLLED (x2, y2)
GENERATOR. x
VCO Abbreviation of VOLTAGE-CONTROLLED OS-
CILLATOR.
V connection of transformers See VEE CONNEC-
TION OF TRANSFORMERS.
VCR Abbreviation of VIDEO CASSETTE RE-
CORDER.
VCSR Abbreviation of voltage-controlled shift regis-
ter.
vector addition
V-cut crystal See VEE-CUT CRYSTAL.
VCXO Abbreviation of VOLTAGE-CONTROLLED
CRYSTAL OSCILLATOR. (Also, lowercase.) vector admittance The reciprocal of VECTOR
VD 1. Abbreviation of VOLTAGE DROP. 2. Abbrevi- IMPEDANCE.
ation of vapor density. vector cardiograph An electrocardiograph that in-
VD Symbol for drain voltage of a field-effect transis- dicates the magnitude and the direction of a
tor. heart signal.
Vdc Symbol for DC VOLTS. vector components 1. The Cartesian coordinates
VDU Abbreviation of VISUAL DISPLAY UNIT. of a vector, or its component angle and radius
vdcw Symbol for DC WORKING VOLTAGE. (Also, (polar coordinates). 2. Quantities that can be rep-
dcwv.) resented by means of vectors (e.g., impedance
VDIG Abbreviation of VIDEO DIGITIZER. and velocity).
VDR 1. Abbreviation of VOLTAGE-DEPENDENT vector diagram A graphical representation of vec-
RESISTOR. 2. Abbreviation of VIDEODISC tor quantities.
RECORDER. vector function A function having both magnitude
Vdrive Abbreviation for DRIVING VOLTAGE or OUT- and direction. Also see VECTOR; VECTOR COM-
PUT VOLTAGE. PONENTS, 2; and VECTOR QUANTITY.
VE Abbreviation of value engineering. vector generator A device that graphically illus-
VE Symbol for EMITTER VOLTAGE of a bipolar trates vectors.
transistor. vectorial angle 1. The angle between a vector and
vectograph A graphic three-dimensional represen- the horizontal axis. 2. The angle between two vec-
tation of a scene composed of superimposed im- tors.
ages photographed through polarizing filters of vector impedance Complex impedance (i.e., an
different orientation, and reconstructed by a sim- impedance of the form R + jX, where R is resis-
ilar viewing technique. tance, X is reactance, and j is an operator indi-
vector 1. A quantity having direction (in two or cating that the reactance is 90 degrees out of
three dimensions) and magnitude. 2. A graphical phase, relative to the resistance).
representation of a quantity, as defined in 1. It vector-mode display On a cathode-ray-tube dis-
consists of a straight arrow indicating the direc- play, the data representation in which points on
tion, and whose length is proportional to the the screen are connected by straight lines.
vector power The vector quantity (Pa2 + Px2)1/2,
magnitude.
vector addition The summation of two vectors, de- where Pa is the active power and Px is the reactive
termined by adding their corresponding compo- power.
vector power factor The ratio Pa/(Pa2 + Px2)1/2,
nent values. In two dimensions, for example,
suppose A = (x1,y1) and B = (x2,y2). Then A + B = where Pa is the active power and Px is the reactive
[(x1 + x2),(y1 + y2)]. The sum can be found geomet- power. In sine-wave situations, this ratio (of
721
vector power factor • velocity modulation


active power to vector power) produces a figure velocity Symbol, v. Abbreviation, vel. Unit, dis-
identical to the conventional power factor. tance per unit time [e.g., meters per second
vector quantity A quantity having both magni- (m/s)]. 1. The change in the position of a body
tude and direction, and that can, therefore, be over a specified period of time. 2. The derivative of
represented by a vector. displacement with respect to time. Compare AC-
vectorscope A special oscilloscope for visual ad- CELERATION.
justment of a color-television receiver by means velocity constant See VELOCITY FACTOR.
of a color-phase diagram. velocity error For a servomechanism in which the
vector sum The resultant of two nonparallel vec- input and output shafts rotate at the same speed,
tors; therefore, the resultant of the forces or the angular displacement between them.
quantities represented by them. For example, re- velocity factor Abbreviation, v. For a transmission
actance and resistance can be represented by two line, the ratio of the speed of electromagnetic
perpendicular vectors. wave propagation in the line to the speed of elec-
vector voltmeter A voltmeter that indicates the tromagnetic waves in a vacuum (299,792 kilome-
phase as well as the amplitude of an alternating- ters per second). It can be expressed as a number
current voltage. between 0 and 1, or as a percentage between 0
VEE Symbol for emitter-voltage supply of a bipolar and 100. In practical feed lines, v ranges from
transistor. about 0.66 (for coaxial line with a solid polyethy-
vee antenna A center-fed antenna in which the lene dielectric) to about 0.95 (for open-wire line
two halves of the radiator form an angle consider- with widely separated spacers).
ably less than 180 degrees. velocity hydrophone A hydrophone whose out-
vee-beam system An elevation-measuring radar put, like that of the velocity microphone, is pro-
system in which fan-shaped vertical and inclined portional to the instantaneous particle velocity in
beams, intersecting at ground and rotating con- the sound wave impinging on the device.
tinuously around the vertical axis, are radiated velocity-lag error A lag (proportional to the input-
by one antenna. Target elevation is determined variation rate) between the input and output of a
from the interval between successive echoes from device, such as a servomechanism.
the target. velocity level For a sound, the ratio v0, expressed
vee connection of transformers In a three-phase in decibels:
system, a method of connecting two transformers
v0 = 20 log10(vs/vr)
so that the line current and voltage equal the
phase current and voltage. Also called open-delta where vs is the particle velocity of the sound, and
connection. vr is a reference particle velocity.
vee-cut crystal A piezoelectric plate cut from a velocity microphone A microphone in which the
quartz crystal so that its faces are not parallel to vibratory element is a thin, aluminum or Duralu-
the x, y, or z axis of the crystal. Also see CRYSTAL min ribbon suspended loosely between the poles
AXES and CRYSTAL CUTS. of a strong permanent magnet. Vibration of the
vee particle A short-lived elementary particle that corrugated ribbon in the magnetic field causes an
results when high-energy neutrons or protons audio-frequency voltage to be induced across the
collide with nuclei. The particle can be positive, ribbon. The microphone is so called because its
negative, or neutral, and gets its name from its output is proportional to the instantaneous parti-
cloud-chamber track. cle velocity in the sound wave impinging on the
vee signal In radiotelegraphy, the letter V (di-di-di- ribbon. Also called ribbon microphone.
dah) transmitted as a test signal, usually three velocity-modulated amplifier A circuit in which
times in rapid succession. It is used during on- radio-frequency amplification is obtained by ve-
the-air transmitter tests, followed by the station™s locity modulation.
call letters. velocity-modulated oscillator A vacuum-tube
vehicle An inert substance, usually a liquid, that device in which an electron stream is velocity-
acts as a solvent, carrier, or binder for some modulated (see VELOCITY MODULATION) as it
other, more active substance. Thus, shellac can passes through a resonant cavity (the buncher);
be the vehicle for the metallic powder in a silver the subsequent energy, of a higher intensity, is
paint used in silk-screening electronic circuits. extracted from the bunched stream as it passes
vehicle smog-control device See COMPUTER- through another resonant cavity (the catcher).
CONTROLLED CATALYTIC CONVERTER and Feedback from catcher to buncher sustains oscil-
EXHAUST ANALYZER. lations. See, for example, KLYSTRON OSCILLATOR.
vel Abbreviation of VELOCITY. velocity-modulated tube A vacuum tube utilizing
velocimeter 1. An instrument for measuring the velocity modulation. See, for example, KLYSTRON.
velocity of sound in various materials. 2. An velocity modulation The process in which the in-
electronic velocity meter”especially a radial- put signal of a vacuum tube varies the velocity of
velocity meter using Doppler radar. 3. An elec- the electrons in a constant-current electron beam
tronic flow meter. in sympathy with the input signal.
722 velocity resonance • versatile automatic test equipment


velocity resonance A state of resonance in which vented-baffle loudspeaker See ACOUSTICAL
a 90-degree phase difference is between the fun- PHASE INVERTER and BASS-REFLEX LOUD-
damental frequency of oscillation of a system and SPEAKER.
the fundamental frequency of the applied signal. vent mount A metal bracket for fastening an an-
velocity sorting Selecting and separating elec- tenna mast to a (plumbing) vent pipe on a roof.
trons, according to their velocity. ventricular fibrillation See FIBRILLATION.
velocity spectrograph A device that uses electric verification 1. The process of ensuring that two
or magnetic deflection to separate charged parti- sets of data are identical. 2. The process of vali-
cles into various streams, according to their ve- dating (see VALIDATE).
locity. vernier 1. An auxiliary scale along which a regu-
velocity variation See VELOCITY MODULATION. lar, linear scale (such as that of a tuning dial)
velocity-variation amplifier See VELOCITY- slides. The vernier scale is graduated so that
MODULATED AMPLIFIER. when the main scale is set to an unmarked point
velocity-variation oscillator See VELOCITY- between two of its graduations, and the “0” point
MODULATED OSCILLATOR. on the vernier scale is used as the index, “1” on
velometer An instrument used to measure the ve- the vernier scale will exactly coincide with “1” on
locity of air (e.g., to determine wind speed). the main scale. The corresponding number on the
venetian-blind effect A television-display mal- vernier scale indicates the exact number of sub-
function in which the picture seems to appear divisions between two points on the main scale.
through horizontal slits. Vernier arrangements are provided with the dials
Venn diagram A method of illustrating the rela- of some precision analog instruments. 2. See
tionship among various subsets within a speci- VERNIER CAPACITOR. 3. See VERNIER DIAL.
fied universal set. The subsets are shown as 4. See VERNIER RESISTOR.
geometric figures, usually circles.

Main
Universal set reading
line
Aux. scale
w1

w2 1234 5
67
x 8
y 9
80
y3
x1 70
y4 Reading is
somewhere Aux. scale lines up at 3,
y1
x4
x2 between indicating 75.3
y5 75 and 76
y2
x5
x3 y6
vernier, 1
z1 z2

vernier capacitor A low-capacitance variable ca-
w3
z
pacitor connected in parallel with a higher-capac-
itance fixed or variable capacitor for precise
adjustment of the total capacitance.
vernier dial 1. A slow moving dial for fine tuning
Venn diagram
an adjustable device. The required reduction ra-
tio is obtained with gears, friction wheels, or a
vent 1. An opening in an equipment enclosure for belt-and-pulley combination. 2. A dial provided
the entry of cool air or the escape of warm air. with an accessory vernier scale.
2. In an electrolytic capacitor, a lightly covered vernier resistor A low-resistance variable resistor
blowout hole for the relief of gas pressure in the connected in series with a higher-resistance fixed
event of severe overload. 3. A small opening for or variable resistor to precisely adjust the total re-
relieving gas pressure in an automobile battery. sistance.
4. In a loudspeaker enclosure, such as the bass- vernier rheostat See VERNIER RESISTOR.
reflex type, an auxiliary opening that extends the vers Abbreviation of VERSED SINE.
low-frequency range of the speaker. versatile automatic test equipment Abbrevia-
vented baffle A loudspeaker enclosure having the tion, VATE. For troubleshooting the electronic
proper auxiliary opening(s) for coupling the systems of missiles, a computer-controlled tester
speaker to the surrounding air. that isolates faults through logical operations.
723
versed sine • vertical frequency response


versed sine Abbreviation, vers. A trigonometric the electromagnetic field for the vertical deflection
function equal to the difference between the co- of the electron beam. Compare HORIZONTAL DE-
sine of an angle and one; vers x = 1 “ cos x. FLECTION COILS.
vert Abbreviation of VERTICAL. vertical deflection electrodes See VERTICAL DE-
vertex 1. The terminal point at which two or more FLECTION COILS and VERTICAL DEFLECTION
branches of a network meet. Also see NODE, 1. PLATES.
2. The point of intersection of two lines that form vertical deflection plates In an oscilloscope (and
an angle. in some early television picture tubes), a pair of
vertex plate In the reflector of a microwave an- plates that provides the electrostatic field for ver-
tenna, a matching plate mounted at the vertex. tical deflection. Compare HORIZONTAL DEFLEC-
vertical 1. The direction indicated by a line per- TION PLATES.
pendicular to the plane of the horizon (e.g., a ver- vertical dipole An antenna consisting of a
tical axis). 2. In the 45-45 recording process, the straight, center-fed, half-wave conductor oriented
signal resulting from sound that arrives simulta- vertically.
neously and 180 degrees out of phase at the two
microphones and causes up-and-down move-
ment of the cutting stylus.
vertical amplification Gain provided by the verti-
cal channel of a device, such as an oscilloscope,
cathode-ray electrocardiograph, or television re-
ceiver. Compare HORIZONTAL AMPLIFICATION.
vertical amplifier The circuit or device that pro-
vides gain in the vertical channel of a device.
Compare HORIZONTAL AMPLIFIER.
vertical-amplitude control 1. See VERTICAL-
GAIN CONTROL. 2. In a color television receiver,
one of the three controls by which the amplitude
of the parabolic voltages applied to the coils of the 1/2-wave
magnetic-convergence assembly are adjusted.
radiating Feed line
vertical angle of radiation The angle, with respect element
to the plane of the horizon, at which radio-
frequency energy is propagated from a transmitting
antenna.
vertical antenna 1. An antenna that consists es-
sentially of a single, straight, vertical conductor.
2. An antenna that is mounted vertically, instead
of horizontally.
vertical blanking See VERTICAL RETRACE
BLANKING.
vertical-blanking pulse In a television signal, the
pulse at the end of each field that accomplishes
vertical retrace blanking. Compare HORIZON-
TAL-BLANKING PULSE.
vertical-centering control See CENTERING CON- vertical dipole
TROL.
vertical channel The system of amplifiers, controls,
and terminations that constitutes the path of the vertical dynamic convergence During the scan-
vertical signal applied to a device, such as an os- ning of points along a vertical line through the
cilloscope. Compare HORIZONTAL CHANNEL. center of a color-television picture tube, the con-
vertical compliance In disc sound reproduction, vergence of the electron beams at the aperture
the ease with which the stylus can move vertically mask. Compare HORIZONTAL DYNAMIC CON-
while it is in position on the disc. VERGENCE.
vertical coordinates See CARTESIAN COORDI- vertical field strength The field strength of signals
NATES. in a vertical plane passing through an antenna.
vertical deflection 1. In an oscilloscope or televi- Compare HORIZONTAL FIELD STRENGTH.
sion receiver, the movement of the spot up and vertical-field-strength diagram A plot of vertical
down on the screen. Compare HORIZONTAL DE- field strength.
FLECTION. 2. In a direct-writing recorder, up or vertical frequency response The gain-frequency
down deflection of the pen. characteristic of the vertical channel of an instru-
vertical deflection coils In a cathode-ray tube, ment, such as an oscilloscope. Compare HORI-
the pair of coils in a deflection yoke that provides ZONTAL FREQUENCY RESPONSE.
724 vertical gain • vertical sweep rate


vertical gain The overall amplification (gain) pro- vertical quantity The quantity measured along
vided by the vertical channel of an instrument, the y-axis of a graph, or represented by the verti-
such as an oscilloscope, graphical recorder, or cal deflection of an electron beam. Compare
television receiver. Compare HORIZONTAL GAIN. HORIZONTAL QUANTITY.
vertical-gain control A control, such as a poten- vertical radiator See VERTICAL ANTENNA.
tiometer, for adjusting vertical amplification. vertical recording Disc recording in which the
Compare HORIZONTAL-GAIN CONTROL. depth of the groove is varied in sympathy with the
vertical-hold control In a television receiver, the sound. Also called HILL-AND-DALE RECORD-
control for adjusting the frequency of the vertical ING. Compare LATERAL RECORDING.
oscillator so that the picture can be locked to pre- vertical redundance In computer operation, the
vent vertical roll. Compare HORIZONTAL-HOLD error state when a character has an odd number
CONTROL. of bits in an even-parity system, or vice versa.
vertical-incidence transmission Transmission of vertical resolution The number of horizontal
a wave vertically to the ionosphere and the sub- wedge-lines that can be easily seen in a television
sequent reflection of the wave to the earth. test pattern before they blend. Compare HORI-
vertical-lateral recording In stereophonic disc ZONTAL RESOLUTION.
recording, the recording of one signal vertically vertical retrace In a cathode-ray device, such as an
(see VERTICAL RECORDING) and the other later- oscilloscope or television receiver, the rapid return
ally (see LATERAL RECORDING). of the beam to its starting point at the top of the
vertical linearity Linearity of response (gain and screen after completely traversing the screen from
deflection) of the vertical channel of an oscillo- top to bottom. Compare HORIZONTAL RETRACE.
scope or television receiver. A linear picture is vertical retrace blanking In a television receiver,
neither contracted nor expanded vertically in any the automatic shutoff of the electron beam during
part of the screen. Compare HORIZONTAL LIN- a vertical retrace period, to prevent an extraneous
EARITY. line being traced on the screen during this period.
vertical-linearity control In an oscilloscope or Also see BLACKOUT, 2; BLANKING INTERVAL,
television receiver, the control whereby vertical 1, 2; BLANKING PEDESTAL; BLANKING
linearity is adjusted. Compare HORIZONTAL- TIME; VERTICAL RETRACE; and VERTICAL
LINEARITY CONTROL. RETRACE PERIOD. Compare HORIZONTAL RE-
vertically polarized wave An electromagnetic TRACE BLANKING.
wave whose electric lines of flux are perpendicu- vertical retrace period In a television receiver, the
lar to the plane of the horizon. Compare HORI- interval during which the spot returns from the
ZONTALLY POLARIZED WAVE. bottom to the top of the screen after having traced
vertical-metal-oxide semiconductor field-effect all horizontal lines from top to bottom. Compare
transistor Abbreviation, VMOSFET. A metal- HORIZONTAL RETRACE PERIOD.
oxide semiconductor field-effect transistor fabri- vertical sensitivity The signal voltage required at
cated so that the current flow within the device is the input of a vertical channel to produce full ver-
vertical, instead of the usual horizontal, affording tical deflection. Also see VERTICAL GAIN. Com-
several advantages over the conventional MOS- pare HORIZONTAL SENSITIVITY.
FET. vertical signal A signal serving as a vertical quan-
vertical oscillator In a television receiver, the os- tity (e.g., one that deflects the beam in a cathode-
cillator that generates the vertical sweep signal. ray tube upward and/or downward). Compare
Compare HORIZONTAL OSCILLATOR. HORIZONTAL SIGNAL.
vertical-output regulator In a television receiver, vertical-speed transducer A transducer whose
a voltage-dependent resistor used to stabilize the electrical output is proportional to the vertical
sweep voltage across the horizontal deflection speed of an aircraft or missile carrying the trans-
coils”especially during warmup. ducer.
vertical output stage In a television receiver, an vertical stylus force In disc sound reproduction,
output amplifier following the vertical oscillator. the downward force (in grams or ounces) that the
Compare HORIZONTAL OUTPUT STAGE. stylus exerts on the disc.
vertical polarization Pertaining to an electromag- vertical sweep 1. In a cathode-ray tube, especially
netic wave whose electric lines of flux are perpen- a television picture tube, the movement of the
dicular to the plane of the horizon. In general, spot up or down on the screen. Compare HORI-
when the radiating element of an antenna is ver- ZONTAL SWEEP. 2. The circuit that produces
tical, the electric lines of flux in the transmitted this sweep.
waves are vertical, and the antenna is most sen- vertical sweep frequency The frequency at which
sitive to incoming signals whose electric lines of vertical sweep occurs. In a television receiver, it is
flux are vertical. Compare HORIZONTAL POLAR- 60 Hz. Also called vertical sweep rate. Compare
IZATION. HORIZONTAL SWEEP FREQUENCY.
vertical positioning control See CENTERING vertical sweep rate See VERTICAL SWEEP FRE-
CONTROL. QUENCY.
725
vertical synchronization • VHF oscillator


Carrier
vertical synchronization In a television receiver,
synchronization of the vertical component of
scanning with that of the camera. Also see VER-
TICAL SYNC PULSE. Compare HORIZONTAL
SYNCHRONIZATION.
vertical sync pulse In a video signal, the pulse
that synchronizes the vertical component of
scanning in a television receiver with that of the
Vestigial
Working
camera, and that triggers vertical retrace and
sideband
sideband
blanking. Compare HORIZONTAL SYNC PULSE.
vertical wave See VERTICALLY POLARIZED
WAVE.
vertical width control See WIDTH CONTROL, 1,
2. fo
very high frequency Abbreviation, VHF. Radio Frequency
frequencies in the range 30 MHz to 300 MHz,
corresponding to free-space wavelengths of 10
vestigial sideband, 2
meters to 1 meter. It is sometimes divided into
VHF low band (30 MHz to 50 MHz) and VHF high
band (50 MHz to 300 MHz). Also see RADIO tude-modulated signal in which one sideband
SPECTRUM, 1. has been partially or largely suppressed. 3. The
very high resistance Abbreviation, VHR. Large small amount of energy emitted in the unused
values of resistance; usually expressed in meg- sideband in a single-sideband transmitter.
ohms, gigohms, or teraohms. vestigial-sideband filter A filter operated between
very-high-resistance voltmeter Abbreviation, an amplitude-modulated transmitter and an an-
VHRVM. A voltmeter using a low-range microam- tenna to obtain a vestigial-sideband signal.
meter or picoammeter and a very high value of vestigial-sideband signal An amplitude-modu-
multiplier resistance (see VOLTMETER MULTI- lated signal in which one of the sidebands has
PLIER). been partially suppressed.
very-high-speed integrated circuit An integrated vestigial-sideband transmission Transmission of
circuit used for switching or other digital func- a signal containing a vestigial sideband. In televi-
tions at thousands, millions, or billions of sion, for example, the upper sideband is trans-
changes of state per second. mitted fully, while the lower sideband is almost
very-large-scale integration Abbreviation, VLSI. completely suppressed. The lower sideband is,
The inclusion of several complete systems, such therefore, a vestigial sideband.
as computers, on a single integrated-circuit chip. vestigial-sideband transmitter An amplitude-
This can extend several orders of magnitude be- modulated transmitter equipped with the filters
yond large-scale integration (LSI). or other subcircuits necessary for emitting a ves-
very long range Abbreviation, VLR. Pertaining to tigial-sideband signal.
ground radar sets having a maximum slant range VF Abbreviation of VIDEO FREQUENCY.
of over 250 miles. Compare VERY SHORT VFB Abbreviation for feedback voltage in an inte-
RANGE. grated circuit device. The term applies especially
very low frequency Abbreviation VLF. A radio fre- to operational amplifiers.
quency in the range 10 kHz to 30 kHz, corre- VFO Abbreviation of VARIABLE-FREQUENCY OS-
sponding to wavelengths between 30 kilometers CILLATOR.
and 10 kilometers. Also see RADIO SPECTRUM, Vg Abbreviation of GENERATOR VOLTAGE. (Also,
1. Eg.)
very low resistance Abbreviation, VLR. Values of VGA Abbreviation of VARIABLE-GAIN AMPLIFIER.
resistance less than 1 ohm, usually expressed in VGD Symbol for GATE-DRAIN VOLTAGE of a field-
milliohms or microhms. effect transistor.
very short range Abbreviation, VSR. Pertaining to VGS Symbol for GATE-SOURCE VOLTAGE of a
ground radar sets having a maximum slant range field-effect transistor.
of less than 25 miles. Compare VERY LONG VHF Abbreviation of VERY HIGH FREQUENCY.
RANGE. VHF high band See VERY HIGH FREQUENCY.
vestigial 1. An effect that remains as a by-product, VHF low band See VERY HIGH FREQUENCY.
but that serves no directly applicable purpose. VHF omnirange Abbreviation, VOR. A very-high-
See, for example, VESTIGIAL SIDEBAND. 2. Un- frequency radionavigation system that provides
necessary; extraneous. radial lines of position.
vestigial sideband 1. A portion of one sideband in VHF oscillator A radio-frequency oscillator spe-
an amplitude-modulated signal, remaining after cially designed to operate in the range 30 MHz to
passage through a selective filter. 2. An ampli- 300 MHz.
726 VHF receiver • vibrocardiography


VHF receiver 1. A radio receiver specially designed vibrating-wire oscillator An oscillator similar to
to operate in the range of 30 MHz to 300 MHz. the vibrating-reed oscillator, but using a wire, in-
2. A television receiver for the VHF channels (see stead of a reed.
VHF TELEVISION CHANNELS). vibrating-wire transducer A transducer in which
VHF television channels Twelve 6-MHz-wide the fluctuating tension of a thin wire suspended
channels (television channels 2 through 13) be- in a magnetic field frequency-modulates the oper-
tween 54 and 216 MHz. ating voltage.
vibration 1. The changing of the position or di-
mensions of a body back and forth, usually at a
Channel Frequency (MHz)
rapid rate, an action seen in the repetitive move-
2 54.0 “ 60.0
ment of a musical string, headphone diaphragm,
3 60.0 “ 66.0
loudspeaker cone, loose machine, etc. 2. See OS-
4 66.0 “ 72.0
CILLATION.
5 76.0 “ 82.0
vibration analyzer See VIBRATION METER.
6 82.0 “ 88.0
vibration calibrator A device that generates a
7 174 “ 180
standard vibration, usually at a fixed frequency,
8 180 “ 186
for calibrating vibration meters, pickups, trans-
9 186 “ 192
ducers, etc.
10 192 “ 198




Y
vibration galvanometer A type of alternating-
11 198 “ 204
current galvanometer. The natural frequency of
12 204 “ 210




FL
the movable element of the instrument is made
13 210 “ 216
equal to that of the alternating current under
test, to obtain a reading.
VHF television channels vibration isolator In an electronic-equipment as-
AM
(United States) sembly, a cushioning support that protects the
equipment from vibration.
VHF transmitter A radio or television transmitter vibration machine See VIBRATOR, 2.
specially designed to operate in the range 30 MHz vibration meter An instrument for measuring the
to 300 MHz. amplitude and frequency of vibration (see VIBRA-
TE

VHR Abbreviation of VERY HIGH RESISTANCE. TION, 1). It consists essentially of a vibration
VHRVM Abbreviation of VERY-HIGH-RESISTANCE pickup followed by a selective amplifier and an in-
VOLTMETER. dicating voltmeter graduated in vibration units.
VHS videocassette recorder A popular scheme for vibration pickup A transducer that senses me-
videocassette recording, used in millions of chanical vibration and converts it into a propor-
households in the United States alone. Typical tionate output voltage, or changes resistance in
VHS cassette play times range from about two sympathy with the vibration.
hours to more than eight hours. vibrato In electronic musical instruments, a cir-
VHSIC Abbreviation for VERY HIGH SPEED INTE- cuit or device that modulates a note by varying its
GRATED CIRCUIT. frequency, amplitude, or both, at an extremely
VI 1. Abbreviation of VOLUME INDICATOR. 2. Ab- low frequency (a few hertz).
breviation of VISCOSITY INDEX. vibrator 1. See INTERRUPTER. 2. See VIBRATING-
Vi Symbol for INPUT VOLTAGE. (Also, Vin.) REED RELAY. 3. A device for shaking something
vibrating bell A bell with a striking mechanism under test at selected frequencies and amplitudes.
that oscillates, causing a continuous ringing vibrator-type power supply A battery-operated,
sound. high-voltage power supply in which one vibrator
vibrating-reed frequency meter See POWER- (see INTERRUPTER) makes and breaks direct
FREQUENCY METER, 2. current flowing from the battery into the primary
vibrating-reed oscillator An audio-frequency os- winding of a step-up transformer, and another vi-
cillator in which an iron, steel, or alloy reed vi- brator rectifies the high voltage delivered by the
brating in a magnetic field acts like a tuning fork secondary winding.
to control the oscillation frequency. vibrator-type rectifier A vibrator (see INTER-
vibrating-reed relay An electromechanical relay in RUPTER) that connects one terminal of the sec-
which the movable contact is carried by the end ondary winding of a transformer to an output
of a thin, metal strip (reed) of iron or magnetic al- terminal each time that terminal is positive.
loy. The strip is supported within the magnetic When the negative half-cycle appears at the
field of a coil carrying an alternating control cur- transformer terminal, the vibrator is open. In this
rent; when the frequency of this current corre- way, the alternating-current output of the trans-
sponds to the natural (resonant) frequency of the former is rectified.
reed, it vibrates vigorously enough to close the vibrocardiography A method of monitoring and
contacts. Such a relay, consequently, is fre- recording the movement of the chest cavity as a
quency selective. result of the beating of the heart.




Team-Fly®
727
vibrograph • video IF amplifier


video correlator A device used with radar to locate
T
and identify a target with high precision.
video detector In a television receiver, the demod-
C3
B RFC 1 RFC 2 ulator for the video signal. This detector follows
Vibrator
the video intermediate-frequency amplifier and
+ precedes the video amplifier. It usually embodies
C2 dc output a relatively simple, wideband diode circuit.
C1
_
Driver coil Peaking
Video coil
_ det.diode
Output
vibrator-type power supply R1
Last IF amp Peaking
+ coil
l
vibrograph A device for observing and recording vi-
bration.
vibrometer See VIBRATION METER.
vibroscope An instrument for observing (and R2
detector
sometimes recording) vibration. C1
load
Victor Phonetic alphabet communications code
word for the letter V.
Victron A brand of polystyrene, a low-loss plastic
B+
insulant that is especially useful at high radio fre-
quencies.
video detector
video 1. Pertaining to television”especially to its
picture circuitry or to circuits and devices related
to television, but used for other purposes. 2. The Video Digitizer Abbreviation, VDIG. A program
picture portion of a television broadcast, as op- developed for multimedia video in personal com-
posed to the sound (audio) portion. 3. Some- puter systems.
times, a cathode-ray-tube terminal or display. videodisc A flat magnetic or optical disc on which
4. Generally, television in adjective sense (e.g., audio-visual programs are recorded, and from
video play). 5. The images on a computer display which they can be played back into a television
or monitor. receiver or multimedia personal computer.
video amplifier 1. In television, the wideband videodisc recorder Abbreviation, VDR. A machine
stage (or stages) that amplifies the picture signal for recording television programs on discs compa-
and presents it to the picture tube. 2. A similar rable to those used for sound or data recording.
wideband amplifier, such as an instrument am- video discrimination In radar, the use of a circuit
plifier or preamplifier having at least a 4-MHz or device to decrease the width of the video-
bandwidth. amplifier passband.
video animation Movement of graphic images on a video frequency 1. Pertaining to signals in the wide
cathode-ray-tube display by the use of computer- passband of a video amplifier: 30 Hz to 4 MHz.
manipulation through special software, under 2. Pertaining to a device capable of operating over
the direction of an operator using a keyboard, the wide passband of a video amplifier (e.g., a
joystick, or digitizer. video-frequency alternating-current voltmeter).
video buffer A unity-gain circuit that minimizes video-frequency amplifier An amplifier capable of
loading effects caused by having several video handling signals of a wide frequency range (e.g.,
multiplexer inputs connected to the same signal direct current to 4 MHz). Also see VIDEO FRE-
source. QUENCY, 1.
video carrier The television carrier amplitude- video gain control In a television receiver, a gain
modulated by the picture information, synchro- control for adjusting the video signal amplitude.
nization pulses, and blanking pulses. In a color-television receiver, a pair of these con-
videocassette recorder Abbreviation, VCR. A trols permits adjustment of the three color sig-
machine for recording television programs on nals to the proper amplitude ratio.
magnetic-tape cassettes (see CASSETTE, 1). video game A game, such as football, basketball,
videocast 1. Television broadcast. Also called slot machine, tic-tac-toe, etc., played on the
TELECAST. 2. To make a television broadcast. screen of a television receiver or on a computer.
videocaster See TELECASTER. videogenic Suitable for television.
video CD-ROM A digital optical VIDEODISC, re- video IF amplifier In a television receiver, the
sembling an audio or computer compact disc. A broadband intermediate-frequency (IF) amplifier
typical disc can store more than an hour™s worth of the video signal. In modern receivers, this IF
of conventional television programming. amplifier also handles the sound signal.
728 video mapping • vinyl


video mapping A system of surveillance or map- videotape recording 1. Abbreviation, VTR. The
ping in which, for reference, the outlines of the technique of recording video signals on magnetic
area being surveyed are superimposed electroni- tape. Also see VIDEO RECORDING, 1, 2 and
cally on the radar display of the area. VIDEOTAPE. 2. A tape on which a video signal
video masking A form of radar signal processing has been recorded.
in which ground clutter and other unwanted videotext A system that allows television viewers
echoes are removed, making the desired targets to dial up special material, such as stock market
more readily visible. quotations, weather data, sports scores, etc.
video mixer A circuit or device for mixing the sig- vidicon A television camera tube in which the elec-
nals from two or more television cameras. tron beam scans a charged-density pattern that
video modulation In television transmission, am- has been formed and stored on the surface of the
plitude modulation of the carrier wave with photoconductor. It is commonly used in cam-
pulses and waves corresponding to the picture el- corders, closed-circuit television systems, and
ements. robot vision systems. Its assets include compact-
video on demand Television service in which sub- ness and sensitivity.
scribers can choose the programs they want to viewfinder An accessory or integral device in
watch, and also the specific times for viewing. which an image (formed optically or electroni-
video random-access memory Abbreviation, cally) corresponds to the image viewed by the
VRAM. In computer systems, RANDOM-ACCESS camera with which it is used.
MEMORY used primarily for enhancing the per- viewing mesh In a cathode-ray storage tube, the
formance of the display. mesh on which the image is presented for viewing
video recording 1. Recording wideband material by the operator. Also see CHARGE-STORAGE
(such as a video signal) on a tape or disc. 2. The TUBE.
recording made of a telecast. Also see VIDEO- viewing mirror In an oscilloscope-camera assembly,
TAPE RECORDER. a flat, slant-mounted mirror that reflects the image
video signal 1. In television, the amplitude-modu- on the oscilloscope screen to the viewer™s eye.
lated signal containing picture information and viewing screen In a cathode-ray device, such as
pulses. Also see VIDEO, 2 and VIDEO MODULA- an oscilloscope tube or television picture tube,
TION. 2. Broadly, a telecast signal, including the face on which the image appears.
sound. viewing time In a storage type cathode-ray tube,
the length of time for which the image persists.
viewing window See WINDOW, 2.
Whitest
Villard circuit 1. A voltage-doubler circuit using
signal Black
only one diode and two capacitors. The open-
Dark
} Blacker-than-black
Grey White circuit direct-current output voltage is ap-
grey region
proximately twice the peak value of the
alternating-current input voltage. Also see VOL-
TAGE DOUBLER. 2. See SELECTOJECT.

Zero signal

C1


+ dc
ac D
Erms Edc
Input Output
_
video signal

video stretching In some electronic navigation
C2
systems, increasing the duration of a video pulse.
video synthesizer A computerized device that pro-
duces graphical renditions of objects or circuits Edc = 2.82 Erms
in three dimensions.
videotape 1. A special magnetic tape for video
Villard circuit, 1
recording (see VIDEO RECORDING, 2). 2. To
make a video recording.
videotape recorder Abbreviation, VTR. A wide- Villari effect In certain magnetostrictive materials,
band, magnetic-tape recorder for producing video the change in magnetic induction that accompa-
recordings with a camera, or for making a record nies the application of a mechanical stress in a
of television programs, for subsequent reproduc- given direction. Also see MAGNETOSTRICTION.
tion (playback). vinyl A general name for vinyl copolymer resins.
729
vinylidene chloride • visible spectrum


vinylidene chloride A plastic insulant. Dielectric of a meter by an amount proportional to the
constant, 3 to 5. Dielectric strength, 20 kV/mm. speed of the ball and, consequently, to the viscos-
Vinylite-A A brand of the plastic polyvinyl acetate. ity of the fluid.
Vinylite-Q A brand of the plastic polyvinyl chloride. viscosimeter See VISCOMETER.
vinyl resin A synthetic resin resulting from the viscosity The resistance offered by a fluid (liquid
polymerization of compounds that contain the or gas) to objects passing through it. The viscos-
group CH2 = CH“. ity of pure water is low; that of heavy oil is high.
violation In a security system, a condition that re- Expressed in newton-seconds per meter squared.
sults in the actuation of an alarm. Example: an viscosity index Abbreviation, VI. A number indi-
intruder breaks the light beam in an electric eye. cating how well an oil retains its viscosity with
virgin magnetic material Core or shield material temperature changes; larger indexes are assigned
that has never been magnetized. When virgin ma- to oils that are little influenced by variations in
terial is first subjected to magnetization, the hys- temperature.
teresis loop starts at zero, but never returns to viscous-damped arm A phonograph pickup arm
zero (see BOX-SHAPED LOOP). with an oil dashpot to prevent arm resonance and
virgin neutron Any neutron that has not been in- to slow the descent of the arm to the disc.
volved in a collision with another particle subse- viscous damping The use of a viscous fluid in the
quent to its initial generation. dashpot of a device (such as a relay, timer, or
virgin record See BLANK RECORD. pickup arm) to provide damping. See, for exam-
virgin tape See BLANK TAPE. ple, DASHPOT RELAY.
virtual address In computer operations, an ad- viscous hysteresis A slow, slight increase in the
dress that must be modified to refer to a location magnetization of a material when the magnetizing
in main memory. field is constant. Compare STATIC HYSTERESIS.
virtual decision value In quantizing or encoding, visibility factor See DISPLAY LOSS.
a method of expressing the maximum input am- visible radiation Electromagnetic radiation that is
plitude. Two values are extrapolated from actual perceptible to the eye. Also see VISIBLE SPEC-
decision values”one at either end of the working TRUM.
range used. visible spectrum The band of electromagnetic
virtual height The altitude that a vertically propa- wavelengths that the human eye perceives as vis-
gated electromagnetic wave would reach before ible light. For most people, this band extends
reflection if its path in the ionosphere were a from approximately 750 nanometers (nm), repre-
straight line. The actual distance at which the senting red light, down to 390 nm, representing
wave penetrates the ionosphere before reflection violet light. The visibility curve peaks in the
is less than the virtual height. yellow-green region at about 560 nm; 1 nm = 0.000
virtual image The image formed when rays from a
scene diverge after passing beyond the focal point
Wavelength
of a convex lens. The scene appears inverted to an
(angstroms)
observer. Compare REAL IMAGE.
virtual memory 1. In a computer system, a means 100 X rays
of using two or more memory stores simultane-
101
ously. 2. Auxiliary memory used in conjunction
with the main, or core, memory.
102 Ultraviolet
virtual ppi reflectoscope A device used to super-
impose a virtual image of a chart or map onto a
103
plan-position indicator (ppi) radar display. Also
see VIDEO MAPPING. Visible light
104
virtual reality Abbreviation, VR. A general term for
any of various high-level computer simulation or
remote-control programs. The user often wears a 105 Infared
head-mounted display that provides vivid, three-
106
dimensional imagery and binaural sound. It can
be used in robotic telepresence systems for preci-
sion remote control. 107



}
virus See COMPUTER VIRUS. EHF
vis 1. Abbreviation of visibility. 2. Abbreviation of 108
visual. SHF Radio waves
viscometer An instrument for measuring viscos- 109
ity. There are several electronic versions of this UHF
1010
device. In one, a steel ball falls through a material
(such as an oil) under test and distorts the mag-
netic field of a pickup coil, causing the deflection visible spectrum
730 visible spectrum • voice frequencies


000 001 meter = 10“9 m. Also see ELECTROMAG- VMOSFET Abbreviation of VERTICAL-METAL-
NETIC THEORY OF LIGHT. OXIDE SEMICONDUCTOR FIELD-EFFECT
vision system A set of devices that allows a ma- TRANSISTOR.
chine (computer or robot) to observe and respond Vo Symbol for OUTPUT VOLTAGE. Also, Vout.
to visual stimuli. Typically, it includes a camera VOA Abbreviation of VOLT-OHM-AMMETER.
[such as a vidicon or charge-coupled device vocabulary In computer-programming operations,
(CCD)], a cable, electromagnetic or fiberoptic link, a list of available operating codes and instruc-
a receiver, and software for interpreting the im- tions for the computer. Also called INSTRUCTION
ages. SET.
visual alignment Optimization of a circuit (such Vocoder A device for reducing speech to frequen-
as a radio receiver) with the aid of meter deflec- cies low enough for efficient transmission
tions, rather than with audible indications. Also through a limited-bandwidth channel. The term
called silent alignment. is a contraction of voice coder.
visual-aural radio range A radio aid to air naviga- Voda In a telephone system that utilizes a radio
tion (characterized by an audible signal, meter link (using the same frequency for transmission
deflection, or both) used by the pilot of an aircraft in both directions) and land-line links, an auto-
to determine if the course is being followed. matic, voice-operated switching system for en-
visual-aural range See VISUAL-AURAL RADIO abling the transmitter and disabling the receiver,
RANGE. and vice versa. The name is an acronym for voice-
visual-aural signal tracer A troubleshooting in- operated device, anti-sing.
strument for following a signal through a circuit Vodacom Contraction of voice data communica-
by sensing it at successive points in the circuit. tions.
The signal strength is indicated by a meter and a Voder An electronic device that synthesizes
loudspeaker. speech. The term is an acronym for voice opera-
visual carrier frequency See VIDEO CARRIER tion demonstrator.
and VIDEO-FREQUENCY, 1. vogad A type of automatic gain control for audio
visual communication 1. Transmission and re- amplifiers and modulators. In a radio transmit-
ception of signals by visible-light means, such as ter, it maintains 100% modulation of the car-
modulated beams of flashing lights. 2. Transmis- rier”even when the speaker™s voice level varies
sion and reception of messages by direct visual widely. The name is an acronym for voice-
observation, such as signal lights. operated gain adjusting device.
visual display unit Abbreviation, VDU. 1. A com- voice actuation See VOICE-OPERATED CON-
puter peripheral consisting of a cathode-ray tube, TROL.
a keyboard, and often a pointing device. 2. A voice analyzer A circuit that evaluates the charac-
dumb terminal for operation of a computer from a teristics of human voices, such as the amplitude-
remote site. vs.-frequency function or the amplitude-vs.-time
visual horizon 1. The distance from a given point function.
to the farthest visible point on the surface of the voice band See VOICE FREQUENCIES.
earth in a particular direction. 2. The enclosed voice coil The moving coil of a dynamic micro-
geometric plane figure on the surface of the earth, phone or dynamic speaker.
representing the set of farthest-visible points for a voice-controlled break-in A type of break-in oper-
particular location. ation for radiotelephony, in which the transmitter
visual telegraphy Telegraphy in which the re- automatically switches on and the receiver
ceived signals are read from a visual device, such switches off immediately when the operator starts
as a blinking light, meter, or swinging pen. talking; the transmitter switches off and the re-
visual transmitter The equipment used to trans- ceiver switches on a moment after the operator
mit the picture portion of a television broadcast. stops talking.
visual transmitter power The peak power output voice-controlled relay An electronic relay that is
of a visual transmitter during normal operation. actuated by the human voice.
vitreous Pertaining to a material or surface resem- voice filter 1. A filter for passing, suppressing, or
bling, or related to, glass (e.g., the vitreous modifying voice frequencies. 2. A parallel-
enamel on certain types of resistors). resonant circuit inserted into a line that feeds
VLF Abbreviation of VERY LOW FREQUENCY. several loudspeakers, to trap certain frequencies
VLR 1. Abbreviation of VERY LOW RESISTANCE. and thereby improve the sound of the reproduced
2. Abbreviation of VERY LONG RANGE. voice.
VLSI Abbreviation of VERY-LARGE-SCALE INTE- voice frequencies 1. The audio-frequency range of
GRATION. human speech, from about 60 Hz to 8000 Hz. 2.
V/m Abbreviation of VOLTS PER METER (a unit of The frequencies within the audio passband of a
electric field strength). typical single-sideband voice transmitter or re-
VMOS Abbreviation of vertical-metal-oxide semicon- ceiver. The lower limit is generally 200 Hz to 300
ductor. Hz; the upper limit is about 2500 Hz to 3000 Hz.
731
voice-frequency carrier telegraphy • voltage-breakdown test


voice-frequency carrier telegraphy A type of car- volatile 1. Capable of evaporating (e.g., volatile sol-
rier-current telegraphy (see WIRED WIRELESS) vents used in the encapsulation of electronic
in which the modulated carrier can be transmit- equipment). 2. Explosive (noun and verb). 3. Per-
ted over a telephone line having a voice-frequency taining to a state which is difficult to maintain
bandwidth. (e.g., a VOLATILE MEMORY).
voice-frequency dialing A system of telephone di- volatile memory Memory, usually of the random-
aling involving the conversion of direct-current access type, whose data vanishes when power is
pulses into voice-frequency alternating-current removed unless some provision is made for mem-
pulses. ory backup. The most common means of memory
voice-frequency telephony Wire telephone com- backup is the use of an electrochemical cell or
munication in which the frequencies of the elec- battery. Modern memory chips need so little cur-
tric waves are identical to the frequencies of the rent to store their data that a backup battery
sound waves (or very nearly so). lasts almost as long in the circuit as it would on
voice grade Pertaining to a communications sys- the shelf. The main advantage of this type of

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