. 31
( 42)


primary frequency standard A device that gener- input voltage. Compare SECONDARY VOLTAGE.
ates unmodulated signals at precise frequencies. primary winding The normal or usual input wind-
It generally uses a highly stable crystal oscillator ing of a transformer. Also called primary coil.
that can be referred to a time standard and peri- Compare SECONDARY WINDING.
odically corrected. A string of multivibrators, to- prime meridian See ZERO MERIDIAN.
gether with harmonic amplifiers and buffers, prime mover A machine, such as a gas engine,
divide, and multiply the fundamental crystal fre- steam engine, or water turbine, that converts a
quency. The resulting signals provide markers for natural force or material into mechanical power.
calibrating receivers and test equipment. Com- primitive oscillation period In a complex oscilla-
pare SECONDARY FREQUENCY STANDARD. tion waveform, the shortest period for which a
Also see PRIMARY STANDARD. definite repetition occurs; the highest fundamen-
primary impedance 1. The impedance of the pri- tal frequency.
mary winding of a transformer whose secondary principal axis The line passing through the center
winding is unloaded. Compare SECONDARY of the spherical part of a lens, mirror, or dish re-
IMPEDANCE, 1. 2. An external impedance pre- flector.
sented to the primary winding of a transformer. principal focus The focal point of rays arriving
Compare SECONDARY IMPEDANCE, 2. parallel to the principal axis of a lens, mirror, or
primary inductance The inductance of the pri- dish reflector.
mary winding of a transformer whose secondary
winding is unloaded. Compare SECONDARY IN-
primary kVA The kilovolt-amperes in the primary
circuit of a transformer. Compare SECONDARY
primary measuring element A detector, sensor,
or transducer that performs the initial conversion
in a measurement or control system. Such an el-
ement converts a phenomenon into a signal that
can be transmitted to appropriate instruments
Principal axis
for translation and evaluation.
primary power Power in the primary circuit of a
transformer. Also see PRIMARY KVA and PRI-
primary radiator 1. The driven element of a direc-
tive antenna system that incorporates parasitic
elements. 2. The driven element of a directive an-
Principal focus
tenna that uses a reflector, such as a screen or
primary resistance The direct-current resistance
of the primary winding of a transformer. Compare
primary standard A usually stationary source of a principal focus
quantity (e.g., capacitance, frequency, time, in-
ductance, resistance, etc.). This source is so pre-
cise, and is maintained with such care, that it principal mode See DOMINANT MODE.
can be used as a universal reference. Compare principal ray The path described by an electron en-
SECONDARY STANDARD. tering an electron lens parallel to the lens™ axis, or
primary turns Symbol, Np. The number of turns in by an electron leaving this lens parallel to the axis.
the primary winding of a transformer. Compare print 1. The material transferred from a typewriter
SECONDARY TURNS. onto paper. 2. The command, in a computer sys-
print • private branch exchange

tem, that causes data to be placed on paper or There are several types, including the dot-matrix
onto the output screen. 3. The alphanumeric out- printer, the daisy-wheel printer, the inkjet printer,
put of a computer or data terminal. and the laser printer. Some printers, such as the
printed capacitor A two-plate capacitor formed on daisy-wheel type, can render only text data;
a printed circuit. others, such as the laser type, can print high-
printed circuit A pattern of conductors (corre- resolution graphic images, sometimes in color.
sponding to the wiring of an electronic circuit) printing calculator 1. An electronic calculator
formed on a board of insulating material, such as that supplies a printed record of the results of a
a phenolic, by photo-etching, silk-screening of calculation. 2. For a programmable calculator,
metallic paint, or by the use of pressure-sensitive the results, a record of program steps, and plots
preforms. The leads or pins of discrete compo- of curves.
nents are soldered to the printed metal lines at printing digital voltmeter Abbreviation, PDVM. A
the proper places in the circuit, or the compo- digital voltmeter that delivers a printed record of
nents can be formed along with the conductors. a voltage reading, in addition to the usual digital
Also see ETCHED CIRCUIT. readout of the voltage.
printed-circuit board A usually copper-clad plas- printing telegraph 1. A telegraph that prints the
tic board used to make a printed circuit. received message on a tape or page. 2. See TELE-
printed-circuit lamp A baseless lamp having flex- TYPEWRITER.
ible leads for easy soldering or welding to a printing wheel See PRINT WHEEL.
printed circuit. print format The form of data transmitted by a
printed-circuit relay A usually small relay pro- computer program to a printer (e.g., plain text,
vided with pins or lugs for easy solder connection graphics, color graphics, etc.).
to a printed circuit. printout See DATA PRINTOUT, 1, 2.
printed-circuit switch A rotary switch whose con- print-through In prerecorded magnetic tape on a
tacts and contact leads are printed on a substrate. reel or cassette, the transfer of magnetism be-
printed-circuit template Also called etching pat- tween layers of the rolled-up tape.
tern. A drawing for the purpose of making print wheel In a daisy-wheel printer, the rotatable
printed-circuit boards by photographic means. wheel on whose rim the letters, numbers, and
printed coil A flat, spiral coil formed on a printed other symbols are inscribed in relief.
circuit. priority indicator In data transmission, a code
that specifies the order of importance of a mes-
sage in a group of messages to be sent.
priority processing In multiple programming op-
erations, a system for ascertaining the order of
processing for different programs.
privacy code 1. A subaudible tone used in cord-
less telephone systems to reduce the chances of
interference between phones operating on the
same channel in close proximity. 2. A subaudible
tone used in radio transmissions, especially in
conjunction with repeaters, to allow only those
stations with the proper code to be received. 3. A
tone-burst sequence at the beginning of a trans-
mission that actuates a receiver, allowing only
those stations with the proper code to be re-
printed-circuit template
privacy equipment Devices, such as speech
scramblers and digital encryption programs, that
printed component A component formed on the
provide some measure of secrecy in communica-
substrate of a printed circuit. See, for example,
privacy switch In a telephone amplifier, a switch
(usually a pushbutton) for muting outgoing mes-
printed display See DATA PRINTOUT, 2.
printed element See PRINTED COMPONENT.
private automatic exchange Abbreviation, PAX. A
printed inductor See PRINTED COIL.
dial telephone system for use within an organiza-
printed resistor A resistor printed or painted on a
tion and having no connection to the central of-
printed circuit.
printed wiring The printed or etched metal lines
private branch exchange Abbreviation, PBX. A
that serve as the conductors in a printed circuit.
telephone system, complete with a private manu-
printer In computer and calculator operations and
ally operated switchboard and individual tele-
in measurement procedures, a readout device
phone sets, installed and operated on private
that prints a permanent record of output data.
556 private branch exchange • program

premises but having trunk-line connection to the product 1. The result of mixing or heterodyning of
central office. Compare PRIVATE AUTOMATIC two or more signals. 2. The result of modulating
EXCHANGE. one signal with another. 3. The result of combin-
private line 1. A communication circuit in which ing or processing a signal or signals in a specified
the use is limited, by electronic means, to certain manner. 4. The saleable end result of a manufac-
subscribers. 2. A subaudible-tone system used to turing process. 5. The result obtained when two
restrict access to a communications system. The or more quantities are multiplied by each other.
tone frequency is predetermined. For access to product detector A detector circuit whose output
the system, a transmitted signal must contain is the product of two signals applied simultane-
the tone of the appropriate subaudible frequency, ously to the circuit. In a single-sideband receiver,
in addition to the voice or other information. for example, one of the signals is the incoming
probability 1. The branch of mathematics con- signal; the other, the signal from the local beat-
cerned with the likelihood of an event™s occur- frequency oscillator.
rence. It has many applications in quality control
and physics. 2. The mathematical likelihood that
+12 V
an event will occur.
probable error Abbreviation, PE. The value of error
above and below which all other error values are

equally likely to occur.
probe 1. A usually slender pencil-like implement

with a pointed metal tip and a flexible, insulated
lead. It is used to contact live points in a circuit
under test (e.g., voltmeter probe and oscilloscope
probe). 2. A device used to sample a radio-
frequency voltage or current at a desired point
(e.g., WAVEGUIDE PROBE). 3. A pickup device
shaped like a probe for insertion into close
quarters (e.g., PROBE THERMISTOR).
Local osc.

probe thermistor A thermistor of slender con-
struction for insertion into an area in which the
temperature is to be monitored or controlled.
probe thermocouple A thermocouple in the form
of a slender probe for insertion into close quarters
for temperature sensing or temperature control. product detector
probe tip See PROD.
probe-type voltmeter A voltmeter installed in a
production lot A manufactured set of compo-
long probe or wand. Kilovoltmeters are some-
nents, circuits, or systems, intended for sale. All
times constructed in this fashion, with a long
of the units in the lot are identical. The finished
multiplier resistor housed in the probe.
product is suitable (presumably) for consumer
probing A process for locating, or determining the
existence of, external artificial interference (e.g.,
production unit One unit in a production lot; a
power-line noise) in a radio communications cir-
finished unit, ready for use by a consumer.
product modulator A modulator whose output is
problem-oriented language Any high-level com-
equal or proportional to the product of carrier
puter programming language that allows the user
voltage and modulating voltage.
to write programs as statements in terms appli-
product of sine waves The result of multiplying
cable to the field of interest (e.g., COBOL™s state-
one sine wave by another with attention being
ments in English for problems relating to
paid to the power factor. In the case of a resistive
circuit, where the power factor is equal to 1, all
problem reduction In artificial intelligence, a pro-
voltage-current (EI) products are positive, and are
cess in which problems are made easier by break-
equal to the true power. A product wave has neg-
ing them down into smaller logical parts.
ative half-cycles when the circuit contains reac-
process control The control of a process, such as
one of manufacturing, by means of computers.
professional engineer A person licensed by a state
processor 1. A circuit or device used to modify
board of examiners to work independently as an
a signal in response to certain requirements
engineering. Also see PE and REGISTERED PRO-
(e.g., clipper and waveshaper). 2. See DATA-
program 1. In computer operations, a detailed se-
quence of instructions representing an algorithm
prod The metal tip of a probe (see PROBE, 1).

program • promethium cell

(the necessary steps in solving a problem) that program register See CONTROL REGISTER.
can be implemented by a computer. 2. The con- program segment A unit within a computer pro-
tent of a radio or television broadcast during a gram that is stored with others in memory at the
specified period of time. 3. In audio recording, the time of the program™s execution, or sometimes, as
composite output from the mixer, used to make overlays loaded individually when the entire pro-
the master tape or disc. gram exceeds memory capacity.
program address counter See INSTRUCTION program specification A description of the steps
REGISTER. involved in the solution of a problem, from which
program amplifier A broadcast preamplifier used a programmer devises a computer program.
at the studio or a remote location. program step An instruction in a computer pro-
programatics The study of computer programming. gram.
program circuit In wire telephony, a circuit capa- program tape In computer operations, a magnetic
ble of handling music and other audio data that or paper tape that contains programs for a sys-
covers a wide band of frequencies. tem or application.
program compatibility The condition in which a program timer 1. A programmed timer (see CY-
program written for one computer can be used CLE TIMER). 2. A timing unit that controls the
with another computer having a different archi- duration of a program.
tecture. progressive scanning Non-interlaced television
program controller In a central processor, a unit raster scanning, in which the lines are traced
that controls the sequence and execution of pro- from top to bottom in succession. Conventional
gram instructions. television broadcasting uses INTERLACED
program file A flexible reference system for soft- progressive wave A wave disturbance that travels
ware library maintenance. through a theoretically perfect homogeneous
program flowchart A representation of a computer medium. This can be a compression (longitudi-
program in the form of a flowchart. Each function nal) wave, a transverse wave, or an electromag-
and transition point is indicated by a box in the netic wave.
chart. A user can follow the flowchart and deter- projected cutoff For an amplifier circuit, the oper-
mine the outcome of the program for any given ating point at which crossover distortion van-
set of input parameters. ishes. The direct-current bias voltage (grid or
program library A collection of computer or pro- gate) required for projected cutoff is somewhat
grammable-calculator programs. Usually, it lower than the value corresponding to conven-
means the collection of programs used in a given tional cutoff of plate or drain current.
computer system, often a software package sup- project engineering A field of engineering dealing
plied by the hardware vendor. It might also be a with the coordination of a complete project.
catalog of programs with instructions for their use. projection television Large-screen television for
programmable calculator A calculator that can be viewing by a relatively large group, usually ac-
programmed to perform a chain of operations in a complished via a projection tube and optical sys-
given order repetitively. tem.
programmable read-only memory In a computer, projection tube A cathode-ray tube, especially a
a read-only memory (ROM) that can store a pro- television picture tube, capable of producing a
gram. bright image that can be projected onto a large
program maintenance The ongoing correcting, screen by means of a lens system.
updating, and modification of computer pro- projector 1. A device that transmits a visible image
grams belonging to a system. onto a surface for reproduction. 2. In general, any
programmed dump A dump that occurs during a device that transmits a signal into space.
program run, according to a program instruction. PROLOG Acronym for programming in logic. A
programmed halt During a computer program high-level computer programming language, sim-
run, a temporary cessation resulting from an in- ilar to LISP, used in artificial intelligence. The op-
terrupt or halt instruction. erator inputs facts and rules; the computer, in
programmed instruction See MACRO INSTRUC- effect, derives theorems from the facts by follow-
TION. ing the logical rules.
programmed timer See CYCLE TIMER. PROM Abbreviation of PROGRAMMABLE READ-
programmer A person who writes computer pro- ONLY MEMORY.
grams. promethium Symbol, Pm. A metallic element of
program modification 1. In computer program- the rare-earth group, produced artificially.
ming operations, a change in the effect of instruc- Atomic number, 61. Atomic weight, approxi-
tions and addresses during a program run by mately 145. Formerly called illinium.
performing arithmetic and logical operations on promethium cell A radioactive battery cell using
them. 2. Rewriting, or adding a patch to, a com- an isotope of promethium. Radioactive particles
puter program. Also see PATCH, 3. from this substance strike a phosphor, causing it
558 promethium cell • protective gap

to glow. Self-generating photocells then convert proportional amplifier An amplifier in which the
this light into electricity. instantaneous output amplitude is proportional
PROM programmer An electronic device that can to the instantaneous input amplitude.
store a computer program in a PROGRAM- proportional control A voltage-regulation system
MABLE READ-ONLY MEMORY (PROM). It uses a in which the feedback correction voltage is pro-
built-in keyboard. portional to the output-voltage error.
prompt In computer operations, a message re- proportional counter A Geiger tube having a
ceived by an operator from an operating system pointed-wire (or ball-tipped-wire) anode. The volt-
or an individual program. For example, in disk age developed across the load resistor is propor-
operating system (DOS), it could be the statement tional to the number of ions created by the
“Bad command or file name.” radioactive particles entering the tube.
prompting In computer or programmed-calculator proprioceptor A set of transducers and associated
operations, the entry of a special, required vari- circuitry that allows a computerized robot to con-
able when the machine halts and awaits such en- stantly sense the positions of its end effectors, and
try. use this data in carrying out programmed tasks.
prong See PIN. prosodic features Variations in voice tone and em-
prony brake An arrangement for measuring the phasis that lend meaning and implication to
mechanical power output of a rotating machine. spoken statements. It is important in advanced
It is a special form of friction brake consisting of computer speech recognition and speech synthe-
a band passed around a pulley on the rotating sis systems. Two sentences with identical wording
shaft of the machine under test and held at each can have greatly different meanings, depending on
end by a spring balance. these factors (e.g., “You are!” versus “You are?”).
propagation 1. The extension of energy into and prosthesis An electromechanical artificial human
through space. Thus, radiant energy is propa- limb or body part. Examples: artificial legs, artifi-
gated from and by its source. 2. A phenomenon cial hands, and artificial respirators. Some such
resulting from the extension of energy into and devices are computer-controlled; others can be
through space. Thus, radio waves can be spoken manipulated by nerve impulses.
of as a propagation. protactinium Symbol, Pa. A relatively short-lived
propagation constant For waves transmitted radioactive metallic element. Atomic number, 91.
along a line, a number showing the effect the line Atomic weight, 231.04 Formerly called protoac-
has on the wave. This is a complex figure [i.e., one tinium.
containing a real-number component (the attenu- protected area A region to which access is re-
ation constant) and an imaginary-number com- stricted, and that is secured by an alarm system,
ponent (the phase constant)]. surveillance cameras, or other intrusion-preven-
propagation delay 1. Symbol, tpd. In an inte- tion systems.
grated-circuit logic gate, the time taken for a logic protected location In computer storage, a loca-
signal to be propagated across the gate. 2. In dig- tion whose contents are protected from mutila-
ital-circuit operation, the time required for a tion or erasure by making the location usable
logic-level change to be transmitted through one only by following a special procedure (e.g., using
or more elements. a password).
propagation delay-power product See DELAY- protection In a multiple processing computer sys-
POWER PRODUCT. tem, preventing interference between data or pro-
propagation factor The ratio E/Eo, where E is the grams.
complex electric-field strength at a point to which protective bias In the final power amplifier of a ra-
a wave has been propagated, and Eo is the com- dio transmitter, external direct-current bias ap-
plex electric-field strength at the point of origin. plied to the base, gate, or grid. Prevents runaway
Also called propagation ratio. in collector, drain, or plate current when the bias
propagation loss The path loss of an electromag- caused by the driving signal is lost.
netic disturbance between the transmitting and protective capacitor A power-line bypass capaci-
receiving antennas. tor.
propagation mode See WAVEGUIDE MODE. protective device 1. A component that breaks a
propagation ratio See PROPAGATION FACTOR. circuit in the event of excessive voltage or current
propagation time In digital-circuit operation, the from the power supply. 2. A device that prevents
time required for a binary bit to be transferred excessive power from being delivered to a load by
from one point to another in the system. a driving circuit.
propagation velocity See VELOCITY OF PROPA- protective gap 1. A spark gap connected in paral-
GATION. lel with a component, or between a line and
proportional action An action, such as amplifica- ground as protection against high-voltage tran-
tion or conversion, that produces an output sients and surges. 2. A spark-gap-type lightning
signal proportional to the input signal. arrester.
protective resistor • pseudo-instruction

To proton A positively charged particle in the nucleus
antenna of an atom. The mass of a proton is approximately
1840 times the mass of an electron.
proton rest mass See MASS OF PROTON AT
Two-wire REST.
feed line proton-synchrotron A synchrotron that uses fre-
quency modulation of the radio-frequency accel-
erating voltage. It can accelerate protons to
energies of several billion electronvolts.
prototype The preliminary design or model of a de-
vice or system. It is often modified numerous
times before the final design is attained. Compare
Protective PILOT MODEL.
gaps proustite Crystalline silver arsenide trisulfide. Ar-
tificial crystals of this compound are used in tun-
able infrared-ray instruments.
proximity alarm A capacitance relay used to actu-
ate an alerting-signal device when an area is in-
truded upon or a person is too close to a
protective gap protected object. Also called INTRUSION ALARM.
proximity detector See PROXIMITY SENSOR.
protective resistor 1. A bleeder resistor connected proximity effect 1. The influence of high-
in parallel with a filter capacitor in a high-voltage frequency current flowing in one conductor on
direct-current power supply to discharge the ca- the distribution of current flowing in an adjacent
pacitor automatically, thus preventing electric conductor. 2. In an audio system, the result of
shock. 2. A series resistor that limits the current placing a microphone too close to a person™s
going through a device. mouth. Under these conditions, some spoken
consonants (e.g., B, F, P, and T) produce clapping
+ or booming sounds.
proximity fuse An electronic device situated in the
nose of a missile. When the missile is near the
target, the fuse transmits a signal that is reflected
back from the target; this reflected signal deto-
nates the missile.
proximity relay See CAPACITANCE RELAY.
proximity sensing The ability of a machine, espe-
cially a robot, to detect when an object is near.
This is an aid in robot navigation because it pre-
vents collisions. Some devices can measure the
distance from a robot, or from a robotic end effec-
tor, to a nearby object.
proximity sensor A device that indicates the pres-
ence of a nearby body. Such a device uses some
form of circuit, such as that of a CAPACITANCE
protective resistor, 2.
RELAY, that changes its operating characteristics
when an object enters its field.
protector 1. A fast-acting power-disconnect de- proximity switch See CAPACITANCE RELAY.
vice, such as a circuit breaker or fuse, that acts to PRR Abbreviation of PULSE REPETITION RATE.
protect electronic equipment. 2. A device or con- PRV Abbreviation of PEAK REVERSE VOLTAGE.
nection, such as a safety ground or ground-fault PS Abbreviation of POWER SUPPLY.
interrupter, that protects an operator from elec- ps Abbreviation of PICOSECOND. (Also, psec.)
tric shock. 3. See CONTACT PROTECTOR. PSD Abbreviation of PHASE-SENSITIVE DETEC-
protium The light isotope of hydrogen, having an TOR.
atomic mass of 1. psec Abbreviation of PICOSECOND. (Also, ps.)
protoactinium See PROTACTINIUM. pseudocode In a computer system, an instruction
protocol 1. A set of parameters for a digital com- or code symbol that affects the operation of the
munications signal. 2. The method by which a programming in an indirect manner.
procedure is followed; a uniform set of governing pseudo-instruction In computer programming op-
regulations. It ensures proper operation of a sys- erations, data representing an instruction and re-
tem or network. quiring translation by a compiler or assembler.
560 pseudo-offlining • pulling

pseudo-offlining During input/output operations PSWR Abbreviation of power standing-wave ratio.
in a computer system, maximizing hardware by psychoacoustics A field of acoustics, overlapping
disconnecting slow devices from the process in with psychology, concerned with the effects of
question. sounds on human beings.
pseudo-operation In computer operations, an op- PT Abbreviation of Pacific Time.
eration that, rather than being performed by Pt Symbol for PLATINUM.
hardware, is carried out by special software or by PTC Abbreviation of POSITIVE TEMPERATURE
macroinstruction. COEFFICIENT.
pseudo-random numbers Numbers that, although PtIr Symbol for PLATINIRIDIUM.
produced by a computer operating on an algo- PTM Abbreviation of PULSE-TIME MODULATION.
rithm for their generation, are useful for an appli- PTO Abbreviation of PERMEABILITY-TUNED OS-
cation requiring random numbers. CILLATOR.
pseudo-stereophonic effect A somewhat height- PTT Abbreviation for press-to-talk. See PRESS-TO-
ened binaural effect obtained when two loud- TALK MICROPHONE; PRESS-TO-TALK SWITCH.
speakers are situated, relative to the listener, so PTV Abbreviation of public television.
that a transit-time difference of 1 to 30 millisec- p-type conduction In a semiconductor, current
onds results. flow consisting of the movement of holes. Com-
p-type material Semiconductor material that has
been doped with an acceptor-type impurity and,
consequently, conducts current mainly via hole
migration. Germanium, for example, when doped
Level with indium, becomes p-type. Compare N-TYPE
equalizer MATERIAL.
p-type semiconductor An acceptor-type semicon-
ductor (i.e., one containing an excess of holes in
its crystal lattice).
PU Abbreviation of PICKUP.
Pu Symbol for PLUTONIUM.
public-address amplifier A high-gain, high-power
audio amplifier designed especially for the repro-
duction of speech and music at large gatherings.
public-address system A system of sound repro-
duction especially designed for use at large gath-
erings indoors or outdoors. The system includes
microphones, a public-address amplifier, loud-
speakers, and sometimes recorders and playback
devices. Also called PA system.
puck drive In a tape recorder, a speed-reduction
pseudo-stereophonic effect
system for driving the flywheel from the shaft of
the (high-speed) motor. In some machines, a rub-
ber tire mounted on the flywheel is driven,
psf Abbreviation of pounds per square foot. (Also, lb
per sq ft, lb/ft2.) through friction, by the motor shaft. In others, an
intermediate rubber-tired wheel is placed be-
psi 1. Abbreviation of pounds per square inch.
(Also, lb per sq in, lb/in2.) tween the motor shaft and the rim of the flywheel.
puffer A meter or bridge for measuring small val-
psia Abbreviation of POUNDS PER SQUARE INCH
ues of capacitance. The name comes from the
spoken sound of pF, the abbreviation of PICO-
psig Abbreviation of POUNDS PER SQUARE INCH
pulldown Descriptive of a circuit, device, or indi-
psi particle A massive elementary particle that
vidual component used to lower the value (e.g.,
represents a resonance in an electron-positron
impedance) of a circuit to which it is connected.
pull-in current The current required to close a re-
PSM Abbreviation of pulse-spacing modulation,
pulling 1. The abnormal tendency of one circuit to
more commonly called PULSE-INTERVAL MODU-
cause another to slip into tune with it. This often
results from coupling (intended or accidental)
psophometer A device used to measure noise in a
that is too tight. Thus, when two oscillators feed a
wire communications system. It provides quanti-
common circuit, such as a mixer, one might pull
tative readings based on typical human observa-
the other into tune with itself. 2. Lowering of a
crystal frequency by an external reactance.
psvm Abbreviation of phase-sensitive voltmeter.
pull-in voltage • pulse droop

pull-in voltage The voltage required to close a re- pulse-code modulation Abbreviation, PCM. A
lay. method of conveying information in wireless com-
pull switch A mechanical switch actuated by a munications. A train of pulses is transmitted. The
pulling action. intelligence-carrying signal is sampled periodi-
pullup Descriptive of a circuit or component used cally and the amplitude is converted into bi-
to raise the value (e.g., impedance) of a circuit to nary code. The code might allow for eight levels
which it is connected. (000 to 111), 16 levels (0000 to 1111), 32 levels
pulsar An extremely dense, rapidly rotating col- (00000 to 11111), or 64 levels (000000 to 111111).
lapsed star that produces radio signals at regular pulse-code-modulation binary code A pulse code
intervals. The pulse frequency varies from less used in communications not in the form of line
than one hertz to several tens or hundreds of transmission. Individual values are denoted by
hertz. binary numbers.
pulsating direct current A direct current that pe- pulse-code modulation multiplex equipment A
riodically rises and falls between zero and a max- multiplexer/demultiplexer for signal conversion
imum value (or between two positive or negative between a single signal and multiple-channel sig-
values) without changing polarity. Thus, it is pos- nals. It uses both pulse-code modulation and
sible to have either a pulsating positive current or time-division multiplexing.
a pulsating negative current. Also see DIRECT pulse-count divider A circuit or device that receives
CURRENT. an input of a certain number of pulses (or pulses
per second) and delivers an output that is a func-
tion of that quantity. See, for example, DIVIDE-BY-
pulse counter A circuit or device that indicates the
+8 number of pulses presented to it in a given time

pulse counting Counting pulses in a sequence. At
+4 low speed (pulse repetition rate), this can be done
with an electromechanical dial-type counter. At
+2 high speed, a fully electronic circuit is required.
pulse delay circuit A monostable multivibrator
adapted to deliver its single output pulse a prede-
termined time after the input pulse has been ap-
pulsating direct current
pulse dialing A form of telephone dialing in which
each digit is formed by a series of pulses, usually
pulsating wave See PULSATING DIRECT CUR- at 10 to 20 Hz. The pulses are the equivalent of
RENT. disconnecting the line for a few milliseconds. Each
pulse A transient signal that is usually of short du- digit has the corresponding number of pulses, ex-
ration, constant amplitude, and one polarity. A cept digit 0, which is formed by 10 pulses.
typical example is a narrow positive or negative pulse droop Distortion observable as a downward-
spike. sloping top on the oscilloscope trace of a pulse. It
pulse amplifier An amplifier having wide fre- can be quantified in volts, millivolts, microvolts,
quency response and low distortion, used for am- amperes, milliamperes, or microamperes.
plifying steep-sided pulses of short duration.
pulse-amplitude modulation Abbreviation, PAM.
A method of conveying information in wireless
communications. A train of pulses is transmitted.
The strength of each individual pulse varies ac- +6
cording to the modulating waveform. Normally,
the pulse amplitude increases as the instanta- Droop

neous modulating-signal level increases (positive
modulation). However, this can be reversed so
that higher audio levels cause the pulse ampli-
tude to go down (negative modulation).
pulse bandwidth For an amplitude pulse, the min-
imum bandwidth occupied. The faster the rise
and/or decay times of a pulse, the greater the
bandwidth. The greater the pulse frequency, the
greater the bandwidth. Time
pulse code A code in which groups of pulses repre-
sent digits. pulse droop
562 pulsed laser • pulse-time modulation

pulsed laser A laser in which flashes (pulses) of 2. A device that modulates pulses (see PULSE
high-intensity light excite the lasing medium. MODULATION, 2).
pulse duration The time period during which a pulse narrower A circuit or device that reduces the
pulse exists (i.e., its width on an oscilloscope dis- duration (width) of a pulse.
play). pulse-numbers modulation Abbreviation, PNM.
pulse-duration modulation Abbreviation, PDM. See PULSE-INTERVAL MODULATION.
See PULSE WIDTH MODULATION. pulse operation Intermittent operation of a circuit,
pulse equalizer A MONOSTABLE MULTIVIBRA- in the form of discrete pulses.
TOR adapted to deliver pulses of equal amplitude, pulse oscillator Any oscillator with an output that
shape, and width”even when it receives trigger consists of a series of pulses.
pulses of different kinds. pulse-position modulation Abbreviation, PPM. A
pulse fall time The time required for the trailing method of conveying information in wireless com-
edge of a pulse to fall from 90 to 10 percent of its munications. A train of pulses is transmitted. The
peak amplitude. Compare PULSE RISE TIME. timing of each individual pulse varies accord-
pulse-forming line A circuit used in radar for pro- ing to the modulating waveform. The pulses
ducing high-intensity pulses. Inductances and occur earlier or later than the nominal (zero-
capacitances are combined in a long string, and modulation) time, depending on the instanta-
the effect is to generate high-amplitude radio- neous amplitude of the modulating signal.
frequency pulses. pulse rate See PULSE REPETITION RATE.
pulse-frequency modulation Abbreviation, PFM. pulse ratio The ratio of pulse height (amplitude) to
See PULSE-INTERVAL MODULATION. pulse width (duration).
pulse generator A signal generator that produces pulse regeneration Restoration of the original
pulses. A general-purpose generator of this sort waveform and frequency to a pulse. It eliminates
will produce pulses of adjustable amplitude, du- distortion caused by circuits or propagation con-
ration, shape, and repetition rate. ditions.
pulse-height discriminator A circuit or device pulse repetition frequency Abbreviation, PRF.
that passes only pulses whose amplitudes exceed See PULSE-REPETITION RATE.
a predetermined level. pulse-repetition rate Abbreviation, PRR. The
pulse interval The interval between successive number of pulses per unit time; usually pulses
pulses. per second (pps).
pulse-interval modulation Abbreviation, PIM. pulse rise time The time required for the leading
Also called pulse-frequency modulation (PFM) or edge of a pulse to rise from 10 to 90 percent of its
pulse-numbers modulation (PNM). A method of maximum amplitude. Compare PULSE FALL
conveying information in wireless communica- TIME.
tions. A train of pulses is transmitted. Every pulse scaler A circuit actuated by the reception of
pulse has the same amplitude and the same du- a definite, predetermined number of input
ration, but their rate fluctuates with the modulat- pulses.
ing waveform. When there is no modulation, the pulse-shaping circuit 1. A circuit for producing a
pulses are evenly spaced with respect to time. An pulse from a wave of some other shape (e.g., sine
increase in the instantaneous data amplitude wave). 2. A circuit for tailoring a pulse to desired
might cause pulses to be sent more often (positive shape, amplitude, and duration.
modulation) or less often (negative modulation). pulse spacing The interval between successive
pulse inverter A single-stage, wideband, low- pulses.
distortion, common-emitter, or common-source pulse-spacing modulation Abbreviation, PSM. See
amplifier. The output-pulse waveforms are PULSE-INTERVAL MODULATION.
therefore inverted, with respect to the input-pulse pulse-steering diode In a flip-flop circuit, a diode
waveforms. through which the trigger pulse must pass to
pulse jitter In a pulse train, a disturbance charac- switch the circuit. Because of the unidirectional
terized by random changes in the spacing be- conductivity of a diode, pulses of only one polar-
tween pulses. ity are passed.
pulse-length modulation See PULSE-DURATION pulse stretcher 1. A shaping circuit that widens a
MODULATION. pulse (i.e., increases its duration). 2. A circuit,
pulse load The load impedance for a pulse genera- such as a special monostable multivibrator, that
tor. generates a pulse that is wider than the trigger
pulse mode See PULSE MODULATION. pulse.
pulse modulation See PULSE-AMPLITUDE MOD- pulse stuffing See JUSTIFICATION, 2.
ULATION, PULSE-CODE MODULATION, PULSE- pulse tilt The sloping of the normally flat top of a
pulse modulator 1. A modulator that delivers pulse-time modulation See PULSE-POSITION
power or voltage pulses for modulating a carrier. MODULATION.
pulse train • purity control

pulse train A series of successive pulses of usually pump frequency The frequency of a PUMP voltage.
one kind. pumping A method of laser actuation. A series of
pulse transformer A transformer designed to ac- pulses, at the resonant frequency of the lasing
commodate the fast rise and fall times of pulses material, is injected to cause laser output.
and similar nonsinusoidal waveforms. Such pump oscillator An oscillator for producing a
transformers often use special core materials and pump voltage.
are made using special winding techniques. pump voltage The voltage of a pumping signal.
pulse transmitter 1. A device that transmits a se- Also see PARAMETRIC AMPLIFIER and PUMP,
ries of pulses. 2. A pulse-modulated transmitter. 1, 2.
3. See PULSE MODULATOR. punch 1. A tool for cutting holes in metal chassis,
pulse waveform The general shape of a pulse as it panels, and boxes for electronic equipment. 2.
appears on an oscilloscope display. The various High signal strength.
forms range from positive or negative half- punch-in editing In audio recording, a feature
sinusoids, through rectangles, to thin-line spikes. that allows convenient insertion of new
pulse width The horizontal dimension of a pulse material on a tape. The tape recorder can be
(i.e., its duration). switched instantly from Play to Record, and
pulse-width modulation Abbreviation, PWM. Also back again, whenever the operator wants to add
called pulse-duration modulation (PDM). A material.
method of conveying information in wireless com- punchthrough In a bipolar transistor, the poten-
munications. A train of pulses is transmitted. tially damaging condition resulting when the re-
The width (duration) of each individual pulse verse bias of the collector is increased to a voltage
varies according to the modulating waveform. high enough to spread the depletion layer entirely
Normally, the pulse width increases as the in- through the base. This tends to effectively con-
stantaneous modulating-signal level increases nect the emitter to the collector.
(positive modulation). However, this can be re- punchthrough region The conduction region as-
versed so that higher audio levels cause the pulse sociated with higher-than-punchthrough voltage,
width to decrease (negative modulation). in which bipolar-transistor current is excessive.
punchthrough voltage The voltage that causes
Modulating PUNCHTHROUGH in a given bipolar transistor.
waveform puncture voltage See BREAKDOWN VOLTAGE, 1.
Pupin coil One of several loading coils that can be
inserted at intervals in series with a telephone
line to cancel line-capacitance effects and, thus,
improve the clarity of speech.
pure tone An audio-frequency (AF) tone having es-
sentially no harmonic content; a sine-wave AF
pure wave A wave containing no distortion prod-
purging The removal of an undesired gas or other
substance from a system by introducing a mate-
rial to displace it.
purifier A power-line operated alternating-current
electromagnet that can be manually rotated in
front of a color-television picture tube to demag-
pulse-width modulation netize the tube. Also called a DEGAUSSER.
purity 1. In color television, complete saturation
of a hue. 2. In a waveform, complete freedom
pump 1. In a parametric amplifier, the oscillator
from distortion. 3. The extent to which spurious
that supplies the signal that periodically varies
signals are attenuated in the output of a radio or
the reactance of the varactor. 2. The pumping
television transmitter. Also called spectral
signal in 1. 3. To perform the operation (pump-
ing) described in 1. 4. To increase the energy level
purity adjustment In a color-television picture
of an atom or molecule (by exposing it to electro-
tube, adjustment of each purity control for pure
magnetic radiation) to such an extent that oscil-
lation or amplification occurs. A ruby laser, for
purity coil A variable-current coil around the neck
example, produces its intense, coherent beam as
of a color-television picture tube that is used to
a result of pumping. 5. The radiation used to
adjust color purity.
pump an atom or molecule. 6. The device pro-
purity control For a purity coil, the variable resis-
ducing the radiation required to pump an atom or
tor that controls the current for color correction.
564 purity magnet • push-push multiplier

purity magnet A ring-magnet collar around the the input-signal cycle and deliver a combined
neck of a color-television picture tube to adjust, output signal.
by rotation, color purity. push-pull deflection In an oscilloscope, the appli-
purple plague Corrosion that occurs when alu- cation of deflection voltage to a pair of deflecting
minum and gold are placed in contact. plates 180 degrees out of phase with each other.
pushbutton tuner A radio or television tuner uti- For this purpose, the output amplifier in the hor-
lizing pushbutton tuning. izontal or vertical deflection channel is a push-
pushbutton tuning The tuning of a circuit to vari- pull stage.
ous frequencies in single steps by means of push- push-pull doubler See PUSH-PULL MULTIPLIER.
button switches. push-pull microphone A set of two microphones,
pushdown list In data processing, a method of in which the audio-frequency outputs are in
amending a list. A new item entered at the top phase opposition.
moves each existing item one position down. push-pull multiplier A push-pull amplifier with its
pushdown stack Also called first-in/last-out. A dig- output circuit tuned to an odd-numbered multi-
ital read-write memory in which data bits emerge ple of the input frequency. This circuit is unsuit-
in reverse sequence from the order they go in. If able for even-harmonic operation, but has some
data bit x enters the pushdown stack before data merit as an odd-harmonic multiplier (e.g., a
bit y, then x will come out after y. Compare tripler or quintupler). Also see PUSH-PUSH MUL-
push-in terminal A circuit contact or tie point, push-pull oscillator An oscillator stage in which,
usually of thin, springy material, that can be in- for increased power output, two active devices are
serted into a hole in a perforated board. operated 180 degrees out of phase with each
push-pull Pertaining to a circuit in which two ac- other in opposite halves of a symmetrical circuit.
tive devices are used, with the inputs and out- Also see PUSH-PULL CIRCUIT.
puts both placed in phase opposition. In the push-pull/parallel amplifier An amplifier stage in
output circuit, even harmonics are canceled, and which tubes or transistors are connected in
odd harmonics are reinforced. push-pull/parallel for increased power output.
push-pull/parallel circuit A push-pull circuit in
which two or more active devices are connected in
parallel on each side of the circuit. This arrange-
ment gives increased power output over that of
the conventional push-pull circuit. See, for exam-
push-pull/parallel oscillator An oscillator stage
in which active devices are connected in
push-pull/parallel for increased power output.
push-pull recording A type of film sound track
consisting of two side-by-side images 180 degrees
out of phase with each other.
push-pull transformer A transformer having a
center-tapped winding for operation in a push-
pull circuit.
push-push Pertaining to a circuit in which two ac-
tive devices are used, with the inputs connected
in phase opposition, and the outputs connected
in parallel. The result is reinforcement of the even
harmonics, and cancellation of the fundamental
push-pull amplifier An amplifier stage in which, frequency and all odd harmonics.
for increased power output, two active devices are push-push circuit See PUSH-PUSH MULTIPLIER.
operated 180 degrees out of phase with each push-push multiplier An amplifier circuit contain-
other in opposite halves of a symmetrical circuit. ing two active devices with their inputs connected
Also see PUSH-PULL CIRCUIT. in phase opposition and their outputs connected
push-pull circuit A symmetrical circuit in which in parallel. This circuit is unsuitable for funda-
two active devices operate on separate halves of mental-frequency and odd-harmonic operation,
push-push multiplier • PZT

pyramidal horn antenna A rectangular horn an-
tenna that is flared in two dimensions. The horn
width and height both increase linearly with in-
creasing distance (in the direction of maximum
radiation/response) from the feed point.
pyramidal wave See BACK-TO-BACK SAWTOOTH.
Pyrex A heat-resistant glass having numerous ap-
plications in electronics and chemistry.
pyrheliometer An instrument used to measure in-
frared radiation.
pyroelectricity In certain crystals, electricity gen-
erated by temperature change, and in particular,
by the application of heat.
pyroelectric lamp See NERNST LAMP.
pyroelectric material A crystalline material that
generates an output voltage when it is heated.
+12 V pyrolysis The process whereby heat changes a
substance into one of several different sub-
push-push stances by rearranging its atoms.
pyromagnetic effect In a material or circuit, the
combined effect of heat and magnetism.
but has some merit as an even-harmonic multi- pyrometer An instrument, other than a ther-
plier (e.g., a doubler or quadrupler). Also see mometer, used for the measurement of tempera-
push-to-talk switch See PRESS-TO-TALK Pythagorean scale A sound scale defining a spe-
SWITCH. cific type of relationship among audio tones. If x
pushup list In data processing, a method of and y are related by the Pythagorean scale and
amending a list, whereby new items are added at are adjacent in frequency, then a specific fre-
quency ( f ) exists, so x = f 2 and y = f 3.
the end of the list; all other items retain their orig-
inal positions. Compare PUSHDOWN LIST. Pythagorean theorem A theorem of plane geome-
pV Abbreviation of PICOVOLT. try. For a right triangle, with sides of lengths a, b,
PVC Abbreviation of POLYVINYL CHLORIDE. and c, where c is the side opposite the right angle,
it is always true that a2 + b2 = c2.
pW Abbreviation of PICOWATT.
PWM 1. Abbreviation of PULSE-WIDTH MODULA- p-zone See P LAYER.
TION. 2. Abbreviation of PLATED-WIRE MEM- PZM Abbreviation of PRESSURE-ZONE MICRO-
pwr Abbreviation of POWER. PZT Abbreviation of LEAD ZIRCONATE TITANATE.
Q 1. The figure of merit of a capacitor, inductor, or Radiating element
inductance-capacitance (LC) circuit, equal to the

reactance divided by the resistance. 2. Symbol for
electrical charge. 3. Occasional symbol for SE-
q 1. Symbol for quantity of electricity (in
coulombs). 2. Symbol for the charge carried by an
electron (the charge carried by a hole is repre-
sented by “q). 3. Symbol for the value of a quan-
Q adjustment The separate null adjustment for
the Q value of a component being tested in an
impedance bridge having separate resistive and
reactive balances.
Q-antenna An antenna in which the transmission Q-matching
line (feeder) is matched in impedance to the cen- section
ter of the radiator by means of a Q-matching sec-
Q band The radio-frequency band 36 to 46 GHz. It
is subdivided as follows: Qa, 36 to 38 GHz; Qb, 38
to 40 GHz; Qc, 40 to 42 GHz, Qd, 42 to 44 GHz;
and Qe, 44 to 46 GHz.
Q bar One of the parallel metal tubes in a
Q-matching section. Also see Q ANTENNA.
Q booster See Q MULTIPLIER. Feeder
Q bridge An alternating-current bridge used prin-
cipally to determine the Q of capacitors and
inductors. Bridges are usually used for
audio-frequency Q determinations; resonant-type
Q meters are generally used for measurement of
radio-frequency Q. Q-antenna

Copyright © 2001 by The McGraw-Hill Companies, Inc.
Click here for Terms of ®
QC • quad

QC Abbreviation of QUALITY CONTROL.

Q channel In American (NTSC) color television, the

Forward Q point.
508-kHz-wide green-magenta color information
transmission band.
QCT Abbreviation of QUALITY-CONTROL TECHNI- Reverse Forward
CIAN. voltage load line
QCW In the local oscillator and associated circuitry
Forward voltage
of a color television receiver, a 3.85-MHz CW sig-
nal of Q PHASE.

QCW signal In a color television receiver, the com-

Q point
ponent of the chrominance signal that is 90 de-
grees out of phase with the in-phase component. Reverse
load line
Q demodulator In a color television receiver, the
demodulator that combines the chrominance sig-
nal and the color-burst oscillator signal to recover
the Q signal (see Q SIGNAL, 2). Q points on diode characteristic
QED 1. Abbreviation of QUANTUM ELECTRODY-
NAMICS. 2. Abbreviation of quod erat demon-
strandum, Latin for “which was to be QRD Abbreviation of QUADRATIC RESIDUE DIF-
demonstrated.” Also, Q.E.D. Often written at the FUSOR.
conclusions of valid logical proofs and derivations. Q-section transformer See Q-MATCHING SEC-
Q factor See Q. TION.
QFM Abbreviation of QUADRATURE MODULA- Q signal In color television, the quadrature compo-
TION. nent of the chrominance signal, equal to +0.48(R-
QM Abbreviation of QUADRATURE MODULATION. Y) and to +0.41(B-Y), where B is the blue camera
Q-matching section A linear radio-frequency signal, R is the red camera signal, and Y is the lu-
impedance-matching transformer consisting of minance signal.
two straight, rigid, parallel metal conductors that Q signals A set of three-letter groups, each begin-
are used to match a feeder to an antenna. The ning with the letter Q, used for simplified tele-
section is 1„4 wavelength long at the operating fre- graph and radiotelegraph communication, and
quency. The diameters and center-to-center sometimes rapid voice communication (in ra-
spacing of the conductors are such that the char- diotelephony). Each signal represents a com-
acteristic impedance of the matching section is monly used phrase or message.
equal to the geometric mean of the feeder charac- QSL card A card verifying communication with, or
teristic impedance and the radiation resistance of the reception of signals from, the station sending
the radiator. Also see Q ANTENNA and QUAR- the card. Such verification is common in the am-
TER-WAVELENGTH MATCHING STUB. ateur radio service and with some shortwave
Q meter A usually direct-reading instrument for broadcast and CB stations.
determining the Q of a capacitor, inductor, or in- QSO Amateur radiotelegraph abbreviation for
ductance-capacitance (LC) circuit. Most Q meters TWO-WAY COMMUNICATION.
are operated at radio frequencies, but audio- Q spoiler A device or circuit that produces Q
frequency instruments are available. SPOILING in a laser.
Q modulation Amplitude modulation obtained by Q spoiling The technique of inhibiting laser action
varying the effective Q of a radio-frequency tank during an interval when an ion population excess
circuit in step with a modulating component. See is pumped up. When the laser is subsequently
ABSORPTION MODULATION. triggered by Q switching, a more powerful pulse
QMQB Abbreviation of quick make/quick break. of light results than would be otherwise obtained.
Q multiplier A positive-feedback (regenerative) Q switching A laser-switching action obtainable
amplifier that increases the effective Q of a tuned with Kerr cells or rotating reflecting prisms,
circuit, and thereby sharpens its response, when which consists of holding the Q of the laser cavity
its input is connected across the tuned circuit. to a low value during an ion-population buildup,
Q output The reference output of a flip-flop. then abruptly switching the Q to a higher value.
Q phase A color-television carrier signal that is 147 Q transformer See Q-MATCHING SECTION.
degrees out of phase with the color subcarrier. qty Abbreviation of QUANTITY.
Q point The point or points at which a load line in- quad 1. A combination of four components, such as
tersects a device characteristic (such as the col- diodes, transistors, etc., in a single housing. The
lector curve of a transistor or plate curve of a components are usually carefully matched. 2. In a
tube) and that identifies the quiescent operating cable, a combination of four separately insulated
point. conductors (sometimes, two twisted pairs) twisted
568 quad • quadrillion

together. 3. Abbreviation of QUADRANT. 4. See Quadrant
quad antenna A directional antenna similar to the
Yagi, except that full-wavelength loops are used
Quartz fiber
instead of straight elements. A two-element array Needle
can consist of a driven element and a reflector, or
it can have a driven element and a director. A Needle Quadrant
three-element system has one driven element,
one director, and one reflector. The director has
quadrant electrometer
a perimeter of about 0.97 electrical wavelength,
the driven element measures exactly 1 electrical
wavelength around, and the reflector has a quadraphonic sound Sound recording and repro-
perimeter of about 1.03 electrical wavelength. Ad- duction involving four channels.
ditional director elements can be added to the ba- quadraphony Music recording or playback in
sic three-element quad design to form arrays which four distinct information channels are
having any desired numbers of elements. The used. Also called four-channel stereo.
gain and directivity increase as the number of el- quadratic equation A second-degree equation
ements increases. Compare YAGI ANTENNA. [i.e., one in which the highest exponent is 2 (the
square of an unknown) (e.g., ax2 + bx + c = 0)].
quadratic residue diffusor Abbreviation, QRD. In
acoustics, a sound-reflection grating that scat-
ters (diffuses) sound waves almost uniformly in
Radiator all directions. The depths of the indentations in
the grating are determined according to a
quadrature The state of (cyclic events or points)
being 90 degrees out of phase.
quadrature amplifier An amplifier circuit that in-
troduces a 90-degree phase shift. Such amplifiers
are used in control devices, test instruments,
Stub transmitters, and color television receivers.
quadrature axes The vertical axes in the complex-
number plane (i.e., the +j and “j axes).
Feeder quadrature carrier See Q PHASE.
quadrature component 1. The reactive compo-
nent of an alternating current or voltage. 2. A vec-
quad antenna
tor perpendicular to a reference vector. 3. The
imaginary-number component in a complex-
quadded cable See QUAD, 2. number expression.
quadding Redundancy obtained by connecting quadrature current Reactive current in an alter-
components in series-parallel for enhanced relia- nating-current circuit.
bility and/or increased power-handling capacity. quadrature modulation In-phase modulation of
quad latch A set of four interconnected flip-flops two carrier components having a 90-degree phase
that is used for digital data storage. difference.
quadrant 1. A specific 90-degree arc of a circle. quadrature number See IMAGINARY NUMBER.
2. One of the four parts formed on a plane surface quadrature-phase subcarrier signal See QCW
by rectangular coordinates and designated I, II, SIGNAL.
III, and IV in a counterclockwise direction, start- quadrature portion In color television, the por-
ing with the upper-right quadrant. 3. An altitude- tion of the chrominance signal having the same
measuring instrument. (or opposite) phase as that of the Q-signal-
quadrantal deviation The part of magnetic- modulated subcarrier, and that is 90 degrees out
compass deviation caused by the induction of of phase with the in-phase portion.
transient magnetism into the horizontal soft iron quadrature sensitivity The sensitivity of a trans-
of a vessel by the horizontal component of ducer to motions in a direction that is perpendic-
terrestrial magnetism. ular to the normal axis of response.
quadrantal error See QUADRANTAL DEVIATION. quadrature voltage A voltage 90 degrees out of
quadrant electrometer An electrometer whose phase with another (reference) voltage.
principal parts are quadrants (a pillbox-shaped quadrilateral 1. Pertaining to an object having
brass chamber split into four parts) and a needle (a four sides. 2. A four-sided plane polygon.
flat, bowtie-shaped aluminum vane) suspended by quadrillion The number 1,000,000,000,000,000
a platinized quartz fiber between the quadrants.
quadripartite • quantized pulse modulation

quadripartite Having four parts. quantitative test A test performed to determine
quadripole network A four-terminal network, the numerical values (and their relationships)
usually with input- and output-terminal pairs. connected with observable phenomena. Compare
quadrivalent Having a valence of 4. Tin, for exam- QUALITATIVE TEST.
ple, is quadrivalent. Also called TETRAVALENT. quantity 1. A parameter (e.g., collector current,
quadruped robot A robot with four legs that can grid voltage, etc.). 2. In calculations, a positive or
move independently. It offers better stability than negative real number. 3. Electrical charge, usu-
three-legged designs. Functions well in mobile ally specified or measured in coulombs (see
machines that must navigate irregular terrain. COULOMB). Also called electrical quantity.
quadrupler 1. A rectifier circuit that delivers a di- quantization The conversion of a quantity having
rect-current output voltage approximately equal infinitely many possible values or levels (such as
to four times the peak value of the alternating- an analog signal) into one that can attain only a
current input voltage. 2. An amplifier or other cir- finite number of defined values or levels (such as
cuit that delivers an output signal of four times a digital signal). The number of levels is usually
the frequency of the input signal. some integral power of 2 (i.e., 2, 4, 8, 16, 32, etc.).
quadruplex circuit A data circuit in which two mes- This allows the levels to be represented as binary
sages are carried in each direction simultaneously. numbers.
quadrupole 1. A combination of two dipoles, pro-
ducing a force that varies inversely with the
fourth power of distance. 2. A four-pole magnet
used in some synchrotrons and linear accelera-
tors to focus and bend a particle beam. 3. A sys-
tem consisting of two dipoles of equal and
opposite direct moment.
qualification The quality-control or quality-
assurance scheme used in the production of
components, circuits, or systems. Certain
minimum requirements must be met for a device
to obtain qualification. 010
qualitative test A test performed to determine the
general mode of operation or the presence of cer- 001
tain factors, without regard to numerical values.
quality 1. In audio-frequency applications, fidelity Time
of transmission or reproduction. 2. The degree of
conformity of a product to specifications. quantization
quality assurance The outcome of measures taken
to bring performance into conformity with specifi-
cations. See QUALITY, 2. quantization distortion Distortion introduced by
quality control The surveillance of selection, man- the process of QUANTIZATION in a communica-
ufacturing, and testing operations to ensure con- tions or broadcast signal.
formity of a product to specifications. quantization distortion power The level of the
quality-control engineering The branch of engi- distortion in a signal resulting from QUANTIZA-
neering concerned principally with the technical TION. It is expressed in microwatts, milliwatts, or
methods of quality control and statistical meth- watts. It can also be expressed as a percentage, or
ods of assessing quality (see QUALITY, 2). as a level in decibels, relative to the power level of
quality-control technician A technician whose the input signal.
principal duty is the performance of operations in quantization error The difference between the ac-
the areas of incoming inspection, manufacturing tual values of quantities and their quantized val-
support, and product testing. Sometimes statisti- ues.
cal evaluations are required. quantization noise Noise introduced by the pro-
quality engineering A field of engineering that deals cess of QUANTIZATION in a communications or
with quality assurance and quality control in the broadcast signal.
production of components, circuits, and systems. quantize 1. To perform the process of QUANTIZA-
quality factor See Q. TION. 2. To split a quantitative commodity, such
quality-factor bridge See Q BRIDGE. as energy into its smallest measurable incremen-
quality-factor meter See Q METER. tal units.
quanta Plural of QUANTUM. quantized pulse modulation Pulse modulation in-
quantimeter An instrument used to measure the volving QUANTIZATION. Examples are PULSE-
quantity of X rays to which a body has been ex- CODE MODULATION and PULSE-NUMBERS
570 quantizer • quarter wavelength

quantizer A circuit or device that selects the digital quarter-deflection method A method of measur-
subdivision into which an analog quantity is ing high-frequency resistance, involving the use
placed (e.g., an analog-to-digital converter). of a sine-wave signal source, a standard nonin-
quantizing See QUANTIZATION. ductive variable resistor, and a square-law radio-
quantometer An instrument for measuring mag- frequency ammeter.
netic flux. quarter-phase See TWO-PHASE.
quantum 1. Abbreviation, Q. Plural, quanta. In quarter wave 1. The length of time corresponding
physics, the elemental unit or particle of electro- to 90 electrical degrees in a wave disturbance.
magnetic energy. The energy contained in one 2. The distance in space, or along a wire or feed
such particle is directly proportional to the fre- line that corresponds to 90 electrical degrees in a
quency, and inversely proportional to the wave- wave disturbance.
length. 2. See PHOTON. 3. Any discrete unit quarter-wave antenna An antenna in which the
derived by QUANTIZATION. radiator is an electrical quarter-wavelength long
quantum chromodynamics A term coined by Pro- at the operating frequency.
fessor Murray Gell-Mann for the theory of quarks
and gluons.
quantum counter A radiation-counter tube with a
window for the admission of light to the cathode.
quantum efficiency See QUANTUM YIELD.
quantum electrodynamics A branch of quantum
mechanics that involves the motions of electrons,
photons, and muons caused by electromagnetic
action. Quantum electrodynamics takes relativis-
tic effects into account.
quantum electronics The branch of electronics
concerned with energy states in matter.
quantum equivalence The principle that one elec-
tron is emitted for each photon absorbed by a ma-
terial (when the photon has the necessary energy).
quantum jump The abrupt movement of a particle
from one discrete energy state to another.
quantum level The orbit or ring occupied by an
electron in an atom.
quantum mechanics A branch of physics con-
cerned with the behavior of matter and energy, on Earth
the basis of observable data.
quantum noise A noise signal arising from ran-
dom variations in the average rate at which quarter-wave antenna
quanta impinge upon a detector.
quantum number A number that describes the en-
ergy level, or change in energy level, for a particle. quarter-wave attenuator In a transmission line or
quantum statistics A branch of QUANTUM ME- waveguide, two energy-absorbing structures sep-
CHANICS concerned with the distribution of ele- arated by an odd number of quarter wavelengths
mentary particles through various quantized so that the reflection from one structure is can-
energy levels. celed by that from the other.
quantum theory The theory that the emission or quarter-wave balun A balun using quarter-wave
absorption of energy by atoms or molecules oc- elements. One form of this device consists of
curs in discrete packages or units, rather than a grounded quarter-wavelength-long cylinder
continuously. Each unit is the emission or ab- closed at one end and open at the other, for
sorption of an energy packet called a QUANTUM. matching an unbalanced low-impedance line to a
Thus, radiant energy is thought to be divided into balanced high-impedance line.
quarter wavelength Symbol, »/4. The distance that
quantum transition The movement of an electron corresponds to 90 degrees of phase as an electro-
from one energy level to another within an atom. magnetic (EM) field is propagated. In free space, it
quantum yield The photoelectric efficiency of a is related to the frequency by a simple equation
light-sensitive surface in terms of the number of L ft = 246/f
electrons emitted for each absorbed quantum of
where L ft represents »/4 in feet, and f represents
the frequency in megahertz. If »/4 is expressed in
quark A hypothetical particle having a fractional
meters, then the formula is
electrical charge; quarks are thought to be con-
stituents of other subatomic particles. L m = 75/f
quarter wavelength • quartz plate

where L m represents the displacement in meters. quarter-wave termination In a waveguide, a set of
In general, if v is the velocity factor (expressed as two metal barriers separated by 90 electrical de-
a ratio) in a given medium, then: grees. One barrier totally reflects the energy strik-
ing it. The other barrier allows some energy to
L ft = 246v/f
pass through. Resonance occurs in the space be-
and tween the barriers.
L m = 75v/f quarter-wave transformer A quarter-wave reso-
Compare FULL WAVELENGTH, HALF WAVE- nant line short-circuited at one end by an ad-
LENGTH. justable slider. This arrangement is useful for
quarter-wavelength line A transmission line or radio-frequency impedance matching.
feeder that is a quarter-wavelength long at the quarter-wave transmission line See QUARTER-
operating frequency. Also called quarter-wave WAVE LINE.
line. quartic equation A fourth-degree equation of the
form ax4 + bx3 + cx2 + dx + e = 0, where a, b, c, d,
quarter-wavelength matching stub An arrange-
ment consisting of a quarter-wavelength-long and e are constants. Also called BIQUADRATIC
parallel-wire section of transmission line, used EQUATION.
for matching the impedance of a nonresonant quartz A mineral that is a variety of natural silicon
feeder to that of an antenna. It is similar to a Q- dioxide, or an artificially grown material of the
MATCHING SECTION, except that flexible trans- same sort. In the natural state, quartz occurs in
mission line (e.g., ladder line) is used, rather than hexagonal crystals having pyramidal ends. It has
rigid metal rods or tubing. various uses in electronics; one of the most com-
quarter-wave monopole A nondirectional UHF mon is the manufacture of piezoelectric crystals.
vertical antenna requiring no ground. The radia- quartz bar A comparatively large, thick piezoelec-
tor is 1„4 wavelength long, and is an enlarged- tric quartz plate used in standard-frequency os-
diameter outer sleeve connected to the outer cillators and in sharply tuned low-frequency
conductor of the coaxial feeder. The two sections filters. Common resonant frequencies are 50 kHz,
simulate a half-wave antenna. 100 kHz, and 1000 kHz.
quarter-wave plate A plate of double-refracting quartz crystal A natural or artificial piece of
crystalline material whose thickness allows the quartz cut to specific dimensions, usually self-
introduction of a quarter-cycle phase difference contained in a solder-in or plug-in enclosure. The
between the ordinary and extraordinary compo- device acts as a highly stable selective circuit. It
nents of light transmitted by it. exhibits a sharp resonance at the frequency for
quarter-wave radiator An antenna consisting of a which it is cut, and at harmonics of this fre-
single, usually straight, active element that mea- quency. It is used as the frequency-determining
sures an electrical quarter wavelength from end element in precision oscillators.
to end. When operated against electrical ground, quartz-crystal oscillator See CRYSTAL OSCILLA-
the element exhibits resonance. A simple quar- TOR.
ter-wavelength (»/4) conductor with a high quartz-crystal resonator See CRYSTAL RES-
length-to-diameter ratio measures approximately ONATOR.
95 percent of »/4 in free space. The element can quartz delay line An acoustic delay line using
be much shorter than free-space »/4 yet remain quartz to transmit the sound waves.
resonant when operated against electrical ground quartz-fiber electroscope An electroscope using a
if inductance is inserted in series with the radia- gold-plated quartz fiber, instead of gold leaves.
tor. The element can be much longer than free- quartz-halogen lamp An incandescent, usually
space »/4 yet remain resonant when operated low-voltage lamp used in automotive headlights,
against electrical ground if distributed capaci- and in some home and office lighting appliances.
tances are inserted in series with the radiator. It provides greater efficiency than conventional
quarter-wave resonance Resonance at the operat- incandescent lamps.
ing frequency in a quarter-wave antenna. quartz lamp A mercury-vapor lamp with a trans-
quarter-wave resonant line A section of transmis- parent quartz (instead of glass) envelope. Unlike
sion line (such as open-wire line or coaxial cable) glass, quartz readily passes the ultraviolet rays
that is a quarter-wavelength long at the operating generated by the mercury discharge.
frequency. Such a section is useful in impedance quartz lock A circuit that uses a CRYSTAL OSCIL-
matching and in various radio-frequency tests LATOR to regulate frequency, timing, or speed. It
and measurements. is used in electronic clocks and watches, televi-
quarter-wave stub See QUARTER-WAVE TRANS- sion receivers, synthesized radio receivers, trans-
FORMER. mitters, transceivers, high-fidelity turntables, etc.
quarter-wave support In a coaxial line, a quarter- quartz oscillator See CRYSTAL OSCILLATOR.
wave metal stub that can be used, instead of an quartz plate A piezoelectric plate cut from a quartz
insulator, to separate the inner and outer con- crystal. The plate is itself often called a crystal.
ductors. Also see CRYSTAL AXES and CRYSTAL CUTS.
572 quartz resonator • quick-break fuse

quartz resonator See CRYSTAL RESONATOR.
quartz timepiece A watch or clock having as its
control element a time-determining quartz crys-

quasi- A prefix meaning “to some extent” or “simi-
lar to,” as in quasi-optical radio wave (a radio Time
wave that behaves like a light ray).
quasi-bistable circuit A trigger-operated multivi-
brator. It operates as a flip-flop when the trigger
frequency is sufficiently high.

quasi-instruction In a computer program, a data
item appearing as an encoded instruction, but quasi square wave
that is not acted upon.
quasi-linear feedback system A system in which
the feedback elements are nearly linear, but not quench 1. To suddenly bring to an end (e.g., to
entirely linear. quench an oscillation). 2. To cool quickly, as in
quasi-negative Pertaining to a voltage that is the quenching of a heated metal object. 3. To ex-
negative, with respect to some other voltage, but tinguish the discharge in a gas tube.
whose absolute polarity is positive. For example, quench capacitor A capacitor that prevents a
+0.5 volt is quasi-negative, with respect to spark from arcing across an inductor when cur-
+5.5 volts. rent flow abruptly stops.
quasi-optical Behaving like light. The term is used quench frequency See QUENCHING FRE-
to describe certain extremely short radio waves or QUENCY.
other radiations that, like light rays, follow line- quenching action Typical operation of a superre-
of-sight paths and can be directed, reflected, re- generative circuit, in which regeneration is in-
fracted, or diffused. creased to nearly the point of oscillation and then
quasi-optical path A line-of-sight path followed by reduced; this action is repeated at an ultrasonic
very short radio waves, such as microwaves. frequency and results in very high sensitivity.
quasi-positive Pertaining to a voltage that is posi- Also see QUENCHING FREQUENCY, QUENCH
tive, with respect to some other voltage, but OSCILLATOR, and SUPERREGENERATIVE CIR-
whose absolute polarity is negative. For example, CUIT.
“0.5 volt is quasi-positive, with respect to quenching frequency The frequency at which re-
“5.5 volts. generation in a superregenerative circuit is in-
quasi-random A set of numbers considered to be creased and decreased.
random, but chosen according to an algorithm. quench oscillator In some superregenerative cir-
quasi-rectangular wave A wave whose shape ap- cuits, the separate ultrasonic oscillator that pro-
proaches that of a rectangular wave, but that duces the required quenching action.
possesses a small amount of tilt and/or curva- quench resistor A resistor in a quenching network
ture. that prevents a spark from occurring across an
quasi-scientific A term that is sometimes applied inductor when current flow stops.
to the design of electronic systems or to the ap- queue A list of data, steps in a process, or com-
praisal of circuit behavior, using an intuitive, mands awaiting execution in a specific order.
rather than analytical approach. queuing theory A branch of mathematical elec-
quasi-sine wave A waveform that is not a perfect tronics, dealing with the optimum order in which
sine curve, but is close enough to be considered steps should be executed to obtain a particular
sinusoidal, for all practical purposes. end result.
quasi-single sideband A modulated waveform that quibinary code In computer operations, a binary-
somewhat resembles single sideband, in which coded decimal system in which each decimal digit
parts of both sidebands are present. is represented by seven bits occupying places
quasi-square wave A waveform that is not a per- whose values are 8, 6, 4, 2, 0, 1, and 0.
fect square, but is close enough to be considered quibinary decade circuit A decade counter con-
square for all practical purposes. It is sometimes sisting of a ring-of-5, followed by a single binary
applied to a rectangular wave when a square stage.
wave is desired. quick break An operating characteristic of a
quasi-technical A term sometimes applied to qual- switch, relay, or circuit breaker whereby the con-
itative tests, as opposed to quantitative tests. tacts open rapidly”even when the actuating cur-
quaternary 1. Pertaining to a base-4 number rent or mechanical force is slow-acting.
system. 2. Of an atom, joined to carbon atoms for quick-break fuse A fuse in which the wire melts
four bonds. 3. The fourth member of a 4-unit set. and breaks almost instantly when the current
Quebec Phonetic alphabet code word for the rating is exceeded. Also called quick-blow fuse.
letter Q. Compare SLOW-BLOW FUSE.
quick-break switch • QWERTY

quick-break switch A switch that opens rapidly” quiescent period The no-signal interval during
even if its handle or lever is moved slowly by the which equipment is not operating”even though
operator. This action minimizes arcing and pre- it is energized.
vents chatter. Compare QUICK-MAKE SWITCH. quiescent point The point on the characteristic
quick charge The process of charging a battery, curve of a transistor, diode, or similar device, de-
such as a nickel-cadmium (NICAD) or nickel- noting the zero-signal operating conditions.
metal-hydride (NiMH) type, at a relatively rapid quiescent push-pull Denoting a push-pull stage,
rate, at high charging current. It is sometimes especially an audio power-output amplifier, in
used to charge a battery from a state of almost to- which the direct-current signal is essentially
tal discharge. Compare TRICKLE CHARGE. zero.
quick-disconnect The characteristic of a connec- quiescent state The inactive, or resting, state of
tor that enables its mating halves to be separated an active component, such as a transistor or vac-
quickly and simply, to break the circuit in which uum tube.
it is situated. quiescent value The zero-signal value of current
quickening liquid A solution of mercuric cyanide or or voltage for any component supplied with oper-
mercuric nitrate, into which objects can be dipped ating power.
prior to electroplating with silver. The process en- quiet AGC See DELAYED AUTOMATIC GAIN CON-
sures good adhesion of the silver to the object. TROL.
quick make An operating characteristic of a quiet automatic gain control See DELAYED AU-
switch, relay, or circuit breaker, whereby the con- TOMATIC GAIN CONTROL.
tacts close rapidly”even when the actuating cur- quiet automatic volume control See DELAYED
rent or mechanical force is slow acting. AUTOMATIC GAIN CONTROL.
quick-make switch A switch that closes rapidly” quiet AVC See DELAYED AUTOMATIC GAIN CON-
even if its handle or lever is moved slowly by the TROL.
operator. Compare QUICK-BREAK SWITCH. quiet battery A direct-current source specially de-
quick printer A high-speed printer, used with a signed and filtered to minimize noise components
data terminal or computer. A relative term, de- in its output.
pending on the user and the application. quieting Noise-voltage reduction in the output of a
quicksilver See MERCURY. frequency-modulation (FM) receiver when an un-
quick-stop control A control on tape recorders and modulated carrier is received. Also called noise
some dictating machines that allows the operator quieting.
to stop the tape, but keep the machine in the play quieting level In a frequency-modulation (FM) re-
or record mode. Also called pause control. ceiver, the limiter threshold point.
QuickTime Trade name (Apple Computer, Inc.) for quieting sensitivity In a frequency-modulation
system software commonly used in MULTIMEDIA (FM) receiver, the lowest input-signal amplitude
applications with personal computers. at which the output signal-to-noise ratio is below
QUICKTRAN For multiaccess computer systems, a the specified limit.
computer programming language based on FOR- quiet tuning A system of tuning in which the out-
TRAN and offering facilities, through the use of put of a receiver is muted until a station is tuned
remote terminals, for running, testing, debug- in properly.


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