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497
operating station • optical character reader


operating station In a computer installation, one operation part In a computer program, the part
or more consoles for the control of a data- of an instruction containing the OPERATION
processing system by an operator. CODE.
operating system Abbreviation, OS. In a computer, operation register In a digital computer, the regis-
a set of programs that oversee the functioning of ter that stores the operation code of an instruc-
the hardware and application software. It works tion.
with the basic input/output system (BIOS). operations research A branch of computer engi-
operating temperature The actual or recom- neering, devoted to the solution and/or optimiza-
mended temperature of a device during its opera- tion of functions of many variables.
tion. operation time The interval between the instant of
operating-temperature range For a given device, application of all voltages to a circuit, and the in-
the spread between maximum and minimum val- stant when the current reaches a specified per-
ues of operating temperature. centage of its final steady value.
operating time 1. The interval during which an operator 1. A person who performs an operation
equipment is in operation. 2. The period corre- (see OPERATE, 1). 2. In mathematics, a symbol
indicating an operation (e.g., j, +, “, —, etc.).
sponding to OPERATING ANGLE.
operating-time characteristic For a coil-type re- operator j See J OPERATOR.
lay, the relationship between operating time and opposition 1. The state of two quantities that are
operating power. 180 degrees out of phase with each other. 2. A
operating voltage The voltage required by a de- state in which two effects or quantities operate
vice, or measured at the device, during its opera- against each other in some manner (e.g., physi-
tion. Compare IDLING VOLTAGE. cally, mathematically, electrically, etc.).
operation 1. The working of a circuit or device (i.e., opt Abbreviation of OPTICAL.
its performance). 2. A process usually involving a Optacon An electronic aid for the blind. It has a
sequence of steps (e.g., a mathematical operation). camera that scans printed matter and a device
operational amplifier Also called an op amp. A that forms corresponding raised letters that can
specialized linear integrated circuit (IC) that con- be read, as would Braille, with the fingertips. The
sists of several transistors, resistors, diodes, and name is a contraction of optical to tactile con-
capacitors, interconnected to produce gain over a verter.
wide range of frequencies. A single amplifier can optical 1. Generating or sensing visible light.
comprise an entire IC, or an IC can contain sev- 2. Visible electromagnetic radiation in the range
eral amplifiers. The dual op amp and the quad op of approximately 390 to 750 nanometers wave-
amp are common variants. Some ICs contain one length.
or more amplifiers in addition to other circuits. optical ammeter A type of OPTICAL PYROMETER
The devices can be used with resistance-capaci- that measures the current flowing through the fil-
tance (RC) network combinations to build active ament of an incandescent lamp.
filters for use at audio frequencies. optical antenna A photosensitive device intended
operational differential amplifier An OPERA- for the reception of modulated-light or modu-
TIONAL AMPLIFIER preceded by a DIFFEREN- lated-infrared signals. Usually consists of a
TIAL AMPLIFIER. convex lens or a concave reflector and a
operational readiness In statistical analysis, the semiconductor photodetector.
probability that a system will, at a certain time,
be correctly operating or ready to operate.
operational reliability Reliability determined em-
pirically from a study of the actual operation of a
device or system under controlled conditions.
Also called ACHIEVED RELIABILITY.
operational transconductance amplifier Abbre-
viation, OTA. An integrated-circuit amplifier that
differs from the conventional operational ampli-
fier in that its output current is proportional to its
input-signal voltage.
operation code In computer operations, the part
of an instruction that specifies an operation.
operation decoder In a digital computer, the cir-
cuit that reads an OPERATION CODE and directs
other circuitry in the execution of the code. optical axis The z-axis of a quartz crystal (see
operation envelope See WORK ENVELOPE. Z-AXIS, 4).
operation number In computer programming, a optical character reader A device that uses OPTI-
number that indicates the position in the pro- CAL CHARACTER RECOGNITION to discern
gram of a particular operation or subroutine. printed characters.
498 optical character recognition • optical sound recording


optical character recognition Abbreviation, OCR.
Stationary
In computer and data-processing operations, the
light source
reading of alphabetical, numerical, and other
characters from hard copy (usually printed mat-
ter) by photoelectric methods. It converts the
characters into digital data that can be stored in
computer memory, on disks and tapes, and
transmitted via digital communications net-
works. It can also allow a computer or robot to Image
read signs, maps, etc.
optical communications One-way or two-way Mirror
communications via modulated visible light. It
can be conducted through optical fibers, the
Meter
atmosphere, water, or any other transparent
bearing
medium. Screen
optical coupler A coupling device consisting es- with scale
sentially of a light source (actuated by an input
signal) mounted in an opaque housing with a optical lever
light-sensitive device (that delivers the output
signal). In its simplest form, the arrangement
consists of a light-emitting diode (LED) and a optical mode The vibration mode that produces an
photodiode. oscillating dipole in a crystal lattice.
optical pattern A Christmas-tree-like pattern pro-
duced by parallel rays of light striking a phono
disk. Also see DIFFRACTION.
optical playback See OPTICAL SOUND REPRO-
Output
Amp.
Input Mod.
DUCER.
optical pyrometer A pyrometer for measuring the
temperature of a hot body in terms of the inten-
optical coupler sity and color of light it emits.
optical scanner An electronic device that converts
hard-copy text and graphics into digital form
optical detector An integrated-circuit (IC) that suitable for processing and storage in a com-
provides light-to-voltage conversion. Its direct- puter. There are several types; the most common
current output voltage is proportional to the in- resembles a small photocopy machine and is
tensity of light impinging on its sensor. known as a flatbed scanner. See OPTICAL SCAN-
optical encoder An electronic device that mea- NING.
sures the extent to which a mechanical shaft has optical scanning An electronic process that con-
rotated. It can also measure the rate of rotation verts hard-copy text and graphics into digital
(angular speed). It consists of a light-emitting form suitable for processing and storage in a
diode (LED), a photodetector, and a disk with al- computer. Text scanners work in conjunction
ternate light and dark bands (chopping wheel). It with specialized software. The optical scanner
is commonly used in digital controls and jointed and software together form the equivalent of au-
robot arms. dio speech recognition and sound interpretation.
optical fiber A glass or plastic medium through Usually, scanners are employed to convert
which light is propagated for optical-communica- printed matter to digital data. However, scanning
tions purposes. The refractive characteristics of technology can also be used at a distance, for ex-
the fiber keep the visible light inside. ample, by a robot for the purpose of reading road
optical lever A device for amplifying the effect of a signs.
small rotation. The rotating member carries a optical sound recorder A photoelectric machine
small mirror that reflects a light beam over a for recording sound on photographic film. Also
curved scale, the distance through which the see OPTICAL SOUND RECORDING.
light spot travels on the scale being proportional optical sound recording A system for recording
to the distance between the scale and the rotating sound on photographic film, as in sound motion
mirror. In this way, the deflection on the scale is pictures. The sound is picked up by a microphone
several times the length of the arc described by and amplified to vary the intensity of a light
the mirror, the rotation being thus amplified. source. The film passing this modulated beam be-
optical link See OPTICAL COUPLER. comes exposed to a variable-width or variable-
optical mark recognition A method of data trans- density track corresponding to the modulation
fer that involves the use of optical techniques. (see VARIABLE-DENSITY SOUND RECORD and
optical maser See LASER. VARIABLE-WIDTH SOUND RECORD). When de-
499
optical sound recording • Orange Book


veloped film is played back, its sound track mod- that results in maximum energy transfer. Also
ulates a light beam in the reproducer by actuating called CRITICAL COUPLING.
a photocell or phototube to produce the audio sig- optimum current The value of current that pro-
nal, which is then amplified. duces the most-effective performance of a circuit
optical sound reproducer A photoelectric ma- or device.
chine for reproducing sound on film. A light beam optimum frequency See OPTIMUM WORKING
in the device is modulated by the passing sound FREQUENCY.
track, and it, in turn, modulates photocell or pho- optimum load The value of load impedance that
totube current, which is amplified to drive a loud- produces maximum transfer of power from a gen-
speaker. Also see OPTICAL SOUND RECORDING. erator or amplifier.
optical system Collectively, the functional ar- optimum plate load The ideal load impedance (see
rangement of lenses, mirrors, prisms, and related OPTIMUM LOAD) for a particular electron tube
devices in optoelectronic apparatus. operated in a specified manner.
optical tachometer An optoelectronic instrument optimum Q The most effective figure of merit for a
for measuring (by means of reflected-light varia- capacitor, inductor, or tuned circuit at a specified
tions) the speed of a body, such as a rotating frequency.
shaft, without electrical or mechanical attach- optimum reliability The value of reliability that
ments to the latter. ensures minimum project cost.
optical thermometer See OPTICAL PYROMETER. optimum voltage The value of voltage that results
optical twinning A kind of defect in which two in the most effective performance of a circuit or
types of quartz occur in the same crystal. Com- device.
pare ELECTRICAL TWINNING. optimum working frequency In radio transmis-
optical type font A special type (printing) style sion involving reflection from the ionosphere, the
designed for use with OPTICAL CHARACTER frequency of use that results in the most reliable
RECOGNITION equipment. communication between two points.
optical wand A pencil-like optical probe, used to optoelectronic coupler An assembly consisting of
read bar codes from a printed page and translate an LED and a phototransistor. An input signal
the codes into information that is then loaded causes the diode to glow, and the light activates
into a computer or calculator. the transistor, which in turn delivers an output
optic axis See OPTICAL AXIS. signal of higher amplitude than that of the input
optic flow See EPIPOLAR NAVIGATION. signal.
optics 1. The science of light, its measurement, optoisolator A light-emitting diode (LED) or in-
application, and control. 2. A system of lenses, frared-emitting diode (IRED) and a photodiode
prisms, filters, or mirrors used in electronics to combined in a single package with a transparent
direct, control, or otherwise modify light rays. gap between them. The LED or IRED converts an
optimization The adjustment or manipulation of electrical signal to visible light or IR; the photodi-
the elements of a process or system for the best ode changes the visible light or IR back into an
operation or end result. electrical signal. This device eliminates interstage
optimize 1. To manipulate a set of variables or pa- impedance reflections that can plague systems
rameters for the best possible performance of a that employ electronic coupling. Even the most
circuit or system. 2. To maximize the value of a drastic changes in load impedance have no effect
multivariable function. on the impedance “seen” by the signal source.
optimum angle of radiation For a given altitude of The devices can also protect expensive equipment
the ionosphere, the angle, with respect to the against electrical transients; for example, in
horizon, at which a radio signal should be trans- telephone-line modems used with personal
mitted from a specific geographic location to pro- computers.
vide optimum reception at some other specific optoelectronics A branch of electronics that in-
location. This angle varies, depending on the alti- volves the use of visible light for communications
tude of the ionospheric layer from which signals or data-transfer purposes.
are returned, the distance between the transmit- optoelectronic transistor A transistor having an
ting and receiving stations, and the number of electroluminescent emitter, transparent base,
hops taken by the signal between the earth and and photoelectric collector.
the ionosphere. optophone A photoelectric device for converting
optimum bunching In a velocity-modulated tube, light into sounds of proportionate pitch to enable
such as a klystron, the bunching associated with blind persons to “see” by ear.
maximum output. Orange Book Trade name (Sony and Philips) for a
optimum collector load The ideal load impe- specialized format for compact-disc recordable
dance (see OPTIMUM LOAD) for a particular tran- (CD-R) computer data storage media. It allows
sistor operated in a specified manner. recording of data onto, as well as retrieval of data
optimum coupling The degree of coupling be- from, an optical compact disc. See also GREEN
tween two circuits tuned to the same frequency BOOK, RED BOOK, and YELLOW BOOK.
500 orange peel • orthiconoscope


orange peel On a phonograph disc, a mottled sur- results from a difference of one wavelength, the
face that produces high background noise; so second fringe from a difference of two wave-
called from its resemblance to an orange peel. lengths, etc. The center fringe indicates that the
orbit 1. Also called shell. The median path of an two signals are exactly in phase; that is, the dif-
electron around the nucleus of an atom. 2. The ference is zero wavelengths.
circular or elliptical path of an artificial satellite order of logic 1. A mathematical expression for
(e.g., a communications satellite) around the the complexity of a system of logic. 2. The relative
earth. 3. The elliptical path of the moon around speed with which logical information is processed
the earth. 4. The elliptical path of the earth or an- in a system.
other planet around the sun. 5. Any closed, usu- order tone A warning signal to receiving operators
ally circular or elliptical path, that an object in the form of a tone transmitted over a trunk
follows around another object. preceding the transmission of an order.
orbital-beam multiplier tube An electron- ordinary ray As a result of the double refraction of
multiplying UHF oscillator or amplifier tube in electromagnetic waves, the member of a pair of
which a positively charged electrode focuses rays that follows the usual laws of refraction. Also
electrons in a circular path. see O WAVE. Compare EXTRAORDINARY RAY.
orbital electron An electron in orbit around the ordinary wave See O WAVE.
nucleus of an atom. ordinate In the rectangular coordinate system, a
orbital period The length of time required by a point located on the vertical axis.
satellite to go around a celestial body, usually the organ 1. A computer subsystem. 2. An electronic
earth. It can vary from about 90 minutes for very device used for the purpose of generating music.
low orbits to months or even years for orbits be- organic decay See EXPONENTIAL DECREASE.
yond that of the moon. The moon™s period is organic electricity Electricity in the living tissues
about a month. of animals and plants.
OR circuit Also called inclusive-OR circuit. In dig- organic growth See EXPONENTIAL INCREASE.
ital systems and other switching circuits, a logic organic semiconductor A semiconductor material
gate whose output is high (logic 1) when any of consisting of, or combined with, some compound
the input signals is high. The output is low (logic of carbon.
0) only when all of the inputs are low. Compare OR gate See OR CIRCUIT.
AND CIRCUIT. orientation 1. The direction or position of an ob-
ject in space, expressed in terms of coordinate
values. 2. In a teleprinter, the calibration or
A
alignment that determines the speed of response
Inputs C Output to a received character.
B orientation of quartz plates See CRYSTAL AXES
and CRYSTAL CUTS.
orifice An opening or window, such as that in a
loudspeaker enclosure or waveguide, through
A B C
which energy is transmitted.
0 0 0
origin 1. The starting point in a coordinate system.
0 1 1 2. Relative to address modification in computer
operations, an address to which a modifier is
1 0 1
added to derive a variable operand address.
1 1 1
original lacquer In disc-recording operations, an
original recording made on a lacquer-surfaced
disc that is subsequently used to make a master.
2-input OR circuit original master In disk recording, the master disc
produced from a wax or lacquer disc (see ORIGI-
NAL LACQUER) by means of electroforming.
order 1. An instruction to a digital computer.
origin distortion The change in the shape of a
2. Sequence.
wave as it swings through zero (polarity).
OR element See OR CIRCUIT.
OR operation See OR CIRCUIT.
ordered pair A set of two variables or numbers
ORS Abbreviation of OMNIDIRECTIONAL RANGE
that can be mapped one-to-one onto a set of
STATION.
points in a plane. The most familiar example is
orthicon A television camera tube somewhat simi-
(x,y), used to depict the Cartesian (rectangular)
lar to the iconoscope, but which provides internal
coordinate system on which characteristic curves
amplification of light and, accordingly, can be
and other functions are plotted.
used in dimmer places than the iconoscope. Light
order of interference The position of an interfer-
amplification is provided by an arrangement sim-
ence fringe that depends on whether the interfer-
ilar to that of a photomultiplier tube.
ence arises from one, two, three, or more
orthiconoscope See ORTHICON.
wavelength differences. Generally, the first fringe
501
orthoacoustic recording • oscillator keying


orthoacoustic recording 1. A system of disc oscillation constant For an oscillating induc-
recording in which the inherent differences tance-capacitance (LC) circuit, the expression
(LC)1/2, where L is the inductance in henrys and C
between high-frequency recording and low-
frequency recording are compensated to provide is the capacitance in farads. The reciprocal of the
reproduction that more closely resembles the OSCILLATION NUMBER.
actual sound. 2. A disc made by the method oscillation control A manual or automatic device
defined in 1. for adjusting the frequency or amplitude of the
orthogonal axes Perpendicular axes [e.g., those in signal generated by an oscillator.
a Cartesian (rectangular) coordinate system]. oscillation efficiency The ratio, as a percentage,
Os Symbol for OSMIUM. of the alternating-current (signal) power output of
OS Abbreviation of OPERATING SYSTEM. an oscillator (Pout) to the corresponding direct-
osc Abbreviation of OSCILLATOR. current power input (Pin). Efficiency = 100Pout/Pin.
OSCAR Abbreviation for Orbiting Satellite Carrying oscillation number For an oscillating circuit, the
Amateur Radio. A satellite with a transponder number of complete oscillation cycles that occur
that has an uplink in one amateur band and a in 6.28 (2 pi) seconds.
downlink in another amateur band. oscillation test 1. A test of an oscillator to deter-
osciducer See OSCILLATING TRANSDUCER. mine if a signal is being generated. 2. A test for
oscillate 1. To fluctuate in amplitude in a uniform transistors wherein the transistor is used as an
manner. 2. To vary above and below a specified oscillator to give a rough indication of its condi-
value at a constant rate. tion in terms of oscillation amplitude.
oscillating arc A small arc, especially one pro- oscillation transformer A tank coil of a radio
duced by slow-opening relay contacts, that gener- transformer”especially one that includes an out-
ates high-frequency oscillations. put coupling coil.
oscillating circuit A closed circuit containing in- oscillator A device that produces an alternating
ductance, capacitance, and inherent resistance, or pulsating current or voltage electronically.
in which energy passes back and forth between The term is sometimes used to describe any
inductor and capacitor at a frequency determined alternating-current-producing device other than
by the inductance (L) and capacitance (C) values. an electromechanical generator.
oscillating crystal 1. A piezoelectric plate main- oscillator circuit The specific manner in which
tained in a state of oscillation in a circuit. See, for the components of an OSCILLATOR are intercon-
example, CRYSTAL OSCILLATOR and QUARTZ nected. The three general types are: positive-
CRYSTAL. 2. An oscillating semiconductor diode feedback, negative-resistance, and relaxation.
(see NEGATIVE-RESISTANCE DIODE, 1, 2). oscillator coil A tapped coil that provides the input
oscillating current See OSCILLATORY CURRENT. and output windings required for an oscillator cir-
oscillating detector A detector provided with pos- cuit. Such coils are used in signal generators, os-
itive feedback; therefore, it is capable of gener- cillators, and superheterodyne receivers.
ating a signal of its own. Compare oscillator-doubler A circuit consisting of an oscil-
NON-OSCILLATING DETECTOR. lator and a frequency doubler (e.g., a crystal os-
oscillating diode 1. A semiconductor diode biased cillator whose output frequency is twice the
into its negative-resistance region so that it oscil- crystal frequency).
lates in a suitable circuit. 2. An oscillating tunnel oscillator drift A usually gradual change in fre-
diode. 3. Any of several microwave diodes, such quency of an oscillator caused by such factors as
as the IMPATT diode, which will oscillate in a warmup time, voltage variations, capacitance
suitable system. 4. See MAGNETRON. Also see change, inductance change, or change in transis-
DIODE OSCILLATOR. tor characteristics.
oscillating field An alternating electric or mag- oscillator frequency The fundamental frequency
netic field. at which an oscillator operates. It can be deter-
oscillating rod A rod of magnetostrictive metal mined by a tuned circuit, crystal, cavity, section
maintained in a state of oscillation in a circuit. of waveguide or transmission line, or by a resis-
See, for example, MAGNETOSTRICTION and tance-capacitance circuit.
MAGNETOSTRICTION OSCILLATOR. oscillator harmonic interference In a super-
oscillating transducer A transducer in which an heterodyne receiver, interference that is the beat
input quantity varies a frequency proportionately product of local oscillator harmonics and received
from its center value. signals.
oscillating wire A wire of magnetostrictive metal oscillator interference Radio-frequency interfer-
maintained in a state of oscillation in a circuit. ence caused by signals from the high-frequency
See, for example, MAGNETOSTRICTION and oscillator of a receiver.
MAGNETOSTRICTION OSCILLATOR. oscillator keying Keying by making and breaking
oscillation The periodic change of a body or quan- the signal output, direct-current (dc) power, or dc
tity in amplitude or position (e.g., oscillation of a bias of the oscillator stage of a radiotelegraph
pendulum, voltage, or crystal plate). transmitter.
502 oscillator-mixer • oscillatory current


+ oscillator synchronization The locking of an os-
cillator in step with another signal source, such
as a frequency-standard generator.
oscillator tracking In a superheterodyne receiver,
the constant separation of the oscillator fre-
Output quency from the signal frequency by an amount
equal to the intermediate frequency at all settings
of the tuning control.
oscillator transmitter A radio transmitter con-
sisting only of a radio-frequency oscillator and its
power supply. The oscillator can be modulated in
various ways [e.g., on-off keying, frequency-shift
keying, voice amplitude modulation (AM), voice
frequency modulation (FM)].
oscillator trimmer In a superheterodyne receiver,
a small, limited-range capacitor connected in
parallel with the oscillator coil for tracking oscil-
lator tuning at the high end of a band. Compare
OSCILLATOR PADDER.
oscillator tuning The separate, often ganged, tun-
ing of the oscillator stage in a circuit.
oscillator keying

+
oscillator-mixer 1. A combination stage in which
a transistor functions as a local oscillator and
mixer in a receiver or test instrument. 2. A device
Variable
designed specifically to function as a local oscilla-
tuned
tor and mixer. circuit
oscillator-mixer-detector 1. In a superhetero- Output
dyne receiver, a stage in which the functions of
high-frequency oscillator, mixer, and first detec-
tor are performed by a single transistor. 2. A de-
vice designed specifically to function as a local
oscillator, mixer, and detector.
oscillator-multiplier A single circuit that serves si-
multaneously as an oscillator and frequency mul-
tiplier. See, for example, OSCILLATOR-DOUBLER.
oscillator padder In a superheterodyne receiver, a
small, limited-range variable capacitor connected
in series with the oscillator coil for tracking oscil-
lator tuning at the low end of a band. Compare oscillator tuning
OSCILLATOR TRIMMER.
oscillator power supply 1. The direct-current or
alternating-current power supply for an oscilla- oscillator-type power supply A high-voltage,
tor. 2. See OSCILLATOR-TYPE POWER SUPPLY. direct-current (dc) power supply in which a radio-
oscillator radiation The emission of radio- frequency (RF) oscillator generates a low-voltage
frequency energy by the oscillator stage of a alternating current (ac). This ac voltage is
superheterodyne receiver. Also see OSCILLATOR stepped up by an RF transformer, and is finally
INTERFERENCE. rectified to obtain high-voltage dc.
oscillator-radiation voltage The radio-frequency oscillator-type transmitter See OSCILLATOR
voltage at the antenna terminals of a super- TRANSMITTER.
heterodyne receiver that results from signal emis- oscillator wavelength The fundamental wave-
sion by the oscillator stage. length at which an oscillator operates. It is
oscillator stabilization 1. The automatic compen- usually expressed in meters, centimeters, or
sation of an oscillator circuit for the frequency millimeters. It can be determined by a tuned cir-
drift resulting from changes in temperature, cur- cuit, crystal, cavity, section of waveguide or
rent, voltage, or component parameters. 2. The transmission line, or by a resistance-capacitance
automatic stabilization of the operating point of circuit.
an oscillator circuit against variations resulting oscillatory current A current that alternates peri-
from changes in temperature, supply current or odically, particularly the current in an induc-
voltage, or component parameters. tance-capacitance (LC) tank circuit that results
503
oscillatory current • out of phase


from the oscillation of energy back and forth be- OTL Abbreviation of OUTPUT-TRANSFORMER-
tween the inductor and capacitor. LESS.
oscillatory discharge An electrical discharge, O-type backward-wave oscillator Abbreviation,
such as that of a capacitor, that sets up an OS- OBWO. A backward-wave oscillator using har-
CILLATORY CURRENT. monics having opposing phases.
ounce Abbreviation, oz. A unit of weight equal to 1„16
oscillatory surge A current or voltage surge that
includes both positive and negative excursions. pound or 28.35 grams.
oscillatory transient See OSCILLATORY SURGE. ounce-inch Abbreviation, oz-in. A unit of torque
oscillistor A device consisting essentially of a bar equal to the product of a force of 1 ounce and a
of semiconductor material positioned in a mag- moment arm of 1 inch. Compare POUND-FOOT.
netic field; it will produce oscillations under cer- outage 1. Loss of power to a system. 2. Loss of a
tain conditions. received signal.
oscillogram 1. The image produced on the screen outboard components 1. Discrete components
of an oscilloscope. 2. A permanent, usually pho- (capacitors, coils, resistors, or transformers) con-
tographic, record made from the screen of an os- nected externally to an integrated circuit. 2. Dis-
cilloscope. crete components connected externally to any
oscillograph 1. An instrument that makes a per- existing electronic device.
manent record (photograph or pen recording) of a outcome In statistical analysis, the result of an ex-
rapidly varying electrical quantity. Also called periment or test. An outcome can be numerical or
recorder (see RECORDER, 2). Compare OSCILLO- nonnumerical.
SCOPE. 2. An obsolete term for OSCILLOSCOPE. outdoor antenna An antenna erected outside,
oscillograph recorder A direct-writing recorder usually high above the surface of the earth clear
(see RECORDER, 2). of obstacles. It generally provides superior perfor-
oscillography The use of a graphic oscillation mance compared with an INDOOR ANTENNA.
recorder (OSCILLOGRAPH). Also reduces the probability of radio-frequency
oscillometer A device used for determining the interference (RFI) when used for transmitting.
peak amplitude of an oscillation. outdoor booster A signal preamplifier mounted on
oscilloscope An instrument that presents for an outdoor television receiving antenna for im-
visual inspection the pattern representing proved reception.
variations in an electrical quantity. Also see outdoor transformer A weatherproof distribution
CATHODE-RAY OSCILLOSCOPE. Compare OS- transformer installed outside the building it ser-
CILLOGRAPH. vices.
oscilloscope camera A special high-speed, short- outer conductor The outer metal cylinder or
focus camera with fixtures for attachment to an jacket of a coaxial cable or coaxial tank. Compare
oscilloscope to record images from the screen. INNER CONDUCTOR.
Standard and instant-film types are available. outgassing 1. In the evacuation of electronic de-
oscilloscope differential amplifier An amplifier vices, such as vacuum tubes, the removal of oc-
that processes the difference between two sig- cluded gases from glass, ceramic, and metal by
nals, for the purpose of displaying on an oscillo- means of slow baking and by flashing an internal
scope or oscillograph. metal getter (such as one of magnesium). 2. The
oscilloscope tube A cathode-ray tube for use in an production of gases in certain electrochemical
oscilloscope. It contains an electron gun, acceler- cells and batteries during the final stage of charg-
ating electrode, horizontal and vertical deflecting ing.
plates, and a fluorescent screen. outgoing line A power or signal line that leaves a
Os-Ir Symbol for OSMIRIDIUM. device, facility, or stage. Compare INCOMING
OSI-RM Abbreviation of OPEN SYSTEMS INTER- LINE.
CONNECTION REFERENCE MODEL. outlet A female receptacle that delivers a signal or
OSL Abbreviation of orbiting space laboratory. operating power to equipment plugged into it.
osmiridium Symbol, Os-Ir. A natural alloy of os- outline flowchart In computer operations, a pre-
mium and iridium. liminary flowchart showing how a program will be
osmium Symbol, Os. A metallic element of the divided into routines and segments, input and
platinum group. Atomic number, 76. Atomic output functions, program entry points, etc.
weight, 190.2. out-of-line coding Instructions for a computer
osmotic pressure The force that causes the posi- program routine stored in an area of memory
tive ions to pass out of a solution toward a metal other than that in which the routine™s program is
body immersed in an electrolyte. Also see stored.
HELMHOLTZ DOUBLE LAYER. out of phase Pertaining to the condition in which
OSO Abbreviation of orbiting solar observatory. the alternations or pulsations of two or more sep-
osteophone A bone-conduction hearing aid. arate waves or wave phenomena, having identical
OTA Abbreviation of OPERATIONAL TRANSCON- frequencies, are out of step with each other. Com-
DUCTANCE AMPLIFIER. pare IN PHASE.
504 out-of-phase current • output coupling transformer


on the oscillator frequency or signal amplitude.
2. An amplifier, usually with a voltage gain of 6 dB,
that follows a video multiplexer. The amplifier
drives a coaxial transmission line.
output bus driver In a computer, a device that
amplifies output signals sufficiently to provide
signals to other devices without undue loading of
the supply line (bus).
output capability The maximum power or voltage
output that a circuit can deliver without distor-
tion or other improper operating conditions.
output capacitance Symbol, Co. The internal ca-
pacitance of a circuit or device, as seen at the
output terminals. Compare INPUT CAPACI-
TANCE.
output capacitive loading For an operational am-
plifier at unity gain, the maximum capacitance
that can be connected to the output of the ampli-
fier before phase shift increases to the point of os-
out of phase
cillation.
output capacitor 1. In a capacitance-coupled cir-
out-of-phase current Reactive current in an alter- cuit, the output coupling capacitor. Compare IN-
nating-current circuit (i.e., current that is out of PUT CAPACITOR. 2. The last capacitor in a
phase with voltage. Also see QUADRATURE CUR- power-supply filter circuit.
RENT). output capacity The maximum output capability
out-of-phase voltage Voltage across a reactance; so of a device or system expressed in appropriate
called because it is out of phase with the current. units, such as current, voltage, power, torque,
outphaser A device that converts a sawtooth wave horsepower, etc.
to a square wave. It is used in electronic organs output choke The last choke (inductor) in a
and synthesizers. power-supply filter circuit.
outphasing modulation A system of modulation
in which the sideband frequencies are shifted
Output choke
90 degrees from the phase position in an ampli-
tude-modulated wave. The resulting constant- L1 L2
envelope wave is then amplified with high
C2
C1 Output
efficiency and low distortion by a class-C stage; Input
then the signal is reconverted to an amplitude-
modulated one by phase shifting the carrier, with
respect to the sidebands.
out-plant system A data-processing system in output choke
which a central computer receives data from re-
mote terminals.
output 1. Energy or information delivered by a output circuit The circuit or subcircuit that con-
circuit, device, or system. Compare INPUT, 1. 2. stitutes the output portion of a network or device.
The terminals at which energy or information is Also see OUTPUT and OUTPUT TERMINALS.
taken from a circuit, device, or system. Compare Compare INPUT CIRCUIT.
INPUT, 2. output-circuit distortion Distortion in the output
output admittance Symbol, Yo. The internal ad- portion of a circuit or device (such as a transistor
mittance of a circuit or device, as “seen” at the or transformer), usually caused by an overload or
output terminals; the reciprocal of OUTPUT nonlinear response.
IMPEDANCE. Compare INPUT ADMITTANCE. output conductance Symbol, Go. The internal
output amplifier See FINAL AMPLIFIER. conductance of a circuit or device, as “seen” at
output area In a computer system, the portion of the output terminals. It is the reciprocal of OUT-
storage holding information for delivery to an out- PUT RESISTANCE. Compare INPUT CONDUC-
put device. Also called output block. TANCE.
output axis For a gyroscope that has received an output control 1. The gain control of an amplifier.
input signal, the axis around which the spinning 2. The level control of a variable power supply.
wheel precesses. output coupling capacitor See OUTPUT CAPACI-
output block See OUTPUT AREA. TOR.
output buffer 1. A circuit that follows an oscillator output coupling transformer See OUTPUT
and reduces the effects of variable load impedance TRANSFORMER.
505
output current • output transformer


output current 1. Symbol, Io. The current deliv- output offset In an integrated circuit, the voltage
ered by a source, such as a battery, generator, or at the output when the inputs are grounded.
amplifier. Compare INPUT CURRENT, 1. 2. Sym- output port The output terminal of a logic device.
bol, Io. Current flowing in the output leg or elec- output power Symbol, Po. The power deliverable by
trode of a circuit or device. Compare INPUT an amplifier, generator, or circuit. Also called
CURRENT, 2. power output. Compare INPUT POWER.
output device 1. A load device, such as a resistor, output-power meter A type of direct-reading
loudspeaker, lamp, relay, motor, etc., that uti- wattmeter for measuring the power output of an
lizes the output energy delivered by a generator, amplifier or generator.
amplifier, or network. 2. A device, such as an out- output regulator A circuit or device that automat-
put transformer, that serves to transfer energy or ically maintains the output of a power supply or
information from a circuit or device. Compare IN- signal source at a constant amplitude.
PUT DEVICE. 3. In computer operations, a device output resistance Symbol, Ro. The internal resis-
that presents the results of computer operation tance of a circuit or device, as “seen” at the out-
in a comprehensible form. Examples: printer, put terminals. Compare INPUT RESISTANCE.
monitor, disk drive, tape drive, modem, etc. output routine In computer operations, a routine
output efficiency The efficiency of a device, such (program segment) that performs the work in-
as a generator or amplifier, in delivering an out- volved in moving data to an output device, often
put signal. For an amplifier, the efficiency (Eff%) is including intermediate transferals and modifying
given as a percentage by the formula Eff% = the data as necessary.
100Po/Pi, where Pi is the direct-current power in- output section See OUTPUT AREA.
put, and Po is the alternating-current (signal) output sink current In an integrated circuit, for a
power output. specified set of conditions at the input and out-
output equipment See OUTPUT DEVICE, 3. put, current into the output as measured in mil-
output filter The direct-current filter of a power liamperes or microamperes.
supply operating from alternating current. Also output source current In an integrated circuit, for
see CAPACITOR-INPUT FILTER and CHOKE- a specified set of conditions at the input and out-
INPUT FILTER. put, the current out of the output, as measured
output gap A device via which current or power is in milliamperes or microamperes.
intercepted from an electron beam in a beam- output stage The last stage of an amplifier. Deliv-
power tube. ers the signal to the load.
output impedance Symbol, Zo. The impedance output terminals Terminals (usually a pair) asso-
“looking” into the output terminals of an ampli- ciated with the output of a circuit or device (see
fier, generator, or network. Compare INPUT OUTPUT, 1, 2). Compare INPUT TERMINALS.
IMPEDANCE. output tank In a transmitter or power generator, a
output indicator A device, such as an analog me- parallel-tuned combination of inductance and ca-
ter, digital meter, or bar-graph meter, that pro- pacitance in the collector, drain, or plate circuit,
vides a visual indication of the output-signal that is generally tuned to resonance at the oper-
amplitude of an equipment. ating frequency. IT optimizes efficiency and cou-
output leakage current In an open-collector inte- ples the signal to the load. Compare INPUT TANK.
grated circuit, the current from collector to emit- output transformer The output-coupling trans-
ter with the output in the “off” condition and a former that delivers signal voltage or power from
certain specified voltage applied to the device. It an amplifier, generator, or network to a load or to
can be expressed in milliamperes or microam- another circuit. Compare INPUT TRANSFORMER.
peres.
output limiting A process for automatically main-
+
taining the amplitude of the signal delivered by a
Output
generator or amplifier. See, for example, AUTO-
tank
MATIC GAIN CONTROL, AUTOMATIC MODULA-
TION CONTROL, VOLUME COMPRESSION, and
VOLUME LIMITER.
Output
output load See OUTPUT DEVICE, 1.
output load current 1. The current through the
Input
output load of an amplifier. Generally, this cur-
rent is expressed in root-mean-square (rms) form.
2. The highest rms current that an amplifier can
deliver to a load of a specified impedance.
output meter A meter that gives a quantitative or
+
qualitative indication of the output of an amplifier
or generator. See, for example, OUTPUT-POWER
METER. output tank
506 output-transformerless • overdesign


output-transformerless Abbreviation, OTL. Per- overall gain The total gain of an entire system
taining to an oscillator, amplifier, or generator (such as a multistage amplifier), as opposed to
that requires no output coupling transformer. that of one or several stages.
output transistor A transistor in the final stage of overall loudness The apparent intensity of an
an amplifier or generator; usually, it is a power acoustic disturbance, generally measured with
transistor. respect to the threshold of hearing, and ex-
output tube A vacuum tube in the final stage of an pressed in decibels, relative to the threshold level.
amplifier or generator; usually, it is a power tube. overbiased unit A component, such as a transis-
output unit See OUTPUT DEVICE. tor or vacuum tube, whose bias current or voltage
output voltage 1. Symbol, Eo or Vo. The voltage de- is higher than the correct value for a given mode
livered by a source, such as a battery, generator, of operation. Compare UNDERBIASED UNIT.
or amplifier. Compare INPUT VOLTAGE, 2. 2. overbunching In a velocity-modulated tube, such
Symbol, Eo or Vo. The voltage across the output as a Klystron, the condition in which the buncher
leg or electrode of a circuit or device. Compare IN- voltage exceeds the value required for optimum
PUT VOLTAGE, 2. bunching.
output voltage compliance In an integrated cir- overcharging In a secondary cell or battery, the
cuit, the voltage range over which the output can application of charging current longer than nec-
be made to swing, while keeping the operation of essary to obtain full charge. This can sometimes




Y
the circuit within a certain maximum allowable cause problems, such as cell heating.
nonlinearity limit. It is measured in volts or milli- overcompounded generator A dynamo-type gen-




FL
volts. erator having a compound field winding in which
output voltage noise In an integrated circuit, the the series-field winding increases the field inten-
output noise over a given range of frequencies, as sity beyond the point needed to maintain the out-
measured in peak-to-peak millivolts or micro- put voltage. Compare UNDERCOMPOUNDED
AM
volts. It can also be measured as the root- GENERATOR.
mean-square (rms) value. overcompounding A characteristic of electrome-
output voltage swing In an integrated circuit with chanical motors, resulting in increased running
a specified load, the output-voltage change mea- speed with decreasing load resistance.
sured as a difference between maximum and overcoupled transformer A transformer having
TE

minimum in volts or millivolts. greater than critical coupling between its primary
output voltage tracking For an integrated-circuit and secondary windings. In tuned circuits, such
dual regulator, the difference between the abso- as intermediate-frequency (IF) transformers, this
lute values of the output voltages of a dual regu- produces a double-peak response.
lator. It can be expressed as a specific voltage or overcoupling Extremely close coupling (see
as a percentage of the specified output voltage of CLOSE COUPLING).
the device. overcurrent A current greater than the specified,
output winding The secondary coil of an output nominal, or desired level. Compare UNDERCUR-
transformer. RENT.
outside antenna See OUTDOOR ANTENNA. overcurrent circuit breaker A circuit breaker that
outside booster See OUTDOOR BOOSTER. opens when current exceeds a predetermined
outside diameter Abbreviation, OD. The outer- value.
most diameter of a body or figure having two con- overcurrent protection The use of a circuit
centric diameters (e.g., tubing or conduit). breaker, relay, or other device to protect a circuit
Compare INSIDE DIAMETER. or system from damage resulting from an exces-
outside lead See FINISH LEAD. sive flow of current.
outside transformer 1. See OUTDOOR TRANS- overcurrent relay A protective relay that opens a
FORMER. 2. A transformer mounted outside of circuit when current exceeds a predetermined
an equipment in whose circuit it is included. value. Compare UNDERCURRENT RELAY.
External mounting can eliminate hum in the overcutting In disc recording, the condition in
equipment circuit, and can help to prevent which an excessively high amplitude signal
overheating. causes the stylus to cut through the wall between
oven 1. Also called crystal oven. A chamber provid- adjacent grooves. Compare UNDERCUTTING.
ing a closely controlled operating temperature for overdamping Damping greater than the critical
an electronic component, such as a quartz crys- value (see DAMPING ACTION, 2). Compare UN-
tal. 2. An enclosure in which electronic equip- DERDAMPING.
ment can be tested at selected, precise high overdesign Also called overengineering. 1. To use
temperatures. Compare COLD CHAMBER. an unnecessarily high safety factor in the design
overall feedback Positive or negative feedback of equipment. 2. To design equipment for perfor-
around an entire system (such as a public- mance superior to that which is required in the
address system), as opposed to feedback confined intended application. 3. A design that results
to one stage or a few stages within the system. from operations defined in 1 and 2.




Team-Fly®
507
overdrive • overload recovery time


overdrive In an analog amplifier, an undesirable as missile launchings from thousands of miles
operating condition that occurs with the applica- away.
tion of excessive input signal voltage or power. over-horizon transmission See FORWARD SCAT-
This results in increased distortion, nonlinearity, TER.
excessive harmonic generation, and excessive overinsulation Use of excessive insulation for a
output signal bandwidth. In a high-fidelity audio particular application. Compare UNDERINSULA-
system, such a condition grossly degrades the TION.
quality of the sound. The amplifying device (tran- over insulation The insulation (usually a strip of
sistor or vacuum tube) is in or near saturation tape) laid over a wire brought up from the center
during part of the signal cycle. This reduces the of a coil. Compare UNDER INSULATION.
efficiency of the circuit, can cause excessive col- overlap 1. The time during which two successive
lector, drain, or plate current, and can overheat operations are performed simultaneously. 2. In a
the base“collector (B-C) junction of a bipolar facsimile or television system, a condition in which
transistor. In the worst case, it can destroy the the scanning line is wider than the center-to-
component. center separation between adjacent scanning lines.
overdriven amplifier See OVERDRIVEN UNIT. overlap radar A long-range radar situated in one
overdriven unit An amplifier, oscillator, or trans- sector and covering part of another sector.
ducer whose driving signal (current, voltage, overlay 1. A sheet of transparent or translucent
power, or other quantity) is higher than that material laid over a schematic diagram for the
which the device can properly or efficiently han- purpose of tracing connections that have been
dle for correct or intended operational perfor- made in wiring an equipment from the diagram.
mance. 2. In computer operations, a method whereby the
overdub In audio recording, a method of combin- same internal storage locations are used for dif-
ing two or more signals onto a single tape track. ferent parts of a program during a program run.
For example, a live voice can be recorded on a It is used when the total storage requirements for
tape containing pre-recorded music. instructions exceed the available main storage
overexcited Receiving higher than normal excita- capacity.
tion, as in radio-frequency amplifiers or alternat- overlay transistor A double-diffused epitaxial
ing-current generators. transistor having separate emitters connected to-
overflow 1. In computer or calculator operation, gether by means of diffusion and metallizing to
the condition in which an arithmetic operation increase the edge-to-area ratio of the emitters.
yields a result exceeding the capacity of the loca- This design raises the current-handling ability of
tion or display for a result. 2. The carry digit that the transistor. Also see DIFFUSED TRANSISTOR
results from the condition described in (1). and EPITAXIAL TRANSISTOR.
overflow indicator 1. In a digital calculator, a dis- overload 1. Current or power drain in excess of the
play that indicates that a numerical value is too rated output of a circuit or device. 2. An excessive
large or too small to be shown with the available driving signal.
number of decimal places. 2. In data processing, overload circuit breaker See CIRCUIT BREAKER.
a display that indicates the presence of too many overloaded amplifier A power amplifier deliver-
bits or characters for the available storage ing excessive output power. Compare UNDER-
capacity. LOADED AMPLIFIER, 2.
overflow position In a digital computer, an auxil- overloaded oscillator An oscillator from which
iary register position for developing the overflow excessive power is drawn, causing instability,
digit (see OVERFLOW, 1, 2). frequency shift, lowered output voltage, and
overflow record In data processing, a record that overheating.
will not fit the storage area allotted for it, and that overload indication Any attention-catching
must be kept where it can be retrieved, according method, such as an audible or visual alarm, for
to some reference stored in its place. warning that a prescribed signal or power level
overflow storage In a calculator or computer, ex- has been exceeded.
tra storage space, allowing a small amount of overload level The amount of overload that can
overflow without loss of accuracy. safely be applied to an equipment (see OVER-
overhanging turns The turns in the unused por- LOAD, 1).
tion(s) of a tapped coil. overload protection The use of circuit breakers,
overhead line A power or transmission line sus- relays, automatic limiters, and similar devices to
pended above the ground between poles or tow- protect equipment from overload damage by re-
ers. ducing current or voltage, disconnecting the
over-horizon radar A form of radar used at high power supply, or both.
frequencies, in which pulses are transmitted and overload recovery time Following an overdrive at
received. The signals are returned to earth via the the input of an integrated-circuit device, the time
ionosphere, both in the forward and reflected di- required for the output to resume its normal
rections, making it possible to detect such things characteristics.
508 overload relay • oxidation-reduction potential


overload relay A relay actuated when circuit cur- Overshoot




Relative amplitude
rent exceeds a predetermined value. Compare
UNDERLOAD RELAY.
overload time The maximum length of time that
an equipment can safely be subjected to an over-
load level of current.
overmodulation Modulation in excess of a pre-
scribed level”especially amplitude modulation
Time
greater than 100%. Compare COMPLETE MODU-
LATION and UNDERMODULATION.
overshoot

overtone crystal A piezoelectric quartz crystal
that oscillates at odd multiples of the frequency
for which it was cut. This allows crystal operation
at frequencies otherwise obtainable only from a
fundamental-frequency crystal ground so thin as
Carrier level




to be prohibitively fragile.
overtone oscillator A crystal oscillator using an
Time OVERTONE CRYSTAL.
overtravel See OVERSHOOT, 2.
overvoltage A voltage higher than a specified or
rated value. Compare UNDERVOLTAGE.
overvoltage circuit breaker A circuit breaker that
opens when voltage exceeds a predetermined
value.
overvoltage protection The use of a special cir-
cuit or device to protect equipment from excessive
overmodulation voltage. When voltage increases beyond the over-
voltage limit, the protective circuit causes shut-
down.
overmodulation alarm See OVERMODULATION
overvoltage relay A relay actuated when voltage
INDICATOR.
rises above a predetermined value. Compare UN-
overmodulation indicator A device, such as a
DERVOLTAGE RELAY.
neon bulb, incandescent lamp, light-emitting
overwrite In computer operations, to record new
diode, analog meter, or digital meter, adapted to
data over existing data (e.g., to update the files on
give an alarm when the modulation percentage of
a magnetic disk or tape).
a signal exceeds a predetermined value.
Ovshinsky effect In thin-film solid-state devices,
overpotential See OVERVOLTAGE.
the tendency for switches to have the same char-
overpower relay A relay actuated by a rise in
acteristics for currents in either direction.
power above a predetermined level. Compare UN-
O wave One (the ordinary) of the pair of components
DERPOWER RELAY.
into which an ionospheric radio wave is divided by
overpressure For a pressure transducer, pressure
Earth™s magnetic field. Compare X WAVE.
in excess of the maximum rating of the device.
Owen bridge A wide-range four-arm bridge that
override 1. To intentionally circumvent an auto-
measures inductance in terms of a standard ca-
matic control system. 2. To bridge a functional
pacitance and bridge-arm resistances.
stage of a system.
own coding Additional program steps added to
overscanning The deflection of the beam of a cath-
vendor-supplied software so that it can be modi-
ode-ray tube beyond the edges of the screen.
fied to fit special needs.
overshoot 1. The momentary increase of a quan-
ox Abbreviation of OXYGEN.
tity beyond its normal maximum value (e.g., the
oxidation 1. The combination of a substance with
spike sometimes seen on a square wave because
oxygen. Generally a slow process, such as the
of the overswing of a rising voltage). 2. Momen-
corrosion of iron or aluminum in the atmosphere.
tary overtravel of the pointer of an analog meter.
The process is accelerated by the presence of
overswing See OVERSHOOT, 2.
moisture and/or high temperatures. 2. The loss
overtemperature protection The use of an auto-
of electrons from a cell or battery during dis-
matic device, such as a thermal relay or thermo-
charge.
stat, to disconnect a device from the power
oxidation-reduction potential The potential at
supply when the device™s temperature becomes
which oxidation occurs at the anode of an elec-
excessive.
trolytic cell, and at which reduction occurs at the
overthrow See OVERSHOOT, 2.
cathode.
overtone See HARMONIC.
509
oxide-coated cathode • ozone monitor


oxide-coated cathode See OXIDE-COATED EMIT- oxygen recombination In nickel-cadmium (NICAD)
TER. cells and batteries, a process in which oxygen is
oxide-coated emitter An electron-tube cathode or generated in the vicinity of the positive electrode,
filament coated with a material, such as thorium and is reduced with water in the vicinity of the
oxide, for increased electron emission at low negative electrode. This produces battery heating.
emitter temperatures. oz 1. Abbreviation of OUNCE. 2. Abbreviation of
oxide-coated filament See OXIDE-COATED OZONE.
EMITTER. oz-in Abbreviation of OUNCE-INCH.
oxide film 1. The thin film of iron oxide that con- ozocerite An insulating mineral wax. Dielectric
stitutes the recording surface of a magnetic disk constant, 2.2. Dielectric strength, 4 to 6 kV/mm.
or tape. 2. The layer of copper oxide formed on Also spelled OZOKERITE.
the copper plate of a copper-oxide rectifier. ozone Symbol, O3. An allotropic form of oxygen. Its
oxide-film capacitor An electrolytic capacitor, so formula indicates that each molecule has three
called because the dielectric is a thin oxide film. atoms. Produced by the action of ultraviolet rays
oxide rectifier A solid-state rectifier using a junc- (or electrical discharge) on oxygen, its character-
tion between copper and copper oxide. Also called istic odor (somewhat like weak chlorine) can often
COPPER-OXIDE RECTIFIER. be detected around sparking contacts or in the
oximeter A photoelectric instrument for measur- air after a thunderstorm.
ing the oxygen content of the blood. It operates by ozone layer In the earth™s atmosphere, a layer of
passing visible light through the earlobe, and an- ozone gas in the upper troposphere and lower
alyzing the color and intensity of the emerging stratosphere. It is produced by ultraviolet
beam. Also called ANOXEMIA TOXIMETER. radiation from space, mainly from the sun. The
oxygen Symbol, O. Abbreviation, O2. A gaseous el- ozone layer tends to block ultraviolet radiation,
ement. Atomic number, 8. Atomic weight, 15.999. reducing the amount that reaches the surface of
Constitutes 21% of Earth™s atmosphere. It readily the earth.
combines with various elements to form com- ozone monitor An instrument for measuring the
pounds (see OXIDATION). concentration of ozone in the atmosphere. One
oxygen analyzer An electronic gas analyzer de- version measures the extent to which ultraviolet
signed especially to measure oxygen content. The radiation is absorbed by a sample of air; the
operation of this instrument is based on the para- greater the absorption, the higher the ozone con-
magnetic properties of oxygen. centration in the sample.
P 1. Symbol for POWER. 2. Symbol for PLATE (of a electronic equipment, or to design a housing for
vacuum tube). 3. Symbol for PHOSPHORUS. 4. it, in accordance with good engineering tech-
Abbreviation of PRESSURE. 5. Symbol for PRI- niques. 3. A computer program of general use for
MARY. 6. Abbreviation for prefix PETA-. 7. Sym- an application (e.g., payroll package).
bol for PERMEANCE. 8. Abbreviation of POINT. package count The number of discrete packaged
p 1. Abbreviation of prefix PICO-. 2. Subscript for circuits in a system.
PEAK. 3. Abbreviation of POUND. 4. Abbreviation packaging density 1. See VOLUMETRIC EFFI-
of POINT (often capitalized). 5. Subscript for PRI- CIENCY. 2. Computer storage capacity in terms
MARY. 6. Subscript for PLATE (of a vacuum of the number of information units that can be
tube). 7. Abbreviation of PITCH. 8. Abbreviation contained on a given segment of a magnetic
of PER. medium. Also called PACKING DENSITY. 3.
PA 1. Abbreviation of POWER AMPLIFIER. 2. Ab- Within a given integrated circuit, the capacity in
breviation of PULSE AMPLIFIER. 3. Abbreviation terms of the number of active devices that can be
of particular average. 4. Abbreviation of pilotless contained on a single silicon chip.
aircraft. (Also, P/A.) 5. Abbreviation of PUBLIC packet 1. A unit of digital information in PACKET
ADDRESS (as in PA system). COMMUNICATIONS. It consists of a header fol-
Pa 1. Symbol for PROTACTINIUM. 2. Symbol for lowed by a certain number of data bits or bytes.
PASCAL. 2. See WAVE PACKET. 3. See PACKET COMMU-
pA Abbreviation of PICOAMPERE. NICATIONS. 4. See PACKET RADIO.
pacemaker See CARDIAC STIMULATOR. packet communications A method via which data
pacer See CARDIAC STIMULATOR. is exchanged through a network between or
Pacific Standard Time Abbreviation, PST. Local among people or computers. Information is sent
mean time at the 120th meridian west of Green- and received in blocks of information called
wich. Also see GREENWICH MEAN TIME, STAN- packets. Each packet is routed individually
DARD TIME, TIME ZONE, and COORDINATED through the network according to the most effi-
UNIVERSAL TIME. cient possible path at the time of its transit. At
pack A technique for maximizing a computer mem- the destination, the packets are reassembled into
ory device™s storage capacity, wherein more than the original signal. This scheme makes more effi-
one information item is stored in a single storage cient use of network resources than continuous-
unit. Also called crowd. connection or single-path methods. However,
package 1. The enclosure for an electronic device when network usage is heavy, there can be a de-
or system. This includes a wide range of hous- lay in the arrival of a sufficient number of packets
ings, from the simple encapsulation of miniature to produce an intelligible received signal.
transistors to forced-air-cooled enclosures for packet radio The transmission and reception of
heavy power units. 2. To assemble and house an PACKET COMMUNICATIONS data via radio.


Copyright © 2001 by The McGraw-Hill Companies, Inc.
Click here for Terms of Use.
511
packet switching • panel meter


packet switching In telephony, a method of con- page A display of text data on a computer display
nection in which data is exchanged between sub- that completely fills the screen.
scribers by splitting the data into units (packets). page printer A computer peripheral that prints a
Each packet is sent over the optimum path at the message in lines on a page, according to an es-
time of transmission. The signal path can, and tablished format, rather than in a single line.
usually does, vary from packet to packet. At the pager 1. A public-address system used for sum-
destination, the packets are reassembled into the moning purposes. 2. See BEEPER, 2.
original singal. The connection is in effect nonex- page turning The successive display of pages (see
istent during periods of silence (no data transmit- PAGE).
ted by either subscriber). Compare CIRCUIT pair 1. Two wires, especially two insulated conduc-
SWITCHING. tors in a cable. 2. A set of two particles or charge
packing In the button of a carbon microphone, carriers (e.g., electron-hole pair). 3. A set of two
bunching and cohesion between the carbon gran- transistors or vacuum tubes, operating together
ules. in push-pull or parallel in a power amplifier.
packing density The number of discrete package paired cable A cable consisting of separate twisted
circuits within a given surface area or volume. pairs of conducting wires.
packing factor 1. See VOLUMETRIC EFFICIENCY. paleomagnetism The study of certain rocks and
2. In computer operations, the number of bits minerals to determine the nature of the earth™s
that can be recorded in a given length of magnetic magnetic field at the time the rocks were formed.
memory surface. Also called PACKING DENSITY. When the age of the rock is determined by means
pack transmitter A portable transmitter that can of radioactive dating, and numerous rock sam-
be strapped to the operator™s back. ples are found covering many different eras, the
pack unit A portable transceiver that can be nature of the earth™s magnetic field can be
strapped to the operator™s back or carried on an graphed over time.
animal™s back. palladium Symbol, Pd. A metallic element of the
PACM Abbreviation of pulse-amplitude code modu- platinum group. Atomic number, 46. Atomic
lation. weight, 106.42.
pad 1. An attenuator network (usually a combina- palletizing In industrial robots, the automatic
tion of resistors) that reduces the amplitude of a placing of objects in a tray according to a com-
signal by a desired amount while maintaining puter program.
constant input and output impedance. 2. In com- Palm See HANDHELD COMPUTER.
puter operations, to make a record a fixed size by Palmer scan In radar, a method of simultaneously
adding blanks or dummy characters to it. 3. To scanning the azimuth and the elevation.
lower the frequency of an inductance-capacitance PalmPilot See HANDHELD COMPUTER.
(LC) circuit by adding capacitance to an already palmtop computer See HANDHELD COMPUTER.
capacitively tuned network. PAM Abbreviation of PULSE-AMPLITUDE MODU-
padder See OSCILLATOR PADDER. LATION.
padding capacitor See OSCILLATOR PADDER. Pan In radiotelephony, a spoken word indicating
padding character In a digital communications sys- that an urgent message is to follow. It is equiva-
tem, a character that is inserted solely for the pur- lent to the XXX of radiotelegraphy.
pose of consuming time while no meaningful pan 1. To make a panoramic sweep [e.g., to sweep
characters are sent. The insertion of such charac- a wide area with a beam (as from an antenna), or
ters maintains the synchronization of the system. to sweep a wide band of frequencies with a suit-
paddle-handle switch A toggle switch the lever of able tuning circuit]. 2. A panoramic sweep made
which is a flattened rod. Compare BAT-HANDLE as defined in 1. 3. In audio engineering, to grad-
SWITCH, ROCKER SWITCH, and SLIDE SWITCH. ually shift from one audio channel to another or
PADT Abbreviation of POST-ALLOY-DIFFUSED from one reproducer to another.
TRANSISTOR. pan and tilt 1. An azimuth-elevation mounting for
a television camera. 2. The simultaneous move-
ment of a television camera in the vertical and
horizontal directions.
pancake coil See DISK WINDING.
panel A flat surface on which are mounted the con-
trols and indicators of an equipment, for easy ac-
cess to the operator.
panel lamp 1. See ELECTROLUMINESCENT
PANEL. 2. See PANEL LIGHT.
panel light A pilot light for illuminating the front
panel of a piece of equipment.
panel meter A usually small meter for mounting
on, or through an opening in, a panel.
paddle-handle switch
512 panic button • parallel capacitors


panic button In a security system, a button or and a fixed straight line (the directrix). In the
switch that immediately triggers an alarm when it Cartesian xy-plane, the general equation is y =
is closed. ax2 + b, where a and b are constants.
panoramic adapter An external device that can be parabola control See VERTICAL-AMPLITUDE
connected to a receiver to sweep a frequency CONTROL, 2.
band and indicate carriers on the air as pips on a parabola generator A circuit for generating a
screen at the corresponding frequency points. parabolic-waveform signal.
Also called pan adapter. parabolic microphone A directional microphone
panoramic display 1. A wide-angle display. 2. A mounted at the principal focus of a parabolic
spectrum-analyzer display that shows a wide sound reflector; the front of the microphone faces
range of frequencies, from zero to well above the the inside of the parabola. It is useful for detect-
maximum frequency in the monitored system. ing sounds from great distances.
panoramic radar An omnidirectional radar (i.e., parabolic reflector Also called paraboloidal reflec-
one that transmits wide-beam signals in all direc- tor. A reflector having the shape of a paraboloid.
tions without scanning). It is particularly useful for focusing or directing
panoramic receiver A receiver that displays pips radiation. For example, if a radiator, such as an
on a screen to show carriers on the air in a given antenna rod, is placed at the focus of the
frequency band. All frequencies in the band are paraboloid, a beam of parallel rays will be emitted
presented along the horizontal axis of the screen. by the reflector.
panpot A potentiometer with which panning can paraboloid The surface generated by a PARABOLA
be achieved (see PAN, 3). rotated about its axis of symmetry.
pan-range A form of radar display in which target paraffin A relatively inexpensive, easily available,
motion can be ascertained. solid, white petroleum wax. At one time, it was
pantography The transmission of radar information used to impregnate capacitors and coils and to
to a distant location for observation or recording. waterproof paper used for insulating purposes.
Papa Phonetic alphabet code word for the letter P. parallax The apparent shift in the position of a rel-
paper advance mechanism In a data-processing atively nearby object when the observer moves or
system, the part of a printer that moves (some- alternately blinks either eye. Thus, a pointer-type
times by computer control) the paper through the meter will seem to give different readings when
printer. viewed from different angles. Some meters have
paper capacitor A component that is made by mirrored scales to eliminate this effect.
placing paper, soaked with mineral oil, between parallel 1. Pertaining to the type of operation in a
two strips of foil. The assembly is rolled up, and computer when all elements in an information
wire leads are attached to the two pieces of foil. item (e.g., bits in a word) are acted upon simulta-
Finally, the rolled-up foil and paper are enclosed neously, rather than serially (one at a time).
in a cylindrical case. These components are 2. The condition in which two comparably sized
sometimes found in radio-frequency (RF) elec- objects or figures are equidistant at all facing
tronic equipment. They have values ranging from points. 3. Pertaining to the shunt connection of
about 0.001 microfarads (µF) to 0.1 µF, and can components or circuits.
handle low to moderate voltages, usually up to parallel access In computer operations, inputting
about 1000 volts. Compare CERAMIC CAPACI- or outputting data to or from storage in whole el-
TOR, ELECTROLYTIC CAPACITOR, MICA ements of information items (a word, rather than
CAPACITOR, PLASTIC-FILM CAPACITOR, a bit at a time, for example).
TANTALUM CAPACITOR. parallel adder In a computer or calculator, an
PAR Abbreviation of PRECISION APPROACH adder in which corresponding digits in multibit
RADAR. numbers are added simultaneously. Also see
par Abbreviation of PARALLEL. PARALLEL, 1.
parabola A plane curve that is the locus of points parallel antenna tuning Antenna-feeder tuning in
that are equidistant from a fixed point (the focus) which the tuning capacitor is connected in paral-
lel with the two feeder wires. Compare SERIES
ANTENNA TUNING.
parallel arithmetic unit See PARALLEL ADDER.
parallel capacitance 1. A capacitance connected
in parallel (shunt) with some other component.
2. The capacitance between the turns of a coil.
Foil
Also see DISTRIBUTED CAPACITANCE.
Paper
parallel capacitors Two or more capacitors con-
Foil nected in parallel (shunt) with each other. The
Paper total capacitance is equal to the sum of the
individual capacitances. Also see PARALLEL
CIRCUIT.
paper capacitor
513
parallel circuit • parallel operation


parallel circuit A circuit in which the components Positive limiting
are connected across each other (i.e., so that the
circuit segment could be drawn showing compo-
nent leads bridging common conductors as rungs
would across a ladder). Compare SERIES CIR-
0 0
CUIT.
vin vout
parallel-component amplifier An amplifier stage
in which the active devices (transistors or vac-
uum tubes) are connected in parallel with each
other for increased power output. Also see PAR-
ALLEL CIRCUIT.
parallel-component oscillator An oscillator stage
in which transistors are connected in parallel
with each other for increased power output. Also Negative limiting
see PARALLEL CIRCUIT.
parallel computer A computer equipped to handle
more than one program at a time, but not
through the use of multiple programming or
0
0
time-sharing.
vin vout
parallel-cut crystal See Y-CUT CRYSTAL.
parallel-diode half-wave rectifier See PARALLEL
LIMITER.
parallel-fed amplifier An amplifier circuit in which
the direct-current operating voltage is applied in
parallel with the alternating-current output volt-
parallel limiter
age. Also see PARALLEL FEED.
parallel-fed oscillator An oscillator circuit in
which the direct-current operating voltage is ap- parallel-line tuning At ultra-high frequencies
plied in parallel with the alternating-current out- (UHF) and microwave frequencies, the use of two
put voltage. Also see PARALLEL FEED. parallel wires or rods for tuning. A straight short-
parallel feed 1. The presentation of parallel alter- circuiting bar is slid along the wires to accom-
nating-current (ac) and direct-current (dc) volt- plish tuning.
ages to a device. 2. The presentation of a dc parallelogram A two-dimensional geometric figure
operating voltage in parallel with the ac output that has four sides. Opposite pairs of sides are par-
voltage of a device (as in a parallel-fed amplifier or allel. Opposite interior angles have equal measure.
oscillator). Also see SHUNT FEED.
parallel gap welding A welding technique using
x
two electrodes separated by a gap.
parallel gate circuit 1. A gate circuit using two
bipolar transistors with parallel-connected collec-
tors and emitters, and a common collector resis-
tor. The input signal is applied to one base, and
y y
the control signal to the other. 2. A gate circuit
using two field-effect transistors with parallel-
connected drains and sources, and a common
drain resistor. The input signal is applied to one
gate, and the control signal to the other.
parallel inductance An inductance connected in x
parallel (shunt) with some other component.
parallel inductors Inductors connected in parallel parallelogram
and separated or oriented to minimize the effects
of mutual inductance. Also see PARALLEL CIR-
parallelogram of vectors A graphic device for find-
CUIT.
ing the sum of two vectors. A parallelogram is
parallel inverse feedback In a single-ended audio
constructed for which the two vectors are adja-
amplifier circuit, a simple system for obtaining
cent sides. The sum of the vectors is represented
negative feedback: A high resistance is connected
by the diagonal of the parallelogram.
from the output-transistor collector or drain to
parallel operation In computer operations, the si-
the driver-transistor collector or drain.
multaneous transmission of all bits in a multibit
parallel limiter A limiter (clipper) circuit in which
word over individual lines, as compared with the
the diode is in parallel with the signal. Compare
serial transmission of a word bit by bit.
SERIES LIMITER.
514 parallel output • parallel-wire line


1/4
parallel output A digital output consisting of two Wavelength
or more lines, all of which carry data at the same
time.
parallel processing In computer operations, the
simultaneous processing of several different pro-
grams through separate channels. Compare
SERIAL PROCESSING. Input
parallel Q Symbol, Qp. The figure of merit of a par-
allel circuit of inductance, capacitance, and resis-
tance.
parallel resistance 1. A resistance connected in
Moveable
parallel (shunt) with some other component.
shorting bar
2. The resistance between the plates of a capacitor.
3. The resistance across a coil.
parallel resistors Resistors connected in parallel. parallel-rod tuning
If the individual resistances are represented by
R1, R2, R3, . . ., Rn, then total resistance Rt is
equal to 1/(1/R1 + 1/R2 + 1/R3 + . . . + 1/Rn). Also parallel-series Also called series-parallel. Pertain-
see PARALLEL CIRCUIT. ing to an arrangement of components, usually
parallel resonance Resonance in a circuit consist- similar (e.g., resistances), consisting of parallel
ing of a capacitor, inductor, and alternating- circuits connected in series with each other, or of
current source connected in parallel. At the series circuits connected in parallel with each
resonant frequency, the inductive reactance is other. Usually, the component values or ratings
equal in magnitude, but opposite in effect, to the are all identical, so currents and/or voltages are
capacitive reactance. The capacitor current and equally shared among them. Also see PARALLEL
inductor current are maximum, the line current CIRCUIT and SERIES CIRCUIT.
is minimum, and the circuit impedance is maxi- parallel-series capacitors Capacitors connected
mum. Compare SERIES RESONANCE. in PARALLEL-SERIES, usually to obtain higher
parallel-resonant circuit A resonant circuit in voltage and/or current ratings than an individual
which the capacitor, inductor, and alternating- capacitor can provide.
current source are connected in parallel. Com- parallel-series inductors Inductors connected in
pare SERIES-RESONANT CIRCUIT. PARALLEL-SERIES and separated or oriented to
parallel-resonant trap A wavetrap consisting of a minimize the effects of mutual inductance.
parallel-resonant inductance-capacitance (LC) parallel-series resistors Resistors connected in
circuit. Compare SERIES-RESONANT TRAP. PARALLEL-SERIES, usually to obtain a higher
power rating than an individual resistor can pro-
vide.
parallel storage In a computer, storage in which
all information items can be made available in the
same amount of time.
parallel-tee amplifier A bandpass amplifier hav-
ing a parallel-tee network in its negative-feedback
path. The null frequency of the network deter-
mines the pass frequency of the amplifier.
parallel-tee measuring circuit A parallel-tee net-
work used for measuring circuit constants. Also
called TWIN-TEE MEASURING CIRCUIT.
parallel-tee network A resistance-capacitance
parallel-resonant trap (RC) network containing two tee sections (with R
and C elements opposite in the tees) connected in
parallel-resonant wavetrap See PARALLEL- parallel. The network produces a null at one fre-
RESONANT TRAP. quency. Also called TWIN-T NETWORK.
parallel-rod oscillator An ultra-high-frequency parallel-tee oscillator A resistance-capacitance
(UHF) oscillator tuned by means of two straight, tuned oscillator having a parallel-tee network in
parallel quarter- or half-wave rods, one rod con- its negative-feedback path. The null frequency of
nected to the base or gate of a transistor, and the the network determines the oscillator frequency.
other rod connected to the collector or drain. parallel transfer A form of digital information
parallel-rod tuning Adjustment of the resonant fre- transfer, consisting of two or more lines that
quency of a section of open-wire transmission line. carry data at the same time.
A movable shorting bar allows quarter-wave reso- parallel-wire line A transmission line consisting of
nance. The impedance at resonance is very high. two parallel wires whose separation is kept
515
parallel-wire line • parasitic capacitance


constant by dielectric rods (open-wire line) or a paraphase inverter A single-transistor phase in-
solid dielectric web (ribbon line). verter in which the two out-of-phase output sig-
parallel-wire tank In an ultra-high-frequency nals are obtained by taking one output from the
(UHF) amplifier or oscillator, a resonant circuit collector or drain, and the other output from
consisting of two separate parallel wires con- the emitter or source. Thus, the 180-degree
nected to the transistor(s) or tube(s) at one end, phase difference between collector/drain and
and short-circuited or tuned at the other end. emitter/source is exploited.
paramagnet A paramagnetic substance (see PARA-
MAGNETISM). Compare DIAMAGNET.
+ 12 V
paramagnetic Possessing PARAMAGNETISM.
Compare DIAMAGNETISM.
paramagnetism The state of having a magnetic
permeability slightly greater than 1. Compare
DIAMAGNETISM.
parameter 1. An operating value, constant, or co-
efficient that can be either a dependent or an in-
dependent variable (e.g., a transistor-electrode Out X
current or voltage). 2. The ratio of one coefficient
to another, where both are either fixed or variable
(e.g., transconductance of a vacuum tube).
parameter word In a computer memory, a place In
having a capacity of a word (bit group) in which is
stored a parameter for a program.
parametric amplifier A radio-frequency power
amplifier based on the action of a voltage-variable
capacitor in a tuned circuit.
parametric amplifier diode See VARACTOR.
parametric converter A frequency converter in
which a parametric device, such as a varactor, is
used to change a signal of one frequency to a sig-
Out Y
nal of another frequency. Also see PARAMETRIC
DOWN-CONVERTER and PARAMETRIC UP-
CONVERTER.
parametric diode A variable-capacitance diode
(see VOLTAGE-VARIABLE CAPACITOR, 1).
parametric down-converter A parametric con-
verter in which the output signal is of a lower paraphase inverter
frequency than the input signal. Compare
PARAMETRIC UP-CONVERTER.
parametric equalizer A set of audio filters similar parasitic See PARASITIC OSCILLATION.
to a GRAPHIC EQUALIZER, except that the cen- parasitic antenna See PARASITIC ARRAY, PARA-
ter frequencies are adjustable, rather than fixed. SITIC ELEMENT.
The center frequencies are selected by the opera- parasitic array Any of several types of directional
tor; then the attenuation level (in decibels) is set antenna employing parasitic elements, some-
for each frequency. It is used in audio recording times in combination with phasing, to obtain di-
studios. rectivity and gain. Common examples include the
parametric modulation Modulation in which ei- Yagi and quad. Arrays with numerous parasitic
ther the inductance or capacitance of a tank cir- elements (usually directors) can produce up-
cuit or coupling device is varied at the wards of 15 dBd forward gain. When several
modulation frequency. high-gain arrays are phased, the realizable
parametric oscillator An oscillator that generates gain becomes greater still. Two-element, three-
visible light energy by means of a parametric am- element, and four-element arrays are common
plifier and a tunable cavity. below 30 MHz. At very-high and ultra-high fre-
parametric up-converter A parametric converter quencies, especially above 100 MHz, bays of an-
in which the output signal is of a higher fre- tennas of this type are used in satellite
quency than the input signal. Compare PARA- communications and radio astronomy. See PAR-
METRIC DOWN-CONVERTER. ASITIC ELEMENT, QUAD ANTENNA, YAGI AN-
parametron See PHASE-LOCKED OSCILLATOR. TENNA.
paramistor A device consisting of several digital parasitic capacitance Stray capacitance. It can be
circuit elements that use parametric oscillators. internal or external to a circuit and can introduce
paramp Abbreviation of PARAMETRIC AMPLIFIER. undesirable coupling or bypassing.
516 parasitic choke • pass amplifier


parasitic choke A small radio-frequency choke parity check A check of the integrity of data being
coil (with or without a shunting resistor) that transferred by adding the bits in, for example, a
suppresses or eliminates parasitic oscillation in a word, and then determining the parity bit needed
power amplifier. and comparing that with the transmitted parity
parasitic director In a multielement directional bit.
antenna, a parasitic element acting as a director; parity error An error disclosed by a parity check.
usually, it is a few percent shorter than the driven parity tree A digital device used to check parity.
element. parsec Abbreviation, pc. The distance at which the
parasitic element An electrical conductor that mean radius of the earth™s orbit around the sun
comprises an important part of an antenna sys- subtends an angle of 1 second of arc; 1 pc =
3.0857 — 1013 kilometers or 3.2616 light years.
tem, but that is not directly connected to the feed
line. Such elements are used for the purpose of part See CIRCUIT COMPONENT, 1.
obtaining directivity and power gain. They oper- part failure The usually destructive breakdown of
ate via electromagnetic coupling to the driven el- a circuit component.
ement(s). The principle of operation was first partial One of the frequencies in a complex musi-
discovered by the Japanese engineers Yagi and cal tone. It might be a harmonic of the funda-
Uda, who observed that antenna elements paral- mental frequency, although this is not always the
lel to a driven element but not connected to any- case.




Y
thing, at a specific distance from the driven partial carry The temporary storage of some or all
element, and having a certain length, cause the of the carry information in a digital calculation.




FL
radiation pattern to show gain in one direction particle 1. A tiny, discrete bit of matter. 2. A unit
and loss in the opposite direction. See DRIVEN of matter smaller and lighter than an atom. See,
ELEMENT, PARASITIC ARRAY, PARASITIC DI- for example, ANTIPARTICLE, ELECTRON, ME-
RECTOR, PARASITIC REFLECTOR. SON, NEUTRETTO, NEUTRINO, NEUTRON, NU-
AM
parasitic-element directive antenna See PARA- CLEON, POSITRON, and PROTON.
SITIC ARRAY. particle accelerator See ACCELERATOR, 1.
parasitic eliminator See PARASITIC SUPPRES- particle theory of radiation In physics, a model
SOR. that explains the nature of electromagnetic radia-
parasitic excitation Excitation of a beam-antenna tion (radio waves, infrared, visible light, ultravio-
TE

element without a direct connection to the trans- let, X rays, and gamma rays) in terms of discrete
mitter. Thus, a director or reflector element can particles. Each particle, called a PHOTON, carries
be excited by the field of the radiator element. a certain amount of energy that depends on the
parasitic inductance Stray inductance (e.g., the wavelength of the radiation.
internal inductance of a wirewound resistor). particle velocity 1. The speed and direction of
parasitic oscillation Extraneous, useless oscilla- the particles from a source of atomic radiation.
tion present as a fault in an electronic circuit, 2. The speed and direction of the molecules in the
particularly a radio-frequency power amplifier. medium of an acoustic disturbance.
parasitic reflector In a multielement beam an- partitioning In computer operations, breaking
tenna, a parasitic element acting as a reflector; down a large block of data into smaller blocks
usually, it is a few percent longer than the driven that can be better handled by the machine.
element. parton model A model for atomic nuclei, in which
parasitic resistance Stray resistance (e.g., the in- protons and neutrons are made up of smaller
herent, internal resistance of a multilayer coil). particles called partons. Subparticles have been
parasitic suppressor A small resistor, coil, or par- found, commonly called quarks.
allel combination of the two, connected in series Pascal A high-level computer programming lan-
with the plate or collector of a vacuum tube or guage, similar to BASIC or FORTRAN in struc-
transistor to eliminate parasitic oscillations in a ture. It is used in some schools to teach computer
radio-frequency power amplifier. programming.
PARD Abbreviation of PERIODIC AND RANDOM pascal Symbol, Pa. The SI (derived) unit of pres-
sure; 1 Pa = 1 N/m2 = 1.4503 — 10“4 lb/in2.
DEVIATION.
parity 1. At par (with respect to the even-or-odd Paschen-Back effect See ZEEMAN EFFECT.
state of the characters in a group). 2. Having the Paschen™s law For a two-element, parallel-plate,
quality that the number of bits (or the number of gas-discharge tube, the plate-to-plate sparking
similar bits) are even or odd, as intended. potential is proportional to Pd, where P is the gas
parity bit 1. In computer operations, a logic 1 pressure, and d is the distance between plates.
added to a group of bits so that the number of 1s pass amplifier A tuned amplifier having the re-
in the group is, according to specification, even or sponse of a bandpass filter. Like the filter, the
odd. 2. In computer operations, a check bit that amplifier passes one frequency (or a narrow
can be a logic 1 or 0, depending on the parity (see band of frequencies) readily while rejecting or
PARITY, 1) of the total of 1s in the bit group being attenuating others. Compare REJECT AMPLI-
checked. FIER.




Team-Fly®
517
passband • passive reflector


passband The continuous spectrum of frequencies requires no power for its characteristic opera-
transmitted by a filter, amplifier, or similar de- tion). Examples: conventional resistor, capacitor,
vice. Compare STOPBAND. inductor, diode, rectifier, and fuse. Compare AC-
passband ripple Multiple low-amplitude attenua- TIVE COMPONENT, 1.
tion variations within the passband of a filter or passive comsat See PASSIVE COMMUNICATIONS
tuner, resulting in a ripple pattern on the nose of SATELLITE.
the response curve. passive decoder A decoder that responds to only
one signal code, rejecting all others.
passive detection In reconnaissance, detecting a
Passband target without betraying the location of the detec-
at 3 dB down tor.
passive electric network See PASSIVE NET-
WORK.
passive frequency multiplier A frequency multi-

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