<<

. 32
( 42)



>>

ging, and compiling programs. quinary code See BIQUINARY CODE.
quiescent carrier operation A modulation system quinary counter A decade counter consisting of a
in which the carrier is present only during modu- five-stage ring.
lation (i.e., it is suppressed at all other times). quinhydrone electrode A pH meter electrode con-
Also called controlled-carrier transmission. sisting of a platinum wire in a solution of quinhy-
quiescent-carrier telephony A carrier-current drone (C12H10O4). Also see PH METER.
(wired-wireless) telephone system in which the quintillion The number 1,000,000,000,000,
000,000 (1018).
carrier is suppressed when there is no voice or
alerting signal. quintupler 1. A rectifier circuit that delivers a di-
quiescent component In an electronic device, a rect-current output voltage equal to about five
component that is momentarily nonfunctional. times the peak value of the alternating-current
quiescent current Operating current (usually a di- input voltage. 2. A circuit that delivers an out-
rect current) flowing in a circuit or component put signal at the fifth harmonic of the input sig-
during zero-signal or no-drain intervals. Also nal.
called IDLING CURRENT. QWERTY The standard typewriter and computer
quiescent operation Zero-signal operation of a de- keyboard layout. The name is derived from the
vice, such as a transistor, diode, magnetic ampli- first several letters in the top letter row: Q, W, E,
fier, or similar component. R, T, and Y.
R 1. Symbol for RESISTANCE. (Also, r.) 2. Ra- Scale
diotelegraph abbreviation for ROGER. 3. Symbol
for RELUCTANCE. 4. Abbreviation of RADIUS.
r 1. Symbol for ROENTGEN. 2. Symbol for correla- Pointer
tion coefficient. 3. Abbreviation of RADIUS. (Also,
abbreviated R.)
re Symbol for CLASSICAL ELECTRON RADIUS.
RA 1. Abbreviation of right ascension. 2. Abbrevia-
Straight,
tion of RANDOM ACCESS.
toothed rod Shaft
rabbit ears An indoor antenna, sometimes used
with a television receiver, consisting of two verti-
cal whips (usually telescoping), the angle between
which is adjustable.
Round,
RAC Abbreviation of RECTIFIED ALTERNATING toothed gear
CURRENT.
Rac Symbol for AC RESISTANCE. (Also, rac.)
race Incorrect interpretation of the clock pulses by
a digital circuit. Also called racing. The circuit im- rack and pinion
properly attempts to do many operations during
one clock pulse, rather than a single operation. rack up In computer operations, a way of display-
RACES Abbreviation of Radio Amateur Civil Emer- ing data, in which a new line added to the already
gency System. completely occupied screen bumps up what has
raceway See WIRE DUCT and WIREWAYS. forgone, thus eliminating the top line.
rack An upright frame for holding equipment of racon Acronym for radar beacon.
RACK-AND-PANEL CONSTRUCTION. rad 1. A unit of ionizing radiation received by a
rack-and-panel construction A method of build- body (dose) equal to 0.001 J/kg. 2. Abbreviation
ing electronic equipment on a chassis attached of RADIAC. 3. Abbreviation of RADIAN. 4. Abbre-
horizontally or vertically to a vertical panel. After viation of RADIO. 5. Abbreviation of RADIX.
completion of a unit, the panel is fastened in radar 1. A microwave system for detecting objects
place on a RACK. Several such panels fill the and determining their distance, direction, head-
rack. ing, speed, and other characteristics. Signals
rack and pinion A device used for mechanical ad- from the transmitter are reflected back to the
justment of a control, such as the tuning control transmitter site by the object, and the reflection
in a radio receiver. A gear engages a serrated rod. (sometimes along with the transmission) is dis-
As the gear is turned, the rod moves lengthwise. played on a cathode-ray screen. The name is an


Copyright © 2001 by The McGraw-Hill Companies, Inc.
Click here for Terms of Use.
575
radar • radial


acronym for radio detection and ranging. 2. The (usually in degrees clockwise from geographic
theory and application of radio detection and north) and radius from the transmitter (usually
ranging systems as defined in 1. in miles or kilometers). Altitude above mean sea
radar altitude The distance of an aircraft above level can be displayed for individual echoes.
the surface of the earth, as determined by radar. radar homing A method of missile homing in
This value varies with the terrain over which the which radar is used to track a target.
aircraft passes. radar speed trap A radar system used by traffic
radar antenna Any antenna used for transmitting police to spot speeding vehicles.
and/or receiving radar signals. radar telescope The transmission and reception
radar astronomy The use of radar equipment to unit used in radar astronomy. Compare RADIO
observe and map planets, moons, and asteroids, TELESCOPE.
and to measure their distance from the earth or RadCM Abbreviation of RADAR COUNTERMEA-
from a spacecraft. SURES. (Also, RCM.)
radar beacon A radar transceiver that, on receipt radial 1. One of several conductors used to enhance
of radar signals, transmits encoded signals from the performance of an unbalanced, vertical an-
which the operator can take a bearing. tenna. These can be constructed from wire or
radar beam The cone-shaped main lobe of energy metal tubing, and generally measure one-quarter
emitted by a radar antenna. The narrower the wavelength or more. When a vertical antenna is
beam, the greater the resolution of the radar sys- mounted at the earth™s surface, the ground con-
tem. ductivity is improved by these conductors, which
radar clutter Visual interference on a radar screen run outward from the base of the radiator, and are
caused by reflections from ground or sea. connected to the shield of a coaxial feed line. The
radar countermeasures Abbreviations, RCM and greater the number of radials of a given length, the
rad CM. In wartime, any method of interfering more the ground loss is reduced. Also, the longer
with enemy radar, such as jamming or use of de- the radials for a given number, the better. If a ver-
coys. tical radiator is mounted with its base more than
radar detector 1. A device used in automobiles one-quarter wavelength above the earth™s sur-
and trucks to detect the proximity of police or face, there need only be three or four conductors
highway-patrol radar. 2. A device used in military measuring exactly one-quarter wavelength.
applications, especially aviation, to indicate the See GROUND-MOUNTED VERTICAL ANTENNA,
presence of radar. GROUND-PLANE ANTENNA. 2. Pertaining to the
radar display The scheme via which a radar set distance from the center of a circle to its periphery.
portrays the relative positions of the objects that 3. Pertaining to the distance from the center of a
produce echoes. The most common is the az- sphere to its surface. 4. Extending or emanating
imuth/range display, showing compass bearings outward in a straight line from a defined point.



Vertical
radiating
element




Radial Radial


Coaxial
feed line


radials
576 radial ground • radioactive


radial ground An earth connection composed of Maximum
radials buried in the ground. radiation
radial lead A lead (pigtail) attached perpendicular
to the axis of a component, such as a resistor or
capacitor.
radian Abbreviation, rad. The angle at the center of Antenna
a circle subtended by an arc whose length is
equal to the radius. Equal to approximately Angle
57.2958 degrees.
radiance The radiant flux emitted by an object. Ra-
diance is measured in terms of the amount of en-
ergy contained in a unit solid angle (steradian)
with the source at the apex.
Average terrain
radians-to-degrees conversion The conversion of
(horizontal)
radian angular measure into degrees. To change
radians to degrees, multiply the number of de-
grees by 57.2958. Thus, 0.7854 radian = 45 de-
grees. Compare DEGREES-TO-RADIANS CON-




Y
radiation angle
VERSION.
radiant efficiency The ratio of the radiant energy




FL
emitted by a source to the energy consumed by radiation loss Loss of energy through radiation
the source. The radiant energy is generally speci- from a conductor. Also see LOSS.
fied within a certain range of wavelengths. An ex- radiation pattern A graphical representation of
ample is the incandescent light bulb, which has the intensity of the electromagnetic field in vari-
AM
relatively low radiant efficiency in the visible ous directions from a radiator, such as a trans-
spectrum between about 750 and 390 nanome- mitting antenna. It is usually shown in either the
ters. horizontal plane or a specific vertical plane con-
radiant energy 1. Any form of energy emitted by a taining the antenna. Also see LOBE.
source and propagated through space as an elec- radiation physics The study of radiation and its
TE

tromagnetic disturbance. Included are radio effects on matter. Radiation physics is especially
waves, infrared, visible light, ultraviolet, X rays, concerned with ionizing radiation, but it can in-
and gamma rays. 2. Electromagnetic distur- volve any kind of particle or electromagnetic en-
bances at infrared and shorter wavelengths. ergy.
radiant flux The rate at which radiant energy is radiation pressure Pressure exerted on a surface
emitted. by impinging electromagnetic radiation.
radiation 1. The emission of energy or particles radiation resistance The inherent resistance at
(e.g., waves from an antenna, X rays from an X- the feed point of a resonant radio antenna.
ray tube, energy from a radioactive material, heat radiation sickness General physiological symp-
from a body, etc.). 2. Radio waves, infrared, visi- toms resulting from a short-term overdose of
ble light, ultraviolet, X rays, or gamma rays. X rays, gamma rays, or atomic-particle radia-
3. Ionizing emissions from radioactive substances tion.
(e.g., alpha particles, beta particles, neutrons, radiator 1. The element of an antenna from which
gamma rays, etc.). radio energy is directly radiated, as opposed to
radiation angle The horizontal or vertical angle at the transmission line, lead-in, reflector, or direc-
which electromagnetic waves are radiated from tor. 2. See LOUDSPEAKER.
an antenna. Measured between the central axis of radio 1. Wireless electrical communication, i.e., by
the main lobe and the horizon, or between the means of electromagnetic waves. 2. See RADIO
central axis of the main lobe and geographic RECEIVER. 3. See RADIO TRANSCEIVER. 4. See
north. RADIO TRANSMITTER. 5. To communicate by ra-
radiation belts See VAN ALLEN RADIATION dio.
BELTS. radio- 1. A prefix meaning “pertaining to wireless
radiation counter An instrument used for deter- electrical communication.” Examples: radiotele-
mining the intensity of atomic-particle radiation, phone and radiotelegraph. 2. A prefix meaning
X rays, or gamma rays. It operates by means of “using radio waves.” Examples: radiosonde, ra-
ionization of a gas in a sealed tube. diolocator, and radiothermics. 3. A prefix meaning
radiation field The portion of the electromagnetic “pertaining to using or possessing radioactivity,”
field that is propagated by a radiator, as opposed or “pertaining to X rays.” Examples: radiograph,
to the induction field. radioisotope, and radiologist.
radiation intensity For a directional radio trans- radioactive Having the property of emitting alpha,
mitting antenna, the radiated power per stera- beta, and (sometimes) gamma rays as the result
dian in a given direction. of nuclear disintegration. Also see HALF-LIFE.




Team-Fly®
577
radioactive element • radio-frequency choke


radioactive element A chemical element that is radio control See REMOTE CONTROL.
RADIOACTIVE (e.g., uranium). Also called ra- radio direction finder See DIRECTION FINDER.
dioelement. radio Doppler 1. A change in the frequency of a ra-
radioactive isotope See RADIOISOTOPE. dio signal emitted by a source having radial mo-
radioactive tracer A quantity of radioactive mate- tion, with respect to the receiver. 2. An electronic
rial put into a system so that its path can be mon- device used to measure radial speed by means of
itored by means of a radiation detector. An the Doppler effect at radio frequencies.
example is the introduction of radioactive barium radio-electronics The branch of electronics specif-
into the large intestine. The flow and concentra- ically involved with wireless communications.
tion of the barium gives an indication of the func- radioelement See RADIOACTIVE ELEMENT.
tioning of the lower intestine. radio engineer A trained professional skilled in the
radioactive transducer A pickup device for detect- physics and mathematics of radio communica-
ing and measuring radioactivity (e.g., Geiger- tions, and in the theory and application of basic
Mueller tube). electronics engineering and related subjects. Also
radioactivity counter See GEIGER COUNTER see RADIO ENGINEERING.
and SCINTILLATION COUNTER. radio engineering The branch of electronics engi-
radio altitude See RADAR ALTITUDE. neering devoted to the theory and operations of
radio amateur An electronics hobbyist licensed to radio communication.
operate two-way wireless communications sta- radio field strength The intensity of radio waves
tions in various assigned frequency bands, with- at a given point. Also see FIELD INTENSITY, 2
out receiving payment for services rendered. and RADIO MAP.
Radio Amateur Civil Emergency System Abbre- radio frequency Abbreviation, RF. 1. Consisting
viation, RACES. A civil-defense organization of li- of, or pertaining to, alternating currents at fre-
censed amateur radio stations. Also see RADIO quencies above about 9 kHz (the lowest allocated
AMATEUR. radio communications frequency). 2. Consisting
radio astronomy The observation, study, and of, or pertaining to, electromagnetic fields whose
analysis of radio-frequency electromagnetic emis- wavelengths are longer than those of infrared,
sions from bodies or points in space, and the but shorter than about 33 kilometers (corre-
study of these bodies through their radiations. sponding to a frequency of 9 kHz). Also see RA-
radioautograph See AUTORADIOGRAPH. DIO SPECTRUM.
radio beacon 1. A radio transmitter of direction- radio-frequency amplifier 1. In a superhetero-
finding or guidance signals. 2. Also called radio dyne circuit, the channel in which the incoming
beam. The signals transmitted by a radio beacon, signal is amplified. Compare INTERMEDIATE-
as defined in 1. FREQUENCY AMPLIFIER. 2. Broadly, an ampli-
radio beam 1. Antenna radiation focused in one fier of radio-frequency signals.
direction. 2. See RADIO BEACON, 2. radio-frequency choke Abbreviation, RFC. A low-
radiobiology A field of biology concerned with the inductance coil used to block radio-frequency
influence of radiant energy or radioactivity on liv- (RF) alternating currents. Many RF chokes have
ing organisms. air cores; some have cores of ferrite or powdered
radio broadcast A radio transmission directed to iron.
numerous, nonspecific receivers”especially by a
station in the broadcast service. Also called RA-
DIOCAST. Also see BROADCAST SERVICE, 1, 2.
radio car An automobile equipped with a two-way
radio.
radio carbon Radioactive carbon (i.e., carbon 14).
radiocast See RADIO BROADCAST.
radio channel A single, usually narrow radio- Out
frequency band within a larger band, in which
In
stations are authorized to transmit signals of a
specified type. Also see CHANNEL, 1; CHANNEL
SEPARATION; and CHANNEL WIDTH.
radiochemistry The chemistry of radioactive sub-
stances.
radio communication Wireless communication
carried on by means of radio-frequency electro- +12 V
magnetic waves.
radio compass See DIRECTION FINDER.
(General bipolar circuit)
radioconductor A substance or body whose elec-
trical conductivity is affected by radio waves, and
that can be used as a sensor of such waves. radio-frequency amplifier, 2
578 radio-frequency current • radiolocation


radio-frequency current Symbol, IRF. 2. The in- radiogram A (usually printed out) message trans-
tensity of a generated radio-frequency (RF) signal, mitted and received via radiotelegraphy or ra-
usually expressed in microamperes. 2. Loosely, dioteletype. The term is an acronym for radio
any measurable RF signal. telegram.
radio-frequency heating The generation of heat in radiograph 1. To contact by sending a RADIO-
an object by an intense radio-frequency electro- GRAM. 2. An X-ray photograph.
magnetic field. See, for example, DIATHERMY, 1; radio homing 1. A method of homing that uses the
DIELECTRIC HEATING; and INDUCTION HEAT- tracking of a target on the basis of a radio signal
ING. emitted by that target. 2. A method of keeping a
radio-frequency interference Abbreviation, RFI. missile on track via radio remote control.
1. Annoying electrical noise in radio-frequency radio interference 1. Interference to radio com-
(RF) amplifiers, detectors, and instruments. munication, from whatever cause. 2. See RADIO-
2. Undesired RF signals that compete with desired FREQUENCY INTERFERENCE.
ones in amplifiers, receivers, and instruments. radioisotope A radioactive isotope (natural or artifi-
3. The unwanted interception and demodulation cial) of a normally nonradioactive chemical element
of a strong RF signal by an audio-frequency (AF) (e.g., radioactive carbon). Also see ISOTOPE.
device, such as a telephone set or high-fidelity radio jamming See JAMMING.
stereo amplifier. radio knife A surgical instrument consisting essen-
radio-frequency meter An instrument for mea- tially of a needle that forms a high-frequency arc.
suring signals of RADIO FREQUENCY (9 kHz and The arc simultaneously cuts and cauterizes tissue.
above). radiolocation A process whereby the position of a
radio-frequency oscillator Abbreviation, RFO. An vehicle, aircraft, or ocean-going vessel is deter-
oscillator (self-excited or crystal-controlled) for mined. The simplest method is the directional
operation at radio frequencies. In such an oscilla- method. Two or three fixed receiving stations are
tor, stray components, efficiency, and general used. Radio direction-finding (RDF) equipment is
losses are of primary concern. Also see RADIO employed at each station, in conjunction with a
FREQUENCY. transmitter aboard the vessel, to establish the
radio-frequency power Symbol, PRF. Alternating- bearings of the vessel with respect to each sta-
current power at radio frequencies. tion. Radar can also be used to locate vessels. In
radio-frequency resistance The total in-phase re- wartime, enemy craft can sometimes be located
sistance exhibited by a conductor at radio fre- by visual or infrared apparatus. Satellites can lo-
quencies. This opposition to current includes cate enemy ships and missiles, in some cases
direct-current resistance and the in-phase com- with an error smaller than the length of the ves-
ponents caused by skin effect, shielding, and the sel itself. Compare RADIONAVIGATION.
presence of dielectrics.
radio-frequency selectivity The selectivity of a ra-
dio-frequency (RF) channel, such as the RF am-
plifier and first detector of a superheterodyne
circuit. Receiver
radio-frequency transformer Abbreviation, RF X
transformer. A device used for the purpose of
impedance matching, antenna tuning, or inter-
stage coupling at frequencies above the range of
human hearing (approximately 20 kHz and up). Receiver
Vessel
The device might consist of solenoidal windings Y
with an air core, solenoidal windings with a
powdered-iron or ferrite core, or toroidal wind-
ings with a powdered-iron or ferrite core. The
windings are designed to minimize distributed
capacitance and direct-current resistance.
When no reactance is present, the impedance-
transfer ratio is equal to the square of the turns
ratio. Compare AUDIO-FREQUENCY TRANS-
FORMER.
radio-frequency transistor 1. A transistor capa-
ble of providing significant amplification at radio
frequencies. 2. A transistor operable at frequen-
Receiver Z
cies above 100 kHz.
radiogenic Produced by radioactivity.
radiogoniometer A radio compass (see DIREC-
radiolocation
TION FINDER and GONIOMETER, 1).
579
radiolocator • radio spectroscope


radiolocator See RADAR. radio micrometer See MICRORADIOMETER.
radiological system See X-RAY THERAPY SYS- radionavigation The use of radio apparatus, usu-
TEM. ally in conjunction with computers, by personnel
radiologist A specialist skilled in RADIOLOGY. aboard moving vessels, for the purpose of plotting,
radiology The science embracing the theory and correcting, and maintaining a course. The inter-
use of X rays and radioactive substances in the secting-line method is simplest. Two or three
diagnosis and treatment of diseases and ail- land-based transmitters are needed. Their loca-
ments. tions must be accurately known. A direction-
radiolucency 1. The property of a material that al- finding device on the vessel is used to determine
lows ionizing radiation to pass through it with lit- the bearings of each of the transmitters. Aircraft
tle or no absorption. 2. The extent to which a radionavigation can be performed with the aid of
material transmits ionizing radiation. radar. The most sophisticated radionavigation
radioluminescence Visible light emitted from a ra- techniques employ the Global Positioning System
dioactive material. A good example is radium; it (GPS). Computers are used to project the course
was once used on wristwatch dials so that they of a craft based on its current position, its speed,
could be seen in the dark. and the direction of its movement. Course correc-
radiolysis Chemical decomposition brought about tions are made by choosing the desired course
by radiation. and having the computer calculate speed and/or
radioman A radio technician or operator. direction changes. Compare RADIOLOCATION.
radio map A map of a geographic area, on which radio net A group of radio stations operating to-
lines are drawn connecting measured points of gether in an organization, often on or near the
equal field strength for signals from a radio sta- same frequency.
tion at the approximate center of the area. radio network See RADIO NET.
radiometeorograph See RADIOSONDE. radio operator A technician licensed to operate a
radiometer A device for detecting and measuring transmitter in the radio, television, or radar ser-
the strength of radiant energy. One form consists vices.
of a set of vanes blackened on one side and radiopaque Opaque to X rays or other ionizing ra-
mounted on pivots in a partially evacuated glass diation. Compare RADIOPARENT.
bulb. Visible light or infrared causes the vane as- radioparent Transparent to X rays or other ioniz-
sembly to rotate, the speed being proportional to ing radiation. Compare RADIOPAQUE.
the intensity of the light. radiophone See RADIOTELEPHONE.
radiophoto A photograph transmitted and re-
ceived by radio. Also see FACSIMILE.
Glass
radio pill See ENDORADIOSONDE.
envelope
radio prospecting The use of radio-frequency de-
vices to locate underground or underwater metals
and mineral deposits. Also see METAL LOCATOR.
radio range A radio station providing navigational
Light
aid to airplanes.
radio receiver The complete apparatus that se-
lects, amplifies, demodulates, and reproduces a
radio signal for purposes of communication, as
distinct from facsimile receiver, remote-control re-
ceiver, telemetry receiver, television receiver, etc.
radiosensitivity 1. The property of being sensitive
to ionizing radiation. Most photographic films
have this property. 2. The extent to which a sub-
stance or device is sensitive to ionizing radiation.
radio service technician An electronics techni-
cian skilled in the repair and maintenance of ra-
dio equipment”especially receivers.
radiosonde A balloon-carried combination of radio
transmitter and transducers, for sending to a
ground monitoring station signals revealing such
atmospheric conditions as temperature, humid-
radiometer ity, and pressure. It is used mainly for gathering
meteorological data at high altitudes.
radiometry The science and art of measuring radi- radiosonobuoy See SONOBUOY.
ation in the infrared, visible, and ultraviolet re- radio spectroscope A device used by radio as-
gions of the electromagnetic frequency spectrum. tronomers to obtain the radio-frequency profile of
Compare PHOTOMETRY. a distant star or galaxy. It generally consists of a
580 radio spectroscope • radiothermics


graph, obtained by scanning the radio spectrum frequency (UHF), 300 to 3000 MHz; super high fre-
and plotting signal intensity as a function of fre- quency (SHF), 3 to 30 GHz; extremely high fre-
quency or wavelength. quency (EHF), 30 to 300 GHz.
radio spectrum The continuum of frequencies radiostat See CRYSTAL FILTER.
useful for radio communication and control. radio station 1. The location at which a radio
Classified in the following manner: Very low fre- transmitter and/or receiver is/are installed.
quency (VLF), 9 to 30 kHz; low frequency (LF), 30 2. The complete set of equipment for a radio receiv-
to 300 kHz; medium frequency (MF), 300 to 3000 ing and/or transmitting installation, including
kHz; high frequency (HF), 3 to 30 MHz; very high the studio, linking apparatus, and antennas. 3. A
frequency (VHF), 30 to 300 MHz; ultrahigh standard broadcast station.
radio technician A professional skilled in the con-
struction, testing, repair, and maintenance of radio
To
equipment, and sometimes in its design, and who
infrared,
usually works under the supervision of a radio en-
visible light,
ultraviolet, X rays, gineer. Also see RADIO SERVICE TECHNICIAN.
gamma rays radiotelegram See RADIOGRAM.
radiotelegraph 1. Pertaining to the theory and ap-
plication of, and the equipment for, Morse code
transmission and/or reception via radio. 2. An
0.1 mm 3 THz installation for Morse code transmission and/or
Decimillimetric reception via radio. 3. The transmission and/or
reception of Morse code signals via radio.
radiotelegraph code See CONTINENTAL CODE.
1 mm 300 GHz
radiotelegraph distress signal See SOS.
Millimetric EHF
radiotelegraph monitor See KEYING MONITOR.
Microwaves radiotelegraphy The transmission and/or recep-
tion of telegraphic communications, usually
1 cm 30 GHz Morse code, by means of radio.
Centimetric SHF radiotelephone 1. Pertaining to the theory and ap-
plication of, and the equipment for, voice trans-
mission and/or reception via radio. 2. An
10 cm 3 GHz installation for voice transmission and/or recep-
Decimetric UHF
tion via radio. 3. The transmission and/or recep-
tion of voice signals via radio.
radiotelephone distress signal See MAYDAY.
1m 300 MHz radio/telephone patch See PHONE PATCH.
VHF radiotelephony The transmission and/or recep-
tion of audio signals, usually human voices, by
Metric
means of radio.
10 m 30 MHz radio telescope A directional antenna and associ-
HF ated equipment for receiving and evaluating the
radio-frequency electromagnetic radiation from
Decametric
space”especially from celestial objects (such as
100 m 3 MHz the sun, planets, stars, nebulae, galaxies,
MF quasars, etc.). See RADIO ASTRONOMY.
radioteletype 1. Pertaining to the theory and ap-
Hectometric
plication of, and the equipment for, text data
1 km 300 kHz transmission and/or reception via radio. 2. An
LF installation for text data transmission and/or re-
ception via radio. 3. The transmission and/or re-
Kilometric
10 km 30 kHz ception of text data signals via radio.
VLF radioteletypewriter A teletypewriter adapted to
Myriametric radio, rather than wire service; it is used in some
30 km 10 kHz
RADIOTELETYPE installations. In recent years,
100 km 3 kHz personal computers and terminals have largely
replaced adapted teletypewriters for this purpose.
radiotherapy The use of X rays and/or radioactive
To lower audio substances in the treatment of disease and disor-
and subaudio ders.
radiothermics The science of the generation of
radio spectrum heat by means of radio-frequency current.
581
radiothermy • random feed


radiothermy See DIATHERMY. rad/s Abbreviation of radians per second, the SI
radio thorium Radioactive THORIUM. unit of angular velocity.
rad/s2 Abbreviation of radians per second squared,
radiotracer See TRACER.
radio transceiver A RADIO RECEIVER and RADIO the SI unit of angular acceleration.
TRANSMITTER built into a single unit, and gener- radux A continuous-wave, low-frequency radion-
ally intended for use in two-way communication. avigation system. Position is determined by com-
radio transmitter The complete apparatus that paring the phase of two signals sent from
generates radio-frequency power, modifies it with different locations.
the data needed for communication, and delivers RAID Acronym for REDUNDANT ARRAY OF INDE-
the product to an antenna for radiation into PENDENT DISKS.
space. Here, the radio transmitter is distin- rainbow generator A test-signal generator that
guished from similar equipment: facsimile trans- produces a full color spectrum, a pattern resem-
mitter, remote-control transmitter, telemetry bling the successive coloration of a rainbow, on
transmitter, television transmitter, etc. the screen of a color-television receiver. Also see
radio-transparent material 1. A substance RAINBOW PATTERN.
through which radio waves pass with little or no rainbow pattern A test pattern for servicing a
attenuation. 2. A substance through which color-television receiver. It consists of a full color
X rays, gamma rays, or high-speed subatomic spectrum, thus taking its name from its resem-
particles can pass with little or no attenuation. blance to a rainbow. Also see RAINBOW GENER-
radiotrician Acronym for radio electrician. See RA- ATOR.
DIO SERVICE TECHNICIAN. RAM Abbreviation of RANDOM-ACCESS MEM-
radio tube 1. A VACUUM TUBE used at radio fre- ORY.
quencies. 2. A vacuum tube used as an amplifier, ramp A sawtooth wave with a linear rise and a
local oscillator, detector, or mixer in an early ra- practically instantaneous decay; its name was
dio receiver. derived from its resemblance to an incline.
radiovision See TELEVISION.
radio watch See WATCH.
radio waves Electromagnetic waves in the RADIO
SPECTRUM.
radio window That portion of the radio-frequency
Amplitude




electromagnetic spectrum that passes through
the atmosphere, rather than being refracted or
absorbed. The wavelength range is about 20 me-
ters to 5 millimeters, or 15 MHz to 60 GHz. The
lower limit of this range is affected by ionospheric
conditions. The upper frequency limit depends on
various factors, including relative humidity and Time
dust content of the air.
radium Symbol, Ra. A rare radioactive metallic ramp
element. Atomic number, 88. Atomic weight,
226.025.
radius The straight-line distance from the center of ramp generator A test-signal generator that pro-
a circle or sphere to its periphery. duces sawtooth-wave signals. Also see RAMP.
radius vector In spherical or polar coordinates, a R and D Abbreviation of research and development
line segment drawn from the pole, or origin, and or research and design. (Also, R&D.)
representing the vector magnitude. random access Abbreviation, RA. In computer and
radix The number indicating the number of sym- data-processing operations, pertaining to storage
bols in a system of numerical notation, and the or memory in which data can be recovered in any
powers of which give the place values of the sys- order.
tem. Thus, 10 is the radix of the decimal system, random-access memory In computer and data-
and 2 is the radix of the binary system. Also processing systems, a memory providing access
called BASE. time that is independent of the address.
radix point In a number, the point (dot or period) random deviation Irregular RIPPLE.
separating the integral and fractional digits. Its random-fed antenna An antenna that uses RAN-
specific name depends on the system of notation DOM FEED.
involved: binary point, decimal point, etc. random feed A method of connecting a transmis-
radome A plastic shell housing a radar antenna” sion line to an antenna, wherein the feed point is
especially aboard an aircraft. not necessarily at the center and not necessarily
radon Symbol Rn. A gaseous radioactive element at a current loop or voltage loop. This technique
that results from the disintegration of radium. is rarely used; it generally results in some radia-
Atomic number, 86. Atomic weight, 222. tion from the feed line.
582 random noise • ratio detector


random noise Electrical noise in which the pulses raser A device that produces coherent electromag-
or fluctuations have no discernible pattern of oc- netic waves at radio frequencies; the radio-
currence (i.e., they are haphazard in frequency frequency equivalent of a LASER.
and amplitude). raster The rectangle of light (composed of unmod-
random number A number derived by chance. It is ulated lines) seen on the screen of a television
used in statistical analysis for various purposes. picture tube when no signal is present.
random number generator Hardware or software ratchet circuit See COMMUTATOR, 2 and ELEC-
that provides a sequence of numbers or digits TRONIC RATCHET.
that are random for the purpose of a given statis- rate action See DERIVATIVE ACTION.
tical application. rate effect In a four-layer semiconductor device,
random occurrence See CHANCE OCCURRENCE. the tendency for the switch to conduct undesir-
random variable In statistics, a variable that can ably as a result of a transient spike.
have a number of values, each of the same prob- rate-grown transistor See GRADED-JUNCTION
ability. TRANSISTOR.
random winding A coil winding in which the turns rate gyro A special gyroscope for measuring angu-
are wound haphazardly to reduce distributed ca- lar rates.
pacitance. rate of change 1. The extent to which the value of
range 1. The limits within which a circuit or device a dependent variable changes in accordance with
operates (i.e., the territory defined by such lim- a specified change in an independent variable
its). Examples: current range, frequency range, (usually time). 2. A quantitative expression of the
and voltage range. 2. The difference between the speed with which a dependent variable changes,
upper and lower limits of deflection of a meter. with respect to an independent variable (usually
3. The distance over which a transmitter operates time).
reliably. 4. A clear area for testing antennas. rate signal A signal whose amplitude is propor-
5. The distance between a radar station and a tional to the derivative of a variable, with respect
target. 6. The possible values for a quantity or to time.
function that lie between given limits. rate time In automatic-control operations, the
range capacitor See TRIMMER CAPACITOR. time over which the addition of DERIVATIVE AC-
range-height indicator Abbreviation, RHI. A radar TION advances PROPORTIONAL ACTION.
display in which the horizontal axis shows dis- ratio-arm bridge A simple four-arm bridge in
tance to the target, and the vertical axis shows el- which the balancing potentiometer supplies the
evation of the target. two arms, one on each side of the slider at all
range mark See DISTANCE MARK. settings.
range plotting The creation of a graph of the dis-
tance (range) to objects, as a function of direction
Rx Rs
or orientation in two or three dimensions. Com-
monly used in robot guidance systems.
range resistor See TRIMMER RESISTOR.
range sensing The measurement of distances to
Det
objects via electronic methods such as radar, Ra
Rx = R
sonar, vision systems, etc. Commonly used in Rb s
robot guidance systems.
ranging 1. Any means of determining the distance
Ra Rb
from a station or vehicle to an object or objects.
2. Any of several methods for a vehicle, vessel,
aircraft, spacecraft, or robot to navigate in its en-
vironment by measuring, and keeping track of
changes in, the distance between itself and one or
more objects or beacons.
rank 1. To arrange in a specific sequence accord-
ratio-arm bridge
ing to significance. 2. A place in such a se-
quence.
Rankine scale A temperature scale on which the ratio arms Two impedance arms serving to estab-
freezing point of water is 491.69 degrees, and the lish the numerical ratio of a bridge circuit.
boiling point 671.69 degrees. Absolute zero is ratio control In automatic-control operations, a
represented by 0 degrees. For conversion to system in which the controlled variable is in a
kelvins, multiply degrees Rankine by 5/9. prescribed ratio to another variable.
rapid drift A fast change of a quantity or setting ratio detector A frequency-modulation (FM) sec-
(usually in one direction) with time. ond detector resembling the FOSTER-SEELEY
rapid printer See QUICK PRINTER. DISCRIMINATOR, except that one of the two
583
ratio detector • reactance


diodes is reversed and the junction point of the Rayleigh distribution A probability-density func-
load resistors is grounded. In an FM circuit using tion, used to describe the behavior of sky-wave
a ratio detector, no limiter is required. The ratio of electromagnetic signals.
the direct-current outputs is proportional to the Rayleigh™s law The hysteresis loss in a magnetic
ratio of the instantaneous signal voltages applied material varies in proportion to the cube of the
to the two diodes. magnetic induction.
ratio meter An instrument that compares two dif- Rb Symbol for RUBIDIUM.
ferent signals (and indirectly their sources) and RB Symbol for BASE RESISTANCE. (Also, rB.)
delivers a reading of their ratio. RC 1. Abbreviation of RESISTANCE-CAPACI-
rational number A number that can be expressed TANCE. 2. Abbreviation of RADIO-CON-
in the form a/b, where a and b are integers and b TROLLED. 3. Abbreviation of REMOTE CONTROL.
is not equal to zero. Rc 1. Symbol for COLLECTOR RESISTANCE. (Also,
rational operation Any of the conventional arith- rC.) 2. Symbol for COLD RESISTANCE.
metic operations: multiplication, division, addi- RCA jack See PHONO JACK.
tion, or subtraction. RCA plug See PHONO PLUG.
ratio of geometric progression In a geometric RC circuit See RESISTANCE-CAPACITANCE CIR-
progression, the ratio of one value to the next. CUIT.
ratio of similitude The ratio of the lengths of cor- RC-coupled amplifier See RESISTANCE-CAPACI-
responding sides in similar geometric figures. TANCE-COUPLED AMPLIFIER.
rat race See HYBRID RING. RC coupling See RESISTANCE-CAPACITANCE
raven red A variety of red oxide of iron, a commer- COUPLING.
cial red paint used as the magnetic coating of RC filter See RESISTANCE-CAPACITANCE FILTER.
early recording tapes. RCL 1. Abbreviation of RECALL. 2. Abbreviation of
raw ac Unrectified alternating current (ac) or volt- RESISTANCE-CAPACITANCE-INDUCTANCE.
age. RCM Abbreviation of RADAR COUNTERMEA-
raw data Data that has not been processed in any SURES. (Also, radCM.)
way. RC phase shifter See RESISTANCE-CAPACI-
rawinsonde A RADIOSONDE tracked by a radio di- TANCE PHASE SHIFTER.
rection finder to determine wind velocity. The RC time constant See RESISTANCE-CAPACI-
name is an acronym from radar wind radiosonde. TANCE TIME CONSTANT.
raw tape See BLANK TAPE. RCTL Abbreviation of RESISTOR-CAPACITOR-
ray 1. A line of radiant energy. Such a line (e.g., TRANSISTOR LOGIC.
the path of a single photon of visible light) is RC tuning See RESISTANCE-CAPACITANCE TUN-
imagined to arise from a point source and have ING.
zero width. 2. A thin beam of radiant energy RCV Abbreviation for receive. (Also, rcv.)
(e.g., the beam of electrons in a cathode-ray RCVR Abbreviation for RECEIVER. (Also, rcvr, rx.)
tube). 3. A quantity of radiant energy or ionizing rd Abbreviation for rutherford.
radiation (e.g, gamma ray). 4. One of numerous R & D See R AND D.
lines converging toward, or emanating from, a RD Symbol for DRAIN RESISTANCE.
specific point. 5. A vector representing the direc- Rd 1. Symbol for DIODE RESISTANCE. (Also, rd.)
tion in which an electromagnetic field or acous- 2. Symbol for DISTRIBUTED RESISTANCE.
tic disturbance travels. 6. Also called half line. R-DAT Abbreviation of ROTARY DIGITAL AUDIO
The set of points on a line consisting of a defined TAPE.
origin and all the points on one side of the origin. Rdc Symbol for DC RESISTANCE. (Also, rdc.)
Example: the positive reactance axis in an AR- RDF Abbreviation of RADIO DIRECTION FINDER.
GAND DIAGRAM. Re Symbol for RHENIUM.
Raydist A continuous-wave, medium-frequency Re Symbol for EMITTER RESISTANCE. (Also, rE.)
radionavigation system. The position is deter- REA Abbreviation of Rural Electrification Adminis-
mined according to the phase difference between tration.
two signals transmitted from different locations. reachthrough See PUNCHTHROUGH.
Rayleigh-Carson theorem An expression of the reachthrough region See PUNCHTHROUGH RE-
reciprocal relationship between the transmitting GION.
and receiving properties of an antenna. If voltage reachthrough voltage See PUNCHTHROUGH
E applied to antenna A causes current I to flow at VOLTAGE.
a given point in antenna B, then the same voltage reactance Symbol, X. Unit, ohm. The opposition
(E) applied at that point in antenna B will produce offered to the flow of alternating current by pure
identical current I (same magnitude and phase) capacitance, pure inductance, or a combination
at the point in antenna A, where voltage E of the two. Reactance introduces phase shift. Also
originally was applied. Also see RECIPROCITY see CAPACITIVE REACTANCE and INDUCTIVE
THEOREM. REACTANCE. Compare RESISTANCE.
584 reactance chart • readthrough


reactance chart A nomograph for capacitance, in- reactor 1. An inductor, especially one having very
ductance, and frequency. low internal resistance, used principally for its in-
reactance factor The ratio of the alternating- ductive reactance. 2. A chamber in which the nu-
current resistance of a conductor to the direct- clei of atoms are split to provide atomic energy.
current resistance. The reactance factor generally Also see NUCLEAR REACTOR. 3. In industrial
increases as the frequency increases because of chemistry, a vat in which reactions take place.
skin effect and because the length of the conduc- read 1. In computer operations, to extract data
tor might be a sizable part of the wavelength of from memory or a storage medium and (usually)
the transmitted energy. transfer it to another area of memory or other
reactance modulator A frequency modulator us- medium. Compare WRITE. 2. In digital communi-
ing a variable reactance, usually a varactor diode cations, to transcribe data into printed form. 3. In
in the oscillator. radiotelegraphy, to listen to Morse-code signals
and comprehend the text without necessarily
writing it down. 4. To observe and note the indi-
cation of an instrument, such as a meter.
readability In electronic communications, the de-
gree to which a desired signal can be recognized
To
osc. and interpreted in a given context.
readback In a multiplexer, a feature that facilitates
AF inspection of the contents of the control latch.
in reader A device that transcribes digital signals or
markings into meaningful data. Examples:
Morse-code reader and bar-code reader.
Circuit
read head In a magnetic memory or in a tape
recorder or wire recorder used for data recording,
’ + the head that picks up the magnetic pulses from
Varactor the drum, tape, disk, or wire. Compare WRITE
bias HEAD.
reading rate The number of input characters per
reactance modulator second that a computer or other data-processing
device handles.
read-only memory Abbreviation, ROM. In a com-
reactance transistor A transistor used as a REAC-
puter or calculator, a memory unit in which in-
TANCE MODULATOR.
structions or data are permanently stored for use
reaction-time meter See NEOMATACHOGRAPH
by the machine or for reference by the user. The
and NEOMATACHOMETER.
stored information is read out nondestructively.
reactive absorber In acoustics, a device that dissi-
readout lamp An electron tube containing several
pates impinging sound waves by means of reflec-
cathodes, filled with a gas (such as neon), and
tion, resonance, and other effects, besides
used as a numeric or alphanumeric display de-
dissipation in the form of heat.
vice. Each cathode is connected to a separate pin
reactive attenuator An attenuator that functions
on the base. A single anode is common to all
by means of reactance, rather than by means of
cathodes. The cathode(s) to which a voltage is ap-
resistance.
plied glow(s), showing the shape of a numeral, let-
reactive current The component of alternating
ter of the alphabet, or other symbol. In recent
current that is not in phase with the voltage.
years, this type of display has been replaced by
Compare RESISTIVE CURRENT.
light-emitting diodes (LEDs) and liquid-crystal
reactive kilovolt-ampere Abbreviation, kVAR. A
displays (LCDs).
unit of high apparent power; it is the product of
readout pulse In a random-access memory (RAM),
kilovolts and amperes in a reactive component of
a pulse applied to the word line, facilitating read-
a circuit. Also see APPARENT POWER, KILO-
out of the information in a certain storage slot.
VOLT-AMPERE, REACTIVE VOLT-AMPERE, and
read pulse In computer operations, a pulse that
VOLT-AMPERE.
activates the read function (see READ). Compare
reactive load 1. A load device that is capacitive or
WRITE PULSE.
inductive, rather than resistive. 2. A load device
read rate The number of data units an input read
that contains reactance as well as resistance.
device can transcribe per unit of time [e.g., bits
reactive power See REACTIVE KILOVOLTAM-
per second (bps) and words per minute (wpm)].
PERE and REACTIVE VOLT-AMPERE.
readthrough 1. The reception of signals between
reactive volt-ampere Abbreviation, VAR. A unit of
transmitted pulses at the same frequency.
apparent power; it is the product of volts and am-
2. The continuous monitoring of a signal being
peres in a reactive component of a circuit. Also see
jammed. Any change in the frequency, modula-
APPARENT POWER, KILOVOLT-AMPERE, REAC-
tion, or other characteristics of the signal can
TIVE KILOVOLT-AMPERE, and VOLT-AMPERE.
585
readthrough • receiver front end


then be detected, and the jamming signal translucent, flat surface. The viewer is positioned
adjusted accordingly. on the side of the screen opposite to the project-
read time The period during which data is being ing beam.
transferred from a computer storage unit. Reaumur scale A thermometer scale on which zero
read-write channel In computer operations, a is the freezing point of water and 80 degrees is the
channel over which activity between a central boiling point of water. Compare ABSOLUTE
processing unit and a specific peripheral occurs. SCALE, CELSIUS SCALE, FAHRENHEIT SCALE,
read-write head An electromagnetic transducer and RANKINE SCALE.
used for both reading and writing data. See READ rebecca The airborne interrogator in the British
and WRITE. REBECCA-EUREKA SYSTEM.
read-write memory 1. A small data storage bank rebecca-eureka system A British 90-mile-
for short-term use. The contents of the memory hovering radar navigation system that consists of
are easily changed. 2. See RANDOM ACCESS an airborne interrogator (rebecca) and a ground
MEMORY. transponder beacon (eureka).
real address See ABSOLUTE ADDRESS. rebroadcast The retransmission of a radio broad-
real axis The axis of the real-number component of cast simultaneously by a station other than the
a COMPLEX NUMBER (i.e., the horizontal axis in originator. Also see AUTOMATIC RELAY STATION.
an ARGAND DIAGRAM). rebroadcast station See AUTOMATIC RELAY STA-
real component The real-number part of a COM- TION.
PLEX NUMBER. recalescence During the cooling of a metal, the
real image The image formed on a screen when sudden release of heat. Also see RECALESCENT
rays from the object converge on passing through POINT. Compare DECALESCENCE.
a lens. Compare VIRTUAL IMAGE. recalescent point In a metal whose temperature is
being lowered from a higher value, the tempera-
ture at which heat is suddenly released. Compare
Screen
DECALESCENT POINT.
Lens
recall Abbreviation, RCL. In computers and calcu-
lators, an instruction that brings material from
the memory for examination or use. The opposite
Object
instruction is STORE.
receiver 1. A device or system operated at the des-
Image
tination end of a communication link; it accepts a
signal and processes or converts it for local use.
real image Also see specific entries for various types of re-
ceiver. 2. The earpiece of a telephone. 3. A radio
real number A number in the category that in- broadcast-band tuner integrated with a general-
cludes zero, all rational numbers, and all irra- purpose preamplifier and power amplifier, and
tional numbers. Also see COMPLEX NUMBER, containing standard jacks for input and output of
IMAGINARY NUMBER, IRRATIONAL NUMBER, audio signals to and from peripheral equipment.
and RATIONAL NUMBER. receiver detector In a wireless communications or
real power The apparent power multiplied by the broadcast receiver, a circuit that extracts the in-
power factor in an alternating-current circuit formation from the signal. The design depends on
containing reactance. Real power is the difference the type of emission to be received. See also DIS-
between the apparent power and the reactive CRIMINATOR, ENVELOPE DETECTOR, PHASE-
power. Actual radiated or dissipated power can- LOCKED LOOP, PRODUCT DETECTOR, RATIO
not exceed the real power. DETECTOR.
real time Pertaining to the operation of a computer, receiver dynamic range A quantitative measure of
communications, or data processing system in the ability of a wireless receiver to maintain a
which events are represented or acted on as they fairly constant output, and yet to maintain its
occur. Data is processed as it becomes available, rated sensitivity, in the presence of signals ranging
usually through the use of time-sharing, direct- from very weak to extremely strong. This figure is
access storage devices, and remote terminals. specified in decibels. It is typically 100 dB or more
real-time clock A device that produces periodic in a well-engineered communications receiver.
signals that reflect the interval between events. It receiver front end The portion of a wireless com-
is sometimes used to indicate time of day. munications or broadcast receiver consisting of
rear end The low-frequency portion of a super- the first radio-frequency (RF) amplifier, and often
heterodyne receiver (i.e., the intermediate- also including bandpass filters between this am-
frequency amplifier, second detector, and plifier and the antenna. The dynamic range and
audio-frequency amplifier). Compare FRONT END. sensitivity of a receiver are determined by the per-
rear projection A method of big-screen television formance of this stage. These two characteristics
picture reproduction. The image is focused onto a are among the most important for any receiver.
586 receiver front end • recombination rate


Low-noise, high-gain amplifiers are the rule. receiver sensitivity A quantitative measure of the
Field-effect transistors are commonly used. ability of a wireless receiver to recover weak sig-
receiver IF chain In a wireless communications or nals and process them into readable data. The
broadcast receiver, the series of radio-frequency most common expression is the number of signal
(RF) amplifier stages in which most of the gain microvolts that must exist at the antenna termi-
takes place. These stages are also where the best nals to produce a certain signal-to-noise ratio
possible RF selectivity is obtained. The intermedi- (S/N). Sometimes, the signal-plus-noise-to-noise
ate frequency (IF) on which the amplifiers works ratio (abbreviated S+N/N) is given. The front end,
is a constant frequency. This simplifies the de- or first RF amplifier stage, of a receiver is the
sign of the amplifiers to produce optimum gain most important stage with regard to sensitivity.
and selectivity. Crystal-lattice filters or mechani- Sensitivity is directly related to the gain of this
cal filters are commonly used in these stages to stage, but the amount of noise the stage gener-
obtain the desired bandwidth and response. ates is even more significant. A good front end
receiver mixer In a superheterodyne wireless com- should produce the best possible S/N or S+N/N
munications or broadcast receiver, a stage that ratio at its output. All subsequent stages amplify
converts the variable input signal frequency to a the front-end noise output as well as the front-
constant intermediate frequency (IF), or a stage end signal output.
that converts the first IF to a second IF usually receiving set RADIO RECEIVER.




Y
having a lower frequency. This type of circuit is receiving station A station that ordinarily only re-
nonlinear, and combines the signal with a carrier ceives signals (i.e., it makes no type of transmis-




FL
from a local oscillator (LO). The output is either sion). Compare TRANSMITTING STATION.
the sum or the difference of the signal frequency receptacle 1. See SOCKET. 2. The half of a con-
and the LO frequency. nector that is mounted on a support, such as a
receiver muting See MUTING, 1. panel, and that is therefore stationary.
AM
receiver noise figure A quantitative measure of the recharge In certain cells and batteries, the restora-
ability of a wireless receiver to respond to desired tion of chemical energy following use so that the
signals while rejecting unwanted noise. This can device is ready to deliver its full rated electric cur-
be quantified in various ways. In general, the rent. Also see RECHARGEABLE.
lower the noise figure, the better the sensitivity. rechargeable Pertaining to a secondary cell or bat-
TE

Gallium“arsenide field-effect transistors (GaAs- tery that can accept a restoration of chemical en-
FETs) are well known for the low levels of noise ergy following use, and thus can be completely
they generate, even at quite high frequencies. charged and discharged numerous times. Exam-
Other types of FETs can be used at lower fre- ples: nickel-metal-hydride (NiMH) battery and
quencies. Bipolar transistors tend to be noisy. lead-acid battery.
See also NOISE FACTOR, NOISE FIGURE. reciprocal impedances See INVERSE IMPED-
receiver post-detector stages In a wireless com- ANCES.
munications or broadcast receiver, one or more reciprocal ohm See SIEMENS and MHO.
stages of amplification and/or filtering employed reciprocation 1. The determination of a mathe-
to refine the detector output to a form suitable for matical reciprocal value from a given value.
feeding a speaker, headset, printer, fax machine, 2. The transmission of a message in response to
slow-scan television picture tube, computer, a received message.
electromechanical device, or other peripheral reciprocity in antennas See RAYLEIGH-CARSON
equipment. THEOREM.
receiver primaries See DISPLAY PRIMARIES. reciprocity theorem When a voltage E across
receiver selectivity A quantitative measure of the branch A of a network causes a current I to flow
ability of a wireless receiver to respond to a de- in branch B of the network, the voltage can be ap-
sired signal, but not to undesired ones. The fre- plied across branch B to cause the same value of
quency window is established by a preselector in current to flow in branch A. Compare COM-
the early RF amplification stages, and is honed to PENSATION THEOREM, MAXIMUM POWER
precision by bandpass filters in later amplifier TRANSFER THEOREM, NORTON™S THEOREM,
stages. The preselector passes energy within a SUPERPOSITION THEOREM, and THEVENIN™S
range of about plus-or-minus 10 percent of the THEOREM.
signal frequency; other frequencies are attenu- recombination The refilling of holes by electrons
ated. This reduces the chance for strong, out-of- in a semiconductor.
band signals to impair the performance of recombination current In a transistor circuit,
the receiver. The narrowband filter in the final base current resulting from recombination.
intermediate-frequency (IF) stage responds only recombination rate In a semiconductor material,
to energy within the actual signal band. This the speed at which the electrons and holes re-
minimizes adjacent-channel interference. In combine. It can be expressed as the time
some receivers, yet another bandpass filter is required for a certain proportion of charge carri-
used in the audio-amplifier stages. ers to recombine.




Team-Fly®
587
recompile • rectified alternating current


recompile In computer operations, to COMPILE switched from forward to reverse. 2. The time re-
again, usually according to program amendments quired for a circuit to recover from momentary
following debugging, or to create a different form overdrive. 3. The time required for a computer
of a program so that it will be compatible with system to stabilize following a degenerative oper-
other hardware. ation. 4. The time required for switching a mem-
record 1. See PHONOGRAPH DISC. 2. A chart de- ory from the write to the read mode. It is
livered by a graphic recorder. 3. To make one of measured as the length of time from switching
the foregoing. 4. In data processing, a constituent out of the write mode until meaningful signals oc-
of a file. 5. In data processing, a data unit por- cur at the output. 5. In a transceiver, the time re-
traying a specific transaction. quired from the completion of a transmitted
record blocking In data processing operations, signal until the receiver is activated.
making data blocks from groups of records so rect Abbreviation of RECTIFIER.
that the blocks can, in a single operation, be rectangular coordinates See CARTESIAN COOR-
transferred to a nonvolatile storage medium, DINATES.
such as diskette or tape. rectangular scan 1. A method of beam scanning in
record count A usually running total of a file™s a cathode-ray tube, in which the beam moves se-
records. quentially in parallel lines to cover a rectangular
recorded disc A phonograph disc on which a region. Used in television. 2. In radar, a two-
recording has been made. Also called PRERE- dimensional scan, covering a specific rectangular
CORDED DISC. region.
recorded tape Magnetic tape containing recorded rectangular wave An alternating or pulsating cur-
material. Also called PRERECORDED TAPE. rent or voltage whose rise and decay times are es-
Compare BLANK TAPE. sentially zero, and whose maxima and minima
recorder 1. A machine for preserving sound, video, are essentially flat, but not necessarily of equal
or data signals in the sequence in which they oc- duration. The SQUARE WAVE is a special type of
cur (e.g., DISC RECORDER, TAPE RECORDER, rectangular wave.
and WIRE RECORDER). 2. A machine for making
a permanent visual record (photographically or
+
by stylus) of an electrical phenomenon. Exam-
ples: DRUM RECORDER and OSCILLOGRAPH.
record head See RECORDING HEAD.
recording density In a magnetic storage medium,
the number of information units (bits, bytes, etc.)
represented by magnetized areas, per unit area or
length.
Amplitude




recording disc A phonograph record on which ma-
terial has not been recorded, or from which
Time
recorded material has been removed. Compare
PRERECORDED DISC.
recording head In a magnetic recorder/repro-
ducer, the head that magnetizes the medium in
accordance with sounds or other signals. Also

called RECORD HEAD and WRITE HEAD. Com-
pare PLAYBACK HEAD.
rectangular wave
Recording Industry Association of America Ab-
breviation, RIAA. An organization that sets stan-
dards for audio recording and reproduction in the rectangular waveguide A waveguide having a rect-
United States. angular cross section.
recording instrument A measuring instrument, rectification The conversion of alternating current
such as a voltmeter or ammeter, that makes a into pulsating direct current by any means other
permanent record of its deflections. Also see than the use of a motor-generator. Also see REC-
RECORDER, 2. TIFIER.
recording loss 1. Loss of data during a recording rectification efficiency The ratio (expressed as a
process. 2. Loss resulting from recording effi- percentage) of the direct-current output voltage
ciency of less than 100 percent; audio power loss. to the peak alternating-current input voltage of a
recording tape Magnetic tape on which nothing rectifier.
has been recorded, or from which all data has rectified alternating current The unfiltered, pul-
been erased. Compare PRERECORDED TAPE. sating direct-current output of a rectifier. It con-
recovery time 1. Symbol, t r. The time required for sists of the unidirectional half-cycles passed by
a semiconductor pn junction to attain its high- the rectifier (one per cycle for half-wave rectifica-
resistance state when the bias voltage is suddenly tion, and two per cycle for full-wave rectification).
588 rectifier • reductionism


+4
rectifier Abbreviation, rect. An electronic or elec-
+3
tromechanical device that converts alternating
current into pulsating direct current.
+2
rectifier diode A heavy-duty tube or semiconduc-
+1 Pen
tor diode designed primarily to change alternat-
ing current to pulsating direct current in power 0
’1 0 1 2 3 4 5 6 7 8
supplies. ’1
rectifier filter A circuit containing parallel capaci-
’2
tance, sometimes in combination with series in-
ductance, intended for smoothing out the ripple ’3
in the output of a power-supply rectifier.
’4
Movement of paper

rectilinear chart

controls. Also called REPETITIVE SWEEP. Com-
pare NONREPETITIVE SWEEP.
recursion 1. Generating a complete sequence of
functions or numbers by applying an algorithm to
initial values in the sequence. 2. In computer
programming and artificial intelligence, a logical
process containing loops in calculation or reason-
ing.
recursive Relating to a procedure or set of steps
that repeat endlessly.
Red Book The first format developed for compact-
rectifier-filter system The rectifier plus power- disc data storage media, developed by Sony and
supply-filter combination for converting alternat- Philips. It is commonly used in digital audio sys-
ing current into direct current. tems. See also CD-ROM, GREEN BOOK, OR-
rectifier photocell A photovoltaic cell consisting of ANGE BOOK, and YELLOW BOOK.
two layers of material with a semiconductor junc- red-green-blue Abbreviation, RGB. In video appli-
tion between them. The device produces direct cations, the three primary colors from which all
current when exposed to visible light, infrared, or other colors are derived. Also see COLOR TELE-
ultraviolet radiation. VISION.
rectifier probe A diode-type probe used with a red gun In a three-gun color-television picture
direct-current (dc) voltmeter to measure radio- tube, the electron gun whose (correctly adjusted)
frequency (RF) voltage. The diode rectifies the RF beam strikes only the red phosphor dots on the
signal and presents to the meter a dc voltage pro- screen.
portional to the peak RF voltage. red oxide of iron An iron oxide of the general for-
rectifier stack An assembly of separate rectifier mula Fe2O3, used as the magnetic coating of
disks or plates in series on a central bolt, as in recording tape. Also see IRON OXIDE.
most selenium rectifiers. red oxide of zinc See ZINCITE.
rectifier tube A two-element electron tube, once red-tape operation An operation or function
commonly used for converting alternating cur- needed for organizational purposes, but that does
rent into pulsating direct current in high-voltage, not directly contribute to the completion of the
high-current power supplies. task at hand.
rectifier-type meter See DIODE-TYPE METER. reduced instruction set computer Abbreviation,
rectilinear chart A graphic-recorder chart in RISC. A computer architecture in which program
which the crossing coordinates are arcs, rather instructions are simplified to obtain enhanced
than straight lines, to correspond to the swing of processing speed. It is useful especially in com-
the pen. Also see STRIP CHART. plex graphics, animation, multimedia, and scien-
rectilinear scan See RECTANGULAR SCAN, 1. tific work requiring many calculations.
recurrent network A circuit in which several sec- reductio ad absurdum A method of obtaining a
tions of identical configuration (e.g., L sections) conclusion by proving that its negation results in
are cascaded. a contradiction. It is sometimes used in computer
recurrent phenomenon A phenomenon that re- programming involving mathematical proofs.
peats itself periodically. reduction In an electrochemical cell or battery, a
recurrent sweep In an oscilloscope, a repetitive transfer of electrons to the active chemical.
horizontal sweep of the beam occurring at a fre- reductionism The theory that all human thought
quency determined by the settings of the sweep processes, including emotion and intuition, can
589
reductionism • reflected power


be reduced to digital logic, and thus can be dupli- the beam against a target surface, measured with
cated by a sufficiently powerful computer. It is of respect to the normal (perpendicular) line at the
interest to researchers in artificial intelligence. surface.
reductionist A person who subscribes to the the- reference antenna A standard antenna, such as
ory of REDUCTIONISM. an isotropic radiator or a half-wave dipole, used
redundancy 1. The repetition of components in a to establish a reference for determining the rela-
circuit (e.g., series or parallel connection of them) tive gain of another antenna.
so that one will be available for circuit operation reference bias current In a reference amplifier,
if the other fails. 2. Having available more than the input current that subtracts from the refer-
one method for performing a function. 3. Having ence current. It is generally measured in mi-
on hand several copies of data as a safeguard croamperes.
against data loss. reference current range In a digital-to-analog con-
redundancy check A check for the integrity of dig- verter, the difference between the maximum and
itized data to which extra bits have been added minimum reference current for which the device
for the purpose (e.g., parity check). is within specifications for resolution.
redundant 1. Pertaining to any two units of data reference diode A Zener diode whose constant
that resemble each other in such a manner that if voltage drop is used as a direct-current reference
either unit is removed, no information is lost from potential in calibrator circuits and voltage regula-
the system. 2. A unit of data that contains infor- tors.
mation already present in the system. reference dipole See REFERENCE ANTENNA.
redundant array of independent disks Acronym, reference electrode For use with a pH meter, an
RAID. A set of data storage media used to store electrode that provides a reference potential.
video programs. reference input slew rate In a digital-to-analog
red video voltage In a three-gun color-television converter, the average rate of change in output
circuit, the red-signal voltage that actuates the for a given change in the reference input. It is ex-
red gun. pressed in milliamperes or microamperes per mi-
reed A usually thin metal blade, leaf, or strip used crosecond.
in vibrators, reed-type relays, reed-type oscilla- reference level A specific value of a quantity (e.g.,
tors, and similar devices. current, frequency, power, or voltage) to which
reed oscillator See REED-TYPE OSCILLATOR. other values of the same quantity are referred.
reed relay See DRY-REED SWITCH and reference time The point at which a trigger pulse
MERCURY-WETTED REED RELAY. attains 10 percent of its maximum amplitude.
reed-relay logic Logic circuits using reed relays. reference tone A standard audible tone of known
Also see RELAY LOGIC. frequency [e.g., 440 Hz (representing A below
reed switch 1. A frequency-sensitive switch in middle C)]. Sometimes the intensity as well, as
which the movable contact is mounted on the tip the frequency, is specified.
of a thin, metal strip (reed). The reed is actuated reference white level The television picture signal
by an alternating-current (ac) coil. The reed value representing the uppermost limit for peak
closes the contacts when the ac excitation is at its white signals.
natural frequency. 2. See DRY-REED SWITCH. Reff Symbol for EFFECTIVE RESISTANCE.
reed-type oscillator An electromechanical audio- reflectance 1. See MISMATCH FACTOR. 2. The re-
frequency oscillator whose frequency is con- flected part of the radiant flux striking a surface.
trolled by a vibrating metal strip (reed) instead of It is expressed as a fraction of the total incident
a tuning fork. Also see HUMMER. radiation.
reed-type switch See REED SWITCH. reflected binary code See CYCLIC CODE.
reel 1. The spool around which a magnetic tape or reflected electromagnetic field In a transmission
video film is wound. 2. A spool containing mag- line, the electromagnetic energy not absorbed by
netic tape or video film. the load when an impedance mismatch exists be-
reentrant cavity A resonant cavity in which one or tween the load and the line. See INCIDENT
more sections are directed inward to confine the POWER and REFLECTED POWER.
electric field to a small volume. reflected impedance In a coupled circuit, the
reentrant winding A winding of wire that returns impedance in the secondary that appears in the
to its starting point”especially in a motor arma- primary circuit, or vice-versa, as if it were re-
ture. flected through the coupling transformer.
ref Abbreviation of REFERENCE. reflected power In a transmission line not per-
reference address As a point of reference, an ad- fectly matched to a load at the feed point, an ex-
dress for instructions having relative addresses. pression of the amount of electromagnetic field
reference amplifier A voltage-regulation device reflected from the feed point, rather than ab-
consisting of a transistor and Zener diode in the sorbed by the load. In general, this can be ex-
same envelope. pressed in watts or as a percentage of the
reference angle In radar, the angle of incidence of incident power. It is not a true indicator of the
590 reflected power • refractivity


loss caused by the mismatch because the re- reflection loss 1. Loss caused by the reflection of
flected field is usually all returned again when it an electromagnetic field at a discontinuity in a
arrives back at the transmitter. transmission line. 2. Loss that occurs when an
reflected-power meter A radio-frequency instru- electromagnetic wave is reflected from a surface
ment, connected between a source and a load, or object.
that can measure INCIDENT POWER and RE- reflection phase grating A device that diffuses
FLECTED POWER. sound waves by diffraction effects. The acoustic
reflected ray The ray that is reflected by the sur- equivalent of an electromagnetic-wave DIF-
face of a body or region it strikes. Compare INCI- FRACTION GRATING.
DENT RAY and REFRACTED RAY. reflective code See GRAY CODE.
reflected resistance 1. In a transformer, the effec- reflectivity 1. See MISMATCH FACTOR. 2. The
tive resistance across the primary winding when degree to which a point, plane, or surface reflects
a resistive load is connected to the secondary. the radiation (light, for example) that strikes it.
2. In a transmission line, the resistance at the input reflectometer 1. See REFLECTED-POWER ME-
end when a load is connected to the output end. TER. 2. A type of photometer used to measure re-
reflected wave 1. An electromagnetic wave reflected flection.
by the ionosphere or by the surface of the earth. reflector 1. A smooth, metal surface or wire screen
Compare INCIDENT WAVE and REFRACTED for reflecting radio waves. See, for example,
WAVE. Also see IONOSPHERE and IONOSPHERIC PARABOLIC REFLECTOR. 2. A length of wire,
PROPAGATION. 2. A wave that is bounced off an rod, or tubing used in a parasitic antenna to re-
obstruction, such as a building or mountain. flect radio waves. Compare DIRECTOR and RADI-
reflecting galvanometer A galvanometer having a ATOR. 3. A polished surface for reflecting visible
light-beam pointer. light or infrared rays (i.e., a mirror). 4. See RE-
reflecting shell See IONOSPHERE. PELLER.
reflection 1. The turning back of a ray by a surface reflector element See REFLECTOR, 2.
it strikes. Examples of reflecting media are the reflector satellite A satellite whose skin reflects
surface of the earth, the polished surface of a ma- radio waves.
terial, and a layer of the ionosphere. Compare reflector voltage In a reflex Klystron, the reflector-
REFRACTION. 2. The return of energy to the to-cathode voltage.
source by the mismatched end of a transmission reflex baffle A loudspeaker BAFFLE constructed
line or by the end of a radiator. so that some of the sound radiated to the rear of
reflection error In a radar, radionavigation, or ra- the diaphragm is transmitted forward (after
diolocation system, an error in the reading phase shift) to boost acoustic radiation at some
caused by reflections of the signal from objects frequencies.
other than the intended signal source or object. reflex bunching In a Klystron, electron bunching
reflection factor See MISMATCH FACTOR. following direct-current-field-induced reversal of
reflection law When a ray strikes a smooth reflect- the velocity-modulated electrons. Also see RE-
ing surface, the angle of incidence is equal to the FLEX KLYSTRON.
angle of reflection. reflex circuit A radio receiver circuit in which a
single transistor is used successively for different
functions. For example, one active device can act
Reflected ray as a mixer and as a radio-frequency amplifier.
Tangent plane
reflex Klystron A Klystron having only one cavity.
This cavity serves first as the buncher and then,
as the electrons are turned around and caused to
pass through again, as the catcher.
Surface
refracted ray The ray that is refracted by a body or
region through which it passes. Compare INCI-
DENT RAY and REFLECTED RAY.
refracted wave An electromagnetic wave that is re-
fracted by the ionosphere. Compare INCIDENT
WAVE and REFLECTED WAVE. Also see IONO-
SPHERE and IONOSPHERIC PROPAGATION.
refraction The bending of an energy ray as it
passes through media that cause a change in the
speed of propagation. It can occur with radio
= Angle of incidence
waves, infrared, visible light, ultraviolet, X rays,
= Angle of reflection
Incident ray
gamma rays, and sound waves.
refractive index See INDEX OF REFRACTION.
refractivity The extent of the ability to refract, given
reflection law as the quantity (v1/v2) “ 1, where v1 is the phase
591
refractivity • rejection filter


velocity in free space, and v2 is the phase velocity
in the medium through which a wave passes.
refractory A heat-resistant, nonmetallic ceramic
material.
refrigerator A chamber used to maintain a circuit
or component at a constant temperature that is
lower than the ambient temperature. This device
is analogous to the oven, which maintains a
higher temperature than the surrounding
medium. A refrigerator can be used to maintain
precise frequency for a reference oscillator.
regeneration 1. The processing of a distorted sig-
nal so that it has its original characteristics.
2. Positive feedback generally used for the purpose 3. See CURRENT REGULATION. 4. See VOLT-
of causing oscillation, or for detection in a regen- AGE REGULATION.
erative receiver. See POSITIVE FEEDBACK. regulator 1. A device that automatically holds a
regeneration period The period during which the quantity to a constant value (e.g., a voltage regu-
electron beam scans a cathode-ray tube screen to lator). 2. A device via which a quantity can be var-
restore changes to the screen surface. ied (e.g., potentiometer, rheostat, and variable
regenerative amplifier An amplifier that uses re- autotransformer).
generation to increase its gain and/or selectivity. regulator diode A semiconductor diode”espe-
regenerative detector A detector provided with re- cially a Zener diode used as a two-terminal volt-
generative feedback. Although such a detector is age regulator.
sensitive, it can be unstable. Compare NONRE- reinitialization The setting of all lines in a micro-
GENERATIVE DETECTOR. computer or microprocessor to logic zero auto-
regenerative feedback Feedback producing re- matically when power is removed, then reapplied.
generation (i.e., positive feedback). Compare DE- reject amplifier A tuned amplifier having the re-
GENERATIVE FEEDBACK. sponse of a band-suppression filter. Like the fil-
regenerative IF amplifier An intermediate- ter, the amplifier rejects or severely attenuates
frequency amplifier in which regeneration is intro- one frequency (or band of frequencies) while read-
duced to boost sensitivity and, sometimes, ily passing lower and higher frequencies. Com-
selectivity. pare PASS AMPLIFIER.
regenerative reading A method of reading data reject filter See REJECTION FILTER.
(see READ) so that it is automatically restored, by rejection circuit A circuit performing the function
writing, to locations from which it came. of a REJECTION FILTER.
register In computer systems, an arrangement of rejection filter A filter that suppresses one fre-
several storage devices, such as flip-flops, for quency (or band of frequencies) while passing all
storing a certain number of digits (a two-bit regis- other frequencies.
ter, for example, requires two flip-flops).
register capacity The range of values for quanti-
ties that can be handled by a register.
Input Output
registered professional engineer A title granted
by a state board of examiners to a person licensed
to work as an engineer.
register length The number of characters or bits
that can be held in a register, according to its ca-
pacity.
registration The accurate alignment of terminals
or other points on different components or on op-
posite sides of a board so that when the surfaces
containing those points are overlaid, all points
mate precisely.
regulated power supply A power supply whose
output is held automatically to a constant level or
within a narrow range, regardless of loading vari-
ations.
regulating transformer See VOLTAGE-REGULAT-
ING TRANSFORMER.
regulation 1. In general, the adjustment or control
of a component, device, or system. 2. Automatic
control. See, for example, SELF-REGULATION. rejection filter
592 rejection notch • reluctance motor


rejection notch A sharp dip in the transmission relaxation time 1. The time required for an expo-
characteristic of a crystal filter. It provides rejec- nentially decreasing variable to fall to 1/e (ap-
tion-filter action at the notch frequency. Also see proximately 36.8 percent) of its initial value,
CRYSTAL RESONATOR and REJECTION FILTER. where e is the natural-logarithm base (approxi-
rejectivity The degree to which a selective circuit mately 2.71828). 2. For a gas, the time required
rejects an unwanted signal. Compare TRANSMIT- for it to return to its original state after having
TIVITY. been disturbed.
rejuvenation See REACTIVATION. relay 1. A signal-actuated switching device. In
rel Symbol, R. The cgs unit of reluctance, equiva- most instances, a relatively weak current or volt-
lent to gilberts per maxwell. age is used to make the relay switch a higher cur-
relative accuracy In a measuring instrument, the rent or voltage. A relay can be electromechanical
error determined as a percentage of the actual or fully electronic (no moving parts). See, for ex-
value; the difference between the actual and mea- ample, ELECTROMECHANICAL RELAY and
sured values, divided by the actual value, then ELECTRONIC RELAY. 2. A repeater station. 3. In
multiplied by 100. communications, to receive a message and re-
relative address In the address part of a computer transmit it en route from a source to a destina-
program instruction, a number specifying a loca- tion.
tion relative to a BASE ADDRESS. When the base relay amplifier See RELAY DRIVER.
address is added to the relative address, it yields relay booster See RELAY DRIVER.
the ABSOLUTE ADDRESS. relay driver A direct-current amplifier (usually one
relative error The ratio of the absolute error to the stage) used to actuate an electromechanical relay
exact value of a quantity. in response to a low-powered signal.
relative gain The current, voltage, or power gain, relay flip-flop See BISTABLE RELAY.
measured, with respect to a reference standard. relay logic Abbreviation, RL. In computer and
relative humidity Abbreviation, rh. The ratio, as a industrial-control operations, a logic system us-
percentage, of the amount of moisture in the air ing electromechanical relays as flip-flops (see
to the amount the air could contain at a given BISTABLE RELAY).
temperature. Compare ABSOLUTE HUMIDITY. relay transmitter See AUTOMATIC REPEATER
relative luminosity Luminosity measured with re- STATION.
spect to a reference level. release time 1. The interval between the instant
relative permeability The ratio of the permeability power is removed from a relay and the instant
of a given material to the permeability of another the armature is released sufficiently to operate
material (or of the same material under different the contacts. 2. The time between one control in-
conditions). put becoming inactive and another becoming ac-
relative power Power level specified with respect tive. 3. The time required for reception to
to another (often reference) power level. resume in a transceiver, once transmission has
relative uncertainty The uncertainty of a mea- stopped. 4. An expression for the rapidity with
surement divided by the measured value. The which an automatic gain control reverts to max-
maximum value that this quotient can have is 1. imum sensitivity following the reception of a
Also see UNCERTAINTY IN MEASUREMENT. strong signal.
relative visibility Response of the human eye to reliability 1. The dependability of operation of a
light. This is relative because the eye does not see device or circuit under specified conditions.
equally well throughout the visible spectrum. The 2. The proportion of units that still work after a
peak response of the human eye is around 5.4 — set of units has been in use for a specified length
1014 Hz; this represents yellow-green light. Photo- of time.
electric devices have peak responses that can dif- reliability engineering The branch of engineering
fer considerably from this value. devoted to the theory and application of reliabil-
relativity theory See EINSTEIN™S THEORY. ity; based on fundamental engineering and ad-
relaxation A delayed change in circuit conditions, vanced statistical concepts.
as a result of change in the input. reluctance Symbol, R. SI unit, A/Wb; cgs unit, rel.
relaxation inverter An inverter circuit in which In a magnetic circuit, the opposition to the estab-
the direct-to-alternating-current conversion de- lishment of a magnetic field; it is analogous to re-
vice is a RELAXATION OSCILLATOR. sistance in electric circuits.
relaxation oscillator An oscillator whose operation reluctance motor An electric motor having a
results from the buildup of a charge in a capaci- squirrel-cage rotor with some of its teeth ground
tor, followed by sudden discharge of the capacitor, down, and a shaded-pole or split-phase type of
the sequence being repeated periodically. In one stator that supplies a rotating magnetic field.
circuit, a capacitor is connected in series with a When starting, this motor comes up to speed like
resistor and a direct-current power supply, and a an induction motor, but the protruding teeth of
neon bulb is connected in parallel with the capac- the rotor then follow the field in the manner of the
itor. The output is a sawtooth wave. poles of a hysteresis motor.
593
reluctivity • replacement


reluctivity Specific reluctance (i.e., the reluctance rendering In three-dimensional computer anima-
of a sample of magnetic material one centimeter tion, the software process in which all the aspects
long and one square centimeter in cross section). of the model are combined to obtain the presen-
Reluctivity is the reciprocal of permeability. tation.
rem Acronym for roentgen equivalent man, an rep 1. Acronym for roentgen equivalent physical,
amount of ionizing radiation having the same ef- an amount of ionizing radiation that, upon ab-
fect on the body as a one-roentgen dose of gamma sorption by body tissue, will develop the energy of
or X radiation. a one-roentgen dose of gamma or X radiation.
remagnetizer A magnetizer used principally to re- 2. Colloquial abbreviation for repetition, as in rep
store weakened permanent magnets. rate. 3. Colloquial abbreviation for representative,
remainder 1. The result of subtracting one quan- as in service representative.
tity (the subtrahend) from another (the minuend). repeatability The ability of an instrument, system,
Also called DIFFERENCE. 2. In division, the nu- or method to give identical performance or results
merical value left over after the integral part of in successive instances.
the quotient has been determined; it becomes the repeater A receiver/transmitter device that re-
fractional part when divided by the divisor. For transmits a signal it receives from another
example, in 25/3, the remainder is 1. source, often simultaneously. In this way, a sig-
remanence See RESIDUAL MAGNETISM. nal can be transmitted on several frequencies, or
remanent flux density See REMANENCE. the service area of the original station can be ex-
remodulator Any device that changes the modula- tended. Also see ONE-WAY REPEATER and TWO-
tion of a signal from one form to another, such as WAY REPEATER.
from frequency modulation to amplitude modula-
tion, without loss of intelligence.
Receive Transmit
remote alarm In security systems, an alarm that
antenna antenna
occurs at a location different from where an in-
trusion occurs (e.g., at the headquarters of a se-
curity company).
remote control Control of distant devices by me-
chanical means or by radio-frequency signals
Isolator
sent from a transmitter especially designed for
the purpose; in the latter case, it is sometimes
called radio control.
remote-control receiver The complete device that Receiver Transmitter
selects, amplifies, and demodulates or rectifies a
radio signal for control of a circuit or mechanism
at a distance from the transmitter of the control repeater
signal. Some receivers have self-contained anten-
nas.
remote-control transmitter The complete device repeater station See AUTOMATIC REPEATER
that generates radio-frequency power, adds to it STATION and REPEATER.
the signals needed for remote control, and radi- repeating decimal A decimal fraction in which
ates the modified power. groups of digits recur endlessly (e.g., 25/99 =
remote-control system The complete set of hard- 0.252525. . .).
ware units and software programs facilitating the repeller An electrode, especially in a velocity-mod-
operation of a computer or robot from a distance. ulated tube, for reversing the direction of an elec-
remote data terminal In a computer system, a tron beam.
terminal connected to the central processor by a repertoire The instruction set for a particular ob-
telephone line or radio link. It is used for the ject or source computer programming language.
transfer of data without providing control of the repetition instruction In a loop in a computer
system. Also called remote data station. program, an instruction that causes the repeti-
remote error sensing A method of regulation used tive implementation of one or more instructions.
in some power supplies. The voltage across the repetitive phenomenon See RECURRENT PHE-
load, or the current through the load, is deter- NOMENON.
mined by remote control. The power-supply out- repetitive sweep See RECURRENT SWEEP.
put is adjusted to compensate for losses in the replication In an electronic system, especially in a

<<

. 32
( 42)



>>