. 33
( 42)


system. computer, the redundancy of hardware units to
remote job entry In computer operations, the key- provide standby facilities in case of failure.
ing-in of input data at a site physically distant replacement A component or circuit that can be
from the central processor. substituted directly for another; it fits exactly into
remote tuning The electrical or radio tuning of a place and functions exactly like the component it
circuit or device from a distance. replaces, without modification to the equipment.
594 report • resilience

report 1. The results of testing and evaluation of a tional again so that it can detect subsequent in-
device, organized into a written document. 2. The trusions should they occur.
output of a computer, printed on paper for per- reset action 1. The return of a circuit or device to
manent reference. its normal operating condition. 2. A method of
report program generator Abbreviation, RPG. A adjusting a circuit to compensate for the severity
computer programming language with which pro- of an abnormal condition. The extent of readjust-
grams can be produced for the generation of busi- ment is determined by the extent of the departure
ness reports. from normal conditions.
reproduce head See PLAYBACK HEAD. reset generator A circuit or device that generates a
reproducing stylus A stylus for the playback of pulse for resetting a flip-flop or counter. Also see
material from a phonograph disc. RESET and RESET TERMINAL.
reproduction 1. The recovery of data from storage, reset pulse A pulse that resets (see RESET, 1) a
and its presentation in original form. 2. Data ob- storage cell in a computer memory.
tained by the process defined in 1. 3. See PLAY- reset terminal In a flip-flop, the zero-input termi-
BACK. nal. Compare SET TERMINAL.
reproduction loss See PLAYBACK LOSS. reset time The elapsed time between a malfunc-
repulsion A force that pushes objects away from tion and the completion of the reset action.
each other, as between similar electric charges or reset timer A device that returns a circuit or de-
similar magnetic poles. Compare ATTRACTION. vice to its initial state after a specified time delay.
Also see LAW OF REPULSION. reserve In multiple programming computer opera-
repulsion-induction motor An alternating- tions, to allocate memory areas and peripherals
current motor arranged to start as a REPULSION for a program.
MOTOR and run as an INDUCTION MOTOR, but reserve battery A battery in which the electrolyte
with better regulation than that of the latter. is in a special standby chamber outside of the in-
repulsion motor An alternating-current motor terelectrode section while the battery is on the
having an armature and commutator similar to shelf. When the battery is readied for service, the
those of a direct-current motor, and a stator sim- electrolyte is caused to flow into position between
ilar to that of a split-phase motor, without the the electrodes, either by heating the battery,
auxiliary starting winding. Repulsion caused by shocking it mechanically, or inverting it.
the negative half-cycle of torque is utilized to drive residual amplitude modulation See INCIDENTAL
the armature, by placing the brushes in such a AM.
way that they close the coils only when the latter residual charge The electric charge remaining in a
are in position to receive this repulsive action. capacitor after it has been initially discharged. It
repulsion-start motor An alternating-current mo- results from dielectric absorption.
tor that starts as a REPLUSION MOTOR but at residual current A current that continues to flow
approximately 75 percent of full speed. Its com- in a circuit after removing power. The duration is
mutator is automatically short-circuited and the measured in nanoseconds or microseconds.
motor runs as an INDUCTION MOTOR. Also see residual frequency modulation 1. See INCIDEN-
REPULSION INDUCTION MOTOR. TAL FM. 2. Frequency modulation of the funda-
request slip In computer operations, peripheral mental frequency of a Klystron by noise or
and memory needs for a program given in a writ- alternating-current heater voltage.
ten statement. residual gas Minute quantities of gas remaining in
reradiation Radiation of energy by a body that has a vacuum tube after evacuation.
been exposed to radiation, as when a receiving residual magnetism Magnetism remaining in a
antenna retransmits a signal. material, such as iron, after the magnetizing force
rerecording A recording of played-back material. has been removed.
reroute 1. In computer operations, to establish new residual modulation 1. Modulation of a signal by
channels between peripherals and main memory. hum or noise. 2. See INCIDENTAL AM. 3. See IN-
2. To establish new circuit paths, physically (as by CIDENTAL FM.
changing conductor orientation) or electronically residual voltage In the output of a null device,
(as by selecting an alternate signal bus). such as a bridge, a usually small voltage still pre-
rerun See ROLLBACK. sent at null and preventing zero balance.
res 1. Abbreviation of RESISTANCE or RESISTOR. residue check In computer operations, the verifica-
(Also, R and r.) 2. Abbreviation of RESEARCH. 3. tion of the result of an arithmetic operation using
Abbreviation of RESOLUTION. the remainders generated when each operand is di-
reset 1. The clearing of a flip-flop of data in storage vided by a special number; the remainder is trans-
(i.e., the setting of the flip-flop to its zero state). 2. mitted along with the operand as a check digit.
In a computer program, an instruction to initial- resilience Also called fault resilience. The ability of
ize the value of a variable. 3. In a security system, an electronic device or system, especially a com-
a function that terminates an alarm signal follow- puter, to keep functioning after part of it has
ing an intrusion, and renders the system opera- failed.
resin • resistance-inductance circuit

resin A natural or synthetic organic substance resistance-capacitance circuit A circuit contain-
that is polymeric in structure and largely amor- ing only resistors and capacitors. There are no in-
phous. Various plastics are made from synthetic ductors.
resins. resistance-capacitance-coupled amplifier A
resistance 1. Symbol, R or r. Unit, ohm. In a de- multistage amplifier circuit in which RESIS-
vice, component, or circuit, the simple opposition TANCE-CAPACITANCE COUPLING is used be-
to current flow. Resistance by itself causes no tween stages and at the input and output points
phase shift. In a purely resistive circuit, R = E/I, of the circuit.
where R is the resistance in ohms, E is the voltage resistance-capacitance coupling Coupling, espe-
in volts, and I is the current in amperes. 2. A cially between stages in a circuit, using blocking
property of circuits, devices, or substances that capacitors and supply-path resistors.
causes impinging energy to be dissipated by con- resistance-capacitance filter A power-supply fil-
version to heat. Compare REACTANCE. ter or wave filter containing only resistors and ca-
pacitors. The resistors are in the positions
occupied by inductors in inductance-capacitance
Per kilometer of solid copper wire for American Wire Gauge resistance-capacitance-inductance Abbrevia-
(AWG) 1 through 40. tion, RCL. Pertaining to a combination of resis-
AWG ohms/km AWG ohms/km tance, capacitance, and inductance.
1 0.42 21 43 resistance-capacitance phase shifter A phase
2 0.52 22 54 shifter containing only resistors and capacitors to
3 0.66 23 68 obtain the desired shift.
4 0.83 24 86
5 1.0 25 110
6 1.3 26 140
7 1.7 27 170
8 2.1 28 220
9 2.7 29 270
10 3.3 30 350

11 4.2 31 440
12 5.3 32 550
13 6.7 33 690
resistance-capacitance phase shifter
14 8.4 34 870
15 11 35 1100
16 13 36 1400 resistance-capacitance time constant Symbol, t.
17 17 37 1700 The time constant (see ELECTRICAL TIME CON-
18 21 38 2200 STANT) of a circuit containing (ideally) only resis-
19 27 39 2800 tance and capacitance; t = RC, where t is in
20 34 40 3500 seconds, R is in ohms, and C is in farads. Compare
resistance-capacitance tuning Tuning of a cir-
resistance alloys Metallic alloys used in the man-
cuit, such as that of an amplifier or oscillator, by
ufacture of resistance wire and resistance ele-
means of a variable resistor or ganged units of
ments. Such alloys include CONSTANTAN,
this type. See, for example, PARALLEL-TEE AM-
resistance balance A device used to balance a cir-
resistance-coupled amplifier See RESISTANCE-
cuit, by means of the insertion of resistances.
resistance brazing A method of brazing in which
resistance drop The voltage drop across a resistor,
metal is heated by passing a current through it.
The I 2R loss, or dissipated power, occurs in the or across the inherent resistance of a device.
resistance-inductance Abbreviation, RL. Pertain-
form of heat.
ing to a combination of resistance and inductance
resistance bridge A bridge (see BRIDGE, 2) for
measuring resistance only.
resistance-inductance bridge 1. A four-arm null
resistance-capacitance Abbreviation, RC. Pertain-
circuit containing only resistors and inductors.
ing to a combination of resistance and capacitance
Also see BRIDGE, 1. 2. An alternating-current
bridge (see BRIDGE, 2) for measuring resistance
resistance-capacitance bridge 1. A four-arm null
and inductance only.
circuit containing only resistors and capacitors.
resistance-inductance circuit A circuit contain-
Also see BRIDGE, 1. 2. An alternating-current
ing only resistors and inductors. There are no ca-
bridge (see BRIDGE, 2) for measuring resistance
and capacitance.
596 resistance-inductance phase shifter • resistors in series-parallel

resistance-inductance phase shifter A phase exhibits significant resistivity. See, for example,
shifter containing only resistors and inductors to RESISTANCE ALLOYS and RESISTANCE METAL.
obtain the desired phase shift. resistance-wire sensor A specific length of resis-
tance wire, properly mounted, whose resistance
is proportional to a sensed phenomenon (such as
EL ER strain, temperature, presence of gas, pressure,
etc.). See, for example, ELECTRICAL STRAIN
resistive current The component of alternating
current that is in phase with voltage. Also called
resistive cutoff frequency Symbol, frco. The fre-
quency beyond which a tunnel diode ceases to ex-
hibit negative resistance.
resistance-inductance phase shifter
resistive load A load device that is essentially a
pure resistance.
resistance lamp An incandescent bulb inserted in resistive losses Losses resulting from the resis-

series with a circuit to provide a dropping resis- tance of a circuit or device, and usually appearing
tance. Such a lamp is capable of dissipating a as heat.

large amount of power, shows very little reac- resistive transducer A transducer in which the
tance at low frequencies, and is inexpensive. sensed phenomenon causes a change in resis-
resistance magnetometer A magnetometer whose tance, which in turn produces a corresponding
operation is based upon the change of electrical change in output current or voltage. Compare
resistance of a material (such as bismuth wire) CAPACITIVE TRANSDUCER, CRYSTAL TRANS-
placed in the magnetic field under test. DUCER, INDUCTIVE TRANSDUCER, MAGNETIC
resistance material A substance, such as carbon TRANSDUCER, and PHOTOELECTRIC TRANS-
or German silver, whose resistivity is high DUCER.
enough to enable its use as a lumped resistor. resistive trimmer See TRIMMER RESISTOR.

See, for example, RESISTANCE ALLOYS and RE- resistive voltage The voltage across the resistance
SISTANCE METAL. component in a circuit. In an alternating-current
resistance metal A metal, such as iron, whose re- circuit, the resistive voltage is in phase with the
sistivity is high enough to enable its use as a current.
lumped resistor. Also see RESISTANCE ALLOYS. resistivity Symbol, r. Resistance per unit volume
resistance pad An attenuator composed of nonin- or per unit area. It can be expressed in terms of
ductive resistors. ohms per cubic meter or ohms per square meter.
resistance standard A highly accurate and stable Also see MICROHM-CENTIMETER and OHM-
resistor used in precision measurements of resis- CENTIMETER.
tance. Also see PRIMARY STANDARD and SEC- resistor A device having resistance concentrated in
ONDARY STANDARD. lumped form. Also see RESISTANCE and RESIS-
resistance strain gauge An electrical strain gauge TIVITY.
in which the stressed element is a thin resistance resistor-capacitor-transistor logic Abbreviation,
resistance strip A strip of metallic or nonmetallic in which capacitors are used to enhance switch-
resistance material. Also see RESISTANCE AL- ing speed.
LOYS and RESISTANCE METAL. resistor color code See COLOR CODE.
resistance temperature detector A transducer resistor core A form around which a resistance
consisting of a specially made resistor whose re- wire can be wound for the purpose of construct-
sistance varies linearly with temperature. ing a high-power resistor.
resistance thermometer An electronic thermome- resistor decade See DECADE RESISTOR.
ter whose operation is based on the change of re- resistor diode A usually forward-biased semicon-
sistance of a wire as it is heated or cooled. ductor diode that acts as a VOLTAGE-DEPEN-
resistance transducer See RESISTIVE TRANS- DENT RESISTOR.
resistance tuning See VARIABLE-RESISTANCE resistor fuse See FUSIBLE RESISTOR.
TUNING. resistors in parallel See PARALLEL RESISTORS.
resistance welding An electrical or electronic resistors in parallel-series See PARALLEL-
welding process in which the workpieces are SERIES RESISTORS.
heated by current flowing through the inherent resistors in series See SERIES RESISTORS.
resistance of their junction. resistors in series-parallel See SERIES-
resistance wire Wire made of a metal or alloy that PARALLEL RESISTORS.

resistor substitution box • resonant-line oscillator

resistor substitution box A self-contained assort- variations in the frequency of an applied sound or
ment of common-value resistors arranged to be signal. Such curves are almost always plotted in
switched one at a time to a pair of terminals. In rectangular coordinates with frequency as the in-
troubleshooting and circuit development, any of dependent variable on the horizontal axis. The de-
several useful fixed resistance values can thus be pendent variable, plotted on the vertical axis, can
obtained. be any characteristic that displays a peak or dip
resistor transistor See ELECTRONIC RESISTOR. at the resonant frequency or frequencies. In radio-
resistor-transistor logic Abbreviation, RTL. A cir- frequency circuits, such parameters include cur-
cuit in which the logic function is performed by rent, voltage, attenuation, gain, and impedance.
resistors, and an inverted output is provided by resonance theory of hearing The theory that
transistors. sound waves pass down the auditory canal and
resnatron A form of vacuum tube that is used as cause the eardrum to vibrate. Behind the
an oscillator and amplifier at ultra-high and mi- eardrum is a system of three bones leading to the
crowave frequencies. It is essentially a cavity res- cochlea. The cochlea consists of fibers that res-
onator. onate. Therefore, they vary in length and tension.
resolution 1. The degree to which closely adjacent Various groups of fibers are activated by different
parts of an image can be differentiated. 2. The re- sounds, and the vibrations are transmitted to
duction of a problem by means of logical analysis. nerves leading to the brain.
3. The ability of a vision or ranging system to dis- resonance radiation Electromagnetic radiation
tinguish between objects that are close together from an energized substance, resulting from
in terms of radial distance, direction, or absolute movement of electrons from a higher to lower en-
separation. ergy level. When an electron moves from a higher
resolution ratio In a television image, the ratio of to a lower orbit, a photon, having a definite wave-
horizontal resolution to vertical resolution. length, is emitted.
resonance 1. The state in which the natural re- resonant cavity A chamber whose size reinforces
sponse frequency of a circuit coincides with the energy injected into it at a natural frequency,
frequency of an applied signal, or vice versa, which is determined by the chamber™s dimen-
yielding intensified response. 2. The state in sions. Such cavities can be used with acoustic or
which the natural vibration frequency of a body electromagnetic waves.
coincides with an applied vibration force, or vice resonant circuit A circuit whose constants are
versa, yielding reinforced vibration of the body. chosen for maximum circuit response at a given
resonance bridge An alternating-current bridge frequency. Examples: parallel-resonant circuit
(see BRIDGE, 2) in which one or two arms are and series-resonant circuit. Also see RESONANCE
series-resonant or parallel-resonant, the other and RESONANT FREQUENCY.
arms being resistances. Also see SERIES-TYPE resonant current Current flowing in a tuned cir-
RESONANCE BRIDGE and SHUNT-TYPE RESO- cuit at resonance.
NANCE BRIDGE. resonant feeder An antenna feeder that is reso-
resonance curve A graph of the insertion gain or nant at the operating frequency.
loss of a component, device, circuit, or system to resonant filter A filter containing at least one se-
ries- or parallel-resonant arm for sharp response.
Thus, a power-supply filter of this kind might
have a parallel-resonant arm acting as a wave-
trap at the ripple frequency.
resonant frequency Symbol, fr or fo. The natural
frequency at which a circuit oscillates or a device
Current or voltage

vibrates. In an inductance-capacitance circuit
(series-resonant or parallel-resonant), the reac-
tances cancel at the resonant frequency, leaving
only resistance.
resonant-gate transistor A transistor embodying
a tiny tuning fork for resonance at low frequen-
cies, thus eliminating bulky coils and capacitors.
resonant line A transmission line that is resonant
at the operating frequency.
resonant-line amplifier See LINE-TYPE AMPLI-
resonant-line circuit A circuit using resonant
lines as a tank. See, for example, LINE-TYPE
resonant-line oscillator See LINE-TYPE OSCILLA-
resonance curve
598 resonant-line wavemeter • reverberation system

resonant-line wavemeter See LECHER WIRES. ders the retrace line invisible on the screen so
resonant rise See VOLTAGE RISE. that it will not interfere with the display.
resonant-slope amplifier See DIELECTRIC AMP- retrace line See RETRACE, 2.
LIFIER. retrace ratio For the swept beam in a cathode-ray
resonant-slope detector See SLOPE DETECTOR. tube, the ratio of the scanning velocity in the
resonant suckout The drawing of radio-frequency trace direction to the scanning velocity in the RE-
energy out of the energized part of a coil or trans- TRACE direction.
mission line by the part not intended to be ener- retrace time In a cathode-ray tube, the amount of
gized, when the latter resonates at the same time required for the scanning beam to move
frequency. from the end of one trace or line to the beginning
resonant-voltage rise See VOLTAGE RISE. of the next.
resonant-voltage stepup See VOLTAGE RISE. retrofit To supply something with specially de-
resonate 1. To exhibit RESONANCE”either elec- signed or adapted parts that were not available
trically or acoustically. 2. To adjust a variable- when it was made.
frequency electrical or acoustical device so that it retrograde orbit For an artificial earth satellite, an
exhibits RESONANCE at a specific frequency. orbit whose direction is east-to-west, relative to
resonator A device that produces or undergoes the earth™s surface.
resonance. See, for example, HELMHOLTZ RES- return 1. See RETRACE. 2. See RETURN CIRCUIT.
ONATOR and RESONANT CAVITY. 3. See RETURN POINT. 4. In an electronic circuit,
resource A part of a computer system that can be the electrical ground and ground current path.
used for a specific application as a unit (e.g., return circuit The circuit through which current
printer, PCMCIA standard adapter card, tape returns to a generator.
drive, etc.). return instruction In a computer program, an in-
responder The transmitting section of a transpon- struction in a subroutine directing operation
der. back to a specific point in the main program.
response The behavior of a circuit or device (espe- return interval See RETRACE TIME.
cially in terms of its dependent variables), in ac- return line See RETRACE, 2.
cordance with an applied signal (e.g., frequency return point 1. The point to which circuits are re-
response and current-vs.-voltage response). turned (e.g., a common ground point). 2. The ter-
response curve A graph depicting the perfor- minal point of a return circuit.
mance of a circuit or device. Examples: attenua- return ratio See FEEDBACK FACTOR.
tion-vs.-frequency curve and current-vs.-voltage return time See RETRACE TIME.
curve. return to zero 1. Abbreviation RZ or RTZ. In the
response time The interval between the instant a magnetic recording of data, a method in which the
signal is applied to or removed from a circuit or write current returns to zero following the write
device and the instant that the circuit acts ac- pulse. Compare NONRETURN-TO-ZERO. 2. A
cordingly. logic system in which the zero and one states are
restart Following a malfunction or error occurring represented by zero voltage and a discrete voltage.
during a computer program run, to go back to an return trace See RETRACE, 1, 2.
earlier point in the program. REV 1. Abbreviation of REENTRY VEHICLE. 2. Ab-
resting state See QUIESCENT STATE. breviation of REVERSE.
restore See RESET. rev 1. Abbreviation of REVOLUTION. 2. To quickly
resultant 1. The vector that results from the addi- and substantially increase the angular velocity of
tion of two or more vectors. 2. A quantity that re- a motor.
sults from mathematical operations performed on reverberation 1. Multiple reflections of sound
other quantities. waves from the inside surfaces of an enclosed
retarding magnet See DRAG MAGNET. chamber. 2. The dying-out of sound waves in an
retentivity 1. The property whereby a material re- enclosed chamber as the waves reflect repeatedly
tains magnetism imparted to it. 2. A quantitative from the inside surfaces. 3. In sound recording
measure of the extent to which a material retains and/or reproduction, an electronically produced
magnetism imparted to it. echo. It is used for special effects”especially in
retention period In computer operations, the time electronic music systems. 4. See RESONANCE, 2.
during which the data on a magnetic medium reverberation chamber A room in which the walls,
(disk or tape) must be kept intact. floor, and ceiling absorb very little sound, result-
retrace 1. In a cathode-ray tube, the return of the ing in echoes. To avoid standing waves, the room
scanning beam to its starting point. 2. In a cath- is designed so that no two surfaces are exactly
ode-ray tube, a line traced on the screen by the parallel.
scanning beam as it returns to its starting point, reverberation system A system of devices oper-
if RETRACE BLANKING is not used. ated with an electronic organ to simulate the ef-
retrace blanking Obliteration of the RETRACE of fect of reverberation in a large room, such as a
the electron beam in a cathode-ray tube. It ren- church auditorium.
reverberation time • revolution

reverberation time In an enclosed chamber, the reverse engineering A design process in which a
time required for a sound to die down to a speci- specific device or system is copied functionally,
fied level (usually -60 dB) after the disturbance but not literally.
has stopped. reverse Polish notation Abbreviation, RPN. A sys-
reverberation unit A device for producing artificial tem of notation for expressing mathematical op-
echoes”especially in the operation of electronic erations in which the operators follow the
music systems. operands being manipulated. It is a mode of entry
for some calculators (e.g., the operation 7 — 2
reverse 1. To alter the direction of a current or pro-
cess or motion of an object so that the new direc- might be entered by pressing keys in this order:
7, ENTER, 2, —).
tion is exactly opposite the previous direction.
2. In a directional wattmeter, the reflected-power reverse recovery time See RECOVERY TIME, 1.
indication or switch position. reverse resistance Symbol, Rr. The resistance of a
reverse AGC Automatic gain control in which a reverse-biased pn junction. Also called BACK RE-
signal-dependent voltage is fed back to an earlier SISTANCE. Compare FORWARD RESISTANCE.
stage to adjust its gain automatically. Compare reverse voltage Symbol, Er or Vr. Direct-current
FORWARD AGC. voltage applied to a pn junction so that the
reverse bias Reverse voltage or current in a tran- p-type material is electrically more negative than
sistor or a semiconductor diode. Compare FOR- the n-type material. Also called BACK VOLTAGE.
reverse-voltage capacitance The internal capaci-
tance of a reverse-biased semiconductor pn junc-
reverse voltage drop The voltage drop across a
semiconductor pn junction that is biased in the
reverse (low-conduction) direction.
reversible counter A counter that, by a control
signal, can have the value it is holding either in-
creased or decreased.
reversible permeability The permeability of a fer-
’ romagnetic substance when the magnitude of the
alternating-current field is arbitrarily small.
reversing switch 1. A switch that reverses the po-
larity of a direct-current voltage. 2. A switch that
reverses the direction of motor rotation.



Input Ganged

reverse bias

reverse breakdown See AVALANCHE.
reverse breakdown voltage See AVALANCHE reversing switch
reverse characteristic The current-vs.-voltage re-
revolute geometry A method by which a robot
sponse of a semiconductor junction that is biased
arm can move freely in three dimensions. The en-
in the reverse (low-conduction) direction. Com-
tire assembly rotates from the base in a horizon-
tal plane through a complete circle (360 degrees).
reverse conduction The very small current con-
An elevation joint at the base moves the arm from
duction through a pn junction when it is reverse-
horizontal to vertical (90 degrees). A joint in the
middle of the arm can bend through about 180
reverse current Symbol, Ir. The current that flows
through a pn junction when it is reverse-biased.
revolution Abbreviation, r or rev. One complete ro-
Also called back current. Compare FORWARD
tation (i.e., 360 degrees of circular travel).
600 revolving field • Rieke chart

revolving field See ROTATING FIELD. rhenium Symbol, Re. A metallic element. Atomic
rewind To run a magnetic tape on a transport at a number, 75. Atomic weight, 186.207. It is used in
high speed, in the direction opposite to that asso- some thermocouples.
ciated with the play mode. rheostat A wirewound variable dropping resistor of
rewrite In computer operations, to return informa- the rotary type or slider type.
tion read from a storage location to that location
by recording.
RF Abbreviation of RADIO FREQUENCY.
End Adjustable
RFC Abbreviation of RADIO-FREQUENCY CHOKE. contact
contact contact
RF inverse feedback A negative-feedback system
for radiophone transmitters, in which a portion of
the modulated radio-frequency (RF) signal is rec-
tified, and the resulting direct-current voltage is
filtered and applied as bias to one of the audio
stages in the proper polarity for degeneration.
RF lamp A lighting lamp, used with radio-
frequency (RF) alternating current, rather than
the conventional 60-Hz utility current. This results
in better efficiency, and allows much more light to End contacts
be generated with a given filament lamp, as com-
pared with 60-Hz current. rheostat
RF motion detector In security systems, an intru-
sion detection and alarm system that senses
Doppler-effect-induced changes in the frequency RHF Symbol for high-frequency resistance (see
or phase of a radio-frequency (RF) electromag- RADIO-FREQUENCY RESISTANCE).
netic field. The Doppler effect results from motion RHI Abbreviation of RANGE-HEIGHT INDICATOR.
of objects in the secured area. rhodium Symbol, Rh. A metallic element. Atomic
RFO Abbreviation of radio-frequency oscillator. number, 45. Atomic weight, 102.906.
RF power supply See OSCILLATOR-TYPE POWER rhombus A four-sided geometric plane figure, in
SUPPLY. which all four sides have equal length, and oppo-
RF preamplifier A sensitive, radio-frequency ampli- site angles have equal measure.
fier circuit intended for improving the signal-to- rhombic antenna See DIAMOND ANTENNA.
noise (S/N) ratio in a wireless receiver. Generally rho-theta A radio-navigation system in which a
placed between the receiver and the antenna or single transmitting station is used, and the posi-
feed line. Some such devices are tunable; others tion is determined, according to polar coordinates
are broadbanded. See also PREAMPLIFIER. (distance and direction).
RF probe See RECTIFIER PROBE. rhumbatron A RESONANT CAVITY”especially
RF selectivity See RADIO-FREQUENCY SELEC- Ri Symbol for INPUT RESISTANCE. (Also, Rin.)
FORMER. RIAA curve The amplitude-versus-frequency func-
RF transistor See RADIO-FREQUENCY TRANSIS- tion used in recording and reproduction of long-
TOR. playing (33.3 rpm) phonograph discs, and
Rg Symbol for GRID RESISTANCE. specified by the Recording Industry Association
RG Symbol for GATE RESISTANCE. of America (RIAA). The RIAA curve takes advan-
RGB Abbreviation of RED-GREEN-BLUE. tage of the sensitivity of the human ear at various
RGT Abbreviation of RESONANT-GATE TRANSIS- frequencies to reduce the level of audible noise.
TOR. ribbon microphone See VELOCITY MICROPHONE.
Rh Symbol for RHODIUM. ride gain In broadcasting, the operations of con-
R/h Abbreviation of ROENTGENS PER HOUR. stantly adjusting the audio modulation of the
RH 1. Symbol for HEATER RESISTANCE. 2. Sym- transmitter for optimum operation.
bol for HOT RESISTANCE. Rieke chart A visual aid, similar to the SMITH
rh Abbreviation of RELATIVE HUMIDITY. CHART, used with traveling-wave tubes in the
Rieke chart • ripple

ultra-high-frequency (UHF) and microwave fre- time the telephone rings, so the telephone can be
quency bands for determining the optimum load answered via remote control.
impedance. ring counter An electronic counter in which suc-
rig Colloquialism for a radio communications in- cessive cascaded stages form a ring (i.e., the last
stallation”especially a transmitter or trans- stage in the chain is connected to the first stage
ceiver. It is commonly used among amateur radio so that the counter advances through the cycle,
operators. stage by stage, repetitively).
right-angle line section See ELL. ringdown In a telephone system, the signal sent
right-hand lay See DIRECTION OF LAY. from the transmitting (source) set to the receiving
right-hand polarized wave See CLOCKWISE- (destination) set, causing the destination set to
right-hand rule for induced emf See FLEMING™S ring head In tape recorders, a recording and play-
RIGHT-HAND RULE. back head that consists essentially of a metal ring
right-hand rule for wire A simple rule for indicat- with a gap at one point, and on which the coils
ing the direction of the magnetic field surround- are wound.
ing a straight wire that carries current. When the ring inductor 1. An inductor consisting of a single
wire is grasped in the right hand with the thumb turn of wire, or of a conductor bent into a loop.
pointing in the direction of current flow, the fin- 2. See SHADING COIL.
gers curl in the direction of the magnetic field. ringing Self oscillation in a pulsed inductance-
right-hand taper Potentiometer or rheostat taper capacitance circuit, sustained by the circuit™s fly-
in which most of the resistance is in the clockwise wheel action (hysteresis), and usually producing
half of rotation, as viewed from the front. Com- a damped wave.
pare LEFT-HAND TAPER. ringing coil In the horizontal oscillator in a televi-
right justified In a computer memory location, a sion circuit, a small, adjustable coil (shunted by a
data item that takes up consecutive bit positions, capacitor) used to produce a sharp rise in input-
from right to left. signal voltage.
Right-Leduc effect A phenomenon somewhat ringing current In wire telephony, an alternating
analogous to the Hall effect. When a metal strip current superimposed on the direct operating
conducting heat is placed in a magnetic field per- current. Produces RINGDOWN.
pendicular to the plane of the strip, a tempera- ringing time See RING TIME, 1.
ture difference develops across the strip. ring magnet A permanent magnet in the shape of
right shift In computer operation, a shift whereby a ring or donut.
word bits are displayed to the right; the effect is ring main An electric power main that is closed to
division in a right arithmetic shift. form a ring. This results in two independent elec-
rim drive 1. In a tape recorder, a driving method in trical paths between any two points in the circuit.
which the motor shaft is provided with a smooth If one path is interrupted, power can still be
pulley that transfers motion directly to the rub- transmitted to any other point in the circuit from
ber-tired rim of the flywheel. 2. A driving method a power station.
for a phonograph turntable in which a rotating ring modulator A double-balanced diode-type
wheel contacts the outer edge of the platter. modulator circuit; its name is derived from the
Rin Symbol for INPUT RESISTANCE. (Also, Ri.) ring-like arrangement of the four diodes.
ring 1. The core of a toroidal coil. 2. See HYBRID ring oscillator A self-excited oscillator in which
RING. 3. See RING MODULATOR. 4. See RING two sets of two transistors are operated in push-
INDUCTOR. 5. See RING MAGNET. 6. See RING- pull/parallel.
ING. ring shift In computer operation, the cyclic shift-
ring armature A motor or generator armature hav- ing of digits from one end of a register to the
ing a ring winding. other.
ringback In a telephone system, the signal sent ring time 1. The period of a damped oscillation”
from the receiving (destination) telephone set especially one set up in an inductance-capaci-
back to the sending (source) set, indicating that tance circuit by a pulse. 2. The time required for
the signal is being received. This consists of a an ECHO BOX signal to decay below the display
tone, interrupted by pulses at intervals of about level.
0.05 second. The signal stops when the destina- ring winding A winding in which the turns of the
tion set is taken off the hook. Also see RING- coil are laid on the outside of a ring-shaped core
DOWN. and passed through its center, resulting in a
ring circuit 1. See RING MODULATOR. 2. A donut coil with a core.
waveguide hybrid-tee resembling a ring having ripple 1. A small alternating-current component in
radial branches. 3. In amateur radio operations, the output of a direct-current power supply with
a circuit connected to a telephone line and radio inadequate filtering. 2. In computer and data-
transmitter. The radio transmitter is energized processing operations, the serial transmission of
and modulated with an identifiable signal each data.
602 ripple amplitude • Rochelle salt

rms converter See ROOT-MEAN-SQUARE CON-
rms current See EFFECTIVE CURRENT.
rms meter A current meter or voltmeter whose de-
Core flection is proportional to the root-mean-square
(rms) value of current or voltage. In most meters,
the deflection is proportional to either the peak
value or the average value, but the scale of an
rms unit is graduated on the basis of sine-wave
rms value See EFFECTIVE VALUE.
rms voltage See EFFECTIVE VOLTAGE.
ring winding Rn Symbol for RADON.
Rn 1. Symbol for NEGATIVE RESISTANCE. (Also,
“R.) 2. Symbol for null resistance.
ripple amplitude The peak or peak-to-peak value Ro Symbol for OUTPUT RESISTANCE. (Also, Rout.)
of ripple in a power supply (see RIPPLE, 1). roaming 1. In cellular communications, an ideal
ripple counter A binary counter consisting of flip- condition in which the user of a mobile or
flops cascaded in series. A pulse must pass se- portable wireless telephone set can travel
quentially from the input, through each stage, to throughout a specified geographic region with no
the output of the chain. “dead zones” or interruption in service. 2. For a
ripple current Current flowing in a circuit as the mobile or portable cellular telephone subscriber,
result of ripple voltage (see RIPPLE AMPLITUDE). the act of traveling throughout a large geographic
ripple factor The ratio of the RIPPLE AMPLITUDE region and, in particular, among different states
to the direct-current voltage output of a power or countries.
supply. robot 1. An electromechanical device or system ca-
ripple frequency The frequency of a ripple compo- pable of reliably performing complex and/or
nent (see RIPPLE, 1). In power supplies using repetitive tasks. It can be controlled by a human
half-wave rectification, this frequency is normally operator or by a computer. 2. A usually au-
60 Hz (the line frequency); in full-wave supplies, tonomous device, as defined in 1, built to physi-
it is normally 120 Hz (twice the line frequency). cally resemble a human being, with a head, two
ripple percentage See PERCENT RIPPLE. arms, and some form of locomotion.
ripple torque Symbol, TR. In a torque motor, the robot generations Agreed-on milestones or crite-
small fluctuation in torque resulting from com- ria in the evolution of robots and smart ma-
mutator switching action. chines. First generation: Before 1980. Mainly
ripple voltage See RIPPLE AMPLITUDE. mechanical, stationary, physically rugged, no ex-
RISC Abbreviation of REDUCED INSTRUCTION ternal sensors, no artificial intelligence. Second
SET COMPUTER. generation: 1980“1990. Tactile sensors, vision
rise 1. See VOLTAGE RISE. 2. See RISE TIME. systems, position sensors, pressure sensors, mi-
3. An increase in the amplitude of a pulse or wave. crocomputer control, programmable. Third gener-
rise cable 1. A vertical feeder cable. 2. A vertical ation: After 1990. Mobile, autonomy or group
section of a feeder cable. control, artificial intelligence, speech recogni-
rise time The time required for a pulse to rise from tion/synthesis, teleoperation, navigation sys-
10 percent to 90 percent of its peak amplitude. tems. Fourth generation: In conceptual stages.
Compare FALL TIME. Highly intelligent, capable of building other
RJE Abbreviation of REMOTE JOB ENTRY. robots, capable of doing many human tasks.
Rk Symbol for cathode resistance. robot gripper A robotic END EFFECTOR designed
RL 1. Abbreviation of RESISTANCE-INDUCTANCE. specifically to grasp objects. The two basic de-
2. Abbreviation of RELAY LOGIC. signs are: hand-like and specialized. Hand-like
RL Abbreviation of LOAD RESISTANCE. grippers are engineered according to the notion
RL bridge See RESISTANCE-INDUCTANCE that the human hand has evolved to near perfec-
BRIDGE. tion, and should be mimicked in robots. Special-
RL circuit See RESISTANCE-INDUCTANCE CIR- ized grippers are built by trial-and-error methods
CUIT. and often bear little resemblance to human
RLF Symbol for low-frequency resistance. hands.
RL phase shifter See RESISTANCE-INDUCTANCE robotics The science and art of robot design, con-
PHASE SHIFTER. struction, operation, and maintenance.
Rm Symbol for METER RESISTANCE. Rochelle salt Sodium potassium tartrate, a sub-
rm Symbol for emitter-collector transresistance of a stance whose crystals are piezoelectric. Such crys-
bipolar transistor. tals are used in some microphones, loudspeakers,
rms Abbreviation of ROOT MEAN SQUARE. and transducers. Also called SEIGNETE SALT.
rock • rotary beam

rock Slang for QUARTZ CRYSTAL. the whole assembly to be rotated; a wheel contact
rockbound Pertaining to an oscillator or radio provides a movable tap. Such an indicator is con-
transmitter whose frequency is determined by a tinuously variable and is often used in such de-
quartz crystal, and is, therefore, not variable over vices as antenna-tuning networks.
a significant range. rolling In television, the apparent continuous up-
rocker switch A toggle switch whose lever is a spe- ward or downward movement of the picture,
cially shaped bar. The bar is rocked back and resulting from lack of vertical synchronization
forth to operate the switch. Compare BAT- between the transmitter and receiver.
HANDLE SWITCH, PADDLE SWITCH, and SLIDE rolloff 1. The rate at which a dependent variable
SWITCH. (e.g., output amplitude) diminishes above or be-
low a certain critical value of the independent
variable (e.g., frequency). It pertains especially to
frequency response in audio devices and sys-
on tems. 2. Attenuation of the bass and/or treble re-
sponse or output in an audio system.
ROM Abbreviation of READ-ONLY MEMORY.
Romeo Phonetic alphabet code word for the letter
Romex cable A form of wire cable with a covering
that is highly resistant to the environment.
roof mount A metal bracket for fastening an an-
rocker switch tenna mast to a roof.
room noise Ambient acoustic noise in a room.
rod 1. A unit of length or distance; 1 rod = 5.029 room resonance Acoustic resonance caused by
meters. 2. A bar of material with special proper- the geometry and contents of a room.
ties. room temperature Abbreviation, RT. 1. The tem-
rod antenna See FERRITE-ROD ANTENNA. perature of the chamber in which a test or fabri-
rod magnet A permanent magnet in the shape of a cation is carried out. It is commonly used to
rod with circular or elliptical cross section. distinguish between operations that can be per-
roentgen Abbreviation, r. A unit of ionizing radia- formed at the ambient temperature and those
tion; 1 r is the quantity of radiation that produces that require an oven or a cold chamber. 2. A tem-
1 esu of electricity (positive or negative) per cubic perature typical of an indoor environment, ap-
centimeter of air at standard temperature and proximately 21 degrees Celsius (70 degrees
pressure. In average tissue, 1 r produces ioni- Fahrenheit).
zation equivalent to an energy concentration of room tone A qualitative expression for the suit-
2.58 — 10“4 C/kg (93 ergs per gram). Also see MIL- ability or behavior of an enclosed area for a given
LIROENTGEN. acoustic application. It affected by factors (such
roentgen equivalent man See REM. as resonances or lack thereof, echoes or lack
roentgen equivalent physical See REP. thereof, overall room size and proportions, and
roentgen ray See X RAY. background noise).
roger A communications signal meaning “Ac- root mean square Abbreviation, rms. The square
knowledged.” root of the arithmetic mean (average) of the
Roget spiral A spring-like wire device that con- squares of a set of values.
tracts in proportion to the magnitude of the cur- root-mean-square converter A device that con-
rent flowing through it. verts an input signal of any waveform into a
role indicator In computer operations, a code direct-current signal of the same value as the
classifying a keyword as a part of the speech (e.g., EFFECTIVE VALUE of the input signal.
noun). root-mean-square current See EFFECTIVE CUR-
roll 1. In a display terminal having a line length of RENT.
less than the standard 80 characters, an operat- root-mean-square value See EFFECTIVE VALUE.
ing feature that allows the operator to follow the root-mean-square voltage See EFFECTIVE VOLT-
text along. The cursor remains fixed near the cen- AGE.
ter of the displayed line, while the text moves ROP Abbreviation of record of production.
from right to left. 2. Vertical movement of a tele- rosin A substance derived chemically from an ex-
vision picture, resulting from lack of vertical syn- tract of pine wood, and used in some solders.
chronization. rotameter A fluid flow gauge consisting of a float
rollback In computer operations, the running within a glass tube having incremental markings.
again of a computer program or portion of the rotary amplifier See AMPLIDYNE.
program. Also called RERUN. rotary antenna See ROTATABLE ANTENNA.
roller inductor A variable inductor, usually of the rotary beam A beam antenna, such as a Yagi, that
air-core type, with a shaft attached that allows can be rotated in a (usually horizontal) plane to
604 rotary beam • rounding

allow transmission and/or reception in various Antenna
directions. Also see ROTATABLE ANTENNA.
rotary-beam antenna See ROTARY BEAM.
rotary converter A dynamo (electric machine)
having a direct-current armature connected to a
commutator on one end of the shaft and to slip
rings on the other end. When the machine is op-
erated as a direct-current motor, it delivers an al-
ternating-current output, and vice versa. Also
rotary dialing An older style of telephone dialing in
which a rotary pulse generator is used to dial the
rotary digital audio tape Digital audio tape used
with a recording/playback system that uses a ro-
tating head or heads.
rotary encoder An optical analog-to-digital (A/D)
converter that operates by passing a light beam
through a rotating disk. The amplitude of the
analog input signal at any moment causes a cer-
tain angular rotation of the disk, cutting off the
light beam, according to the nature of the pattern
on the disk. The resulting modulated light beam
has digital characteristics and can be detected
using photocells.
rotary inverter A motor-generator used to change
a direct-current input voltage into an alternating-
current output voltage. rotatable antenna
rotary-motion sensor A transducer that delivers
an output voltage proportional to the arc over
which its shaft has been turned. rotating machines Electromechanical devices
rotary power amplifier See DC GENERATOR AM- (such as motors, generators, amplidynes, rotary
PLIFIER. converters, etc.) that utilize magnetic flux to con-
rotary relay An electromechanical relay in which a vert angular motion or displacement into electri-
pivoted armature rotates to open or close the con- cal energy, or vice-versa.
tacts. The meter relay is an example. rotating memory See DISK MEMORY and DRUM
rotary selector switch See ROTARY SWITCH. MEMORY.
rotary stepping relay See STEPPING SWITCH. rotating voltmeter See GENERATING VOLT-
rotary stepping switch See STEPPING SWITCH. METER.
rotary switch A switch in which a blade moves in rotator A motor-driven, remotely controlled mech-
a circle or in arcs over the contacts. anism for turning a directional antenna in a spe-
rotary transformer A motor-generator used to cific plane.
change an input voltage into a lower or higher rotor 1. A rotatable coil”especially in a motor or
output voltage. generator. Compare STATOR, 1. 2. The rotating
rotatable antenna An antenna that can be turned member of a motor or generator. Compare STA-
to change the orientation of its main lobe (direc- TOR, 2. 3. The rotating-plate assembly of a vari-
tion of greatest forward gain) in a specific plane able capacitor. Compare STATOR, 3.
(usually horizontal). rotor blade The wiper arm of a rheostat or poten-
rotating amplifier See DC GENERATOR AMPLI- tiometer.
FIER. rotor coil See ROTOR, 1.
rotating antenna An antenna that constantly rotor plate The rotating plate(s) of a variable ca-
turns to scan a given area (e.g., a RADAR AN- pacitor. Compare STATOR PLATE.
TENNA). roulette pattern A circular pattern for frequency
rotating-capacitor modulator A frequency modu- identification with an oscilloscope, consisting of
lator consisting of a motor-driven variable capac- loops around the screen™s circumference. Com-
rotating field An alternating-current electric or URE, and SPOT-WHEEL PATTERN.
magnetic field, such as that generated by the sta- rounding 1. A method of approximating a quantity
tors of some motors, that revolves between poles. by reducing the number of significant digits. For
rotating interrupter A commutator (see COMMU- example, rounding 3.44 to two significant digits
TATOR, 1). yields 3.4; rounding 3.46 to two significant digits
rounding • rumble

yields 3.5. Compare TRUNCATION. 2. The ap- Rs 1. Symbol for SERIES RESISTANCE. (Also, Rser.)
proximation of a value to a specified number of 2. Symbol for SECONDARY RESISTANCE. (Also,
decimal places or significant digits. 3. Smoothing Rsec.)
of the corners of a square wave or sawtooth wave, Rsec Symbol for SECONDARY RESISTANCE. (Also,
resulting in lengthening of the transition time Rs.)
from one state to another. Rser Symbol for SERIES RESISTANCE. (Also, Rs.)
rounding error The error resulting from the RST flip-flop A conventional flip-flop subject to the
rounding of a number (see ROUNDING, 1, 2). operations of reset, set, and trigger.
round off To shorten an otherwise lengthy number RST system In the amateur radio service, a
by replacing numerical digits with zeros and in- method of reporting signal quality in terms of
creasing the final nonreplaced digit by 1 if the readability, strength, and tone.
leftmost replaced digit is 5 or greater. Thus, R sweep In an oscilloscope or spectrum analyzer,
3.141592653 can be rounded off to 3.1416 or an expanded portion of the trace produced by a
3.14. long triggered sweep. It permits detailed analysis
round-up A form of numerical approximation, in of a small portion of a displayed waveform or fre-
which a number with a value of n.5 or greater is quency band.
assigned the value n + 1. This is a feature of many RT 1. Abbreviation of RADIOTELEPHONE. 2. Ab-
calculators using scientific notation or a fixed breviation of ROOM TEMPERATURE.
number of decimal places. rt Abbreviation of RIGHT.
Rout Symbol for OUTPUT RESISTANCE. (Also, Ro.) RT 1. Symbol for THERMAL RESISTANCE. 2. Sym-
route 1. To physically position wires or conducting bol for total resistance. (Also, Rt.)
circuit paths by planning and deliberation. 2. The Rt Symbol for total resistance.
path over which conductors are positioned. 3. A RTD Abbreviation of RESISTANCE TEMPERA-
path over which signals or information can be TURE DETECTOR.
carried. RTL Abbreviation of RESISTOR-TRANSISTOR
routine 1. In computer operations, the complete LOGIC.
sequence of instructions for performing an opera- RTTY Abbreviation of RADIOTELETYPE.
tion (i.e., a program or program segment). 2. A RTZ Abbreviation of RETURN TO ZERO. (Also, RZ.)
test or measurement procedure. 3. An assembly Ru Symbol for RUTHENIUM.
or manufacturing procedure. 4. A standard trou- rubber A natural insulating material; an elastomer
bleshooting procedure. exhibiting rapid elastic recovery. Dielectric con-
row In a matrix, a horizontal arrangement or set of stant, 2 to 3.5. Dielectric strength, 16 to 50
values. kV/mm. Also called India rubber. Compare HARD
RP 1. Symbol for PLATE RESISTANCE. (Also, rP.) RUBBER.
2. Symbol for POSITIVE RESISTANCE. 3. Symbol rubber-covered wire Wire insulated with a jacket
for PARALLEL RESISTANCE. (Also, Rpar.) 4. Sym- of rubber.
bol for PRIMARY RESISTANCE. (Also, Rpri.) rubidium Symbol, Rb. A metallic element. Atomic
Rpar Symbol for PARALLEL RESISTANCE. (Also, number, 37. Atomic weight, 85.468.
RP.) ruby laser A laser using a ruby rod as the resonant
r parameters 1. Device or network parameters ex- element.
pressed as resistances. 2. Transistor parameters
in terms of resistance values in the equivalent tee
network. Compare G PARAMETERS and H PA- Ruby crystal
rpm Abbreviation of revolutions per minute.
RPN Abbreviation of REVERSE POLISH NOTA- 95-percent
100-percent Helical
TION. reflector
reflector flash tube
Rpri Symbol for PRIMARY RESISTANCE. (Also,
RP.) ruby laser
rps Abbreviation of revolutions per second.
RPT Radiotelegraphic abbreviation of repeat.
ruby maser A maser in which the resonant mate-
rial is ruby.
Ruhmkorff coil See INDUCTION COIL.
rumble 1. Low-frequency acoustical noise of a fre-
quency below about 50 Hz. 2. Low-frequency
RS Symbol for SOURCE RESISTANCE in a field-
electrical noise in an audio circuit of a frequency
effect transistor.
606 rumble • R-Y signal

below about 50 Hz. 3. Vibrations that can occur terial subjected to excessive voltage. 2. The clean
in a poorly designed or malfunctioning phono- opening of relay, circuit-breaker, or switch con-
graph turntable. tacts to interrupt a current-carrying circuit.
rumble filter An audio high-pass filter having rush Broadband audio background noise, such as
sharp cutoff below 50 Hz, for eliminating rumble that arising from superheterodyne receivers and
arising from irregularities in the rotation of a high-gain amplifiers. Its name is derived from re-
phonograph turntable. Also see RUMBLE, 3. semblance to the gentle rushing of wind. Com-
run 1. The execution of a computer routine or pro- pare HISS, 1, 2.
gram. 2. To execute a routine or program. 3. To ruthenium Symbol, Ru. A rare metallic element.
cause a routine or program to be executed. 4. A Atomic number, 44. Atomic weight, 101.07.
command that causes a routine or program to be rutherford Abbreviation, rd. A unit of radioactivity
equal to 106 disintegrations per second (2.7 — 10“5
runaway In a current-carrying circuit or device, es- curie). Also see KILORUTHERFORD, MEGA-
pecially a semiconductor, a rapid increase in cur- RUTHERFORD, MICRORUTHERFORD, and
rent that causes the temperature to rise, in turn MILLIRUTHERFORD.
resulting in a further increase in current. Unless Rutherford atom An early concept of the nature of
preventive measures are taken, this will ulti- the atom, proposed by Rutherford in 1912. In this
mately damage or destroy the component. model, negatively charged electrons orbit a cen-

run chart In computer operations, a flowchart tral, positively charged nucleus in a manner sim-
showing the organization and order of pertinent ilar to the way planets orbit the sun. Compare

programs to be run. BOHR ATOM.
running accumulator A computer storage unit rutherfordium Symbol, Rf. Also called unnilquadium
having registers linked so that data is transferred (Unq) and kurchatovium (Ku). Atomic number, 104.
unidirectionally from one to the other, and in The most common isotope has atomic weight 261.
which only one register is accessible from the out- Classified as a transition metal. It has a half-life on
side. the order of a few seconds to a few tenths of a sec-
running open 1. The condition of a mechanical ond (depending on the isotope), is human-made,
teleprinter running continuously in the absence and is not known to occur in nature.
of a signal. The teleprinter operates, but nothing RW Abbreviation of radiological warfare.

is printed; this keeps the machine in synchro- Rx Symbol for unknown resistance.
nization. 2. Operation of a transmitter at the RY Abbreviation of RELAY.
maximum rated level of input or output power. ryotron A form of inductive semiconductor switch,
running-time meter See ELAPSED-TIME METER. operated at cold temperatures to maximize con-
run time 1. The period of time during which a ductivity.
computer program is executed. 2. The length of R-Y signal In a color-television circuit, the signal
time required for a computer program to be exe- representing primary red (R) minus luminance
cuted. (Y). A primary red signal is obtained when the
rupture 1. The usually rapid and violent tearing R-Y signal is combined with the luminance (Y)
apart, or breaking through, of an insulating ma- signal. Compare B-Y SIGNAL and G-Y SIGNAL.

S 1. Symbol for SCREEN GRID of a vacuum tube.
2. Symbol for SHELL of a tube or semiconductor Unit Unit Unit
device. 3. Symbol for SULFUR. 4. Symbol for DE- X Y Z
6. Symbol for ELASTANCE. 7. Abbreviation of
SYNC. 8. Symbol for SECONDARY. 9. Abbrevia-
tion for SIEMENS. 10. Abbreviation of SINE. 11.
Symbol for ENTROPY.
s 1. Symbol for distance or DISPLACEMENT.
2. Symbol for SCREEN GRID of a vacuum tube.
3. Symbol for STANDARD DEVIATION. 4. Abbre- safety ground
viation for SECOND.
SA band A section of the S band, extending from sal ammoniac Formula, NH4Cl. Ammonium chlo-
3100 to 3400 MHz. ride, the principal ingredient in the gelatinous
sabin A unit of sound absorption; 1 sabin repre- electrolyte of some dry cells and batteries.
sents a surface that can absorb sound at the salient pole A pole, such as the polepiece of a mo-
same rate as 1 square foot of a perfectly ab- tor or generator, that projects from the rest of the
sorbent surface. structure (rotor assembly or motor frame).
SADT Abbreviation of surface alloy diffused-base Salisbury chamber A radio-frequency test cham-
transistor. ber in which the walls are non-reflective at vari-
SAE 1. Abbreviation of SHAFT-ANGLE ENCODER. ous frequencies, thus simulating free space.
2. Abbreviation of Society of Automotive Engineers. salt-spray test A test to assess the life and perfor-
safe noise level A level of acoustic intensity equal mance of electronic equipment in a marine envi-
to 85 dB above the threshold of hearing. At sound ronment. The equipment is sprayed, usually with
levels higher than this, eardrum damage is possi- a saltwater mist, and various electrical parame-
ble. ters are measured at prescribed time intervals.
safety factor A figure denoting the extent of over- samarium Symbol, Sm. A metallic element of the
load that a device can withstand before breaking rare-earth group. Atomic number, 62. Atomic
down. weight, 150.36.
safety ground A connection made between equip- sample 1. A selection of quantities, events, or ob-
ment (usually the metal chassis, panel, case, or jects, taken at a specific time or time interval for
B-minus circuit) and the earth as a protective analysis or testing. 2. To take a sample, as de-
measure against fire and electric shock. fined in 1. 3. To test a quantity (current, voltage,
safety switch See ELECTRICAL INTERLOCK. temperature, pressure, etc.) or a material

Copyright © 2001 by The McGraw-Hill Companies, Inc.
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608 sample • saturation

(electrolyte, insulant, corrosion, rust, etc.) taken
from a larger group or body.
sample and hold A method of storing a variable
signal for detailed examination.
sampled data system A system that can be either
analog or digital, and that works from samples of
the input signals.
sampler In audio systems, a device that digitizes
and stores sound for a brief interval of time.
sample size In statistics, the number of items in
the sample space chosen for analysis.
sample space In statistics, the set of events, num-
bers, or other items chosen for analysis.
sampling 1. Observation of a signal at various
points in a circuit, without affecting the operation
of the circuit. 2. The conversion of analog signals
to binary signals”especially for use in digital
communications systems and in computers. 3. In
statistics and probability, a set of function values
corresponding to specifically chosen points in the
domain. saturable-core magnetometer A MAGNETOME-
sampling rate The frequency with which samples TER in which the sensor is a saturable magnetic
are taken [e.g., 1/hr (one sample per hour) or core with a winding. The readout is proportional
10/min (10 samples per minute)]. to the change in permeability of the core pro-
sampling window See WINDOW, 2. duced by the magnetic field under test.
sand load A microwave power dissipator in which saturable reactor An inductor consisting essen-
the absorptive material is a mixture of sand and tially of a coil wound on a core of magnetic
carbon. material whose magnetic flux can easily reach
sapphire needle See SAPPHIRE STYLUS. saturation level. The inductance and, accordingly,
sapphire stylus A jewel-tipped stylus for disc the reactance of the device can be varied by pass-
recording and playback. It is noted for durability. ing a direct current through the coil simultane-
sat 1. Abbreviation of saturate. 2. Abbreviation of ously with the alternating current to be controlled.
SATURATION. 3. Abbreviation of SATELLITE. saturable transformer A transformer having a sat-
satd Abbreviation of saturated. urable core that permits automatic regulation of
satellite An artificial object sent into orbit around an alternating-current voltage.
the earth or another planet. See, for example, AC- saturated color A visible color whose energy is
TIVE COMMUNICATIONS SATELLITE and PAS- concentrated at a single wavelength or in a nar-
SIVE COMMUNICATIONS SATELLITE. row band of wavelengths. Also called pure color.
satellite communication Communication via one saturated logic Any form of digital-logic circuit in
or more satellite transponders. Usually both sta- which the transistors are either completely cut off
tions are on the ground, although sometimes one or completely saturated. It is characterized by rel-
or both stations are airborne or in space. ative immunity to noise, high speed, and high
satellite processor 1. In a computer, a micropro- input-level requirements.
cessor that is subsidiary to the central processing saturated operation 1. The operation of a mag-
unit (CPU). 2. In a data-processing system, a CPU netic core at or beyond its saturation point (i.e.,
used to handle the running of programs of sec- in the region where an increase in coil current
ondary importance to the system™s main applica- produces no change in core magnetization).
tion. 2. The operation of a transistor or vacuum tube
satellite television The broadcasting and reception beyond its saturation point (i.e., in the region
of television (TV) signals via earth-orbiting satel- where an increase in voltage produces no change
lite. Usually, the satellite is in a geostationary or- in current, or vice versa). Compare UNSATURATED
bit. The receiving station employs a dish antenna, OPERATION.
a tuner, a digital-to-analog (D/A) converter (if the saturated solution A solution, such as an elec-
signals are digital), and a TV receiver. trolyte, that contains all of the solute that it ordi-
satisfy To make a statement of inequality or an narily will hold at a given temperature and
equation true (e.g., x = 2 satisfies the equation pressure. Compare SUPERSATURATED SOLU-
2x = x 2). TION. Also see SOLUTE; SOLUTION, 1 and SOL-
saturable capacitor A voltage-variable ceramic or VENT, 2.
semiconductor capacitor in which variations in saturating current See SATURATION CURRENT.
capacitance stabilize at a reasonably constant saturation 1. See SATURATION POINT. 2. The
value after a particular voltage level is reached. state of purity of a color. In general, the greater
saturation • scale down

the saturation, the narrower the bandwidth of the age of a switching transistor in its switched-on
electromagnetic energy. The highest possible sat- state).
uration is represented by energy at a single wave- SAVOR Abbreviation of SIGNAL-ACTUATED
length [e.g., light of 700 nanometers (nm) appears VOICE RECORDER.
as highly saturated red, and light of 400 nm ap- sawtooth An alternating or pulsating wave of cur-
pears as highly saturated violet]. Compare HUE. rent or voltage that is characterized by a gradual
3. The condition of a ferromagnetic material in rise in amplitude followed by a rapid fall, or vice
which it can accommodate no additional mag- versa; its name is derived from its graphic resem-
netic flux. 4. The condition of a dielectric material blance to the teeth of a saw.
in which it can accommodate no additional elec-
tric flux.
saturation current In a device, the current flowing

at and beyond the SATURATION POINT.
saturation flux 1. The magnetic flux density that
will saturate a given sample of magnetic material. Time
2. The electric flux density that will saturate a
given sample of dielectric material.
saturation flux density See SATURATION INDUC-
TION. sawtooth
saturation induction For a magnetic material, the
maximum possible flux density.
saturation limiting Output peak clipping that oc- SB 1. Abbreviation of SIDEBAND. 2. Abbreviation
curs when a transistor or vacuum tube is driven of SIMULTANEOUS BROADCAST.
into saturation during part of the input cycle. Sb Symbol for ANTIMONY.
Compare CUTOFF LIMITING. S band A radio-frequency band extending from
saturation point On a voltage-current conduction 1550 to 5200 MHz. For subdivisions of this band,
curve, the point beyond which a further increase see SA BAND, SC BAND, SD BAND, SF BAND, SG
in voltage produces no appreciable increase in BAND, SH BAND, SQ BAND, SS BAND, ST BAND,
current. SW BAND, SY BAND, and SZ BAND.
Collector/drain current

SC 1. Abbreviation of SUPPRESSED CARRIER.
2. Abbreviation of SHORT CIRCUIT. 3. On draw-
ings, the abbreviation for silk-covered.
Sc Symbol for SCANDIUM.
sc 1. Abbreviation of SINGLE CRYSTAL. 2. Abbre-
viation of SCALE. 3. Abbreviation of sine-cosine.
4. Abbreviation of science.
Base/gate voltage
SCA adapter An auxiliary tuner unit for separat-
saturation point
ing the SCA subcarrier from a main frequency-
modulated signal on which it is superimposed.
saturation resistance The voltage-to-current ratio Also see SCA SUBCARRIER and SUBSIDIARY
for a saturated semiconductor. COMMUNICATIONS AUTHORIZATION.
saturation switching The on/off switching opera- scalar quantity A quantity having magnitude, but
tion in which a transistor is in its saturated state for which direction is not specified. Compare
when conducting. VECTOR QUANTITY.
saturation value 1. In a transistor, field-effect scale 1. A graduated line or curve for indicating
transistor, or vacuum tube, the lowest level of the values of a quantity. 2. An ordered set of values.
input current, voltage, or power that results in 3. An ordered series of quantities, such as tones,
saturation. 2. The maximum obtainable output frequencies, voltages, etc. (e.g., musical scale).
level for a given circuit. 3. In a magnetic material, scale division The space between consecutive
the smallest level of magnetizing force that re- graduations on a scale (see SCALE, 1).
sults in the maximum possible flux density. scale down In computer operations, to adjust a
saturation voltage The (usually direct-current group of quantities according to a fixed factor so
output) voltage appearing across a device operat- that it can be accommodated by hardware or
ing in its saturation region (e.g., the collector volt- software.
610 scale expansion • scanning yoke

scale expansion Spreading out the divisions in element, as in facsimile or television. 5. A single
part of a scale (see SCALE, 1). line resulting from 4. 6. In information retrieval
scale factor 1. A figure by which the readings from operations, to inspect each record in a file or con-
a particular scale must be multiplied or divided to stituent of a list. 7. To check communications or
give the true values of measured quantities. 2. A data channels for availability.
figure via which values in one system of notation scan conversion In television reception, the scan-
are converted to those in another system. 3. In ning of each line twice to convert a conventional
scaling down (see SCALE DOWN), the factor by image into one that can be displayed on a high-
which a group of quantities is adjusted. 4. The definition picture tube.
ratio of output frequency to input voltage for a scan-converter tube A face-to-face assembly of a
voltage-to-frequency converter. cathode-ray tube and a vidicon in one envelope.
scale-factor adjustment In some meters, an ad- scandium Symbol, Sc. A metallic element. Atomic
justment that allows full-scale deflection to be set number, 21. Atomic weight, 44.956.
at any desired value (within certain limits) of ap- scan frequency See SCANNING FREQUENCY.
plied-signal amplitude. scanner A device, especially a radio receiver,
scale-factor error The absolute value of the differ- equipped with a circuit that searches communi-
ence between the actual scale factor and the ideal cations or data channels for signals.
scale factor for a multiplier circuit. scanner amplifier An amplifier for boosting a
scale-factor tolerance The extent to which a mea- scanning signal. Also see SCAN, 1, 3, 4.
sured value for the scale factor differs from the scanning 1. In a cathode-ray tube or camera tube,
computed value. It is generally given as a per- the synchronized movement of the electron beam
centage. (or other marker) from right to left and/or from
scale length The end-to-end dimension of a scale top to bottom. 2. The intermittent, but repetitive,
(see SCALE, 1), in inches, centimeters, geometric monitoring of two or more communications chan-
degrees, or number of divisions. nels in rotating sequence. 3. The movement of a
scale multiplier See SCALE FACTOR, 1. radar beam for the purpose of obtaining coverage
scale-of-two counter A circuit that delivers one over a specified area.
output pulse for two successive input pulses. scanning antenna A transmitting or receiving an-
scale-of-10 counter A circuit that delivers one tenna (such as a rotating one) that covers a gen-
output pulse for 10 successive input pulses. erally circular region.
scale-of-ten scaler See SCALE-OF-10 COUNTER. scanning beam The deflected electron beam in a
scaler A circuit or device for extending the fre- cathode-ray tube. Also see SCAN, 1, 2, 3, 4, 5.
quency range of another device (e.g., a circuit that scanning circuit A circuit for producing a scan
extends the range of a 1-MHz counter to 100 (see SCAN, 2, 4).
MHz). scanning frequency The number of scans per unit
scale range The difference between the lowest and time, usually expressed in lines, sweeps, or chan-
highest values on a scale. nels per second or per minute. Also called SCAN-
scale span See SCALE RANGE. NING RATE.
scaling The fact, and the implications of the fact, scanning line A single line sampled or produced
that the mechanical strength of a structure in- by a scanning process, as in facsimile, television,
creases in proportion to the square of linear di- and graphic recording.
mension while the weight increases, according to scanning line frequency See SCANNING FRE-
the cube of linear dimension. Thus, weight in- QUENCY.
creases more rapidly than strength as a struc- scanning linearity Uniformity of scanning rate. In
ture, composed of a given material, is made a linear scan, for example, scan speed is the same
larger. It is important in the design of large an- at all points along a line.
tennas and support structures. scanning loss The effective reduction in radar sen-
scaling adder An inverting OPERATIONAL AMPLI- sitivity that occurs as the beam scans a given
FIER used to weight and sum multiple voltages. area, rather than remaining in a fixed orientation.
scaling circuit A circuit, such as one or more flip- scanning rate See SCANNING FREQUENCY.
flops, that will deliver one output pulse after a scanning receiver A receiver whose tuning is au-
predetermined number of input pulses have been tomatically and continuously swept through a
received; therefore, it will provide pulse or fre- frequency band to detect all signals in the band.
quency division. See, for example, SCALE-OF- scanning sonar A form of distance-measuring or
TWO COUNTER. depth-finding sonar, in which the receiving trans-
scaling factor For a scaler, the number of input ducer scans to find the direction of the echo or
pulses required for one output pulse. echoes.
scaling ratio See SCALING FACTOR. scanning speed The rate at which a line, region, or
scan 1. To traverse a range, field, or dimension. quantity is scanned or at which samples are
2. The amount of traversal in 1. 3. See SWEEP. taken.
4. To sample or reproduce an image in a single-line scanning yoke See YOKE, 2.
scan rate • scientific notation

scan rate 1. The rate at which a controlled quan- schematic diagram An electronic circuit diagram.
tity is checked periodically by a control computer. Also called WIRING DIAGRAM and schematic.
2. See SCANNING FREQUENCY. schematic symbol A graphic symbol used to rep-
scan tuning Repetitive, automatic sweeping of a resent electronic components in a circuit dia-
frequency band by a tuned circuit containing a gram.
varactor, whose capacitance is periodically varied Schering bridge A four-arm capacitance bridge in
by a sawtooth voltage. which the unknown capacitance is compared
SCARA Abbreviation of SELECTIVE COMPLIANCE with a standard capacitance. This bridge is fre-
ASSEMBLY ROBOT ARM. quently used in testing electrolytic capacitors, to
SCA subcarrier An auxiliary carrier (commonly which a direct-current polarizing voltage is ap-
67 kHz) superimposed on a main frequency- plied during the measurement.
modulated carrier to convey subsidiary communica-
tions, such as music without commercials. Also see
CX = CS (R2/R1)
RX = R1 (C1/CS)
RX balance
scatter To disperse or diffuse transmitted electro-
magnetic radiation.
scattering 1. The tendency of a concentrated beam
of energy to be spread out when it passes through
a given medium or substance. 2. The spreading
out of radio waves as they pass through the iono- C1
sphere or troposphere.

Transmitting Receiving Schering bridge
station station
Schmidt optical system In projection television, a
lens system used between the bright-image pic-
ture tube and the screen.
scattering Schmitt limiter See SCHMITT TRIGGER.
Schmitt trigger A multivibrator that produces
scatter read In data processing, to distribute data uniform-amplitude output pulses from a vari-
from an input record to several storage areas. able-amplitude input signal. This circuit has
scatter transmission See BACK SCATTER and many applications, one being the conversion of a
FORWARD SCATTER. sine wave into a square wave.
SC band A section of the S BAND extending from Schottky diode A solid-state diode in which a
2000 to 2400 MHz. metal and a semiconductor form the pn junction.
scc Abbreviation of SINGLE-COTTON-COVERED Electrons injected into the metal have a higher
(WIRE). energy level than the charge carriers in a semi-
SCDSB Abbreviation of SUPPRESSED CARRIER conductor, and energy storage at the junction is
DOUBLE-SIDEBAND (see DOUBLE-SIDEBAND low because current flow is not accompanied by
SUPPRESSED CARRIER). hole movement. Also known as HOT-CARRIER
SCE Abbreviation of saturated calomel electrode. DIODE.
sce Abbreviation of SINGLE-COTTON-ENAMELED Schottky logic A form of integrated-injection logic
(WIRE). with enhanced operating speed.
SCEPTRON Acronym for SPECTRAL COMPARA- Schottky noise The random noise resulting from
TIVE PATTERN RECOGNIZER. the emission of charged particles, usually elec-
schedule In computer operations, to establish the trons or holes, from an electrode in an amplifying
order of importance of jobs to be run, and assign device. This noise is usually of a wideband na-
the necessary resources for those jobs. ture.
schedule method A method of waveform analysis scientific language Any computer programming
involving the evaluation of instantaneous ampli- language used primarily for mathematical or sci-
tudes at numerous points in time. The values are entific applications.
obtained at specific intervals from the image of scientific notation The expression of very large
one complete wave cycle, as displayed on an os- and very small numbers as a fixed-point part
cilloscope or plotted on a graph. (mantissa) and a power of the radix (usually 10).
612 scientific notation • seaborgium

Generally, the mantissa is greater than or scratchpad memory In computers, a low-capacity
equal to 1, but less than 10; the power of 10 is ad- memory that stores an intermediate result of a
justed accordingly. Thus, for example, 203,700 = calculation.
2.037 — 105; 0.000533 = 5.33 — 10“4. See also scratch tape Magnetic data tape that can be over-
SIGNIFICANT FIGURES. written for any purpose.
scintillating crystal A crystal, such as one of screen 1. See SCREEN GRID. 2. See SHIELD.
sodium iodide, that sparkles or flashes when ex- 3. The front surface of a cathode-ray tube. 4. The
posed to radioactive particles or rays. surface of a computer or terminal display.
scintillation 1. In radar operations, the apparent screen angle In radar, the angular difference be-
rapid displacement of a target from its mean po- tween the actual horizon and the plane perpen-
sition. 2. A momentary flash of light produced in dicular to the line connecting the radar set with
a phosphor or scintillating crystal when a high- the center of the earth.
velocity particle strikes it. 3. A small fluctuation screen current Symbol, IS or ISG. The current flow-
in radio field intensity at a receiving point. ing in the screen circuit of an electron tube.
scintillation counter A radiation counter consist- screen grid In a vacuum tube, a grid element be-
ing essentially of a scintillating crystal in combi- tween the control grid and plate. It reduces the
nation with a photomultiplier tube. Flashes from internal grid-plate capacitance, and consequently
the excited crystal cause the tube to deliver out- prevents self-oscillation when the tube is used in
put pulses that are totaled and indicated. a straight-through amplifier.
scintillator material A substance, such as crys- screen-grid neutralization Neutralization of an
talline sodium iodide, that scintillates under cer- amplifier that uses a tetrode vacuum tube. Such
tain stimuli. circuits require smaller neutralizing capacitances
scissoring A method of interrupting the electron than those used in triode amplifiers because
beam in a cathode-ray tube when the beam of the lower interelectrode capacitance of the
would not land on the phosphor screen. screen-grid tube.
SCLC Abbreviation of SPACE-CHARGE-LIMITED screen illumination Edge lighting of the transpar-
CURRENT. ent screen of an oscilloscope, to make the lines of
sco Abbreviation of SUBCARRIER OSCILLATOR. the graticule more clearly visible.
scope Colloquialism for OSCILLOSCOPE. screen material See PHOSPHOR.
Scott oscillator See PARALLEL-TEE OSCILLA- screen resistance Symbol, RS or RSG. The internal
TOR. resistance presented by the screen-grid/cathode
scp Abbreviation of SPHERICAL CANDLEPOWER. path of an electron tube.
SCR Abbreviation of SILICON-CONTROLLED REC- screen room See CAGE.
TIFIER. screen voltage Symbol, ES or ESG. The voltage at
scrambled signal Any signal in which (for secrecy the screen grid of an electron tube.
or exclusivity) the elements are disarranged ac- scribing The etching of a semiconductor wafer to
cording to an encryption algorithm. Thus, intelli- facilitate breaking the wafer into smaller pieces.
gent reception is possible only if the signal is ScriptX A high-level programming language used
processed via a suitable decryption algorithm. in the writing of software for personal comput-
Example: SCRAMBLED SPEECH. ers”especially in multimedia. Developed by
scrambled speech Voice transmission in which Kaleida Laboratories.
the frequencies have been inverted to prevent SCS Abbreviation of SILICON-CONTROLLED
eavesdropping. It is automatically unscrambled SWITCH.
(by reinversion) at the receiver to restore intelligi- SCT Abbreviation of SURFACE-CHARGE TRAN-
bility. SISTOR.
scrambler circuit A circuit containing filters and S curve 1. The voltage-versus-current curve for a
frequency inverters for scrambling speech. negative-resistance device. Compare N CURVE.
scratch filter An audio-frequency low-pass filter 2. The response curve for a frequency-modula-
that suppresses high-frequency noise caused by tion discriminator or ratio detector.
friction between a phonograph disc and the needle. SD Abbreviation of STANDARD DEVIATION.
SD band A section of the S BAND extending from
4200 to 5200 MHz.
SDF Abbreviation of static direction finder.
Se Symbol for SELENIUM.
Input Output
seaborgium Symbol, Sg. Also called unnilhexium
(Unh). Atomic number, 106. The most common
isotope has atomic weight 263. Classified as a
transition metal. It has a half-life on the order of
1 second or less, is human-made, and is not
scratch filter known to occur in nature.
sea clutter • secondary frequency standard

sea clutter Collectively, the radar echoes that the secondary battery See STORAGE BATTERY.
sea reflects. secondary calibration The calibration of an in-
seal 1. The point at which a lead or electrode en- strument, based on a reference instrument cali-
ters or leaves and is secured to an envelope, case, brated against an absolute source.
or housing. Such a point is often tightly closed secondary capacitance 1. The distributed capaci-
against the passage of air in or out of the enve- tance of the secondary winding of a transformer
lope. 2. To close off a circuit or component from whose primary winding is unloaded. Compare
tampering. PRIMARY CAPACITANCE, 1. 2. A series or shunt
sealed dry battery A set of electrochemical dry capacitance used to tune the secondary coil of a
cells that can be installed without concern for ori- radio-frequency transformer. Compare PRIMARY
entation or position. Example: 9-volt “transistor CAPACITANCE, 2.
sealed meter 1. A meter that is tightly closed
against the entry of moisture and foreign materi-
als. 2. A meter that is locked or otherwise pro-
tected against tampering. To next
IF amp.
sealing compound A substance (such as wax, IF amp.
pitch, or plastic) used to enclose and protect elec-
tronic devices.
search 1. To scan or sweep through a range of
quantities or through a region of interest. 2. To
examine (usually in some prescribed order) items
of information in a computer memory to find
secondary capacitance, 2
those satisfying a given criterion.
search coil An inductive probe (exploring coil)
used to sample magnetic fields.
search oscillator A variable-frequency oscillator secondary cell See STORAGE CELL.
used to locate and identify signals by the hetero- secondary circuit 1. The circuit associated with
dyne method. the secondary winding of a transformer. 2. See
search probe 1. See SEARCH COIL. 2. A capacitive OUTPUT CIRCUIT.
probe used to sample electric fields. secondary coil See SECONDARY WINDING.
search radar A radar that displays a target almost secondary color 1. A color prepared by mixing two
immediately after that target enters a scanned primary colors. 2. In television operations, any
area. displayed color composed of two or more color
search time The time needed to test items during primaries.
a search (see SEARCH, 2). secondary current The current flowing in the sec-
sea return See SEA CLUTTER. ondary winding of a transformer. Also called
seasonal effects In ionospheric propagation, the TRANSFORMER OUTPUT CURRENT. Compare
changes produced as a result of the revolution of PRIMARY CURRENT.
the earth around the sun. The path of the sun secondary electron 1. The electron possessing the
across the sky, and the length of the day, are pri- lesser energy after a collision between two elec-
marily responsible for such effects. trons. Compare PRIMARY ELECTRON. 2. An
seasonal static Atmospheric electrical interfer- electron ejected by secondary emission.
ence, most prevalent during the summer. secondary emission The action whereby electrons
SE band A section of the S BAND extending from in the atoms at the surface of a target are ejected
1550 to 1650 MHz. as a result of bombardment by a beam of (pri-
sec 1. Abbreviation of SECOND. 2. Abbreviation of mary) electrons. Thus, in an electron tube, elec-
SECTION. (Also, sect.) 3. Abbreviation of SEC- trons from the cathode strike the plate with a
ONDARY. 4. Abbreviation of SECANT. force that drives secondary electrons out of the
secant Abbreviation, sec. The trigonometric func- plate, into the surrounding space.
tion representing the ratio of the hypotenuse of a secondary emitter A source of secondary elec-
right triangle to the adjacent side (c/b). The secant trons (e.g., the plate of an electron tube or a dyn-
is the reciprocal of the cosine; sec x = 1/cos x. ode in a photomultiplier tube).
second 1. Abbreviation, s and sec. A unit of time. secondary failure The failure of a component or
The mean solar second is 1/86,400 of a mean so- circuit, resulting from the failure of some other
lar day, and is 1/60 minute or 1/3600 hour. component. For example, the pass transistor in a
2. Symbol ("). A unit of arc measure. 1" = 1/3600 power supply might burn out, causing the output
geometric degree. voltage to increase; this increased voltage can
secondaries See SECONDARY COLORS. damage equipment connected to the supply.
secondary 1. See SECONDARY WINDING. 2. See secondary frequency standard A device for gener-
SECONDARY STANDARD. ating signals of accurate frequency, but that does
614 secondary frequency standard • secular equilibrium

not possess the very high stability and extreme second-channel attenuation See SELECTANCE, 2.
accuracy of a primary frequency standard. The second-channel interference In a given channel,
secondary standard is periodically checked interference arising from authorized signals two
against a PRIMARY FREQUENCY STANDARD channels removed.
and appropriately corrected. second detector In a superheterodyne receiver,
secondary impedance 1. The impedance of the the intermediate-frequency detector. Compare
secondary winding of a transformer whose pri- FIRST DETECTOR.
mary winding is unloaded. Compare PRIMARY second-level address In a computer program in-
IMPEDANCE, 1. 2. An external impedance pre- struction, an address giving the location of the
sented to the secondary winding of a transformer. address of a required operand. Also called indirect
Compare PRIMARY IMPEDANCE, 2. address.
secondary inductance The inductance of the sec- sect Abbreviation of SECTION. (Also, sec.)
ondary winding of a transformer whose primary section 1. A subcircuit or stage of a larger circuit
winding is unloaded. Compare PRIMARY INDUC- (e.g., the oscillator section of a receiver). 2. The


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