. 36
( 42)


staircase circuit See STAIR-STEP CIRCUIT. to supply a precise direct-current voltage for
staircase generator A circuit or device for generat- electronic measurements. The Weston standard
ing a STAIR-STEP WAVE. cell contains a mercury positive electrode, cad-
staircase wave See STAIR-STEP WAVE. mium amalgam negative electrode, and cad-
stair-step circuit A circuit that converts a series of mium sulfate electrolyte, and delivers 1.0183
equal-amplitude pulses into a stair-step wave. volts at 20 degrees Celsius. Also see ZINC
stair-step wave A nonsinusoidal wave character- STANDARD CELL.
ized by a multistep rise and a steep fall. It is so
called from its resemblance to the cross section of
a staircase.

stair-step wave

stall torque The torque produced when a motor
shaft is prevented from turning.
stalo Acronym for stabilized oscillator.
stand-alone photovoltaic system A solar-power
plant that uses large banks of rechargeable elec-
trochemical batteries, such as the lead“acid type,
to store electric energy as it is supplied by photo-
voltaics during hours of bright sunshine. The en-
ergy is released by the batteries at night or in standard deviation In statistical analysis, the
gloomy daytime weather. This system does not square root of the mean of squares of deviation
depend on the electric utility companies. Al- from the mean.
though this scheme offers independence from the standard frequency A highly precise frequency to
utility companies, a blackout will occur if the sys- which other frequencies can be compared for
tem goes down. Compare INTERACTIVE PHOTO- identification or measurement.
VOLTAIC SYSTEM. standard-frequency oscillator A stable, precise
standard 1. A precise specification governing the oscillator that delivers a standard frequency. Also
dimensions and characteristics of a device or sys- see PRIMARY FREQUENCY STANDARD and
tem (e.g., military standard). 2. A highly accurate SECONDARY FREQUENCY STANDARD.
physical or electrical quantity to which similar standard-frequency signal A calibration and ref-
quantities can be compared (e.g., standard fre- erence signal that is broadcast on a standard fre-
quency). 3. The device or system that produces a quency, such as those transmitted on 2.5, 5, 10,
standard quantity as defined in 2 (e.g., frequency and 15 MHz by the National Bureau of Stan-
standard). 4. Having conventional and widely ac- dards.
cepted characteristics. standard pitch The tone corresponding to the
standard atmosphere Abbreviation, atm. Air pres- frequency 440 Hz (in music, the note A above
sure at sea level (1.013 Pascals, or about 14.7 middle C).
pounds per square inch). Also called ATMO- standard signal generator A (usually continu-
SPHERE. ously variable) high-grade generator of modu-
standard broadcast band Any of numerous fre- lated and unmodulated radio-frequency test
quency bands allocated to conventional broad- signals. A general-purpose instrument of this
cast stations. In the United States, the type usually covers a wide range (e.g., 15 kHz to
amplitude-modulation (AM) radio broadcast band 100 MHz) in several tuning bands. For calibra-
extends from 535 to 1705 kHz, and the fre- tion, a standard signal generator is referred to a
quency-modulation (FM) radio broadcast band primary frequency standard or secondary fre-
extends from 88 to 108 MHz. The television (TV) quency standard.
654 standard subroutine • state

standard subroutine A usually vendor-supplied standing-wave meter See SWR BRIDGE.
computer program segment applicable to more standing-wave ratio Abbreviation, SWR. 1. The
than one program and used as needed as a sub- ratio between the maximum and minimum volt-
routine. age along a transmission line. This quantity is
standard temperature and pressure The condi- sometimes specifically called voltage standing-
tion where the temperature is zero degrees Cel- wave ratio (VSWR). 2. The ratio between the
sius and the pressure is one atmosphere. maximum and minimum current along a
Abbreviated STP. transmission line. 3. The ratio of load impedance
standard time Official civil time in a particular re- to feed-line characteristic impedance or vice
gion. See TIME ZONE. versa, whichever is greater than or equal to 1.
standby 1. The state in which equipment is out of Ideally, the SWR is equal to 1 or 1:1, representing
operation, but can be immediately activated. Also a load impedance that is purely resistive and has
called IDLING. 2. A state of readiness on the part the same value as the characteristic impedance of
of personnel, equipment, or systems. the feed line. A high standing-wave ratio causes
standby battery An emergency power source for a increased loss in the line and can also result in
battery-powered installation. excessive conductor heating or dielectric break-
standby current The CURRENT DRAIN of a cir- down.
cuit, device, or system when in the standby con- standoff insulator An insulator (usually of the
dition. post type) that is used to hold a wire or compo-
standby equipment See EMERGENCY EQUIP- nent away from a chassis or base.
MENT. star 1. In a gravity-battery cell, the copper elec-
standby operation Keep-alive operation during a trode. The name is derived from its star shape.
standby interval (see STANDBY). 2. A star-shaped circuit of three-phase compo-
standby power The power drawn by an equipment nents. Also see WYE CONNECTION.
connected to the power supply, but out of opera- star connection See WYE CONNECTION.
tion. Stark effect The influence of a strong transverse
standby power supply A circuit containing a bat- electric field on the spectrum lines of a gas.
tery, an automatic switch, and sometimes a starlight scope A device capable of viewing in ap-
power inverter. When utility power fails, the parent total darkness. Its operation depends on
switch actuates the supply, and the battery sup- its ability to provide high amplification of ex-
plies power to essential devices or systems. Simi- tremely low light levels, such as that of objects re-
lar to an UNINTERRUPTIBLE POWER SUPPLY. flecting the light from a moonless, but starlit, sky.
standing wave A stationary distribution of current star rectifier See WYE RECTIFIER.
or voltage along a line because of the interactions starter 1. An ignitor electrode in an ignitron (see
between a wave transmitted down the line and a IGNITOR). 2. See STARTING BOX.
wave reflected back; it is characterized by maxi- starting box A special rheostat for starting a motor
mum-amplitude points (loops) and minimum- gradually in steps. The device is provided with an
amplitude or zero points (nodes). electromagnet for holding the arm in the maxi-
mum-speed position and releasing it when power
is interrupted.
Voltage standing waves starting rod An ignitor electrode in an ignitron (see
starting voltage 1. For a gas tube, the minimum
voltage that will initiate the glow discharge. 2. In
appropriate solid-state devices (e.g., a diac), the
voltage at which conduction between electrodes
Feed line
start lead The lead attached to the first turn of a coil.
standing wave
Also called inside lead. Compare FINISH LEAD.
start/stop multivibrator See MONOSTABLE
standing-wave distortion Distortion of current or
stat- A prefix denoting ELECTROSTATIC.
voltage caused by standing waves on a transmis-
statampere The cgs electrostatic unit of current;
sion line terminated in an impedance that con-
1 statampere = 3.335640 — 10“10 ampere.
tains reactance, and/or that differs from the
statcoulomb The cgs electrostatic unit of charge;
characteristic impedance of the line.
1 statcoulomb = 3.335640 — 10“10 coulomb.
standing-wave indicator 1. A device, such as a
state 1. The present condition (i.e., on or off, true
lamp or meter, used to detect standing waves.
or false, 1 or 0, high or low) of a bistable device,
2. Standing-wave meter (see SWR BRIDGE).
such as a flip-flop. 2. The physical or electrial
standing-wave loss The additional loss, over the
condition or status of a component, device,
matched-line loss, that occurs in a transmission
circuit, or system.
line when the standing-wave ratio (SWR) is not 1.
statement • statics

statement The contents of a line in a source- static dump In computer operations, a dump oc-
language computer program. curring at a predetermined point in a program
state of charge The amount of charge, measured run or at the end of the run.
in coulombs or ampere hours, in a storage cell or static electricity Energy in the form of a station-
battery at a given time. A measure of the available ary electric charge, such as that stored in capac-
remaining energy in the cell or battery. itors or produced by friction or induction.
statfarad The cgs electrostatic unit of capacitance; static emitter current See DC EMITTER CUR-
1 statfarad = 1.112650 — 10-12 farad. RENT.
stathenry The cgs electrostatic unit of inductance; static emitter resistance See DC EMITTER RE-
1 stathenry = 8.987554 — 1011 henry. SISTANCE.
static 1. Pertaining to that which is constant in static emitter voltage See DC EMITTER VOLTAGE.
quantity (e.g., static collector current of a transis- static flip-flop A flip-flop (see BISTABLE MULTIVI-
tor). 2. Pertaining to that which is at rest (e.g., BRATOR) using direct-current operating voltages.
static electricity). 3. The radio noise (sferics) pro- A single pulse switches the unit from on to off,
duced by electric discharges in the atmosphere, and vice versa. Compare DYNAMIC FLIP-FLOP.
usually lightning. 4. Pertaining to a test-and- static forward current transfer ratio Symbol,
measurement mode for a unit or device, without HFE. An expression of gain in a bipolar transistor.
subjecting the unit or device to regular operation. It can range from a factor of just a few times up to
Compare DYNAMIC. hundreds of times. Mathematically,
static base current See DC BASE CURRENT.
static base resistance See DC BASE RESIS-
TANCE. where IC is the collector current and IB is the base
static base voltage See DC BASE VOLTAGE. current. The HFE rating is important because it
static cathode current See DC CATHODE CUR- gives engineers an indication of the greatest cur-
RENT. rent amplification that can be obtained with a
static cathode resistance See DC CATHODE RE- particular transistor.
SISTANCE. static frequency multiplier A magnetic-core de-
static cathode voltage See DC CATHODE VOL- vice, similar to a magnetic amplifier or peaking
TAGE. transformer, that provides harmonics by distort-
static characteristic An operating characteristic ing a sine-wave signal.
determined from constant, rather than alternat- static gate current See DC GATE CURRENT.
ing or fluctuating, values of independent and de- static gate resistance See DC GATE RESISTANCE.
pendent variables. Examples: the direct-current static gate voltage See DC GATE VOLTAGE.
(dc) characteristics of diodes, transistors, and in- static grid current See DC GRID CURRENT.
tegrated circuits. Compare DYNAMIC CHARAC- static grid voltage See DC GRID VOLTAGE.
TERISTIC. static hysteresis The condition in which the mag-
static charge Energy stored in a stationary electric netization of a material (when it has the same in-
field; electricity at rest. tensity as the magnetizing force) is different when
static collector A device that grounds the rotating the force is increasing than when the force is de-
wheels of a motor vehicle, thereby removing the creasing, regardless of the time lag. Compare
static electricity generated by the friction of the VISCOUS HYSTERESIS.
tires on the roadway. static induction See ELECTROSTATIC INDUC-
static collector current See DC COLLECTOR TION.
static collector resistance See DC COLLECTOR TOR.
RESISTANCE. static memory Also called nonvolatile memory. In
static collector voltage See DC COLLECTOR a computer, a data memory medium (such as
VOLTAGE. programmable read-only memory, or PROM) in
static convergence In a color-television picture which information is stored until it is altered or
tube, the convergence of the three undeflected erased. It does not require a source of power to
electron beams at the center of the aperture maintain the integrity of the data. Compare
static device A device with no moving parts. static mutual conductance See STATIC TRANS-
static discharge resistor A fixed resistor con- CONDUCTANCE.
nected between the earth and the high side of the static plate current See DC PLATE CURRENT.
power line in a television receiver to drain off at- static plate resistance See DC PLATE RESIS-
mospheric electric charge. TANCE.
static drain current See DC DRAIN CURRENT. static plate voltage See DC PLATE VOLTAGE.
static drain resistance See DC DRAIN RESIS- statics The study of forces, bodies, poles, charges,
TANCE. or fields at rest or in equilibrium. Compare
static drain voltage See DC DRAIN VOLTAGE. DYNAMICS.
656 static skew • step counter

static skew In magnetic tape recording or play- Stator
back, the amount of lead or lag time of one track, plates
with respect to another. Ideally, the static skew
should be zero or practically zero.
static source current See DC SOURCE CURRENT.
static source resistance See DC SOURCE RESIS-
static source voltage See DC SOURCE VOLTAGE.
static storage Also called nonvolatile storage. In a
computer, a data storage medium (such as mag-
netic or optical disk) in which information is
stored until it is altered or erased. It does not re-
quire a source of power to maintain the integrity
of the data. Virtually all data storage media are of
stator plate
this type, as contrasted with memory, which is of-
ten volatile (see STATIC MEMORY and VOLATILE
MEMORY). stator section See STATOR, 3.
static stability The ability of a robot to maintain statoscope An aircraft altimeter that shows small

its balance while standing still. A robot with two changes in altitude.
legs is generally poor in this respect. This is one statvolt The cgs electrostatic unit of electromotive

of the reasons why humanoid robots (androids) force; 1 statvolt = 299.7925 volts.
are difficult to engineer. A minimum of three legs statweber The cgs electrostatic unit of magnetic
flux; 1 statweber = 299.7925 webers (2.997925 —
is necessary for good static stability.
1010 maxwells).
static subroutine In computer programming, a
subroutine that always serves the same purpose ST band A section of the S BAND, extending from
[i.e., it does not need to be tailored (according to 1850 to 2000 MHz.
parameters) for a specific application]. std Abbreviation of STANDARD.
station 1. An installation consisting of a transmit- steady-state component A quantity whose value
ter, receiver, or both. 2. A test-equipment instal- remains constant during normal operation of a

lation or position. 3. A computer installation circuit or device, as opposed to an alternating,
including peripherals. fluctuating, or transient component.
stationary battery A (usually wet storage) battery steerable antenna A directional antenna having a
not normally moved when in use. rotatable major lobe.
stationary state A particular energy state for an steering diode See DIRECTIONAL DIODE.
Stefan-Boltzmann constant Value, 5.67051 —
atom represented by its electrons being in shells
10“8 Wm“2K“4.
at specific energy levels.
stationary wave See STANDING WAVE. Stefan-Boltzmann law The thermal-radiation law
station authorization The legal privilege assigned that shows the total emissive power of a black-
to a broadcast or communications station, allow- body to be proportional to the fourth power of the
ing that station to be used for the purpose of absolute temperature of the body.
transmitting electromagnetic signals. stenode See CRYSTAL FILTER.
station license See STATION AUTHORIZATION. step 1. A computer program instruction. 2. A sin-
statistical quality control Quality control based gle action in the operation, maintenance, or trou-
upon the techniques of probability and statistics bleshooting of equipment. 3. A specific increment
in analyzing findings, making predictions, and in a quantity (such as frequency, voltage, current,
formulating procedures for sampling. etc.). 4. A sharp or rapid change in the value of a
statmho The cgs electrostatic unit of direct- quantity.
current conductance; 1 statmho = 1.112650 — step-by-step operation See STEPTHROUGH OP-
10“12 siemens. ERATION.
statoersted The cgs electrostatic unit of mag- step change A single-increment change in a value.
netizing force; 1 statoersted = 265.458 A/m step circuit A circuit that produces a step (sharp
(3.33585 — 10“11 oersted). change of slope) in the response curve of an am-
statohm The cgs electrostatic unit of direct-current plifier.
resistance; 1 statohm = 8.987554 — 1011 ohm. step counter 1. A stair-step circuit arranged to
stator 1. A stationary coil. Compare ROTOR, 1. 2. count input pulses. The output capacitor of the
The stationary member of a motor or generator. circuit discharges when a predetermined number
Compare ROTOR, 2. 3. The stationary-plate sec- of input pulses has raised the capacitor voltage to
tion of a variable capacitor. Compare ROTOR, 3. the level required to trigger a counter. 2. In a com-
stator coil A stationary coil (see STATOR, 1, 2). puter or calculator, a circuit or device that counts
stator plate(s) The stationary plate(s) of a variable the steps in an operation (such as division, multi-
capacitor. Compare ROTOR PLATE. plication, or shifting) called for by an instruction.

step-down ratio • stop amplifier

step-down ratio In a circuit or device, such as a special circuit to obtain stereo sound from Multi-
step-down transformer or cathode follower, the channel Television Sound signals. Compare
ratio of the low output voltage to the high input STEREO-READY.
voltage. Compare STEP-UP RATIO. stereo amplifier A two-channel amplifier for bin-
step-down transformer A transformer delivering aural reproduction (see BINAURAL).
an output voltage that is lower than the input stereophonic Pertaining to equipment or tech-
voltage. In such a transformer, the secondary niques for producing a (somewhat) three-dimen-
(output) winding contains fewer turns than the sional perspective of sound reproduction.
primary (input) winding. Compare STEP-UP stereophonic sound system See STEREO SYSTEM.
TRANSFORMER. stereo-irrelevant Pertaining to sound compo-
step function See UNIT FUNCTION. nents in a stereo system that are of equal mag-
step generator 1. A signal generator that delivers nitude in both (or all) channels. Thus, these
a step function (see UNIT FUNCTION). 2. A circuit components sound the same whether the system
or device that generates a STAIR-STEP WAVE. is reproducing stereophonic sound or monaural
stepped leader The probing flow of electrons sound.
through the atmosphere preceding a lightning stereo phono cartridge A phono cartridge capable
stroke. Once the path has been established, the of reproducing sound from stereo discs.
discharge takes occurs along the ionized path stereo-ready Pertaining to a television receiver or
determined by the stepped leader. It is so called videocassette recorder (VCR) that can deliver
because the electrons move in hesitations, stereo sound from Multichannel Television Sound
jumping several meters with each advance or signals without the need for a decoding circuit.
stepper motor A motor in which the shaft ad- stereo recording A method of recording in which
vances in uniform angular steps, instead of rotat- two independent sound channels are transferred
ing continuously. These motors are extensively to some medium simultaneously, with the inten-
used in robotic devices. When such a motor is tion that the two channels be reproduced at the
stopped and its coils are carrying current, the same time.
shaft resists turning. stereoscopic television Television in which the
stepping relay See STEPPING SWITCH. reproduced image appears three-dimensional.
stepping switch A multiposition rotary switch in stereo system A multichannel, high-fidelity sound
which an electromechanical ratchet mechanism reproduction system including an amplifier and
advances to the next contact position each time various other components, such as a radio re-
that a pulse of current is received. ceiver, compact-disc (CD) player, tape player,
step-through operation A way of operating a com- turntable, and speakers.
puter, usually during a debugging operation, in stereotape Magnetic tape bearing more than one
which program instructions are executed one at a channel (usually two channels) for the recording
time by direction of the user. Also called single- and reproduction of stereophonic sound.
step operation and step-by-step operation. sterilizer Any electronic device, such as an ultravi-
step-up ratio In a circuit or device, such as a step- olet generator, used to kill germs.
up transformer or voltage amplifier, the ratio of stethoscope An electronic or nonelectronic instru-
the high output voltage to the low input voltage. ment used by physicians to listen to the heart-
Compare STEP-DOWN RATIO. beat and other body sounds, and by technicians
step-up transformer A transformer delivering an to listen to mechanical sounds.
output voltage that is higher than the input volt- still 1. A stationary picture on television. 2. A pic-
age. In such a transformer, the secondary (out- ture transmitted or received by means of facsimile.
put) winding contains more turns than the 3. A print on photographic paper of a negative.
primary (input) winding. Compare STEP-DOWN still television See FACSIMILE.
TRANSFORMER. stinger A brief, loud sound burst, such as a musi-
steradian A unit of solid-angle measure. A cone- cal chord, sometimes used for effect in recorded
shaped solid angle that has a vertex at the center audio or audio-visual presentations.
of a sphere (of radius r), that cuts off a portion of stn Abbreviation of STATION. (Also, sta.)
the sphere™s surface whose outer perimeter is a STO Abbreviation of STORAGE FUNCTION.
circle, and that has an area (as measured on the stochastic The condition in which, at any instant,
sphere™s surface) of r2. Also see SOLID ANGLE. a given variable can assume a state dependent on
Sterba array See BARRAGE ARRAY. previous states, as well as chance elements (e.g.,
Sterba curtain See BARRAGE ARRAY. words uttered extemporaneously by a speaker are
stereo 1. Contraction of STEREOPHONIC. 2. Gen- random in that they cannot be predicted), while
eral term for a two-channel high-fidelity audio re- also being dependent, by the application of gram-
production system. mar, on previously spoken words (i.e., previous
stereo-adaptable Pertaining to a television receiver states).
or videocassette recorder (VCR) that requires a stop amplifier See REJECT AMPLIFIER.
658 stopband • storage register

memory to a more permanent medium. Compare
MEMORY. 3. The retention of data of any kind,
such as an oscilloscope image or video display,
for use at a later time. 4. The retention of electric
energy or charge, as in a capacitor or electro-
tuner chemical cell. 5. The retention of energy in the
form of a magnetic field, as in an inductor. 6. The
retention of potential energy in any form.
storage allocation The assignment of computer
memory areas to certain kinds of information, as
outlined in a source program and implemented
by a compiler.
storage battery A rechargeable battery; the tech-
nical term is secondary battery. Also see STOR-
storage capacity 1. The amount of data that can
be stored in a specific medium, such as a hard
disk, diskette, or tape. Generally measured in
bytes, kilobytes, megabytes, gigabytes, or ter-
abytes. 2. The energy-delivering capability of a
Tape storage battery in terms of ampere-hours, mil-
player liampere-hours, or other current-time units for a
specific rated voltage.
storage cell 1. An electrochemical cell whose po-
tential can be restored by charging it with elec-
tricity. Compare PRIMARY CELL. Also see CELL.
Turntable 2. The smallest part of a computer storage
medium. 3. In computer data storage, the part
that can hold a data unit (e.g., a bit).
storage cycle In computer operation, the period
during which a location of a cyclic storage device
cannot be accessed.
stereo system storage density The number of data units (e.g.,
bytes, kilobytes, or megabytes) that can be stored
in a given length or area of a storage medium.
storage device A medium into which data can be
stopband The continuous spectrum of frequencies
placed and kept for later use. Examples: mag-
rejected by a filter, selective amplifier, or other
netic disk, magneto-optical disk, optical disk,
band-suppression device.
and magnetic tape.
stopband ripple Single or multiple attenuation
storage dump See DUMP.
peaks within the stopband of an elliptic filter,
storage function Abbreviation, STO. The so-called
where the frequency of the attenuation peak(s)
“memory” function of a microcomputer chip. It
is/are associated with the resonant circuit(s) in
causes data to be inserted into memory or storage
the filter.
for later use. It is commonly used in programmable
calculators, automatic-dialing telephones, and ra-
stop element In digital transmission, a bit or set of
dio receivers. Also called memory function.
bits indicating the end of a character, and serving
storage laser A laser that stores intense energy be-
to inform the receiving device of the end of the
fore flashing.
storage life See SHELF LIFE.
storage mesh In the cathode-ray tube (CRT) of a
stopper resistor See STOPPING RESISTOR.
storage oscilloscope, a fine metal mesh electrode
stopping capacitor See BLOCKING CAPACITOR.
that serves as the target on which the image is
stopping coil See CHOKE COIL.
electrostatically stored. Also see STORAGE TUBE.
stopping resistor A parasitic-suppressing resis-
storage oscilloscope An oscilloscope that retains
tor, usually inserted in series with the input
a displayed image until the display is erased. Also
and/or output of a power amplifying device. Also
called stopper resistor.
storage register In computers and calculators, a
storage 1. In computer operations, a medium on
storage unit composed of flip-flops. In computers,
which data can be kept for an extended period of
it is independent of the central processing unit
time. Examples: magnetic disk, magnetic tape,
optical disk. 2. The transferring of data from
storage temperature • stray field

storage temperature 1. The recommended tem- straight-line programming During the writing of
perature for storing specified electronic compo- a computer program, avoiding the creation of
nents. 2. The particular temperature at which loops by repeating a series of instructions to re-
electronic components have been stored. duce execution time.
storage time 1. The interval during which carriers straight-line tracking In a phonograph turntable,
remain in a semiconductor-junction device after linear lateral stylus movement (as opposed to mo-
the bias has been removed. Also see DIODE RE- tion along an arc) as the disc is played. This en-
COVERY TIME. 2. For a switching semiconductor sures that the stylus is always at the optimum
device, the time required for the amplitude of the angle in the disc groove. The result is improved
output pulse to fall from maximum to 90% of sound reproduction, and longer disc and stylus
maximum after the input pulse has fallen to zero. life because of minimal friction between the sty-
3. In a computer, the time required for data to be lus and groove.
transferred from random-access memory (RAM) straight-line wavelength Abbreviation, SLW. Per-
to nonvolatile storage (e.g., hard disk). taining to a variable capacitor in a tuned circuit
storage tube A cathode-ray tube that retains infor- for which the setting-vs.-wavelength curve is a
mation in the form of images on a special elec- straight line; the wavelength variation is linear.
trode until erased by a signal. Compare STRAIGHTLINE CAPACITANCE and
store 1. To place data in a nonvolatile medium STRAIGHT-LINE FREQUENCY.
(such as a hard disk, diskette, optical disk, mag- straight-through amplifier An amplifier in which
netic tape, etc.). 2. To place in the memory of a the input and output circuits are tuned to the
calculator or computer. 3. In computing, a com- same frequency. Compare MULTIPLIER AMPLI-
mand that causes data to be placed in a non- FIER.
volatile medium. In some applications, this is strain A force that compresses or squeezes a body.
called save. 4. A nonvolatile medium on which Compare TENSION, 1.
data has been placed for future use or for archival strain gauge See ELECTRIC STRAIN GAUGE.
purposes. strain-gauge bridge A four-arm resistance bridge
stored base charge The carriers that remain in the in which an ELECTRIC STRAIN GAUGE forms
base layer of a bipolar transistor immediately af- one arm. The resistance of the gauge changes be-
ter the forward bias has been interrupted. This cause of strain. The amount of strain can be de-
charge maintains collector current momentarily. termined by balancing the bridge.
stored-energy welding A method of electric weld- strain-gauge transducer A transducer, other than
ing in which electrical energy is stored slowly, a strain sensor, that uses strain gauges to con-
then released at the rate required for the welding. vert values of pressure into their electrical
STP See STANDARD TEMPERATURE AND PRES- analogs (e.g., pressure transducer and strain-
SURE. gauge phonograph pickup).
straight adapter An inline coaxial fitting for join- strain pickup A phonograph pickup using a strain
ing two fixture-terminated coaxial lines in series. gauge to convert sound vibrations into a varying
straight angle An angle measuring 180 degrees. electric current.
straight dipole A (usually center-fed) dipole an- strand A single solid conductor in a STRANDED
tenna having only one radiator. Also see DIPOLE WIRE.
ANTENNA. stranded wire A conductor composed of several
straightforward Pertaining to data transmission in non-insulated wires twisted together to provide
one direction only. mechanical flexibility. Compare SOLID WIRE.
straight-gun CRT A cathode-ray tube (CRT) in stratosphere The portion of earth™s upper atmo-
which the electron gun projects the beam in a sphere beginning at a height of approximately 10
straight line through the deflecting elements to miles and extending to the ionosphere.
the screen. Compare BENT-GUN CRT. stray capacitance Inherent capacitance in a place
straight-line capacitance Abbreviation, SLC. Per- where it can be detrimental, such as that between
taining to a variable capacitor for which the the turns of a coil or between adjacent areas in a
setting-vs.-capacitance curve is a straight line; circuit. Also see STRAY COMPONENT.
the capacitance variation is linear. Compare stray component An electrical property that exists
STRAIGHT-LINE FREQUENCY and STRAIGHT- as an inherent, and usually undesirable, side ef-
LINE WAVELENGTH. fect in a circuit or device. Thus, for example,
straight-line coding See STRAIGHT-LINE PRO- STRAY CAPACITANCE unavoidably exists be-
GRAMMING. tween parallel conductors, and STRAY INDUC-
straight-line frequency Abbreviation, SLF. Per- TANCE is present in all wiring.
taining to a variable capacitor in a tuned circuit stray field The portion of an electric or magnetic
for which the setting-vs.-frequency curve is a field that extends beyond the immediate vicinity
straight line; the frequency variation is linear. of the circuit with which it is associated, and
Compare STRAIGHT-LINE CAPACITANCE and which is, therefore, capable of interfering with
STRAIGHT-LINE WAVELENGTH. other circuits or devices.
660 stray inductance • stylus friction

strobe 1. See ELECTRONIC FLASH, 1. 2. See
interacts strobe light 1. See ELECTRONIC FLASH, 1. 2. See
with nearby
Strobolume Trade name for a type of high-output
stroboscope 1. An instrument that emits bright,
adjustable-rate flashes of light. When this light il-
luminates an object that is rotating or vibrating
at a fixed period, and the flash rate is made to
match that period, the object seems to stand still
stray field
and can be examined for flaws or faulty operation
(and its speed can be measured). 2. A rotatable,
stray inductance Inherent inductance in a place slotted disk for producing the effect defined in 1.
where it can be detrimental (e.g., inductance in stroboscopic disk A rotatable disk with alternating
the coil of a wirewound resistor). Also see STRAY white and black radial regions, used in conjunc-
COMPONENT. tion with a strobe light for precise measurement of
stray resistance Inherent resistance in a place the speed of a phonograph turntable.
where it can be detrimental, such as leakage re- strobotron A gas tetrode tube used as the flashing
sistance in a dielectric, and wire resistance in an light source in a stroboscope.
inductor. stroke speed See SCANNING FREQUENCY.
streaking In television or facsimile, a form of dis- strong coupling See CLOSE COUPLING.
tortion in which the image appears enlarged in strontium Symbol, Sr. A metallic element of the al-
the horizontal, but not the vertical. kaline-earth group. Atomic number, 38. Atomic
stress 1. See STRAIN. 2. See TENSION, 1. 3. The weight, 87.62. It is used in some ceramic di-
force per unit area that produces STRAIN or TEN- electrics, such as barium-strontium titanate.
SION on a body. Strowger exchange A telephone system incorpo-
stretch The amount by which a material being rating Strowger switches.
measured with an electronic device increases in Strowger switch A switch with one input and 100
surface dimensions. Compare SHRINK. individually selectable outputs. It is used with
stretched string A long, thin wire or string that vi- telephone switching networks. The telephone dial
brates at a certain frequency, causing standing code causes a contact to move vertically and hor-
waves. It generally exhibits a specific fundamen- izontally in such a way that a particular output is
tal frequency and integral harmonics of this fre- connected to the input. Each output has a
quency. As the wavelength is cut in half, the unique dial code and each dial code has a unique
frequency doubles. output.
strike To initiate a discharge, as in striking a gas structured programming Computer programming
tube. using a limited number of procedural sets, while
striking voltage See STARTING VOLTAGE. minimizing branches to make the program as
string 1. In computer operations, a set of items in forward-going as possible. This allows it to be
a sequence determined by the order of keys. 2. In easily modified or debugged.
a computer memory, a sequence of bits or char- STS switch See SPACE-TIME-SPACE SWITCH.
acters. 3. Any group of series-connected compo- stub A (usually short) section of transmission line
nents or circuits. that is patched onto a longer line for tuning or
string electrometer See BIFILAR ELECTROME- impedance matching.
string variable A string of characters, usually stub tuner A tuning unit consisting of a stub with
forming a word or phrase, represented by a vari- a short circuit that can be moved along the stub.
able name and character string symbol (BASIC™s stub trap See INTERFERENCE STUB.
$, for example) in a computer program. stub-type wavetrap See INTERFERENCE STUB.
strip chart A longitudinal, as opposed to circular, stuffing bits In a digital communications system,
chart for graphic recording. In a rectilinear chart, extra bits inserted into some words so that all the
both coordinates are straight; in a curvilinear words are the same length.
chart, the crosswise coordinates are arcs. styli Plural of STYLUS.
strip core A ferromagnetic core material made from stylus 1. The “needle” that conveys vibrations to or
a strip of the substance. The method of manufac- from the disk in phonograph-disc recording or
ture results in superior ferromagnetic qualities, playback. 2. One of the pins in the print head of
but also imparts a polarization to the material. a dot-matrix printer.
strip fuse A fuse in which the fusible element is a stylus drag See NEEDLE DRAG.
flat strip of low-melting-point metal. Compare stylus friction Rubbing of the stylus against the
WIRE FUSE. record groove in phonograph-disc playback.
stylus pressure • subsidiary communication authorization

stylus pressure See VERTICAL STYLUS FORCE. subcarrier oscillator In a color-television receiver,
stylus printer See WIRE PRINTER. the oscillator operating at the burst (chromi-
stylus scratch See NEEDLE SCRATCH. nance-subcarrier) frequency of 3.579545 MHz.
sub Abbreviation of subtract. subchassis An auxiliary chassis on which one sec-
sub- Prefix denoting under, below, less than, or tion of a larger piece of equipment is completely
lower than, with respect to size, value, or rank. assembled and wired.
Compare SUPER-. subfrequency See SUBHARMONIC.
subassembly A completely fabricated unit that subharmonic An integral submultiple of a funda-
forms part of a larger unit into which it easily fits. mental frequency. Thus, for example, the 10th
subatomic particle 1. Any of various particles that subharmonic of 15 MHz is 1.5 MHz.
comprise atoms of matter. 2. A particle smaller submarine cable An underwater cable designed to
than an atom. See, for example, ANTI-PARTICLE, withstand continuous immersion.
ELECTRON, MESON, NEUTRETTO, NEUTRINO, submarine robot A robot designed for underwater
NEUTRON, NUCLEON, POSITRON, and PROTON. operation. It can be operated via telepresence or
subaudible 1. Pertaining to any frequency falling by simple remote control, usually using a con-
below the limit of human hearing, that is, less ventional or fiberoptic cable. Some underwater
than about 20 Hz. 2. Any sound that is too low in robots have manipulators attached; others are
amplitude to be heard. equipped only with cameras, lights, and propul-
subaudible tone A signal, usually a steady, sine- sion devices.
wave tone, sent along with a radio signal. The subminiature jack A female connector with an in-
side diameter of 3„32 inch.
tone frequency varies from about 20 Hz to 200
Hz, below the audio cutoff frequency of most voice subminiature plug A male connector with an out-
side diameter of 3„32 inch.
communications systems. Subaudible tones are
used mainly for privacy. The receiver is pro- submultiple A fractional multiple, usually in refer-
grammed to receive only signals having the cor- ence to a frequency. For example, 7.2 MHz is a
rect subaudible tone frequency. submultiple of 14.4 MHz. See SUBHARMONIC.
suballocation A portion of a radio-frequency subpanel The front panel of a removable unit or
broadcast or communications band that is legally module that forms a part of a larger unit.
set aside for specific purposes or users, e.g., the subroutine In a computer program, a sequence of
Extra-class segment of the 40-meter amateur-ra- instructions for carrying out a section of the pro-
dio band. gram™s function. It is usually entered (led to) by a
subband 1. A portion of a frequency band with spe- conditional branch (jump) instruction in the main
cific characteristics. 2. A portion of a radio- program.
frequency broadcast or communications band that subscriber An individual user of a communica-
is set aside, legally or by convention, for specific tions network or service.
purposes [e.g., the single-sideband (SSB) portion subscript A small number or letter written to the
of the 20-meter amateur-radio band]. lower right (and occasionally to the lower left) of
subcarrier A modulated carrier wave that composes another number or letter to identify the latter
the modulating signal for another carrier wave. from others of the same designation (e.g., a5, Sn).
subcarrier band The band of frequencies in which Compare SUPERSCRIPT.
a subcarrier signal is transmitted. subscription TV A television (TV) service paid for
subcarrier frequency modulation In a system in by subscribing viewers. The signals are scram-
which a carrier frequency is obtained by beating a bled so as to be useless to nonsubscribers, and
low-frequency radio-frequency (RF) signal with a legitimate subscribers are provided with a de-
high-frequency RF signal, the application of fre- coder to unscramble the telecasts.
quency modulation to the low-frequency com- subset 1. In statistics and set theory, a set whose
ponent. The technique is sometimes used in members are all contained in a larger set. 2. A
sweep-frequency signal generators. telephone handset or deskset (subscriber™s set).
3. A modulator/demodulator for making
business machines compatible with telephone
High - freq.
subsidiary communication authorization Abbre-
RF osc.
viation, SCA. An authorization provided by the
Mixer Out
Federal Communications Commission (FCC) for a
frequency-modulation (FM) broadcast station to
RF osc.
transmit, in addition to its main program, a sec-
ond program within the assigned bandwidth usu-
Reactance ally consisting of commercial-free background
modulator music on a subcarrier that can be detected only
with a special receiver or with a special adapter
attached to a standard FM receiver.
subcarrier frequency modulation
662 subsidiary feedback • sun battery

subsidiary feedback Feedback other than the that have been filtered through additive-primary
main feedback in a system. lenses.
subsonic frequencies Frequencies below the subtrahend In the process of subtraction, the
range of hearing, that is, less than about 20 Hz. quantity that is subtracted from another (the
Also called ULTRALOW FREQUENCIES and SUB- minuend) to produce the remainder or difference.
AUDIBLE FREQUENCIES. subwoofer A speaker designed to effectively repro-
substation An intermediate electricity-distributing duce extremely low audio frequencies, in some
location from which electrical energy is trans- cases, subaudible (below 20 Hz).
formed and transmitted to users within a given successive derivatives Successive repetition of
geographical area. the operation of differentiating a function, which
substitution capacitor A capacitor used tem- yields the first derivative, second derivative, and
porarily in place of another of usually the same so on to the nth derivative.
value, as in troubleshooting. Also see CAPACI- successive integration The operation of double or
TOR SUBSTITUTION BOX. triple integration.
substitution inductor An inductor used tem- Suhl effect A reduction in hole life that occurs in a
porarily in place of another of usually the same semiconductor material in the presence of a mag-
value, as in troubleshooting. Also see INDUCTOR netic field.
SUBSTITUTION BOX. suite 1. A group of computer programs run succes-
substitution method 1. A method of measuring a sively as a job. 2. A bundled, high-end software
quantity (such as capacitance, inductance, or re- package used especially in business computing.
sistance) in which the value of the unknown sulfate Contraction of lead sulfate.
quantity is determined in terms of the amount of sulfation In a lead-acid storage cell, the formation
a standard quantity that must be removed to re- of disabling lead sulfate during discharge of the
store the test circuit to its original state of bal- cell.
ance. 2. A method of troubleshooting in which sulfur Symbol, S. A nonmetallic element. Atomic
good components are substituted for bad ones in number, 16. Atomic weight 32.06.
a circuit (see, for example, SUBSTITUTION CA- sulfur hexafluoride A gas used as a coolant and
PACITOR, SUBSTITUTION INDUCTOR, SUBSTI- insulant in some power transformers.
TUTION RESISTOR, SUBSTITUTION SPEAKER, sulfuric acid Formula, H2SO4. An acid used in di-
and SUBSTITUTION TRANSFORMER). lute solution as the electrolyte of a lead-acid bat-
substitution resistor A resistor used temporarily tery. This highly corrosive fluid also has many
in place of another of usually the same value, as industrial uses.
in troubleshooting. Also see RESISTOR SUBSTI- sum The result obtained by adding two or more
substitution speaker A loudspeaker used tempor- sumcheck See SUMMATION CHECK.
arily in place of another, as in troubleshooting. sum frequency 1. In an amplitude-modulated car-
substitution transformer A transformer used rier, the upper sideband frequency (i.e., the side-
temporarily in place of another having the same band equal to the carrier frequency plus the
characteristics, as in troubleshooting. modulating frequency). Compare DIFFERENCE
substrate A plate, wafer, panel, or disk of suitable FREQUENCY. 2. In superheterodyne operation,
material on (or in) which the components of a an intermediate frequency equal to the signal fre-
unit, such as an integrated or printed circuit, are quency plus the local-oscillator frequency.
deposited or formed. summation 1. The sum of a finite number of
subterranean 1. Pertaining to components, sys- terms. Thus, the total resistance of n resistors
tems, or devices installed underground. It is ap- connected in series is the summation of all R (re-
plicable especially to cables. 2. Pertaining to a sistance) terms. 2. A frequency equal to the sum
phenomenon, such as the propagation of electric of two other frequencies.
currents or acoustical waves, that occurs under- summation check In computer operations, a
ground. check carried out on a group of digits. The result
subterranean acoustical communication A met- of adding the digits, and disregarding any over-
hod of communication that uses low-frequency flow, is a check digit that can be compared with a
sound waves, such as SONAR, to communicate standard value for the operation to verify the in-
via conduction through earth or water. tegrity of data.
subtracter See ELECTRONIC SUBTRACTER. summer 1. See ADDER. 2. See SUMMING AMPLI-
subtractive color A color formed by mixing sub- FIER.
tractive primary pigments. summing amplifier An operational amplifier
subtractive primaries Broad-spectrum pigments whose output is the sum, or is proportional to the
used in printing to produce a wide variety of col- sum, of several inputs.
ors through filtering. These primaries are cyan sun battery A set of photovoltaic cells connected in
(blue-green), magenta (pink-red), yellow, and series, parallel, or series-parallel to produce use-
sometimes black. They are used to print images ful output voltages and currents.
S units • supermodulation


Relative sunspot numbers
V2 V0
Vc0 = ’ V1

summing amplifier

S units In radio (especially amateur radio), grada-
1970 1980 1990 2000
tions reflecting the strength of received signals.
Typically, a value of S9 (9 s-units), representing
sunspot cycle
“extremely strong signals,” is equal to a strength
of 50 microvolts. The next lower S unit (S8) is
supercardioid microphone A microphone that is
6 dB lower in voltage (i.e., 25 microvolts); S7 is
highly sensitive in one direction and insensitive
12 dB below S9 (i.e., 12.5 microvolts), etc.
in all other directions. The directional pattern is
sun lamp An incandescent or fluorescent lamp with
similar to a CARDIOID PATTERN, but is exagger-
high ultraviolet output, used in medicine for the
ated along the axis of optimum response.
treatment of certain skin disorders. It can also be
superconducting cable A cable in which super-
used for skin tanning; most physicians discourage
conductivity is achieved by surrounding the cable
habitual use of the lamps for this purpose.
with liquid helium to lower its temperature to
sunlight lamp A lamp that produces visible light
near absolute zero.
whose spectral distribution is similar to that of
superconductivity The virtual disappearance of
typical daylight. It generally produces more blue
resistance in some metals cooled to temperatures
and violet light than a conventional lamp. It is
in the vicinity of absolute zero. Also see CRYO-
sometimes used for indoor lighting in winter at
high latitudes, and/or to enhance plant growth.
superconductor A material or device that displays
sunlight-powered laser A laser whose action is
stimulated by sunlight collected by a system of
super flatpack An integrated-circuit package of
mirrors and lenses. The life of the device is long,
the flatpack type having considerably more com-
compared with that of conventional lasers.
ponents and leads than those in the conventional
sun-pumped laser See SUNLIGHT-POWERED
superhet Contraction of superheterodyne.
sun relay See SUN SWITCH.
superheterodyne circuit A circuit in which the in-
sunspot An area on the sun™s surface that is visible
coming signal in a first detector (or mixer) beats
as a dark, irregular region of variable size, gener-
with the signal of a local oscillator, resulting in a
ally several thousand miles across. Sunspots are
lower (intermediate) frequency, which then is am-
believed to be comparatively cool regions associ-
plified by an intermediate-frequency (IF) ampli-
ated with solar magnetic disturbances. The num-
fier. This IF signal is detected by a second
ber of sunspots is correlated with the frequency
detector whose output is amplified by an audio-
and intensity of solar flares (see SOLAR FLARE).
frequency (AF) amplifier. Because the IF amplifier
sunspot cycle Regular periodic variation of sun-
operates at a single (fixed) frequency, it can be
spot activity. The time between peaks in activity
adjusted for optimum selectivity and gain. Also
is approximately 11 years.
called superhet circuit.
sun switch A photoelectric switch or relay actu-
superheterodyne receiver A radio or television re-
ated by sunlight and used for various domestic
and industrial purposes, such as switching
superhigh frequency See RADIO SPECTRUM.
lights, operating window shades, etc.
Supermalloy An alloy having a maximum perme-
sup Abbreviation of SUPPRESSOR.
ability of 106.
super Contraction of supersonic.
supermodulation A type of amplitude modulation
super- Prefix denoting over, above, greater than, or
(AM) in which one radio-frequency (RF) power
higher than, with respect to size, value, or rank.
stage continuously generates the carrier, and a
Compare SUB-.
second (usually identical) RF power stage is gated
superaudible frequency See ULTRASONIC FRE-
into full operation at the proper instant by the au-
dio modulation to add additional RF power (cor-
superbeta transistor A transistor or transistor
responding to 100% modulation) to the signal. At
combination, such as a Darlington pair (see
the same time, the carrier amplitude is decreased
COMPOUND CONNECTION), that provides a very
by the proper amount to fulfill the conditions of a
high current amplification factor (beta).
664 supermodulation • surface-barrier transistor

signal amplitude swing between zero and twice supervisor 1. In a computer, a set of routines that
maximum for 100% modulation. oversees the operation of the system. The super-
superposition In a complex wave, the manner in visor routines are coordinated by the central pro-
which the constituent waves combine. The in- cessing unit. 2. The execution of such a set of
stantaneous value of the complex wave is equal to routines. 3. A microcomputer that oversees the
the vector sum of the instantaneous values of all operation of a security system.
the constituent waves. supervisory circuit In a security system, a link
superposition theorem In a network of linear ele- between a sensor and the central computer or
ments, if a voltage E1 in branch A causes a cur- control device. This link can be via electric cur-
rent I1 to flow through branch C, and if a voltage rent through a wire or cable, but other methods
E2 in branch B (which might be identical with can be used, such as fiberoptics, line-of-sight op-
branch A) causes a current I2 to flow through tics, infrared, ultrasonic, or radio.
branch C, then E1 in branch A and E2 in branch supply 1. See CURRENT SUPPLY. 2. See POWER
B applied simultaneously will cause a current SUPPLY. 3. See VOLTAGE SUPPLY.
equal to I1 + I2 to flow through branch C. Compare supply current Alternating or direct current avail-
COMPENSATION THEOREM, MAXIMUM POWER able for operating a circuit, device, or system.
TRANSFER THEOREM, NORTON™S THEOREM, supply frequency The frequency of an alternating-
RECIPROCITY THEOREM, and THEVENIN™S current power supply.
THEOREM. supply power The maximum power that can be re-
superpower An arbitrary term denoting very high liably delivered by an alternating-current or
power. In the rating of standard broadcast sta- direct-current power supply.
tions, it has come to signify 1,000,000 watts (one supply reel In a reel-to-reel tape recorder or player,
megawatt) radio-frequency (RF) power output. the reel that is initially full, and that gradually
superradiance In a laser, a rapid increase in inten- empties as the tape moves through the machine.
sity of fluorescent-line emission with increasing supply voltage The voltage of an alternating-cur-
excitation power. rent or direct-current power supply.
superregenerative circuit A regenerative detector suppressed carrier A carrier that has been canceled
circuit in which regeneration is periodically in- or filtered out of a carrier/sideband combination.
creased almost to the point of oscillation, then de- suppressed-carrier double sideband See DOU-
creased. This quenching action takes place at a BLE-SIDEBAND and SUPPRESSED CARRIER.
supersonic rate (typically at 50 or 100 kHz) so suppressed-zero instrument A meter or graphic
that the quenching is inaudible. The result is that recorder in which the zero point is off-scale or up-
much more regeneration is afforded, without the scale, but has been brought to scale-zero by
detector going into oscillation, than is possible by means of mechanical adjustment or use of a
simply increasing the regeneration manually. An bucking voltage.
extremely sensitive detector is the result. suppressor 1. A filter used to suppress radio inter-
supersaturated solution A solution that contains ference. 2. See AUTOMATIC NOISE LIMITER. 3.
more solute than it normally would hold. Super- See SPARK SUPPRESSOR. 4. In a pentode vac-
saturated solutions are obtained through special uum tube, a gridlike element between the screen
techniques and are extremely unstable. Compare grid and the plate, used to suppress secondary
SATURATED SOLUTION. Also see SOLUTE; SO- emission. Also see GRID, 2 and PENTODE.
LUTION, 1; and SOLVENT, 2. suppressor circuit The circuit associated with the
superscript A small number or letter written to the suppressor electrode of a vacuum tube.
upper right of another number or letter, the suppressor diode A semiconductor diode used to
BASE, to indicate the power to which the base prevent inductive kickback in circuits, to elimi-
must be raised. Example: 105, e x, y2. Also called nate or reduce transients, or to prevent arcing be-
EXPONENT. Compare SUBSCRIPT. tween make-and-break contacts.
supersensitive relay A relay that operates with a suppressor grid See SUPPRESSOR, 4.
current of less than one milliampere, or with a suppressor modulation A method of modulation
voltage of less than one millivolt. in which a modulating voltage is superimposed
supersonic flow In a gas or liquid, movement of on the suppressor voltage of a pentode radio-
the medium at a speed greater than the speed of frequency power amplifier tube.
sound in that medium. Supersonic flow results in suppressor pulse A pulse that prevents electron
a greatly increased resistance or drag because of flow.
shock waves that form in the medium. surface analyzer A device designed for the mea-
supersonic frequency See ULTRASONIC FRE- surement of surface flatness or uniformity.
QUENCY. surface-barrier diffused transistor See MICRO-
supervised line In a security system, a wire or foil surface-barrier transistor Abbreviation, SBT. A
strip that carries electrical current. If the current pnp transistor made by means of electrolysis and
changes in such a line, an alarm is actuated. electroplating: Two fine streams of indium sulfate
surface-barrier transistor • surveillance radar

surface wave 1. The earth-guided component of a
ground wave. (The other component is the SPACE
WAVE.) 2. An acoustic wave traveling along the
surface of a plate in a surface-wave amplifier or
Base surface-wave filter.
surface-wave amplifier An amplifying device con-
sisting essentially of a surface-wave filter to
which has been added a direct-current-biased n-
Collector type silicon electrode, which is separated from
the crystal substrate of the filter by a very thin
surface-barrier transistor oxide layer. Amplification is produced by interac-
tion between the electron current in the silicon
and the piezoelectric field of the filter. Also see
solution are placed on axially opposite points on
the faces of an n-type wafer. At the same time, a
surface-wave filter An acoustoelectronic device
direct current is passed through the wafer and
consisting essentially of a crystal plate having
solution in such a direction as to remove semi-
electrodes at each end. An alternating-current
conductor material electrolytically from the faces;
(ac) input signal applied to one electrode sets up
the tiny sprayed areas are etched away. When the
acoustic waves that travel along the surface of the
desired wafer thickness is reached at the points
plate to the other electrode, where they generate
of impact, the etching process is arrested by re-
an ac output voltage by piezoelectric action. The
versing the direction of current flow. This reversal
resonant frequency of the device is governed by
causes an indium dot to be plated on each oppo-
the dimensions of the crystal plate. Also see
site face in the etched-out pit. Leads are attached
to the collector and emitter dots and to the wafer
surge A sudden rise or flow of current or voltage.
surge absorber See SURGE SUPPRESSOR.
surface-charge transistor A semiconductor device
surge arrester See SURGE SUPPRESSOR.
consisting essentially of two narrowly separated
surge current A heavy current that flows initially
plates (source electrode and receiver electrode)
into a capacitor when a charging voltage is applied.
deposited on the film-insulated surface of a sili-
surge impedance Symbol, Zo. The impedance seen
con chip, and a third, overlapping electrode (the
by a pulse applied to a transmission line; Zo = L/C
transfer gate) deposited on, but insulated from,
(approximately), where L and C are the induc-
the other electrodes. An input signal stores a
tance and capacitance, in microhenrys and mi-
charge in the capacitor formed by the source elec-
crofarads, per unit length of the line. Also called
trode and chip. A subsequent trigger signal ap-
plied to the transfer gate transfers the charge to
surge protector Misnomer for SURGE SUPPRES-
the receiver electrode, where it becomes an out-
put signal (often amplified, with respect to the in-
surge suppressor A semiconductor device used to
put signal).
absorb potentially destructive transients or over-
surface effect An effect (such as current, resis-
voltages on a utility power line. It has a three-wire
tance, or resistivity) observed on the surface of a
cord for plugging into a 117-volt outlet, a power
sample of material, rather than throughout the
switch, and several three-wire outlets for connec-
body of the material. Compare BULK EFFECT.
tion to sensitive electronic equipment (such as
surface insulation A coating applied to the sur-
personal computers, videocassette recorders,
faces of core laminations to prevent the passage
television sets, hi-fi amplifiers, etc.).
of currents between laminations.
surround See SUSPENSION, 1.
surface leakage Leakage of current over the sur-
Surround Sound The trade name for a multichan-
face of a dielectric material, as opposed to leakage
nel sound system for use with television receivers
through the interior of the material.
and videocassette players. Some televised movies,
surface noise See NEEDLE SCRATCH.
especially on cable and satellite networks, deliver
surface recombination rate For a semiconductor,
multichannel sound through receiving/recording
the rate at which electrons and holes recombine
systems equipped with special decoders.
at the surface. Compare VOLUME RECOMBINA-
surveillance 1. A method of monitoring a specific
area or volume for intrusion or other disturbance.
surface resistivity The resistance of a unit area of
2. A means of monitoring a specified portion of
a material, measured between opposite edges.
the electromagnetic spectrum for unauthorized
surveillance radar An air-traffic-control radar that
surface tension The tendency of the surface of a
supplies continuous information regarding the
liquid to “shrink.” This property varies with dif-
azimuth and distance of aircraft inside a selected
ferent liquids and is caused by a net molecular
radius around an airport.
force directed inward from the surface.
666 susceptance • swing

susceptance Symbol, B. Unit, siemens. The reac- which the carrier frequency is increased and de-
tive component of admittance, as distinguished creased by a sweep-signal generator. 3. In an os-
from conductance. cilloscope, the number of times that the trace
susceptibility The capacity of a substance to be- moves across the screen in one second. It is equal
come magnetized, expressed as the ratio of mag- to the reciprocal of the SWEEP PERIOD.
netization to the strength of the magnetizing sweep generator 1. A device that causes the elec-
force. tron beam in a cathode-ray tube to scan at a
suspension 1. In a speaker, the flexible, circular or known speed. 2. An oscillator that generates a
elliptical structure via which the cone is attached signal that rapidly varies in frequency. It is used
to the frame. 2. The wire or metallized fiber for the testing and adjustment of bandpass filters
supporting the movable coil of a galvanometer. and other selective circuits.
3. Particles of a substance and the liquid in which sweeping receiver See SCANNING RECEIVER.
it is mixed, but not dissolved. 4. The substance, sweep magnification In an oscilloscope, increas-
as defined in 3. ing or multiplying the sweep frequency, thus re-
suspension galvanometer A meter with a light- ducing the time per horizontal division. This
beam apparatus for lengthening the arc through increases the maximum frequency of waveforms
which the pointer travels. When the beam of light that can be analyzed, and allows closer inspec-
is cast a long distance, a tiny movement of the tion of high-frequency signal components.

coil will cause considerable movement of the im- sweep magnifier In an oscilloscope, a circuit for
age. achieving sweep magnification.

sustained oscillations Oscillations that continue sweep oscillator See SWEEP GENERATOR.
as long as power is supplied to the oscillation sweep period The duration, in seconds, of one
generator. Also see CONTINUOUS WAVE. Com- complete cycle of sweep signal in an oscilloscope.
pare DAMPED OSCILLATIONS. It is equal to the reciprocal of the SWEEP FRE-
sustaining voltage The voltage at which second- QUENCY.
collector breakdown occurs in a transistor (see sweep signal The (usually linear, sawtooth) signal
SECOND BREAKDOWN). used to sweep the beam of an oscilloscope tube.
S video In animation, a scheme that separates Also see SWEEP, 1, 2.
brightness and color. It can enhance the video in sweep-signal generator A signal generator that

some applications. supplies a signal whose frequency varies automat-
SW Abbreviation of SHORTWAVE. ically and periodically throughout a given band.
sw Abbreviation of SWITCH. (Also, S or s.)
swamping resistor 1. A noninductive resistor con-
nected in parallel with the input circuit of a class-
B linear amplifier for automatic regulation of the fmax
excitation. 2. A resistor connected in series with

the emitter of a bipolar transistor to minimize the
effects of temperature-induced variations in junc-
tion resistance.
swarf The string of material that threads off a disc
during sound recording.
SW band A section of the S BAND, extending from
3400 to 3700 MHz.
sweep 1. To deflect the electron beam in a cathode- Time
ray tube, usually horizontally, to provide a time
base. 2. The circuit for achieving the particular sweep-signal generator
deflection described in 1.
sweep circuit A circuit, such as a deflection gener-
ator (e.g., a sawtooth oscillator), for producing a sweep test A method of testing the attenuation-
sweep signal. Also see SWEEP. vs.-frequency characteristics of a selective cir-
sweep delay In an oscilloscope, the process of ini- cuit, using a radio-frequency sweep generator.
tiating the sweep of the electron beam at some se- sweep time The actual time required for a single
lected instant after the signal has started. sweep by a deflecting signal; t = 1/f, where t is
sweep-delay circuit In an oscilloscope or radar, sweep time in seconds, and f is sweep frequency
the circuit for delaying the sweep until the start of in hertz.
the signal. Also see DELAYED SWEEP. sweep voltage The peak voltage amplitude of the
sweeper 1. See SWEEP GENERATOR. 2. See sweep signal.
SWEEP-SIGNAL GENERATOR. SWG Abbreviation of standard wire gauge.
sweep frequency 1. The frequency at which the swing The maximum change exhibited by a varying
electron beam in a cathode-ray tube is deflected quantity (e.g., amplitude swing and frequency
along the reference axis. 2. The frequency at swing).

swinging choke • symmetrical conductivity

swinging choke A filter choke that exhibits rela- switching voltage The largest voltage that a
tively high inductance when low current flows switching device can handle without malfunc-
through it, and lower inductance when high cur- tioning.
rent flows through it. This inductance, which switch leakage current 1. The current flowing
swings under conditions of varying load current, through a switching device when it is supposed to
permits the use of a high-resistance bleeder re- be nonconducting. 2. In a switching transistor,
sistor. Compare SMOOTHING CHOKE. for a given voltage, the leakage current between
Swiss-cheese packaging A method of packaging the emitter and collector when the device is sup-
an electronic circuit, in which components are in- posed to be nonconducting.
serted into the assembly through holes drilled or SWL Abbreviation of SHORTWAVE LISTENER.
punched in parallel, stacked printed-circuit SWR Abbreviation of STANDING-WAVE RATI0.
boards. SWR bridge A four-arm resistance bridge for mea-
switch 1. A circuit or device (electronic, electrome- suring voltage standing-wave ratio. This radio-
chanical, or mechanical) for opening and closing frequency bridge has noninductive resistors in
a circuit or for connecting a line to one of several three of its arms and the device under test in the
different lines (e.g., rotary selector switch). 2. To fourth arm. The bridge is balanced first with an
change the logic state of a circuit or device. 3. In equivalent noninductive resistor that replaces
a computer program, a branch instruction direct- the device, and the output voltage is noted. Then
ing the program to a line number dependent on the device is substituted for the test resistor, and
the value of a variable or result (e.g., BASIC™s the change in voltage is noted. The standing-wave
GOTO). 4. To cause an electrical circuit to change ratio is determined from the voltage ratio.
state, as from low to high or vice versa. SWR meter See SWR BRIDGE.
switch current 1. The current flowing through a SY band A section of the S BAND, extending from
switch. 2. The current flowing through a switch- 2600 to 2700 MHz.
ing diode or transistor. 3. The minimum current syllable compandor A device that compresses or
necessary to produce switching of a transistor, expands the amplitude of an audio signal. The
specified in milliamperes or microamperes. time constant is fast enough to allow response to
switchgear Collectively, devices and systems for individual syllables. Compression is generally
making and breaking circuits”either automati- used at the transmitting station, and expansion
cally or manually. at the receiving station.
switchhook In a telephone set, the spring-and- sym 1. Abbreviation of symmetrical. 2. Abbrevia-
switch device that engages the line when the re- tion of SYMBOL.
ceiver is lifted. symbol 1. A letter or graphic device representing a
switching characteristics Technical data describ- quantity or term [e.g., I (current), f (frequency),
ing the performance and capabilities of switching etc.]. 2. A conventional device denoting a mathe-
devices and circuits. matical operation (e.g., +, /). 3. In a circuit
switching circuit An on-off type of circuit contain- diagram, a pictorial device representing a
ing electronic or mechanical switches. component.
switching diode See COMPUTER DIODE. symbolic address An address in a source-
switching frequency The frequency at which a language computer program (i.e., the arbitrary
repetitive switch operates. Also see SWITCHING label used by the programmer).
RATE. symbolic language See SOURCE LANGUAGE.
switching mode Operation in which a device, such symbolic logic A system for representing logical
as a transistor or diode functions as a binary dig- relationships, such as those acted upon by com-
ital device, rather than as an analog device. The puter and switching circuits, by means of sym-
current is generally either zero (cutoff or pinchoff) bols that are usually nonnumerical. Also see
or some value that depends on the bias and on BOOLEAN ALGEBRA.
the applied voltage. symmetrical circuit A circuit having identical
switching rate The rate (e.g., closures per second) configurations on each side of a dividing line,
at which a repetitive switch operates. Also see such as the ground bus. A push-pull circuit is an
switching speed The time required for a switch to symmetrical communications 1. Two-way com-
open or close or for a switching device to change munications in which the volume of transmitted
states (as from cutoff to saturation). Also see data is the same, or nearly the same, in both di-
SWITCHING TIME. rections. 2. Two-way communications in which
switching time The time required, after the appli- the speed of transmitted data is the same, or
cation of a pulse, for an electronic switch to nearly the same, in both directions. Compare
switching transistor A transistor designed espe- symmetrical conductivity Identical conductivity
cially for on-off operation. Such units exhibit for both positive and negative electricity. Com-
short recovery time and low capacitance. pare ASYMMETRICAL CONDUCTIVITY.
668 symmetrical FET • synchronous clock

symmetrical field-effect transistor A field-effect
transistor whose source and drain terminals can
be interchanged without affecting circuit opera-
SISTOR. Signal
symmetrical input See BALANCED INPUT.
RF amp. comparator
symmetrical output See BALANCED OUTPUT.
symmetrical transistor See BIDIRECTIONAL
symmetrical wave A wave whose positive and neg-
ative half-cycles are identical in shape and peak Signal
symmetry 1. The condition of having the same
shape on each side of an axis. 2. The condition of Voltage-
conducting positive and negative currents equally controlled
well. 3. The condition in which a circuit is identi- oscillator
cal on both sides of a reference line, such as the
ground line.
sympathetic vibration Resonant vibration of one
body in response to the vibration of another body.
sync 1. Contraction of SYNCHRONIZATION.
2. Contraction of SYNCHRONISM.
sync amplifier In a television circuit, the amplifier
AF amp.
used to increase the amplitude of the sync pulses
after they are separated from the composite video
sync generator A circuit that produces the syn-
chronization pulses in a television transmitter. synchrodyne receiver
synchro A dynamo-electric-control device that,
when connected to a similar device and the alter-
nating-current power line, permits remote control. synchronization The coincidence of one process
Thus, when the rotor of one synchro is turned to a or operation with another, as in the synchroniza-
certain position, the rotor of the other assumes the tion of an oscillator frequency by means of an ap-
same position. Also see AUTOSYN and SELSYN. plied standard-frequency voltage, in which case
synchrocyclotron A type of cyclotron in which the the oscillator frequency becomes that of the stan-
variation in mass, because of increased velocity, dard signal.
of the charged particles is compensated, resulting synchronized clamping A type of clamping in
in higher energy for the particles. which an output voltage is maintained at a pre-
synchro differential A synchro that receives two determined fixed value until a synchronizing
input signals and delivers a single output signal. pulse is applied, whereupon the output follows
The inputs can be two electrical signals, or one the input.
electrical signal and one mechanical signal. synchronized multivibrator See DRIVEN MULTI-
synchrodyne receiver A direct-conversion re- VIBRATOR.
ceiver in which the local oscillator frequency or synchronizer A computer storage device used be-
phase is locked into synchronism with the incom- tween two devices transmitting data at different
ing signal carrier frequency or phase. speeds, to counteract this differential (as a
synchroflash A flash that is synchronized with the buffer).
shutter of a camera. synchronizing signal A signal used to synchronize
synchro generator The transmitting member of a another signal, usually in frequency.
synchro system. synchronous The condition of operating in step
synchro motor The receiving member of a synchro (phase) with some reference signal.
system. synchronous clock 1. An alternating-current
synchronism 1. The condition of being in step, as clock driven by a synchronous motor. Although
when two motors are running in synchronism 60-Hz models are common, such clocks are not
with each other and the power frequency, or restricted to low-frequency ac operation; 1-kHz
when two relays open and close in step. 2. The types, for example, are used in some primary
condition of being in phase, as when two pulses frequency standards. 2. The timing source in a
occur simultaneously. synchronous computer.
synchronous computer • synthesizer

synchronous computer A computer whose opera-
tions are timed by single-frequency clock signals.
synchronous contacts The rectifying contacts of a
synchronous vibrator (see VIBRATOR-TYPE REC-
synchronous converter A synchronous machine
that can run on alternating current and generate
direct current, or vice versa. Also called ROTARY
synchronous gate A gate whose output is syn-
chronized, according to the input signal.
synchronous generator An alternator operating in
synchronism with one or more other alternators.
synchronous induction motor An alternating-
current motor that is intermediate between the
fractional-horsepower reluctance motor and the
multiple-horsepower three-phase, synchronous
motor. The synchronous induction machine Collector
starts like an induction motor and runs like a Circular
synchronous motor. accelerating
synchronous inputs In a computer flip-flop, in- chamber
puts that accept pulses only at the command of
the clock. synchrotron
synchronous machine See SYNCHRONOUS IN-
synchronous motor See SYNCHRONOUS INDUC- frequency magnetic field to impart very high
TION MOTOR. velocity to the particles.
synchronous network A communications network sync pulse 1. A pulse used to control the fre-
in which all clocks are set so that they run at the quency or repetition rate of an oscillator or other
same rate, their increments are identical in dura- generator. 2. In a television system, a pulse
tion, and transitions occur simultaneously or transmitted as part of the composite video signal
with a specified phase difference. Such a system to control scanning. Also see HORIZONTAL SYNC
allows for greatly enhanced signal-to-noise ratio PULSE and VERTICAL SYNC PULSE.
for a given amount of transmitter power, and also sync separator In a television receiver circuit, a
reduces the bandwidth necessary for a single sig- stage used to separate and deliver the sync
nal so that many more signals can be placed in a pulses from the composite video signal. See, for
given frequency band. example, DIODE SYNC SEPARATOR.
synchronous orbit See GEOSTATIONARY ORBIT. sync signal See SYNCHRONIZING SIGNAL.
synchronous satellite See GEOSTATIONARY sync takeoff The point in the video amplifier cir-
SATELLITE. cuit of a television receiver at which the compos-
synchronous speed For an alternating-current ite video signal is sampled to extract the sync
(ac) machine, the speed corresponding to the ac pulses.
frequency. syntax 1. The rules by which computer program
synchronous transmission A method of signal statements are structured. 2. The way that a
transmission in which individual symbols are written or spoken sentence is constructed. It is
sent at a specified rate, according to a clock that important in speech recognition and speech syn-
also governs the receiver. thesis.
synchronous vibrator See VIBRATOR-TYPE REC- synthesis The rigorous (usually mathematical) de-
TIFIER. sign of an electronic circuit or device and the ac-
synchroscope 1. An oscilloscope having a high- curate prediction of its performance. Compare
speed sweep triggered by a synchronizing signal. ANALYSIS.
Such an instrument is valuable for viewing high- synthesizer 1. See SIGNAL SYNTHESIZER. 2. A
speed pulses. 2. A pointer-type instrument used circuit synthesizer (i.e., a device that allows a
to indicate the synchronism between two power wide variety of circuits to be set up temporarily or
alternators. simulated, for testing and evaluating). Some-
synchro system A circuit or system using syn- times, a specially programmed computer serves
chros for the transmission and reception of posi- this purpose. 3. A keyboard on which music can
tioning signals. Also see SYNCHRO. be played, and whose output can be adjusted to
synchrotron A particle accelerator that uses a simulate the sounds of various musical instru-
high-frequency electrostatic field and a low- ments. 4. See MOOG SYNTHESIZER.
670 synthetic bass • SZ band

synthetic bass An apparent accentuation of bass system of units A set of fundamental units for
notes resulting from intermodulation distortion defining the magnitudes of all physical variables.
in an amplifier. The most common system of units is the stan-
synthetic crystal An artificially produced crystal, dard international (SI) system.
such as synthetic quartz. systems analysis In computer system operation,
synthetic resin An artificially produced resin. Also analyzing the way something is done and devising
see THERMOPLASTIC MATERIAL and THER- a better alternative by isolating the problem area,
MOSETTING MATERIAL. scrutinizing the system as it stands, studying
syntony See RESONANCE. what is thereby disclosed, devising the alternate
syst Abbreviation of SYSTEM. application of software and/or hardware, dissemi-
system 1. An integrated assemblage of hardware nating the revised operational procedure, and
and/or software elements operating together to overseeing the implementation of the new method.
accomplish a prescribed end purpose (e.g., servo systems engineering The branch of engineering
system, operating system, and communications devoted to the design, development, and applica-
system). 2. A methodology incorporating fixed tion of complete systems. The approach takes
and ordered procedures for accomplishing an end into consideration all elements in a system or
purpose. 3. A self-contained computer worksta- process and their integration.
tion. systems flowchart A flowchart showing the inter-
systematic error See CUMULATIVE ERROR. relationship of activities in a system.
system engineering See SYSTEMS ENGINEER- SZ band A section of the S BAND, extending from
ING. 3900 to 4200 MHz.
T 1. Symbol for TRANSFORMER. 2. Abbreviation of tabulator See TAB.
prefix TERA-. 3. Symbol for thermodynamic tem- tacan A pulse-type UHF air navigation system in
perature. 4. Symbol for TRITIUM. 5. Abbreviation which a station is interrogated by signals from an
of TON. (Also, t and tn.) 6. Abbreviation of TESLA. aircraft to provide bearing and range information.
7. Symbol for KINETIC ENERGY. 8. Symbol for The name is an acronym for tactical air naviga-
PERIOD. 9. Symbol for true. tion.
t 1. Symbol for TIME. 2. Abbreviation of TON. tach Abbreviated form of tachometer.
(Also, T and tn.) 3. Symbol for CELSIUS TEM- tachometer See ELECTRONIC TACHOMETER.
PERATURE. (Also, T.) 4. Abbreviation of TARGET. tachometer generator A small, dynamo-type elec-
5. Abbreviation of technical. 6. Abbreviation of tric generator that delivers a voltage proportional
TENSION. to the rotational speed of a shaft to which it is at-
Ta Symbol for TANTALUM. tached.
tab On the keyboard for a computer, typewriter, tachyon A high-speed subatomic particle thought
terminal, or word-processing system, a key that to move faster than the speed of light.
moves the cursor a specified number of spaces tactical air navigation See TACAN.
toward the right. It also performs various other tactical radar A radar system used in military op-
functions in menu-driven or graphical computer erations.
interfaces. tactile sensor A device that provides an intelligent
table In an internal or external computer memory, machine with a sense of “touch”: temperature,
an array (i.e., a list or matrix) of data that can pressure, force, texture, and torque. It is impor-
be recalled using keys (e.g., single- or double- tant in robotics, and also in some computer ap-
subscripted variables). plications, such as virtual reality (VR).
table look-at Abbreviation, TLA. In computer oper- T-adapter See TEE-JUNCTION.
ations, finding the position of a data item in a tag 1. In data-processing and computer opera-
table by implementing an algorithm. tions, the identification of digits or characters
table look-up Abbreviation, TLU. In computer op- forming part of a record. 2. An encoded price tag
erations, locating items in a table by inspecting (i.e., a passive transponder or barcode strip). It is
what is in the table, key by key. commonly used in retail stores.
tabulate In data processing, to combine the totals tag converter A device that senses the information
for data item groups having the same key. on tags (see TAG, 2) and transfers it to a com-
tabulation 1. The printout of what has been tabu- puter system.
lated (see TABULATE). 2. The computer-program- tail 1. The decay of a waveform from maximum
directed movement of the cursor on a amplitude to zero amplitude. 2. Any pulse that
cathode-ray-tube display, or of a typewriter car- follows a main pulse as a result of the main
riage, to certain positions in a line. pulse.

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672 taillight monitor • tap changer

amplifier. 2. A circuit in which is stored electrical
energy of frequencies in a range whose midpoint
is resonance for the circuit. 3. See MERCURY

tantalum Symbol, Ta. A metallic element of the
vanadium family. Atomic number, 73. Atomic
weight, 180.95. Tantalum is used in the elements
of some electron tubes and in some electrolytic
tantalum capacitor A type of electrolytic capacitor
that uses tantalum rather than aluminum. The
tantalum can be foil, as is the aluminum in a con-
ventional electrolytic capacitor. It might also take
the form of a porous pellet, the irregular surface
of which provides a large area in a small volume.
An extremely thin oxide layer forms on the tanta-
lum. These capacitors have high reliability and
taillight monitor An electronic device for warning
excellent efficiency, and are used in military ap-
a motorist of taillight failure.
plications because they have a low failure rate.
tail pulse 1. A pulse with a fast rise time, but a
They can be used in audio and digital circuits in
slow decay time. 2. See TAIL, 2.
place of aluminum electrolytic capacitors. The
takedown In computer operations, the process of


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