. 35
( 42)


single-phase full-wave Pertaining to a rectifier op- tenuated or canceled out, leaving only one
erated from a single-phase alternating-current (ac) sideband. The carrier is generally suppressed also.
power line, and rectifying both half-cycles of ac single-sideband suppressed-carrier Abbreviation,
voltage. Compare SINGLE-PHASE/HALF WAVE. SSSC or SSBSC. Pertaining to a system of modula-
single-phase/full-wave bridge A bridge rectifier tion in which the carrier and one sideband from an
operated from a single-phase alternating-current amplitude-modulated signal are suppressed; only
supply, usually from the untapped secondary the remaining sideband is transmitted. Sometimes
winding of a transformer. Compare SINGLE- this mode is simply called SINGLE SIDEBAND.
PHASE/FULL-WAVE CIRCUIT and SINGLE- single signal Pertaining to a mode of reception in
PHASE/HALF-WAVE CIRCUIT. which signals appear on only one side of zero
single-phase/full-wave circuit A rectifier circuit beat, enhancing selectivity and reducing interfer-
in which each half-cycle of single-phase alternat- ence among received signals. Most superhet-
ing current is rectified by a separate diode sup- erodyne receivers have this feature; most
plied from the ends of a center-tapped winding of direct-conversion receivers do not.
a transformer. Compare SINGLE-PHASE/FULL- single-signal receiver A superheterodyne receiver
WAVE BRIDGE and SINGLE-PHASE/HALF- that achieves high selectivity via a selective filter
WAVE CIRCUIT. in the intermediate-frequency amplifier chain.
single-phase/half-wave Pertaining to a rectifier Signals appear on only one side of zero beat, in a
operated from a single-phase alternating-current band whose width can be adjusted or selected for
(ac) power line, and rectifying only one half-cycle various values from about 200 Hz to 3 kHz.
of ac voltage. single silk-covered wire Wire insulated with one
single-phase/half-wave circuit A rectifier circuit layer of silk.
in which a diode, output load, and single-phase single-skip propagation See SINGLE-HOP PROP-
alternating-current supply are connected in se- AGATION.
ries, only one half-cycle of the cycle being passed single-step operation See STEP-THROUGH OP-
by the diode. Compare SINGLE-PHASE/ ERATION.
FULL-WAVE CIRCUIT and SINGLE-PHASE/ single sweep In an oscilloscope, a single time-axis
FULL-WAVE BRIDGE. deflection of the electron beam. Also see SWEEP,
single-phase rectifier See SINGLE-PHASE/ 1, 2. Compare RECURRENT SWEEP.
FULL-WAVE BRIDGE, SINGLE-PHASE/FULL- single-sweep blocking oscillator A blocking oscil-
WAVE CIRCUIT, and SINGLE-PHASE/HALF- lator that cuts off after generating a single cycle
WAVE CIRCUIT. or pulse.
single-point ground One ground connection to single-throw switch A single-action switch with
which all channels of a circuit are returned. Such two or more poles.
a common connection eliminates or greatly mini- single-tone keying Modulated continuous-wave
mizes the common coupling often encountered keying. A single audio-frequency tone is used to
when separate ground points are used. amplitude-modulate or frequency-modulate the
single-pole double-throw Abbreviation, SPDT. De- carrier.
scriptive of an electrical, electronic, or mechani- single-track recorder A recorder, such as a mag-
cal switch with a pole that can be connected to netic-tape recorder or a graphic recorder, that
either of two adjacent poles, but not to both. permits recording along only one track.
634 single-trip multivibrator • skin depth

single-trip multivibrator See MONOSTABLE SJD Abbreviation of SILICON JUNCTION DIODE.
MULTIVIBRATOR. skating In a phonograph turntable, the tendency
single-tuned circuit A circuit tuned by varying of the tone arm to swing toward the spindle dur-
only one of its components [e.g., an intermediate- ing record play, independent of the action pro-
frequency transformer in which only the sec- duced by the stylus following the groove.
ondary coil (rather than both primary and skeletal code A generalized computer routine
secondary) is tuned]. needing only certain parameters to be usable for
single-turn coil 1. A coil consisting of a single turn a specific application.
of wire, tubing, or strip. 2. See RING INDUCTOR. skeleton bridge A bridge consisting of an ad-
3. See SHADING COIL. justable arm (potentiometer) and a pair of binding
single-turn potentiometer A potentiometer that posts for each of the other three arms. Suitable
can be adjusted through its entire resistance resistors, capacitors, or inductors are connected
range by no more than one full rotation of the to the binding posts to set up the bridge circuit
shaft. Usually, the turning range is somewhat desired.
less than a full circle (e.g., 300 degrees).
single-wire-fed antenna See WINDOM ANTENNA.
single-wire line 1. See SINGLE-WIRE TRANSMIS-
SION LINE. 2. A single wire used for communica-
tion or control purposes. The earth furnishes the
return path.
single-wire transmission line An antenna trans-
mission line or feeder consisting of one wire only
(see, for example, WINDOM ANTENNA).
sink 1. A device or circuit into which current
drains. 2. See HEATSINK.
sink circuit The circuit associated with a load or
other sink. Compare SOURCE CIRCUIT, 2.
sinker A piece of semiconductor material used to
reduce the base-collector junction resistance in a
bipolar transistor. Gen
sintering A process in which various solid bodies
are formed from fusible powders at temperatures skeleton bridge
below their melting points. Example: sintered
magnetic core.
sinusoidal Having the shape and properties of a skeleton-type assembly 1. A method of elec-
SINE WAVE. tronic-equipment construction in which a mini-
SIO Abbreviation of serial input/output. mum of supporting members is used. An example
SIP Abbreviation of SINGLE-INLINE PACKAGE. is the use of an open framework, instead of a
six-phase rectifier A polyphase rectifier circuit chassis, to support components. 2. An assembly
operated from a three-phase supply. The output of electronic equipment, consisting essentially of
ripple frequency is six times the supply fre- a foundation unit (containing the basic circuitry)
quency. and plug-in units for setting up various complete
skew 1. A condition resulting from failure of the
horizontal synchronization in facsimile or televi-
sion. The picture appears distorted, and appears
as a non-rectangular parallelogram. 2. In a print
Primaries display, nonalignment of columns resulting from
an incorrect number of line spaces in each line.
3. In a probability function, an accumulation of
values toward either side of center.
Secondaries Load
skewing 1. The bending of a curve away from its
normal shape. 2. In a differential amplifier, the
offset between two signals. Also see OFFSET.
Skiatron A special form of cathode-ray tube, with
the fluorescent coating replaced by a screen of
halide crystals that darken, instead of glow, when
exposed to the electron stream.
skin depth The depth to which current penetrates
below the surface of a conductor, as a result of
six-phase rectifier the SKIN EFFECT.
skin effect • slider

skin effect The tendency of high-frequency alter- Weak
First Strong
nating current to travel along the surface of a magnet
anode magnet
conductor; the high-frequency reactance is lower
along the outside than at the center of a conduc-
tor. This tends to increase the resistivity of solid
conductors at high alternating-current frequen-
cies, as compared with low frequencies and direct
skip 1. Ionosphere-reflected radio transmissions.
2. In a computer program, an instruction whose
sole function is that of causing a jump to the next
instruction. Control grid Ion beam
skip distance For a signal propagated via the iono-
sphere, the distance from the transmitter to the slashed-field-gun CRT
point at which the returned skywave strikes the
skip fading For a signal propagated via the iono- slanted, the electrostatic field is diagonal, caus-
sphere, changes in signal strength caused by ing the electron and ion beams to be diverted at
fluctuations in the altitude and/or contour of the an angle.
ionized layer(s). slave flash A photoflash operated by the light flash
skip zone See ZONE OF SILENCE. from another such unit.
skirt selectivity 1. The bandwidth between points slave relay A relay operated by, and whose action
of high attenuation (usually 30 dB or 60 dB) on follows, a MASTER RELAY.
the selectivity curve in a communications re- SLC Abbreviation of STRAIGHT-LINE CAPACI-
ceiver. 2. The relative steepness of the attenua- TANCE.
tion-vs.-frequency curve in a communications sleeping sickness A gradual increase in transistor
receiver. leakage current.
SKM Abbreviation of sine-cosine multiplier. sleep machine An electronic device sometimes
skyhook 1. Colloquialism for ANTENNA. 2. A wire used as an aid for relaxation or sleeping. It con-
antenna supported by a captive balloon or kite. sists of a wideband audio-frequency noise gener-
sky noise Radio noise originating in outer space. ator that produces low-level sounds similar to the
skywave A radio wave propagated by ionospheric noise of waves on a beach or a light wind through
reflections and/or refractions. Compare trees.
GROUND WAVE. sleeve antenna A vertical antenna in which the
upper half is a quarter-wave rod connected to the
inner conductor of a coaxial feeder, and the lower
Ionized layer half is a quarter-wave metal sleeve connected to
the outer conductor of the feeder. Also called
sleeving A material in tubular form that can be
slipped over another material [e.g., insulating
sleeving for wires (spaghetti)].
slew rate In an operational amplifier, the rate at
which the output can be driven between its lim-
Earth its.
Xmtr Rcvr
SLF Abbreviation of STRAIGHT-LINE FRE-
slice A semiconductor wafer cut from a single-
crystal ingot.
skywave correction A factor applied to long-range
slide-back meter An electronic voltmeter in which
radionavigation signals to account for the time
an unknown alternating-current signal voltage
delay resulting from ionospheric propagation.
applied to the input of an amplifier stage is
bucked by an internal, adjustable, accurately
slab 1. A relatively thick body of quartz, ceramic,
known signal voltage. The internal voltage is ad-
semiconductor, or dielectric. 2. See SUBSTRATE.
justed until a null occurs, indicating that its mag-
slap back The return of sounds by an acoustically
nitude is equal to that of the unknown voltage.
reflective object or surface a short distance away,
slider A flat-spring contact that slides along the
resulting in almost immediate echoes.
turns of a resistance or inductance coil to vary
slashed-field-gun CRT A straight-gun television
the coil™s resistance or inductance. Also called a
picture tube (see STRAIGHT-GUN CRT). Because
the gap between the anodes in this tube is
636 slide-rule dial • slotted line

slide-rule dial A dial mechanism having a straight slope detector An amplitude-modulation (AM) re-
scale that resembles a slide rule. ceiving circuit detuned to one side of resonance
slide switch A switch actuated by sliding a block- (i.e., to a point along the skirt of the selectivity
shaped button. Compare BAT-HANDLE SWITCH, curve) to detect a frequency-modulated (FM) sig-
PADDLE SWITCH, and ROCKER SWITCH. nal. The FM swing occurs along the slope of the
resonance curve. Slope detection is useful in nar-
rowband FM when conventional FM circuitry is
not available.


slide switch

slide wire A simple potentiometer consisting of a

single, straight piece of resistance wire with a
sliding contact. Also see SLIDE-WIRE RESISTOR.
slide-wire bridge A simple four-arm bridge in
which the adjustable element is a single, straight
resistance wire along which a clip or slider is
moved, and that supplies two arms of the bridge
(one on each side of the slider).
slide-wire resistor A variable resistor consisting of
a single wire (straight or coiled) along whose

length a slider is moved to vary the resistance.
sliding contact A contact that mates with another
contact, or moves along a contacted surface, with
a sliding motion. Also called SELF-CLEANING slope resistance The ratio of a small change in
CONTACT and WIPING CONTACT. voltage to a small change in current at an elec-
slip 1. In an eddy-current brake, coupling, or trode or in a component.
drive, the difference in speed between the field slop-jar capacitor See WATER CAPACITOR.
magnets and the iron eddy-current ring. 2. In a slop-jar rectifier See ELECTROLYTIC RECTIFIER.
synchronous motor, the difference between rotor slot 1. In the armature of a motor or generator, a
speed and stator speed. groove in which the windings are laid. 2. The
slip clutch In a gear or rack-and-pinion drive sys- notch in the response curve of a crystal filter.
tem, a device that releases the load if the torque slot antenna A microwave antenna that radiates
becomes excessive. The gears then slip instead of energy through a slot cut in a surface, such as
being damaged. the metal skin of an aircraft.
slip ring See COLLECTOR RING, 1. slot cell A reinforcing, dielectric material (such as
slip speed See SLIP, 2. plastic) placed in the slot of a ferromagnetic core.
slope 1. The slant of a line (graph) in rectangular slot coupling Coupling microwave energy between
coordinates, depicted as the ratio of the change in a waveguide and a coaxial cable by means of two
the dependent variable y to the change in the in- slots, one in the waveguide and the other in the
dependent variable x. If (x1,y1) and (x2,y2) are two outer conductor of the cable.
points on the line, then slope m is determined by slot-discharge resistance See CORONA RESIS-
m = (y2 “ y1)/(x2 “ x1). 2. The slant of a line in rect- TANCE.
angular coordinates as defined in 1, when the slot insulation 1. Insulation of wires in the slots of
line is tangent to a curve (graph) at a specified the armature of a motor or generator (see SLOT,
point. 3. The skirt(s) of a selectivity curve, partic- 1). 2. A material in the form of tape or sheets,
ularly in a communications receiver, where a used for the purpose defined in 1.
small change in frequency results in a significant slot radiator See SLOT ANTENNA.
change in gain or attenuation. 4. The ratio of the slotted line A device consisting of a section
extent of change in a quantity to the extent of of air-dielectric coaxial line arranged for mi-
change in some other quantity, when a causal re- crowave measurements. The outer conductor is
lation exists between the magnitudes of the a metal cylinder, and the inner conductor is a
quantities. Example: See SLOPE RESISTANCE. concentric metal rod. The cylinder is provided

slotted line • small signal

with a lengthwise slot through which a small slow time scale An extended time scale, i.e., one
pickup probe extends for sampling the electro- larger than the time unit of the system under
magnetic field inside the device. The probe is consideration.
attached to a carriage that slides along a SLS Abbreviation of SIDELOBE SUPPRESSION.
graduated scale on the outside of the cylinder. slug 1. A movable core of ferromagnetic material,
Radio-frequency energy is injected into one end used to tune (varying the inductance of) coil by
of the line through a coaxial cable; as the probe changing its position along the axis of the coil.
moves along, response points are indicated by Also see SLUG-TUNED COIL. 2. A copper ring at-
an external detector connected to the probe. The tached to the core of a relay for time-delay pur-
scale is read at these points to determine fre- poses (see SLUG-TYPE DELAY RELAY).
quency, standing-wave ratio, impedance, and slug-tuned coil A coil whose inductance is varied
power. An alternate form of slotted line uses a by means of a ferromagnetic slug that slides in
section of slotted waveguide, instead of a sec- and out of the coil.
tion of coaxial line. slug tuner A tuner for a radio or television receiver
slotted rotor See SERRATED ROTOR PLATE. or test instrument, using slug-tuned coils.
slotted section See SLOTTED LINE. slug-type delay relay A delayed-response relay that
slotted waveguide See SLOTTED LINE. achieves time delay through the action of a heavy
slot width 1. The width of a slot in the armature of copper slug on the core. The slug forms a low-
a motor or generator (see SLOT, 1). 2. The band- resistance, short-circuited single turn in which a
width of the notch in the response curve of a current is induced by the magnetic flux, resulting
band-suppression filter of any kind. See, for ex- from energizing the relay. The resulting flux of the
ample, NOTCH FILTER. slug opposes the buildup of relay-coil flux.
slow-acting relay Any relay designed to operate at slumber switch An alarm-reset switch on an elec-
some finite period following the application of the tronic clock radio. If the alarm activates, the
actuation voltage. slumber switch (usually a pushbutton device)
slow-blow fuse A fuse in which the melting wire can be pressed to turn off the alarm for a prede-
breaks apart slowly. The time delay allows the termined length of time. Also called snooze but-
fuse to withstand momentary current surges that ton.
do not damage the protected equipment, but that SLW Abbreviation of STRAIGHT-LINE WAVE-
would cause a fast-blow fuse to break the circuit LENGTH.
needlessly. Sm Symbol for SAMARIUM.
slow-break, fast-make relay A relay that opens small-current amplifier 1. A direct-current (dc)
slowly and closes rapidly. amplifier for low-level input currents (i.e., cur-
slow-break, slow-make relay A relay that opens rents of 1 milliampere or less). 2. An amplifier
slowly and closes slowly. (such as a silicon-transistor unit) requiring very
slow charge Storage-battery charging in which a low dc operating current.
low current is passed through the battery over a small-scale frequency response For an analog
long period of time. It ensures that the rated circuit, the output frequency at which the level is
ampere-hour capacity will be restored to the “3 dB, relative to the maximum level, with a small
battery. signal at the input, normally 1 volt peak-to-peak.
slow death 1. The gradual deterioration of transis- small loop antenna A closed loop antenna with
tor performance. 2. The gradual deterioration in one to several turns and a circumference less
the performance of a component, circuit, device, than 0.1 wavelength at the highest operating fre-
or system. quency. This antenna is suitable for wireless re-
slow drift The gradual change of a quantity or set- ception, but generally not for transmission
ting (usually in one direction). Compare FAST because the radiation resistance is extremely low.
DRIFT. The antenna is least responsive along its axis,
slow-make, fast-break relay A relay that closes and is most responsive in the plane defined by its
slowly and opens rapidly. turn(s). The null along the axis is sharp and deep.
slow-make, slow-break relay A relay that closes A capacitor can be connected in series or parallel
slowly and opens slowly. with the loop to provide a resonant response. This
slow-operate, fast-release relay See SLOW- type of antenna can reduce interference caused
MAKE-FAST-BREAK RELAY. by human-made noise or strong local signals. It is
slow-operate, slow-release relay See SLOW- also useful for radio direction finding (RDF) at fre-
MAKE-SLOW-BREAK RELAY. quencies up to approximately 20 MHz. Compare
slow-release, fast-operate relay See SLOW- FERRITE-ROD ANTENNA, LARGE LOOP AN-
slow-release, slow-operate relay See SLOW- small signal A low-amplitude signal. Such a signal
BREAK-SLOW-MAKE RELAY. covers so small a part of the operating character-
slow storage A form of memory with long storage istic of a device that operation is essentially lin-
and recovery time. ear. Compare LARGE SIGNAL.
638 small-signal analysis • smoke detector

small-signal analysis Analysis of circuit or compo- S meter In a radio communications receiver, a me-
nent operation in which it is assumed that the ter graduated in S units and/or decibels to indi-
signals deviate from (fluctuate to either side of) cate the strength of a received signal.
the steady bias levels by only a small amount.
small-signal bandwidth The frequency at which
the output signal of an analog circuit decreases to 9 20
7 40
“3 dB, relative to the value for direct current. The 3 60
output voltage is generally set at 0.1 volt peak-to- 1
peak for testing this value so that the circuit is S units dB
not overdriven.
small-signal component 1. A coefficient or pa-
rameter (such as amplification, transconduc-
tance, dynamic resistance, etc.) calculated or
measured under conditions of small-signal oper-
ation. Also see SMALL SIGNAL and SMALL-
designed for operation at low signal levels.
small-signal diode See SIGNAL DIODE.
S meter
small-signal equivalent circuit For a given transis-
tor circuit, the equivalent circuit for low signal lev-
els (i.e., at amplitudes lower than saturation and Smith chart A curvilinear graph on which com-
cutoff levels). Also see EQUIVALENT CIRCUIT. plex-number impedance values can be plotted. It
small-signal operation Operation at low signal is useful in evaluating the behavior of radio-
amplitudes (i.e., at signal levels that do not ex- frequency circuits, transmission lines, and
tend into the saturation or cutoff levels of a tran- antenna systems”especially with regard to
sistor, diode, or other component). impedance mismatches and standing-wave ratio.
small-signal transistor A transistor designed for
low-level applications, such as the amplification
of small voltages and currents and low-voltage
0 Short
switching. Compare POWER TRANSISTOR. SWR = 4:1
SWR 10:1
SmallTalk A high-level computer programming Resistance
language that uses a graphical user interface
’25 +25
(GUI). It is used in complex design and research, 25
SWR = 2:1
and in robotics.
smart home or business An electronically con-
trolled home or business, in which computers
0 ’ j40 0 + 40
50 + j0 50
and robots take care of cooking, dish washing,
’50 +50
floor scrubbing, waste removal, laundry, yard 50 + j50
50 ’ j50
maintenance, snow removal, and other mundane
chores. Intrusion detection and fire prevention
are constantly maintained. In some cases, in- 100
truders can actually be identified or detained; ’100 +100
fires can be extinguished by controlled sprinkler
systems or remotely controlled robots. Some
tasks can be monitored and controlled directly by
∞ Open
the owner from remote locations, via telephone SWR = ∞ :1
lines or wireless. (Worst possible
smartness The ability of an electronic system, es- mismatch)
pecially a computer or control system, to perform
a complete series of operations, substituting al- Smith chart
ternative steps, where necessary”all with a min-
imum of instructions from, and supervision by,
human operators. smoke alarm A device that produces audible
smearing In television or facsimile, a form of picture and/or visible signals in the presence of smoke or
distortion caused by an excessively narrow receiv- unusual gases in the air. Also see PHOTOELEC-
ing bandpass. The image appears fattened and TRIC SMOKE ALARM.
horizontally blurred. Contrast might also be lost. smoke control See PHOTOELECTRIC SMOKE
smectic crystal A liquid crystal in which the CONTROL.
molecules are arranged in parallel layers and smoke detector Any circuit or device used to
cannot slide past each other. sense the presence of smoke or noxious gases.
smoke detector • software

Some types detect changes in the ionization Snell™s law A rule of physics that applies to visible
potential of the air; others sense changes in light passing from air (or a vacuum) to some
the dielectric constant of the air. Also see medium with an index of refraction c. If the light
PHOTOELECTRIC SMOKE DETECTOR. ray strikes the medium at an angle u, relative to a
smoke sensor See SMOKE DETECTOR. line normal (perpendicular) to the surface, and
smooth 1. Relatively free from surface irregularity. passes into the medium at angle v relative to the
2. To reduce or eliminate irregularities in the volt- normal, then (sin u)/(sin v) = c.
age or current from a direct-current power sniffer See EXPLORING COIL.
source. 3. To reduce or eliminate irregularities in sniperscope A telescope, snooperscope, or star-
data or signal amplitude. light scope for a carbine or rifle.
smoothing choke A power-supply filter choke (S+N)/N Abbreviation of SIGNAL-PLUS-NOISE-TO-
having a core with an air gap that prevents satu- NOISE RATIO.
ration at maximum rated direct current. Com- SNOBOL Acronym for string-oriented symbolic lan-
pare SWINGING CHOKE. guage, a computer-programming language for
smoothing factor For a power-supply filter, a manipulating character strings.
quantity approximately equal to 6.28fRC, where f snooperscope 1. An infrared-sensitive device that
is the alternating-current frequency in Hertz, R is permits viewing objects and surroundings in total
the filter resistance (in an RC filter) or the series darkness. It presents the image on a fluorescent
reactance of the choke (in an LC filter) in ohms, screen. 2. A rifle-mounted starlight scope.
and C is the filter capacitance in farads. snow A type of television picture interference that
smoothing filter 1. A filter for smoothing the al- typically occurs when the signal-to-noise ratio is
ternating-current ripple component of a direct- low (the reception is marginal or poor). Charac-
current power supply following rectification. It terized by countless tiny out-of-focus light spots,
can consist of one or more parallel capacitors of whose rapid, random motion mimics the appear-
large value, and one or more series chokes of ance of falling snow.
large inductance. 2. A low-pass filter used at the SNR Abbreviation of SIGNAL-TO-NOISE-RATIO.
output of a digital-to-analog (D/A) converter for soak value The smallest value of current that will
eliminating high-frequency components gener- cause saturation of a relay core.
ated by sampling. Society of Motion Picture and Television Engi-
SMPTE Abbreviation of SOCIETY OF MOTION PIC- neers Abbreviation, SMPTE. A group that de-
TURE AND TELEVISION ENGINEERS. cides on various procedures in video recording
smudge See SQUEEZEOUT. and reproduction, both on magnetic media (tape
SN Abbreviation of semiconductor network. or disk) and on film.
S/N Abbreviation of SIGNAL-TO-NOISE RATIO. socket A (usually female) fixture into which a plug,
Sn Symbol for TIN. integrated circuit, or other component is inserted
snake 1. A long, strong, flexible wire or strip used for easy installation in, or removal from, a circuit.
to pull other wires through electrical conduits. 2. socket punch See PUNCH, 2.
To route wires or cables through a group of cir- sodium Symbol, Na. A metallic element of the al-
cuits, components, or boards. kali-metal group. Atomic number, 11. Atomic
snap-action switch A switch that snaps quickly weight, 22.9898.
into the on or off position to prevent arcing and sodium silicate See WATER GLASS.
consequent premature contact deterioration. sodium-vapor lamp A gas-discharge lamp con-
snap diode A semiconductor diode in which taining neon and a small amount of sodium. After
switch-off time after carrier storage is extremely the filaments of the lamp are lighted for a short
short (e.g., under 1 nanosecond). time, the heat vaporizes the sodium, and the fila-
snap magnet A magnet that reduces the tendency ments are disconnected by an automatic switch.
for arcing in relay-control instruments, thereby Under the influence of the voltage across the
minimizing electromagnetic interference and pro- lamp, the sodium vapor glows with a characteris-
longing contact life. tic yellow light.
snap-on connector An electrical connector that sofar A system for pinpointing the source of under-
locks in place, reducing the chance that it will de- water sounds (coming from as far away as 2000
tach unless it is deliberately removed. miles) through triangulation. The name is an
snapshot dump During a computer program run, acronym for sound fixing and ranging.
a dump, for debugging purposes, of certain stor- soft-drawn wire Wire that is highly malleable, and
age areas. is therefore easily bent and unbent. Compare
sneak current Unintended current flow through a soft iron A grade of iron, used in some cores, that
path that is auxiliary to a main circuit. is easily demagnetized.
sneak path A path through which current is soft solder A low-melting-point solder.
accidentally detoured; it is usually a leakage software 1. Vendor-supplied or user-generated
path. programs or groups of programs for a computer
640 software • soldering gun

or computer system. 2. The detailed instructions quency, such as 2800 MHz. The solar flux tends to
for performing a particular operation with a cal- be highest during periods of the greatest sunspot
culator or a computer. activity and immediately following a solar flare.
software-defined radio Abbreviation, SDR. 1. solar laser See SUNLIGHT-POWERED LASER.
Wireless communications in which the modula- solar noise Broadband electromagnetic noise gen-
tion waveforms and protocols are generated and erated by the sun. In particular, noise that occurs
decoded by computer software. This allows a at radio frequencies and affects satellite, moon-
single, microcomputer-controlled radio receiver, bounce, and space communications. This noise
transmitter, or transceiver to operate in a variety varies in intensity with the 11-year sunspot cycle,
of services that use different protocols. Changing being generally higher at and near sunspot max-
the modulation waveform or protocol requires ima. A solar flare can cause a sudden and dra-
only a change in the program run by a micro- matic increase in the noise at all wavelengths.
computer that controls the radio. 2. A receiver, See SOLAR FLARE.
transmitter, or transceiver that employs the solar panel An array consisting of a number of se-
technology defined in (1). 3. The use of wireless ries-connected or series-parallel-connected solar
equipment that employs the technology defined cells mounted on a flat plate.
in (1). solar power Useful amounts of electricity obtained
soft X rays Low-frequency (long-wavelength) from suitable arrays of solar cells.
X rays. Such radiation has relatively poor pene- solar radiation Electromagnetic energy of various
trating power. Compare HARD X RAYS. wavelengths originating in the sun. Such radia-
sol 1. Abbreviation of SOLUTION. 2. Abbreviation tion, after passing through the earth™s atmo-
of SOLUBLE. sphere, consists mostly of infrared rays and
solar access For a specific property or location, the visible light. Some ultraviolet rays also reach the
availability of direct exposure to the sun™s rays as earth™s surface.
a source of energy. solar relay See SUN SWITCH.
solar absorption index A quantitative measure of solar switch See SUN SWITCH.
the effect of the sun on the ionospheric absorp- solar wind Continuous emission of high-speed sub-
tion of radio waves. atomic particles by the sun. It causes distortion of
solar activity See SOLAR RADIATION and the lines of flux in the earth™s magnetic field. It be-
SUNSPOT cycle. comes more intense following a solar flare.
solar battery A battery composed of solar cells solder 1. A metal alloy (usually of tin and lead) that
connected in series and/or parallel for increased is melted to electrically and mechanically join
output. pieces of other metals. Also see HARD SOLDER
solar cell A photovoltaic power transducer that and SOFT SOLDER. 2. To join metals with solder.
converts visible light to electricity. It is called a
cell because its output is a low direct-current
voltage. Such cells can be connected in series
and/or parallel to provide useful electric power Solder Melting point Principal
output. type (°F/°C) uses
solar cycle See SUNSPOT CYCLE.
Tin-lead 50 : 50, 430/220 Electronic
solar energy 1. The total energy arriving from the
rosin-core circuits
sun, over a given period of time and within a spe-
cific surface area, at a given location on the sur- Tin-lead 60 : 40, 370/190 Electronic
face of the earth. 2. Any energy derived entirely rosin-core circuits,
from the sun. low-heat
solar-energy conversion Any process that changes
Tin-lead 63 : 37, 360/180 Electronic
solar radiant energy into another useful form.
rosin-core circuits,
solar flare A violent storm on the surface of the
sun. These events tend to occur near the peak of
the 11-year sunspot cycle. They cause an in- Tin-lead 50 : 50, 430/220 Non-electronic
crease in the level of radio noise that comes from acid-core metal bonding
the sun, and they emit high-speed subatomic Silver 600/320 High-current,
particles that reach earth a few hours after the high-heat
first appearance of the flare. Because the parti-
cles are electrically charged, they are accelerated
by the geomagnetic field. Sometimes a geomag- soldering Joining (usually nonferrous) metal parts
netic storm results, producing aurora near the with solder, a lead-alloy substance. Compare
poles and deterioration of ionospheric radio- BRAZING.
propagation conditions. soldering gun An electric soldering iron having the
solar flux An indicator of general solar activity. The general shape of a handgun. The element heats
solar noise level is measured at a particular fre- and cools more rapidly than the element in a
soldering gun • solution

typical soldering iron. The element is heated by solid-state Pertaining to devices and circuits in
pressing a device similar to the trigger on a pistol. which the flow of charge carriers (electrons and
soldering iron An electric or nonelectric tool hav- holes) is controlled in specially prepared blocks,
ing a heated tip for melting solder. wafers, rods, or disks of solid materials. Semicon-
solderless breadboard A foundation (see BREAD- ductor devices, such as transistors and inte-
BOARD, 1) on which a circuit can be assembled grated circuits, are solid-state components.
by plugging components into tiny jacks without solid-state battery An atomic battery consisting
the use of solder. essentially of a photovoltaic cell in combination
solderless connection A connection between with a quantity of radioactive material, whose ra-
leads, or between leads and terminals, accom- diation causes the cell to generate electricity.
plished entirely through crimping, pinching, solid-state camera A video camera device that
splicing, or wire wrapping. Solder is not used. makes use of solid-state technology. The target is
Also see WIRE-WRAP CONNECTION. a matrix of charge-coupled devices (CCDs). When
solderless terminal A terminal to which a solder- light strikes these devices, charge carriers are
less connection can be made. Also see WRAP separated in a manner similar to that in a photo-
POST. voltaic cell. The matrix is scanned according to a
solenoid 1. A coil of wire having a single layer, particular scheme, and the voltages developed in
wound on a cylindrical form. 2. A multilayer coil each CCD combine to produce the video signal
used as an electromagnet, and usually having a output.
straight, iron core. solid-state capacitor See SOLID ELECTROLYTIC
solid-state chronometer Any semiconductor de-
vice to indicate or measure time.
solid-state circuit See MONOLITHIC INTE-
solid-state lamp 1. See LIGHT-EMITTING DIODE.
solid-state maser A device, such as the ruby
maser, in which the stimulated medium is a solid
solid-state photosensor A semiconductor photo-
diode or phototransistor, as opposed to a photo-
solid-state physics The branch of physics con-
solenoid switch A switch consisting of a solenoid cerned with the nature and applications of such
coil (see SOLENOID, 2) into which a core is pulled solids as electronic semiconductors.
by the magnetic field to close a pair of contacts. solid-state relay 1. A sensitive relay consisting of
solid 1. One of the states of matter. It is character- a conventional electromagnetic relay preceded by
ized by a definite shape and volume, and by a transistorized amplifier. 2. A completely elec-
atoms that maintain a fixed position, relative to tronic relay (i.e., one without moving parts) in
each other. Compare GAS, LIQUID, and PLASMA. which switching transistors provide the on and
2. An enclosed, defined volume of three-dimen- off states. 3. See THYRISTOR.
sional space. 3. In communications, descriptive solid-state thermometer An electronic thermo-
of error-free reception of a series of coded signals. meter utilizing one or more solid-state compo-
4. In printing and data transmission, a large nents, such as transistors, integrated circuits, or
print area whose entire surface is of equal and thermistors.
maximum intensity (of ink, light, or darkness). solid-state thyratron See SILICON-CONTROL-LED
solid angle Unit, steradian. The angle within the RECTIFIER and SILICON-CONTROLLED SWITCH.
apex of a cone formed by all line segments be- solid-state tube A semiconductor device (diode,
tween the center of a sphere and a defined circle rectifier, transistor, SCR, etc.) whose housing and
on the surface of the sphere. base allow it to replace directly an electron tube.
solid circuit Any circuit consisting of a single piece solid tantalum capacitor A capacitor using tanta-
of hardware that is not normally separated into lum as a solid electrolyte.
smaller parts. solid wire Wire consisting of a single strand of
solid conductor See SOLID WIRE. metal. Compare STRANDED WIRE.
solid electrolyte A solid substance affording ionic solute A substance that is dissolved in some other
action similar to that in a liquid electrolyte. substance. Also see SOLUTION, 1.
solid electrolytic capacitor A capacitor using a solution 1. A well-diffused mixture of two or more
solid electrolyte. substances. It can consist of a gas in a liquid, a
solid ground See DIRECT GROUND. gas in a solid, a gas in a gas, a liquid in a solid, or
642 solution • SOS

a solid in a solid. A solution, typically, is molecu- sonde A device for automatically gathering metero-
lar (i.e., there is no chemical reaction between its logical data at high altitudes. An example is the
constituents). Also see SATURATED SOLUTION; radiosonde.
SOLUTE; SOLVENT, 1; and SUPERSATURATED sone A unit of loudness for an individual listener.
SOLUTION. 2. The result of solving a problem or The level of 1 sone is the loudness of a 1000-Hz
making a calculation. Also called answer or result. tone that is 40 dB above the particular listener™s
solution conductivity The electrical conductivity threshold of hearing.
of a solution, such as an electrolyte. The conduc- sonic altimeter An altimeter (see ABSOLUTE AL-
tivity (and conversely, the resistance) depends on TIMETER) using sound waves. The time required
the number and mobility of ions in the solution. for a transmitted wave to reach a target and be
solution-conductivity bridge A direct-current reflected back to the transmitter is proportional
bridge specially designed and calibrated to mea- to the distance between the transmitter and the
sure the conductivity of chemical solutions. target.
solution pressure In an electrolyte into which a sonic boom An explosive sound occurring when
metal body is immersed, the force that causes the the shock wave produced by an aircraft flying at
metal to tend to pass into solution as positive supersonic speed strikes the earth.
ions and to form a Helmholtz double layer. sonic delay line A delay line using electroacoustic
solvent 1. A fluid that dissolves other materials. transducers and an intervening medium through
2. The constituent of a solution that dissolves one which a sound wave is transmitted.
or more other constituents. Thus, in a saltwater sonic depth finder See ACOUSTIC DEPTH
solution, water is the solvent and salt the solute. FINDER.
Also see SOLUTION, 1. sonic thermocouple A thermocouple whose heat-
SOM Abbreviation of start of message. absorbing properties are enhanced by subjecting
Sonalert Tradename for a small, but loud, sound it to acoustic vibrations.
reproducer used with solid-state circuits for sonobuoy A buoy equipped with an acoustic re-
alarm purposes. ceiver and radio transmitter. The device is
sonar A system of detection and ranging by means parachuted into the water, where it receives sub-
of sonic and ultrasonic signals. In this system of marine sounds and transmits them to a monitor-
echo ranging, the distance to an underwater ob- ing station. Several sonobuoys communicating
ject is determined from the time it takes a sound with a computer will track the path of a subma-
signal to reach the object and be reflected back to rine.
the transmitter. The name is an acronym for sonovox An electronic device used to produce spe-
sound navigation and ranging. cial sound effects when it is held against the
throat of the operator. The special sounds are
formed into words by the operator™s mouth.
SOP Abbreviation of standard operating procedure.
sophisticated electronics Advanced electronics
theory and operations, usually dealing with com-
plex devices or systems and requiring rigorous
analysis to describe their operation and de-
vise applications. Compare UNSOPHISTICATED
sorption processes Processes whereby certain
substances (e.g., activated charcoal) occlude and
retain gases and vapors. A chamber containing
Acoustic waves
such a substance is often useful in the produc-
tion of a vacuum. Sorption includes both absorp-
tion and adsorption.
sort 1. To group information items using their
keys. Also see KEY. 2. To group information items
according to some system of classification, as to
print an alphabetical list of words stored in a ran-
dom sequence.
Submarine sorting routine A computer program for sequenc-
ing data items according to key words (values in
specific fields) of the different records.
SOS 1. The international radiotelegraph distress
signal; equivalent to mayday in radiotelephony. It
consists of three dits (“dots”), followed by three
dahs (“dashes”), followed by three more dits.
sonar 2. Abbreviation of SILICON ON SAPPHIRE.
sound • sound power level

sound The vibratory or wave phenomenon to which frequency. See, for illustration, INTERCARRIER
the sense of hearing is responsive. Conducted by RECEIVER and SPLIT-SOUND RECEIVER.
waves in solids, liquids, and gases; not propa- sound-level meter See SOUND SURVEY METER.
gated through a vacuum. sound marker A marker indicating the sound-
sound absorption The nonreflection and nontrans- carrier point on a television alignment curve
mission of acoustic energy by a body or medium, displayed on an oscilloscope screen.
and the attendant conversion of the acoustic en- sound-marker generator A special radio-
ergy into another form of energy (usually heat). frequency signal generator (or a special circuit in
sound absorption coefficient A quantitative ex- a television-alignment generator) for the produc-
pression of the extent to which a surface absorbs tion of a sound marker.
acoustic energy (as opposed to reflecting, trans- sound mirage See ACOUSTIC MIRAGE.
mitting, diffusing, or scattering it). sound mix In sound recording or reproduction, the
sound amplifier 1. An audio amplifier”especially composite output from an audio mixer circuit.
the sound channel of a television system. 2. A de- sound-on-film recording See OPTICAL SOUND
vice, such as a horn or reflector, that directly RECORDING.
boosts the intensity of sound at a given listening sound-on-sound recording The simultaneous
point. recording (on a single track on magnetic tape) of
sound analyzer An instrument, often a wave ana- new material with previously recorded material.
lyzer equipped with a microphone, for measuring The old recording is not erased.
such characteristics of sound as amplitude, fre- sound-operated relay 1. A relay operated indi-
quency (pitch), and harmonic content (timbre). rectly from sound, through the medium of a
sound articulation See ARTICULATION. pickup microphone and amplifier. 2. A relay hav-
sound bars In a television picture, horizontal bars ing a delicately poised armature that operates di-
resulting from interference between the audio rectly from sound vibrations.
and video channels of the receiver.
sound carrier In a television signal, the frequency-
modulated carrier that transmits the audio part
of the program. Compare VIDEO CARRIER.
sound chamber An air enclosure, usually a box or
can, for modifying the acoustic qualities of sound
or of an audio signal.
sound detector The discriminator or ratio detector
that demodulates the sound signal in a television
receiver circuit.
sound-energy density Sound energy per unit vol-
ume, expressed in joules per cubic meter or ergs Filter
per cubic centimeter.
sound-energy flux The average rate of flow of
sound energy through a specified area, as ex-
pressed in ergs or joules per second.
sound field A volume of space or material contain-
ing sound waves.
sound film Motion-picture film on which a sound dc
track is recorded. Also see OPTICAL SOUND
sound flux The rate of flow of sound energy, usu-
ally expressed in terms of sound pressure at a
point or over a unit area normal to the direction
of sound propagation.
sound gate An optical device used to convert the
sound track of a movie film into electrical impulses. Relay
circuits or
sound generator Any combination of oscillator, systems
amplifier, and transducer (loudspeaker or head-
phones) for producing sound waves.
sound-operated relay
sound-hazard integrator An instrument used to
measure cumulative noise exposure received by
persons in noisy environments. One such instru- sound power The total sound energy per unit time
ment provides direct readings in percent of per- produced by a sound source, as expressed in ergs
missible exposure. per second or in watts.
sound IF amplifier In a television receiver circuit, sound power level The extent, in decibels, by which
SOUND POWER exceeds one picowatt (10“12 watt).
the separate amplifier for the sound intermediate
644 sound pressure • source follower

sound pressure 1. The force exerted by sound sound track The variable-density or variable-width
waves on a surface area, expressed in dynes per recording on one side of the film in sound-on-film
square centimeter (as an rms value over 1 cycle). recording and reproduction. Also see OPTICAL
The sound pressure is proportional to the square SOUND RECORDING.
root of sound-energy density. 2. The instanta- sound transducer See ACOUSTIC TRANSDUCER.
neous difference between actual air pressure and sound-transmission coefficient See ACOUSTI-
average air pressure at a given point. CAL TRANSMITTIVITY.
sound pressure level The extent, in decibels, via sound trap In a television receiver circuit, a wave-
which SOUND PRESSURE exceeds 20 micropas- trap that prevents the sound signal from entering
cals (2.0 — 10“5 pascal). the picture channels.
sound probe A transducer used to receive acoustic sound unit See PHONE, 2.
vibrations for detection or measurement pur- sound wave The vibratory phenomenon produced
poses. in a medium by acoustic energy. A sound wave in
sound recording The electrical recording of sound, air consists of alternate compressions and rar-
using cylinder, disc, tape, wire, or other compa- efactions of the air. Also see ACOUSTIC WAVE.
rable storage medium. source 1. The origin of a signal or electrical energy
sound-recording system A complete, integrated (e.g., a transmitting station). 2. In a field-effect
array of equipment for recording sound, includ- transistor, the electrode that is equivalent to the
ing such components as microphones, ampli- emitter of a common-emitter-connected bipolar
fiers, pickups, filters and other shaping net- transistor, or the cathode of a vacuum tube.
works, attenuators, level indicators, and 3. That which is being transcribed to magnetic
recording mechanisms. Compare SOUND- tape. 4. Manufacturer, wholesaler, or retailer.
REPRODUCTION SYSTEM. source circuit 1. The circuit associated with the
sound reinforcement Intensification of sound by source electrode of a field-effect transistor. 2. A
horns, resonant chambers, or other acoustical generator circuit. Compare SINK CIRCUIT.
devices. source code See SOURCE LANGUAGE.
sound relay See SOUND-OPERATED RELAY. source computer A computer for compiling a
sound reproduction The electrical reproduction of source program.
sound from recordings on vinyl discs, magnetic source-coupled multivibrator A multivibrator cir-
tapes, magnetic discs, compact optical disbs, etc. cuit using field-effect transistors, in which feed-
sound-reproduction system A complete, inte- back coupling is achieved with a common source
grated array of equipment for the playback of resistor for the two FETs. This circuit is equiva-
recorded sound, including such components as lent to the emitter-coupled bipolar-transistor-
tape or record players, amplifiers, filters and type multivibrator.
other shaping networks, attenuators, level indi- source data automation A means of storing a
cators, loudspeakers, and headphones. Compare master data file for easy duplication, whenever
sound spectrograph A device that produces a dis- source deck An audio or video tape player that re-
play of sound amplitude vs. frequency. Similar to produces original recordings in the editing process.
a SPECTRUM ANALYZER, except that it operates source follower A field-effect-transistor circuit in
at audio frequencies (about 20 Hz to 20 kHz) and which the output is taken across a resistor be-
is actuated by acoustic disturbances, rather than tween source and ground. This circuit is equiva-
by electromagnetic signals. lent to the emitter follower, and is a unity-gain
sound spectrum The continuous band of fre- stage whose impedance-transformation charac-
quencies (about 20 Hz to 20 kHz) constituting teristics make it ideal in signal conditioning,
audible sounds, and sometimes the immediately buffering, and impedance-matching applications.
adjacent (subaudible and superaudible) fre-
quencies. +dc
sound stage The apparent dimensions of a sound
sound survey meter A portable instrument for Cin
measuring the intensity and other characteristics
of sound.
sound sweetening In audio recording or reproduc-
tion, the modification of the sound to achieve Signal
some desired effect. input Signal
sound system A sound-recording system, sound- output
reproduction system, or a combination of the two.
sound takeoff In a television receiver circuit, the
point at which the frequency-modulated sound
source follower
signal is extracted from the complex signal.
source impedance • special character

source impedance 1. The impedance of a genera- spark energy The energy dissipated by an electric
tor in a circuit. 2. The impedance of the source arc or spark.
electrode of a field-effect transistor. spark gap A device consisting essentially of two
source language A computer programming lan- metal points, tips, or balls that are separated by a
guage from which is derived (by a compiler) the small air gap. A high voltage applied to the elec-
machine (object) language on which the computer trodes causes a spark to jump across the gap.
operates. sparking distance The maximum separation of
source program A computer program written in a the electrodes of a spark gap at which a given
source language. voltage will produce a spark.
south magnetic pole The south pole of the equiv- sparking voltage The lowest voltage that will
alent bar magnet constituted by earth™s magnetic cause a spark to jump across a gap of a given
field (see EARTH™S MAGNETIC FIELD). The south width.
magnetic pole lies close to the geographic south spark killer See SPARK SUPPRESSOR.
pole. Compare NORTH MAGNETIC POLE. sparkover A discharge in air, a vacuum, or a di-
south-seeking pole Symbol, S. The so-called electric. It is characterized by sparking between
south pole of a magnet. When a bar magnet is electrodes in the medium.
suspended horizontally, this pole points to spark plate In some automobile radios, a noise-
earth™s south magnetic pole. Compare NORTH- interference-eliminating bypass capacitor in
SEEKING POLE. which the chassis is one plate.
SP Abbreviation of STACK POINTER. spark-plug suppressor A small resistive device
sp 1. Abbreviation of single pole. 2. Abbreviation of connected in series with a spark plug to suppress
special. electrical noise arising from the ignition in an in-
space-charge field 1. The electric field existing ternal combustion engine.
within a group of charged particles. 2. The elec- spark quencher See SPARK SUPPRESSOR.
tric field existing in a plasma. spark suppressor A resistor, capacitor, and/or
space diversity See DIVERSITY RECEPTION. diode used to eliminate or minimize sparking be-
space-diversity reception See DIVERSITY RE- tween make-and-break contacts.
space division A method of data transfer in which
different paths are used for the transmission of
To keyed
different signals.
space-division switch A switch having two or more
ports and different paths connecting the ports.
space lattice The three-dimensional, redundant
pattern formed by atoms and molecules in a crys-
tal and having a shape that is characteristic of a
particular crystalline material.
spacer An insulating rod or bar that serves to hold
spark suppressor
apart the conductors of a two-wire, four-wire, or
coaxial air-dielectric transmission line.
space suppression Following the printing of a line spark-suppressor diode See SUPPRESSOR
by a printer, the prevention of normal paper travel. DIODE.
space-time-space switch Abbreviated STS switch spatial distribution The three-dimensional direc-
or STSS. A large switching array with two space tional pattern of a transducer (such as an an-
switch blocks and a time switch block between tenna, microphone, or speaker).
them. spc 1. Abbreviation of silicon point contact. 2. Ab-
space wave One of the components of an electro- breviation of silver-plated copper.
magnetic ground wave. The space wave, unlike SPDT Abbreviation of SINGLE-POLE/DOUBLE-
the surface wave, is not earth-guided. It has two THROW (switch or relay).
components: the direct wave and the ground- speaker See LOUDSPEAKER.
reflected wave. speaker damping See DAMPED LOUDSPEAKER.
spaghetti Slender, varnished-cambric tubing used speaker-level audio In a sound reproduction sys-
as slipover insulation for wires and busbars. tem, radio receiver, or other audio circuit, an au-
span On an instrument scale, the difference be- dio-frequency signal of sufficient amplitude to
tween the highest value and the lowest value. drive a speaker or speaker system directly, with-
spark See ELECTRIC SPARK. out the need for additional amplification.
spark absorber 1. See SPARK SUPPRESSOR. 2. speaking arc A method of modulated-light trans-
See KEY-CLICK FILTER. mission. An electric arc is modulated by audio-
spark coil A small induction coil. Its name is de- frequency signals.
rived from its initial purpose of supplying the special character A printed, displayed, or encoded
high voltage for spark plugs in gas engines. character other than a numeral or letter, such as
646 special character • speech clipping

an ampersand (&) or a pound sign (#). Also called through the material under analysis is broken up
SYMBOL. into a spectrum that is examined with a photo-
special effects Various techniques used in film- electric circuit, which, in turn, plots a spectro-
making, computer animation, and videotape gram.
recording for achieving certain visual scenes or spectroscope An instrument that resolves a radia-
images. tion into its various frequency components and
special-purpose computer A computer designed permits measurement of each.
to handle problems or be suitable for applications spectrum A band of frequencies or wavelengths
of a specific category; a dedicated computer. (e.g., radio spectrum, visible-light spectrum, and
special-purpose calculator An electronic calcula- sound spectrum).
tor intended for essentially “nonmathematical” spectrum analyzer 1. An automatic wave analyzer
purposes, such as biorhythm data, astrological with a visual display (oscilloscope). 2. A scanning
information, metric conversions, musical com- receiver with a screen that shows a plot of signals
posing, etc. and their bandwidths over a specific frequency
specific address See ABSOLUTE ADDRESS. band.
specification 1. For an electronic device, a state-
ment of performance over specific parameters.
Example: for a high-fidelity stereo amplifier, 50

watts per channel over a frequency range of 10 Hz
Amplitude axis
to 30 kHz, with less than 1 percent total har-

monic distortion. 2. A precise listing of require-
ments or expectations.
specific conductivity Conductance per unit vol-
ume. In SI units, this is expressed in siemens per
cubic centimeter (S/cm3).
specific dielectric strength For an insulant, the
dielectric strength per millimeter of thickness.
specific gravity Abbreviation, sp gr. The ratio of
the density of a material to the density of a sub-

stance accepted as a standard (usually water at 4
degrees Celsius or 39.2 degrees Fahrenheit).
specific inductive capacity See DIELECTRIC
specific resistance See RESISTIVITY.
specific sound-energy flux See SOUND INTEN-
spectral comparative pattern recognizer Acro- Noise floor
nym, SCEPTRON. Equipment used to classify
automatically complex signals obtained from
information that has been converted into electri-
spectrum analyzer, 2.
cal signals.
spectral density For a complex signal, the amount
of energy contained within a given band of fre- specularity A qualitative or experimentally derived
quencies. expression of the efficiency with which a
spectral energy distribution The occurrence of DIFFRACTION GRATING works.
different amounts of energy in different areas of a specular reflection Reflection in which the re-
spectrum (as in a visible-light spectrum, sound flected ray is in the same plane as the incident
spectrum, or radio-frequency spectrum). ray, as in reflection from an extremely smooth
spectral response The characteristic of a device, surface.
such as a photocell or the human eye, that de- speech amplifier A (usually low-level) audio am-
scribes the device™s sensitivity to radiations of plifier designed especially for speech frequencies.
various frequencies in a given spectrum. It is generally used to amplify the signals from a
spectral sensitivity The color response of a light- microphone.
sensitive device. speech clipper A device, such as a biased diode,
spectrograph A recording SPECTROMETER. (see POSITIVE PEAK CLIPPER) for holding speech
spectrometer 1. An instrument used to measure signals to a constant amplitude. Compare
spectral wavelengths. 2. An instrument used to SPEECH COMPRESSOR. Also see SPEECH CLIP-
measure the index of refraction. 3. See MASS PING.
SPECTROMETER. speech clipping The use of a limiting circuit to
spectrophotometer A photoelectric instrument for maintain the output-signal amplitude of a speech
chemical analysis. In the device, light passing amplifier against fluctuations in the intensity of

speech clipping • speed of transmission

speech input. The resulting signal requires filter-
ing to remove harmonics generated by the pro-
cess. Compare SPEECH COMPRESSION. Mic. analyzer
speech compression Automatic regulation of the
gain of a speech amplifier to maintain its output-
signal amplitude against speech-input fluctua-
tions. Compare SPEECH CLIPPING.
speech compressor A circuit or device, such as an
automatic-gain-control (agc) system, for perform-
ing speech compression. Compare SPEECH CLIP-
PER. To computer
or robot
speech digit signaling A method of digital signal-
ing, where time slots generally used for encoded
audio or video are used alternately for signaling.
speech frequencies See VOICE FREQUENCIES.
speech intelligibility The quality of reproduced
speech that makes it easily understood by a rea-
sonably proficient user of the language. For good
speech intelligibility, a circuit should transmit
frequencies between 300 Hz and 3000 Hz with Vocabulary
minimal distortion. Increased bandwidth im-
proves fidelity, but does not provide a significant
increase in intelligibility for normal speech.
speech inverter See SCRAMBLER CIRCUIT.
speech recognizer
speech power 1. The alternating-current power in
an electric wave corresponding to speech, as op-
posed to that in a sine wave. 2. Sound power in a
speech transmission.
speech recognition The ability of a device to
translate audible spoken words, phrases, or sen-
tences into binary digital signals that can be used
by machines, such as computers and robots.
speech recognizer An electronic device that trans- Spkr.
lates audible spoken words, phrases, or sen-
tences into binary digital signals that can be used
by machines, such as computers and robots.
speech scrambler See SCRAMBLER CIRCUIT.
speech synthesis The ability of a device to trans-
late binary digital signals from a machine, such
as a computer or robot, into audible, coherent
spoken words, phrases, or sentences.
speech synthesizer An electronic device that
Phoneme Phoneme
translates binary digital signals from a machine,
vocabulary selector
such as a computer or robot, into audible, coher-
ent spoken words, phrases, or sentences.
speed key 1. A semiautomatic key for manual gen-
eration of Morse code characters. 2. A similar,
fully automatic key used especially for high-
speed telegraphy. Optical
speed of light Symbol, c. The speed at which elec- character
tromagnetic waves propagate in a vacuum; ap- recognizer
proximately 299,792 kilometers per second
(186,282 miles per second).
speed of sound The speed at which acoustic waves
propagate. It depends on the nature of the
medium. In air, at ordinary temperatures, it is
approximately 344 meters (1129 feet) per second. Text
In fresh water, it is approximately 1463 meters hardcopy
(4800 feet) per second.
speed of transmission The amount of data sent in
speech synthesizer
a given unit of time. It is generally measured in
648 speed of transmission • spiral distortion

bits per second (bps), characters per second (cps), spiderweb antenna A set of dipole antennas for
characters per minute (cpm), or words per minute different frequencies, arranged in a common
(wpm). It is used primarily for digital codes. (usually horizontal) plane. The result is a broad-
speedup capacitor See COMMUTATING CAPACI- band antenna.
sp gr Abbreviation of SPECIFIC GRAVITY.
sphere 1. A closed surface in three-dimensional
space, represented by the set of all points
equidistant from a specified center point. 2. A
solid in three-dimensional space, represented by
the set of all points on or within a closed surface,
as defined in 1.
sphere gap A spark gap in which the spark passes
between two polished metal spheres. When the
air gap is adjustable, unknown high voltages can
be measured in terms of the largest gap width at
which sparking occurs. Compare NEEDLE GAP.
sphere-gap voltmeter See SPHERE VOLTMETER.
sphere voltmeter A gap voltmeter using a SPHERE Feed line
spherical aberration In a spherical lens, mirror, or
reflecting dish, distortion as a result of the spher-
ical (as opposed to paraboloidal) shape of the sur-
face. This causes the focus to be elongated into a
short line segment along the principal axis.
spherical angle An angle formed by the intersec- spiderweb antenna
tion of two arcs on the surface of a sphere.
spherical coordinate geometry A scheme for
guiding a robot arm in three dimensions via spiderweb coil A flat, single-layer coil in which a
SPHERICAL COORDINATES. The length (radius) strand of wire is woven over and under the
of the arm can be varied, as can the elevation (lat- spokes of a wheel-like form, and having the gen-
itude) and azimuth (longitude). eral appearance of a spiderweb. The criss-cross
spherical coordinates A method of defining a winding reduces distributed capacitance by
point (P) in three-space using two angles (latitude breaking up the parallelism of adjacent turns.
and longitude) and a radial distance (r) from the spike 1. A current or voltage pulse of extremely
origin. short duration. 2. A sharp transient, such as an
spherical degree A unit equal to 1„720 of the surface overshoot on a pulse or square wave.
area of a sphere. spike suppressor A clipper or similar device for re-
spherical distance The length of the shortest arc moving a spike from a signal voltage.
(lying on a great circle) connecting two specified spin A quantity of angular momentum possessed
points on a sphere. by a subatomic particle. It can be positive, nega-
spherical divergence The manner in which energy tive, or zero, but it always exists in integral mul-
tiples of 1„2.
normally propagates from a fixed point source in
three dimensions. Wavefronts expand from the spindle 1. The pivoted shaft that carries the mov-
source in the form of spheres, whose centers are able element and rotates between the pivots in a
at the point source. meter movement. 2. The rotor of an alternator”
spherical reflector A microwave reflector (dish) especially when the rotor is a permanent magnet.
whose contour is that of a sphere, rather than 3. The rotating shaft in a motor, generator, or
that of a paraboloid. similar electric machine.
spherical wave A wave characterized by wave- spinning electron An electron having nonzero an-
fronts that are concentric spheres. gular momentum.
spheroidal antenna A sheetmetal or wire-mesh spinthariscope An optical device for observing the
antenna having the cross section of a sphere that effect of alpha particles emitted by a radioactive
is flattened at the ends of one axis. substance, from the scintillations they produce
SPHW Abbreviation of SINGLE-PHASE HALF-WAVE. upon striking a small, fluorescent screen.
spider 1. The flat, round, springy part that holds the spiral coil See DISK WINDING.
apex of the vibrating cone of a dynamic speaker. spiral distortion A form of television camera-tube
2. A quickly assembled, chassisless hookup in distortion caused by spiraling of the electrons as
which the pigtails of components form the wiring they are emitted from the photocathode. The re-
and the mechanical support for a circuit. sult is a twisted image.
spiral-rod oscillator • spot modulation

spiral-rod oscillator A parallel-line-type oscillator split-load phase inverter See PARAPHASE IN-
in which the lines are rods that are rolled up into VERTER.
spirals to conserve space. Also see LINE-TYPE split-phase motor A fractional-horsepower, alter-
OSCILLATOR. nating-current motor that starts like a two-phase
spiral sweep 1. A means of sweeping the electron motor and runs like a single-phase motor. After
beam in a cathode-ray tube to produce a spiral the machine approaches approximately 75 per-
trace on the screen. 2. The circuit for producing cent of full speed, a centrifugal switch cuts out
such a sweep. the starting winding.
spiral trace See SPIRAL SWEEP. split projector An acoustic transmission device
spiral winding See DISK WINDING. with several independently operated transducers.
spkr Abbreviation of speaker (see LOUDSPEAKER). split-reed vibrator See SELF-RECTIFYING VIBRA-
splatter-suppression filter In an amplitude-mod- split-rotor plate See SERRATED ROTOR PLATE.
ulated (AM) or single-sideband (SSB) radio trans- split-stator capacitor A variable capacitor having
mitter, a low-pass filter inserted between the two separate stator sections and a common rotor
output of the audio amplifier and the audio input section.
of the modulator. It suppresses high-frequency split-sound receiver A television receiver circuit in
audio components that would otherwise cause which the sound signal is separated from the
sideband splatter. composite signal shortly after pickup by the an-
splaying The construction of a room or auditorium tenna, and is amplified separately from the video
so that the walls do not meet at right angles. It is signal. Compare INTERCARRIER RECEIVER.
useful in optimizing the acoustic characteristics splitter A device used to couple two or more televi-
of the enclosure because it tends to reduce sion receivers to a single antenna.
acoustic resonant effects. spool See REEL.
splice 1. A physical or electrical connection be- sporadic-E layer ionization Occasional, scattered
tween two wires, made by tightly winding the ionization in the E-layer of the ionosphere.
ends together. Solder is often applied for addi- sporadic-E propagation At certain radio frequen-
tional mechanical strength and electrical conti- cies, the long-distance propagation of electro-
nuity. 2. A physical connection between two magnetic (EM) waves via the E layer of the
lengths of magnetic tape, made in such a way as ionosphere. This layer exists at an altitude of ap-
to cause minimal disturbance in reproduced au- proximately 50 miles (80 km) above sea level. This
dio, video, or data. 3. To prepare a joint, as de- mode of propagation tends to be intermittent, and
fined in 1 or 2. conditions can change rapidly. It is most likely to
splicer A device for making a SPLICE. occur between 20 MHz and 150 MHz. Occasion-
splicing block A device specifically designed to fa- ally, it is observed at frequencies as high as 200
cilitate easy splicing of audio, video, or digital MHz. The propagation range is normally several
magnetic tape. hundred miles, but occasionally can occur over
splicing tape A durable, flexible adhesive designed distances of 1,000 to 1,500 miles. The standard
to hold a magnetic-tape splice together. frequency modulation (FM) broadcast band is
spline-based modeling In video animation and ad- sometimes affected by this propagation. The
vanced computer graphics, a scheme that uses same is true of the lowest television (TV) broad-
curve-generating formulas (e.g., Bezier curves) to cast channels, especially channels 2 and 3. See
create lifelike images. IONOSPHERE.
split-anode magnetron A magnetron in which the SPOT Abbreviation of satellite position and tracking.
plate (anode) consists of two semicylinders with spot brightness In a cathode-ray tube, the relative
the cathode at their axis. brilliance of the glowing dot or trace produced on
the screen by the electron beam.
spot check 1. To take a random sample or to make
Envelope a random test by arbitrarily selecting a single item
from a run of similar items and subjecting it to
One-half analysis, examination, performance, or paramet-
anode ric evaluation, etc. 2. A random sample or test.
spot frequency 1. A single frequency or signal to
which other frequencies can be referred. 2. A fre-
quency or signal that acts as a limit marker (e.g., to
define the edges of an allocated frequency band).
One-half spot jamming Deliberate interference to a radio sig-
Cathode anode nal at some frequency and at some specific time.
(Magnet not shown) spot modulation In a cathode-ray tube, modula-
tion of the brightness of the spot (and, accord-
ingly, of the image) produced on the screen by the
split-anode magnetron
650 spot modulation • square-law meter

electron beam. Also see INTENSITY MODULA- generated by faulty modulation, amplification,
TION. and/or oscillation.
spot welding A method of electrical welding in spurious oscillation 1. Oscillation in a normally
which the parts to be joined are held together, nonoscillatory circuit. 2. In an oscillator, simulta-
overlapping, between the points of two electrodes, neous oscillation at a frequency other than the
between which a current is passed to heat the normal one.
parts at the spot of contact. spurious response In a communications receiver,
spot-wheel pattern A frequency-identifying wheel a signal that appears to be on a certain fre-
pattern produced on an oscilloscope screen by in- quency, when, in fact, the received signal is not
tensity-modulating a circular trace. The circular on that frequency. It often results from inade-
trace is produced by applying a standard- quate image rejection.
frequency signal to the horizontal and vertical input spurious-response ratio The ratio of the transmis-
terminals 90 degrees out of phase. A square-wave sion (or gain) of a circuit of a desired signal to its
signal of unknown frequency is applied to the in- transmission (or gain) for a spurious signal at the
tensity-modulation (z-axis) input terminals. The same setting of the circuit (e.g., signal-to-image
square wave chops the circle into a number of ratio).
bright sectors or spots. The unknown frequency spurious sidebands In an amplitude-modulated
(fx) equals Nfs, where N is the number of spots in (AM) or single-sideband (SSB) radio signal, side-
the circle, and fs is the standard frequency. Com- band energy at frequencies outside the nominal
pare GEAR-WHEEL PATTERN. signal band, usually resulting from improper
sprat Acronym for small portable radar torch. A modulation, inadequate filtering, improper enve-
portable radar unit that uses a Gunn diode to lope clipping, or nonlinear amplification.
generate microwave energy. The range is about Sputnik The first orbiting artificial earth satellite.
500 meters (1„3 mile). It was launched by Russia (then known as the
spray coating 1. Applying a protective coat of in- Union of Soviet Socialist Republics) in 1957.
sulating material to a conductor or component by sputter 1. A layer of material obtained by sputter-
spraying it with a liquid substance and allowing it ing (see SPUTTERING, 1). 2. To carry out the pro-
to dry. Compare DIP COATING. 2. The coat ap- cess of sputtering (see SPUTTERING, 1).
plied, as defined in 1. sputtering 1. A technique for electrically deposit-
spreader 1. An insulator used to separate the ing a film of metal on a metallic or nonmetallic
wires of an air-spaced transmission line. 2. Any surface. In a vacuum chamber, the piece of metal
of the rods composing the supporting structure in to be deposited is made the cathode of a high-
a cubical quad antenna. voltage circuit, with respect to a nearby anode
spreading current In a semiconductor, current plate. The high voltage causes atoms to be ejected
caused by the movement of charge carriers by cir- from the surface of the cathode and strike the
cuitous routes, that is, in paths that deviate sig- surface of an object placed in their path, becom-
nificantly from straight lines. ing deposited on it as a film of cathode metal.
spreading loss Energy lost during the transmis- Compare EVAPORATION, 1. 2. The disintegration
sion of radiation. of a vacuum-tube cathode through ejection of
spreading resistance In a semiconductor device, surface atoms from the cathode by impinging
the resistance that is a consequence of electrical positive ions.
paths through material that is not along straight sq Abbreviation of SQUARE.
lines between electrodes. SQ band A section of the S BAND, from 2400 to
spread spectrum 1. A method of transmission in 2600 MHz.
which the occupied bandwidth of the signal is de- SQC Abbreviation of STATISTICAL QUALITY CON-
liberately increased, or spread out, over a much TROL.
wider range than it would normally occupy with SQR 1. Abbreviation of SQUARE ROOTER. 2. In
conventional modulation. 2. A signal transmit- the BASIC computer-programming language, a
ted, as defined in 1. function that computes the square root of a posi-
spring coil See SOLENOID, 1. tive number.
spring contact See FLEXIBLE CONTACT. S quad See SIMPLE QUAD.
sprite In video and animated computer graphics, a square-law demodulator See SQUARE-LAW DE-
brief insert, such as a little insect that scurries TECTOR.
across the screen, or a face that pops in and square-law detector A detector whose output is
smiles. It is used primarily for effect. proportional to the square of the root-mean-
SPST Abbreviation of SINGLE-POLE/SINGLE- square (rms) value of the input. Also called
THROW (switch or relay). WEAK-SIGNAL DETECTOR.
spurious emission From a radio or television square-law meter 1. A meter whose deflection is
transmitter, an unintended and unwanted proportional to the square of the quantity applied
output signal on a frequency other than the to it. Also see CURRENT-SQUARED METER. 2. A
fundamental signal frequency. It can be high-impedance electronic voltmeter, whose
square-law meter • ssc

deflection is proportional to the square of the ap- squegging A choking-type cutoff action in a circuit
plied voltage. caused by an excessively strong signal.
square-law modulator A circuit or device that ac- squegging oscillator An oscillator that starts and
complishes amplitude modulation of one signal stops oscillating intermittently as a result of
current by another, by simultaneously passing SQUEGGING.
the two currents through a component, such as a squelch See SQUELCH CIRCUIT.
nonlinear resistor, having a square-law response. squelch amplifier An amplifier that can be con-
square-law response Circuit or component opera- trolled by a squelch signal. Also see SQUELCH
tion that results in an output signal, proportional CIRCUIT.
to the square of the input. squelch circuit One of several circuits that auto-
square rooter An analog or digital device used to matically disable a receiver or amplifier, except
extract the square root of a number. when incoming signals exceed a predetermined
square wave An alternating or pulsating current or threshold amplitude. This action mutes the
voltage whose rise and decay times are essentially equipment, eliminating annoying background
zero, and whose maxima and minima are essen- noise and unwanted signals. Also called MUTING
tially flat. The duration of the maxima is equal to CIRCUIT.
the duration of the minima. A special form of squelch signal The activating or deactivating sig-
square-wave amplifier An amplifier designed to squiggle See BLIP, 2.
operate with square waves. squint 1. The angular resolution of a radar an-
tenna. 2. The angular difference between the
antenna axis and the major lobe of a radar trans-
squirrel-cage induction motor See SQUIRREL-
squirrel-cage motor An induction-type alternat-
ing-current motor using a squirrel-cage rotor.
squirrel-cage rotor In an alternating-current mo-
square wave
tor, a rotor composed of straight copper bars
embedded in a laminated soft-iron core and
square-wave converter See SQUARING CIRCUIT. short-circuited at the ends by rings. Its name is
square-wave generator A signal generator deliver- derived from its resemblance to a revolving squir-
ing an output signal that has a square waveform. rel cage.
square-wave testing Testing the response of a cir- SR 1. Abbreviation of SILICON RECTIFIER. 2. Ab-
cuit or device, such as an amplifier, by observing breviation of silicone rubber (see SILICONE).
the extent to which it distorts a square-wave 3. Abbreviation of SHIFT REGISTER.
signal passing through it (a measure of high- S-R Abbreviation of SEND-RECEIVE.
frequency response). Sr Symbol for STRONTIUM.
squaring circuit 1. A circuit (such as a twin-diode sr Abbreviation of STERADIAN.
clipper, overdriven amplifier, or Schmitt trigger) SRAM Abbreviation of static random-access mem-
that converts a sine wave or pulse into a square ory.
wave. 2. A circuit whose instantaneous output- S-rays See SECONDARY RAYS.
signal amplitude is equal to the square of the in- SRF Abbreviation of SELF-RESONANT FRE-
stantaneous input-signal amplitude. QUENCY.
squarish wave 1. A signal whose oscilloscope trace S-RF meter A dual-function meter in a radio
is nearly, but not exactly, the same as that of a transceiver. In the receiving mode, the meter in-
square wave. 2. A rectangular wave that is not a dicates S units. In the transmit mode, the meter
square wave; that is, whose maxima and minima indicates relative output power.
are not of the same duration. See RECTANGULAR SRR Abbreviation of SHORT-RANGE RADAR.
WAVE and SQUARE WAVE. SS 1. Abbreviation of SOLID STATE. 2. Abbrevia-
squawker 1. In a three-way speaker system, the tion of SINGLE SHOT. 3. Abbreviation of small
midrange speaker. 2. Any slave station in a mul- signal. 4. Abbreviation of SINGLE SIGNAL. 5. Ab-
tistation intercom network. breviation of same size. 6. Abbreviation of stain-
squeal A high-pitched interferential sound, such less steel.
as that encountered in spuriously oscillating sys- SSB Abbreviation of SINGLE SIDEBAND.
tems. SS band A section of the S BAND extending from
squeezeout In optical character recognition (OCR), 2900 to 3100 MHz.
a condition in which errors occur because the SSBSC Abbreviation of SINGLE-SIDEBAND SUP-
printed characters have excessive ink at the PRESSED CARRIER.
edges. Also called smudge. ssc Abbreviation of single-silk-covered (wire).
652 S scale • staggered tuning

S scale A scale of numbers used in radio commu- selenium rectifier plates (see POWER STACK).
nications, and especially in amateur radio, to re- 3. To assemble a stacked array. 4. A temporary
port the approximate strength of signals: S1, storage area consisting of a small group of regis-
faint signals; S2, very weak signals; S3, weak sig- ters in a computer memory.
nals; S4, fair signals; S5, fairly good signals; S6, stacked array An antenna system in which two or
good signals; S7, moderately strong signals; S8, more identical antennas, such as dipoles, Yagis,
strong signals; S9, extremely strong signals. Also or halos, are placed one above the other or side-
see S METER. by-side. It provides additional forward gain, and,
sse Abbreviation of single-silk-enameled (wire). in some cases, enhances the front-to-back ratio
SSI Abbreviation of SMALL-SCALE INTEGRATION. and/or front-to-side ratio.
SSL Abbreviation of SOLID-STATE LAMP.
ST Abbreviation of SINGLE THROW.
sta 1. Abbreviation of STATION. (Also stn.) 2. Ab-
breviation of STATIONARY.
stab Abbreviated form of stabilizer (see STABI-
LIZER, 4).
stability 1. The condition in which an equipment
or device is able to maintain a particular mode of
operation without deviation. 2. The condition in
which the setting or adjustment of a device re-
mains at a particular point without movement.
3. The condition in which a quantity remains
constant, with respect to time, temperature, or
another variable. 4. The ability of inks used in op-
tical character recognition to retain their color
after exposure to light or heat.
stability factor Abbreviation, SF. For a bipolar
transistor, the derivative dIc/dIco, where Ic is the
steady-state collector current and Ico is the collec-
tor cutoff current. stacked array
stabilized platform See STABLE PLATFORM.
stabilizer 1. See DAMPING DIODE. 2. See DAMP-
ING RESISTOR. 3. A device or circuit for the self- stacked-dipole antenna A stacked array of half-
regulation of current or voltage. 4. A chemical wave dipole antennas.
used to control or arrest a reaction. stacking The combination of two or more identical
stabilizing windings Auxiliary field windings used antennas, such as dipoles, Yagis, or halos, in a
to prevent speed runaway in shunt motors. STACKED ARRAY to provide enhanced forward
Stabistor Trade name for a type of voltage-regulat- gain. It can also enhance the front-to-back ratio
ing semiconductor diode. and/or front-to-side ratio. Stacking can be done
stable device A device whose characteristics and vertically or horizontally.
performance remain substantially unchanged stack pointer Abbreviation, SP. A register indicat-
with time or variations in temperature, applied ing the last data item to be entered in a stack (see
power, or other quantities. STACK, 4).
stable element 1. A component that maintains its stage A complete functional unit of a system (e.g.,
value or ratings, despite widely variable environ- amplifier stage, oscillator stage, modulator stage,
mental conditions. 2. A navigational instrument etc.).
that maintains its orientation at all times. stage-by-stage elimination See SIGNAL INJEC-
stable platform A gyro-type device used to TION.
stabilize objects in space, and to provide accurate stage gain The amplification provided by a single
information regarding attitude (pitch, roll, and stage in a system.
yaw). stage loss The loss introduced by a single stage in
stable state A stable condition, such as the high a system.
and low states of a flip-flop. The flip-flop has two stagger 1. An error in facsimile reception, occur-
stable states and will remain in one until it is ring as a constant discrepancy in the position of
switched to the other, whereupon it will then re- the received dot. 2. To deliberately tune a set of
main in that latter state until switched back to resonant circuits, especially in a bandpass filter,
the former. Compare UNSTABLE STATE. to one side or the other of the center frequency.
stack 1. A piled assembly of capacitor plates and staggered tuning The tuning of the input and out-
separating dielectric films. 2. An assembly of put circuits of a single stage, or the tuning of
staggered tuning • standard signal generator

successive stages to slightly different frequencies broadcast bands range from 54 MHz to 806 MHz
to obtain flat-top response. in several sections, designated in channels from 2
stagger tuning See STAGGERED TUNING. through 69. Also see BROADCAST SERVICE, 1.
stagger-wound coil See BASKET-WEAVE COIL standard candle See CANDELA.
and SPIDERWEB COIL. standard cell A highly refined primary cell used


. 35
( 42)