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SIGNAL—A general term used to describe any ac or dc of interest in a circuit; for example, input signal [8]
[15].
SIGNAL DISTORTION—Any unwanted change to the signal [12].
SIGNIFICANT SIDEBANDS—Those sidebands with significantly large amplitude [12].
SILICON—A metallic element which, in its pure state, is used as a semiconductor [7].
SILICON-CONTROLLED RECTIFIER (SCR)—A semiconductor device that functions as an
electrically controlled switch [7].
SINE WAVE—(1) The curve traced by the projection on a uniform time scale of the end of a rotating arm,
or vector. Also known as a sinusoidal wave [2]. (2) The basic synchronous alternating waveform for all
complex waveforms [12].
SINGLE-ENDED MIXER—See UNBALANCED CRYSTAL MIXER [18].
SINGLE LINE DIAGRAM—A diagram which shows, by means of single lines and graphic symbols, the
course of an electric circuit or system of circuits and the component devices or parts used therein [4].
SINGLE, STATIONARY-LOBE SCANNING SYSTEM—Antenna (with a single, stationary beam) that
is rotated to obtain 360-degree coverage [18].
SINK—See OUTPUT END [10].
SKIN EFFECT—The tendency for alternating current to concentrate in the surface layer of a conductor.
The effect increases with frequency and serves to increase the effective resistance of the conductor [10]
[11].
SKIP DISTANCE—The distance from a transmitter to the point where the sky wave is first returned to
earth [10].
SKIP ZONE—A zone of silence between the point where the ground wave becomes too weak for reception
and the sky wave is first returned to earth [10].
SKY WAVES—Radio waves reflected back to earth from the ionosphere [10].
SLANT RANGE—See RANGE [18].
SLIP—The difference between rotor speed and synchronous speed in an ac induction motor [5].
SLIP RINGS—Contacts that are mounted on the shaft of a motor or generator to which the rotor windings
are connected and against which the brushes ride [5]. Devices for making electric connections between
stationary and rotating contacts.
SLOPE DETECTOR—A tank circuit tuned to a frequency, either slightly above or below an FM carrier
frequency, that is used to detect intelligence [12].
SLOT—Narrow opening in a waveguide wall used to couple energy in or out of the waveguide. Also called
an aperture or a window [11].
SNAP-ACTING—Changing position quickly with the aid of a spring [3].
