18WuD2x

source impedance • special character 645
source impedance 1. The impedance of a generator
in a circuit. 2. The impedance of the source
electrode of a field-effect transistor.
source language A computer programming language
from which is derived (by a compiler) the
machine (object) language on which the computer
operates.
source program A computer program written in a
source language.
south magnetic pole The south pole of the equivalent
bar magnet constituted by earth’s magnetic
field (see EARTH’S MAGNETIC FIELD). The south
magnetic pole lies close to the geographic south
pole. Compare NORTH MAGNETIC POLE.
south-seeking pole Symbol, S. The so-called
south pole of a magnet. When a bar magnet is
suspended horizontally, this pole points to
earth’s south magnetic pole. Compare NORTH-
SEEKING POLE.
SP Abbreviation of STACK POINTER.
sp 1. Abbreviation of single pole. 2. Abbreviation of
special.
space-charge field 1. The electric field existing
within a group of charged particles. 2. The electric
field existing in a plasma.
space diversity See DIVERSITY RECEPTION.
space-diversity reception See DIVERSITY RE-
CEPTION.
space division A method of data transfer in which
different paths are used for the transmission of
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 crystal
and having a shape that is characteristic of a
particular crystalline material.
spacer An insulating rod or bar that serves to hold
apart the conductors of a two-wire, four-wire, or
coaxial air-dielectric transmission line.
space suppression Following the printing of a line
by a printer, the prevention of normal paper travel.
space-time-space switch Abbreviated STS switch
or STSS. A large switching array with two space
switch blocks and a time switch block between
them.
space wave One of the components of an electromagnetic
ground wave. The space wave, unlike
the surface wave, is not earth-guided. It has two
components: the direct wave and the groundreflected
wave.
spaghetti Slender, varnished-cambric tubing used
as slipover insulation for wires and busbars.
span On an instrument scale, the difference between
the highest value and the lowest value.
spark See ELECTRIC SPARK.
spark absorber 1. See SPARK SUPPRESSOR. 2.
See KEY-CLICK FILTER.
spark coil A small induction coil. Its name is derived
from its initial purpose of supplying the
high voltage for spark plugs in gas engines.
spark energy The energy dissipated by an electric
arc or spark.
spark gap A device consisting essentially of two
metal points, tips, or balls that are separated by a
small air gap. A high voltage applied to the electrodes
causes a spark to jump across the gap.
sparking distance The maximum separation of
the electrodes of a spark gap at which a given
voltage will produce a spark.
sparking voltage The lowest voltage that will
cause a spark to jump across a gap of a given
width.
spark killer See SPARK SUPPRESSOR.
sparkover A discharge in air, a vacuum, or a dielectric.
It is characterized by sparking between
electrodes in the medium.
spark plate In some automobile radios, a noiseinterference-eliminating
bypass capacitor in
which the chassis is one plate.
spark-plug suppressor A small resistive device
connected in series with a spark plug to suppress
electrical noise arising from the ignition in an internal
combustion engine.
spark quencher See SPARK SUPPRESSOR.
spark suppressor A resistor, capacitor, and/or
diode used to eliminate or minimize sparking between
make-and-break contacts.
spark suppressor
To keyed
circuit
spark-suppressor diode See SUPPRESSOR
DIODE.
spatial distribution The three-dimensional directional
pattern of a transducer (such as an antenna,
microphone, or speaker).
spc 1. Abbreviation of silicon point contact. 2. Abbreviation
of silver-plated copper.
SPDT Abbreviation of SINGLE-POLE/DOUBLE-
THROW (switch or relay).
speaker See LOUDSPEAKER.
speaker damping See DAMPED LOUDSPEAKER.
speaker-level audio In a sound reproduction system,
radio receiver, or other audio circuit, an audio-frequency
signal of sufficient amplitude to
drive a speaker or speaker system directly, without
the need for additional amplification.
speaking arc A method of modulated-light transmission.
An electric arc is modulated by audiofrequency
signals.
special character A printed, displayed, or encoded
character other than a numeral or letter, such as