18WuD2x

662 subsidiary feedback • sun battery
subsidiary feedback Feedback other than the
main feedback in a system.
subsonic frequencies Frequencies below the
range of hearing, that is, less than about 20 Hz.
Also called ULTRALOW FREQUENCIES and SUB-
AUDIBLE FREQUENCIES.
substation An intermediate electricity-distributing
location from which electrical energy is transformed
and transmitted to users within a given
geographical area.
substitution capacitor A capacitor used temporarily
in place of another of usually the same
value, as in troubleshooting. Also see CAPACI-
TOR SUBSTITUTION BOX.
substitution inductor An inductor used temporarily
in place of another of usually the same
value, as in troubleshooting. Also see INDUCTOR
SUBSTITUTION BOX.
substitution method 1. A method of measuring a
quantity (such as capacitance, inductance, or resistance)
in which the value of the unknown
quantity is determined in terms of the amount of
a standard quantity that must be removed to restore
the test circuit to its original state of balance.
2. A method of troubleshooting in which
good components are substituted for bad ones in
a circuit (see, for example, SUBSTITUTION CA-
PACITOR, SUBSTITUTION INDUCTOR, SUBSTI-
TUTION RESISTOR, SUBSTITUTION SPEAKER,
and SUBSTITUTION TRANSFORMER).
substitution resistor A resistor used temporarily
in place of another of usually the same value, as
in troubleshooting. Also see RESISTOR SUBSTI-
TUTION BOX.
substitution speaker A loudspeaker used temporarily
in place of another, as in troubleshooting.
substitution transformer A transformer used
temporarily in place of another having the same
characteristics, as in troubleshooting.
substrate A plate, wafer, panel, or disk of suitable
material on (or in) which the components of a
unit, such as an integrated or printed circuit, are
deposited or formed.
subterranean 1. Pertaining to components, systems,
or devices installed underground. It is applicable
especially to cables. 2. Pertaining to a
phenomenon, such as the propagation of electric
currents or acoustical waves, that occurs underground.
subterranean acoustical communication A method
of communication that uses low-frequency
sound waves, such as SONAR, to communicate
via conduction through earth or water.
subtracter See ELECTRONIC SUBTRACTER.
subtractive color A color formed by mixing subtractive
primary pigments.
subtractive primaries Broad-spectrum pigments
used in printing to produce a wide variety of colors
through filtering. These primaries are cyan
(blue-green), magenta (pink-red), yellow, and
sometimes black. They are used to print images
that have been filtered through additive-primary
lenses.
subtrahend In the process of subtraction, the
quantity that is subtracted from another (the
minuend) to produce the remainder or difference.
subwoofer A speaker designed to effectively reproduce
extremely low audio frequencies, in some
cases, subaudible (below 20 Hz).
successive derivatives Successive repetition of
the operation of differentiating a function, which
yields the first derivative, second derivative, and
so on to the nth derivative.
successive integration The operation of double or
triple integration.
Suhl effect A reduction in hole life that occurs in a
semiconductor material in the presence of a magnetic
field.
suite 1. A group of computer programs run successively
as a job. 2. A bundled, high-end software
package used especially in business computing.
sulfate Contraction of lead sulfate.
sulfation In a lead-acid storage cell, the formation
of disabling lead sulfate during discharge of the
cell.
sulfur Symbol, S. A nonmetallic element. Atomic
number, 16. Atomic weight 32.06.
sulfur hexafluoride A gas used as a coolant and
insulant in some power transformers.
sulfuric acid Formula, H 2 SO 4 . An acid used in dilute
solution as the electrolyte of a lead-acid battery.
This highly corrosive fluid also has many
industrial uses.
sum The result obtained by adding two or more
terms. Compare SUMMATION.
sumcheck See SUMMATION CHECK.
sum frequency 1. In an amplitude-modulated carrier,
the upper sideband frequency (i.e., the sideband
equal to the carrier frequency plus the
modulating frequency). Compare DIFFERENCE
FREQUENCY. 2. In superheterodyne operation,
an intermediate frequency equal to the signal frequency
plus the local-oscillator frequency.
summation 1. The sum of a finite number of
terms. Thus, the total resistance of n resistors
connected in series is the summation of all R (resistance)
terms. 2. A frequency equal to the sum
of two other frequencies.
summation check In computer operations, a
check carried out on a group of digits. The result
of adding the digits, and disregarding any overflow,
is a check digit that can be compared with a
standard value for the operation to verify the integrity
of data.
summer 1. See ADDER. 2. See SUMMING AMPLI-
FIER.
summing amplifier An operational amplifier
whose output is the sum, or is proportional to the
sum, of several inputs.
sun battery A set of photovoltaic cells connected in
series, parallel, or series-parallel to produce useful
output voltages and currents.