18WuD2x

664 supermodulation • surface-barrier transistor
signal amplitude swing between zero and twice
maximum for 100% modulation.
superposition In a complex wave, the manner in
which the constituent waves combine. The instantaneous
value of the complex wave is equal to
the vector sum of the instantaneous values of all
the constituent waves.
superposition theorem In a network of linear elements,
if a voltage E 1 in branch A causes a current
I 1 to flow through branch C, and if a voltage
E 2 in branch B (which might be identical with
branch A) causes a current I 2 to flow through
branch C, then E 1 in branch A and E 2 in branch
B applied simultaneously will cause a current
equal to I 1 + I 2 to flow through branch C. Compare
COMPENSATION THEOREM, MAXIMUM POWER
TRANSFER THEOREM, NORTON’S THEOREM,
RECIPROCITY THEOREM, and THEVENIN’S
THEOREM.
superpower An arbitrary term denoting very high
power. In the rating of standard broadcast stations,
it has come to signify 1,000,000 watts (one
megawatt) radio-frequency (RF) power output.
superradiance In a laser, a rapid increase in intensity
of fluorescent-line emission with increasing
excitation power.
superregenerative circuit A regenerative detector
circuit in which regeneration is periodically increased
almost to the point of oscillation, then decreased.
This quenching action takes place at a
supersonic rate (typically at 50 or 100 kHz) so
that the quenching is inaudible. The result is that
much more regeneration is afforded, without the
detector going into oscillation, than is possible by
simply increasing the regeneration manually. An
extremely sensitive detector is the result.
supersaturated solution A solution that contains
more solute than it normally would hold. Supersaturated
solutions are obtained through special
techniques and are extremely unstable. Compare
SATURATED SOLUTION. Also see SOLUTE; SO-
LUTION, 1; and SOLVENT, 2.
superscript A small number or letter written to the
upper right of another number or letter, the
BASE, to indicate the power to which the base
must be raised. Example: 10 5 , e x , y 2 . Also called
EXPONENT. Compare SUBSCRIPT.
supersensitive relay A relay that operates with a
current of less than one milliampere, or with a
voltage of less than one millivolt.
supersonic flow In a gas or liquid, movement of
the medium at a speed greater than the speed of
sound in that medium. Supersonic flow results in
a greatly increased resistance or drag because of
shock waves that form in the medium.
supersonic frequency See ULTRASONIC FRE-
QUENCY.
supersonics See ULTRASONICS.
supervised line In a security system, a wire or foil
strip that carries electrical current. If the current
changes in such a line, an alarm is actuated.
supervisor 1. In a computer, a set of routines that
oversees the operation of the system. The supervisor
routines are coordinated by the central processing
unit. 2. The execution of such a set of
routines. 3. A microcomputer that oversees the
operation of a security system.
supervisory circuit In a security system, a link
between a sensor and the central computer or
control device. This link can be via electric current
through a wire or cable, but other methods
can be used, such as fiberoptics, line-of-sight optics,
infrared, ultrasonic, or radio.
supply 1. See CURRENT SUPPLY. 2. See POWER
SUPPLY. 3. See VOLTAGE SUPPLY.
supply current Alternating or direct current available
for operating a circuit, device, or system.
supply frequency The frequency of an alternatingcurrent
power supply.
supply power The maximum power that can be reliably
delivered by an alternating-current or
direct-current power supply.
supply reel In a reel-to-reel tape recorder or player,
the reel that is initially full, and that gradually
empties as the tape moves through the machine.
supply voltage The voltage of an alternating-current
or direct-current power supply.
suppressed carrier A carrier that has been canceled
or filtered out of a carrier/sideband combination.
suppressed-carrier double sideband See DOU-
BLE-SIDEBAND and SUPPRESSED CARRIER.
suppressed-zero instrument A meter or graphic
recorder in which the zero point is off-scale or upscale,
but has been brought to scale-zero by
means of mechanical adjustment or use of a
bucking voltage.
suppressor 1. A filter used to suppress radio interference.
2. See AUTOMATIC NOISE LIMITER. 3.
See SPARK SUPPRESSOR. 4. In a pentode vacuum
tube, a gridlike element between the screen
grid and the plate, used to suppress secondary
emission. Also see GRID, 2 and PENTODE.
suppressor circuit The circuit associated with the
suppressor electrode of a vacuum tube.
suppressor diode A semiconductor diode used to
prevent inductive kickback in circuits, to eliminate
or reduce transients, or to prevent arcing between
make-and-break contacts.
suppressor grid See SUPPRESSOR, 4.
suppressor modulation A method of modulation
in which a modulating voltage is superimposed
on the suppressor voltage of a pentode radiofrequency
power amplifier tube.
suppressor pulse A pulse that prevents electron
flow.
surface analyzer A device designed for the measurement
of surface flatness or uniformity.
surface-barrier diffused transistor See MICRO-
ALLOY DIFFUSED TRANSISTOR.
surface-barrier transistor Abbreviation, SBT. A
pnp transistor made by means of electrolysis and
electroplating: Two fine streams of indium sulfate