18WuD2x

automatic interrupt • automatic secure voice communications 51
automatic interrupt A program interruption
caused by hardware or software acting in response
to some event independent of the program.
automatic level compensation See AUTOMATIC
GAIN CONTROL.
automatic level control Abbreviation, ALC. 1. A
circuit that adjusts the input gain of a magnetictape
recording device to compensate for changes
in the loudness of the sound reaching the microphone.
2. A form of AUTOMATIC GAIN CONTROL
used in single-sideband (SSB) radio transmitters
to maintain linearity while increasing the level of
the average power relative to the peak power.
automatic line feed In the digital transmission of
printed matter, the automatic insertion of a line
feed (LF) character immediately following every
carriage return (CR) character.
automatic modulation control Abbreviation,
AMC. In a frequency-modulated (FM) radio transmitter,
a form of AUTOMATIC GAIN CONTROL
that regulates the gain of the audio amplifiers to
compensate for fluctuating audio input amplitude.
This prevents overdeviation while optimizing
signal intelligibility.
automatic noise limiter Abbreviation, ANL. Any
of several circuits for clipping noise peaks exceeding
a predetermined maximum receivedsignal
amplitude.
automatic phase control In a color television (TV)
receiver, a circuit that synchronizes the burst signal
with the 3.58-MHz color oscillator.
automatic pilot An electronic device, often computer-controlled,
that automatically keeps a ship,
airplane, or space vehicle on course.
automatic polarity In an electronic metering device,
a means of automatically switching the input
polarity of the instrument when the input
signal polarity is shifted. Also called bipolar operation.
automatic programming See AUTOMATIC COD-
ING.
automatic protective device A circuit or device
(such as a fuse, circuit breaker, limiter, or regulator)
that protects another circuit or device by
automatically removing, reducing, or increasing
the current or voltage during overload or underload.
automatic radio compass See AUTOMATIC
DIRECTION FINDER.
automatic ranging In a metering device, the automatic
adjustment or optimization of the full-scale
range to compensate for large changes in the input
parameter.
automatic regulation 1. Voltage regulation. In a
power supply, the automatic holding of the output
voltage to a constant value, despite variations in
the input voltage or load resistance. 2. Current regulation.
In a power supply, the automatic holding
of the output current to a constant value, despite
variations in the input voltage or load resistance.
automatic relay The relaying of messages automatically
from one station to another via intermediate
points, without the need for human
operators.
automatic repeater station A station that receives
signals and simultaneously retransmits
them, usually on a different frequency.
automatic reset 1. The self-actuated restoration
of a circuit or device to a given state (e.g., the
state of rest). 2. A circuit or device that restores
another circuit or device to a given state.
automatic scanning 1. The automatic (usually
repetitive) tuning or adjustment of a circuit or
system throughout a given frequency range. In a
radio receiver, the system can be programmed to
pause or stop at occupied channels, passing over
vacant ones; or it can be programmed to pause or
stop at vacant channels, passing over occupied
ones. 2. The repetitive sweep of a cathode-raytube
(CRT) electron beam.
automatic scanning receiver Also called
PANORAMIC RECEIVER. A radio receiver that is
automatically tuned (usually repetitively) over a
frequency band. Such a receiver either homes in
on a signal when one is found, or displays on a
cathode-ray-tube (CRT) screen the distribution of
signals in the band.
automatic secure voice communications A wideband
and narrowband voice-digitizing application