18WuD2x

auroral propagation • automatic chrominance control 49
circuit is at a latitude less than 35 degrees north
or south of the equator. Auroral propagation can
take place at frequencies well above 30 MHz. It is
characterized by deep, rapid fading and random
phase modulation of reflected signals.
auroral reflection The return of electromagnetic
waves that have been beamed toward an aurora.
Most often observed between 15 MHz and 150
MHz.
authorized access switch A device that disables a
security system in a defined region or volume so
that authorized personnel can enter without triggering
an alarm condition.
authorized channel The carrier frequency or band
assigned to a transmitting station by a licensing
authority. Also see RADIO SPECTRUM.
autoalarm A device that is actuated from a received
signal to alert a radio or computer network
operator to the existence of a message.
autobaud 1. In digital communications, a function
that allows the equipment to adjust itself to the
speed of the terminal. 2. Any digital communications
equipment capable of automatically adjusting
to the speed of the terminal.
autocondensation The application of radiofrequency
(RF) energy to the human body for
medical purposes. The living organs serve as an
impedance or load, across which the RF is applied.
autoconduction The application of radiofrequency
(RF) currents into the body, by placing
the living organ inside a coil and supplying the
coil with RF. Used for medical purposes.
autocorrelation function A measure of the similarity
between delayed and undelayed versions of
a signal, expressed as a delay function.
autodyne reception Radio reception of cw signals
by means of an oscillating detector. This is in
contrast to heterodyne reception, in which a local
oscillator (LO) generates an audio beat note with
the cw signal in a separate detector.
autoionization A two-phase process of atomic ionization.
The atom is excited beyond its ionization
potential, and then it is allowed to deionize, causing
the emission of an electron. The result is a
positively charged atom (positive ion).
automated communications The transfer of data
without the use of operating personnel; generally
done with computers connected to communications
equipment.
automated guided vehicle Abbreviation, AGV. A
robot cart that runs without a driver. It uses an
electric engine and is guided by the magnetic field
produced by a current-carrying wire embedded in
the floor or pavement. Alternatively, the robot can
run on a track.
automated home A residence in which many, or
most, of the routine chores are done by computers
and/or robots. Examples of such tasks are
dishwashing, doing the laundry, mowing the
lawn, blowing snow, and vacuuming the floors.
automated integrated manufacturing system
Acronym, AIMS. An assembly line or factory that
uses robots, often controlled by one or more computers,
to perform specific tasks that result in the
production of various hardware items.
automatic Self-regulating, independent of human
intervention. Some periodic adjustment might be
needed.
automatic base bias A method of obtaining base
bias in a bipolar transistor, where a resistor
develops a voltage drop because of the current
flowing through it. The resistor is usually placed
in the emitter circuit, raising the emitter above
ground potential.
automatic bass compensation Also called bass
boost. In audio high-fidelity systems, a resistorcapacitor
(RC) network that increases the relative
amplitude of the bass at low volume levels. This
compensates for the ear’s inefficiency at low frequencies.
The function can be automatically actuated
by the setting of the volume control, or it
can be switched manually on and off.
automatic bias In an amplifier, dc base/gate/
grid bias obtained from the voltage drop produced
by collector/drain/plate current flowing through
a resistor common to the input and output. This
resistor is usually shunted by a capacitor and
placed in the emitter/source/cathode circuit.
automatic brightness control A circuit that uses
the same principles used in AUTOMATIC GAIN
CONTROL (AGC) to hold steady the average
brightness of a television (TV) picture.
automatic carriage Typewriters, automatic key
punches, and other devices that can control automatically
the spacing and feeding of paper,
cards, and forms.
automatic check 1. In a digital computer, the automatic
inspection of operation and performance
by a self-contained subsystem. 2. The circuit or
device for performing this inspection.
automatic chrominance control In a color television
(TV) receiver, a subcircuit that controls the