Page 44 - The Illustrated Dictionary of Electronics

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Anderson bridge • angle of beam 29

anechoic chamber An enclosure that does not re-
Anderson bridge An ac bridge circuit with six flect sound waves that approach its walls. Such a
impedances, permitting the value of an unknown chamber is used to test certain audio devices.
inductance to be determined in terms of a stan- anemograph An electromechanical device that
dard capacitance. produces a recording of wind speed versus time.
Generally, it consists of an ANEMOMETER con-
nected to a PEN-AND-INK RECORDER via a suit-
able electronic interface.
anemometer An instrument that measures or
indicates wind speed, or speed and direction (ve-
locity).
angel 1. An extraneous image, usually of short du-
ration, on a cathode-ray-tube (CRT) display. The
term applies particularly to anomalies in a radar
image caused by low-atmospheric reflection,
birds, or other mobile objects. 2. Air-deployed
metallic debris, also known as chaff, designed to
create radar echoes as a decoy or diversion tactic.
angle jamming A radar jamming technique in
which the return echo is jammed with a signal
containing improper azimuth or elevation angle
components.
angle modulation Variation of the angle of a sine-
wave carrier in response to the modulating
source, as in FREQUENCY MODULATION and
PHASE MODULATION.
angle noise In radar reception, the interference re-
AND gate 1. AND circuit. 2. In a TV receiver, an sulting from variations in the angle at which an
AND circuit that holds the keyed-AGC signal off echo arrives from the target.
until a positive horizontal flyback pulse and a angle of arrival The angle which the line of propa-
horizontal sync pulse appear simultaneously at gation of an incoming radio wave makes with the
the input. surface of the earth. Compare ANGLE OF DE-
android A sophisticated robot built in humanoid PARTURE.
form. Usually, it propels itself by rolling on angle of azimuth The horizontal angle between
wheels or on a track drive. A rotatable head con- the viewer and object or target, usually measured
tains position sensors, a machine vision system, clockwise from north.
and/or a machine hearing system. Mechanical angle of beam The angle enclosing most of the
arms are equipped with end effectors to perform transmitted energy in the radiation from a direc-
various tasks. The most advanced androids have tional antenna. It is usually measured between
self-contained computer control systems. the half-power points in the main lobe of the di-
anechoic Pertaining to the absence of echoes. Ex- rectional pattern. This angle can be measured in
amples: ANECHOIC CHAMBER, anechoic enclo- the horizontal (azimuth) plane or in the vertical
sure, or anechoic room. (elevation) plane.