Page 51 - The Illustrated Dictionary of Electronics

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36 antiphase • A plus

antiphase The property of being in phase opposi- aperture 1. The larger, normally open end of a
tion (180 degrees out of phase). horn antenna or horn loudspeaker. 2. An opening
antipincushioning magnets In some television in an opaque disk or mask that passes a prede-
(TV) receivers, a pair of corrective magnets in the termined amount of light or other radiant energy.
deflection assembly on the picture tube that elim- 3. The portion of a directional antenna through
inate pincushion distortion (disfigurement of the which most of the radiated energy passes.
raster so that it resembles a pincushion—a rect- aperture angle For an antenna or telescope or mi-
angle with its sides bowed in). croscope, the half angle formed by the radius of
antiproton A subatomic particle with a mass equal the detecting instrument, as viewed from the
to that of the proton, but with opposite electrical source.
charge.
antiquark An ANTIPARTICLE of a QUARK.
antirad substance A material that protects against
damage caused by atomic radiation.
antiresonance 1. Parallel resonance. 2. The con-
dition of being detuned from a resonant fre-
quency.
antiresonant circuit See PARALLEL-RESONANT
CIRCUIT.
antiresonant frequency 1. The resonant fre-
quency of a parallel-resonant circuit. 2. In a
piezoelectric crystal, the frequency at which
impedance is maximum (as in a parallel-resonant aperture antenna An antenna whose beamwidth
circuit). depends on the size of a horn, reflector, or lens.
antisidetone Pertaining to the elimination in tele- aperture compensation In a television (TV) cam-
phone circuits of interference between the micro- era, the minimizing of APERTURE DISTORTION
phone and earphone of the same telephone. by widening the video-amplifier passband.
antistickoff voltage The low voltage applied to the aperture distortion In a television (TV) camera
coarse synchro control transformer rotor winding tube, a form of distortion that occurs when the
in a dual-speed servo system to eliminate am- scanning beam covers several mosaic elements
biguous behavior in the system. simultaneously. This condition, caused by exces-
antitransmit/receive switch Abbreviated ATR. In sive beam thickness, results in poor image reso-
a radar installation, an automatic device to pre- lution.
vent interaction between transmitter and re- aperture mask In a three-gun color picture tube, a
ceiver. thin, perforated sheet mounted behind the view-
antivirus program A computer program or utility ing screen to ensure that a particular color phos-
designed to detect and eliminate viruses and Tro- phor will be excited only by the beam for that
jan horses in a computer system. color. Also called shadow mask.
antivoice-operated transmission Radio commu- aperture synthesis In telescopes, a method of ob-
nications that use a voice-activated circuit as a taining high resolution using several small anten-
transmitter interlock during reception on the nas separated by great distances. The small
companion receiver. antennas are moved around to simulate the re-
apc 1. Abbreviation of automatic picture control. 2. solving power of a much larger antenna that
Abbreviation of AUTOMATIC PHASE CONTROL. would, in practice, be impossible or impractical to
aperiodic Characterized by a lack of predictable construct.
repetitive behavior. For example, the sferics or aphelion 1. The point at which a solar-orbiting
“static” electromagnetic interference caused by satellite attains its highest altitude. It occurs
lightning. once for every complete orbit. At this point, the
aperiodic current The unidirectional current that satellite travels slower than at any other point in
follows an electromagnetic disturbance in an LCR the orbit. 2. The altitude, measured from the
circuit, in which R is equal to or higher than the sun’s surface or the sun’s center, of a solar-
critical circuit resistance. orbiting satellite at its most distant point.
aperiodic damping Damping of such a high degree APL Abbreviation for A Programming Language. A
that the damped system, after disturbance, high-level computer language designed for ease of
comes to rest without oscillation or hunting. use, and characterized by the requirement for a
aperiodic discharge A discharge in which current special character set.
flowing in an LCR circuit is unidirectional, rather apl 1. Abbreviation of average picture level. 2. Ab-
than oscillatory. For this condition, 1/LC is less breviation of automatic phase lock.
2
2
than or equal to R /4L . A plus Also, A+. The positive terminal of an A bat-
aperiodic function A nonrepetitive function (e.g., tery. Also, pertaining to the part of a circuit con-
a hyperbolic trigonometric function). nected to that terminal.