Page 82 - The Illustrated Dictionary of Electronics

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beacon • beam parametric amplifier 67

scanning infrared laser. The robot controller de- television (TV) camera tube, the lining-up of the
termines the distance to any given reflector by electron beam so that it is perpendicular to the
measuring the time required for the laser beam to target. 3. In a cathode-ray tube, the positioning of
return. In this way, two mirrors can allow the the electron rays so that they converge properly
robot to locate its position in two dimensions; on the screen, regardless of the deflection path.
three mirrors can facilitate position determina- beam angle In the radiation from an antenna, the
tion in three-dimensional space. direction of most intense radiation, the side limits
beacon direction finder A direction finder using a of which are determined by the points at which
signal received from a beacon station. the field strength drops to half the value in the
beacon receiver A receiver that is specially principal direction.
adapted for the reception of beacon signals (see beam antenna 1. A multielement directional an-
BEACON, 1 and 3). tenna, consisting of a half-wave driven dipole and
beacon station 1. A station broadcasting beacon one or more parasitic elements. See YAGI AN-
signals (see BEACON, 1 and 3) for direction find- TENNA. 2. Any directional antenna used for
ing, navigation, and/or determination of radio- transmitting and receiving radio-frequency (RF)
wave propagation conditions. 2. Sometimes, a signals.
radar transmitting station. beam bender 1. In a television (TV) picture tube,
beacon transmitter A transmitter specially the ion-trap magnet. 2. Deflection-plate correc-
adapted for the transmission of beacon signals tion device or circuit.
(see BEACON, 1 and 3). beam bending Deflection of an electron beam by
bead 1. A small ferromagnetic ring that is used as electric or magnetic fields.
a passive decoupling choke by slipping it over the beam blanking See BLANK, 2.
input power leads of a circuit or stage, or around beam convergence The meeting, at a shadow-
a coaxial transmission line. 2. A magnetic mem- mask opening, of the three electron beams in a
ory element in a ferrite-core matrix. three-color television picture tube. See BEAM
beaded coax A low-loss, coaxial transmission line, ALIGNMENT, 3.
in which the inner conductor is separated from beam coupling A method of producing an alternat-
the outer conductor by means of spaced dielectric ing current between two electrodes by passing a
beads. density-modulated beam of electrons between the
beaded support A plastic or dielectric bead that is electrodes. This, in effect, demodulates the elec-
used to support the inner conductor of an air- tron beam, recovering the information.
insulated transmission line of coaxial construction. beam crossover Either of the half-power points
bead thermistor A thermistor consisting essentially in the beam of a directional antenna, usually in
of a small bead of temperature-sensitive resistance the horizontal plane. The reference point is con-
material into which two leads are inserted. sidered to be the direction of maximum radia-
beam 1. The more-or-less narrow pattern of radia- tion.
tion from a directional antenna. 2. A directional beam current The current represented by the flow
antenna—especially a YAGI ANTENNA. 3. The of electrons in the beam of a cathode-ray tube.
stream or cloud of electrons emitted by the cath- beam cutoff In an oscilloscope or television picture
ode in an electron tube—especially a BEAM tube, the complete interruption of the electron
POWER TUBE. beam, usually as a result of highly negative con-
beam alignment 1. The lining-up of a directional trol-grid bias.
transmitting antenna with a directional receiving beam deflector A deflection plate in an oscillo-
antenna for maximum signal transfer. 2. In a scope tube.
beam efficiency In a cathode-ray tube, the ratio of
the number of electrons generated by the gun to
the number reaching the screen. The efficiency is
high in electromagnetic-deflection tubes and
lower in electrostatic-deflection tubes.
beam lead In an integrated circuit, a relatively
thick and strong lead that is deposited in contact
with portions of the thin-film circuit. It provides
stouter connections than continuations of the
thin film would provide.
beam-lead isolation In an integrated circuit, re-
duction of distributed capacitance and other in-
teraction through use of beam leads.
beam modulation See INTENSITY MODULATION.
beam parametric amplifier A PARAMETRIC AM-
PLIFIER in which the variable-reactance compo-
beam alignment nent is supplied by a modulated electron beam.