18WuD2x

324 G-string antenna • Gunnplexer
from the first initial of Dr. George Groubau, inventor
of the device, and the stringy appearance
of the wire.
GTO Abbreviation of GOTO.
guard band A narrow unoccupied band of frequencies
at the upper and lower limits of an assigned
channel; its purpose is to prevent adjacentchannel
interference by ensuring adequate
separation between channels.
guard circle On a phonograph disk, an inner
groove that prevents collision of the pickup with
the spindle at the center of the disc.
guard circuit An auxiliary circuit added to an
alternating-current bridge to compensate for the
effects of stray capacitance in the bridge arms.
One of its several forms is the WAGNER
GROUND.
guarded input An input-terminal arrangement in
which one terminal, maintained at the proper potential,
shields the entire input-terminal combination.
guarding
A method of short-circuiting a leakage
current to ground. On a printed-circuit board,
guarding is usually accomplished by the use of a
large conducting foil surface near critical components.
guard relay A relay that ensures that only one
linefinder will be connected to a line circuit when
other line relays are in operation.
guard ring A metal ring (or other configuration)
surrounding, but separate from, a charged body
or terminal, for the purpose of evenly distributing
the electric charge over the latter’s surface.
guard shield A shield that encloses the input circuit
of an amplifier or instrument.
guard terminal In a GUARDED INPUT, the terminal
that shields the combination.
guard wire A grounded wire that is intended to
catch and ground a broken high-voltage line.
Gudden-Pohl effect The tendency of an ultraviolet
irradiated phosphor to glow momentarily when
subjected to an electric field.
GUI Acronym for GRAPHICAL USER INTERFACE.
Can be spelled out or pronounced “gooey.”
guidance Electronic control of the path or course
of a robot, missile, or other vehicle.
guidance system The complete electromechanical
system for control of a robot, missile, or other vehicle.
It consists of hardware and software. The
hardware includes beacons, sensors, drive systems,
rockets, etc. The software interprets data
from, and transmits commands to, the hardware.
The nature of the hardware and software depend
on the application.
guidance tape In a guided missile, a magnetic tape
containing computer instructions for steering the
missile in a designated course.
guide See WAVEGUIDE.
guide connector See WAVEGUIDE CONNECTOR.
guided missile A missile whose progress to a target
is controlled electronically by signals from a
control station or by sensing equipment aboard
the missile.
guided propagation A form of radio-wave propagation
in which air masses of different temperatures
or humidity levels cause refraction and/or reflection
of electromagnetic waves, guiding signals
over long distances with very little attenuation.
Commonly observed at very-high and ultra-high
frequencies.
guide elbow See WAVEGUIDE ELBOW.
guide flange See WAVEGUIDE FLANGE.
guide gasket See WAVEGUIDE GASKET.
guide junction See WAVEGUIDE JUNCTION.
guide load See WAVEGUIDE LOAD.
guide slot See KEYWAY.
guide wavelength See WAVEGUIDE WAVE-
LENGTH.
Guillemin effect The tendency for a strip of ferromagnetic
material to become straight in a strong
magnetic field. This is a form of MAGNETO-
STRICTION.
Guillemin line In radar operations, a special
pulse-forming network for controlling modulation
pulse duration.
guillotine capacitor A variable capacitor in which
a sliding (instead of rotary) plate moves between
two stator plates. Its name results from its resemblance
to the infamous beheading apparatus.
gulp Several bytes of digital information.
gun See ELECTRON GUN.
Gunn diode A semiconductor diode that can operate
as an oscillator in the ultra-high-frequency
(UHF) and microwave parts of the radio spectrum.
Oscillation takes place as a result of a negative-resistance
effect in which, within a certain
range of applied voltages, the current decreases
as the voltage increases. The device is not particularly
efficient. Only a small fraction of the input
power results in useful signal output. The frequency
and oscillation stability are sensitive to
changes in temperature and bias voltage. See
GUNN EFFECT, NEGATIVE RESISTANCE.
Gunn effect A semiconductor phenomenon named
after J. Gunn of International Business Machines
(IBM) who first observed and studied it in the
1960s. In certain types of diodes having a negative-resistance
characteristic, oscillation occurs
when the applied voltage is within a certain
range. See GUNN DIODE, NEGATIVE RESIS-
TANCE.
Gunn-effect circuit Any circuit exploiting the
Gunn effect, especially a GUNN OSCILLATOR.
Gunn oscillator A discrete semiconductor microwave
oscillator using a GUNN DIODE.
Gunnplexer A microwave transmitter consisting of
a Gunn-diode oscillator connected to a horn antenna.
Usually, the entire device is a compact,
self-contained unit. The output power is low.
When the device is placed at the focal point of a
large dish antenna with the horn pointing toward
the dish reflector (conventional dish feed), consid-