18WuD2x

124 coherent bundle • cold resistance
coherent bundle A bundle of optical fibers, such
that the individual fibers are in the same relative
positions at either end of the bundle.
coherent carrier A carrier that agrees in frequency
and phase with a reference signal.
coherent electroluminescent device See LASER
DIODE.
coherent light Visible light in which the phase relationship
between successive waves is such that
the beam consists of parallel rays that provide a
high concentration of energy. Also see LASER.
coherent-light radar See COLIDAR.
coherent oscillator In a radar system, an oscillator
that provides a COHERENT REFERENCE.
coherent-pulse operation Pulse operation characterized
by a fixed phase relationship between
pulses.
coherent radiation Radiation characterized by
COHERENCE.
coherent reference A stable reference frequency
with which other signals are phase locked for coherence.
coherent transponder A transponder in which the
frequency and phase of the input and output signals
have a fixed relationship.
coil A long conductor or group of conductors wound
into a tight helical package, often in several layers
on a cylindrical form. This takes advantage of the
resulting concentration of magnetic flux, maximizing
the inductance that can be obtained in a component
of limited physical size. Further increases
in inductance can be realized by the use of ferromagnetic
core materials. See also INDUCTOR.
coil antenna See LOOP ANTENNA.
coil checker An alternating-current (ac) meter or
simple bridge for checking inductors. Such instruments
usually only indicate inductance values,
but some list readings of resistance or
approximate inductor Q factor.
coil dissipation The power wasted in a coil as
heat. Generally, this dissipation or loss is proportional
to the resistance of the coil, and to the
square of the current passing through the coil.
coil form The insulating support around which an
air-core coil is wound.
coil loading The insertion of one or more inductors
into a transmission line or antenna element, for
the purpose of impedance matching, alteration of
the resonant frequency, or both.
coil magnification factor The Q factor of an inductor.
Generally given by the ratio X L /R L , where
X L is the inductive reactance of the coil in ohms,
and R L is the resistance of the coil in ohms.
coil neutralization See INDUCTIVE NEUTRALIZA-
TION.
coil resistance The resistance of a coil (inductor),
as distinct from its reactance. It is almost entirely
the result of ohmic loss in the wire from which
the coil is manufactured.
coilshield A metal can designed to provide efficient
electrostatic and electromagnetic shielding of a
coil, preventing unwanted inductive coupling to
other components.
coincidence The simultaneous occurrence of two
or more signals. Compare ANTICOINCIDENCE.
coincidence amplifier An amplifier that delivers
an output signal only when two or more input signals
occur simultaneously.
coincidence circuit See AND CIRCUIT.
coincidence counter A circuit or device, such as a
gate, that delivers an output pulse only when two
or more input pulses occur simultaneously; the
output pulses go to a device that counts them.
coincidence detector See AND CIRCUIT.
coincidence gate See AND GATE.
coincident-current selection Selection of a magnetic
core (in a core memory or similar device) by
applying two or more currents simultaneously.
coin shooting Searching for coins and similar
small, buried metallic objects using a METAL LO-
CATOR.
coke A porous material obtained from the destructive
distillation of coal. It is valued for the
production of carbon components for electronics,
such as dry-cell electrodes and motor
brushes.
cold 1. Pertaining to an electrical circuit, component,
or terminal that is at ground potential. 2. A
term denoting a bad solder joint. 3. Pertaining to
an unheated electrode or element. See COLD
CATHODE.
cold alignment The alignment of a tracking system
(especially of its tuned circuits) when the system
is not in operation, as when transistor power
is off. Also called QUIET ALIGNMENT.
cold cathode 1. In an electron tube, a cathode that
emits electrons without being heated. 2. A cathode
electrode operated at a temperature below
ambient temperature.
cold chamber An enclosure in which electronic
equipment can be tested at selected, precise low
temperatures. Compare OVEN.
cold flow The (usually gradual) change in the dimensions
of a material, such as plastic in a
molded part.
cold junction In a thermocouple system, an auxiliary
thermocouple connected in series with the
hot thermocouple, and immersed in ice or operated
at ambient temperature.
cold light Light produced without significant heat,
as from the ionization of a gas by a high voltage
(as in neon bulbs and fluorescent lamps), or by
electroluminescence, bioluminescence, cathodoluminescence,
or a similar phenomenon.
cold pressure welding Welding sometimes used in
the fabrication of electronic equipment, in which
the metal parts to be joined are pressed together
tightly to the point of deformation, whereupon
they become welded.
cold resistance The resistance of an unheated
electronic component. Compare HOT RESIS-
TANCE.