18WuD2x

120 closed-circuit security system • CMR
interconnected so that a disturbance anywhere in
the circuit will result in an alarm signal pinpointing
the location of the disturbance.
closed-circuit signaling Signaling accomplished
by raising or lowering the level of a signaling current
flowing continuously in a circuit.
closed-circuit television Abbreviation, CCTV. A
usually in-plant television system, in which a
transmitter feeds one or more receivers through a
cable.
closed core A magnetic core generally constructed
in an “O” or “D” configuration to confine the magnetic
path to the core material. Compare OPEN
CORE.
closed-core choke A choke coil wound on a
CLOSED CORE. Also called CLOSED-CORE IN-
DUCTOR.
closed-core choke
closed-core transformer
a CLOSED CORE.
Primary
Laminated core
closed-core transformer
A transformer wound on
Secondary
closed loop 1. The feedback path in a self-regulating
control system. An oscillator, for example, is a
closed-loop amplifier. 2. A loop within a program
that would continue indefinitely, except for an external
exit command.
closed-loop bandwidth The frequency at which
the gain of a closed-loop circuit (see CLOSED
LOOP, 1) drops 3 decibels from the direct-current
or midband value.
closed-loop control system A control system in
which self regulation is obtained by means of a
feedback path (see CLOSED LOOP). An example
is a voltage regulator, in which a rise in output
voltage is fed back to the input. This changes the
input voltage and reduces the output voltage to
its correct value. Compare OPEN-LOOP CON-
TROL SYSTEM.
closed-loop input impedance The input impedance
of an amplifier that has feedback.
closed-loop output impedance The output impedance
of an amplifier that has feedback.
closed-loop voltage gain The voltage gain of an
amplifier that has feedback.
closed magnetic circuit A magnetic circuit in
which the flux is uninterrupted, as in a ferromagnetic
core, which has no air gap. Also see
CLOSED CORE.
closed subroutine In a digital computer program,
a subroutine that can be accessed and left by
branch instructions, such as GOSUB and RE-
TURN in the high-level language BASIC.
close-spaced array A beam antenna in which the
elements (radiator, director, and reflector) are
spaced less than a quarter-wavelength apart.
close-talk microphone A microphone that must
be placed close to the mouth. Such a microphone
is less susceptible to background noises than an
ordinary microphone, and is useful in environments
where the ambient noise level is high.
closing rating A specification for closure conditions
in a relay, including duty cycle and contact
life (total guaranteed closures before contact
failure).
closure 1. The act of closing or being closed (e.g.,
switch closure or relay closure). 2. Circuit completion
(i.e., the elimination of all discontinuities).
cloud The mass of electrons constituting the space
charge in a vacuum tube.
cloverleaf antenna An omnidirectional transmitting
antenna in which numerous horizontal,
four-element radiators (stacked vertically, a quarter-wavelength
apart) are arranged in the shape
of a four-leaf clover.
C/L ratio See LC RATIO.
clutter Extraneous echoes that interfere with the
image on a radar display.
clutter gating In radar operations, a switching
process that causes the normal video to be displayed
in regions free of clutter, and the video indicating
target movement to be displayed only in
cluttered areas.
Cm Symbol for CURIUM.
cm Abbreviation of CENTIMETER.
c.m. Abbreviation of CIRCULAR MIL.
cm 2 Abbreviation of square centimeter.
cm 3 Abbreviation of cubic centimeter.
C max Abbreviation of maximum capacitance.
C meter See CAPACITANCE METER.
C min Abbreviation of minimum capacitance.
CML Abbreviation of CURRENT-MODE LOGIC.
CMOS Abbreviation of COMPLEMENTARY METAL-
OXIDE SEMICONDUCTOR.
CMR See COMMON-MODE REJECTION.