18WuD2x

control circuit 1. A circuit in which one signal or
process is made to control another signal or procontrast
• controlling file 145
max
Output level
min
low
Bass
Midrange
Frequency
contour
Treble
high
cessive contrast, a “hard” picture. 2. In optical
character recognition, the degree to which a character
is distinguishable from its background.
contrast control A potentiometer for adjusting the
gain of the video in a television receiver or cathode-ray-tube
(CRT) computer display and, accordingly,
the image contrast.
contrast range In an image or pattern, the brightness
range from the lightest to the darkest parts.
contrast ratio In a video image, the ratio of maximum
to minimum luminance.
control 1. An adjustable component, such as a
rheostat, potentiometer, variable capacitor, or
variable inductor, that allows some quantity to be
varied at will. 2. A test or experiment conducted
simultaneously with another similar test conducted
under conditions lacking the factor under
consideration. Thus, if 100 resistors coated with
a special varnish are tested at 120°F, 100 identical
unvarnished resistors could be tested (as a
control) under the same conditions; in this way,
the effect of the varnish would be ascertainable.
3. As a computer function, understanding and
implementing instructions or carrying out tasks,
according to specific conditions.
control ampere-turns The ampere-turns of the
control winding in a magnetic amplifier.
control block A storage block for control information
in a computer.
control bus In a digital computer, the electrical
conductors linking the central-processing-unit
(CPU) control register to the memory circuits.
control card A card that provides control information
for a computer.
control character A character (bit group) used to
start the control of a peripheral.
control characteristic A representation (such as a
collector-current versus collector-voltage curve)
depicting the extent to which the value of one
quantity affects or controls the value of another.
cess. 2. In a digital computer, a circuit that handles
and interprets instructions and commands,
particularly in the arithmetic and logic unit
(ALU).
control computer A computer that receives signals
concerning the parameters in some process,
and responds with signals that control those parameters.
control counter See CONTROL REGISTER.
control data 1. In a computer record having a key,
information used to put the records in some sequence.
2. Information affecting a routine’s selection
or modification.
control electrode An electrode to which an input
signal can be applied to control an output signal.
Common examples are the base of a bipolar transistor,
the gate of a field-effect transistor, and the
inputs of a logic gate.
control field 1. In direct-current generators of the
amplifying type, an auxiliary field winding used
for feedback and regulation, in contrast to the
self-excited field winding (which is the conventional
field winding of the generator). 2. A computer
record field containing control data.
control flux In an amplidyne, magnetic flux generated
by current flowing through the control winding.
control grid See GRID, 1.
control-grid bias The negative dc voltage applied
between ground and the control grid of a vacuum
tube to establish the operating point.
control language Within the operating system of a
computer, the command set that the operator or
programmer uses to control the running of a program
or the operation of peripherals. Also called
job control language or system control language.
control language interpreter See CONTROL LAN-
GUAGE and INTERPRETER.
controlled avalanche diode Also called avalanche
diode or Zener diode. A diode that has a welldefined
avalanche voltage. Used primarily for
voltage regulation in power supplies.
controlled-carrier modulation See QUIESCENT
CARRIER OPERATION.
controlled-carrier transmission See QUIESCENT
CARRIER OPERATION.
controlled rectifier A rectifier whose dc output
can be varied by adjusting the voltage or phase of
a signal applied to the control element. See
SILICON-CONTROLLED RECTIFIER.
controller
1. The control signal of an electronic
control (or servo), system. 2. A device, such as a
specialized variable resistor, used to adjust current
or voltage. 3. A computer that oversees and
controls the operation of a robot or fleet of robots.
controller function The control of the movements
of a servo system.
controlling file A computer storage area encompassing
several complete magnetic disk cylinders;
its size can be changed to accommodate a
number of files.