18WuD2x

change tape • character density 109
change tape See TRANSACTION TAPE.
channel 1. A frequency (or band of frequencies) assigned
to a radio or television station. 2. See KEY-
WAY. 3. A subcircuit in a large system [e.g., the
radio-frequency (RF) channel of a receiver, the
vertical-amplifier channel of an oscilloscope, or the
modulator channel of a radio transmitter]. 4. The
end-to-end electrical path through the semiconductor
body in a field-effect transistor. 5. One of
the independent audio circuits in a stereo sound
system (e.g., the left channel or the right channel).
channel analyzer A (usually multiband) continuously
tunable instrument, similar to a tuned radio
receiver, used in troubleshooting radio
communications circuits by substituting a perfect
channel for one that is out of order.
channel balance The state in which the apparent
amplitude of two or more channels is identical.
channel bank In a transmission system, the terminal
equipment used for the purpose of multiplexing
the individual channels.
channel capacity The fullest extent to which a
channel can accommodate the information (frequencies,
bits, words, etc.) to be passed through it.
channel designator A name, number, or abbreviation
given to a channel in a communications system.
channel effect The possible current flow through a
high impedance between the collector and emitter
in a bipolar transistor.
channel frequency The CENTER FREQUENCY of
a communications channel.
channeling Multiplex transmission in which separate
carriers within a sufficiently wide frequency
band are used for simultaneous transmission.
channelizing The subdivision of a relatively wide
frequency band into a number of separate subbands.
channel reliability 1. The proportion of time, usually
expressed as a percentage, that a communications
channel is useful for its intended purpose.
2. The relative ease with which communications
can be carried out over a particular channel.
channel reversal In stereo reproduction, interchanging
the left and right channels.
channel-reversing switch In a stereo system, a
switch that allows channel reversal without the
need for reorienting speaker cables or connectors.
channel sampling rate The rate at which individual
channels are sampled. For example, in the
electronic switching of an oscilloscope, the number
of times per second each input-signal channel
is switched to the instrument.
channel selector A switch or relay used to put any
of a series of channels into functional status in a
system.
channel separation 1. The spacing between communications
channels, expressed in kilohertz. 2.
In stereo reproduction, the degree to which the
information on one channel is separate from the
other; usually expressed in decibels.
Max
Amplitude
Min
Lower
Channel
separation
f 1 f 2 f 3
Frequency
Higher
channel separation, 1.
channel slot On a carrier modulated by numerous
signals, the position or frequency of a specific
modulating signal.
channel shift The interchange of communications
channels (e.g., the shift from a calling frequency
to a working frequency).
channel strip A fixed-channel amplifier for a television
receiver.
channel time slot In a frame of transmitted information,
such as a television picture, a time interval
designated to a channel for the transmission
of a character signal or other information.
channel-to-channel connection A device, such as
a channel adapter, used to transfer data rapidly
between any two channels of two digital computers,
at the data speed of the slower channel.
channel-utilization index An indication of the extent
to which channel capacity is used. For a
given channel, the index is the ratio of information
rate to channel capacity, each expressed in
units per second.
channel wave An acoustic wave that travels
within a region or layer of a substance because of
a physical difference between that layer and the
surrounding material. An example of a channel
wave is the propagation of sound over a still lake.
channel width In a frequency channel, the difference
f 2 – f 1 , where f 1 is the lower-frequency limit
and f 2 is the upper-frequency limit of the channel.
chapter A self-contained computer program section.
character 1. One of the symbols in a code. 2. In
computer operations, a digit, letter, or symbol
used alone or in some combination to express information,
data, or instructions.
character code In a communications or computer
system, the combination of elements (e.g., bits)
representing characters.
character crowding A reduction of the time interval
between successive characters—especially
those read from tape.
character density The number of characters that
can be stored in a given length or surface area of