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110 character density • charge carrier
a medium. On a magnetic tape, it might be specified
in characters per millimeter; on a magnetic
disk, it might be specified in characters per
square millimeter.
character emitter A coded-pulse generator in a
digital computer.
character generator A device that converts coded
information into readable alphanumeric characters.
characteristic 1. A quantity that characterizes
(typifies) the operation of a device or circuit. Examples
are emitter current, output power, and
frequency deviation. 2. In floating point notation,
the exponent.
characteristic curve A curve showing the relationship
between an independent variable and a dependent
variable, with respect to the parameter(s)
for a device or circuit. Example: the collector voltage-collector
current characteristic curve of a
transistor.
characteristic distortion 1. In a digital signal,
pulse distortion caused by the effects of the previous
pulse or pulses. 2. Distortion in the characteristic
curve of a component or device.
characteristic frequency The frequency peculiar
to a given channel, service, or response.
characteristic impedance Symbol, Z 0 . 1. Theoretically,
the impedance that would be simulated
by a given two-conductor or coaxial line of uniform
construction, if that line were of infinite
length. This value is determined by the materials
used for the two conductors, the dielectric used
to insulate the two conductors, the diameters of
the conductors, and the spacing between them.
2. In practice, for a transmission line or waveguide
terminated with a load that produces no
standing waves on the line, the ratio of radio-frequency
(RF) voltage to RF current. This ratio is
the same at all points along the length of a perfectly
matched line, and depends on the physical
construction of the line. Coaxial lines typically
have Z 0 between 50 and 100 ohms. Twinlead is
available with 75-ohm and 300-ohm Z 0 values.
Open-wire line has Z 0 between 300 and 600
ohms, depending on the spacing between the
conductors, and also on the type of dielectric (insulating
material) employed to keep the spacing
constant between the conductors. 3. Experimentally,
the value of impedance that, if it terminates
a transmission line or waveguide, results in no
reflected power from the load end of line. This is
always a pure resistance; that is, it contains no
reactance.
characteristic overflow In floating-point arithmetic,
the condition that occurs when a characteristic
exceeds the upper limit specified by a
program or computer.
characteristic spread The range of values over
which a characteristic extends. For example, if an
amplifier’s output ranges from 15 W to 25 W, its
characteristic spread is 10 W.
characteristic underflow In floating-point arithmetic,
the condition that occurs when a characteristic
exceeds the lower limit specified by a
program or computer.
character modifier In address modification, a
constant (compare VARIABLE) that refers to a
specific character’s location in memory.
character-oriented A computer in which character
locations, rather than words, can be addressed.
character printer A computer output device that
prints matter in the manner of a conventional
typewriter.
character reader Also called an optical scanner. In
a digital computer, an input device that can read
printing and script directly.
character recognition The reading of a written or
printed character by a computer, including its
identification and encoding.
character sensing The detection of characters by
a computer input device. This can be done galvanically,
electrostatically, magnetically, or optically.
character set The set of characters in a complete
language, or in a communications system.
character signal The set of elements or bits representing
a character in a digital transmission system.
The signal can also represent the quantizing
value of a sample.
characters per minute An expression of the speed
of transmission of a digital signal. The number of
characters (on average) transmitted in a period of
one minute. In Morse code (CW) transmission,
this is generally taken as the number of times the
word paris plus the subsequent space, multiplied
by six (five letters and one space following), can
be sent in one minute.
characters per second An expression of the speed
of transmission of a digital signal. The number of
characters (on average) transmitted in a period of
one second.
character string A one-dimensional character array
[i.e., a list of characters that, when printed or
displayed, would appear in a row or column, but
not both (as in a matrix)].
character subset A classification of characters
within a set.
Charactron A cathode-ray readout tube that displays
letters, numbers, and symbols on its
screen. More commonly called a monitor.
charcoal tube In a system for producing a high
vacuum, a trap containing activated charcoal,
which is heated to dull red, then cooled by liquid
air to absorb gases.
charge
1. A quantity of electricity associated with a
space, particle, or body. 2. To electrify a space,
particle, or body (i.e., to give an electric charge).
3. To store electricity, as in a storage battery or
capacitor. Compare DISCHARGE.
charge carrier 1. An ELECTRON whose movement
constitutes a flow of electric current. 2. An elec-