18WuD2x

carrier mobility Symbol, µ. In a semiconductor
material, the average drift velocity of electrons
and holes per unit electrostatic field.
carrier noise Modulation of a carrier when there is
no input from the modulator itself; unwanted
modulation.
carrier noise level The noise signal amplitude that
results from unintentional fluctuations of an unmodulated
carrier.
carrier-on-light transmission A form of transmission
in which many different signals are sent simultaneously
by modulating a beam of light at
multiple frequencies.
carrier-on-microwave transmission A form of
transmission in which many different signals are
sent simultaneously by modulating a microwave
signal at multiple lower frequencies.
carrier-on-wire transmission A form of transmission
in which many different signals are sent at
the same time over a wire, by using radiofrequency
carriers. Also called CARRIER-CURRENT
COMMUNICATIONS or WIRED RADIO.
carrier oscillator In a single-sideband receiver,
the radio-frequency (RF) oscillator that supplies
the missing CARRIER WAVE.
carrier power The actual power represented by a
radio-frequency (RF) carrier applied to an antenna,
measured by either the direct or indirect
method. The direct method involves determination
of power according to the formula P = I 2 R,
where I is antenna current and R is antenna resistance
at the point of current measurement.
The indirect method involves determination of
power according to the formula P = EIF, where E
and I are antenna voltage and current, and F is a
factor less than 1.0, whose value depends on the
type of modulation used.
carrier power-output rating The power delivered
by an unmodulated transmitter or generator to
the normal load or its equivalent.
carrier shift In an amplitude-modulated transmitter
or generator, the undesired change of average
carrier voltage during modulation.
carrier-shift indicator An instrument for detecting
carrier shift. It usually contains only a
pickup coil, semiconductor diode, and dc milliammeter
in series. Meter deflection is steady
until carrier shift is detected; then, the needle
fluctuates.
carrier signaling In wire telephony, the use of
carrier-wave signals to operate such functions as
dialing, ringing, busy signal, etc.
carrier storage In a semiconductor device, the tendency
of mobile carriers to stay near a junction
for a short time after the junction voltage has
been removed or reversed in polarity.
carrier suppression The elimination of the carrier
in an amplitude-modulated signal so that only
the sideband energy remains.
carrier swing In frequency-modulated or phasemodulated
transmission, the total deviation (lowcarrier
mobility • carry system 101
est to highest instantaneous frequency) of the
carrier wave.
carrier system The transmission of many signals
over one circuit, accomplished by modulating
various different carriers at different frequencies.
Different signals can use different modulation
methods.
carrier telegraphy 1. Continuous-wave telegraphy
by WIRED WIRELESS. 2. Wired-wireless telegraphy
in which a radio-frequency carrier is modulated
by an audio-frequency keying wave.
carrier telephony Telephone communication by
WIRED WIRELESS.
carrier terminal 1. At each end of a carrier-current
line or cable, the equipment for generating, modifying,
or utilizing the carrier energy. 2. In a balanced
modulator, the point of carrier insertion.
carrier-to-noise ratio The ratio of carrier amplitude
to noise-voltage amplitude.
carrier transmission Transport of information by
a carrier, as by an amplitude-modulated radio
wave that carries the low-frequency information
as the AF modulation envelope and delivers it to
the demodulator at the receiving station.
carrier-type dc amplifier A high-frequency ac amplifier,
ahead of which is operated a generator
and transducer. A dc voltage applied to the transducer
modulates the carrier supplied by the generator;
the amplifier boosts the modulated wave,
and the resultant output is rectified at a level
higher than that of the dc input signal.
carrier voltage The voltage component of a carrier
wave; also, the amplitude of this component. Compare
CARRIER CURRENT and CARRIER POWER.
carrier wave A sine wave that is modulated to
convey information in wireless and cable communications
systems. The lowest frequency normally
used for wireless signal transmission is 9
kHz, corresponding to a wavelength of approximately
33 km. The highest frequency is less well
defined; some systems make use of visible light
waves, whose wavelengths are as short as approximately
4 × 10 –7 m. For modulation to work
effectively, the carrier must have a frequency at
least 10 times the highest frequency of the modulating
signal.
carry 1. In adding a column of figures, the digit
added to the column at the left when the sum exceeds
one less than the radix value. 2. In digital
computers and counters, a pulse that corresponds
to the arithmetic operation in which a figure
is carried to the next column in addition.
carrying capacity The ability of a conductor, such
as copper wire, to carry current safely (expressed
in maximum amperes).
carry-complete signal In an arithmetic computation
by a computer, an adder-produced signal indicating
that the pertinent carries have been
generated.
carry system A communications system in which
several carries occupy one circuit.