Page 68 - Electrical Engineering Dictionary

(2) a spring-loaded tension sleeve into interconnected system, scheduled power in-
which a conductor or other wire is inserted terchanges are maintained by means of con-
for tensioning and attachment to a pole or trolling area generations.
other fixture.
(2) electronic circuitry used to keep the re-
ceived signal properly placed within the de-
automatic allocation allocation of mem-
sired IF frequency range. In televisions, the
ory space to hold one or more objects whose
AFC circuitry is also called the AFT or “auto-
lifetimes match the lifetime of the activation
matic fine tuning” section. The AFC circuit
of a module, such as a subroutine. Automatic
will generate an error signal if the input fre-
allocations are usually made upon entry to a
quency to the IF drifts above or below the
subroutine.
IF frequency. The error signal is fed back
to vary the local oscillator frequency in the
automatic black-level control electronic
tuner section. See also automatic fine tuning
circuitry used to maintain the black levels of
(AFT).
thevideosignalatapredeterminedlevel. The
black level reference is either derived from
the image or from the back porch of the hor- automatic gain control (AGC) a method
izontal blanking interval. to control the power of the received signal
in order to be able to use the full dynamic
automatic chroma control (ACC) ACC range of the receiver and to prevent receiver
is used to correct the level of the input chroma saturation.
signal. Typically, the ACC circuitry makes
corrections to the chroma, based on the rela-
automatic generation control (AGC)
tive degeneration of the color burst reference
phrase describing the computer-based pro-
signal, since this signal will have been sub-
cess by which electric utilities control indi-
jected to the same degradation.
vidual generating stations to maintain system
frequency and net interchange of power on a
automatic circuit recloser See recloser.
highly interconnected transmission grid. Au-
tomatic generation control (AGC) systems
automatic fine tuning (AFT) one of
monitor grid frequency, actual and scheduled
the input circuits of a color television re-
power flows, and individual plant output to
ceiver specifically designed to maintain the
maintain balance between actual and sched-
correct oscillator frequency of the tuner
uled power production, both within transmis-
for best color reproduction of the picture.
sion control areas and at individual gener-
The circuit is sometimes called the auto-
ating stations. Control is generally accom-
matic frequency control. See also automatic
plished by adjusting the speed control (or
frequency control (AFC).
droop) characteristics of individual generat-
ing units. Control actions are determined by
automatic focusing on an optical disk,
planned production schedules and power ex-
the process in which the distance from the ob-
change agreements among participating util-
jective focal plane of the disk is continuously
ities.
monitored and fed back to the disk control
system in order to keep the disk constantly in
focus. automatic level control (ALC ) a feed-
back system where an RF signal from a
automatic frequency control (AFC) (1) source is sampled, detected, and sent to a
an automatic feedback control system that voltage controlled attenuator to maintain a
is used to maintain active power balance by constant amplitude output over a specified
means of the speed governor system. In an band of frequencies.
c
2000 by CRC Press LLC