The
CCTV
Glossary
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G
Gain.
Any increase or decrease in strength of an electrical signal.
Gain
is often measured
in terms of
decibels, the logarithmic ratio of input to output.
Gamma. A correction
of the linear response of a camera in order to compensate for the
monitor phosphor screen non-linear
response. It is measured with the exponential
value
of the curve describing the non-linearity.
A typical monochrome monitor's gamma
is 2.2,
and a camera needs to be set to
the inverse value of 2.2 (which
is 0.45) for the overall
system to respond linearly (i.e.,
unity).
Gamut. The range of
voltages allowed for a video signal, or a component of a video signal.
Signal voltages outside of the
range (i.e., exceeding the gamut) may lead to
clipping,
crosstalk or other distortions.
Gen-lock. A way of
locking the video signal of a camera to an external generator of
synchronization pulses.
GHz. Giga Hertz.
One thousand million (American billion) cycles per second.
GB. Gigabyte.
Unit of computer memory consisting of about one thousand million bytes
(a
thousand megabytes). The
actual value is 1,073,741,824 bytes.
GND. Ground (electrical).
Grey scale. A series
of shades of grey that range from true black to true white, usually
expressed in 8 or 10
steps.
Ground loop. (Also known
as an Earth Loop) An unwanted interference in the copper electrical
signal transmissions with shielded
cable, which is a result of ground currents when the system has
more than one ground
point. For example, in CCTV, when we have a different earthing
resistance
at the camera
end to that at the switcher or monitor end. It must NEVER be
cured
by removing
either ground connection, it should
be removed using an isolation transformer or other isolating device ,
eg
opto-isolator.
GUI. Graphical User
Interface. A computer type display giving system status
information
it
may also include touchscreen control.
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