C-mount:
is a lens mount with 17.526 mm back flange.
Back flange is the distance between the
lens mounting surface and the CCD chip.
Cable
compensated amplifier:
High frequency video signals are attenuated
when transmitted through cables. A cable
compensated amplifier boosts the high
frequency signals depending upon the cable
distance. This ensures minimum video loss.
Cable
core:
is the central part of the cable which
actually carries the video , control or
power signals. It can be made up of a
single conductor ( solid core) or a number
of electrical wires.
Cable
jacket:
is the outer protective coating which
covers the core of the cable.
Cable
tray:
is a long tray installed in many sites
which allows cables to be economically
laid out.
Camera:
is an electronic device which converts
light into an electrical signal.
Camera
controller:
controls the different functions
of the pan tilt head and the zoom lens.
It is also known as the PTZ controller.
Candela:
a new unit which replaces the
candle and is a measurement of luminous
intensity
Cathode
ray tube (CRT):
is a tube in the monitor containing
a heated cathode which emits a beam of
electrons focused on a phosphor coated
surface. The surface glows depending upon
the intensity of the beam. The deflection
circuitry in the tube controls the movement
of the beam.
CCD
Charge Coupled Device:
is a solid state device in a
camera that converts light falling on
it into an electrical signal.
CCD
iris:
is a feature in modern CCD cameras
by which the iris function is performed
by the CCD chip itself. This eliminates
the need for an auto iris lens. The CCD
iris can handle minor light fluctuations
only and therefore is not recommended
for most outdoor applications.
CCIR
International Radio Consultative Committee:
recommends a format of 625 lines
per frame and a transmission speed of
25 frames per second.
Celsius:
is the metric unit for measuring
temperature. In this scale, the boiling
point of water is 100 deg. In the USA,
the unit used to measure temperature is
Fahrenheit.
Channel
separation:
When signals are multiplexed
at different frequencies for transmission,
then the separation between these frequencies
is called channel separation. Poor separation
can lead to cross talk.
Chromatic
aberration:
is an error in lenses which causes
the focal point to be scattered. This
occurs because different wavelengths of
light bend differently through a lens.
A combination of lenses are required to
minimise this error.
Chrominance
signal:
is that part of the video signal
which contains the colour information.
In S-VHS, this signal is transmitted along
a separate cable. In a composite video
signal, the chrominance signal is multiplexed
at a higher frequency and sent along the
same cable.
Colour
stripe filter:
is a type of filter placed in
front of a colour CCD chip. It breaks
up light into the basic colours - red,
green and blue which are then directed
to separate pixels in the CCD chip
Common
sync generator:
is a device used to synchronise
cameras. It generates synchronising pulses
that are sent to all cameras connected
to it by coaxial cable.
Composite
video:
is a standard signal format in
CCTV which contains the video signal,
the horizontal and vertical sync pulses
and the blanking pulses. The sync pulses
are 0.3 volts and the video signal is
0.7 volts.
Concave:
is a type of optical lens in
which the light rays passing through it
are made to diverge by the inward bulge
of the glass surface.
Conduit:
is a plastic or metallic tube
which is used to conceal, protect or secure
cables.
Connector:
a device used to interconnect
cables or connect cables to various equipment.
Contrast:
is the difference in the intensity
between the black parts and white parts
of the picture on the monitor.
Contrast
Control:
is a control in the monitor which
changes the contrast by increasing or
decreasing the amplitude of the video
signal.
Covert:
is a mode of CCTV surveillance
in which the camera and lens are hidden
and cannot be seen.
Convex:
is a type of optical lens in
which the light rays passing through it
are made to converge by the outward bulge
of the glass surface.
Crimping:
is a process of connecting a
cable to a connector without screwing
or soldering using a special tool. In
crimping a BNC connector, the centre pin
of the connector is uniformly pressed
against the cable core. To ensure a proper
connection, a good crimping tool is needed.
Cross
talk:
is the noise generated by the
interference between adjacent ( in terms
of signal frequency) video, audio or data
channels in a multiplexed signal.
CS
mount:
is a lens mount with 12.5 mm
back flange. Back flange is the distance
between the lens mounting surface and
the CCD chip. |
