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6
The Sony Guide to CCTV
.
Issue 3
What is Closed Circuit
Television?
Closed Circuit Television (CCTV) is a television system which operates on a
‘closed loop’ basis. Unlike broadcast television, which is available to anyone
with a suitable receiver, CCTV pictures are only available to those directly
connected to the loop.
CCTV was first used in the 1950s and has since become an essential element in
any professional security system.
In most installations, the loop is a physical link – a cable which carries the
picture from the camera to the viewer.With very few exceptions, the pictures are
transmitted as a composite video signal at 75ohms, 1 volt peak-to-peak.Where
very high resolution (>400TV lines) is required, some equipment offers a Y/C facility
where the luminance signal (Y) and the chrominance (C) is divided. Over long
distances, for example in Town Centre systems, fibre optic transmission has
become popular.Where this option is too expensive, ISDN offers a cost-effective
alternative for event-driven surveillance systems.
As well as the full range of property protection and control applications, CCTV
offers benefits in many other areas, for example:
■ Assisting police authorities in the monitoring of traffic flow and the
implementation of prompt action in case of accidents and other emergencies
■ Supporting process industry managers as they control the flow of work, identify
production bottlenecks and take corrective action
■ Monitoring of hostile environments that are not accessible to man, i.e. nuclear
reactors, furnaces, etc.
Video Out
(Coaxial cable)
DC12 V
DC12 V
power supply
AC outlet
Colour Video Monitor