01-08-2012, 12:07 PM
CLOSED CIRCUIT TELEVISION
cctv presentation.ppt (Size: 1.79 MB / Downloads: 45)
THE CAMERA:-
The starting point for any CCTV system must be camera. The camera creates the picture that will be transmitted to the control position.
A part from special designs CCTV cameras are not fitted with a lens. the lens must be provided separately and screwed on to from of the camera.
There is a standard screw thread for CCTV cameras , although there are different types of lens mounts.
Not all lenses have a focus and it is adjustment most have iris adjustment. Some very wide angle lenses do not have a focusing .
The ‘BNC’ plug is for connecting the coaxial video cable. Line power cameras do not have the mains cable.
Power is provided via the coaxial cable .
THE MONITOR:-
The picture created by the camera needs to be reproduced at the control position.
A CCTV monitor is virtually the same as a television receiver except that it does not have the tuning ckt.
MAIN POWERED CCTV SYSTEM:-
The basic CCTV installation is shown in figure. Where the camera is mains powered as is the monitor.
Coaxial cable carries the video signal from the camera to the monitor. Although simple to install it should be born in mind that the installation must comply with the relevant regulation such as the institute of electrical engineers latest edition.
Failure to do so could be dangerous and create problems with the validity of insurance.
The arrangement allow for a great deal more flexibility in designing complex system. When more than one camera is required than a video switcher must be included as shown in diagram (b).
Using this switcher any camera may be selected to be held on the screen or it can be set to sequence in turn through all the cameras. Usually the time that each camera is shown may be adjusted by a control knob or by a screwdriver.
MOVABLE CAMERAS:-
So far all the cameras shown have been fixed with fixed focus length lenses. In many application the area to be covered would need many fixed cameras.
The solution to this is to use camera fixed to a movable platform. This platform can then be controlled from a remote location . The platform may simply routed in horizontal plane and is generally known as scanner.
Alternatively the platform may be controllable in both horizontal and vertical planes and its generally known as a pan, a basic system is illustrated in diagram.