Introduction to CCTV

There are still people who talk about CCTV without realising what the initials stand for – Closed Circuit Television. So what exactly is this system of surveillance and security which has mushroomed in the UK to the extent that it now has more cameras per head of population than any other country?

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Quite simply it is exactly as the name implies – a system in which the circuit is closed and all the elements are directly connected, including those linked by microwave, infra-red beams and so on. This is what makes it different from broadcast television, which enables any correctly tuned receiver to pick up the signal from the airwaves.

While the most common use of CCTV is providing security in retail shops, government establishments, hospitals, banks and suchlike, and surveillance with regard to traffic, crowds, airports etc, the list of possibilities is endless. It has, for example, even been used for recording the birth of a gorilla at a zoo and reproducing the infra-red vision of a goldfish!

You may not be aware of it, but every bank cash machine in the country uses CCTV to record you making your cash transaction. Indeed, it might interest you to know that there are more than four million CCTV cameras in the UK and you are likely to be caught on camera 300 times a day. A startling statistic is that Britain has 20 per cent of the world’s CCTV cameras to photograph one per cent of the world’s population!

The British government has been heavily involved in the growth of the world’s largest CCTV network, providing a total budget of £420m.

So how does it work?

The simplest system is the line-powered camera, which has a camera connected directly to a monitor by a coaxial cable, and from that evolved the outputs from four cameras into the monitor, with a built-in microphone. Now there are many line-powered systems on the market that are far more sophisticated, with most of the earlier disadvantages having been overcome.

Then there is the system in which both camera and monitor are mains-powered, with a coaxial cable carrying the video signal from the camera to the monitor, which allows for much more flexibility in designing complex systems. You could also add a video recorder.

Fixed cameras have their obvious limitations, especially if there is a large area to cover, so the advent of cameras fixed to a movable platform, controlled from a remote location, was warmly welcomed.

CCTV cameras can be used both indoors and outdoors, although in the case of the latter they will require a protective housing. In some instances it may be practical to have a system which has a combination of both fixed and movable cameras.

The CCTV system continues to evolve and these days it is possible to have a multiple recording of many cameras; touch-screen control; immediate full colour prints from a camera or recording; and the switching of thousands of cameras from many separate control positions to dozens of monitors, among many other sophisticated applications.