Closed Circuit Television – An Introduction

As the name suggests, Closed Circuit Television (CCTV) is a system where in the circuit is closed and all the elements are directly connected. This is different from broadcast television where any receiver that is properly tuned can pick up the signal from the airwaves. Directly related in this context includes systems linked by microwave, infrared beams, etc. Read on and be familiar with the main components that can go to make up CCTV systems of varying complexity.

Different Applications for CCTV Systems

Probably the most widely known use of CCTV is in the world of security. Security systems and such applications in retail shops, banks, government establishments and the likes. The true scope for applications is almost never-ending. Some examples are:

o Monitoring traffic on a bridge.
o Recording what is inside of a baking oven to know the cause of problems.
o A temporary system to carry out a traffic survey in a town center.
o Time lapse recording for the animation of plastic puppets.
o Used by a stage manager of a show to see unnoticed parts of a set.
o The well-publicized use at football stadiums.
o Hidden in buses to manage vandalism.
o Recording the birth of a lion at a zoo.
o Making a wildlife program using a large model helicopter.
o Reproducing the infrared vision of a bubble fish!
o Aerial photography from a hot air balloon.
o Production control in a factory.

The Camera

The jump-off point for any CCTV system should be the camera. The camera creates the picture that will be transmitted to the control position. Aside from special designs, CCTV cameras are not fitted with a lens. The lens must be provided separately and screwed into the front of the camera. There is a standard screw thread for these specific cameras, but there are different types of lens mounts.

Not all lenses have focus and iris adjustments. Most have iris adjustments while some have very wide angle lenses without a focus ring. The BNC plug is used for connecting the coaxial video cable. Line powered cameras do not have the mains cable. Power is provided via the coaxial cable.

The Monitor

The image created by the camera needs to be reproduced at the control position. A CCTV monitor is essentially the same as a television receiver except that it does not have the tuning circuits.

First CCTV Systems

The simplest CCTV system is a camera connected directly to a monitor by a coaxial cable with the power for the camera provided from the monitor. This is called the line powered camera. Probably the earliest popular version of this was the Pye Observation System that initiated the concept of CCTV, mainly in retail establishments. It was an cost-friendly, do-it-yourself, self-contained system.