CCTV

CCTV stands for closed circuit television. It is a system where the circuit is closed and all the elements are linked. This is different from broadcast T.V. where tuners pick up the signals from the airwaves. For purposes of this article, linked means connected by wiring, microwave, infrared, etc.

 

What's It Used For?

The most obvious and common use for CCTV is for security. This type of installation is used in a variety of locations such as stores, banks, schools and government buildings. However, there are so many other uses. It can be used for monitoring traffic. It is used in sports stadiums to focus on the audience. It can be hidden in trains and buses to detect vandalism. It can be used to monitor animals in a zoo. It can even be used to reproduce infrared vision. The applications are almost limitless.

 

What's In It?

It all starts with the camera. This creates the picture that is transmitted to the control area. Most CCTV cameras are not fitted with lenses. They must be obtained separately and screwed on. There is a standard screw thread although there are different mounts. Not all lenses have focus adjustment. Most have iris adjustment. Some wide angle lenses do not have a focus ring. There is a BNC jack for connecting the video cable. In the case of line powered cameras, this coaxial cable also provides power. The monitor is what receives the signal that the camera creates. A CCTV monitor is similar to a television set but it does not have tuning circuits.

 

Simple CCTV systems consist of a camera connected to a monitor with coaxial cable or a category 5e or higher cable. This cable also carries the power needed for the camera. This is called a line powered camera. The Pye Observation System was such a system and was popular during the early days of CCTV. It was affordable and could be set up with a minimum of difficulty. The next big step in the technology was allowing for four cameras to be connected to the monitor simultaneously. The view could be programmed to cycle through the available cameras or go to a particular camera chosen by the user.