How CCTV is used

2. How it works

The images are transmitted from the camera down optical fibre as a light signal. On arrival at the CCTV control centre the signal is converted back into pictures. The date, time and camera number is imprinted onto each frame of the image.

Images from each camera are sent to one of the monitors. Or they're projected display units on the video wall and to each of the spot monitors on the desk.

The images are also sent to 'lapsed time' digital video recorders and recorded on to hard drives. This is where all footage is recorded 24 hours a day, 7 days a week, every day of the year.

In addition to lapsed time recording, the CCTV system uses 'real time' recording equipment. These recordings will show events as they happen.

When an operator observes an incident, they're able to monitor and record the event in real time. This is whilst they're initiating a response from the police.

Once the incident is over, the investigating police officer can arrange to view the images for evidential quality. The police can request a copy of the recorded images to enable them to conduct their investigation.

Images are recorded onto hard drives and are kept for 31 days before the hard drives are electronically erased.