Cameras linked to a monitor, digital recorder and a telephone link to an Alarm Receiving Centre (ARC). Activation of the system is generated by externally fitted movement sensors or infra red beams.

Staff at the ARC can remotely monitor the cameras and verbally speak to the site using voice informers and issue warnings. If the system by design complies with British Standard 8418 then a police response can be generated.

Lighting levels are vital for ensuring good quality images and so a site visit is essential for designing a CCTV system. Light levels can be enhanced by white light, infra red light and thermal imaging. Number plate details are often required these can be achieved using specialist number plate recognition cameras. Facial recognition of individuals can be achieved only if the subject gets close to the camera and is not masked.

Some larger CCTV systems have to be registered with the Information Commissioners Office. Notes of guidance are issued with each specification.