As the name implies, it is a system in which the circuit is closed and all the elements are directly connected. This is unlike broadcast television where any receiver that is correctly tuned can pick up the signal from the airwaves. Directly connected in this context includes systems linked by microwave, infrared beams, etc.
The starting point for any CCTV system must be the camera. The camera creates the picture that will be transmitted to the control position. Apart from special designs CCTV cameras are not fitted with a lens. The lens must be provided separately and screwed onto the front of the camera. There is a standard screw thread for CCTV cameras, although there are different types of lens mounts.
Monochrome Colour Analogue Digital Day / Night PCB ‘ Bullet’ and various other specialist units Types of Cameras Available
Colour PAL (Phase Alternate Line.) Colour TV system used in the UK SECAM ( System Electronique Couleur Avec Memorie) Colour TV system used in France NTSC (National television Standards Committee) Color TV system used in the USA
Analogue A signal in which any level is represented by a directly proportional voltage; not digital
Digital A signal that levels are represented by binary numbers. These can be kept in a store A digital camera of high class can be remotely setup from a laptop or back at the control room
Resolution Low Resolution 300TVL up to 380TVL High Resolution 380TVL to around 580TVL TVL is Television Lines Resolution