Closed-circuit television CCTV , also known as video surveillance , [ 1 ] [ 2 ] is the use of closed-circuit television cameras to transmit a signal to a specific place on a limited set of monitors. It differs from broadcast television in that the signal is not openly transmitted, though it may employ point-to-point , point-to-multipoint P2MP , or mesh wired or wireless links.
Even though almost all video cameras fit this definition, the term is most often applied to those used for surveillance in areas that require additional security or ongoing monitoring videotelephony is seldom called "CCTV" [ 3 ] [ 4 ]. The deployment of this technology has facilitated significant growth in state surveillance, a substantial rise in the methods of advanced social monitoring and control, and a host of crime prevention measures throughout the world.
In industrial plants , CCTV equipment may be used to observe parts of a process from a central control room , especially if the environments observed are dangerous or inaccessible to humans. CCTV systems may operate continuously or only as required to monitor a particular event.
A more advanced form of CCTV, using digital video recorders DVRs , provides recording for possibly many years, with a variety of quality and performance options and extra features such as motion detection and email alerts. More recently, decentralized IP cameras , perhaps equipped with megapixel sensors, support recording directly to network-attached storage devices or internal flash for stand-alone operation. In the United States, the first commercial closed-circuit television system became available in from Remington Rand and designed by CBS Laboratories , called "Vericon".
The earliest video surveillance systems involved constant monitoring because there was no way to record and store information. The development of reel-to-reel media enabled the recording of surveillance footage. These systems required magnetic tapes to be changed manually, with the operator having to manually thread the tape from the tape reel through the recorder onto a take-up reel.
