Closed-circuit television

Closed-circuit television (CCTV), also known as video surveillance, 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").

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. Though surveillance of the public using CCTV Camera is common in many areas around the world, video surveillance has generated significant debate about balancing its use with individuals' right to privacy even when in public.

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.

An early mechanical CCTV system was developed in June 1927 by Russian physicist Leon Theremin. Originally requested by CTO (the Soviet Council of Labor and Defense), the system consisted of a manually operated scanning-transmitting camera and wireless shortwave transmitter and receiver, with a resolution of a hundred lines. Having been commandeered by Kliment Voroshilov, Theremin's CCTV system was demonstrated to Joseph Stalin, Semyon Budyonny, and Sergo Ordzhonikidze, and subsequently installed in the courtyard of the Moscow Kremlin to monitor approaching visitors.

Another early CCTV system was installed by Siemens AG at Test Stand VII in Peenemünde, Nazi Germany, in 1942, for observing the launch of V-2 rockets.

In the United States, the first commercial closed-circuit television system became available in 1949 from Remington Rand and designed by CBS Laboratories, called "Vericon". Vericon was advertised as not requiring a government permit due to the system using cabled connections between camera and monitor rather than over-the-air transmission.

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. Due to these shortcomings, video surveillance was not widespread.

Later, videocassette recorder technology became available in the 1970s, making it easier to record and erase information, and the use of video surveillance became more common. During the 1990s, digital multiplexing was developed, allowing several cameras to record at once, as well as time-lapse and motion-only recording. This saved time and money which then led to an increase in the use of CCTV.