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Closed-circuit television
Closed-circuit television (CCTV), also known as video surveillance, is the use of video 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 (P2P), point to multipoint, or mesh wireless links. Though almost all video cameras fit this definition, the term is most often applied to those used for surveillance in areas that may need monitoring such as banks, casinos, airports, military installations, and convenience stores. Videotelephony is seldom called "CCTV" but the use of video in distance education, where it is an important tool, is often so called.〔Verman, Romesh. (Distance Education In Technological Age ), Anmol Publications Pvt. Ltd., 2005, pp.166, ISBN 81-261-2210-2, ISBN 978-81-261-2210-3.〕〔"Distance education in Asia and the Pacific: Proceedings Of The Regional Seminar On Distance Education, 26 November - 3 December 1986", Asian Development Bank, Bangkok, Thailand, Volume 2, 1987〕
In industrial plants, CCTV equipment may be used to observe parts of a process from a central control room, for example when the environment is not suitable for humans. CCTV systems may operate continuously or only as required to monitor a particular event. A more advanced form of CCTV, utilizing digital video recorders〔(【引用サイトリンク】url=http://www.sourcesecurity.com/products-search-results/digital-recorders.html )〕 (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, some equipped with megapixel sensors, support recording directly to network-attached storage devices, or internal flash for completely stand-alone operation. Surveillance of the public using CCTV is particularly common in many areas around the world. In recent years, the use of body worn video cameras has been introduced as a new form of surveillance.
== History ==
The first CCTV system was installed by Siemens AG at Test Stand VII in Peenemünde, Germany in 1942, for observing the launch of V-2 rockets.〔Dornberger, Walter: ''V-2'', Ballantine Books 1954, ASIN: B000P6L1ES, page 14.〕 The noted German engineer Walter Bruch, Wayne Cox, and Tashara Arnold were responsible for the technological design and installation of the system.
In the U.S. the first commercial closed-circuit television system became available in 1949, called Vericon. Very little is known about Vericon except it was advertised as not requiring a government permit.〔('' "Television Rides Wires" '', February 1949, Popular Science ) small article, bottom of page 179〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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