Closed-Circuit Television

Closed circuit television, or CCTV, also called video surveillance, uses cameras to send a video signal to a limited set of monitors rather than broadcasting it openly, over a wired or wireless connection, and it is used mainly where an area needs security or ongoing monitoring. Russian physicist Leon Theremin built an early mechanical closed circuit system in June 1927 on commission from the Soviet Council of Labor and Defense, a manually operated scanning and transmitting camera achieving about 100 lines of resolution that was installed at the Moscow Kremlin to watch visitors. Siemens installed another early system in 1942 at a Nazi German rocket facility to observe V-2 rocket launches, and the first commercial closed circuit television system in the United States went on sale in 1949 from Remington Rand under the name Vericon. Today CCTV is used for crime prevention, traffic monitoring, workplace supervision, and building security, and it has moved from reel to reel recording to digital video recorders and internet protocol cameras that support remote viewing and motion detection. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/