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.
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.
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 (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.
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, which was a time-consuming, expensive and unreliable process, with the operator having to manually thread the tape from the tape reel through the recorder onto an empty take-up reel. Due to these shortcomings, video surveillance was not widespread. VCR technology became available in the 1970s, making it easier to record and erase information, and 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 increased savings of time and money and the led to an increase in the use of CCTV.
Recently CCTV technology has been enhanced with a shift towards internet-based products and systems and other technological developments.
A 2009 analysis by Northeastern University and the University of Cambridge, “Public Area CCTV and Crime Prevention: An Updated Systematic Review and Meta-Analysis,” examined 44 different studies that collectively surveyed areas from the United Kingdom to U.S. cities such as Cincinnati and New York.
The results from the above 2009 “Public Area CCTV and Crime Prevention: An Updated Systematic Review and Meta-Analysis”, are somewhat controversial. Earlier similar meta-analysis completed by Walsh and Farrington in 2002 showed similar results: a significant decrease in car park crime (41%), and a non-significant decrease of crime in public transit and public places. This study was criticised for the inclusion of confounding variables (e.g. notification of CCTV cameras on site, improved street lighting) found in the studies analyzed (including car park studies). These factors could not be differentiated from the effect of CCTV cameras being present or absent while crimes were being committed. Thus, a combination of factors might be important for the decrease in crime not just the CCTV cameras. The 2009 study admitted to similar problems as well as issues with the consistency of the percentage of area covered by CCTV cameras within the tested sites (e.g. car parks have more cameras per square inch than public transit). There is still much research to be done to determine the effectiveness of CCTV cameras on crime prevention before any conclusions can be drawn.
There is strong anecdotal evidence that CCTV aids in detection and conviction of offenders; indeed major police forces routinely seek CCTV recordings after crimes. Moreover, CCTV has played a crucial role in tracing the movements of suspects or victims and is widely regarded by antiterrorist officers as a fundamental tool in tracking terrorist suspects. Large-scale CCTV installations have played a key part of the defenses against terrorism since the 1970s. Cameras have also been installed on public transport in the hope of deterring crime, and in mobile police surveillance vehicles, often with automatic number plate recognition, and a network of APNI-linked cameras is used to manage London’s congestion charging zone. Even so there is political hostility to surveillance and several commentators downplay the evidence of CCTV’s effectiveness, especially in the US. However, most of these assertions are based on poor methodology or imperfect comparisons.
In October 2009, an “Internet Eyes” website was announced which would pay members of the public to view CCTV camera images from their homes and report any crimes they witnessed. The site aimed to add “more eyes” to cameras which might be insufficiently monitored. Civil liberties campaigners criticized the idea as “a distasteful and a worrying development”. Unfortunately, since that time, the website has been taken down. Another example, in 2013 Oaxaca hired deaf police officers to lip read conversations to uncover criminal conspiracies.