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[[File:Cameratoezichtcentrale politie nederland.jpg|thumb|Desk in one of the regional control-rooms of the National Police in the Netherlands in 2017]]
[[File:CCTV control room monitor wall.jpg|thumb|CCTV control-room monitor wall for 176 open-street cameras in 2017]]
An early [[Mechanical television|mechanical]] CCTV system was developed in June 1927 by Russian physicist [[Léon Theremin]]<ref name=":0">{{Cite book|title=Theremin : ether music and espionage|last=Glinsky, Albert.|date=2000|publisher=University of Illinois Press|isbn=0252025822|location=Urbana|pages=46–47|oclc=43286443}}</ref> (cf. [[Television in the Soviet Union]]). 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.<ref name=":0" />
Another early CCTV system was installed by [[Siemens|Siemens AG]] at [[Test Stand VII]] in [[Peenemünde]], Nazi Germany in 1942, for observing the launch of [[V-2 rocket]]s.<ref name="dornberger">[[Walter Dornberger|Dornberger, Walter]]: ''V-2'', [[Ballantine Books]] 1954, ASIN: B000P6L1ES, page 14.</ref>
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It has been argued that problems of selection bias and endogeneity can be addressed by stronger research designs such as [[randomized controlled trials]] and [[natural experiments]]. A 2017 review published in [[Journal of Scandinavian Studies in Criminology and Crime Prevention]] compiles seven studies that use such research designs. The studies included in the review found that CCTV reduced crime by 24-28% in public streets and urban subway stations. It also found that CCTV could decrease unruly behaviour in football stadiums and theft in supermarkets/mass merchant stores. However, there was no evidence of CCTV having desirable effects in parking facilities or suburban subway stations. Furthermore, the review indicates that CCTV is more effective in preventing property crimes than in violent crimes.<ref>{{Cite journal|title = Surveillance cameras and crime: a review of randomized and natural experiments|journal = Journal of Scandinavian Studies in Criminology and Crime Prevention|date = 2017|pages = 210–222|volume = 18|issue = 2| author = Gustav Alexandrie|doi = 10.1080/14043858.2017.1387410|s2cid = 149144413}}</ref>
[[File:Alexis Navy Yard 012 1dsLQLVk7nY.jpg|thumb|left|Closed circuit television cameras captured the perpetrator of the [[Washington Navy Yard shooting]],
Another question in the effectiveness of CCTV for policing is around uptime of the system; in 2013 City of Philadelphia Auditor found that the $15M system was operational only 32% of the time.<ref>{{cite web|url=http://www.viakoo.com/orphaned-video-system-in-philadelphia/|title=Orphaned Video System in Philadelphia?|date=May 2015|access-date=29 July 2015|archive-date=28 October 2017|archive-url=https://web.archive.org/web/20171028042359/https://www.viakoo.com/orphaned-video-system-in-philadelphia/|url-status=dead}}</ref> There is strong anecdotal evidence that CCTV aids in detection and conviction of offenders; for example, UK police forces routinely seek CCTV recordings after crimes.<ref>[https://www.telegraph.co.uk/news/uknews/crime/10512087/10484338Police-are-failing-to-recover-crucial-CCTV-footage-new-figures-suggest.html?fbHow&goback=%2Egde_1889337_member_5817222616544473092 "Police are failing to recover crucial CCTV footage, new figures suggest"], The Daily Telegraph</ref> Moreover, CCTV has played a crucial role in tracing the movements of suspects or victims and is widely regarded by anti-terrorist 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.<ref>[http://news.bbc.co.uk/1/hi/england/hereford/worcs/3101016.stm "CCTV to drive down cab attacks"], BBC</ref><ref>[http://news.bbc.co.uk/1/hi/england/bristol/4295859.stm "Taxi CCTV cameras are installed"], BBC</ref>
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In 2013 [[Oaxaca]] hired deaf police officers to [[lip reading|lip read]] conversations to uncover criminal conspiracies.<ref>[https://archive.today/2013.11.21-124759/http://m.theglobeandmail.com/news/world/oaxacas-angels-of-silence-deaf-police-officers-see-crime-where-others-dont/article15520263/?service=mobile Angels of Silence see crime where others don't] Globe & Mail, 20 November 2013</ref>
In Singapore, since 2012, thousands of CCTV cameras have helped deter loan sharks, nab litterbugs, and stop illegal parking, according to government figures.<ref>{{Cite web|url=http://www.straitstimes.com/singapore/network-of-cctv-cameras-proving-effective|title=Network of CCTV cameras proving effective | publisher= straitstimes|access-date=2017-02-06|date=8 March 2016 }}</ref>
===Crime solving===
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=== Employee monitoring ===
{{See also|Employee monitoring}}
Organizations use CCTV to monitor the actions of workers. Every action is recorded as an information block with subtitles that explain the performed operation. This helps to track the actions of workers, especially when they are making critical financial transactions, such as correcting or cancelling of a sale, withdrawing money, or altering personal information.
Actions which an employer may wish to monitor could include:
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===Use in schools===
{{further|Video surveillance in schools}}
In the United States, Britain, Canada,<ref>{{cite news|url=https://www.atl.org.uk/policy-and-campaigns/policy-posts/use-cctv-surveillance-schools?resetmyATL=true|title= Use of CCTV surveillance in schools| author= ATL|access-date=8 November 2016|publisher= ATL the education union|date=22 October 2013}}</ref> Australia<ref>{{cite news|url=http://www.dailytelegraph.com.au/news/nsw/school-security-cctv-puts-bullies-on-pause/story-e6freuzi-1226311797645|title= School security CCTV puts bullies on pause | author= Bruce McDougall and Katherine Danks |access-date=8 November 2016|newspaper= The Daily Telegraph|date=28 March 2012}}</ref> and New Zealand, CCTV is widely used in schools due to its success in preventing [[bullying]], [[vandalism]], monitoring visitors and maintaining a record of evidence of a crime. There are some restrictions, cameras not being installed in areas where there is a "reasonable [[expectation of privacy]]", such as bathrooms, gym locker areas, and private offices (unless consent by the office occupant is given). Cameras are generally acceptable in hallways, parking lots, front offices where students, employees, and parents come and go, gymnasiums, cafeterias, supply rooms, and classrooms. Some teachers object to the installation of cameras.<ref>{{cite web|url = https://www.ncjrs.gov/school/ch2a_18.html/|title = Legal aspects of the use of video cameras in schools =|access-date = 25 March 2014|archive-url = https://web.archive.org/web/20160215174520/https://www.ncjrs.gov/school/ch2a_18.html/|archive-date = 15 February 2016|url-status = dead}}</ref>
A study of high school students in Israeli schools shows that students' views on CCTV used in school are based on how they think of their teachers, school, and authorities.<ref name=":1">{{Cite journal|last1=Birnhack|first1=Michael D.|last2=Perry-Hazan|first2=Lotem|date=2020|title=School Surveillance in Context: High School Students' Perspectives on CCTV, Privacy, and Security|url=http://dx.doi.org/10.2139/ssrn.3587450|journal=SSRN Electronic Journal|doi=10.2139/ssrn.3587450|s2cid=234991261|issn=1556-5068}}</ref> It also stated that most students do not want CCTV installed inside a classroom.<ref name=":1" />
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=== Counter-terrorism ===
{{further|War on terror}}
Material collected by surveillance cameras has been used as a tool in post-event forensics to identify tactics, techniques, and perpetrators of [[terrorist attack]]s. Furthermore, there are various projects − such as [[INDECT]] − that aim to detect suspicious behaviours of individuals and crowds.<ref>{{cite journal|last1=Mould|first1=Nick|last2=Regens|first2=James L.|last3=Jensen|first3=Carl J.|last4=Edger|first4=David N.|title=Video surveillance and counterterrorism: the application of suspicious activity recognition in visual surveillance systems to counterterrorism|journal=Journal of Policing, Intelligence and Counter Terrorism|date=30 August 2014|volume=9|issue=2|pages=151–175|doi=10.1080/18335330.2014.940819|s2cid=62710484}}</ref> It has been argued that terrorists will not be deterred by cameras, that terror attacks are not really the subject of the current use of video surveillance and that terrorists might even see it as an extra channel for [[propaganda]] and publication of their acts.<ref>{{cite magazine|title=In the Petabyte Age of Surveillance, Software Polices|url=http://www.popularmechanics.com/technology/security/how-to/a5776/surveillance-cameras-and-data/|magazine=Popular Mechanics|access-date=4 January 2017|date=10 May 2010}}</ref><ref>{{cite web|title=Mehr Videoüberwachung gegen Terroristen - WDR aktuell - Sendung - Video - Mediathek - WDR|url=http://www1.wdr.de/mediathek/video/sendungen/wdr-aktuell/video-mehr-videoueberwachung-gegen-terroristen-100.html|publisher=WDR|access-date=4 January 2017|date=26 October 2016}}</ref> In Germany calls for extended video surveillance by the country's main political parties, [[Social Democratic Party of Germany|SPD]], [[Christian Democratic Union of Germany|CDU]], and [[Christian Social Union in Bavaria|CSU]] have been dismissed as "little more than a [[placebo]] for a subjective feeling of security" by a member of the Left party.<ref>{{cite web|title=Calls increase for sweeping surveillance after Berlin attack|url=http://www.dw.com/en/calls-increase-for-sweeping-surveillance-after-berlin-attack/a-36854715|publisher=Deutsche Welle|access-date=4 January 2017}}</ref>
== Prevalence ==
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=== Retention, storage and preservation ===
There is a cost in the retention of the images produced by CCTV systems. The amount and quality of data stored on storage media is subject to compression ratios, images stored per second, image size, and is affected by the retention period of the videos or images.<ref name="JVSG Video Compression Guide 2010">{{cite web|title= MotionJPEG, JPEG2000, H.264 and MPEG-4 compression methods in CCTV|access-date=2011-05-01|url=http://www.jvsg.com/cctv-compression-guide/}}</ref> DVRs store images in a variety of [[proprietary file format]]s. Recordings may be retained for a preset amount of time and then automatically archived, overwritten, or deleted, the period being determined by the organisation that generated them.
=== IP cameras ===
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Main types of IP cameras include: fixed cameras, [[Pan–tilt–zoom camera|pan-tilt-zoom]] (PTZ) cameras and multi-sensor cameras.<ref>{{cite web |url= https://internationalsecurityjournal.com/selecting-most-suitable-cameras/ |title= Selecting the most suitable cameras to monitor large areas |website= internationalsecurityjournal.com |date= 19 November 2020 |publisher= International Security Journal |access-date= 2021-06-23}}</ref> Fixed cameras' resolution can vary based on the application area, but typically does not exceed 20 MP. The main feature of a PTZ is its remote directional and optical zoom capability. With multi-sensor cameras, wider areas can be monitored and hundreds of [[megapixel]] resolution can be achieved.
Industrial video surveillance systems use [[network video recorder]]s to support IP cameras. These devices are responsible for the recording, storage, video stream processing, and alarm management.
Since 2008, IP video surveillance manufacturers can use a standardized network interface ([[ONVIF]]) to support compatibility between systems.<ref>{{cite web |url= https://www.ifsecglobal.com/onvif/ |title= ONVIF: a guide to the open security platform |website= ifsecglobal.com |publisher= IFSEC Global |access-date= 2021-06-23}}</ref>
=== Networking CCTV cameras ===
The city of [[Chicago]] operates a networked video surveillance system which combines CCTV video feeds of government agencies with those of the private sector, installed in city buses, businesses, public schools, subway stations, housing projects, etc.<ref>{{cite web|title=The City of Chicago's OEMC and IBM Launch Advanced Video Surveillance System|url=http://www-03.ibm.com/press/us/en/pressrelease/22385.wss|website=IBM News Room}}</ref> Even homeowners are able to contribute footage. It is estimated to incorporate the video feeds of a total of 15,000 cameras.<ref>{{Cite news|url=https://www.wsj.com/articles/SB10001424052748704538404574539910412824756|title=Chicago's Camera Network Is Everywhere|author=William M. Bulkeley|newspaper=Wall Street Journal}}</ref>
The system is used by Chicago's [[Office of Emergency Management]] in case of an emergency call: it detects the caller's location and instantly displays the real-time video feed of the nearest security camera to the operator, not requiring any user intervention. While the system is far too vast to allow complete real-time monitoring, it stores the video data for use as evidence in criminal cases.<ref>"[https://www.wsj.com/articles/SB10001424052748704538404574539910412824756 Chicago's Camera Network Is Everywhere]", The Wall Street Journal</ref>
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