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Closed-circuit television

File:Three Surveillance cameras.jpg|thumb|Surveillance cameras
Closed-circuit television ('''CCTV''') 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 wireless links. CCTV is often 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; when, for example, 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). Mass_surveillance#United_Kingdom|Surveillance of the public using CCTV is particularly common in the UK, where there are reportedly more cameras per person than in any other country in the world.Lewis, Paul. "Every step you take: UK underground centre that is spy capital of the world", ''The Guardian'', March 2, 2009. There and elsewhere, its increasing use has triggered a debate about security versus privacy.

History

The first CCTV system was installed by Siemens|Siemens AG at Test Stand VII in Peenemünde, Germany in 1942, for observing the launch of V-2 rockets.Walter Dornberger|Dornberger, Walter: ''V-2'', Ballantine Books 1954, ASIN: B000P6L1ES, page 14. The noted German engineer Walter Bruch was responsible for the design and installation of the system. CCTV recording systems are still often used at modern launch sites to record the flight of the rockets, in order to find the possible causes of malfunctions, while larger rockets are often fitted with CCTV allowing pictures of stage separation to be transmitted back to earth by radio link. In September 1968, Olean, New York was the first city in the United States to install video cameras along its main business street in an effort to fight crime. The use of closed-circuit TV cameras piping images into the Olean Police Department propelled Olean to the forefront of crime-fighting technology. The use of CCTV later on became very common in banks and stores to discourage theft, by recording evidence of criminal activity. Their use further popularised the concept. The first place to use CCTV in the United Kingdom was King's Lynn, Norfolk. In recent decades, especially with general crime fears growing in the 1990s and 2000s, public space use of surveillance cameras has taken off, especially in some countries such as the United Kingdom.

Uses

Crime prevention and prevalence in the UK

Outside government special facilities, Janet CCTV was developed initially as a means of increasing security in banks. Experiments in the UK during the 1970s and 1980s (including outdoor CCTV in Bournemouth in 1985), led to several larger trial programs later that decade. These were deemed successful in the government report "CCTV: Looking Out For You", issued by the Home Office in 1994, and paved the way for a massive increase in the number of CCTV systems installed. Today, systems cover most town and city centres, and many stations, car-parks and estates. The exact number of CCTV cameras in the UK is not known but a 2002 working paper by Michael McCahill and Clive Norris of UrbanEye, based on a small sample in Putney High Street, estimated the number of surveillance cameras in private premises in London is around 500,000 and the total number of cameras in the UK is around 4,200,000. Research conducted by the Scottish Centre for Crime and Justice Research and based on a survey of all Scottish local authorities, identified that there are over 2,200 public space CCTV cameras in Scotland. Bannister, J., Mackenzie, S. and Norris, P. Public Space CCTV in Scotland(2009), Scottish Centre for Crime and Justice Research (Research Report) According to their estimate the UK has one camera for every 14 people, although it has been acknowledged that the methodology behind this figure is somewhat dubious. The CCTV User Group estimate that there are around 1.5 million CCTV cameras in city centres, stations, airports, major retail areas and so forth. This figure does not include the smaller surveillance systems such as those that may be found in local corner shops. There is little evidence that CCTV deters crime; in fact, there is considerable evidence that it does not. According to a Liberal Democrats|Liberal Democrat analysis, in London "Police are no more likely to catch offenders in areas with hundreds of cameras than in those with hardly any." "Tens of thousands of CCTV cameras, yet 80% of crime unsolved" by Justin Davenport 2007 A 2008 Report by UK Police Chiefs concluded that only 3% of crimes were solved by CCTV. "Are CCTV cameras a waste of money in the fight against crime?" The Independent, 7 May 2008 In London, a Metropolitan Police report showed that in 2008 only one crime was solved per 1000 cameras. There are valid reasons for using CCTV in a comprehensive physical security program, but deterrence is not one of them. Cameras have also been installed in taxicab|taxis in the hope of deterring violence against drivers,"CCTV to drive down cab attacks," ''BBC''Taxi CCTV cameras are installed," ''BBC'' and in mobile police surveillance vans.CCTV patrols to monitor estates," ''BBC'' In some cases CCTV cameras have become a target of attacks themselves."http://news.bbc.co.uk/," ''BBC'' Middlesbrough council have recently installed "Talking CCTV" cameras in their busy town-centre."CCTV mast destroyed by vandals," ''BBC'' It is a system pioneered in Wiltshire, which allows CCTV operators to communicate directly with the offenders they spot."Talking CCTV pioneered in Wiltshire," ''BBC'', 23 March 2003 On 22 July 2005, Jean Charles de Menezes was shot dead by police at Stockwell tube station. CCTV footage debunked claims made by the Metropolitan Police in defence of the shooting of an innocent man."Menezes family view CCTV footage," ''BBC'' Because of the 21 July 2005 London bombings|bombing attempts the previous day, some of the tapes had been supposedly removed from CCTV cameras for study, and they were not functional."Menezes death 'cover-up' doubted," ''BBC'' An ongoing change to personal video recorder|DVR based technology may in future stop similar problems occurring."Digital CCTV scheme switches on," ''BBC'' The UK cameras were deployed and are maintained by NEP - Roll to Record, a division of NEP Broadcasting. In the UK, CCTV is also used to target anti-social behaviour. In many areas, local authority CCTV operators work with the police to combat, for example, drink-related anti-social behaviour in city centres or youth-related anti-social behaviour in housing estates. 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, but civil liberties campaigners criticised the idea as "a distasteful and a worrying development".Public to Monitor CCTV from home, ''BBC''

Hacking and video art

Hackers and guerilla artists have exposed the vulnerabilities of the video systems in an act dubbed "video sniffing"Christopher Werth To Watch the Watchers October 20, 2008 NewsweekNewsweek They have crossed feeds, uploaded their own video feeds and used the video footage for artistic purposes.

Industrial processes

Industrial processes that take place under conditions dangerous for humans are today often supervised by CCTV. These are mainly processes in the chemical industry, the interior of reactors or facilities for manufacture of nuclear fuel. Use of thermographic cameras allow operators to measure the temperature of the processes. The usage of CCTV in such processes is sometimes required by law.

Traffic monitoring

Many cities and motorway networks have extensive traffic-monitoring systems, using closed-circuit television to detect congestion and notice accidents. Many of these cameras however, are owned by private companies and transmit data to drivers' GPS systems. The UK Highways Agency has a publicly owned CCTV network of over 1200 cameras covering the English motorway and trunk road network. These cameras are primarily used to monitor traffic conditions and are not used as speed cameras. With the addition of fixed camera for the Active Traffic Management system the number of cameras on the Highways Agency CCTV network is likely to increase significantly over the next few years. The London congestion charge is enforced by cameras positioned at the boundaries of and inside the congestion charge zone, which automatically read the registration plates of cars. If the driver does not pay the charge then a fine will be imposed. Similar systems are being developed as a means of locating cars reported stolen.

Transport safety

A CCTV system may be installed where an operator of a machine cannot directly observe people who may be injured by unexpected machine operation. For example, on a subway train, CCTV cameras may allow the operator to confirm that people are clear of doors before closing them and starting the train. Operators of an amusement park ride may use a CCTV system to observe that people are not endangered by starting the ride. A CCTV camera and dashboard monitor can make reversing a vehicle safer, if it allows the driver to observe objects or people not otherwise visible.

Outside the UK

The use of CCTV in the United States is less common, though increasing, and generally meets stronger opposition. In 1998 3,000 CCTV systems were found in New York City."You're being watched, New York!," 11 March, 2002 ''BBC'' There are 2,200 CCTV systems in Chicago."Is Chicago safe from a terrorist attack?," ''Chicago Sun-Times'' In the last few years particularly, the percentage of people in the U.S having installed a security camera system has increased dramatically. Global Security Solutions with the help of Zone Tech Systems first announced the launch of IP surveillance in the US security industry by partnering up with Axis Communications (an IP pioneer). Today's CCTV market has transformed the shift towards IP-based security products and systems, and is often touted as an example of a disruptive technology that has had – and will continue to have – profound consequences for the electronic security industry as a whole."Tulsa!," 11 March, 2009 ''GSS'' In Latin America, the CCTV market is growing rapidly with the increase of property crime."Latin American Physical Security Market Growing Rapidly," 8 October, 2009 ''Security Magazine''

Criminal use

Criminals may use surveillance cameras, for example a hidden camera at an Automated Teller Machine|ATM to capture people's Personal Identification Number|PINs without their knowledge. The devices are small enough not to be noticed, and are placed where they can monitor the keypad of the machine as people enter their PINs. Images may be transmitted wirelessly to the criminal.

Privacy

Opponents of CCTV point out the loss of privacy of the people under surveillance, and the negative impact of surveillance on civil liberty|civil liberties. Furthermore, they argue that CCTV displaces crime, rather than reducing it. Critics often dub CCTV as "Big Brother (1984)|Big Brother surveillance", a reference to George Orwell's novel ''Nineteen Eighty-Four'', which featured a two-way telescreen in every home through which The Party would monitor the populace. More positive views of CCTV cameras have argued that the cameras are not intruding into people's privacy, as they are not surveilling private, but ''public'' space, where an individual's right to privacy can reasonably be weighed against the public's need for protection from presumptively innocent people .''Smile, the cameras are here to watch over you'' - ''The New Zealand Herald'', Tuesday 18 March 2008, Page A14 The recent growth of CCTV in housing areas also raises serious issues about the extent to which CCTV is being used as a social control measure rather than simply a deterrent to crime. However, since the September 11 attacks of 2001, many studies have suggested that public opinion of CCTV has grown more favorable. Many proponents of CCTV cite the attacks of the London Underground bombings as one example of how effective surveillance led to swift progress in post-event investigations. Quite apart from government-permitted use (or abuse), questions are also raised about illegal access to CCTV recordings. The Data Protection Act 1998 in the United Kingdom led to legal restrictions on the uses of CCTV recordings, and also mandated their registration with the Data Protection Agency. In 2004, the successor to the Data Protection Agency, the Information Commissioner's Office clarified that this required registration of all CCTV systems with the Commissioner, and prompt deletion of archived recordings. However subsequent case law (Durant vs. FSA) has limited the scope of the protection provided by this law, and not all CCTV systems are currently regulated. Private sector personnel in the UK who operate or monitor CCTV devices or systems are now considered security guards and have been made subject to Security Industry Authority|state licensing. A 2007 report by the UK's Information Commissioner's Office, highlighted the need for the public to be made more aware of the "creeping encroachment" into their civil liberties created by the growing use of surveillance apparatus. A year prior to the report Richard Thomas (lawyer)|Richard Thomas, the Information Commissioner, warned that Britain was "sleepwalking into a surveillance society". In 2007, the UK watchdog CameraWatch claimed that the majority of CCTV cameras in the UK are operated illegally or are in breach of privacy guidelines. In response, the Information Commissioner's Office denied the claim adding that any reported abuses of the Data Protection Act are swiftly investigated. Majority of UK's CCTV cameras 'are illegal' Telegraph.co.uk In the United States, there are no such data protection mechanisms. It has been questioned whether CCTV evidence is allowable under the Fourth Amendment to the United States Constitution|Fourth Amendment, which prohibits "unreasonable searches and seizures". The courts have generally not taken this view. In Canada, the use of video surveillance has grown very rapidly. In Ontario, both the ''municipal'' and ''provincial'' versions of the Freedom of Information and Protection of Privacy Act Freedom of Information and Protection of Privacy Act Text outline very specific guidelines that control how ''images'' and ''information'' can be gathered by this method and/or released.

Technological developments

[[File:West Yorkshire Police control station at Elland Road.jpg|thumb|right|A CCTV monitoring station run by the West Yorkshire Police at the Elland Road football ground in Leeds.]]

Computerised monitoring

The first closed-circuit television cameras used in public spaces were crude, conspicuous, low definition black and white systems without the ability to zoom or pan. Modern CCTV cameras use small high definition colour cameras that can not only focus to resolve minute detail, but by linking the control of the cameras to a computer, objects can be tracked semi-automatically. The technology that enable this is often referred to as VCA (Video Content Analysis), and is currently being developed by a large number of technological companies around the world. The current technology enable the systems to recognize if a moving object is a walking person, a crawling person or a vehicle. It can also determine the color of the object. NEC claim to have a system that can identify a person's age by evaluating a picture of him/her. Other technologies claim to be able to identify people by their biometrics. A problem for these types of systems is that they have been "oversold", meaning that poorly working systems have been sold which has undermined the trust for the technology. The technique will for instance not work well in large crowds, and the oversold feature of "unattended luggage detection" for airports have severe problems with determining whether or not a piece of luggage is really unattended. What the system can do is basically identifying where a person is, how he is moving and whether he is a person or for instance a car. Based on this information the system developers implement features such as blurring faces or "virtual walls" that block the sight of a camera where it is not allowed to film. It is also possible to provide the system with rules, such as for example "sound the alarm whenever a person is walking close to that fence" or in a museum "set off an alarm if a painting is taken down from the wall". VCA can also be used for forensics after the film has been made. It is then possible to search for certain actions within the recorded video. For example if you know a criminal is driving a yellow car, you can set the system to search for yellow cars and the system will provide you with a list of all the times where there is a yellow car visible in the picture. These conditions can be made more precise by searching for "a person moving around in a certain area for a suspicious amount of time", for example if someone is standing around an ATM machine without using it. Maintenance of CCTV systems is important in case forensic examination is necessary after a crime has been committed. In crowds the system is limited to finding anomalies, for instance a person moving in the opposite direction to the crowd, which might be a case in airports where passengers are only supposed to walk in one direction out of a plane, or in a subway where people are not supposed to exit through the entrances. VCA also has the ability to position people on a map by calculating their position from the images. It is then possible to link many cameras and track people through a building, this can also be done for forensic purposes where a person can be tracked between cameras without anyone having to analyze many hours of film. Currently the cameras have a hard time identifying individuals, but if connected to a key-card system it can find out the identities of people and the input for instance their ssnr as a tag over their heads on the filmed material. There is also a significant difference in where the VCA technology is placed, either the data is being processed within the cameras (on the edge) or by a centralized server. Both technologies have their pros and cons. The implementation of automatic number plate recognition produces a potential source of information on the location of persons or groups. There is no technological limitation preventing a computer network|network of such cameras from tracking the movement of individuals. Reports have also been made of plate recognition misreading numbers leading to the billing of the entirely wrong person. In the UK, car cloning is a crime where, by altering, defacing or replacing their number plates with stolen ones, perpetrators attempt to avoid speeding and congestion charge fines and even to steal petrol from garage forecourts. CCTV critics see the most disturbing extension to this technology as the facial recognition system|recognition of faces from high-definition CCTV images. This could determine a person's identity without alerting him that his identity is being checked and logged. The systems can check many thousands of faces in a database in under a second. The combination of CCTV and facial recognition has been tried as a form of mass surveillance, but has been ineffective because of the low discriminating power of facial recognition system|facial recognition technology and the very high number of Type I and type II errors|false positives generated. This type of system has been proposed to compare faces at airports and seaports with those of suspected terrorists or other undesirable entrants. Computerized monitoring of CCTV images is under development, so that a human CCTV operator does not have to endlessly look at all the screens, allowing an operator to observe many more CCTV cameras. These systems do not observe people directly. Instead they track their behaviour by looking for particular types of body movement behavior, or particular types of clothing or baggage. The theory behind this is that in public spaces people behave in predictable ways. People who are not part of the 'crowd', for example car thieves, do not behave in the same way. The computer can identify their movements, and alert the operator that they are acting out of the ordinary. Recently in the latter part of 2006, news reports on UK television brought to light newly developed technology that uses microphones in conjunction with CCTV. If a person is observed to be shouting in an aggressive manner (e.g., provoking a fight), the camera can automatically zoom in and pinpoint the individual and alert a camera operator. Of course this then lead to the discussion that the technology can also be used to eavesdrop and record private conversations from a reasonable distance (e.g., 100 metres or about 330 feet). The same type of system can track identified individuals as they move through the area covered by CCTV. Such applications have been introduced in the early 2000s, mainly in the USA, France, Israel and Australia. With software tools, the system is able to develop three-dimensional models of an area, and to track and monitor the movement of objects within it. To many, the development of CCTV in public areas, linked to computer databases of people's pictures and identity, presents a serious breach of civil liberties. Critics fear the possibility that one would not be able to meet anonymously in a public place or drive and walk anonymously around a city. Demonstrations or assemblies in public places could be affected as the state would be able to collate lists of those leading them, taking part, or even just talking with protesters in the street.

Retention, storage and preservation

The long-term storage and archiving of CCTV recordings is an issue of concern in the implementation of a CCTV system. Re-usable media such as tape may be cycled through the recording process at regular intervals. There are statutory limits on retention of data. Recordings are kept for several purposes. Firstly, the primary purpose for which they were created (e.g. to monitor a facility). Secondly, they need to be preserved for a reasonable amount of time to recover any evidence of other important activity they might document (e.g. a group of people passing a facility the night a crime was committed). Finally, the recordings may be evaluated for historical, research or other long-term information of value they may contain (e.g. samples kept to help understand trends for a business or community). Recordings are more commonly stored using hard disk drives in lieu of video cassette recorders. The quality of digital recordings are subject to compression ratios, images stored per second, image size and duration of image retention before being overwritten. Different vendors of digital video recorders use different compression standards and varying compression ratios.

Closed-circuit digital photography (CCDP)

A development in the world of CCTV (October 2005) is in the use of megapixel digital still cameras that can take 1600 x 1200 pixel resolution images of the camera scene either on a time lapse or motion detection basis. Images taken with a digital still camera have higher resolution than those taken with a typical video camera. Relatively low-cost digital still cameras can be used for CCTV purposes, using CCDP software that controls the camera from the PC. Images of the camera scene are transferred automatically to a computer every few seconds. Images may be monitored remotely if the computer is connected to a network. Combinations of PIR activated floodlights with 1.3Mpix and better digital cameras are now appearing. They save the images to a flash memory card which is inserted into a slot on the device. The flash card can be removed for viewing on a computer if ever an incident happens. They are not intended for live viewing, but are a very simple and cheap "install and forget" approach to this issue. Closed-circuit digital photography (CCDP) is more suited for capturing and saving recorded photographs, whereas closed-circuit television (CCTV) is more suitable for live monitoring purposes.

IP cameras

A growing branch in CCTV is ''internet protocol'' cameras (IP cameras), which allow homeowners and businesses to view their camera(s) through any internet connection available through a computer or a 3G phone. Internet protocol is a protocol used for communicating data across a packet-switched network using the ''internet protocol suite'', also referred to as TCP/IP.

Potential advantages

The following are potential advantages of IP cameras over traditional cameras:
- Two-way audio via a single network cable, allowing users to communicate with what they are seeing (e.g. gas station clerk assisting a customer on how to use the prepay pumps)
- Higher image resolution: IP cameras have a resolution of at least 640x480 and can provide multi-megapixel resolution and HDTV image quality at 30 frames per second.
- Flexibility: IP cameras can be moved around anywhere on an IP network (including wireless).
- Distributed intelligence: with IP cameras, video analytics can be placed in the camera itself allowing scalability in analytics solutions.
- Transmission of commands for PTZ (Panning (camera)|pan, Tilt (camera)|tilt, Zoom lens|zoom) cameras via a single network cable.
- Encryption & authentication: IP cameras offer secure data transmission through encryption and authentication methods such as WEP, WPA, WPA2, TKIP, AES.
- Remote accessibility: live video can be viewed from any computer, anywhere, and also from many mobile devices including iPhone, iPod touch, and Windows Live Messenger on selected cameras.
- Cost-advantage for larger systems. Studies show that for systems with less than 16 cameras, analog technology is cheaper, between 16 and 32 they are equal, and beyond 32 cameras, IP-based systems are more cost-effective.
- IP cameras are also able to function on a wireless network. Initial configuration has to be done through a router; after the IP camera is installed it can then be used on the wireless network These cameras are used in navigation purpose in defence forces.
- PoE - Power over ethernet. Modern IP cameras have the ability to operate without an additional power supply. They can work with the PoE-protocol which gives power via the ethernet-cable

Potential disadvantages

Potential weaknesses of IP cameras in comparison to other CCTV cameras include:
- Higher initial cost per camera, except where cheap webcams are used.
- Lack of standards. Different IP cameras may encode video differently or use a different programming interface, thus requiring matching the camera with the recorder.
- High network bandwidth requirements: a typical CCTV camera with resolution of 640x480 pixels and 10 frames per second (10 frame/s) in MJPEG mode requires about 3 Mbit/s.Network bandwidth and video storage space calculation by JVSG, January 17, 2008
- Technical barrier. Installation for IP cameras requires network settings including IP address, Dynamic DNS|DDNS, router setting and port forwarding, calling for the skills of a LAN technician or a CCTV tech who has studied these things.
- Opening to Internet results in a circuit being less closed than in classic CCTV. The system becomes open to hacking and hoaxing via internet (false bomb threats being called in while hoaxers watch on web, etc). Criminals can hack into a facility's CCTV system to observe security measures and personnel, thereby facilitating criminal acts and rendering the IP technology counterproductive.

Networking CCTV cameras

The city of Chicago operates a networked video surveillance system which combines CCTV video feeds of government agencies with these of the private sector, installed in city buses, businesses, public schools, subway stations, housing projects etc. Even home owners are able to contribute footage. It is estimated to incorporate the video feeds of a total of 15,000 cameras. 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 later usage in order to provide possible evidence in criminal cases."Chicago's Camera Network Is Everywhere", ''The Wall Street Journal''

Integrated Systems

One of the recent developments in the design of CCTV systems is dvr|Integrated Systems. These Systems consist of a Digital Video Recorder (Digital video recorder|DVR), a display monitor, and a built in Network card. Integrated systems look exactly like an LCD monitor. They can be used as simply a monitor, although their compact size makes them attractive for CCTV users. DVRs used in Integrated Systems have the capacity to record up to 14 days of footage, using high resolution recording. Integrated Systems have USB outlets so that recordings can be moved out onto a USB key or external hard drive and then later transferred on to a DVD if needed. Police investigations after a crime require that a copy of the CCTV recording be available to investigators. Integrated Systems that come with a Built in Network Card allowing users to connect remotely from the internet and view exactly what their cameras are viewing. This allows monitoring from anywhere in the world by simply having a computer and an internet connection. This feature is very similar to that of IP cameras. A famous incident is that of Jeanne Thomas a lady from Boynton Beach, Florida was able to watch her house get robbed and contacted police directly from her office at work. Popularity of Integrated Systems is increasing among small business owners and small offices. These users require a solution to their security needs that does not involve complex hook ups and difficult user interface.

Niche uses

- The use of CCTV at Hessdalen AMS where by it is used for discovery of unidentified flying objects.
- In the earlier days of television, some programs, and selected live sporting events, were demonstrated on closed-circuit television in theaters across the United States. The 1952 Metropolitan Opera production of Bizet's ''Carmen (opera)|Carmen'' was telecast complete by NBC on closed-circuit television. From 1965–1970, the Indianapolis 500 was shown live on closed-circuit television in many movie theatres. The first few WrestleMania events were shown in such a way as well. The first six Super Bowls were shown at special closed-circuit TV gatherings in the host cities, where the game was blacked out by National Football League rules in place at the time.
- In the UK, some places have installed talking CCTV, where the operator can talk to the people they monitor.
- British author Chris Roberts quips that “Closed-Circuit Television Cameras are proving very useful to low-budget TV producers throughout the UK for programmes along the lines of ''World’s Rudest Drunks Outside Nightclubs in the North of England''.” Chris Roberts, Heavy Words Lightly Thrown: The Reason Behind Rhyme, Thorndike Press,2006 (ISBN 0-7862-8517-6)

CCTV countermeasures

Unless physically protected, CCTV cameras have been found to be vulnerable against a variety of (mostly illegal) tactics:
- Some people will deliberately destroy cameras. Some outdoor cameras, such as those employed by the Chicago Police Department, have bullet-resistant housing.
- Spraying substances over the lens can make the image too blurry to be read.
- Laser pointers can temporarily blind cameras, and higher powered lasers can damage them. However, since most lasers are monochromatic, colour filters can reduce the effect of laser pointers. However filters will also impair image quality and overall light sensitivity of cameras (see laser safety article for details on issues with filters). Also, complete protection from infrared, red, green, blue and UV lasers would require use of completely black filters, rendering the camera useless.
- For wireless networks, broadcasting a signal at the same frequency of the CCTV network is reported to be able to jam it.

References

External links

- Space Shuttle External Tank and Solid Rocket Booster Camera Systems
- Cameras Monitor Rocket Launch
- UK Government pro-CCTV campaign
- Assessing the Impact of CCTV, a UK Home office study on the effectiveness of closed-circuit television
- The Register story: Face recognition useless for crowd surveillance
- CCTV Guidance notes from the UK Information Commissioner's Office
- CBC Digital Archives - The Long Lens of the Law
- The Urbaneye Project on CCTV in Europe
- CCTV:Constant Cameras Track Violators National Institute of Justice Journal 249 (2003). Washington, DC: U.S. Department of Justice.
- CCTV Surveillance in Airports & Ports: Case Studies Category:Surveillance Category:Security technology Category:Crime prevention Category:Warning systems Category:Applications of computer vision Category:Law enforcement Category:Public safety Category:National security Category:Law enforcement techniques Category:Security engineering simple:Closed-circuit television
- Public Space CCTV in Scotland: Results of a National Survey of Scotland's Local Authorities

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