Closed-Circuit Television

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 (P2P), point to multipoint, or mesh wireless links. CCTV is often used for surveillance in areas that may need monitoring such as banks, casinos, airports, military installations, and convenience stores. It is also an important tool for distance education
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-based CCTV 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 the UK, where there are reportedly more cameras per person than in any other country in the world.
There and elsewhere, its increasing use has triggered a debate about security versus privacy.


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 Video Content Analysis (VCA), 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.


CCTV monitoring station run by the West Yorkshire Police at the Elland Road football ground in LeedsThe system identifies 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.


Surveillance camera outside a McDonalds highway drive-inMaintenance 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.[citation needed]

VCA also has the ability to track people on a map by calculating their position from the images. It is then possible to link many cameras and track a person through an entire building or area. This can allow a person to be followed without having to analyze many hours of film. Currently the cameras have difficulty identifying individuals from video alone, but if connected to a key-card system, identities can be established and displayed as a tag over their heads on the video.


Monitoring station of a small office buildingThere 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 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.[37] 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 recognition of faces from high-definition CCTV images.[citation needed] 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 technology and the very high number of 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.


Eye-in-the-sky surveillance dome camera watching from a high steel poleComputerized 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[clarification needed] 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.[citation needed] 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.[citation needed] 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.

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