Closed TV circuit

The closed circuit television (in English closed circuit television, CCTV) is a video surveillance technology designed to monitor a variety of environments and activities. It is called closed circuit since, unlike what happens with diffusion, all its components are linked. Furthermore, unlike conventional television, this is a system designed for a limited number of viewers.

The circuit can simply be made up of one or more surveillance cameras connected to one or more video monitors or televisions, which reproduce the images captured by the cameras. Although, to improve the system, other components such as videos or computers are usually directly connected or networked.

They are fixed in a certain place. In a modern system the cameras used can be controlled remotely from a control room, where their pan, focus, tilt and zoom can be configured. This type of camera is called PTZ (pan-tilt-zoom). These systems include night vision, computer-assisted operations and motion detection, which makes it easier for the system to put itself on alert when something moves in front of the cameras. The clarity of the images can be excellent, it can be transformed from dark to light levels. All these qualities mean that the use of CCTV has grown extraordinarily in recent years.^{[when?][citation required]}

Surveillance through the use of CCTV is increasingly common in public spaces for crime prevention. The rationale for its use is that it deters potential criminals, can quickly alert police or security personnel to intervene, and helps people feel safer. However, the use of CCTV has a very high cost. For example, it is estimated that in the United Kingdom more than £250 million was spent on CCTV between 1992 and 2002, with this form of surveillance being one of the most funded.

A systematic review of 44 studies conducted in the United Kingdom, United States, Canada, Norway and Sweden determined that the use of CCTV has a modest impact on reducing crime. The results suggest that surveillance is most effective in preventing vehicle thefts in parking lots, and is less effective in urban centers of cities and towns, in public housing, and on public transportation. Likewise, it was determined that the effectiveness is greater when the camera coverage is broader, and that this has no effect on violent crimes.

CCTV main components

• Cameras, are those devices that capture the image of the protected place.
• Monitor, is the external component that allows us to see the images captured by the camera.
• Image transmission medium. It refers to the way the images are transmitted, which can be by coaxial cable, copper braided pair or optical fiber (the latter two commonly used in IP camera systems).
• DVR (Digital Video Recorder) digital video recorder or NVR (network video recorder) for IP cameras.

CCTV in video surveillance

Originally, video surveillance was carried out using closed circuit television. This technology uses analog video cameras, coaxial cable and video recorders. The cameras transmit a signal to a specific, limited set of monitors. CCTV systems typically include a fixed communications link between cameras and monitors, using wires and cables. This method records what is happening, but does not send you alerts. CCTV works like a video player, you have to change cassettes, picture quality is average, storage tapes wear out over time, and storage is bulky. Additionally, cameras, monitors, and recorders must be physically close enough to be connected by cables.

In this application the circuit will be composed, apart from the cameras and monitors, of a video storage device (DVR Digital Video Recorder, NVR Network Video Recorder) depending on the structure of the circuit, whether analog or based on IP networks, although combinations can be made depending on the needs of the site. The cameras can be fixed, with zoom, mobile or PT (Pan, Tilt) or PTZ (Pan, Tilt, Zoom) such as the so-called dome, due to the inverted dome shape they present, and cameras with a positioner, which They can be remotely movable. This movement can be done through a console or keyboard through which the various options of the software installed on it can be managed. A CCTV video surveillance system also includes devices such as: infrared lamps, twilight sensors, positioners, telephoto lenses, video analysis and intelligent video, etc. Camera technology currently allows, depending on the models, to capture thermal images in total darkness, or images in darkness illuminated with infrared that the eye is not able to see. In addition, many have video analytics that allow them, among other things, to: read license plates, read body temperature, delimit areas to create heat maps of people's movement, facial recognition, etc.