What is CCTV?
Closed circuit television (CCTV) is a surveillance technology. More specifically, it is "a system in which a number of video cameras are connected in a closed circuit or loop, with the images produced being sent to a central television monitor or recorded"2. The term closed circuit television was originally used to differentiate between public television broadcasts and private camera-monitor networks. These days CCTV is used as a generic term for a variety of video surveillance technologies.
Although some systems are extremely sophisticated, employing bullet-proof casing, night-vision capability, motion detection, and advanced zoom and automatic tracking capacities, many existing systems are more rudimentary. More common CCTV installations include a number of cameras connected to a control room where human operators watch a bank of television screens.
Many (but not all) will have a recording facility that works in one of the following ways:
- Recording the images from a selected camera
- Using multiplex recording where the image switches from camera to camera thus allowing one tape to see every camera view on a rotating basis
- Employing digital technology to record images from multiple cameras at once
Often an operator can pan, tilt, and zoom a number of cameras. As the technology has developed, cameras with a full range of movement and control facilities have become the norm, and it is likely there will be continual improvements in optical and digital zoom, color, and pixel† resolution, all of which will enhance image quality.
† A pixel is an abbreviation of picture element. Pixel resolution refers to the quality of an image. For example, a digital camera with a resolution of 640 x 480 pixels (640 pixels wide by 480 pixels high) will record a better quality image than a camera with a resolution of 320 x 240 pixels. Higher resolution images are generally of better quality, but increased storage capacity is required for better quality recording.
Including the human element, we can categorize systems into passive—where banks of recording devices record images that can be replayed if a crime is reported, though nobody actively monitors the images, and active—where a person sits and monitors a series of displays in real time. In reality, many systems are a hybrid, where recording devices record all images, and an operator scans from monitor to monitor, concentrating on some and ignoring others.
Although most CCTV schemes employ overt cameras, which are obvious (see Figure 1), it is possible to find systems in which cameras are mounted into protective shells or within frosted (polycarbonate) domes. Often termed semi-covert, these camera systems make it more difficult for people under surveillance to determine if they are being watched, as it is usually impossible to figure out in which direction the camera is facing (see Figure 2). Some cameras employ dummy lenses to conceal the surveillance target. The advantage of using a one-way transparent casing is that it provides for the possibility of retaining the overt impression of surveillance—and hence a deterrent capacity—without having to place a camera in every housing or to reveal to the public (and offenders) the exact location under surveillance3.
In addition to the cameras, the cabling to feed images to the monitors, and the recording devices, a CCTV system also requires an operator to watch the monitors or review the recordings. Because of this, a full description of CCTV should not ignore the human element. Reviewing video, acting on the information, and preparing video evidence for court all create a potential need for ongoing office space and personnel costs over and above any initial capital expenditure. There may also be extra demands placed on local law enforcement as a result of increased surveillance of an area. With increased surveillance, more public order crime may come to the notice of police. With technological and personnel costs, CCTV comes at a considerable price. Though the technological costs continue to fall, the human costs do not. Therefore, you must give CCTV serious consideration before you purchase and install a system to combat a crime problem. A later section details some of the factors to consider before deploying a CCTV solution.
Fig. 1:With an overt CCTV camera, the public (and offenders) can clearly see the surveillance camera and determine the direction in which it is facing. (Photo credit: Jerry Ratcliffe)
Fig. 2:This semi-covert CCTV camera may have a crime prevention advantage over an overt system because offenders can never be sure in which direction that camera is facing. (Photo credit: Jerry Ratcliffe)
In summary, there is a range of CCTV configurations available. A complete CCTV system (for the purposes of this report) comprises:
- One or more cameras that view a public area
- A mechanism to transmit video images to one or more monitors
- Video monitors to view the scene—usually accompanied by recording devices such as a time-lapse video recorder or computer hard drive for digital images
- A viewer or camera operator, such as a police officer or security guard
Variations to this basic configuration include:
- The ability to transmit images across the Internet
- Motion sensors that activate the camera when activity is detected
- Normal or infrared lighting to enhance picture quality at night
- A pan and tilt capacity that allows an operator to change the camera's viewing direction, zoom, and focus
More advanced systems can include limited facial recognition technologies or estimate the location of firearm incidents, though more advanced systems often rely on other technology. For example, a facial recognition program is of limited value unless it is linked to a computer database of suspect photos. Intelligence systems that can detect unusual activity (such as fights in the street) are also under development4.
In addition to determining if you want to install a CCTV system (and what type), you should consider how sophisticated you want it to be and if you have the resources to support it.
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Video Surveillance of Public Places
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