ABSTRACT
At its simplest, CCTV comprises a camera, coupled with a cable to a display monitor. It was this type of system in the early days of CCTV monitoring that was popular in many retail establishments, since it was an “a ordable, do it your self, self contained system” [Constant and Turnbull, 1994:3]. ese early systems were o en extended to connect up to four cameras to the monitor, the images from which could be displayed individually or in a preprogrammed sequence. e cameras were generally static and had a xed focal length. e next innovation was to add a video recorder, enabling the image displayed on the monitor to be recorded on videotape and played back at a later time. To this was added the ability to move the cameras in either the horizontal or vertical plane, o en coupled with the capability to zoom, by permitting variable camera focal length. ese fully functional cameras are o en referred to as pan, tilt, and zoom (PTZ) cameras. e recording of images has also undergone considerable change. e sheer volume of tape required to capture the images of, say, a four-camera system recording in real time could be overwhelming.* e solution has typically been to “multiplex” the monitoring and recording so that images from four or more cameras are displayed on each screen and captured on a single tape. Doing this, of course, decreases the quality of each individual image, but it lessens the number of tapes required. However, it still requires the tapes to be changed every three hours. e solution to this problem has been to install time lapse recordings, so that rather than recording each camera in real time, the recording is updated at a slower rate.†
Many, particularly larger, CCTV systems incorporate the range of more advanced technical capablities, consisting of a number of fully functional PTZ cameras coupled, not just to a monitor, but to a recording device as well. Yet Gill and Spriggs [2005:1]. have noted that there is a “tendency within the criminological literature to discuss CCTV as if it were a single measure, CCTV systems can di er quite markedly.” Indeed, in a survey of CCTV in London, McCahill and Norris [2002] found that three quarters of institutions had xed cameras only, nearly one in ten (8%) had no recording facility, and a third (30%) did not have the capacity to multiplex the images.
