CCTV: The tale of the tape

Building Operating Management, May 2000 by Dingle, Jeffrey A

CLOSED-CIRCUIT TELEVISION SYSTEMS OFFER MORE THAN JUST A PHOTOGRAPHIC RECORD OF EVENTS

A woman is kidnapped in Lexington, Ky., and forced by her abductor to go on a shopping spree. In Houston, a citizen is shot and robbed at an automatic teller machine (ATM). A bomb explodes in Oklahoma City, killing eight Federal agents and more than 100 civilians.

Reliable eye witnesses to a crime are difficult to come by even under the best of circumstances, but all three of these incidents had something better than an eyewitness: photographic evidence. All three were recorded on video tape by closed-circuit television (CCTV) systems.

CCTV systems offer a useful addition to facility security systems. These systems are designed to offer an additional set of eyes, provide a permanent record of activity and to be where the protection professional or investigator cannot or does not want to be.

Like other types of surveillance, electronic surveillance by CCTV generally falls into one of two categories: specific surveillance and general surveillance. The former involves looking for a specific incident or persons. Equipment is portable and temporary, and often involves warrants. Specific surveillance means watching a target location or person and manually turning cameras and recorders on and off when the targeted suspect is seen. Specific surveillance is usually associated with an investigation, and is conducted in response to a specific incident, with a specific result expected.

FOREVER LOOKING

In what CCTV expert Charlie Pierce calls "the unblinking eye," general surveillance involves cameras and recorders that are permanently installed and aimed in general directions. The intent is to have a record of a general area, without a specific result expected. General surveillance is usually associated with general facility management. Continuous coverage is provided for areas that are high risk, such as an ATM, or for which there is a high probability of recording significant information, such as an exterior entrance into a facility.

In general surveillance, video tape is constantly recorded and the tape is held for a period of time. Tape can be reviewed (and saved) if there is reason to believe the camera may have caught something. Tapes need to be held long enough - usually 30 days - that the content still exists if a problem is discovered later. In order to hold a tape for 30 days, 31 tapes are need for each recorder used. One tape is used each day of the month, then used again on the same day the next month.

In order to record constantly, a time-lapse VCR is used. A timelapse recorder is similar to a regular VCR, but records at a slower speed, one frame at a time. A frame will be recorded, and after a specified number of seconds, another frame will be recorded. The time between frames determines how many hours can be recorded on a single tape. Most commercial video recorder units offer a choice of multiple record and playback speeds, ranging from 2 to 960 hours.

The slower the speed, the greater the time-lapse between the recording of images. In the 960 hour recording mode, an image is captured every 8 seconds.

Essential to any video surveillance system is a time-date generator. A time-date generator constantly displays the time and date onto the recorded field of view. This allows for an exact record of the time and date when an incident is recorded. Most time-lapse recorders have a time-date generator built in.

CCTV CATEGORIES

CCTV systems are designed and built in two basic categories, covert and overt. One of the inherent advantages of security devices is that they are usually visible. This visibility greatly adds to the deterrent factor useful in overall security operations. Overt security devices, by design, deter people from committing criminal acts.

Covert systems, on the other hand, are not seen. Covert security devices offer much less of a deterchance of catching a criminal in the act of committing a crime. They are hidden, and most people will not know they exist. Covert systems are used in permanent applications when it is not appropriate to have overt surveillance systems, such as some dignitary protection situations, and in temporary situations where a specific item or area is placed under surveillance to gather information.

Overt systems are clearly visible to the public and employees. A camera hanging near the front entrance is thought to be a deterrent; the knowledge that all activities are recorded is often by itself enough to prevent criminal activities. Camera housings may help as well. Department stores often have many more camera housings than cameras. It's the job of the shoplifter to figure out which housings have cameras and which don't.

A CCTV system is comprised of a camera, transmission method, monitors and a recorder. State-of-the-art cameras are now smaller than a pack of cigarettes, and can transmit in color or black and white.

While at first color seems to be a better choice, often black and white is functionally preferable. Color systems do not work very well in low light applications, and variations in types of security lighting can skew color accuracy.