NCJ Number
87840
Date Published
1983
Length
67 pages
Annotation
In covering the fundamentals of closed circuit television (CCTV) systems, this paper presents the functions of lenses, cameras, monitors, recorders, transmission means, and special equipment particularly suited for museum security.
Abstract
A large number of museum CCTV applications require only one television camera, such as for monitoring people entering and leaving the front lobby. Questions to be answered in the use of such a system deal with the camera and lens, the cabling, the monitor/switcher, and the lobby camera location. The essentials of a CCTV camera are the lens and the field of view (the scene that the camera 'sees'). All standard CCTV cameras use either a 2/3-inch diameter or 1-inch diameter vidicon image tube. Which tube to use is determined primarily by cost factors. A zoom lens provides for a range of focal lengths that can be dialed in, thereby accommodating a variety of fields of view with one lens. The majority of lenses used in CCTV applications, however, are fixed focal length lenses, which have a fixed field of view. Standard television monitors are available with screen sizes from 5-inch to 23-inch diameter diagonal, with the 9-inch monitor being most commonly used. There are many different types of video switchers available for connecting multiple cameras to a single or multiple monitors. The simplest type is a manual switcher, which permits choosing from a number of cameras for use with single video monitor. Once the single camera lens system has been mastered, most of the design for a multiple camera system has been accomplished. The principal question with a multiple system is whether a monitor will be used for each camera or a single monitor will be used for all cameras, with displays from each camera being obtained by an electronic switch. The choice will depend on preference, budget, and the number of people entering and leaving each camera area. For covert CCTV systems, equipment options include the high light power pinhole camera, manual iris pinhole lenses, auto-iris pinhole lenses, rigid fiber optic pinhole lenses, and the flexible optic pinhole lenses. A CCTV system can also be used for access control, as it permits visual identification. Photographic and graphic illustrations of systems and system elements are provided, along with a glossary of CCTV terms and references.