The twin goals of any security system are threat prevention and threat intervention. If you can, prevent; if you can’t, intervene. When you have to intervene you need as much information as you can get about the nature of the threat. Security sensors provide at a minimum, detection of a threat and at best, identification of the threat. Video surveillance is the most critical distinction between these two concepts.                    

A video signal can substitute for

eyes-on-the-scene, but to what

extent depends on the camera and

distribution system. A picture can

easily be used to detect an in intruder,

but how well can it identify

the intruder? It depends on the video

format and bandwidth of the distribution and switching system. Until recently, the standard surveillance camera generated a composite video (NTSC) signal, like that on broadcast television. Composite video makes pretty pictures, but the bandwidth of less than 5MHz tells the story and there isn’t a lot of detail. A face might be recognizable but you wouldn’t be able to read the numbers on a license plate or the label on a container.

To identify the nature of an intrusion, you may need more information than NTSC can provide, and the key element is in getting and retaining the detail. Pictures have information about brightness (Y, or luminance), and about color (C, or chrominance). You need both, but there is much more detail in the luminance. The first step is to separate the Y elements from the C elements. This means you need two, three, four, or even five wires to carry a high-resolution video signal. A one standard two-wire system is known as Y/C, or S-video. There are two standard three-wire systems: RGB, and YPbPr, and four and five-wire systems called RGBS and RGBHV (the VGA output on computers is an RGBHV system).

As the resolution (detail) goes up, the bandwidth of the cabling, switching, and distribution systems must go up too. Typical bandwidths for composite video are 4.5MHz, and a standard Y/C signal requires 6MHz to be fully resolved. An analog HDTV signal requires 25MHz or more, and a system switching a simple RGBHV signal (like SVGA) needs 36MHz of bandwidth. Some higher resolution video requires 100MHz to 200MHz (so-called XVGA and UXVGA). A video surveillance system design team needs to know more than just how many points of video will be monitored. It also needs to know what degree of detail the video is expected to provide, to chose an appropriate video format, and then to insure that the cabling, switching, and distribution equipment can handle the video format he has chosen.

QuickSet International can provide exactly the right elements to suit the level of detection/identification your video security system requires. From rugged precision positioning systems, to standard- or high-definition cameras, to signal switching, distribution, and display devices, a

QuickSet system gathers the picture resolution you need and preserves the detail all the way through the system.

By Stefan Seigel