The transmission of video over the phone line is not new. Commonly known as slow-scan video, this method enables users to conduct surveillance activities from a remote location without installing a dedicated coaxial cable or establishing some kind of microwave or radiated- RF link between the monitored location where the camera is and the operator.

Recently, however, digital technology has made it possible to improve the typically slow refresh times associated with yesterday's slow-scan technology. Dubbed by some as "fast-scan," the result has rendered a remarkably efficient method of controlling cameras over the phone line in a close-to-real-time fashion. For example, where it once took 8 to 16 seconds to transmit one frame of video using the older analog, slow-scan method, pictures can now be transmitted at the rate of 8 to 10 frames every second for low resolution images, or 1 frame in 4 seconds for higher resolution images.

These over-the-phone-line camera control systems also provide near-real-time camera control and selection. This usually includes control over pan-and-tilt mechanisms, lens focus and zoom. Not only does this refer to prepositioning, but also to the preview of solicited changes in camera position.

When performing a pan or tilt maneuver, for example, the operator is able to see in near real time the effect of each command enacted at the remote sight through a small window. Although the resolution of the image shown in the window is too low for identification purposes, it gives the operator a quick idea of where the camera is pointed. As images are then refreshed at the selected rate, the operator will then see the delayed effect of his or her commands on screen later.

Security with this type of system is usually performed at both sending and receiving ends. For example, before an operator can dial up a remote site, he or she must enter a unique passcode. A unique identification number is also encrypted in the software on both ends so when an operator dials up the "transmitter" at the remote site, the identification number at the "receiver" is checked. In some cases, connection is then severed by the transmitter and the transmitter then dials up the receiver. This feature assures that the proper receiver gains control of the system.

Computerized Camera Control - On-site computer-driven camera control systems also provide a myriad of features and benefits unequaled by yesterday's standards. Using a soft screen- generated or hard keyboard, users can run sequential camera tours based on any number of criteria. Use of a soft keyboard is usually accompanied by the implementation of a mouse and a Windows-based softwareprogram.

Like their microprocessor counterparts that use embedded firmware, computerized camera control systems provide presets so when a door or motion detector are violated, cameras are automatically returned to "home" and lens focus and zoom settings are performed.

Computerized systems also provide other benefits, such as the retention of camera images for personnel and visitor identification, the retention of individual video frames during alarm, and the integration of alarm devices and access control functions.

Return To Section Index

BACK	NEXT