CCTV

Jan 1, 2001 12:00 PM, ACCESS CONTROL & SECURITY SYSTEMS INTEGRATION STAFF

Monitor For industrial/commercial applications

Features: 800 lines of resolution, over/under scan switch, dual video inputs with selectable composite and S-video, built-in audio with loudspeaker control, automatic voltage selector. VMC-8618 SANYO Chatsworth, Calif.

Camera Mobile thermal imaging Designed to be sensitive to thermal energy emitted by people and objects.

Features: 91 pounds, mountable on vehicles or in fixed mount applications, hybrid ferroelectric focal plane array detector, weather-proof. ProtectIR 4000B RAYTHEON COMMERCIAL INFRARED Dallas

Multiplexers Fiber-optic Designed to transmit multiple channels of video over a single fiber optic.

Features: models available for multiplexing from two to eight channels of video on single mode or multi-mode fibers. MERIDIAN TECHNOLOGIES INC. Elmont, N.Y.

Multiplexers Duplex operation Available in 4-,9- and 16-camera versions.

Features: VCR alarm mode, video loss alarm, RS-232/485 interfaces, and rack-mounting kit. CAPTURE RICHARDSON ELECTRONICS SECURITY SYSTEMS Houston

Digital recorder Simultaneous recording, playback, and viewing Video images are first loaded onto the hard-disk drive, and then periodically compressed and transferred onto the DV drive.

Features: built-in modularly expandable duplex multiplexing, programmed to record in multiple modes, can accommodate up to 16 cameras, five preset recording modes. HSR-2 SONY ELECTRONICS INC. Park Ridge, N.J.

Video server MPEG

Features: MPEG1 up to 30 f/s (32kps-1.6Mbps), MJPEG up to 8/f/s, snap shot, MPEG1 Layer2 audio. MG120S HITACHI AMERICA LTD. San Diego

Camera Small enough to fit in a single gang box

Features: IR-optimized 1/3-in. CCD, pan/tilt mount, optical-acrylic window, voltage regulator. EB-S300 EXTREME CCTV SURVEILLANCE SYSTEMS Burnaby, British Columbia, Canada

Anyone investing in a good CCTV security system knows the importance of high-resolution cameras. A good CCTV surveillance accepts about 480 TV lines as high resolution. At the bottom end of the spectrum, video-conferencing and the Internet don't usually come into the high-resolution debate.

A few digital video storage systems store images at better than 450 TV lines of resolution although the majority achieve about half that with 240 lines, these are often sold as "high-resolution."

Resolution is a complex subject, but one thing is obvious - you must have a balanced system as the entire system is limited by the weakest link in the chain. Having a high-resolution camera, recorder and monitor makes sense. The same can be said for having a low-resolution camera, recorder and monitor, but never mix the two.

Most digital storage systems capture 240 scan lines although 480 lines are possible, for CCTV surveillance, the interlacing of two 240-line fields gives more disadvantages than advantages. The industry is fairly well agreed, and scan lines are not where the confusion lies. The confusion is the horizontal resolution or X-axis measured in TV lines and the number of black and white lines that can be drawn from the top to the bottom of the image. Standard numbers are:

- Broadcast NTSC - 330 TV lines

- VHS - 240 TV lines

- SVHS - 400 TV lines

Digital systems tend to be measured in pixels rather than TV lines, but when matching components a common "language" has to be chosen. If cameras continue to output analog signals, the common language is likely to remain TV lines. If a digital storage system either captures, stores or displays X pixels in the horizontal direction, then its possible TV lines equivalent is 75 percent of that.

- CIF Resolution (theoretical max)(i.e. 320x240) equates to 240 TV lines

- High-Resolution (theoretical max)(640x240) equates to 480 TV lines

In practice there are many reasons why this theoretical maximum will not be reached. A better camera will always look better than a poor camera, even on a low-resolution display. But this maximum limit is still the ceiling.

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