CCTV Systems
By John W. Colley

Grill The CCTV Expert
November, 2003 Issue

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John W. Colley

Our Company has always used coaxial cable for our closed circuit installations. We have received literature on equipment that is two wires unshielded cabling for video installations. Can you tell us the video quality I can expect by using this equipment please?

Very high quality video pictures can be sent over Unshielded Twisted Pair (UTP) wires, provided that suitable cable slope equalizers and amplifiers are provided to completely off-set the losses incurred when the video signal traverses the UTP cable pairs. When this is done, the picture received at the far end of the cable will be every bit as good as the Camera, Recorder, and Monitor are able to produce, with no degradation due to losses in the intervening transmission facilities, whether UTP, Coaxial Cable, or Impedance Converters such as senders and receivers. In fact, once the cable losses have been correctly equalized, further picture quality improvement can only be achieved by using superior quality Cameras, Recorders, and Monitors.

Many CCTV installers have found that high quality Cameras, Recorders, and Monitors do not seem to provide better overall picture quality than lower quality terminal equipment when used on long UTP transmission facilities. The reason is simple. All of the crisp high quality detail created by the high quality terminal equipment (cameras, etc.) has been lost trying to get through the losses created by the Senders, UTP wires, and Receivers. The only way to upgrade picture quality is to correct the transmission facility losses by using cable equalizers and amplifiers to offset these losses. It is also very important to realize that, in the case of twisted wire equalization, "more is not better". Only the correct amount of equalization will do. More of the same will only make the video picture worse, instead of better.

Equipment and components are available to approach the installation-using individual to multiple input capability.


Has anyone discussed the fact that several new cameras today being sold do not appear to have the standard 75-Ohm video output from the cameras?

In the past, CCTV cameras could be counted on to have proper 75 Ohm source impedances, but recently there have been a rash of cameras showing up on the market that do not have a 75 Ohm source impedance. In fact, they exhibit almost zero output impedance even though the specification sheets that come with them specify 75 ohms! It even appears that some cameras do not meet their own specifications and could be returned for not meeting their own published specifications.

Can you give me a recommendation on ground loop issues with two wire UTP devices for a closed circuit television (CCTV) camera? UTP is a new product. We used to have ground loop issues with coaxial cable and now it seems we have them on UTP?

Ground loops do develop on UTP CCTV installations as well as coaxial cables. Please explore a ground-loop blocker equipment for twisted pair wire installations. The proper equipment is an active device used in conjunction with any Unshielded Twisted Pair video transmitter or "Balun" to eliminate Ground Loop Interference and picture quality problems in new and existing twisted wire CCTV video installations.

The unit is installed at the monitor site where the video twisted pair signals come together or at any intermediate point where video signals are monitored.

This device controls and corrects up to four channels of CCTV video, each channel is separately adjustable for Video Level and Picture Sharpness. A built-in active ground loop blocker removes the 60 Cycle Bars from the CCTV signal even after they have become part of the video signal. This ground loop isolator will prevent 60 Cycle "Hum Bars" from degrading your twisted pair wire CCTV system.

If a level control is provided you can adjust to overcome losses due to long wire runs up to 3000 feet, small wire gage or quality, and improper camera source terminations.

Some units also provide a picture sharpness control which can be used to restore picture quality to its original sharpness due to long wire runs, poor quality twisted pair wire or wire used in wet locations in twisted pair "Balun" transmission installations. It will also restore the video color-burst on a color camera to improve color camera operation on long wire runs.

Could give me an idea of how video digital recording watermarking works and what type of technology is used.

Each video digital recording manufacture approaches water marking differently. I am most familiar with wavelet watermarking compression. In general, the wavelet-compressed images are evaluated to determine if they contain the expected image register for our the compression algorithm. Our manufacture process will indicate if the wavelet image is decompressed, they will be able to recognize the file as a tampered image.

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John W. Colley is president of Integrated Security Systems, Ltd. and has been in the security industry for over 25 years, beginning his experience in the CCTV segment of security and gaining knowledge through field experience, manufacturer training and designing systems to meet customer needs. Colley started his security integration firm 18 years ago, providing design, engineering, installation and service to commercial accounts using integrated systems. Send your CCTV/Surveillance questions to jwc@securityiss.com.