CCTV Systems
By John W. Colley

Grill The CCTV Expert
January, 2003 Issue

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Our retail customer is asking our company to locate CCTV cameras in a retail store near customer entrances. The customer wants positive identification of the person coming in the door. What should we do to give him what he wants?

Position the camera to view the door and select a lens that will give the customer a high quality facial view of the person. Several devices are available for you to view the scene to make the right lens selection. Always the best way is to take the actual camera there and show the customer what he will purchase. Another consideration is providing the right equipment for light variations. By selecting a CCD camera with an adequate pixel resolution, auto iris lens and camera with back light compensation circuitry the customer will have the best picture possible.

One of our customers is a city official, they asked what is the policy on the use of surveillance equipment in their office area.

General camera placement guidelines for use of CCTV are that CCTV is allowed in most business, commercial, education, municipal and retail areas. The exceptions are an area designated as an "employee/customer restricted area" i.e.: bathrooms, teachers/employee lounges, and employee lunchrooms. CCTV has been court tested and brought to the attention of US Congress by the ACLU. There have been attempts to further restrict CCTV in legislative bills but they have never been approved do to the heavy lobbing by the security industry.

What does JPEG image stand for in digital recording?

JPEG stands for Joint Photographic Experts Group this original committee wrote the standard for standardized image compression mechanism. JPEG is designed to compress gray scale images or full-color of natural real-world scenes. JPEG is designed to exploit known limitations of the human eye, notably the fact that small color changes are perceived less accurately than small changes in light.

These type image compression decoders can trade off decoding speed against quality, by using faster but inaccurate approximations to the required calculations. Encoders can also trade accuracy for speed.

What is color quantization?

A full-color 24 bit per pixel is required in the digital world for a full picture. Video capture boards and CD chips may not have the capability of processing 24 bit pixels. Usually they may use only 8 pixels. To view a full color picture the computer chooses an appropriate set of reprehensive colors not the full 24 pixels. This process is called "color quantization". The industry is working to improve the number of pixels to improve picture quality.

How well does JPEG compress images?

Images are very good. As the images are compressed in JPEG, the storage requirements are reduced. This provides more pictures to be stored. Color images will compress more noticeable than black and white images. In the gray-scale world, the file is smaller thus, less needs to be compressed.

What is CD-RW device?

A CD-RW is a compact recordable disc device that allows you to record erase and rewrite to the same CD disc. Most discs' hold about 74 minutes of audio or about 650MB of data. The security industry's digital recorders will also compress files that you may store on CD-RW. Each digital recording manufacture has to approve the CD-RW device to be used with their product.

I have heard video can interface with police radar guns.

Yes equipment is available to interface to radar guns. Data from the radar gun is converted to a readable format this data can be sent to a product that overlays the data onto the video picture. It is important to check first with the radar gun manufacture to be sure the gun transmits standard RS232 data information.

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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.