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Guide to Closed Circuit TV (CCTV)

TRUSTED - Target Recognition Using Surveillance Technology for Evidence and Detection - A campaign to improve the effectiveness of existing video surveillance security systems.

CCTV Camera Operation - in a little more detail (continued)

- General Background Information -

So you'd like to find out more about analogue CCTV cameras .... be patient my friends, there's a lot to get through.

Doktor Jon promises to be gentle with you, so we'll try and start with a basic oveview of the main technical points, listed on a CCTV camera specification sheet. (It's important to remember that any figures quoted for a piece of electronic equipment, should be taken with a pinch of salt; just because a car (automobile) is supposed to travel 35 miles on a gallon of fuel (in a laboratory), doesn't mean it can actually achieve that when you take it out for a drive!.

First up, there are 3 location specific factors for cameras (the scanning system, power supply and dimensions), and 6 key areas to consider when looking at a units overall performance.

To begin with, the Scanning System actually refers to the number of lines which electronically make up the picture. At the most basic level, there are effectively two main systems in operation around the world (excluding High Definition which does not yet have a secured place in the world of video surveillance).

These are 'EIAJ' which is an international standard for 525 horizontal lines captured at 30 framers per second, (widely used in the Americas and much of Asia); and 'CCIR' which works on 625 horizontal lines captured at 25 frames per second, this being the standard throughout Europe, Australasia and much of Africa.

The terms EIAJ and CCIR are normally only applied to black and white (monochrome) equipment, because (would you believe it!) there are actually three main colour scanning systems, which relate to the way colour (or chrominance) information is encoded onto the monochrome (luminance) signal.


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