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Guide to Closed Circuit TV (CCTV)

So would you like to play "Spot the CCTV Camera?". Eagle eyed visitors may recognise the profusion of street furniture, surrounding a single heritage dome camera keeping watch over part  of Londons' prestigious Oxford Street shopping area.

CCTV cameras on the move


The main reason for using a variable speed P/T head is actually very obvious if you think about it.

With a powerful zoom lens set to its maximum magnification, this can be quite a challenge to control effectively. If you imagine pulsing the pan button for half a second, this can easily equate to a displacement of perhaps five metres away from your target; so ‘locking on’ does require a fair degree of precise control.

Using powerful low voltage DC motors, and a variable speed telemetry control system, the camera can be made to ‘inch’ very gradually or ‘fly’ at high speed to a preset position, ready for manual fine tuning.

One noticeable difference with the DC motors though, is whereas the AC syncronous type are virtually silent in operation, the variable speed units certainly let you know they are there! Another point to consider is that, despite the inherent strength of any modern Pan and Tilt head, most DC or variable speed units, do not tend to have the same weight capacity as their standard AC cousins.

Despite the cost and operational limitations of variable speed P/T heads, they continue to be used for a wide range of applications; although longer term, there will undoubtedly be a growing shift towards the adoption of complete integrated 'Dome' system cameras.

We have briefly touched on the term 'preset positioning', but it might be appropriate to expand on this a little further, at this stage.

The simple principle is that with a correctly configured Pan and Tilt head (which is nearly always going to be a variable speed unit), the control system can be manually programmed to memorise a numberof set positions (the lens zoom and focus settings can also be held if the correct lens is fitted). So whenever the operator enters the preset position number, or an alarm is activated, the PTZ camera will automatically go to its pre programmed setting (These presets are not generally 100% accurate, so manual fine tuning may well be required).

Information on Specialist Pan and Tilt Heads>

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