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Guide to Closed Circuit TV (CCTV)

CCTV cameras on the move

OVER THE TOP (OTT) PAN & TILT (P/T) HEADS

Although Side Mount and Over the Top pan and tilt heads do pretty much the same thing, allowing unrestricted movement of the camera assembly, the advantage of using a well balanced OTT assembly can be outweighed by one obvious disadvantage.

If a weatherproof housing is fitted with a front mounted wiper unit, the bolt on box can with some models, strike against the Pan and Tilt head when the camera is tilted downwards, usually to a maximum of about 70 degrees. So with this set up, it can create a blind area directly below the camera.
One obvious way around this which Doktor Jon has used on a number of occassions, is to have the wiper unit built inside a ‘Deep Base’ housing. This ensures that all the equipment, including the Telemetry receiver card are housed inside a flat bottom unit, which can then be tilted downwards a full 90 degrees without any problem.

As with other camera movement devices, both S/M and OTT types are available for indoor and outdoor use, and are capable of revolving up to approx 345 degrees, and tilting up 20 (more with the SM type), or down 90 degrees, with adjustable ‘end stops’ (normally fitted internally) to limit the arc of travel.
They are available with a wide range of options for different operating voltages (e.g. 240v, 110v, 24v AC 12 or 24v DC ), using highly efficient ‘syncronous’ AC, or variable speed ‘stepper’ DC motors with heavy duty gear assemblies.

Autopan is readily available as an option, and some can be supplied with ‘preset pots’ which allow positional information to be communicated directly to the telemetry control receiver. Using this advanced technique, the Pan and Tilt head is capable of being ‘programmed’ to move to a number of specific horizontal and vertical settings, simply by the press of a couple of buttons on the control unit. The option of variable speed motors, can provide a much finer level of control, which is useful for a Control Room Operator, particularly if the camera is fitted with a powerful zoom lens set to a high magnification as used in a Town Centre type CCTV system.

With units available for different weight capacities, from 3 Kgs. (miniature internal) up to 50 Kgs. heavy duty external, the important thing to remember is that heavy snow or high winds, or indeed a combination of both, can significantly strain the gearing and cause the unit to fail; so when choosing an outdoor P/T head, Doktor Jon recommends that you calculate the weight of the camera assembly, then allow 50 - 100% spare capacity for bad weather (e.g. for an 11Kg. housing load, select a P/T head with around 20Kgs. capacity).

Variable Speed Pan and Tilt Heads>

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