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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.

Everything you need to
control a CCTV system

If it’s time to move on from fixed cameras,
Doktor Jon has the lowdown on all that’s happening with CCTV Control Systems. When it comes to cameras, if you need to switch on, zoom in or turn around, it helps to know the basic facts, so for all you control freaks out there, let us begin ....


Historically, Hardwired Control systems, in other words, a simple arrangement whereby a piece of equipment, whether it be a pan / tilt head or a motorised zoom lens, is controlled by sending the correct driving voltages directly down a multicore cable (any cable with more than two individual conductors contained within an outer sheath, is generally described as a multicore), has been around since the earliest days of Closed Circuit Television.

Although there have been quite a range of basic hardwired controllers available for single cameras (some still available), the majority of complex multicamera installations that were set up in the ‘70s and early ‘80s, generally had custom built control panels with banks of selector switches for individual camera units.

Although Telemetry has really become the control system of choice in recent years, there is still a place for hardwired systems, particularly with basic single camera applications.

The main problems with direct driving a remote control camera have generally been cable length and cost. Whilst a decent quality multicore cable can become rather expensive over longer distances, the basic principles of electrical conductivity apply, so the further away the camera, the thicker the cable conductor needs to be, in order to overcome the problems of ‘voltage drop’.

For most applications requiring control of a P/T head, a zoom lens and a couple of ancillary switches (e.g. remotely switched lighting or a door release) a twelve core cable is normally adequate (zoom lens - 4 conductors, P/T head - 6 conductors + 2 spares), with 16/0.2mm conductors being a reasonable choice for distances of up to 100 metres or so.

Continued >>

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