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Line-fed video security systems are becoming an increasingly popular alternative to conventional CCTV technologies as more sophisticated multi-camera packages -- designed mainly for small to medium scale installations --  come on to the market. Line fed systems have already gained a foothold in the UK but the according to some manufacturers the picture across the rest of the EC is at best patchy.


The advantages of a line-fed system are fairly obvious; only one cable is needed to carry both the power to the camera, and the video signal from the camera, back to its camera control unit or CCU. Because of this there are fewer cables in the systems, which in turn means it's simpler to install and service, which can represent a valuable saving for both the engineer and the end-user.


However, one of the major benefits of line-fed cameras is flexibility, and because only one cable is needed it is easier to site cameras in remote and inaccessible locations, where it may be difficult or even impossible to lay on an mains supply. The flipside of that argument is that line-fed cameras can be more troublesome to set up and align as very few models have an accessible or on-board video output.  


From a manufacturing point of view line-fed cameras can help to rationalise model ranges and in theory one common design can be marketed in countries with widely differing mains supplies, only the camera control unit's power supply needs to be adapted to local conditions. In practice cameras and systems are modified to meet local standards, regulations and conditions.


In addition to power and video information the coaxial cables used in line-fed systems can carry a variety of other signals between the camera and its CCU. Examples include control pulses for pan/tilt heads, zoom lenses and manual focusing systems, camera housekeeping functions (heaters, fans, window wash/wipe etc.),  two-way multiplexed audio and, of course, alarm telemetry.


The cameras themselves cover a wide range of applications, from simple single-camera surveillance and access control, though to general-purpose, multi-camera systems with colour or monochrome operation. Line-fed cameras have not, as yet, had much of an impact on the specialist end of the market; the low-light performance of line-fed cameras is improving all the time and are comparable with conventional CCTV cameras , though it's unlikely there will be any major improvements in image resolution as it's currently impossible to send separated or Y/C formatted video signals down a single coaxial cable.


There are other disadvantages with line-fed systems worth noting, including higher cost, but cross-brand compatibility, or lack of it , is at or near the top of the list. Incidentally, this is the reason most frequently cited for the comparatively low level of interest towards line-fed CCTV in some EC markets. Line-fed cameras and control units, whether stand-alone or built into a video monitor are normally packaged together, and because there's no agreed technical standard for line-fed cameras and CCUs, there's little or no opportunity to mix and match products from different manufacturers, or integrate other, non line-fed cameras or devices other than standard peripherals, such as monitors and time-lapse VCRs. The power supply requirements of line-fed cameras is one example of the widespread variations; 12 and 24 volts DC supplies for the cameras are fairly common, though by no means the norm and there are several cameras that need a 24 volt AC supply. Other inconsistencies include camera and peripheral control protocols, the way genlock or sync information on multi-camera set-ups is processed, alarm triggers and even audio modulation systems.


Expandability can be another problem; most packages are limited to a maximum of four or six cameras, and each manufacturer will have only a small number of compatible cameras in their model range which can be used. Restrictions on the length of cable runs can also cause headaches in some installations. The actual maximum length varies from systems to system, and the type of cable used, some are as short as 200 metres, though most manufacturers recommend the camera is no more than 500 metres from the CCU. One or two systems can reach as far as 900 metres, and there are 'fixes' that can help extend the run a little further but noise, the resistance of the cable and it's effect on the low-voltage supply it carries, will always be constraining factors.


Many of the major Japanese manufacturers market their range of line-fed systems and components throughout the EC. Mitsubishi are one notable exception, though, and they do not supply their largely British-built Melguard II system outside the UK and Eire, though other Mitsubishi security and surveillance products are widely distributed by their European dealer networks and affiliates.


JVC's range of line-fed components is broadly the same across the EC, with many of their surveillance products from the far-East coming in to Europe via JVC Professional Products in  the UK. This includes their monochrome and colour cameras (TK-S100 and TK-890), plus the TK-U890/1003 and SW-C300 CCUs and switcher units, as well as their range of monitors, these are normally available from their subsidiaries in EC countries.


Matsushita, who market surveillance equipment in Europe under their Panasonic brand have the same general  policy of producing a common range of products, though this time distribution is controlled from their European HQ at Matsushita Deutschland which is located in Hamburg. The range includes their Mini CCVE system which operates with WV-BL90 and WV-80 cameras; the Colour CCVE system which uses the recently launched WV-CL120 camera, plus the WJ-400 and WJ-450 B&W and colour quad units. Their top-end System 200 and 300, which can handle up to 4 and 64 line-fed cameras respectively, and feature multiplexed telemetry for controlling pan/tilt heads, zoom lenses, high-speed shutters and audio are also available on an EC-wide basis. As a matter of interest Panasonic began manufacturing line-fed black and white CCTV cameras in Germany last October.


Philips are the leading European manufacturer in this sector of the surveillance market and they have two 4 and 6 camera line-fed packages,  based around the latest incarnation of their highly successful 'Observation System. This is available throughout the EC, though the general specification varies slightly from country to country, depending on local conditions.


Sony are another company who aim to keep things simple, their line fed cameras and peripherals are the same in most EC countries, though with small variations to take account of differences in mains supplies etc. Distribution is controlled from Sony Europa in Cologne. They presently have four cameras, two black and white (SSC-M350CE & SSC-M370CE), and two colour (SSCC-350P & SSCC-370P), these are compatible with four CCUs. The YSW-130P and YSW-230P are single and four camera PSUs respectively. The YSS-6P is a six camera CCU/switcher, and the YSS-104, dubbed the 'Intelligent Sequential Switcher', can drive up to 8 cameras, it has the added facility that it can be controlled from a IBM or compatible PC.


TOA's  range of  six line-fed, or 'power superimposed' cameras are available in most EC countries via local distributors, though many of their products enter the EC via the UK. Their current line-up includes four black and white models, (CC-1110, CC-1120, CC-1320 & CC-1510) and two colour cameras (CC-1150S & CC-1350). These can all be used with their CC-8350 camera control unit/switcher, which can handle up to three cameras, and the CC-8450 extension adaptor which increases the number of cameras to six. TOA also have a manually-switched four camera control unit (CC-5784) and single camera CCU (CC-8750).


Line-fed CCTV is clearly growing in importance to European installers and the technology is improving all the time but the most commonly cited objections -- compatibility and cost --  need to be addressed before they can compete effectively outside the small to medium scale system market..


Useful contacts:


JVC Professional Products, London (44-81-902 8812)



Matsushita Deutschland, Hamburg (49-40-85490)

Philips Eindhoven (31-40-788908)

Sony Europa, Cologne, (49-221-5977323)

TOA Electronics Ltd., Brentwood (44-277-233882)



 (c) R.Maybury 1993 2903



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