Articles and whitepapers

4/5/2003

The Need for Structured Wiring

By Keith Haddock and Stephen Gough

Over the years there have been enormous changes to the way we live in our homes. Not so long ago, the inside loo was a luxury, heat came from open fires, and parts of the kitchen were open to the elements to stop the butter from going rancid. Now we treat central heating as a human right, the fitted kitchen as a fundamental requirement, and all the electrical gadgets as essential for survival.

Such devices are designed to make life easier, but still require some kind of elementary programming - even the simple off/on switch calls for affirmative action. Then it is almost certain that you switch on your TV with one remote and operate the channel changer for the cable system with another. Then you hunt down the back of the sofa for the VCR or DVD remote, and so that you can watch your favourite movie, you turn down the lights and draw the curtains. A lot of effort isn't it? And it's all completely unnecessary.

Imagine if you had a central control for all the systems in your house, not just to control each component, but one that would almost intuitively maintain the living environment of heating, lighting, security and entertainment systems, and initiate intelligent interaction between them. So if you want to watch that movie, it will turn on the relevant amplifier, DVD and television, turn down the lights and draw the curtains - in any room that you choose. It is this kind of effortless 'smart' control that home owners now seek.

House wiring graphic

But 'smart homes' are not only for the rich. When you consider how many TVs and computers are dotted around the average home, how much we spend on home entertainment equipment, and how more of us are using the Internet, you realise how useful a simple network can be to the average home owner. Yet many homes lack the wiring necessary for even the most basic connections. Typically, the wiring has either been modified, bodged or is simply the product of lazy practices. The result is, literally, dead-ends.

It is surprising however, what can be achieved with a little forethought and the application of certain wiring principles. It starts by introducing what is commonly referred to as 'structured wiring.'

Certain UK developers are now offering their clients 'future-proofed' homes by accommodating communications, entertainment and security in a structured wiring regime, following a trend established in the US, a market which has seen an explosion in structured wiring sales in recent years. So let us see how adding a little structure to the wiring plan can make a huge difference at the other end.

The standard TV network comprises a ring-main of TV points, which have been daisy-chained together, usually using cheap co-axial cable (10p per metre). By the time the RF (radio frequency) signal reaches the third or fourth room (or point), picture and sound are distorted because the signal has run out of 'juice'. By adding a signal-boosting amplifier at the aerial end, and a level-balancing termination point (TAP) after the amplifier, which ensures all points are driven individually at the correct level, and by replacing the cheap coax with decent CT100 co-axial cable (50p a metre), the poorly-performing RF distribution system can be transformed into an embryonic structured wiring system with real growth potential.

Underfloor wiring

If you want to share the system in the living room, which might include a satellite box, DVD and VCR, with other rooms, you would install another length of CT100 to a splitter-box before the amplifier. At the equipment end of this 'return' cable is an RF modulator, which allows the installer to pick specific VHF frequencies to carry audio and video. Plug your gear into the modulator and there you have it: video and audio from your sources (DVD, video, satellite etc), available through all screens on your network.

Alternatively, a simple RF distribution system can be achieved using a 'smart-switch' (or multi-switch), from which TV/SAT/FM signals are sent to dedicated 'tri-plexed' room outlet sockets down a single CT100 cable. You can plug gear such as a SAT receiver into every room, and share what you are watching with other rooms through a return cable back to the smart switch.

The key technique in all structured wiring schemes is the use of the return cable, through which all sources are referred back to a central point in the network for distribution. This is known as the 'home run' principle and is found in every structured wiring plan. Another standard practice, and a by-product of the home run principle, is to collect all the sources and the smart distribution devices in one place in the home, often called the MEC (Main Equipment Centre). This can be the living room, or in more elaborate systems, a dedicated room for storing racks of equipment.

Backstage racking

Another structured wiring scheme uses a specialised multi-room controller in the MEC and distributes stereo sound. The hi-fi, and other stereo sources plug into the controller, and are switched on a network of loudspeaker cables and CAT 5 (Category 5) control cables using small keypads in every room.

CAT 5 is a key technology in the smart house repertoire, and is a standard that establishes the minimum requirements for telecommunications cabling. The CAT 5 cable comprises a core of eight cables, in four twisted pairs, and is designed for low noise and high speed. CAT 5 cable (and sometimes the more advanced version CAT 5e), is used in many structured wiring schemes to carry audio, video and control signals around the network. For instance, the keypads in the last example are connected back and forth from the multi-room controller using CAT 5.

CAT 5 cable

CAT 5 is a specialised cable and requires careful application if it is to operate correctly: no more than 20mm of the outer sheath should be removed, no more than 10mm of the signal-carrying core should be untwisted, sharp bends in the cable should be avoided, the cable should be kept at least 160mm away from 230V mains cable, no more than 25lbs of pull tension should be used, and you should not step-on, kink, snag or splice CAT 5 cable. It should be treated with respect because it is the main highway for signals in all advanced structured wiring schemes that regularly use three CAT 5 outlets in every room, one for broadband A/V signals and control signals, and the others for the telephone and PC networks.

The ultimate smart house systems introduce more specialised, and much more expensive, digital interfaces, routers and in-room LCUs (Local Control Units). Some routers are capable of multiplexing 32 sources in 64 rooms, converting all audio and video to digital signals alongside the digital data control signals, and converting them back to analogue at the LCUs. All audio and video sources, including those from entertainment portals such hard disk media servers and PVRs (Personal Video Recorders), as well as video from security cameras, can be sent anywhere in the home on CAT 5 cable. Lighting and heating controls are on separate structured networks under the intelligent control of dedicated, centralised hubs, usually situated in the MEC. Remote touch panels in each room talk to LCUs via infra-red (IR) and can communicate with heating and lighting systems via RS232, 485, 422 and other data languages through wall-mounted interfaces.

Installer with touch panel controller

Such systems can cost as much as £100,000, but deliver the most sophisticated smart-house utilities. They give the client control over all services anywhere in the home via very cute, portable IR panels, and embody a high level of intuitive management.

The basis of any successful structured wiring system is good planning, and adherence to certain principles and techniques enshrined in the laws of custom installation. You can do wonders with them, transforming bog-standard home wiring into something far more useful, for as little at £500. However the more complex systems are more likely to require the expertise of a specialist.

Keith Haddock is PR officer for CEDIA UK.

www.cedia.co.uk

Stephen Gough works for CEDIA member Sensory International Limited.

Telephone 0161 924 0200
stepheng@sensoryinternational.com
www.sensoryinternational.com