In The Loop – The Rise of Structured Cabling

You can tell an awful lot about any technology by simply looking to see how it plugs in. It is often the physical interconnection between formerly disparate technologies which provides the clearest illustration of the extent to which they have become unified. Take a look around the back of your PC, and you’ll see what I mean: Sound card inputs and outputs, perhaps a video output from the built-in DVD player, network connections and, more often than not, a telephone socket. The functions of entertainment device, communication centre and workstation now happy co-exist together on the PC desktop. But is it really the PC which has become unified, or the infrastructure behind it? The AV-IT convergence issue is essentially a debate over which technology will eventually dominate the underlying infrastructure. Have AV and IT reached an uneasy truce, or is a totally unified infrastructure inevitable?

Technology convergence is not a new issue: The unification of data communications and telecommunications was no less traumatic in its day than today’s convergence of AV-IT. In the early years of LAN, data and voice communication operated via completely different transmission systems. Up until the early ‘80’s coaxial cable was the preferred LAN medium, while voice communication was predominantly based on traditional unshielded telephone cable, known today as Cat1. Cat1 derived from the earliest days of telephony and while it could be used for modem data communication, it was inadequate for use with the emerging LAN technologies. But this physical limitation there was also another, more subtle reason behind the segregation of technologies: The computer industry and the telecommunications industries were two very separate entities at the time, as John Laban, Technical Director of network specialists Annor Ltd. recalls. “A key reason why the datacommunications department wanted their cabling separate from the telecommunications department was job preservation. Each department saw the other as a threat if an integrated voice and data structured wiring solution was implemented”…..sound familiar?.

But by the mid 1980’s, things were beginning to change: The ready availability of cheap, unshielded twisted pair (UTP) capable of handling higher data rates meant that for reasons of economy and ease of handling ,  UTP was fast supplanting coaxial as the medium of choice for data communications.  With the advent of Cat3 cable, UTP became capable of supporting 10 Mbit/sec Ethernet and 4 Mbit/sec token ring networks and so became the standard wiring spec for both data and voice. Datacommunications and telecommunications had in effect become unified by a single infrastructure technology. UTP continued to evolve as a comparatively cheap and effective signal transport until, by the early 1990’s Cat5 had become virtually ubiquitous in voice and data applications. The first commercial building cabling standard to define the structured cabling concept was released in 1991 under auspices of the Telecommunications Industry Association/ Electronic Industries Association (TIA/EIA). The original TIA/EIA 568 standard  forms the basis of the latest international standard, ISO/IEC 11801.  As well as defining in detail the media and topology of the structured cabling system, one of the primary aims of TIA/EIA 568 was to develop a uniform wiring scheme which supported multi-vendor products and environments.  In effect, this meant that it was now possible to plan and install communications wiring in buildings without any prior knowledge of the products that would eventually use it.  Although not originally conceived with AVL in mind, it is this application-independent aspect which holds the greatest significance for AVL installers. 

TIA/EIA 568 and its international derivative ISO/IEC 11801 provide strict performance criteria which any structured wiring scheme must adhere to – criteria which are well understood by building contractors like CCI Ltd who specialise in structured cabling systems. “More end users are coming around to the idea of flood-wiring Cat5 because it’s cheaper in the long-term”, says CCI’s Ian Blackman. Economies of scale make it cost effective to use a single specialist contractor like CCI, to install everything.  “Labour is by far the biggest element in the cost”, agrees Ian.  “In a new build, you might be paying €55 – €85 per outlet. This rises to something like four times that for a retro-fit.” Low unit cost and long-term savings makes the case for flood-wiring an economic no-brainer for new build’s and major refurbishments, but are AVL manufacturers being forced into adopting UTP by budget conscious architects and designers? Not always. In fact, in some cases, quite the reverse is true:

“We’ve seen a steady deterioration in the quality of video over co-ax”, declares John Stephenson, managing director of Studio Systems Ltd. “Broadband distribution over coaxial requires modulation and demodulation which degrades quality. Our aim is to re-introduce quality, and Cat5 is the ideal medium for that”. John was one of the first people to became involved with developing high quality video distribution over UTP whilst working as a senior design engineer at the BBC.  After leaving the BBC, John formed Studio Systems to develop commercial UTP video applications. “We’ve been involved with Cat5  for over ten years now”, says John. “Initially we worked in banks and dealer rooms, but applications are now much more widespread, and include training facilities and even supermarkets.” John is a strong advocate of the advantages of video distribution over twisted pair: “The beauty of Cat5 is that it’s all there: With builders and architects now routinely flood wiring,  you have the ability to patch signals anywhere you want without having to re-wire – plus, of course, the advantage of higher quality”.  The idea of high quality analogue signal distribution over twisted pair is not new: The BBC first used twisted pair during their coverage of the Queen’s coronation in 1953. But the quality of video over UTP has advanced to the point where it is now a serious contender to coaxial: “Signal quality is getting better and better all the time”, confirms Paul de Graca of Extron. “We ran a test recently between coaxial and UTP,  running a 1280 x 1024 signal over 150m; you couldn’t tell the difference between the two”. So does this mean that Cat5 offers a truly universal AVL – IT infrastructure in the same way that Cat3 unified data and telecoms? Not quite: Because as Paul points out, for the moment at least, video  “can be distributed over Cat5, but it’s still an analogue signal”.

“And at the end of the day, Cat5 was designed for IT systems, not video”, continues Paul. “You have crosstalk  and the nature of twisted pair means the R,G and B conductors are different lengths so that you sometimes end up with image convergence problems.” Some Extron equipment has trim pots to compensate for this delay, but Extron recommends using media-grade Cat5 as a solution. “Our skew-free cable means that the signal paths are the same length. The only problem”, concedes Paul, “Is that you can’t use it for IT”. This illustrates the point that although the concept of a pre-installed universal cabling structure is an attractive one, often the reality falls some way short of the mark.

There is also a problem in bridging the knowledge gap: Cabling contractors might have the specialised skills to design and wire structured cabling systems, but they will generally employ materials and solutions designed to satisfy the requirements of the IT specification. “I heard of an example recently”, says Paul de Graca, “Of a cabling contractor using Cat5 to provide a video connection in a hospital. In theory, not a problem but the cable run passes over two x-ray departments, so by the time the video signal reaches the other end, it’s got noise on it. An AVL specialist would have run coaxial as a matter of course”. Barry Revels of Canford Audio relates a similar story: “We had a customer recently who was so horrified at the quality of the cable that the building contractor had run in, that they insisted that everything be ripped out and re-wired. Amongst our traditional customer base, there is a feeling that building contractors definitely need educating in the requirements of audio”.  From the AVL side of the fence, there is still a lot of misunderstanding about the terminology and technology surrounding twisted pair. Paul de Graca comments, “Cat5 is not a fixed wiring standard….it’s evolving. We already have Cat5e, Cat6 and Cat7 is on the way.  We’ve had customers asking ‘will your Cat5 transceivers work over Cat6” when in reality Cat6 is just another UTP cable. We’ve changed all our advertising to refer to ‘twisted pair’ rather than Cat5 to help avoid this confusion. We now talk about video/audio over UTP in our Extron school to give our people a better understanding of the subject. If they want to use it properly, they need to get educated”. 

But while video transmission over UTP remains analogue-based, audio has no such limitations. Lower bandwidth requirement allows audio signals to be transported in the digital domain – the format for which UTP was originally intended – and has allowed the use of audio networks to become firmly established.  Barry Revels of Canford Audio comments, “There has been a big increase in the use of twisted pair in audio installations: That increase has been exponential over the last two years”.  Barry agrees that products like BSS Soundweb are having a big impact on the install market, and it’s not hard to see why. Multiple channels of digital audio, and in some cases control signals too, can share a single low-cost Cat5 cable delivering self-evident advantages in terms of the cost and the ease of cabling large-scale installations like stadiums or passenger terminals. Not to mention the inherent flexibility of a structured network approach and its ability to easily adapt to different applications and configurations. The audio system installed in London’s Millennium Dome, for example, utilised around 4000 channels of audio and would have been all but impossible to achieve using conventional analogue equipment. But using BSS’s Soundweb system,  signals could be routed to and from any part of the Dome – all easily managed from a central control PC. Soundweb is just one example of a new generation of audio systems designed to utilise the network infrastructure. The Soundweb network uses its own transmission protocols and is capable of bi-directional transfer of 8 channels of 48kHz digital audio over Cat5. Klotz Digital’s Vadis system is another example of an audio distribution system based on a structured wiring infrastructure. Klotz Digital supplied and installed their Vadis system into the Bolshoi Theatre in Moscow, linking all the technical areas in the two different buildings of the theatre complex. The audio matrix handles 120 microphone feeds coming from the stage, several rehearsal areas and a recording studio together with stage directions and all the tie-lines for radio and television broadcast. DSP functions like paramentric EQ and mixing consoles are all integrated into the Klotz solution.

And yet, advanced though systems like Soundweb and Vadis are, they still do not represent the true union of AVL and IT infrastructure.  The reason is that both systems still require a dedicated network infrastructure, separate from any other transports which may be needed like Ethernet networks, for example.  But systems are now available that breach this last remaining physical barrier to true integration. CobraNet from Peak Audio is an audio network solution utilising Ethernet as it’s transport medium, allowing digital audio to share the same network as data.  Ethernet works by splitting data into discrete chunks which are routed to specific destinations via repeater hubs or intelligent switches. The key to CobraNet is its ability to route time-critical data packets like real-time audio through the network ahead of lower priority network traffic. While putting all one’s eggs in one basket might not be appropriate in every case, adopting the Ethernet medium brings some significant advantages, aside from saving money on cables and cabling costs. The industry providing cost-effective Ethernet-related hardware such as switches, hubs, WiFi radio links etc., is vast and well developed. Ethernet’s “star” wiring configuration increases system reliability and flexibility. And not least is the fact that much of the management of facilities and hardware, via AMX or Crestron for example, already takes place over Ethernet.  Ethernet also allows for the creation of “Virtual” networks or VLAN’s which allow segregation of services over the same physical connection. 

And it’s not just the noise-boys that can now leverage the power of Ethernet. Artistic License produce a range of products which allow DMX512 data to be sent over Ethernet networks using a proprietary protocal called Art-Net. “Art-Net has been around for sometime now”, says Artistic License’s Simon Hobday,  “And is supported by a good number of other manufacturers through the Art-Net Alliance organisation”. So who’s buying it? “Art-Net is used a lot in building installations as a permanent fixture”, says Simon, meaning that cabling can run and certified prior to the lighting contractor commencing work. Existing Ethernet cabling can be used for retrofit or even temporary lighting projects.  “Lighting control over wireless Ethernet is also really useful at big trade shows and the like”, continues Simon, “We’ve used it ourselves in this way to great effect. Many of the big lighting desks now have a straight Ethernet connection built in.”

Further indicative of the growing acceptance of UTP cable within the pro light and sound market that Neutrik now manufacture ruggedised RJ-45 connectors specifically for the events industry. Charlie Cook of Neutrik says that “The UK  AVL industry asked us for a pro-version of the RJ-45.  Our response is the Ethercon range.” Ethercon incorporates an RJ-45 into an XLR shell. “UTP is becoming much more widespread. Ethercon is now being used by audio and lighting manufacturers”, says Charlie, “But also by broadcasters for outside broadcast work”. Paul de Graca of Extron points out. “10 meters of Cat5 costs about the same as 3 meters of cheap coaxial. I’ve even heard of cases in the U.S. where rental companies are using Cat5 on shows and just tossing it away afterwards – it’s cheaper than transporting drums of expensive co-ax”!

It is tempting to believe that development of structured cabling schemes reached a plateau with Cat5. Certainly Cat5 was once considered future-proof. But inevitably the trend within digital networks – the real driving force – is toward higher bandwidth systems. The emergence of gigabit Ethernet calls for a higher specification network infrastructure. While some Cat5 installations will support gigabit Ethernet, the recommendation now is for Cat5e cable, which at 200MHz, is rated at twice the transmission capability of Cat5. Now, even higher specification cables are emerging. Cat6 (ISO Class E) is designed to support 200MHz and above, while the Cat7 (ISO Class F) standard will be rated at up to 600MHz.  Again it’s crucial to remember that these systems are not designed to carry analogue signals. Problems like crosstalk and interference could cause some unexpected headaches for AVL installers attempting to pass analogue signals over these systems.  Nevertheless as John Stephenson says, “There’s still a lot of life left for analogue (video) over copper. I’ve yet to see really good and affordable IP video sources, although I’m sure that it will happen.” Until such time that high-quality video over data networks becomes a practical reality, the familiar video head-end infrastructure looks to be fairly safe. “I haven’t seen a rack yet that is exclusively twisted pair” comments Paul de Graca, “And I don’t really see that happening right away”. Extron launched an 8 x 8 twisted pair matrix switch for specialist applications last year, but despite “positive” response from the industry, Paul concedes that “I’ve yet to hear a consultant saying ‘we need a twisted pair matrix’”. But network speeds are increasing year on year. Just this month, Fujitsu announced the development of a 12 port, 10 gigabit per second Ethernet switch on a single chip. It is perhaps only a matter of time before the last technical barrier to true unification is breached.

But remember those warring datacomms and telecomms managers from yesteryear? Those same prejudices still exist today and are perhaps the biggest barrier to a truly unified infrastructure. “Formerly it was only IT people who understood Cat5, and they were pretty unwilling to allow others to use their network”, says John Stephenson.  Paul de Graca concurs: “It’s been hard to sell the concept to the IT world. They have to be confident that we, the AV guys, are not going to disturb their system”. But Ian Blackman of CCI has observed that the last five years has seen a gradual migration of responsibility for data, voice, security, and more recently AV infrastructure, toward a central Facilities Manager.  Perhaps if  AV and IT cannot choose to play together nicely, the Facilities Manager will settle the internecine squabble for them in the same way that IT solved the data / telecomms debate

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