Structured wiring - what can it do?

[Module last updated Oct 1995]

Many data services have been designed, or can be adapted, to run over unshielded twisted pair wiring. For example,

and many others.

If you have a non-standard data wiring requirement, please do not hesitate to ask. Use of the structured wiring saves a lot of unnecessary effort in installing non-standard individual cables, and gives much greater flexibility vis a vis moving equipment from room to room etc. However, use for conveying power currents is unacceptable; and use of data cables in our environment for telephone lines is also not envisaged.

It is also possible, using proprietary "baluns", to connect 10-base-2 (i.e thin-wire 50-ohm Ethernet) over twisted pair wiring. We have done this in a small number of cases, where workstations had come equipped for 10-base-2 Ethernet only, and an upgrade to twisted pair would have been prohibitively expensive. At that time, a pair of baluns cost us about £75, at a time when the cheapest coax-to-TP "convertor" cost over £150 and a proper coax-to-TP repeater would have cost £300 or more. I would not recommend it as a general solution, and I would recommend using this only on an individual basis and not attempting to daisy-chain it to any other 10-base-2 co-axial segment. With coax-to-TP full repeaters now available for little more than £100, this proprietary solution will soon be hardly worth attempting.

Our wiring will be technically capable of supporting the 100Mb/s standards that are currently evolving. There are several contenders: twisted-pair versions of the FDDI standard, some 100Mb/s versions of Ethernet, and a relatively new scheme that is rapidly gaining ground, called ATM (Asynchronous Transfer Mode). We had not yet seen a requirement for general deployment of any such standard in our environment, and it is unclear which one will become the best choice in the long term.

BT informed us at the time of the installation that although the wiring (category 5) is adequate for 100Mb/s, the connectors available at that time were either unsuitable or prohibitively expensive. They gave us to understand that before deploying 100Mb/s connections at some point in the future, we would need to have a newer type of connectors fitted. This has not been investigated in detail, due to the lack of motivation at this time. Sceptics from the computing service have also suggested to us that as our representatives failed to insist on time domain reflectometer tests of our wiring, there is no guarantee that it has been installed correctly, and it might fail to support these higher data rates. However, BT told us, informally, that insisting on full TDR tests would have more or less doubled the cost of the contract, and it was their view (which we accepted, well, in fact in view of the limited budget we had little choice in the matter) that their installers already used good practice methods of installation, such that the TDR tests would be a waste of time and money. So far, I am unable to throw any further light on these questions for you.