9.1 - What is data cabling and why do we need it?

First of all, why should a book concerned with the Wiring Regulations seek to cover the subject of data cabling, to which the Regulations (BS 7671) do not apply? The simple answer must be that most of today’s electricians are almost certain to be concerned with the technology sooner or later, and an introduction to the subject will be useful.

Data cabling (often referred to as a network) has become extremely common in business and in academic installations, and will shortly almost certainly be a necessity for many domestic applications. Data terminals and computers these days are seldom separate ”stand alone“ items, but are networked together, so that all can communicate with the others and so that the data input to them may be collected and analysed centrally. For example, all the tills in a supermarket must be linked so that any price changes can be relayed to all of them simultaneously, and so that the sales information they obtain from the bar code readers can be gathered centrally to provide exact data concerning the merchandise checked out. Again, all the individual computers in a college will be linked by a network so that all can use a single set of programs, such as for word processing.

The system to interconnect these systems is the data cabling which forms the network. In its most basic form it will consist of copper cables which exist in pairs, which are twisted throughout their length as an aid in combating the problem of interference due to ”electrical noise“ from other electrical wiring and equipment. One method of ensuring that there will be no interference is to send the signals in the form of light. A glass fibre cable is used as path for light pulses injected at one end by a laser and read at the other end by a photocell. Both of these methods will be considered here. However, it must be appreciated that one chapter like this one can only provide the briefest coverage, and that a specialist work, or a training course, is necessary to obtain a fuller understanding of the subject.