16th Edition (reference only) – NOW superseded by the 17th Edition IEE Regulations.
 chapter 1 The IEE Regulations chapter 2 Installation Requirements and Characteristics chapter 3 Installation Control and Protection chapter 4 Cables, Conduits and Trunking chapter 5 Earthing chapter 6 Circuits chapter 7 Special Installations chapter 8 Testing and Inspection chapter 9 Data cabling and Networks
 Data cabling and networks
 9.1 - What is data cabling and why do ------- we need it? 9.4 - System design and categories 9.2 - What are digital systems? 9.5 - Installing data cabling 9.3 - Copper or glass fibre? 9.6 - Useful information

9.2 - What are digital systems?

Data networks are already digital and telephones are fast becoming so. That means that the signals carried are not waves (like sine waves) which are subject to deterioration as they are fed through cables, but consist of a series of pulses. If a distorted wave is received, it is usually impossible to reshape it to the form it had when transmitted because we have no information to tell us what that shape was originally. If a digital pulse becomes distorted, it can be reshaped, because we know that it was rectangular. Information sent digitally is encoded using the binary system, which has only two numbers, 1 and 0. The rectangular pulse represents 1 and the absence of a pulse at the expected time is a 0. Some of the low value binary equivalents of decimal numbers are shown in Table 9.1

A lot more numbers are required in the binary system than in the decimal, and vast numbers of binary digits will be required to represent a complex wave-shape, such as that generated by the microphone in a telephone. Modern electronics is quite able to handle these large numbers of digits, so most means of communication are becoming digital.

 Table 9.1 - Some decimal numbers and their binary equivalents Decimal Binary Decimal Binary Decimal Binary Decimal Binary 1 00001 9 01001 17 10001 25 11001 2 00010 10 01010 18 10010 26 11010 3 00011 11 01011 19 10011 27 11011 4 00100 12 01100 20 10100 28 11100 5 00101 13 01101 21 10101 29 11101 6 00110 14 01110 22 10110 30 11110 7 00111 15 01111 23 10111 31 11111 8 01000 16 10000 24 11000 32 100000

The increasing introduction of cabling systems with higher bandwidths are allowing digital systems to become faster and their use is becoming commonplace. Wireless systems, using radio waves in place of cables are being developed; but such systems, of course, require little or no data cabling.