to the 16th Edition IEE Regulations
   
   
   
 
 

chapter 5
Earthing

chapter 6
Circuits

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.

 

 

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Extracted from The Electricians Guide Fifth Edition
by John Whitfield
Published by EPA Press Click Here to order your Copy

Click here for list of abbreviations