WEEK 4 : DAY 4 COLOUR CODING OF WIRES

4.4 COLOUR CODING OF WIRES

4.4.1 colour coding of copper wires

        Copper wires come in 5, 10, 20, 50, 100, 500 pair of wires. So to identify such huge number of wires can be a tedious task. To facilitate it colour coding is used on wires. First of all all wires are organised in to group of five wires having following colour code

1. Blue
2. Orange
3. Green
4. Brown
5. Grey

        If the wire are five pair then the above scheme is the order of pair no of wire.The other wire will be white. If the wires are more the other wire in the pair is organised as follows

1. White
2. Red
3. Black
4. Yellow

        An example is given below. For a 20 pair PIJF wire the color coding will be like this

WIRE NO.	Color of 1st wire	Colour of 2nd wire
1	Blue	White
2	Orange	White
3	Green	White
4	Brown	White
5	Grey	White
6	Blue	Red
7	Orange	Red
8	Green	Red
9	Brown	Red
10	Grey	Red
11	Blue	Black
12	Orange	Black
13	Green	Black
14	Brown	Black
15	Grey	Black
16	Blue	Grey
17	Orange	Grey
18	Green	Grey
19	Brown	Grey
20	Grey	Grey

        If the wire are above the 20 pairs they will be like 50, 100, 500 etc. They will be coded as shown in the figure.

Colour coding of wires

        So here on the left there are group of wires an on the right there is colour in which they are grouped together.
Let us take an example to understand this. Let us assume that we have to find wire no 74 in 100 PIJF wire. Now dividing by 20 and taking integer part we get 3 i.e green colour wire. Then 74 - (3X20) we get 14. Which comes under brown-black pair of wire.

4.4.2 Colour coding of Optical Fibre Cables

        24 - fibre OFCs is used in the railways. They are divided into 6-tubes having four fibres each. 

• 4 Fibres in each tube are coloured. The colours are:-

1. Blue
2. Orange
3. Green
4. Colourless

• Now the rest of the six tubes are arranged in a circular fashion.Two of them are blue and orange and rest 4 are colourless. We have to count from blue and proceed in the direction of orange.

.4.4.3 Practical application of colour coding

        The person there gave a very interesting example of a practical application of colour coding. In offices there are phones that connect one department to another. Of course copper cables will be used because there is no point of using a optical fibre cable there. So usually 100 wire copper cable is used. Now let us assume there is a office in which many different departments are there as shown in the figure. Also there is a telephone code to each department that is assigned according to the wire number that office is using. E.g :- 32 code number means 32nd wire.

        Let us assume that the wire is cut due to some reasons. Now you have to join it. You will obviously take some time to join each of 100 wires. Now here GM office (code :- 39), DRM office (code :- 44) and HR office(code :- 65) is given preference as they have administrative work. So you will connect 39th,44th,65th wire first so they get connectivity. Hence you must know which wire is which. This is where colour coding knowledge is required.

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