| Wire Number | Base Colour | Ring Colour | Function |
|---|---|---|---|
| 1 | Green | White | (Not used in domestic installations.) |
| 2 | Blue | White | ‘B’ wire |
| 3 | Orange | White | Ring wire |
| 4 | White | Orange | Earth wire (in a PABX) |
| 5 | White | Blue | ‘A’ wire |
| 6 | White | Green | (Not used in domestic installations.) |