These cables are used in communication systems as following construction:
1- Layer, for general use, including two cables for insulation in customers premises where good appearance required.
2- Unit, of 16-pairs, for use with the binary number system.
3- Unit, of 20-pair including a 1.38 mm diameter insulated earth conductor, for use with customer distribution schemes.
4- Unit, of 30-pair, for use with PCM systems
Construction:
Solid tinned annealed copper conductor, diameter 0.4, 0.5 PVC insulation
Colors for pair identification: AC CW1308 table 2
An optinal insulated 1.38 mm copper wire as earth Rip cord for jacket easy removal PVC sheath ACC: British telecom CWB08-1990