Polyethylene Insulated underground PCM Cables for 2mb/s Digital Systems

Conductor - Each conductor consists of a round wire of annealed high conductivity copper.

Insulation -Each conductor is insulated with polyethylene insulation.

Twinning - Two insulated conductors are twisted with uniform lay to form a pair. The length of the lay of the pairs is so chosen that the cross-talk is minimum.

Unit - 5, 10 or 20 No's of twisted pairs are laid up to form a group which constitutes a unit. Each unit has an open helical lapping of coloured tape for identification.

Stranding - 2 units of 5 pair each for 10+2 pair cable, 2 units of 10 pair each for 20+4 pair cable, 4 units of 12 pair each for 48+6 pair cable and 8 units of 12 pair each for 96+8 pair cable shall form the respective cable.

Spare Pair - Extra pairs are provided for the purpose of supervisory and order wire circuits.

Filling & Core Seperator Tape (Screen) - The cable is fully filled with water resistant compound which is compatible with the polythene insulation of the conductors. An aluminum polylaminated tape is applied to physically separate the core into two compartments.

Core Wrapping and Screening - The filled cable core is wrapped with at least one helical or longitudinal plastic tape. Thereafter one aluminium tape, coated with polythene on both sides is applied longitudinally over the cable core with a specified overlap.

Armouring - If the cable is required to be armoured, two helical lapping of polythene bedding tape is applied over the polythene sheath. The cable is then armoured with two applications of galvanized steel tape each applied helically with a specified gap. The second tape covers the gap left by the first tape.

Jacketing - The armoured cable is finally jacketed with black polythene compound grade 03C of BS:6234