Post Office Part In Cable Project

Press, Volume CI, Issue 29869, 9 July 1962, Page 9

Post Office Part In Cable Project

One of the largest New Zealand jobs from a physical angle was the laying of the cable from Muriwai Beach to the Terminal Repeater Station at I akapuna, and from this station to I'akapuna Beach on the future route to Suva.

In open country the cable is placed in a deep trench to avoid damage by bulldozers. In built-up areas the cable is placed in ducts.

The Post Office employed nine contractors for six months on ducting and. in all, they laid 500.000 feet, a total greater than the average annual amount for the whole of New Zealand. Pulling the cable through the ducts has made use of an interesting idea developed in New Zealand from a suggestion made by the wife of a Post Office staff member. A small piece of canvas shaped like a parachute is placed in the duct with a light cord attached, and blown through the duct by air pressure.

The cable is then pulled through and, with the COMPAC cable, this is done by hand rather than by machine because, although the cable is not fragile, it must be treated with respect.

When it is pulled through by hand, any unusual tension is immediately noticed and the trouble rectified. There would be a constant danger with a machine that tension would not be noticed and the cable might be subjected to undesirable strain.

Included in New Zealand’s tasks was the cross-

ing of an arm of the Auckland harbour from Hobsonville to Birkdale. The cable for this crossing was brought to New Zealand by the '“Retriever,” but the laying was undertaken by the New Zealand Post Office with the assistance of the “Jane Gifford” and a team of Post Office men including two Post Office skindivers who used compressed air drills to gouge out a channel in which to lay the cable where it would be safe from interference by anchors and fishing gear.

The “Jane Gifford” used somewhat unusual though practical techniques. Just before high tide she went as close as possible to the Birkdale shore and floated one end of the cable on the beach. She then moved to the other shore paying out cable en route. At high tide she beached herself at Hobsonville and, as the tide receded, men unloaded the cable end and dragged it up the beach for jointing. At next high tide the “Jane Gifford” floated herself off.

The jointing techniques require brazing of high-

tensile steel wires and of the copper conductors, as well as the extrusion of polythene for insulation and sheathing. Before a joint is passed it is submitted to X-ray tests to make sure that the copper conductor is centrally placed in the polythene and that no foreign particles or air bubbles, which would reduce the insulating qualities of the polythene, have been included.

In the whole of the 8700 nautical miles of COMPAC there are 335 submerged repeaters or amplifiers every 26 nautical miles. New Zealand has the only land-based repeater. This was placed in a pit near Muriwai and is cooled by water from a nearby spring In designing and planning the terminal at Takapuna, special attention was given to the question of possible power breaks. To prevent a breakdown of service the power is fed through batteries which have sufficient capacity to carry the load for a period. Meantime a diesel generator would automatically switch on to charge the batteries.