TELEPHONE CABLE.

Press, Volume LXII, Issue 18636, 10 March 1926, Page 5

TELEPHONE CABLE.

TO SPAN COOK STRAIT. The new telephonic cable that is to span took Strait arrived in Wellington horn England by the Tongariro, and was, transferred to the foretank of the Tutanekai. The actual work of laying the cable will not be proceeded with at once, as the Government steamer is undergoing an extensive overhaul, and it may be over a fortnight before she is in a condition to put to sea. The new cable is to be laid between Lyall Bay at the Wellington end, and Blind River (near Seddon) in Marluorough on tho other side of the Strait. Ao it will necessary to connect it up j with stations at either end there will be a good deal of land work involved in the burying of it between Lyall Bay and Courtenay Place, whence it will bo conducted in exisiting ducts to the Stout street Central Exchange, and the live mile from the beach at Blind River to the new station to be built for its reception at Seddon township. Siemann's, who made the new cable, are also supplying the machinery for the repeat station at Seddon. In long distance telephony the sound has to be amplified at certain points, and relaid, precisely in the manner that wireless signals are amplified, by the use of valves, etc. This requires the erection of a room about loft by 18ft at Seddon to contain the repeating apparatus, and switch board that has not yet arrived in the country. This will be adequate to serve Nelson, Marlborough and Canterbury. Whether another repeating station will be needed further south remains to be seen by the experience of the one now to be erected at Seddon. The marvel of the four-core continu-ous-loading cable is that three conversations (engaging six persons) and three Morse messages, may be sent over the cable at one and the same time, without the slightest risk of interference one with the other, and yet the cable is only a two-pair one; that is to 6av, there are only four copper wires running through "the heart of the cable. The new cable is not of uniform thickness throughout its entire length from station to station. The deep sea length is one and threequarter inches in diameter, and the shore ends are two inches in diameter, whilst the armouring is proportionately heavier in the shore ends than the deep-sea portions of the cable, for the reason that extra strength is required in the cable as it reaches the shore, owing to the greater action of tides nncl.surf Round the central core containing the all-impor-tant copper wires, there are seventeen especially prepared iron wires, whilst on the shore-end portions there are only twelve, but the latter are considerably stouter. The composition of the cable, which is unique in these parts, consists of the four copper wires, each contained in the centre of four circular compartments made by a running tube of the finest brass tape, which makes the cable invulnerable to the attack of the torpedo, the copper wires being encased in belata (a form of gutta percha) within the brass tape circles. Even inside the belata filling bound close to the copper wires is the finest of iron wire—threadlike in character—which gives the continuous loading required. The brass tape ducts are geometrically placed in the centre of the cable, and round them is the usual jute "worming; then the stout iron wire Jkrmouring, which in turn is protected with jute yarn and a bituminous compound. Taking into consideration all the work that has to be done in connexion with the cable afloat and ashore, it is not exnected that the new cable will be available for every-day' use- for at least a month yet.