TELEPHONE CABLE.

Otago Witness, Issue 3757, 16 March 1926, Page 7

TELEPHONE CABLE.

TO SPAN COOK STRAIT. The new telephonic cable that is to span Cook Strait arrived in Wellington from Eng- i land last week by the Tongariro (reports the Dominion), end will be transferred to the foretank of the Tutanekai forthwith. The actual work of laying the cable will net bo proceeded with at once, as the Government steamer is undergoing an extensive overhaul, and it may be over a fortnight berore she is in a condition to put to sea, but that will not delay the transhipment of the 70 miles of cable into her hold. The new cable is to be laid between Lyail Bay at this end and blind River (near Seddon) in Marlborough, on the other side of the Strait. As it will be necessary to connect it up with stations at either end there will be a good deal of land work involved m the burying of it between Lyail Bay and 1 Courtenay Place, whence it will be conducted j in existing ducts to the Stout Street Central exchange, and the five miles from the beach at Blind River to the new station to be buiit j 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 tele- j phony the sound has to be amplified at cer- { tain points and relaid, precisely in the man- i ner that wireless signals are amplified, by \ the use of valves, etc. This requires the ( erection of a room about 15ft 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, j Whether another repeating station will be v needed further south remains to be seen by j the experience of the one now to be erected at Seddon. The marvel of this four-core continuous- ' loading cable is that three conversations lengaging six persons) and three Morse mes- . sages, 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 lo say, there are only four copper wires running through the heart of the cable. The new cable, a section of which was submitted to a Dominion reporter for inspection by the acting-chief telegraph engineer, is not of uniform thickness throughout its ' entire length from station to station. The deep sea length Is one and three-quarter inches in diameter, whilst the shore ends , are two Inches in diameter, and the ' armouring 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 and surf. Round the central core containing the all-important copper wires, there are 17 especially prepared iron wires, whilst on the shore-end portions there are only 12, 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 ihe torpedo, the copper wires being encased in belata (a form of gutta percha) within tho brass tape circles. Even inside the belata filling bound close to the copper wires is the finest of Iron wire—thread-like 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 armouring, which in turn Is protected with Jute yarn and a bituminous compound. Taking into consideration all the work that has to be done in connection with the cable afloat and ashore, it Is not expected that the new cable will be available for. every-day use for at least a month yet.