IMPROVED TELEPHONES.

Timaru Herald, Volume XIC, Issue 13397, 21 September 1907, Page 7

IMPROVED TELEPHONES.

NEW SYSTEM FOR TIMARU.

Mr A. E. Shrimpton, an ex-resident of Timaru, who is now chief electrician of the' Canterbury section of telegraphs and telephones, is at present in Timaru supervising the commencement of the installation of the new metallic circuit system of telephones. Mr Shrimpton says that the chief features of the new system are that each telephone will have two wires connecting it with the central station, and that the electric power, instead of being generated by; batteries ■at each telephone, will be derived from the burean, either by means of a small engine and dynamo or by means of a main from the. electric lighting system. At present the return wire from an instrument to the bureau is earthed and this .causes induction which enables a, person to overhear conversations not meant for him; but with the metallic circuit system there is absolute privacy between persons using the wires. Conversation will also be much more distinct than iat present, for the wires within the cables, iire insulated with paper which has a very low electro-static capacity, and a conversation over 20 or 30 miles of wire will be imuch more audible than in the case of rubbar-insulated wires. . All the wires "are. inclosed in air-tight lead tubing, and to ensure perfect working of the system the cables'are connected'at the station to ;a series of drums containing calcium cloryde. Air is then pumped through the Whole system, and the air being dried by the. calcium all dampness in the cables •is dissipated and the result is a perfecttransmitting medium. The system in Christchurch has now been working for two years and no fault whatever has been found by subscribers. In the case of a fire destroying a cable containing 200 wires, it would be much easier to replace one cable than a large number of separate wires, in fact Mr Shrimpton says ft ihat recently two cables were burned through in Glirfctehurch and were replaced almost before subscribens were aware of the i fact.

The way the system is worked is briefly this. The subscriber, on taking the receiver in his hand causes a small lamp to light opposite his number in the bureau and the operator is able to tell at a glance who is speaking. When the subscriber has been switched on to the person he wants two lamps remain alight, and, as often happens, one speaker has to leave the instrument to make an enquiry, the operator knows this withoutasking a word. Another convenience is the fact that each operator h?s control of the whole switchboard and therefore no time is lost in" connecting any two persons.

The new telephones will be somewhat different to the present ones, the microphone and receiver being practically the whole instrument.

Mr Shrimpton says it will be about 'six months before the installation is completed owing to the fact that the new wires cannot be connectad up until all the cables are in position, and if will be some time yet before the large multiple switchboard arrives.

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