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The New Zealand Railways Magazine, Volume 6, Issue 2 (June 1, 1931)

The Subscriber's Instrument

The Subscriber's Instrument.

One very important item of telephone plant, namely, the subscriber's instrument, has, however, not benefited by these developments. The reason is to be sought mainly in the policy adopted by some of the largest telephone administrations, which until recently found it inconvenient to admit a new type of instrument, just as, years ago, they found it inconvenient to admit the automatic system. As a result of the public demand, however, this reluctance has now been broken down. The telephone is no longer regarded by the subscriber as an electrical contrivance entitled to some respect and entailing a certain amount of inconvenience in its installation and use. Encouraged by the rapid and efficient service given by the automatic exchange, he looks upon the telephone nowadays as a necessary and welcome accessory and expects it to be as serviceable and as handy as his fountain pen! He is impatient of technical difficulties, and where technical difficulties interfere with his convenience, he insists that they must be overcome. Coincident with the growth of this feeling has been the expansion of telephone networks to a stage at which difficulties are being experienced in finding space under our streets for the enormous numbers of conductors now required. Means of overcoming the difficulty by the substitution of conductors of lighter gauge have been sought, but the extent to which this remedy is effective is limited by consideration of the transmission efficiency of existing instruments. Another feature of recent development has been the technical perfection attained on long-distance net-works, national and international. Attenuation and distortion are practically eliminated. A modern long-distance circuit, regardless of its length, transmits all frequencies between 300 cycles per sec. and 2,000 cycles per sec. with a practically uniform attenuation of about ten decibels. (The word “decibel” is now internationally adopted as the name for the “transmission unit.” Broadly speaking a decibel, a standard mile and a decineper are all equal.) Proposals are now being discussed to extend the frequency range for uniform transmission upwards to 2,400 cycles per sec. This achievement has been the result of the application of detailed scientific study to the problems of page 63 main line transmission and is far in advance of the performance of subscribers’ telephone instruments of the types in use hitherto.

Summarising the circumstances outlined above, we may say that the insistent desire of the subscriber for a more convenient type of instrument, the technical progress made in other branches of the telephone art, and the scientific knowledge and methods of study and manufacture which recent years have made available, have all combined to demand and to make possible the production of a new and greatly improved type of telephone instrument.

On account of the intimate association of the subscriber's instrument with the public, it is very desirable that the type adopted should be permanent for as long a period as possible. To secure this degree of permanency, it is not enough that the new type should meet the demands of the present state of the art. It should represent such an advance that it will fulfil future requirements so as to defer as long as possible the time when progress in other branches of the art necessitates another change.

It is with the confident belief that such an advance has been made that the “Neophone,” the new telephone, has been introduced.

The British Post Office, recognising that the time had arrived for the introduction of a new type, investigated and tested several types recently introduced, but without finding one complying fully with its requirements. It therefore associated itself actively with Siemens Brothers and Co. Ltd. during the later stages of the development of their instrument, so that, in those details which most nearly concern the administration and the subscribers, the company had the cooperation of the Post Office engineers. It has also assisted by conducting confirmatory life and other tests in its own laboratories.

Following upon these investigations, orders for over 200,000 Neophones for the British Post Office have been placed with the Company.

(To be concluded.)