WIRELESS TELEPHONY

Evening Post, Volume XCIX, Issue 90, 16 April 1920, Page 7

WIRELESS TELEPHONY

ITS UTILISATION. IN NEW

ZEALAND

IMPRACTICABLE BETWEEN THE

ISLANDS.

The suggestion made recently by a correspondent that in view of the progress abroad in wireless telephony it would probably not be difficult to arrange for wireless telephonic communication between the North and South Islands, was brought to the notice of the Postmaster-General, the Hon. J. G. Coa-tes, by a Post representative.

The Minister said that he had been conferring with officers of the Post and Telegraph Department to bee whether, it would be possible for an experiment' in wireless telephony to be made between Wellington" and Chriatchurch, and he had a^report before him from the Chief Telegraph Engineer" (Mr. E. A. Shrimpton). "Though considerable advancement has been, made in the development of wireless .telephony," said Mr. Coates, 'lit se,ems that most of the practical work done- has been confined to communications over short distances, and to the.transmission-of only one telephone message at a time between the two wireless stations involved. Telephone communication between, the North and South, Islands of New Zealand could not be met by such means, as such a service would scon demand the simultaneous transmission of several telephone communications. Reports show that there are, however, other developments of wireless telephony which give promise of meeting the problem mentioned. One of these developments is .known as multiplex telephony. It involves one ordinary wire telephone' circuit over which, by the use of wireless apparatus, and the application of •wireless principles, several simultaneous telephone conversations may be carried ■6n. The second development may be called multiplex wireless telephony. It achieves the same results' without the use of wires. Like multiplex telephony, it ■ has been given practical tests, but cannot yet be said- to be a practical proposition. It is the result of a special application of wireless receiving valves used with what are known as heterodyne circuits. By utilising the-effects of resonance and periodic interference, the receiving station is able ingeniously to discriminate between electric waves of varyinsr frequency, each carrying, superimposed upon it, the delicate modulations which constitute sound waves. These developments cannot be introduced into practical telephony until much greater reliability, freedom from changes in adjustment, and variations iii volume are assured. Unfortunately,, this stage ■has not yet been reached; arid, for these reasons, tho field of wireless telegraphy and telephony is largely confined to telegraph communication between isolated points for the connection of which wireless' is peculiarly suited."