NEW RADAR ’PHONE TEST SOON

Gisborne Herald, Volume LXXV, Issue 22657, 7 June 1948, Page 5

NEW RADAR ’PHONE TEST SOON

MELBOURNE, May 13. The Postmaster-General’s Department will try a new radar technique —pulse modulation radio-telephone * transmission—to relieve the load on trunk lines in Victoria, N.S.W. and Queensland. Each pulse modulation radio-tele-phone system installed will be able to carry up to 24 conversations at one time, compared with a maximum of four on each radio-telephone channel between Victoria and Tasmania. The Postmaster-General, Senator Cameron, said that the method appeared to offer a solution to the department’s problem of extending the underground cable and open wire trunk telephone network. Systems giving up to 100 conversations a channel were being developed in America. How It Works The pulse modulation method was similar to the motion picture technique, in which a series of still pictures flashed on to the screen in rapid succession to give the impression of continuous motion. The pulse modulation system transmitted speech in the form of electric pulses. Twenty-four pulses and a synchronising pulse were transmitted in a sequence, which was repeated 8000 times a second. Receiving stations had to be within line of sight of transmitting stations. Senator Cameron added that the power used m transmission was very low and the cost for power was not great. Engineers were making detailed surveys to determine suitable locations for the relay stations.