£2,000,000 TELEPHONE CABLE

Hokitika Guardian, 6 January 1930, Page 8

£2,000,000 TELEPHONE CABLE

SECRET TALKS TO U.S. /By Sir Robert Done Id in “Daily Mail.”) An invention is being perfected which will enable a business man in London to hold a conversation, direct and secret, with a man in New York, through his ordinary desk telephone. This is the latest triumph of the science of dielectrics: the transmission of the human voice over thousands of miles of submarine cable. Up to now the maximum distance which tlie telephone carries with certainty under the sea is less than 200 miles. It was this failure to get a submarine cable to transmit the spoken word as effectively as it does the Morse code signals which gave wireless telephony its opportunity in long-distance ocean communication. Tlie introduction of the loaded cables two years ago, by which the speed of transmission was multiplied tenfold, gave cables a new lease of life, and within a, few years they will couple the telephones with their long-distance cable channels. This revolution is due to the work of scientists and experts in laboratories in London and New York, experimenting quite independently of each other. The credit in America belongs to the research department of American Telephone and Telegraphy Company—the Bell combination. In London the invention has been developed in the laboratories of the International Standard Electric Corporation. The two corporations are working on parallel but competitive lines. Tlie only ocean telephones planned between New York and London is that belonging to the Bell company.

AS QUICK AS TRUNK CALL. The telephone cable is a development of the loaded permalloy cable. The cable will be loaded with a series of alloys which combined are given the name of “perminvar.” meaning that its permeability is not variable. It is insulated, not with guttapercha, but with a new dielectric material called “ pargutta” 1 . While intended as a medium of com 7 munication under the sea, the new cable will stick as long as possible to the land It will go from New York by way of Nova Scotia to Newfoundland. From Newfoundland it will jump 1,800 miles to a small place called French Port, in Mayo. It will then be carried through Northern Ireland, across the shortest sea route to Stranraer, and on to Glasgow, where it will link up with the main trunk line to London.

This sounds as if it were a long-time journey, but the system will work as quickly as the ordinary trunk telephone* The relays are automatic. Tlie secret of success is due-to counteracting fading. In the ordinary trunk land line the voice has to be amplified at repeater station every 50 miles. The perminvar cable will preserve the sounds over a distance of 1,800 miles but it will be a very still small voice which reaches Ireland. The cable will be shielded for a hundred miles from the shore to safeguard it against land disturbances and then will be picked up and amplified by the repeater station.

It is almost impossible to express arithmetically the variations between the input and output power; before it completes the distance the sound will be faint almost to vanishing point—a fading away equivalent to one thousand million-millionth part of the transmitted power. Yet such is the extreme delicacy and perfection to which repeaters are carried that the faint attenuated tones will at once be restored to natural speech, just as spoken at the other end. The scientists and experts in New York have carried experiments to such a stage that they are satisfied that they have solved the problem of long-distance ocean telephony. Tlie engineers of the British office are equally satisfied that a solution has been found and are co-op-erating with their opposites on the other side of the Atlantic in putting the new system in operation. Tlie cable will take two years to complete and will cost £2,000,000.

SPAIN TO SOUTH AMERICA. The invention evolved by the experts of the International Standard Electric Corporation, one of the subsidiaries belonging to the world communication and construction groups, built up in nine years by the organising genius of ColBeh n, is not quite so far advanced as is its Bell ocntemporary. It is on the some lines, although it is hoped to introduce more channels in the same cable. Arrangements have been made to lay down in European waters a 200mile cable for final tests.

Tlie line first planned by this eompan y will run from North to South America where the Helm interests dominate the world of communications. It will be laid in stages of several hundred miles by sea. 'Hie next line proposed will go from South America to Spain and Portugal, and in no case will the unintedrupted span he more than 1,800 miles in length. According to Sir Thomas Purves the engineer-in-chief of the Post Office, this year’s president of the Institution of Electrical Engineers, the new system will be a welcome supplement to the radio-telephone. The Transatlantic telephone is increasing in popularity and efficiency—the one because of the other —but it cannot yet overcome magnetic storms and fading due to unknown factors of atmospherics. There are delays and about 20 per cent, of the calls cause difficulty—at best they are only fair. .

In spite of devices which are being tried, it is impossible to make wireless telephony secret. Messages can be tapped by anyone who takes a lot of trouble, and they have to be relayed more than once between the sender and the receiver.

The cable telephone provides the same measure of secrecy* as does the ordinary telephone. Sir Thomas Purves, who referred to the subject in his address as president of the Institution of Eleetrica* Engineers, welcomes the invention for another reason: it will supplement the radio-telephone and relieve congestion in the ether. It will have a stabilising influence, and he foresees the future of the radio-telephone when the cable-tele-phone becomes general for point-to-point service, the radio-telephone being used more for communication from moving objects, trains, ships, and aircraft.