SUBMARINE CABLES

Evening Star, Issue 18810, 8 December 1924, Page 3

SUBMARINE CABLES

I THE LATEST PATENT. ( EFFECT OF “MAGIC LAND.” Tlio world's biggest, cable ship, the Colonia, has just completed (ho laying between New York and the Azores ol 2,400 miles of a wonderful type of new submarine cable for tho Western Onion Telegraph Company, whoso president, Mr Newcomb Carlton, considers that the new cable marks an era in the history of submarine cables. Tire “ magic band wrapped round the core of tin’s cable makes it possible to send messages six times as quickly as through a cable with the same euro without the band, states tho ‘ Daily Telegraph.’ Tho cable has been manufactured and laid by the Telegraph Construction and Maintenance Company of London, which laid the original Atlantic cable. A cable message is sent in the following manner: The words forming tho message are written by the .sender, and are passed to an operator. This man has before him a machine like a typewriter. By touching the keys he punches small holes above or below a central line on a narrow strip of paper; these groups of holes represent the characters of the Morse code. Tin's strip is passed into another machine, which transmits into the cable ■Jnipulses corresponding to tho perforations. Tim operator at the distant, end receives tho signals, and by (he aid of a typewriter writes up tho message direct on to the form which is sent to the addressee.

A more technical explanation of the method of sending a cable message is as follows Signalling currents in an ordinary submarine cable reach the far end gradually, taking time to rise to their full strength, the speed of signalling being retarded by this low rise of current. In order to record the signal it is necessary to wait until the current has risen to the value required to work the receiving instruments, and the fending must be timed to allow one signal to be, recorded before the next comes in. In the case of an ordinary Atlantic cable the interval between two consecutive signals is about onetenth of a second. If the. cable is

” loaded," as in the present rase, by wrapping the conductor with a material highly permeable to magnetism, the current rises much more rapidly to the rcipiired strength. The time interval may be reduced to about onc-sixticth of a second, and the speed of signalling is proportionately increased. The enterprise of various cable companies has spread a network of cables over the sea bed of the world. Considerable improvements have occurred in methods of manufacturing the cable, in stowing the cable aboard ship, ami in laying the cable on the sea door. .Science has nut hitherto hi ought any revolutionary change as regards the composition of the ac;ual core of long telegraph cables since the Great Eastern laid the cables of 1860 and 1866. One may represent the electric current in a cable, as stalling out full of "pep" and vim, but wit bout help it would reach the distant end quite exhausted. This diminuendo result is caused by the arch enemy of the electric current—the " I.eydon jar effect." _\ cable message coming, say, from Australia to England passes through ten retransmitting points, so that the current is supplied with new impulses of vigor. On a long cable at each end is a very sensitive instrument called a " magnifier," which magnifies the incoming currents and inci eases tho working speed about one--111 i 1 (1. Oliver Heaviside, the great Eng!isl mathematician, pointed out as long ago as 1886 that the “ Leydon jar effect ” might bo overcome by tho addition of inductance. In 1892 the late Dr Sylvanus luompson, the English scientist, worked out a scheme which he patented for utilising in a practical manner Heaviside’s ideas, and later still Ur Malcolm, another Englishman, in his work on ‘ The Theory of the Submarine Telegraph and Telephone Cable.’ advocated the, " loaded ” type for long-distance submarine, telegraph cables. it is duo to Mr Newcomb Carlton, president of Hie Western Union Telegraph Company, that the investigations, conclusions, and tests of Heaviside and Malcolm are now to be tried out, for lie alone has been bold enough to order at great cost a, loaded telegraph cable based upon (heir conclusions. Credit is also due to the Western Electric Company for having produced the metal alloy of nickel and iron, " Permalloy,” which, wrapped round the conductor in the form of tape, enables the speed of signalling to he so greatly increased; and to the Telegraph Construction and Maintenance Company for manufacturing the cable, and having at great expense built and equipped with special machinery a new wing to one of their factories for the purpose. It is the combination of these three .which enables a. step to be taken which marks a new era in flie history of the submarine cable. It is of interest to recall that the Telegraph Construction and Maintenance Company manufactured for the Western Electric' Company in 1921 three submarine cables each rather more than 100 miles in length, in -which the ‘‘.loading ” material was a special form of iron wire. Ihese cables are used for telegraphic as well as telephonic purposes. The weight of the submarine cable carried on tho Colonia on the present occasion amounts to between 8,000 and 9,000 tuns.