12 THE BELL SYSTEM TECHXICAL JOIKN'AL, JANUARY 1957 



Experience in these two organizations has been quite different, but each 



ill its own way has been im-aKiable in achieving today's system. 



British Experience 



In Great Britain, communication to the Continent dominated the 

 early work in submarine telephony and led to systems providing rela- 

 tively large numbers of circuits over short cables laid in shallow water. 

 Early systems were un-repeatered, but the ad\'antages of submerged 

 repeaters were apparent. Experimental work, started in 1938, culminated 

 in the first submerged repeater installation in an Anglesey-Isle of ]\Ian 

 cable in 1943. Currently, there are many repeaters in the various shallow 

 water cables radiating from the British Isles. 



These repeaters, although of a size and mechanical structure well 

 suited to shallow water applications, are not structurally suited to 

 Atlantic depths. In 1948, the Post Office began to study deep water 

 problems, and the first laying tests of a deep-water repeater housing were 

 conducted in the Bay of Biscay in 1951. This housing was rigid, like the 

 shallow-water ones, but smaller and double-ended so that the repeater 

 was in line with the cable. Thus the rotation of the repeater, which 

 accompanies the twisting and untwisting of the cable as tension is in- 

 creased and decreased during the laying operation could be tolerated. 

 The housing now used by the British Post Office is basically the same as 

 this early deep-water design, although minor modifications have been 

 made to improve the closure and water seals. 



A serious study of transatlantic telephony was begun by the Post 

 Office in 1950 when a committee was set up to report on future possibili- 

 ties of repeatered cables. As a result, it was decided in 1952 to engineer 

 a new telephone cable to Scandinavia, 300 nautical-miles in length, as a 

 deep-water prototype, even though the requirements of depth, length, 

 and channel capacity all could have been met by existing shallow-water 

 designs. 



All of the Post Office submarine systems are alike in that they use but 

 a single cable, the go and return paths being carried by different frequency 

 bands. The adoption of this plan was greatly influenced by the conditions 

 under which the art developed. Because North Sea and Channel cables 

 were highl}^ subject to damage from fishing operations, it was desirable to 

 limit the effects of such damage as much as possible. A single cable 

 system is obviously preferable under these circumstances to a system 

 using separate go and return cables which could be put out of service by 

 damage to either cable. Since these systems were designed for shallow 



