TRANSATLANTIC TELEPHONE CABLE — AFFEL 279 



is felt about their continued success, although the previous experiences 

 have been for shorter distances. In the case of the deep-sea section, 

 the same technique was employed in 1950 for cables between Key West 

 and Havana, some 120 nautical miles long, having three repeaters in 

 each direction. This system has operated over 5 years with no notice- 

 able deterioration. 



The whole project has required great attention to detail and great 

 precision in design and manufacture. Very small differences in the 

 cable and in the amplifier performance would, if allowed to accumu- 

 late, have serious over-all results. At least 20 years' life has been the 

 objective in designing the elements making up the cable system. 



It is possible, of course, that in time certain parts of the cable or 

 repeaters may become faulty and will have to be removed. This is 

 done by grappling and raising them to the surface from a cable 

 ship. Unfortunately, each time this is done in deep-sea section it is 

 necessary to splice in a longer piece of cable than already existed. 

 This is because, when the cable is first laid, it follows the bottom closely 

 and, since it has very little stretch, it is almost impossible to pick it 

 up by grappling in the deepest sea portions without first cutting it at 

 the bottom. The two ends are then brought up separately and repairs 

 are made. A new section of cable, perhaps as long as 5 or 10 miles, 

 must then be spliced in to close the gap. 



What follows gives more details of the new project and, as noted, 

 is largely taken from the paper "A Transatlantic Telephone Cable," 

 by Mervin J. Kelly, Sir W. Gordon Kadley, G. W. Gilman, and R. J. 

 Halsey, published in Electrical Engineering, vol. 74, No. 3, 1955 

 (see footnote 1, p. 273). That paper goes into more detail in his- 

 torical and other aspects of the project. It should be referred to for 

 a still more complete appreciation of the numerous teclinical prob- 

 lems that had to be solved to obtain assurance that a project 

 representing an outlay of as many millions could be relied on without 

 unreasonable maintenance. 



BACKGROUND OF AMERICAN EXPERIENCE 



As noted previously, when the proposal for a transatlantic telephone 

 cable was first considered, electronic techniques were becoming estab- 

 lished in land-cable practice, although they had not reached the point 

 where serious proposals could be made to lay a submarine cable with 

 submerged repeaters on the ocean bottom. To permit this, further 

 improvements in technology were required, notably the use of ampli- 

 fiers whose performance could be stabilized by features such as nega- 

 tive feedback and long-life vacuum tubes. 



Negative feedback is a modification of an amplifier circuit which 

 greatly improves its stability with time and power fluctuations. It 

 tends to insure that the amplified currents are an exact replica of those 



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