TRANSATLANTIC TELEPHONE CABLE — AFFEL 281 



The repeaters required for the deep-sea system had to be designed 

 to withstand the shocks of laying and recovery and the pressure of 

 water encountered at the greatest depth on the North Atlantic route — 

 approximately 3 miles. 



There are three vacuum tubes in each repeater. These had to be de- 

 signed not only for long life but capable of operating with compara- 

 tively low power and potential to make it safe to supply power to all 

 the 50-odd repeaters from the shore ends without exceeding a safe 

 working potential. This potential, incidentally, is of the order of 

 2,000 volts direct current at each terminal. 



DEEP-SEA REPEATER CONSTRUCTION 



The desirability of a flexible type of liousing has been referred to. 

 The structure, as noted, is a flexible bulge in the cable, 10 feet long, 

 and 2.8 inches in diameter, tapering, for a distance of about 28 feet 

 at each end, down to the cable diameter. The armor of the cable it- 

 self is continued over the repeater housing but with extra armor wires 

 added to get complete coverage. To prevent the twisting of the re- 

 peater in the laying operation, there is a second layer of wdres with 

 opposite lay. 



The structure of the repeater container is shown in figure 2. It can 

 pass readily around a cable drum several feet in diameter, and over 

 the bow sheave of the cable ship without requiring that the ship be 

 stopped. To attain this flexibility, the repeater elements within the 

 container are mounted inside a series of plastic cylinders, successive 

 units being held together by a spring assembly to form an articulated 

 system. Surrounding this series of plastic cylinders is a series of butt- 

 ended steel rings. There are two layers of rings, the joints between 

 successive rings in the two layers being staggered. Over the rings and 

 supported by them against collapse at sea-bottom pressure, there is 

 an envelope in the form of a long tube of thin copper. Over the copper 

 tube are certain protective coatings and armoring wires. 



The repeater enclosure is terminated at each end with a series of 

 seals, comprising, first, a glass-metal seal adjacent to the repeater ele- 

 ments, next, a plastic seal molded to the cable insulation, and, finally, 

 at the extreme ends, a 7-foot-long seal formed within a copper tube 

 which is an extension of the repeater housing. Sea water, in order to 

 penetrate the housing, would therefore have to thread a long multi- 

 barriered path. All the seals are adapted for the sea-bottom pres- 

 sures that they may have to withstand. A partially sectioned por- 

 tion of the seal is shown in figure 3, together with further details of the 

 repeater structure. 



The 51 repeaters in each cable will be located at intervals of 37 nauti- 

 cal miles. They will be fed with direct-current power originating at 

 each shore end, as described later. 



