A SUBMARINE TELEPHONE CABLE WITH SUBMERGED REPEATERS 81 



During the course of manufacture and in splicing on board ship, joints in 

 the copper conductors were silver soldered. For joining the polyethylene in- 

 sulation a special molding machine was designed and built by means of which 

 polyethylene under high pressure and an elevated temperature was applied 

 to the surfaces to be joined. 



The cable was manufactured by the Simplex Wire & Cable Company of 

 Cambridge, Mass., and incorporated the results of a cooperative develop- 

 ment program conducted by this Company and the Bell Telephone Labora- 



UNDERGROUNO 



TYPE D 



TYPE B 



TYPE 



TYPE AA 



Fig. 12 — Cable types. 



tories. The excellent quality of the cable is a tribute to the manufacturer in 

 this very difficult and exacting field. 



Terminal Equipment 



The transmission apparatus at Key West and Havana is mostly standard 

 equipment employed in land line carrier systems, and the operations involved 

 in combining the twenty-four voice circuits into one band and separating 

 them again are largely conventional. Special equalizers, power separation fil- 

 ters and an auxiliary amplifier had to be designed and the standard transmit- 

 ting amplifier used in the J system was modified to accommodate the lower 

 frequency band. A feature of particular interest is the equipment for testing 

 the electrical condition of the repeaters from measurements at Key West. 

 Each repeater contains a sharply tuned circuit by means of which the gain 



