TRANSATLANTIC TELEPHONE CABLE — AFFEL 275 



of Electrical Engineers in 1942, Dr. Oliver E. Buckley, then president 

 of the Bell Telephone Laboratories, summarized the status of and 

 prospects for transoceanic telephony. He commented on the fact that 

 the interruption of the first telephone cable proposal may, indeed, have 

 been fortunate because it offered an opportunity later for a new ap- 

 proach that led to the present project, which is not only technically 

 sound but economically justified, because it provides not merely one, 

 but a large number of telephone circuits. 



SOME BASIC PROBLEMS 



Consider briefly some of the problems that make long deep-sea com- 

 munication difficult. Structurally, the cable is disarmingly simple. 

 It generally consists of a sizable flexible copper wire, surrounded by a 

 layer of flexible insulating material (in the early days guttapercha), 

 which may be covered with some fabric. To give it physical strength 

 to resist abrasion, and tension, it is further covered with a spiraled 

 layer of heavy steel wires. Over-all, the structure may be from % to 

 11/^ inches in diameter. 



Of course, the insulating material must not have any holes to permit 

 the sea water to reach the inside conductor under pressures which, for 

 an Atlantic crossing, may reach several thousand pounds per square 

 inch. It must also withstand electrical pressures, resulting from the 

 voltages necessary to signal over the cable. 



In our present technical knowledge the electrical problems can be 

 approached quite scientifically, but in the early days of transoceanic 

 telegraphy things were not quite so simple. Experimenters with elec- 

 tricity fairly early became aware of the fact that any electrical con- 

 ductor insulated from ground has the characteristic of acting to store 

 or soak up electrical energy to a degree depending on the size of the 

 conductor. This characteristic was termed "capacity." ^ 



Long wire circuits naturally had greater capacity than short cir- 

 cuits. This capacity is not generally harmful in a circuit of established 

 conditions in which the current flows from one end to the other, but it 

 was not at first realized that an effort to vary the current in order to 

 produce telegraph signals could be seriously frustrated by the capacity 

 that exists in a long submarine cable circuit. 



It acts as if the signaling path consisted of a long trough of water 

 and the signals were received as changes in the level of the liquid — but 

 the mass or volume of the water in the trough swamped out most of 

 the level changes that were imparted at the sending end — particularly 

 the fast changes involved in rapid signaling. There would also be 

 considerable time delay as the wave passed from end to end. 



^ More recent terminology is "capacitance." 



