66 



THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1951 



are problems involved in building and maintaining the Miami-Key West 

 connections but these are outside the scope of the present article. 



Telephone communication between the United States and Cuba was initi- 

 ated in 1921, when three submarine cables were laid between Key West and 

 Havana.^ Each cable provided a telephone circuit, operated on a two-wire 

 basis, and two or more telegraph circuits, d-c. and a-c. The cables were con- 

 tinuously loaded with iron wire, insulated with gutta-percha and had return 

 conductors consisting of copper tapes laid on the insulated core and exposed 



P'ig. 1 — Submarine cable repeater. 



electrically to the sea water. These cables were the first ones to employ the 

 copper return conductor, which has also been used in subsequent cables. The 

 copper return was employed after a theoretical study had indicated that the 

 armor and sea water, which for the low frequencies then involved in cable 

 telegraphy furnished a low resistance return conductor, would not be satisfac- 

 tory at voice and higher frequencies. At these frequencies skin effect causes 

 the return current to concentrate in the armor wires, which are naturally poor 



iW. H. Martin, G. A. Anderegg, B. W. Kendall, Key West-Havana Submarine Tele- 

 phone Cable System, AJ££. Transactions, Vol. 41, pp. 1-19, February 1922. 



