A Submarine Telephone Cable with Submerged Repeaters 



By J. J. GILBERT 



{Manuscript Received Sept. ii, ig^d) 



The paper describes the recently installed Key West-Havana submarine cable 

 telephone system in which repeaters designed for long life are incorporated in the 

 cable structure and are laid as part of the cable. 



IN APRIL of last year there was installed between Key West, Florida, 

 and Havana, Cuba, a submarine telephone cable system involving a radi- 

 cal departure from the conventional art of long distance submarine teleph- 

 ony. This departure consisted of the inclusion within the armor of the sub- 

 marine cable of electron tube repeaters which are designed to pass through 

 the cable laying machinery and sink to the ocean bottom like a length of 

 cable, and which, over an extended period of perhaps twenty years, should 

 not require servicing for the purpose of changing electron tubes or defective 

 circuit elements. The repeater has the appearance of a bulge in the cable 

 about three inches in diameter and tapering off in both directions to the 

 cable diameter of a little over an inch. The total length of the bulge including 

 the taper at each end is about 35 feet. The bulge is flexible enough so that 

 it can conform to the curvature of the brake drum and of the various sheaves 

 in the laying gear on the cable ship. A repeater, with stub cables, is shown 

 in Fig. 1. 



Historical 



The new cable system, comprising cables Nos. 5 and 6 of the Cuban- 

 American Telephone and Telegraph Company, represents another step in 

 the development of telephonic communication between the United States 

 and Cuba, which has presented many interesting problems. Natural con- 

 ditions make it difficult, if not impossible, to employ some of the usual 

 methods of communication. One such condition is the absence of high ground 

 in Florida that would permit the use of economic radio systems. Another is 

 the stretch of water between Florida and Cuba, which, in places, is as much 

 as 6,000 feet in depth and which restricts the type of cable that can be 

 used. The practical solution has been to go from the point of contact with 

 the Bell System toll lines at Miami, over the Keys to Key West by land 

 line (with some water crossings), thence to Havana, an air line distance of 

 about 100 n.m., by submarine cable of the deep sea type of construction, 

 having a single coaxial circuit, insulated with water resistant material. There 



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