Submarine Telephone Cables

Telephone service was established initially²⁶ between the United States and Cuba over three continuously loaded cables laid between Key West and Havana and opened for service in 1921. They are slightly over 100 miles long and arc laid in water more than a mile deep.

The three original Key West-Havana telephone cables were continuously loaded with a layer of iron wire. In later cables Permalloy was used. Not all submarine telephone cables, however, are loaded. Carrier systems are sometimes used on submarine cables, and in such instances²⁷ the loading may be omitted because of excessive carrier-frequency losses.

Important long submarine telephone cables have been installed from Italy to Sardinia,²⁸ from Australia to Tasmania,²⁹ and elsewhere. No transoceanic telephone cables have been laid, however, the word transoceanic implying a major ocean such as the Atlantic.

A submarine transatlantic telephone cable was designed about 1930 and was to be laid between Newfoundland and Ireland, about 2100 miles, but was not installed. No intermediate amplifiers were to be used. By the use of continuous Perminvar (page 62) loading and Paragutta insulation the overall loss and distortion were to be maintained within practical limits.³⁰

Studies have been made³¹ of the possibilities of a transatlantic submarine cable on which perhaps 12 telephone channels could operate. It has been proposed that the cable system be provided with underwater vacuum-tube amplifiers (or repeaters) at numerous points and that these be built into the cable structure.³²