Although in 1928 the Bell Laboratories first proposed a transatlantic 

 telephone cable which was to be a single-conductor, continuously- loaded 

 nonrepeatered system, the first such transatlantic telephone cable was 

 not laid until 1956 between Clarenville, Newfoundland, and Sidney Mines, 

 Nova Scotia. The prototype to this cable was laid in 1950 between Key 

 West and Havana. It was a twin cable system, one cable "go", the other 

 "return", with flexible one-way repeaters; 24 channels were available. 



In 1952 C. S. Lawton developed a lightweight cable for telegraphy 

 by eliminating the armor, and in 1963 the first lightweight cable was 

 used between Florida and Kingston, Jamaica. The cable was designed in 

 America. In 1961 the first submarine cable with a high tensile steel 

 center strain member was made. 



The use of working E-M cables in the ocean is a relatively recent 

 development. The 1950 's saw the development of oceanographic sensors 

 that were lowered and raised from shipboard using small diameter electro- 

 mechanical cable. In the 1960's seismic arrays had evolved into such 

 great lengths that strain members had to be put into the signal cables. 

 The 1960's also marked the beginning of deep-towed instrument packages 

 and sensors such as side-scan sonar. These E-M cables usually used the 

 external contrahelical armor as the strain member with several internal 

 types of conductors. 



The technology of working E-M submarine cables has benefited from 

 the science of well-logging. Since the invention of the electric log 

 by Schlumberger in the 1920' s, most oil exploration drill holes have had 

 various sensors, tools, and gadgets lowered into them by E-M cable. The 

 logging of oil exploration drill holes is comparable in depths and pres- 

 sures to working in the sea. In 1972 a well was drilled in Oklahoma to 

 a depth of 30,000 feet. The pressures for anv given depth are usually 

 higher than those experienced in the ocean because drill holes are 

 generally filled with drilling muds that have specific gravities higher 

 than that of seawater. 



Temperatures are extreme, increasing with depth, contrary to the 

 oceans. The higher temperatures of drill holes present problems which 

 relate only peripherally to ocean work — for instance, in 1965 poly- 

 propylene was developed as an insulator. 



Extreme corrosion problems of cables are encountered in drill holes, 

 especially where deep wells penetrate salt strata. For instance, salt- 

 supersaturated drilling mud is used to drill through salt formations to 

 prevent dissolving the sides of the bore hole. Conventional cables are 

 used under these severe conditions. External armor is made of standard 

 improved plow steel; the only concession to the hot brine environment is 

 the sluicing of the cable as it is retrieved from the hole — this being 

 more cost effective than using corrosion-resistant materials. 



In the early 1940' s the Schlumberger Company began using external 

 steel wrapping on cables as a strain member to replace their "rag-line" 

 cables which carried the conductors outside of the internal strain mem- 

 ber. The "rag-line" was marked every 100 feet or so with paint as a 

 means of measuring the amount of cable out. In the late 1940' s the 

 Schlumberger Company began to use magnetic marks spaced every 100 feet 

 on the cable. These magnetic marks were impressed on the cable by placing 

 both poles of a horseshoe magnet against the cable and simplv rotating the 



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