1226 THE BELL SYSTEM TECHNICAL JOURNAL, OCTOBER 1951 



provided the loading, and the loaded conductor was insulated with para- 

 gutta. The suitability of the design for use in deep water was verified by 

 temporarily dropping a 20-mile length on the sea floor in a deep water 

 section of the Bay of Biscay. 



The general business depression of the early 1930's resulted in a post- 

 ponement of the cable project because of its great cost. Later on the project 

 was postponed indefinitely because, in the face of improvements in trans- 

 atlantic radio telephone communicaion, so expensive a cable to carry a 

 single conversation could no longer be justified. 



Additional information regarding this cable project is included in Dr. 

 O. E. Buckley's 1942 paper, "The Future of Transoceanic Telephony," 

 constituting the 33rd Kelvin Lecture before the Institution of Electrical 

 Engineers.'*^ 



Continuous Loading for Paper Insulated Telephone Cables 



Tape and Wire Loading: When permalloy and perminvar first became 

 available, theoretical studies were undertaken to determine the prospects 

 of economic competition with coil loading on ordinary paper insulated 

 telephone cables. Special consideration was given to the use of the mag- 

 netic alloys in situations where coil loading is most expensive, namely, in 

 submarine intermediate cables at river crossings, many of which involve 

 high-frequency carrier telephone operation. None of these studies, however, 

 gave sufficient promise to warrant commercial development work. 

 Electroplated Permalloy Loading: During the middle 1920's, the Bell Tele- 

 phone Laboratories started research work on a radical new concept of 

 continuous loading using electroplated permalloy, which gave some promise 

 of being less expensive than magnetic alloy tape or wire loading. The 

 process involved the electrolytic deposition simultaneously of suitable pro- 

 portions of nickel and iron on the copper conductor, and the use of 

 special heat treatments to obtain the desired characteristic (magnetic and 

 electrical) properties of permalloy. In due course, methods were devised 

 for separating the concentric magnetic layer from the conductor, and for 

 breaking it up into longitudinally discontinuous pieces, so as to secure the 

 most advantageous properties for telephone transmission service, and to 

 provide mechanical flexibility in handling. 



The experimental work was concentrated on small copper conductors, 

 partly because of the more simple process problems, and partly because 

 such combinations appeared to have the best prospects of competing with 

 coil loading from the plant cost standpoint. (N.B. — The amount of permal- 

 loy loading material required to provide a specified inductance per unit 

 length, and its cost, is a direct function of the conductor diameter.) 



