EVOLUTION OF INDUCTIVE LOADING 1225 



the iron wire used on the Cuba cables. An important feature of the cable 

 not previously mentioned was a layer of viscous insulating material (under 

 the regular gutta-percha insulation) which protected the strain-sensitive 

 permalloy from the stresses caused by hydrostatic pressure in the great 

 depths of the ocean. 



Demand for other high-speed loaded submarine cables quickly followed 

 the successful demonstration of the New York-Horta cable and several were 

 installed during 1926, reaching a total of about 15,000 miles of high-speed 

 cables. The new installations included the Horta-Emden cable manufac- 

 tured and installed by the Norddeutsche-Seekabelwerke A.G. for the 

 Deutsch Atlantische Telegraphengesellschaft, and the New York-Bay 

 Roberts-Penzance cable manufactured and installed by the T. C. & M. 

 Company for the Western Union Telegraph Company. These particular 

 cables used an improved form of permalloy supplied by the Western Electric 

 Company containing about 80% nickel, 17.5% iron, 2% chromium, and 

 0.5% manganese. This alloy had an initial permeability of about 3700 and 

 provided a higher impedance loading than that used on the first high-speed 

 cable. In consequence, the newer cables were capable of speeds of about 

 2500 letters per minute. 



Other high-speed continuously loaded cables, installed in 1926 and subse- 

 quent years, used permalloy material manufactured under Western Electric 

 Company patent license, in some instances under a special foreign trade 

 name. 



Comprehensive information regarding all features of the high-speed 

 cable projects specifically mentioned above is given in two papers by O. E. 

 Buckley, published in 1925^'* and 1928^^ respectively. 



In passing, it should be observed that the permalloy loaded cables under 

 discussion were not intended for, and were not suitable for telephone 

 communication. For this purpose, a new family of magnetic alloys, the 

 perminvars, was developed.'*^ Their composition centered on 47% nickel, 

 25% cobalt, 20% iron, 7.5% molybdenum, and 0.5% manganese. When 

 used as a thin loading tape, this alloy has electrical and magnetic properties 

 especially suitable for telephone transmission, including very low hysteresis 

 which is very advantageous in the control of all forms of non-linear dis- 

 tortion. 



A Proposed Transatlantic Telephone Cable 



During the late 1920's, there was worked out a design of a perminvar 

 loaded cable suitable for voice frequency telephony between Newfound- 

 land and Ireland (1800 nautical miles). It was of the single core type with 

 a concentric return conductor. Four layers of very thin perminvar tape 



