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In closinnin^ the New N'ork-Azort-s cable some a.ssuiii|>(i(iii li.id lo 

 Ik- inatio as to the extraneous interfercnre whicli would be encountered. 

 Theoretical considerations led us to believe that the loaded cable 

 woidd l>c no more subject to external interference than non-loaded 

 cables. It even appeared that it would be less affected by some 

 tyf)es of interference, for, owinjj to the shorter wave-lcnRth for a 

 niven frequency, a disturbance which affects a great many miles of 

 cable simultaneously is less cumulative in its effect at the terminal 

 of a loaded than a non-loaded cable. A reasonable assumption seemed 

 to be that the total o\erall attenuation which could be tolerated 

 for the loaded cable was at least as jjreat as that which experience 

 had shown to be permissible ftir simplex operation of non-loaded 

 cables. This maximum permissible attenuation depends, of course, 

 on conditions of terminal interference and no fixed value can be 

 given as applicable to all cables. However, for average conditions 

 of terminal interference in locations free from pf)wer line disturb- 

 ances and where the cable lies in relati\-ely deep water near to its 

 terminal landing, a reasonable value of total attenuation constant 

 for the fundamental frequency- of cable code is about 10 (8(5.9 T.l f.) for 

 recorder operation and about (78.2 T.U.) for relay operation. These 

 were the approximate %alues assumed for the New York-Azores cable 

 and later experience has demonstrated that they were well justified. ■ 



DlSTORTIUX I.V Lo.XDED ( AHl.KS 



Throughout all of the preceding discussion it has been assumed 

 that the relation between attenuation and terminal interference 

 would limit the speed of simplex operation rather than that distortion 

 of signal shafje would be the limiting factor. Although this is, in 

 fact,'" the case with non-loaded cables it was not -self-evident as 

 regards the loaded cable, and to make reasonably certain that the 

 speed could be determined from the attenuation-frequency relation 

 required a demonstration that the signal distortion of a real loaded 

 cable could be corrected by suitable terminal apparatus. One of 

 the merits long claimed for loading was that it would reduce dis- 

 tortion and, indeed, an ideal loaded cable with constant inductance 

 and without magnetic hysteresis, eddy current loss, dielectric leak- 

 ance and sea return resistance would have very little distortion and 

 would give a speed limited only by terminal apparatus. However, 



>• Recent work of J. R. Carson (U. S. Patent 1,315,539—1919) and R. C. Mathes 

 (U. S. Patent 1,311,283 — 1919) has shown that with the combined use of vacuum 

 tube amplifiers and distortion correcting networks, distortion in non-loaded cables 

 can be compensated to any desired degree. 



