262 BELL SYSTEM TECHNICAL JOURNAL 



simplex, both cables being of the same length and size. The latter 

 condition will be met if the diameter of the loaded conductor measured 

 over the permalloy is the same as that of the copper conductor of 

 the non-loaded cable and if the thickness of gutta-percha is the same 

 for both. On this basis one can say that for cables of lengths from 

 about 2000 to 3500 miles the loaded cable has approximately five 

 times the traffic capacity of the corresponding non-loaded cable, 

 this gain being obtained, of course, with a relatively small increase 

 of cost. 



A similar comparison might be made for shorter cables but it would 

 have relatively little significance since in any practical case the loaded 

 cable would probably not be made to have the greatest possible speed 

 consistent with practicable size but would be designed with regard to 

 the limitations of terminal apparatus or connecting lines. The 

 problem becomes more complex as the assumed length is reduced 

 since the shorter is the cable the greater are the number of possible 

 ways of obtaining the desired speed and the more is the speed de- 

 pendent on terminal equipment. It is, however, safe to say that, 

 where the demand for communication is sufficiently great, loading 

 will prove advantageous for cables of all lengths down to perhaps 

 100 miles or less, but for cables much less than 2000 miles long the 

 electrical design of any particular cable will depend greatly on the 

 use which is to be made of it. 



In view of the great gain due to loading long cables it is most 

 probable that all very long cables of the future will be loaded and it 

 is likewise probable that long cables will be used in some cases where 

 previously several short non-loaded sections with repeating apparatus 

 would have been used. Loading will also be used to a considerable 

 extent on shorter cables but it should not be expected that all of the 

 shorter cables will be loaded since there are many cases where the 

 demands for communication which can now be foreseen are so limited 

 that they can be met more economically by non-loaded than by loaded 

 cables. 



In Malcolm's prediction of the loaded ocean cable, to which I 

 have previously referred, he went so far as to suggest that even though 

 the first loaded ocean cable would probably be of the continuously 

 loaded type, ultimately coil-loading might be resorted to. Malcolm, 

 of course, was not in a position to take into account the eff"ect of such 

 a radically new material as permalloy, and with the materials which 

 were known to him coil-loading appeared to offer possibilities which 

 continuous loading did not. It is interesting therefore to examine the 

 present apparent merits of coil-loading with regard to its application 

 to transoceanic cables. 



