528 



BELL SYSTEM TECIISICAL JOURXAL 



The successful operation of long circuits of this cable network has 

 been brought about only by the solution of very difificult technical 

 problems, some of which have alread\- been mentioned. It may be 

 of interest to state that the long through circuits in this cable will be 

 in the nature of four-wire circuits; in other words, one pair of small 

 gauge wires with repeaters will be used for talking in one direction and 



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a similar pair so equip|)ed will be used for talking in the other direction. 

 As an illustration of another type of problem involved, it may be of 

 interest to mention that it is necessar>' to employ automatic regu- 

 lators which vary with changes in the temperature of the cable con- 

 ductors, the amplification introduced into the circuit by some of the 

 repeaters. Without regulation, the change in temperature occurring 

 within 21 hours often makes as much as a thousand-fold difference 

 in the amount of electrical energy received over New York-Chicago 

 circuit from the same input, a variation which would, of course, utterly 

 prevent giving service o\er the circuits. 



Aside from the electrical difficulties there were also interesting 

 problems of a mechanic.il engineering nature to overcome in the desing 

 •ind placing of the cable, particularly where it passes through the 

 wilderness <if the .\lkghen\- Mountains as shown in Figs. Sand 4. 



