THE LOADED SUBMARINE TEl.EGH.II'll C.IHI.I-. 373 



tnailf up only of units of resistance and capacity arranged to ap- 

 proximate the (listributeil resistance anfl capacit>' f)f tlie cable. Some- 

 times inductance units are added to l>.il,in(c the small inductance 

 which even a non-loaiietl cal)le has. In ilir actual operation of 

 cables, artificial lines are adjusted with the greatest care and a remark- 

 able precision of balance is obtained. This is necessary because of 

 the great difference in current amplitude of the outgoing and incoming 

 signals, the former being of the order of 10,000 times the latter. It 

 is quite obvious that it will be much nKjre dilticult to secure duplex 

 of)eration with a loaded than with an ordinary cable, since not only 

 do the copp)er resistance and the dielectric capacity have to be bal- 

 anced, but the artificial line must also be provided with inductance 

 and alternating current resistance. Also the sea-return resistance 

 and inductance which vary with frequency must be balanced. 



In view of these dirticullies it will probably be impossible to get 

 as great a proportionate gain from duplex operation of loaded cables 

 as is secured with ordinary cables. However, it is quite evident that 

 it will be possible to secure duplex operation at some speed, since, 

 with loaded as with non-loaded cables, the ratio of received to sent 

 current increases rapidly as the speed is reduced and on this account 

 it is much easier to duplex the cable at low speeds than at high. To 

 make duplexing worth while on a cable with approximately equal 

 traffic loads in Ixjth directions it is in general only necessary to get 

 a one-way duplex speed half as great as the simplex speed. In fact 

 in some cases the operating advantages of duplex would warrant 

 even a slower duplex speed. On the other hand, there are cables 

 on which the tratiRc is largely undirectional through most of the 

 day and which would accordingly require a one-way duplex speed 

 somewhat higher than half the simplex speed to justify- duplex oper- 

 ation. Whether a suflicienth- great speed of duplexing could be secured 

 to justify designing a cable on the basis of duplex operation could 

 not be judged in advance of laying the first cable, and accordingly 

 it was decided to engineer that cable on the basis of simplex operation. 

 Although it was expected that the new cable might at first have to 

 be operated simplex it should not be supposed that any great diffi- 

 culty or loss of operating efficiency was anticipated on this account. 

 The sfx-ed of the New York-Azores cable is so great that to realize 

 its full commercial advantage practically requires working it on a 

 multi-channel basis as, for example, with a Baudot code, multiplex 

 system, similar to that used on land lines. Such a system may be 

 conveniently adapted to automatic direction reversal and with this 

 modification most of the common objections to simplex operation are 



