CARRIER-CURRENT COMMUKICA TIOX 



641 



showing the filters for separating the various circuits at the terminals, 

 together with the balancing arrangement. In Fig. 6 are shown the 

 essential parts of one channel together with the amplifiers and the 

 hybrid coil which are common to all the channels. For convenience, 

 some of the battery and auxiliary circuits have been omitted in the 

 figure. 



At the time the system was under development, it was uncertain 

 that balanced operation of all channels over a single cable would be 

 practicable, so that an alternative arrangement involving substan- 



CARRIER LOADED 

 AERIAL CABLE , 



LOS ANGELES 



A'ALON CENTRAL OFFICE 



tially four-wire operation over the two cables was provided for. With 

 this arrangement, which is shown diagrammatically in Fig. 7, all 

 transmission in one direction takes place over one cable, while trans- 

 mission in the opposite direction is effected over the second cable. 

 No balancing equipment or hybrid coils are employed. Such an 

 arrangement would increase the system stability, if such were re- 

 quired, but would limit the total carrier capacity of the two cables 

 to six channels. In the event of the failure of one cable, operation 

 with such a system would be impossible, and it would be necessary, 

 at that time, to revert to the two-wire arrangement as described 

 above, with a possible reduction in the o\-er-all gain or a reduction 

 in the number of operating channels. 



