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BELL SYSTEM TECHNICAL JOURNAL 



The permissible distance between these repeaters depends on the 

 gauge of wire employed in the circuits on which the carrier circuits are 

 superposed. For this reason the large gauge circuits of the Bell 

 System have been equipped first with the result that practically all 

 the existing carrier installations are installed on the 165 mil wires 



Fig. 3 



which are the largest generally in use throughout the Bell plant. This 

 wire is largely used on the important backbone routes of the country 

 and it is on these that the existing cairier circuits are superposed. 

 In looking over the map of Fig. 4, which shows all the existing carrier 

 installations, this fact will be noted and also that the carrier systems 

 in most cases provide circuits over 250 miles in length. 



It is of interest to note that the application of carrier very com- 

 pletely covers the important cross country routes. In the west the 

 circuits from Portland to Los Angeles are equipped, the transcon- 

 tinental line from San Francisco east to Harrisburg, and the eastern 

 coast route from Bangor to Atlanta with the exception of the all cable 

 sections between Boston and Washington. As each line on the map 

 represents several channels the number of circuits obtained by carrier 



