TELEPHONE SYSTEM OF THE UNITED STATES 



61 



Toll Line Construction 



The construction of toll lines under a wide variety of conditions 

 has required the solution of many interesting problems. The rela- 

 tively high cost of labor in the United States contributes to the ex- 

 tensive use of labor saving machinery, a large amount of which has 

 been developed to meet the particular conditions of telephone con- 

 struction. Figures 48, 49 and 50 illustrate some of the more inter- 

 esting types of labor saving machinery used extensively for both open 

 wire and toll cable construction. 



Numerous special construction problems are, of course, met in 

 specific situations. One of the interesting river crossings is illustrated 

 in Fig. 51. 



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Fig. 51 — Special aerial cable construction across a river. Cable and messenger 

 secured to a catenary suspension wire. 2-spans each about 180 meters long. 



Switching of Toll Circuits 



As far as is economically practicable the toll business is handled 

 by direct circuits without intermediate switching. At the present 

 time this includes 80 per cent of the toll messages. Of the remaining 

 20 per cent, 17 per cent have one intermediate switch and 3 per cent 

 more than one intermediate switch. 



It is the purpose of the Bell Telephone System to design the toll 



