Wide-Band Open- Wire Program System * 



By H. S. HAMILTON 



Radio programs are regularly transmitted between broadcasting stations 

 over wire line facilities furnished by the Bell System. Both cable and 

 open wire facilities are employed for this service. Recently a new program 

 transmission system for use on open wire lines has been developed which 

 has highly satisfactory characteristics. A description of this open wire 

 system and test results obtained with it are given in this paper. 



THE simultaneous broadcasting of the same radio program from 

 a large number of broadcasting stations, in different sections of 

 the United States, has become of such everyday occurrence that the 

 radio listening public takes it as an accepted fact and in many cases 

 does not know whether the program is originating in the studio of a 

 local broadcasting station or in a broadcasting studio in some distant 

 city. The wire line facilities furnished by the Bell System for the 

 interconnection of the radio stations, particularly the wire line facilities 

 in cable, have such transmission characteristics that little detectable 

 quality impairment is introduced even when programs are transmitted 

 over very long distances. 



This cable program system was described in a recent paper.^ More 

 recently a new program system for use on open-wire lines, which 

 possesses transmission characteristics comparable with those of the 

 cable system, was developed and an extensive field trial made involving 

 two circuits between Chicago and San Francisco. This paper describes 

 this new open-wire program system and gives the principal results of 

 the tests made on the two transcontinental circuits. 



In the paper referred to describing the cable system, the various 

 factors and considerations involved dictating the grade of transmission 

 performance that is desired for program circuits were discussed in 

 considerable detail so they will not be reviewed here. The transmis- 

 sion requirements chosen as objectives for both cable and open wire 

 are as follows: 



Frequency Range 



Frequency range to be transmitted without material distortion — 

 about 50 to 8,000 cycles. 



* Published in April, 1934 issue of Electrical Engineering. Scheduled for presen- 

 tation at Pacific Coast Convention of A. I. E. E., Salt Lake City, Utah, September, 

 1934. 



1 A. B. Clark and C. W. Green, " Long Distance Cable Circuit for Program Trans- 

 mission," presented at A. L E. E. Convention, Toronto, June, 1930; published in 

 Bell Sys. Tech. Jour., July, 1930. 



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