362 



BELL SYSTEM TECHNICAL JOURNAL 



characteristics of two possible pairs are shown. The absorption peaks 

 of pair "A" at 92 and 127 kilocycles are within the frequency range of 

 channels the fourth and twelfth of the J system and would impair the 

 quality of those channels if pair "A" were used. Therefore, pair 

 "B" is used as the regular path for the system. The quality of the 

 channels obtained from these systems is shown by Fig. 17. Curve 



5.0 



25 







-2.5 



-5.0 



5.0 



2.5 







-2.5 



-5.0 



5.0 



2.5 







600 1200 1800 2400 3000 



FREQUENCY-CYCLES PER SECOND 



3600 



Fig. 17 — Quality of derived circuits, "A" for typical channel of systems on six- 

 i ich spaced wire, " B " and " C " for the best and poorest channels of system on twelve- 

 inch spaced wire. 



"A" is representative of that obtained from a system operating over 

 six-inch spaced wires; "B" and "C" are the best and poorest obtained 

 from the Dallas-Longview system. 



The Dallas-San Antonio, Dallas-Longview, and Dallas-Houston 

 systems were placed in commercial service in September, October, and 

 November, 1938, respectively. Experience with these systems is that 

 the circuits obtained compare favorably with those obtained from any 

 other facilities in quality and continuity of service, and that a definite 

 need has been fulfilled in providing an economical method of increasing 

 the capacity of the existing plant. 



