564 



BELL SYSTEM TECHNICAL JOURNAL 



gain requirements are favorable has the advantage of economy in 

 saving the cost of the regulating apparatus and in an expected saving 

 in maintenance. 



NEW YORK NEW YORK PRINCETON PRINCETON PRINCETON PHILA,DELPHIA PHILADELPHIA 

 I KS KN . KS KN 



U— 15.45 »+• — 14.45 — »+• — 16.59 >U — 13.22 »-»■« — 13.92 »+•— 14.79- 



J f^lL-ES J J J MILES 



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10 



5 







-5 



-10 



-15 



-20 



-25 



-30 



-35 



-40 



-45 



Fig. 6 — Level diagram of New York-Philadelphia section, showing theoretical 

 maximum effect on 28 kc levels of omitting regulation at the auxiliary repeater 

 stations. 



Noise Suppression Devices 



Two types of noise suppression devices were used on voice frequency 

 circuits to limit noise currents which might enter the cables used for 

 carrier.^ The first of these is a retardation coil designed to suppress 

 longitudinal currents but to have a negligible effect on the metallic 

 currents on the side and phantom circuits. These were installed at 

 voice frequency repeater points, in all voice quads in cables which 

 contained carrier pairs connected to carrier repeater inputs. These 

 coils attenuate longitudinal noise currents at carrier frequencies gen- 

 erated in the voice repeater office which might enter the cable over 

 the pairs used for voice circuits and be induced into the carrier pairs. 

 A total of 3,000 retardation coils was installed along the New York- 

 Charlotte route for this purpose. The coils are connected into the 

 cable conductors on the office side of the point at which the carrier 

 lateral cable is connected to the main cable. These coils were installed 

 in the office cable vault or manhole. Figure 7-A shows a number of 



