DESIGN OF SYSTEM — NORTH ATLANTIC LINK 



53 



100 



90 



80 



70 



ffl 



LLJ 60 



Q 



O 50 



z 



q: 40 



u 



in 



30 



20 



10 



LOW-GROUP 

 ~ FILTER 



HIGH-GROUP 

 FILTER 



42 50 58 66 74 82 90 98 106 



FREQUENCY IN KILOCYCLES PER SECOND 



Fig. 11 — Splitting filters — loss frequency characteristic. 



114 



122 



and filters designed for a military carrier system. The transmitting out- 

 put amplifier is a modified version of one used in the Havana-Key West 

 submarine cable system terminals; the modifications include broader 

 frequency band, lower modulation and sharper overload cutoff. As in the 

 coaxial carrier system, hybrid coils are provided at points in the Bell 

 equipment where quick patching is needed. 



The agreed Canadian bandwidth quota is 26 kc,^ corresponding to six 

 and one-half message telephone channels. The split between the 6^ 

 Canadian channels and the remaining 5| U.S. channels in the "spUt 

 group" was accomplished by specially-designed group-frequency splitting 

 filters, with very sharp cutoff. The loss-versus-frequency characteristics 

 of these filters are shown in Fig. 11. The resulting Canadian half tele- 

 phone channel next to the cut-apart was broad enough to accommodate 



