126 



BELL SYSTEM TECHNICAL JOURNAL 



90 



80 



70 



m 60 



50 



40 



30 



20 



-4 -3 -2 -I +1 +2 



FREQUENCY FROM CARRIER IN KILOCYCLES 



+ 5 



Fig. 1 — When plotted in cycles removed from the carrier frequency, the insertion 

 loss frequency characteristics of each of the twelve crystal channel filters are for all 

 practical purposes identical. 



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-^W^- BALANCED 

 I INDUCTANCE 



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CRYSTAL ELEMENT 



MECHANICALLY ONE 



ELECTRICALLY TWO 



Fig. 2 — The schematic circuits of each of the twelve filters are the same except 

 for the addition of the condenser shown by the dotted lines which appears only in 

 the two lowest frequency filters. 



