126 



BELL SYSTEM TECHNICAL JOURNAL 



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IX 



2 3 4 5 6 



FREQUENCY IN KILOCYCLES 



Fig. 6o 



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2 3 4 5 6 " 7 

 FREQUENCY IN KILOCYCLES 



Fig. 6b 



LOW PASS FILTER 

 CHARACTERISTICS 



3 4 5 6 7 



FREQUENCY IN KILOCYCLES 



Fig. 6c 



Band Pass Filters 

 The two most important types of band pass filter sections — the 

 confluent and the built-out types — are shown in Fig. 7. The resonance 

 of the confluent section in the voice frequency range does not aftect the 



