348 



BELL SYSTEM TECHNICAL JOURNAL 



1714 Ca ^^ 



mo To m, Ti m2 ^WMAA^j-i ms r^ 



rsSs Soz±3 Si zir 



MaaHH 



^2 S 



S3 



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EQUIVALENT CIRCUIT 



13 -20 



-30 



a. o 

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I4S4 



-60 



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z m 



1,1 u 



500 1000 1500 2000 2500 3000 3500 4000 4500 5000 



FREQUENCY IN CYCLES PER SECOND 



Fig, 6 — Pressure and field response characteristics of the transmitter. 



of this type of analysis, their impedance characteristics can be repre- 

 sented to a first approximation by a constant stiffness and resistance, 

 ^555. The mass of the carbon is lumped with that of the central 

 portion of the diaphragm. The grid of the transmitter unit proper is 

 provided for mechanical protection only and has holes large enough to 

 have no reaction on response. When assembled in a handset or desk 



