344 



BELL SYSTEM TECHNICAL JOURNAL 



The electrode surfaces of the new transmitter unit are so propor- 

 tioned and so spaced relative to each other that the important current 

 paths shift their locations in the carbon mass with changes in angular 

 position in a manner such that the mean effective pressures in the paths 

 and the lengths of the paths result in substantially constant resistance 

 in all positions. Furthermore, the components of the axial motion of 

 the diaphragm effective in changing the contact forces in the paths are 

 also such as to produce essentially constant modulation. Not only is 

 the total resistance of the paths between the electrodes substantially 



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 CD 



5 20 



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20 



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90 75 



60 45 30 15 -15 -30 -45 -60 - 



INCLINATION OF DIAPHRAGM FROM VERTICAL tN DEGREES 



75 -90 



Fig. 4 — Positional characteristics of the transmitter. 



constant, but this resistance also is uniformly distributed between the 

 individual contacts with the result that at no time does the contact 

 potential rise to a value sufficiently high to produce objectionable 

 carbon noise or "burning." These features result in resistance, volume 

 efficiency and carbon noise characteristics which, as is shown by 

 Fig. 4, are essentially independent of angular position. 



Another and perhaps a more exacting criterion of the adequacy of a 

 transmitter from the standpoint of its ability to function satisfactorily 

 in all positions is the extent to which its transmission characteristics 

 at normal speech intensities are adversely affected when immediately 



