VIBRATING TELEPHONE DIAPHRAGMS. 



437 



When two independently clamped telephone diaphragms were 

 mounted, one below the other, in parallel planes, the upper sup- 

 ported in the vibration explorer, the lower in the receiver B, and 



A/a/-ura/ Fre<^uency 

 of 'Spring Load, abouf" 

 3/3^. 



Absorph'on /r'eff/on at 

 0/3^ 



Telephone FfECEivEf? B 

 Spring Load al" Center 



>0 ZO 30 40 so 60 



R'e3i\5l'ance-^'^ -^o -zo -lo 



Fig. i6. Distorted Impedance Circle. Spring Load out of Tune with 



Diaphragm. 



both connected rigidly, between their centers, by an aluminum bar 

 6 cm. long, and 2 mm. X 2 mm. in section, the whole system gave 

 an undistorted motional-impedance circle, corresponding to the nat- 



