KENNELLY AND PIERCE. — TELEPHONE RECEIVERS. 



131 



An examination of the curves of Figures 4, 5, and 6 shows how this 

 occurs. The effective resistance of the receiver, with the e. m. f. at 

 resonance, is not very dift'erent when it is sounding and when it is 

 damped; that is, the motional resistance is nearly but not quite zero. 

 What causes the large consumption of power at the resonant frequency 



350 



300 2 

 250 2 



200 a 



OHMS 

 CO 



40 

 20 

 

 -20 

 -10 

 -CO 

 -80 



a 



150 



100 I 

 o 

 *-^ 

 o 



50 S 



-100 



3000 4000 5000 COOO 



Angular Velocity in Radians Per Secona 



Figure 6. Same as Figure 5, but with 0.42 volt at terminals of Bell bipolar. 

 Power points, calculated; other dots, observed; circles, calculated. 



is the low value of the effective inductive reactance of the receiver at 

 this frequency and the consequent large draft of current from the 

 source. As we go away from the frequency of e. m. f. resonant with 

 the period of the diaphragm, the motional power consumption may be 

 due either to excess of free resistance over damped resistance or to 

 the excess of free current incidental to a decrease of inductance by the 

 motion. 



Effect of Motion on Phase. — The phase angle of the motional 

 impedance for the watch-case receiver is shown in the curve marked 



