KFNNELLY AND PIERCE. 



TELEPHONE RECEIVERS. 



127 



of angular velocity 5820 radians per second, and this is the period of 

 the diaphragm, as is shown later by other methods of analyzing the 

 data. The impressed e. m. f. in this experiment was maintained 

 throughout at 0.3 effective volt. 



3000 



■1000 5000 COOO 7000 



ADgular Velocity iu Radians Per Second 



MICRO- 

 WATTS 



GO 



8000 



Figure 4. Curves of motional resistance, reactance, power, and phase, 

 plotted against angular velocity, for watch-case receiver at 0.3 volt. Dots, 

 observed; circles calculated. 



The method of obtaining the motional power curve was as follows: 

 Table III contains measurements of resistance and reactance of this 

 receiver at different frequencies both while free and while damped. 

 The square root of the sum of the squares of resistance and reactance 

 gives directly the impedance. Dividing the impedance into the e. m. f . 

 gives the effective current. The square of the free effective current 

 multiplied by the free resistance gives the free power. Likewise, the 

 square of the damped current multiplied by the damped resistance 

 gives the damped power. The free power minus the damped power 

 gives the motioyial power. These are tabulated for two receivers, for 

 three series of measurements, in Tables VIII, IX and X. 



