130 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



giving the curves of Figure 4 (the bipolar watch-case — cf . Table X) 

 the motional power at resonance is 62 microwatts, which is 20% of the 

 total free input (309 microwatts) and 25% of the total input at the 

 same voltage with the diaphragm damped (247 microwatts). In the 

 case of the bipolar Bell receiver Rb at 0.3 volt (see Figure 5 and 



MICRO 

 WATTS 



200 



OHMS 



so 







60 



40 



20 



cS 



a -40 



o 



o 



-60 



-80 



-100 



160 

 120 



80; 



40 

 



3000 4000 5000 6000 7000 



Angular Velocity in Radians Per Second 



8000 



Figure 5. Curves of motional resistance, reactance, and power, vs. angular 

 ,'elocity, for Bell bipolar, with 0..3 volt. Dots, observed, circles calculated. 



Table VIII) the motional power at resonance was 179 microwatts, 

 which is 41%, of the free input and 69% of the damped input. At 

 0.42 volt with receiver Rb (see Figure 6 and Table IX) the motional 

 power was 338 microwatts at resonance, amounting to 40% of the 

 total power input with diaphragm free and to 68% of the power input 

 under the same e. m. f. with the diaphragm damped. That is to say, 

 if one holds his finger on the diaphragm so as to damp it, and measures 

 the power supplied to this receiver at 0.42 volt, the frequency being 

 resonan.t with the period of the diaphragm, and then takes his finger 

 oil', the telephone emits a loud sound and the power input jumps up 

 68%. 



