420 



KENNELLY, TAYLOR— PROPERTIES OF 



bridge, the motional impedance OC of the telephone at this fre- 

 quency, the angle BOC is the lag of the motional E. M. F. behind 

 the velocity producing it, and is equal to the angle p.^. Since the 



The three vector^ (current, 



diaphragm ve/oc/fi/ and count- 

 er electrompf-ive force) refer , 

 to Li'ssaJoU'S figure ohsen/a- 

 tions which ivere ma</e y/hen 

 the current and d/'aphragm 

 vibrational displacements 

 were in ± cophase. 



'Telephone Receiver 

 B 



Impedance Circle 

 10 5 10 10 20 ohrns 



I ' I I I 



Velocity Circle 

 I .5 O 1 2 3 cm/sec 



Inillhhl I I I 



/Vo Load 



"fo -3o -zo -lo 10 zo 30 40 SO /t'cs/'Stance 

 Fig. 4. Undistorted Circles of Motional-Impedance and Velocity. 



depression angle AOD of the motional impedance circle, taken from 

 the observation plot is j8i° -\- 1^-2°, the angle jSi" is immediately deter- 

 mined. The test therefore requires the motional-impedance circle 

 to be obtained over the principal range of frequencies, in Fig. 4 from 



