I9IS-] 



SURFACES OF TELEPHONIC DIAPHRAGMS. 



97 



proportional to, the vibrations of the diaphragm at the point of 

 contact. 



The vibration explorer is shown in side elevation at Fig. i, in 

 top view at Fig. 2, and in section, through center of the diaphragm, 

 in Fig. 3. A fairly massive rectangular brass frame holds a plate 

 sliding in grooves. The crank at the bottom of Fig. i controls this 



Fig. I. 



Fig. 2. 



sliding motion, with the aid of the set screw at the other end. At 

 the center of the sliding plate is a circular frame, into which is 

 clamped the diaphragm to be tested. The circular frame can be 

 rotated in its own plane by means of the crank at the right hand 

 of Fig. I, 



