KENNELLY AND PIERCE. 



TELEPHONE RECEIVERS. 



147 



Thus we have methods of deterininiiifi: both coo and A. The experi- 

 ments, on the other hand, do not permit a direct determination of the 

 quantities m, r, and s; hut it would seem that by adding a known 

 mass, as a small load, to the center of the diaphragm and repeating 

 the series of measurements, these quantities should be capable of 

 determination. 



VI. Comparison of Experimental Results with Theory. 



An examination of the experimental results with the aid of the 

 theory al)ove developed gives the following results, which may be 

 called the characteristics of the several receivers (Table XI) : 



TABLE XL 



Summary of Characteristics of Receivers. 



The method of obtaining these characteristics was as follows: 

 The circular graphs of Figures 7 to 11 were plotted. The diameter 

 of the motional impedance circle and the angle of depression of this 

 diameter below^ the axis of R'—R could be measured off at once on the 

 diagram. The value of co at the free end point of the diameter could 

 also be read. or obtained by interpolation; this co is the cOg of the dia- 

 phragm. The logarithmic decrement per second A could have been 

 obtained by either of the two methods derived in the discussion of the 

 theory, equations (41) or (42); but a third method was employed; 

 namely, by the use of the more general equation (39), in which several 

 values of a and the corresponding values of co from the circular graphs 

 were substitutetl, and the values of A so obtained were averaged. 



