440 On Systems with Propagated Coupling. 



without allowance for the influence of time of propagation 

 upon the coupling. 



,/The experimental case — except for the presence of the 

 valves — can be represented by the diagram following (fig. 3). 



Fur. 3. 



, 





1 



E 2 



^ 



H « 



A 





(5 



m '- 8 





. 4* . 



In this diagram M is the mutual inductance between the 

 electric circuits, a^ and a 2 are the mutual coefficients repre- 

 senting the magnetic coupling between the coil and diaphragm 

 in the respective telephones, and fi the corresponding coeffi- 

 cient for the acoustic coupling between the diaphragms. 



The equations are 



L 4 +R d c i +M § 2 +*$=»- 



r 



L *dt 



2 + M§ + < 





/* 





^2 



aA+ r* + "5 +K> > + '* * =0 



leading to an auxiliary equation of the sixth degree. This 

 case is too complicated to justify further account being given 

 of it here. 



The general nature of the effect of propagation is suffi- 

 ciently well represented by case ii. 



