

PROCEEDINGS OF THE AMERICAN A( LDEMY. 



reeonanoe with the alternating voltage impressed on the system by the 

 periodic impact of the Bound waves. This adjustment was easily made 

 experimentally. 



The proper choice of the transformer PS and the telephone T was a 

 more difficult problem. A theoretical solution of this problem was not 

 at hand, on account of lack of knowledge of the characteristics of the 

 telephone when used as a generator of oscillatory currents and on ac- 

 count of tin- fact that the current through the crystal in the set lary 



is not a simple function of the voltage in this circuit (see Figure 6). 

 Some aid in the choice was had in the following considerations, which 

 served to point vaguely the direction in which experiment was to be 



made : 



l. Since the primary circuit was to be brought to resonance with the 

 oscillations, the inductance of the primary circuit is negligible, it' we 



Q^M 



Figure -. — Electric cii cuit 



may neglect the reaction of the secondary circuit on the primary. With 

 this approximation it follows from elementary considerations that the 

 resistance of the primary coil should be equal to the resistance of the 

 telephone. Experiment soonshowed that the reaction of the secondary 

 circuit was not negligible, and Bince the effect of the reaction of the 

 mdary is to increase the apparent resistance <>f the primary, it fol- 

 lows that the resistance of the primary coil should be somewhat 



than that of the. telephone. 



•_'. The iron cure of the transformer should he such as to be properly 

 magnetizable by the current generated by the telephone, which in fre- 

 quency and intensity approaches to the current used in telephony. 

 Whence it seemed probable that the small terminal transformers used 

 in telephony would have about the proper amount of iron for use in 

 the present experiments. 



