678 



Professor J. A. Fleming 



[June 4, 



cently shown, of the non-h'near form of the characteristic curve. In 

 other words, of the fact that the conductivity of the ionised gas is a 

 function of the voltage applied to it, and in this second method the 

 valve and receiving circuits are arranged as shown in Fig. 20. In 



-wwwww^ I — — 



n \n\ 



Cp 



\±J^^m^ 



Fig. 18. Fig. 19. 



Connections for Oscillation Valve used as Radiotelegraphic 



Detector. 



this case, we have to apply to the ionised gas a unidirectional elec- 

 tromotive force which corresponds to a point of inflexion on the 

 characteristic curve, and then to add to this voltage the alternating 

 voltage of the oscillations set up by the incident electric waves in the 

 receiving circuit. The result is to cause a change in the averas^e 



Fig. 20.— Connections for Oscillation Valve used as a Radio- 

 telegraphic Detector. 



value of the current through the telephone, and therefore to produce 

 a sound in it, long or short, according to the number of trains of 

 waves falling on the antenna. This last method, then, requires the 

 application in the telephone circuit of an accurately adjusted steady 



