ARMSTRONG, OPERATING FEATURES OF THE AUDION 237 



system. The frequency of the oscillations set up in the circuits by static 

 are, under normal conditions, the same as those of the incoming signal, 

 and the static is therefore never amplified more than the signal. Usually 

 it is amplified to a somewhat lesser extent, especially if regenerative cir- 

 cuits are employed. In the cascade system used for audio frequencies, 

 a different condition exists. It is ordinary practice to connect the dif- 

 ferent stages by means of transformers, and this leads to conditions 

 which cause the system to produce greater amplifications of the higher 

 frequencies. The rate of change of the wing current of the detecting 

 audion produced by static corresponds to a very high frequency, and as 

 such is invariably amplified to a greater extent than the signal. 



There is a second method of receiving continuous oscillations which 



INCOMING 

 SIGNAL 



CURRENT 

 IN L,C, 



l/lVA%uA/~N_X 



wiI1/1(Vm#ih/WI/ia 



Fig. 30 



makes use of the generating feature of the audion, but does not employ 

 the beat phenomena. The amplifying ratio of the audion depends more 

 or less directly on the value of the wing current, and by varying this 

 current periodically there will be a corresponding periodic change in the 

 amplifying power of the audion. Hence an audion arranged to repeat a 

 continuous wave under such conditions will produce in its wing circuit 

 oscillations which vary periodically in amplitude, and which may there- 

 fore be received by a simple audion system. The first audion may be 

 arranged to produce the necessary variation in its amplifying power in 

 the manner indicated in Fig. 39, which also shows the complete circuit 

 for carrying out this method of reception. Here C-^L^Lfi^ is an audio 

 frequency system designed to produce audio-frequency oscillations; and 

 P is a potentiometer for adjusting the potential of the grid so that on the 

 negative part of the oscillation in the circuit, the wing current is reduced 

 practically to zero. The radio frequency circuit C'LCC^ is tuned to 

 the oscillation frequency of the incoming wave. The radio frequency 

 oscillations cannot be detected in the first audion system, as the strong 

 audio frequency current circulating in this system would produce a con- 

 tinuous note in the telephone receivers of such strength as to render in- 



