Austin: notes on the audton 489 



is applied to the circuit. In both cases the plate circuit contains 

 the usual dry cell battery of about 25 volts,. the telephones, and 

 a galvanometer for the measurement of the plate current. In 

 the observations shown in figure 1 the gas pressure is that 

 usually found in bulbs of this type. 



The figure shows the grid and plate characteristics and also 

 the grid and plate signals as defined above. The alternating 

 e.m.f. in this case was 0.92 volt, with a frequency of 60 cycles. 

 In the neighborhood of zero D. C. grid voltage the usual de- 

 crease of plate current and increase of grid current are noted, 

 while with changing grid voltage the signals change both in 

 magnitude and sign. These changes are apparently to be 

 explained by the changes in curvature of the two characteristics. 



The same curves are obtained if undamped radio frequency 

 excitation of the same strength is used in place of the 60 cycles. 

 In this case the grid galvanometer is shunted with a low non- 

 inductive resistance to allow the oscillations to pass freely. 

 Here the stopping condenser plays little part. If, however, a 

 megohm is placed in series with the grid galvanometer so as to 

 force the oscillations through the stopping condenser, the ap- 

 pearance of the curves is much changed. The grid signal is 

 positive and nearly uniform over a wide range of grid D. C. 

 voltage, while the plate signal is similarly negative except for 

 strongly negative grid where both signals reverse slightly. 

 Apparently here some other effects appear in addition to those 

 due to the changes in grid and plate characteristics. 



This work is still in progress and will be described later at 

 greater length. 



