306 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 13" 



milliampere in the non-oscillatory to 2 milliamperes in the oscillatory 

 state. 



The rise in mean plate current which accompanies the starting of 

 the oscillations is an important feature from the point of view of re- 

 cording radio signals. An ordinary telegraph relay which will operate 

 on one or two milliamperes may be introduced into the plate cir- 

 cuit. The starting of the oscillations will cause the relay to function 

 and the relay contact may be used either to open or close a local circuit. 

 If the local circuit is one operating a chronographic pen the starting 

 of the oscillations may be chronographically recorded. 



Now the change in grid 

 potential necessary to pass 

 from the nonoscillatory to the 

 oscillatory state is very small, 

 so small indeed that it may be 

 provided by a radio signal re- 

 ceived on an antenna suitably 

 connected to the grid of the 

 electron tube of the regenera- 

 tive circuit. Figure 3 shows a 

 suitable arrangement for this 

 purpose. The antenna leads 

 to the tuned circuit which is 

 connected to the grid of the 

 tube through the potentio- 

 meter. The inductance of 



Fig. 3. Radio recording receiver. this tuned cirCUit is COUpled 



regeneratively with an inductance in the plate circuit. The 

 function of the intervening coil we shall consider presently. The os- 

 cillations due to the incoming radio signal cause the grid potential to 

 vary periodically about its mean value. If this mean value is just 

 below the critical one peculiar to the regenerative circuit the incoming 

 signal will cause the critical value to be reached, and local oscillations 

 will be initiated. Unfortunately, however, the local oscillations per- 

 sist even after the mean grid potential has been restored to its orig- 

 inal value below the critical one. To stop these oscillations by chang- 

 ing the grid potential it would have to be lowered considerably below 

 the critical value. We are, therefore, thus far possessed of the means 



