July 19, 1921 eckhardt and karcher: radio recorder 



307 



for setting up local oscillations by the incoming signal, but the instru- 

 ment does not automatically reset itself. 



Means must be provided for killing the local oscillations as soon as 

 the periodic potential variation of the grid has ceased,^ e., when no signal 

 is being received. For this purpose the telegraph relay in the plate cir- 

 cuit is provided with a second contact, insulated from the first, which 



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Fig. 4. 

 is closed when the relay armature is attracted by the relay magnet. 

 The closing of this rear contact short-circuits a low resistance coil of a 

 few turns mounted between the regenerating coils. When short- 

 circuited, this coil provides an effective screen between the grid and 

 plate inductances and regeneration is promptly stopped. The stop- 

 ping of the local oscillations occasions a decrease in the plate current, 

 the relay armature is released and the oscillation-stopping contact is 

 opened. If the potential oscillations of the grid still persist as the ar- 

 mature is leaving the rear contact the local oscillations will immediately 

 build up, the mean plate current will rise, and the relay armature will be 



