RADIO COMMUNICATION 



269 



to the grid of the vacuum valve and on the other side to the fila- 

 ment. The plate is then connected in a third circuit through 

 a high-potential battery of about 40 volts, through the telephone 

 receivers, and back to the filament. 



The action is about as follows. When the filament is lighted 

 by the current from the battery at a, which is controlled through 



|b battery 



FIG. 124. Diagram showing the use of the vacuum tube as a detector: 

 (a) antenna; (0 receiving inductance; (g) ground; (r) head set; (p) plate in tube; 

 (g) grid in tube; (/) filament in tube; (vc) variable condenser. 



a rheostat, a stream of negative particles of electricity or electrons 

 passes from it between the wires of a grid and strikes the plate, 

 which is positively charged by the high-voltage battery. This 

 stream of electrons constantly striking the plate will cause a 

 current of electricity to flow through the plate circuit and through 

 the telephone receivers. Any variation in this current, then, 

 will produce an effect in the telephone receivers. 



