Applications of Electricity 



237 



one sending station at a time to be heard. These rapid electric 

 waves now enter the vacuum tube. The antenna, the variable 

 condenser, a transformer, and one part of the vacuum tube form 

 a circuit. The current is supplied to this circuit from the house 

 lighting current, after it has been stepped down by a transformer. 



Keystone View Company. 



A BROADCASTING STUDIO 



Notice the singers standing by the microphones in the foreground. The walls are so 

 constructed that they cause no echoes. 



The purpose of this circuit is to return the waves as nearly as 

 possible to the wave length which they had when they left the 

 microphone in the sending station. The diaphragm in the loud 

 speaker then translates these waves back to sound. 



Tuning. In order to receive messages, the apparatus at the 

 receiving station must be so adjusted that it receives waves of 

 the same length as those broadcast from the sending station 

 desired. The effort to make the stations work in harmony is 



