RADIO COMMUNICATION 



259 



room with the piano will vibrate only when a certain note is 

 sounded. The receiving circuit can be adjusted by changing 

 the values of capacity and inductance, so that it will respond 

 to any frequency or wave-length desired. The reception will 



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FIG. 1 1 8. A simple receiving circuit 



not be interfered with by waves sent from other stations operating 

 unless the wave from such stations is at the same frequency as 

 the wave sought to be intercepted. A very simple receiving 

 circuit that may be tuned by varying inductance only while the 

 capacity is fixed is shown by the diagram in Figure 118. This 



