PIERCE. 



THEORY OF COUPLED CIRCUITS. 



311 



waves one tunes a wireless telegraph system of the coupled type to 

 resonance with the use of a given detector, and then changes to a 

 detector of different resistance, it is necessary to shift the wave length 

 of both of the circuits in order to bring the system back to its best 

 adjustment. This is a familiar experience, and serves to explain the 



Figure 7. Relation of optimum wave-length adjustment to damping in 

 Circuit IV, for a given value of 773 and r. (7;3 = .l, r = .30). 



fact that with a vacuum detector of the type of Fleming's valve or 

 Deforest's Audion or Hewitt's Mercury-arc detector one may attune 

 the receiving station without change of its capacity or inductance 

 merely by bringing a magnet up near the gaseous path of the detector. 

 This merely changes the resistance of the circuit, and when the change 

 is made in the proper direction and to the proper extent the system is 

 thereby brought into resonance. The same thing may be effected in 

 some cases by changing the strength of the local heating or ionizing 

 current employed with detectors of this type. 



3. The shifting of the resonance relation with change of resistance 

 of the circuit has an influence on the sharpness of resonance when one 



