ARMSTRONG, OPERATING FEATURES OF THE AUDION 235 



mospheric disturbances produce a musical note due to shack excitation 

 of the audio frequency system. Very loose coupling with the wing cir- 

 cuit of the first audion is a partial remedy for this. There are times, 

 however, when interference is more troublesome than static, and in such 

 cases the method may be used to great advantages. If desired, both 

 radio and audio frequency tuning can be carried out in the same audion 

 as indicated in Fig. 22. This combination is apt to be somewhat trou- 

 blesome to operate as a cumulative amplification is obtained in the audio 

 frequency as well as in the radio frequency system. 



Cascade Systems 



Where a greater amplification than can be obtained with one audion 

 is required, cascade working of the radio frequency systems may be' re- 



FiG. 28 



sorted to by coupling together two or more audion systems, each con- 

 nected as already described, in. the manner indicated in Fig. 28. The 

 incoming oscillations in the first audion system are amplified in the usual 

 manner and set up oscillations in the second system by means of the 

 coupling ilfg. The oscillations initially set up in the second system are 

 again amplified, and then rectified in the second audion to produce audi- 

 ble response in the telephones. For the reception of spark signals, con- 

 siderable adjustment is required to get the best results without causing 

 one or the other, or both, of the systems to generate oscillations. It will 

 be found that after the first circuit is adjusted to the point of oscillation 

 and the second is coupled with it, the strength of signal in the first sys- 

 tem will be reduced owing to the withdrawal of energy from it by the 

 second system. The signals may then be again brought up in strength 

 by increasing the coupling between the grid and wing circuits of the first 



