RADIO EXTENSION LINKS TO TELEPHONE SYSTEM 623 



with a small input and small gain with a large input as the use of as 

 simple a circuit as this will cause the amplifier to adjust itself for 

 maximum gain when no input signal is coming in and in that case any 

 noise on the line may be amplified sufficiently to be troublesome. 

 Also, with such an amplifier the gain will become larger whenever the 

 speaker stops or hesitates and will momentarily overload the trans- 

 mitter with the first syllable on resumption which may result in dis- 



— W/ 



INTE- 

 GRATOR 



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HYBRID 

 COIL 



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I3AIM INCREASE j 

 DISABLER 



Fig. 8 — Vogad (voice operated gain adjusting device). 



tortion of considerable consequence. It is therefore desired that this 

 circuit have a maximum gain which will not make noise troublesome 

 and also be so constructed that the gain during any conversation will 

 remain constant even during hesitation and listening periods, and in 

 which the gain will increase only when speech signals become weaker 

 or the gain decrease when speech signals becoming stronger. To 

 accomplish this one element of the circuit marked "Gain Increaser" 

 receives energy from the input and operates through the gas tubes 



