INSTANTANEOUS COMPANDORS 



715 



Noise susceptibility, therefore, is directly proportional to the magnitude 

 of the signal voltage. When ^ in (3) is replaced by the right-hand side of 

 (11) we get 



5 



N 



Vt 



V 



(12) 



20 25 30 



EXPANSION RATIO, K, IN DECIBELS 



Fig. 6 — Expander parameters. 



This shows that the ratio of instantaneous signal to instantaneous noise 

 voltages at the output of the system is independent of the magnitude of the 

 signal for voltages within the exponential range of the expandor. 



Noise in the transmission medium is assumed to be fluctuation noise of 

 uniform power density. It is convenient to replace v in (12) with the rms 

 value of the noise voltage at the input to the expandor.^^ Designate this 



