BAND Ml mil AND TRANSMISSION PERFORMANCE 



Wl 



The compression and expansion result in a uniform improvement of 26 db 

 for weak signals including the "very weak talker" and a lesser improvement 

 for stronger signals. The noise power in the absence of si)eech is 71 db 



SPEECH VOLUME IN VOLUME UNITS (vu) 

 -33 -10 +7 



(very weak) (average) (very loud) 



■+■ 



-60 -55 -50 -45 -40 -35 -30 -25 -20 -15 -10 -5 

 TONE POWER IN DECIBELS (FROM FULL LOAD) 

 ALSO average power OF CONTINUOUS SPEECH IN DECIBELS 

 (from POWER OF FULL-LOAD TONE) 



Fig. 2— Performance of an experimental instantaneous compandor. 



below the power of the full load sine wave which the channel is designed to 

 handle. The performance is substantially equivalent for telephone purposes 

 to a 71-db circuit without companding, in spite of the fact that for all except 

 the very weak talkers the average noise is greater than with the 71-db circuit. 



