MULTICHANNEL MODULATION SYSTEM 



41 



bers of channels from one to ten, connected in tandem as described in the 

 preceding paragraph. Two scales of ordinates are shown in this figure. On 



(/) -J 



-J o 



?^ 



Q I- 



D 

 O 2 



o 



15 



10 



5 







-5 



-10 



-15 



■20 



-25 



■30 



-35 



-4 



-40 -35 -30 -25 -20 -15 -10 -5 5 10 15 20 

 INPUT IN DECIBELS FROM 1 MILLIWATT AT LEVEL 

 (1000-CYCLE TONE) 



Fig. 26. Input-output characteristics of PCM channels. 



id o 

 - -J 2 



24 



23 



022 



z 



H21 



- !^ 



u $ 



^u19 



§? 



O Q. 16 

 a.- 14 



12 

 1 1 



?;^ 



O GROUP 1 

 X GROUP 2 



25 



^15 



59 2 0- 



eo^g 



61 o!j 



62'°0 

 _l o 

 CD O 



64 ti Q 



o u 



65 z ^ 



6 6 (O CO 

 O Q 



68-| 



69 ^ 



2 3 



NUMBER OF LINKS 



4 5 



IN TANDEM 



8 9 10 



Fig. 27. Noise measurements on idle PCM channels. 



the left is a reference scale of weighted noise employed in the Western 

 Electric 2B Noise Set; on the right, a scale which relates the corresponding 

 unweighted root-mean-square noise to the nominal maximum undistorted 



