502 



BELL SYSTEM TECHNICAL JOURNAL 



when the speed was 60 w.p.m. The marking and spacing frequencies of the 

 two-source, one-source two-band, and frequency-shift arrangements were 



90 100 no 120 130 140 150 



SIGNAL SPEED IN WORDS PER MINUTE 



Fig. 7— Distortion vs. speed characteristics of single-sideband arrangements and 

 on-off arrangement without channel filters. 



both varied by the same amount from their normal values without changing 

 their relative separation. It is evident from Fig. 8 that the arrangements 

 ranked in the following order as regards the permissible carrier frequency 



