EFFECT OF SIGNAL DISTORTION IN MORSE TELEGRAPHY 285 



Limiting Values 

 From Opinion of From Curves of Ac- 

 Kind of Distortion Operators curacy of Reception 



1. Positive bias 40% 45% 



2. Negative bias ..._.._..._ 50% 65% 



3. Positive characteristic distortion ... 58% 55% 



4. Negative characteristic distortion. . . 28% 53% 



5. Fortuitous distortion 51% 85% 



6. Various combinations of distortion. . 50 to 65% 55 to 100% 



5. Judged from the opinion of operators, all types and combinations 

 of distortion with the exception of negative characteristic distortion 

 and positive bias become objectionable at values of about 50 per cent. 

 Negative characteristic distortion appears to become objectionable 

 at about 30 per cent and positive bias at about 40 per cent. On the 

 other hand, judged from the accuracy of reception of the operators, all 

 distortions, with the possible exception of positive bias, become ob- 

 jectionable only at values above about 50 per cent. In the case of 

 combined distortions there is considerable disagreement when large 

 amounts of fortuitous distortion are present. The reason for this is 

 discussed under Section III "Discussion of Results — 4. Effect of 

 Fortuitous Distortion." 



The disagreement between opinion and actual performance is of 

 considerable interest, since it shows that operators will condemn a 

 circuit due to the presence of distortion even though their accuracy of 

 reception is not materially influenced thereby. It is probable, there- 

 fore, that in establishing allowable limits of distortion for commercial 

 telegraph circuits, both the accuracy of reception and the opinion of 

 operators will have to be considered. 



