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BELL SYSTEM TECHNICAL JOURNAL 



A. Positive Characteristic Distortion. — ^The curve of Fig. 4 shows 

 the effect of positive characteristic distortion as determined by aver- 

 aging the results of two test curves and a number of qualitative check 

 tests. The effects of this type of distortion upon reception are briefly 

 as follows: The accuracy of reception remained practically constant 

 up to a distortion of about 50 per cent and decreased rapidly above this 

 value. The operators remarked upon the distortion at a value of 

 about 30 per cent and considered the circuit unsatisfactory at about 

 50 per cent. 



10 20 30 40 50 60 70 60 



Per Cent Distortion 



Fig. 5. 



The errors produced by positive characteristic distortion were 

 analyzed for values of distortion from 35 per cent to 65 per cent. The 

 results obtained indicated that most of the errors for distortions greater 

 than 50 per cent were due to a lengthening of dots at the beginning of 

 letters and a dropping out of dots at the middle and at the end of 

 letters. As a consequence a large number of errors were due to the 

 following misinterpretations: H interpreted as B; S as G; N as T; 

 J as K; C, A, J or F as M. In addition an appreciable number of 

 errors were due to miscellaneous interpretations together with a large 

 portion of letters added and omitted. 



B. Negative Characteristic Distortion. — The effect of negative 

 characteristic distortion is illustrated by the curve of Fig. 5 which is an 

 average of three test curves and several qualitative check tests. This 

 type of distortion is of considerable interest due to the fact that a 



