46 



THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1951 



SUM OF FIVE DIGITS 



FIRST DIGIT 



SECOND DIGIT 



THIRD DIGIT 



FOURTH DIGIT FIFTH DIGIT 



Fig. 10— Test signal, boy and bird: single digits, one through five. 



sends sixteen and thirty-two levels. The original, of course, is not quantized 

 and shows a smooth graduation from black to white. It is, however, band 

 limited by the input filter. 



The steps in the five-digit system are even more clearly visible on the 

 picture tube. During some tests in which random noise was added to the 



