288 



BELL SYSTEM TECHNICAL JOURNAL 



d-c. amplifier is practically the same as at the output of the low-pass filter. 

 The operating point on the demodulated wave may be readily adjusted by 



-500 



■400 



-300 -200 -100 100 200 



FREQUENCY DRIFT IN CYCLES PER SECOND 



^" ig. 26. — Signal bias versus frequency drift for FS transmission — wide filter bands. 



30 



20 



z 



ID 

 U 



a. 

 Q. 



z 



< 



03-10 



-20 



-30 



-100 



-60 -40 -20 20 40 60 



FREQUENCY DRIFT IN CYCLES PER SECOND 



100 



Fig. 27. — Signal bias versus frequency drift for FS transmission— narrow filter bands. 



adjusting the bias voltage at the input to the d-c. amplifier. This arrange- 

 ment differs from the impulse type of d-c. elimination, in which the demodu- 

 lated wave form is effectively differentiated to form pulses but a fraction of a 

 unit dot in length. 



