1082 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1956 



30 



UJ 



CODE 



rL.Ji..Ji..Ji 

 nR....jin_._. 



CALCULATED MEASURED 



o X 



45 50 55 60 65 70 75 80 



IMPULSE AMPLITUDE AS PER CENT OF SIGNAL AMPLITUDE 



Fig. 11 — Calculated and measured repeater errors for two set codes. 



1 ST NEGATIVE 



OMISSION 

 THRESHOLD ^ 



PULSE 

 HEIGHT 



2 ND POSITIVE 



INSERTION 



THRESHOLD 



= C=Vd 



1ST POSITIVE 



INSERTION 



THRESHOLD 



= b 

 Fig. 12 — Bias levels used in calculating repeater errors. 



the points of discontinuity. Fig. 12 illustrates these various error thresh- 

 olds with reference to a signal pulse. Theoretical curves were plotted 

 using these values and the observed values of timing and signal aniph- 

 tudes as shown on Fig. 11. It can be seen that very good agreement exists 

 between the measured and computed values. 

 The separate lower thresholds for insertion and omission errors may 



