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BELL SYSTEM TECHNICAL JOURNAL 



upon the signal combinations that have previously been sent over the circuit. 

 Hence the start transition and the transitions occurring between selective 

 pulses are, in general, delayed by varying amounts. All four types of 

 displacement shown in Fig. 2(B) occur, depending upon whether the transi- 

 tion in question is mark-to-space or space-to-mark and whether it has been 



(A) 



(B) 



(C) 



(D) 



(E) 



(F) 



SPACING "END DISTORTION" 



Fig. 2 — Diagrams illustrating start-stop displacements. 



100 



-40 -20 +20 +40 



BIAS OF RECEIVED SIGNALS 

 PERCENT OF A UNIT PULSE 



Fig. 3 — The bias parallelogram. 



delayed more or less than the start transition. For example, if a space-to- 

 mark transition is delayed less (on an absolute time basis) than the start 

 transition, MB displacement occurs; if more, SB displacement. If a mark- 

 to-space transition is delayed less than the start transition, SE displacement 

 occurs, if more, ME displacement. 



