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BELL SYSTEM TECHNICAL JOURNAL 



consider the delay incurred by a single call originating while the trunk 

 is busy. But as calls originate at random, the delayed call is just 

 as likely to have fallen near the beginning as toward the end of the 

 constant interval h during which the trunk is busy. In other words, 

 on the average, the delayed call will have originated in the middle of 

 the constant interval h and thus the average delay incurred will be 

 hjl. This lower limit for the average delay on calls delayed is indi- 

 cated in the lower left-hand corner of each sheet of curves by the point 

 where the axis of abscissae is intersected by a short vertical line. 



It will be noted that the constant holding time delay curves change 

 their direction at those points for which the abscissae are exact multiples 

 of the holding time interval h. No such discontinuities in slope 



I 



Fig. 4. 



