498 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1956 



2 4 6 8 10 12 14 16 18 20 22 24 26 



A' == AVERAGE LOAD OFFERED TO FINAL ROUTE IN ERLANGS 



28 



Fig. 50 — Overprovision of final route trunks when R2 is used instead of Ri 

 as service to first routed traffic. 



and overflowing calls do not return, the variance of the carried load is 

 Fed = a[l - Er, , (a)] fl + aE^, , (a) - aEi, , _i(a)]* (37) 



and the ratio of variance to average of the carried load is 



V 



cd 



= 1 - a [£-1,0-1 (a) - Ei,c(a)]* 



= 1 - /c 



(38) 



These particular forms are due to P. J. Burke. 



