THEORIES FOR TOLL TRAFFIC ENGINEERING IN THE U. S. A. 465 



read from Fig. 25, will be an integer. This causes no trouble and S should 

 be carried along fractionally to the extent of the accuracy of result de- 

 sired. Reading *S' to one-tenth of a trunk will usually be found sufficient 

 for traffic engineering purposes. 



Example 1: Suppose a simple graded multiple has three trunks in each 

 of two subgroups, which overflow to C common trunks, where C = 1, 



P^n 



OST NO. 6 



THEORY OBSD 



AVG 5.02 5.06 



VAR 9.95 7.90 



• RANDOM TRAFFIC, a = 5.0 



-OBSD 



-NEGATIVE BINOMIAL 



2 4 6 8 10 12 14 16 18 



n = NUMBER OF SIMULTANEOUS CALLS 



P?n 



--OBSD 



OST N0.14 



THEORY OBSD 



( ) ( ) 



AVG 2.83 2.87 



VAR 3.35 3,34 



RANDOM TRAFFIC, a = 2.8 



-NEGATIVE BINOMIAL 



2 4 6 8 10 12 14 16 18 



n = NUMBER OF SIMULTANEOUS CALLS 



Fig. 22 — Combined overflow loads off'ered to alternate-route OST trunks from 

 lirect interoffice trunks; negative binomial theory vs throwdown observations. 



t«3. 



V, 



ta2,y 



2y^2 



f a,,i 



Fig. 23 — A full access group divided at several points to examine the traffic 

 character at each point. 



