THEORIES FOR TOLL TRAFFIC ENGINEERING IN THE U. S. A, 433 



will be 



W{x, a, s) = 



Expected overflow calls per unit time 

 Expected calls offered per unit time 



Z (a + sn)jXx, n) - , ./ ^ ^^^ 



sn -\- af{x, y) 



n=0 



X y 



S 2 (« + sn)f(m, n) 



a -{- sn 



m=0 71=0 



X y 



in which n = ^ 2^ nf(7n, n). And when y is chosen so large that/(.r, y) 



7H = 71=0 



is negligible, as we shall use it here, 



L = a 



W(x, a, s) = 



sn 



a -\- sn 



(5') 

 (6') 



1^ 0.5 



< 



"^O 0.4 

 ilZ 



Oo 

 ZZ 0.3 



Ol- 



pllJ 



o5 0.2 



Q. 



o 



? 0.1 



6 TRUNKS 



/ // APOISSON 

 ' ^1 P(C,L) 



5=0.6 



2 4 6 8 



L=LOAD CARRIED IN ERLANGS 



APOISSON 

 P(C,L) 



fly >^- 



f I6j _, 



8 10 12 14 



L = LOAD CARRIED IN ERLANGS 



Fig. 7 — ■ Comparison of trunking formulas. 



