THE INTERCONNECTION OF TELEPHONE SYSTEMS 



545 



efficiency of x + y trunks as 13 per cent. This means that the average 

 load per trunk in the graded multiple is 1.13 times that in a straight 

 group of X + V = 30 trunks at the same probability of loss. From 



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TOTAL TRUNKS IN MULTIPLES OF (X -f- y) 



Fig. 14 — Graded multiple efficiency, x + y = 30. P = 0.001. 



Fig. 4 we read the average carried per trunk on a straight group of 30 

 as .529. Hence the total load which may be submitted " to the graded 



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TOTAL TRUNKS IN MULTIPLES OF (X + y) 



Fig. 15— Graded multiple efficiency, x + y = 40. P = 0.001. 



11 We may use the terms "average submitted" and "average carried" inter- 

 changeably here since at losses of P = .01 or less the difference is negligible. 



