. The Bell System technical journal . // / /V ^, N, N, x + y = 20 P= / 1/ / \ ^ \ \ \ k \ f \ \ \ \ N V. i J \ \ \ \ V \ / \ \ \ \ \ V \ / \ \ \ N \ \ I \ / r r \g=^ \=s \g = 6 ^=, \ \ \ \ I 2 3 4 5 6 7 TOTAL TRUNKS IN MULTIPLES OF (X + y) Fig. 13—Graded multiple efficiency, x + y = 20. P = THE INTERCONNECTION OF TELEPHONE SYSTEMS 545 efficiency of x + y trunks as 13 per cent. This means that the averageload per trunk in the graded multiple is times that in a straightgroup of X + V = 30 trunks at the same probability of loss. From 40+ 36 X / u. 32O r, 28 // / x+y=30 P =
. The Bell System technical journal . // / /V ^, N, N, x + y = 20 P= / 1/ / \ ^ \ \ \ k \ f \ \ \ \ N V. i J \ \ \ \ V \ / \ \ \ \ \ V \ / \ \ \ N \ \ I \ / r r \g=^ \=s \g = 6 ^=, \ \ \ \ I 2 3 4 5 6 7 TOTAL TRUNKS IN MULTIPLES OF (X + y) Fig. 13—Graded multiple efficiency, x + y = 20. P = THE INTERCONNECTION OF TELEPHONE SYSTEMS 545 efficiency of x + y trunks as 13 per cent. This means that the averageload per trunk in the graded multiple is times that in a straightgroup of X + V = 30 trunks at the same probability of loss. From 40+ 36 X / u. 32O r, 28 // / x+y=30 P = // / ^ •n. X z UJ O 24 u. *^^ /; /^ ~\ \ \ \ \ \ u 20 (T UJ Z < 12 O S 8 UJ O /- \ \ V \ \ \ y s \ \ ^ \ \ s \, / \ \ \ \ \ \ V \ / 3- T V = 4 \ = 5 \^ 6 \- UJ d. 0 / \ \ \ \ \ 0 I 2 3 4 567 S TOTAL TRUNKS IN MULTIPLES OF (X -f- y) Fig. 14—Graded multiple efficiency, x + y = 30. P = Fig. 4 we read the average carried per trunk on a straight group of 30as .529. Hence the total load which may be submitted to the graded. 0 I 2 3 4 56 TOTAL TRUNKS IN MULTIPLES OF (X + y) Fig. 15—Graded multiple efficiency, x + y = 40. P = 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. 546 BELL SYSTEM TECHNICAL JOURNAL multiple is A = ()(.529)(105) = To obtain the desired load per subgroup we need only divide by 4. giving a = In terms of one-hundred-second-calls this average per subgroup then equals 36a — 565 calls per hour. As a second example we may set the question: Given 58 trunks tograde on an access oi x -^ y = 20 with either three or six subgroups,which arrangement is to be preferred? We shall have to assume,since we have no additional information, that the decision rests merelyupon the relative efficiencies of the two schemes. From the givendata, gx -{- y = 58, x -\- y = 20, and g =^ 3 or g = 6. We read opposite gx + y _ 5S = ^r- = for
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