1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 % TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%0(/.%G0G0.%47/2+G0G0!.$G0G0)3$.15!,)49G0G0/&G0G03%26)#% G0G0.%47/2+G0G0-!.!%-%.4!.$G0G042!&)#G0G0%.).%2).$%4%2-).!4)/.G0G0/&G0G04(%G0G0.5-“%2G0G0/&#)2#5)43G0G0).G0G0-!.5!,G0G0/0%2!4)/.)45G134G0G0Recommend
2、ationG0G0% (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation E.510 was published in Fascicle II.3 of the Blue Book. This file is an extract from theBlue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are iden
3、tical to the Blue Book version and copyright conditions remain unchanged (see below).2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of t
4、his publication may be reproduced or utilized in any form or by any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle II.3 - Rec. E.510 1Recommendation E.5101)Fascicle II.3 - Rec. E.510DETERMINATION OF THE NUMBER OF CIRCUITSIN M
5、ANUAL OPERATION1 The quality of an international manual demand service should be defined as the percentage of call requestswhich, during the average busy hour (as defined later under 3) cannot be satisfied immediately because no circuit isfree in the relation considered.By call requests satisfied im
6、mediately are meant those for which the call is established by the same operatorwho received the call, and within a period of two minutes from receipt of that call, whether the operator (when she doesnot immediately find a free circuit) continues observation of the group of circuits, or whether she
7、makes severalattempts in the course of this period.Ultimately, it will be desirable to evolve a corresponding definition based on the average speed of establishingcalls in the busy hour, i.e. the average time which elapses between the moment when the operator has completed therecording of the call r
8、equest and the moment when the called subscriber is on the line, or the caller receives the advicesubscriber engaged, no reply, etc. But for the moment, in the absence of information about the operating time in theEuropean international service, such a definition cannot be established.2 The number o
9、f circuits it is necessary to allocate to an international relation, in order to obtain a given grade ofservice, should be determined as a function of the total holding time of the group in the busy hour.The total holding time is the product of the number of calls in the busy hour and a factor which
10、 is the sum ofthe average call duration and the average operating time.These durations will be obtained by means of a large number of observations made during the busy hours, byagreement between the Administrations concerned. If necessary, the particulars entered on the tickets could also serveto de
11、termine the average duration of the calls.The average call duration will be obtained by dividing the total number of minutes of conversation recorded bythe recorded number of effective calls.The average operating time will be obtained by dividing the total number of minutes given to operating(includ
12、ing ineffective calls) by the number of effective calls recorded.3 The number of calls in the busy hour will be determined from the average of returns taken during the busyhours on a certain number of busy days in the year.Exceptionally busy days, such as those which occur around certain holidays, e
13、tc., will be eliminated from thesereturns. The Administrations concerned should plan, whenever possible, to put additional circuits into service for thesedays.In principle, these returns will be taken during the working days of two consecutive weeks, or during tenconsecutive working days. If the mon
14、thly traffic curve shows only small variations, they will be repeated twice a yearonly. They will be taken three or four times a year or more if there are material seasonal variations, so that the averageestablished is in accordance with all the characteristic periods of traffic flow.4 The total occ
15、upied time thus determined should be increased by a certain amount determined by agreementbetween the Administrations concerned according to the statistics of traffic growth during earlier years, to take accountof the probable growth in traffic and the fact that putting new circuits into service tak
16、es place some time after they arefirst found to be necessary.5 The total holding time of the circuits thus obtained, in conjunction with a suitable table (see Table 1/E.510),will enable the required number of circuits to be ascertained._1)This Recommendation dates from the XIIIth Plenary Assembly of
17、 the CCIF (London, 1946) and has not been fundamentallyrevised since. It was studied under Question 13/II in the Study Period 1968-1972 and was found to be still valid.2 Fascicle II.3 - Rec. E.5106 In the international manual telephone service, the following Tables A and B should be used as a basis
18、ofminimum allocation:Table A corresponds to about 30% of calls failing at the first attempt because of all circuits being engaged andto about 20% of the calls being deferred.Table B, corresponding to about 7% of calls deferred, will be used whenever possible.These tables do not take account of the f
19、act that the possibility of using secondary routes permits, particularlyfor small groups, an increase in the permissible occupation time.TABLE 1/E.510Capacity of circuit groups(See Supplement No. 2 - Fascicle II.3 of the Blue Book)Table A Table BNumber ofcircuitsPercentage ofcircuit usageMinutes of
20、circuitusage possiblein the busy hourPercentage ofcircuit usageMinutes of circuitusage possiblein the busy hour123456789101112131415161718192065.076.783.386.788.690.091.091.792.292.693.093.493.693.994.194.294.394.494.594.6399215020826632438244049855661467273078884690496210201078113646.656.763.368.372.074.576.578.079.280.181.081.782.382.883.283.683.984.284.6561021522052593133674214755295836376917457998539079611015Note Tables A and B can be extended for groups comprising more than 20 circuits by using the values given for 20 circuits.
