1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 - TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-!).4%.!.#% ).4%2.!4)/.!,G0G04%,%0(/.%G0G0#)2#5)4335“*%#4)6%G0G04%34).)45G134G0G0RecommendationG0G0- (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation M.731 was published in Fascicle IV.1 of the Blue B
2、ook. This file is an extract fromthe Blue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identical to the Blue Book version and copyright conditions remain unchanged (see below).2 In this Recommendation, the exp
3、ression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic ormechanical, including photocop
4、ying and microfilm, without permission in writing from the ITU.Fascicle IV.1 - Rec. M.731 1Recommendation M.731Fascicle IV.1 - Rec. M.731SUBJECTIVE TESTING1 The need for subjective testing of circuits depends to a great extent on whether or not automatic orsemi-automatic supervisory, testing and fau
5、lt localization equipment is already provided. For example, subjective testingof circuits is not necessary on routes where ATME No. 2 (as described in Recommendation O.22 1) is available. Also,the supervisory and fault localization functions built into SPC exchanges and digital transmission systems
6、reduce or evenremove the need for subjective testing. For those Administrations wishing to use subjective testing, the methodsdescribed in 2-4 below are recommended.2 Circuits used for the automatic and semi-automatic telephone service may be tested subjectively to reveal grossfaults, by systematic
7、test calls from circuit Terminal A to a telephone located at circuit Terminal B. (SeeFigure 1/M.731.) Such test calling may be done independently of all other tests or combined with functional signallingtest calls as described in the Second method in Recommendations Q.139 2 and Q.163 3 for Signallin
8、g Systems No. 4and No. 5, respectively. Such test calls may be classed as type 3 test calls as defined in Recommendation E.424 4. Theymay be applied on a periodic basis for systematically checking each trunk in a group for excessive echo, clipping, loss,noise, distortion and crosstalk. Any fault sus
9、pected as a result of this subjective check should be investigated in thenormal manner. When type 3 test calls are used in this manner a test telephone is assumed to exist at the distantinternational centre. The test telephone is connected to a local exchange, if possible, not located at the same po
10、int as theinternational centre so as to permit a realistic appraisal of the service quality. The test should be initiated at the outgoingterminal for one-way circuits and at both terminals sequentially on both-way circuits. Such test calls for checking servicequality should be scheduled with the dis
11、tant international centre during light load periods.3 Another method of subjective testing, that may be alternatively considered involves type 1 test calls as definedin Recommendation E.424 4. It permits systematic evaluation from Terminal A to a location at Terminal B whichwould not consist of a te
12、st telephone, as shown in Figure 1/M.731, but rather to a test location at Terminal B that is notassociated with a local exchange. Such an agreement might not be as effective in detecting echo control problems (sincethe simulation of a normal connection would be less realistic) but might be useful w
13、hen the first technique suggestedabove is impractical due to local conditions.FIGURE 1/M.731.D01d01-scFIGURE 1/M.731.D012 Fascicle IV.1 - Rec. M.7314 In order to obtain the greatest value from subjective tests it might be advantageous to apply them in associationwith the tests prescribed in Recommen
14、dation M.610 and with in-station tests such as those for the maintenance of echosuppressors.References1 CCITT Recommendation Automatic transmission and signalling testing equipment ATME No. 2, Vol. IV,Rec. O.22.2 CCITT Recommendation Manual testing, Vol. VI, Rec. Q.139.3 CCITT Recommendation Manual testing, Vol. VI, Rec. Q.163.4 CCITT Recommendation Test calls, Vol. II, Rec. E.424.
