1、ITU-T RECMNaR.5 93 486259L 0586143 403 INTERNATIONAL TELECOMMUNICATION UN ION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU TELEGRAPHY TELEGRAPH TRANSMISSION R.5 (03/93) OBSERVATION CON DITIONS RECOMMENDED FOR ROUTINE DISTORTION MEASUREMENTS ON INTERNATIONAL TELEGRAPH CIRCUITS ITU-T Recommen
2、dation R.5 (Previously “CCITT Recommendation”) ITU-T RECMN*R*5 93 4862593 0586344 34T FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The ITU-T is responsible for studying technical, operating and tariff questions
3、 and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendat
4、ions on these topics. IT-T Recommendation R.5 was revised by the ITU-T Study Group IX (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 Februar
5、y 1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendation, no change has been ma
6、de in the text to references containing the acronyms “CCITT, CCIR or IFXB or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure. 2 telecommunication administration and a rec
7、ognized operating agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a O ITU 1994 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and mic
8、rofilm, without permission in writing from the ITU. - ITU-T RECMN+Rm5 93 = 48b259L 058bl145 286 = Recommendation R.5 OBSERVATION CONDITIONS RECOMMENDED FOR ROUTINE DISTORTION MEASUREMENTS ON INTERNATIONAL TELEGRAPH CIRCUITS (New Delhi, 1960; amended at Geneva, 1964, Mar del Plata, 1968, Geneva, 1980
9、 and Helsinki, 1993) The CCITT, considering (a) Recommendations R.5 1, R.5 1 bis, R.54 and R.55; (b) that, for the measurement of the degree of distortion of signais on an international telegraph circuit, it is necessary to specify the best condition of observation in order to be sure that the measu
10、rement obtained gives a good indication of what the performance of the circuit will be during periods of normal traffic; (cl the load on the maintenance services; that the observation conditions should be such that their duration or their complexity does not unduly increase (4 degree of individual s
11、tart-stop distortion using distortion analyzers, the results of which seem to be in agreement, that certain Administrations, to determine these conditions, have carried out statistical measurements of the unanimously declares the view (1) type of circuits concerned; that the tests should be camed ou
12、t at nominal modulation rates of 50, 75, 100 and 200 bauds, depending on the (2) that the text transmitted during measurements should be that of Recommendation R.51 bis; (3) that the degree of transmitter distortion of text signais should not exceed 1%; (4) that, during normal maintenance tests, the
13、 duration of the observation should correspond to the examination of at least 800 significant instants, whatever the type of distortion meter used, isochronous or start-stop. At a modulation rate of 50 bauds this results in an observation period of about 30 seconds. At other modulation rates, the ob
14、servation should last about 20 seconds; NOTE - The period of observation required to assess properly the performance of tandem connected code-independent time-division multiplexors which are not synchronized to one-another may be much longer than for voice-frequency telegraph equipment. The probabil
15、ity of occurrence of this distortion and the duration of measurement to be assumed will differ in each case and requires further study. (5) that, when making start-stop measurements using test equipment that does not register the peak early and peak late reading simultaneously, the observation perio
16、d should be divided into two more or less equal parts: one part during which the significant instants in advance of their theoretical position could be observed and the other part during which the significant instants coming later than their theoretical position could be observed. Recommendation R.5 (03/93) 1
