1、ITU-T RECMNLR.56 93 m 4862591 0586357 TTB m INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STAN DARD IZATION SECTOR OF ITU TELEGRAPHY TELEGRAPH TRANSMISSION R.56 (03/93) TELEGRAPH DISTORTION LIMITS TO BE QUOTED IN RECOMMENDATIONS FOR EQUIPMENT AND TRANSMISSION PLANS ITU-T Recommendati
2、on R.56 (Previously “CCITT Recommendation”) ITU-T RECMN*R-56 93 m 4862593 0586358 934 m 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 questio
3、ns 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 Recommend
4、ations on these topics. ITU-T Recommendation R.56 was prepared 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 F
5、ebruary 1993. In its place, the IT 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 Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector.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 be
6、en made in the text to references containing the acronyms “CCITT, CCIR or IFR3” 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
7、 a recognized 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 a
8、nd microfilm, without permission in writing from the ITU. ITU-T RECMNrR-Sb 93 = 4862591 0586359 870 Recommendation R.56 TELEGRAPH DISTORTION LIMITS TO BE QUOTED IN RECOMMENDATIONS FOR EQUIPMENT AND TRANSMISSION PLANS (Helsinki, 1993) The CCITT. considering in particular Recommendations R.5 and R.74,
9、 unanimously declares the view that the following principles should be adopted in setting distortion limits in Recommendations for equipment and transmission plans: 1 Isochronous as well as start-stop limits should be quoted wherever possible. The start-stop limits should be quoted for 5-unit and/or 8-unit codes (with one unit-interval stop-element) where appropriate and gross or synchronous measurement should be specified as appropriate. 2 In many cases the differences between each of these limits will be negligible. If so, this should be stated. Recommendation R.56 (03/93) 1
