1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU R.55 (03/93) TELEGRAPHY TELEGRAPH TRANSMISSION CONVENTIONAL DEGREE OF DISTORTION ITU-T Recommendation R.55 (Previously “CCITT Recommendation”) ITU-T RECMN+R.55 93 = 48b2.593 058b455 978 FOREWORD The IT Teleco
2、mmunication 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 and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. Th
3、e 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 Recommendations on these topics. ITU-T Recommendation R.55 was revised by the ITU-T Study Group IX (1988-1993) and was a
4、pproved by the WTSC (Helsinki, March 1-12. 1993). NOTES I As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 19
5、93. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector.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 made in the text to references containing the acronyms “CCITT, CCIR or IFRB” or their associated entities suc
6、h 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 recognized operating agency. In this Recommendation, the expression “Administration” is used for conciseness
7、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 microfilm, without permission in writing from the ITU. 1TIJ-T RECHN*R.SS 93 4862591 058b4.56 804 Recommendati
8、on R.55 CONVENTIONAL DEGREE OF DISTORTION (Geneva, 1964; amended at Helsinki, 1993) The CCI“. considering (4 distortion the probability of exceeding which, during a prolonged observation, equals a very small assigned value. that the conventional degree of distortion is (Definition 33.14, Recommendat
9、ion R.140) the degree of NOTE -The assigned value should be specified for each case of utilization. (b) that for standardized start-stop 50-baud systems, the assigned value is 1 per 100 O00 (Recommendation R.54); (cl that to facilitate the use of the conventional degree of distortion and the compari
10、son of studies and plans that have been established with the aid of the conventional degree, it is useful for the probability of being exceeded assigned to the conventional degree to be the same for all telegraph systems (including data transmissions), unless another probability of being exceeded ha
11、s been assigned to the conventional degree of distortion for special studies. (4 Recommendation R.9, unanimously declares the view (1) degree of distortion whose probability of being exceeded is 1 in 100 ; that, unless otherwise specified by the Administrations concerned, the conventional degree of distortion is the (2) that the conventional degree of distortion applies to individual distortion. Recommendation R.55 (03/93) 1
