1、ITU-T RECMNJR-54 93 48b259L 05Bb1.52 41b INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU TELEGRAPHY TELEGRAPH TRANSMISSION R.54 (03/93) CONVENTIONAL DEGREE OF DISTORTION TOLERABLE FOR STANDARDIZED START-STOP 50-BAUD SYSTEMS ITU-T Recommendation R.54 (Previ
2、ously “CCITT Recommendation”) FOREWORD The IT 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 and issuing Recommendations on them with a view to stand
3、ardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the IT-T Study Groups which, in their turn, produce Recommendations on these topics. ITU-T Recommendation R.54 was revise
4、d 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 February 1993. In its place, the ITU Telecommunication Standard
5、ization 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 Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector.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 made in the text to references containing the acronyms “CC
6、ITT, CCIR or IFRB” 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 recognized operating agency. In this Recommendation, the e
7、xpression “Administration” is used for conciseness to indicate both a O ITU 1994 A11 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. ITU
8、-T RECMNtR.54 73 4862571 0586154 297 Recommendation R.54 CONVENTIONAL DEGREE OF DISTORTION TOLERABLE FOR STANDARDIZED START-STOP 50-BAUD SYSTEMS (former CCIT Recommendation B.51, Geneva, 1956; amended at Geneva, 1964, at Mar del Plata, 1968 and at Helsinki, 1993) The CCIT, considering (a) that in te
9、legraph communications used in the public telegram service, in the telex service and for leased circuits, over land lines and submarine cables, using 5-unit start-stop equipment at the modulation rate of 50 bauds, a maximum admissible rate of error of 3 per 1OOO alphabetic telegraph signals transmit
10、ted is recommended by Recommendation F. 10 i; (b) recommended by the CCITT; that at present, interruptions of the telephone-type circuit account for a much higher error rate than that (cl that to fix the objectives to be reached to curb interruptions and noise in telephone-type bearer circuits, it i
11、s of interest to indicate how this tolerable error rate of 3 per 100 OOO telegraph signais can be distributed among the telegraph equipment and the circuits bearing the telegraph systems; (d) that telegraph apparatus, particularly the transmitter and the receiver, is itself liable to fortuitous fail
12、ures and it is difficult to distinguish between errors due to these causes and errors due to the probability that the degree of telegraph distortion can exceed the receiver margin, which cannot be ignored; (e) but in planning telegraph circuits, it may be convenient to limit the conventional degree
13、of gross start-stop distortion of complete circuits (including telegraph transmitting apparatus) to the nominal margin of the receiving apparatus; (f) that moreover, if the individual degree to distortion at apparatus input exceeds the margin by about once in 100 OOO, the measurements show that the
14、combined effect of telegraph distortion and fortuitous apparatus failures is manifested by an error rate of about 2 per 100 O00 telegraph signals; (8) Recommendation R.9, NOTE - The result is that the error rate due to interruptions and noise on telephone-type circuits carrying telegraph systems sho
15、uld not exceed 1 per 100 OOO. unanimously declares the view (1) being exceeded is 1 in 100 000; that the conventional degree of distortion should be the individual degre of distortion whose probability of (2) distortion at the receiver input is not more than the nominal margin. that theoretical and
16、planning studies should be carried out in such a way that the conventional degree of NOTES 1 The notion of conventional degree of distortion is useful above all for theoretical studies and planning. 2 For the relation between conventional degree of distortion and practical measurements, reference sh
17、ould be made to i21, i31 and Pl. Recommendation R.54 (03/93) 1 ITU-T RECMN+R.5Li 93 W 4862591 0586155 125 W References u1 CC Recommendation Character error rate objective for telegraph communication using 5-unit start-stop equipment, Rec. F.lO. Pl Conventional degree of distortion. Blue Book, Vol. V
18、II, Supplement No. 4, ITU, Geneva, 1964. 31 Relation between the results of routine measurements of distortion and the conventional degree of distortion, Blue Book, Vol. VII, Supplement No. 5, ITU, Geneva, 1964. 41 CC - Question 7/IX, Annex, Blue Book, Vol. Vn, ITU, Geneva, 1964. 2 Recommendation R.54 (03193)
