1、ITU-T RECNN*U.4b 73 4862593 058434b LTT 1 INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU TELEGRAPH SWITCHING PARTICULAR SIGNALLING FACILITIES U.46 (03193) INTERRUPTION OF AUTOMATIC TRANSMISSION AND FLOW CONTROL IN THE INTERNATIONAL TELEX SERVICE ITU-T Rec
2、ommendation U.46 (Previously “CCITT Recommendation”) ITU-T RECMN*U*Lib 93 m 48b259L 0584347 03b m The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The IT-T is responsible for studying technical, operating and tariff questio
3、ns and issuing FOREWORD 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 Recommendations on these topics. ITU-T Recommendation U.46 was prepared by the ITU-T Study Gro
4、up 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 Standardization Sector (ITU-T) w
5、as 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 Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector.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 “CCITT, CCIR or IFRB” or th
6、eir 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 expression “Administratio
7、n” 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 microfilm, without permission in writing from the ITU. ITU-T RECMN*U=L)b 93 E 48b2
8、59L 0584348 T72 CONTENTS Page 1 Interruption of automatic transmission . 1 2 Flow control in the interworking environment . 1 2.1 Interworking function IWF . 1 2.2 Telex terminal . 2 2.3 Other networks . 2 Recommendation U.46 (03/93) i I ITU-T RECNN*Um4b 93 II 48b2.591 0584349 909 Recommendation U.4
9、6 (03/93) 1 (b) environment; (c) (4 avoided; (e) that interruption of undesired transmission is required in the Intemational Telex Service, e.g. to apply a that such a procedure could be used to flow-control automatic transmission e.g. in the interworking that a uniform procedure should be applied;
10、that the Quality of Service of the International Telex Service should be preserved and abnormal conditions be that the different types of interworking functions should be taken into account, unanimously recommends that the following procedures should be applied in the International Telex Service: 1
11、Interruption of automatic transmission The stationAWF requiring from the other end interruption of automatic transmission should attempt to prevent further characters being sent by transmitting a sequence of combination No. 20 (in letters or figures shift mode), as indicated in Recommendation S.4, u
12、ntil the transmission is halted, for a maximum of 20 seconds. If the transmission continues after the 20 seconds period, the connection should be cleared forcefully back to the transmitting terminal or function. If the transmission halts, the relevant function may be applied (e.g. return of a servic
13、e signal). 2 Flow control in the interworking environment 2.1 Interworking function IWF Resuming transmission of characters following an interruption may be required in the interworking environment for flow control purposes. However, due to the return of signals to the calling telex terminal over th
14、e backward signalling path, as per the procedure indicated under clause 1, the message will most likely be corrupted. 2.1.1 As the degree of that corruption can not be accurately estimated by the IWF or by the originating terminal, it is recommended to clear the connection with the following message
15、 being forwarded to the originating terminal: EXM TEMPORARY ABNORMAL CONDITION) BK 1 Optional. ITU-T RECMN*U.46 93 = 4862573 0584350 620 I 2.1.2 Alternatively the following procedure may be implemented in an IWF: interrupt transmission as indicated under clause 1; IWF returns the following text to t
16、he originator: EXM TEMPORARY ABNORMAL CONDITION2) IWF informs the recipient of the abnormal condition forwarding the following text: MESSAGE INTERRUPTION - POSSIBLE CORRUPTION IWF attenddmonitors the abnormal condition and after resumption of the normal condition invites the sender to resume transmi
17、ssion with the service signal GA To avoid the possibility of unnecessarily prolonging the chargeable duration, the interval between the halting of the transmission and the recommencement of transmission following the return of the service signal GA should be as short as possible and should not excee
18、d six seconds. Should this period be exceeded, the call should be cleared towards the originating telex terminal with the service signal BK Continuation of the interrupted message should be resumed to the recipient with the following text appended: POSSIBLE INCOMPLETE MESSAGE 2.2 Telex terminal A te
19、lex terminal shall be able to flow control an IWF after successfully having intempted the transmission as per clause 1, by sending the service signal GA to IWF. 2.3 Other networks The flow control procedures in the case of abnormal conditions applicable to other networks which have access to a telex interworking function are described in the relevant Recommendations. An affected telex subscriber shall be informed of such a condition by the code expression EXM TEMPORARY ABNORMAL CONDITION2) 2) ptionai. 2 Recommendation U.46 (03/93)
