1、- CCITT RECMN*F=Bb 91 48b2591 0561158 4 I NIE RNATIONAL TELECOMMUN CATION UN ION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONS U LTAT I V E COM M ITT E E TELEGRAPH AND MOBILE SERVICES OPERATIONS AND QUALITY OF SERVICE F.86 INTERWORKING BETWEEN THE INTERNATIONAL TELEX SERVICE AND THE VIDEOTEX
2、SERVICE Recommendation F.86 i Geneva, 1991 CCITT RECMN*F.Bb 91 4862591 85b1L59 b INTERNATIONAL TELECOMMUN CATION UN ION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONS U LTATIVE COM M ITTE E TELEGRAPH AND MOBILE SERVICES OPERATIONS AND QUALITY OF SERVICE F.86 INTERWORKING BETWEEN THE INTERNATIO
3、NAL TELEX SERVICE AND THE VIDEOTEX SERVICE Recommendation F.86 i Geneva, 1991 - CCITT RECMN*F-86 911 W 48625911 05b111160 2 FOREWORD The CCIT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the International Telecommunication Union (ITLJ). CCIT is responsib
4、le for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The Plenary Assembly of CCITT which meets every four years, establishes the topics for study and approves Recommendations prepared by it
5、s Study Groups. The approval of Recommendations by the members of CCITT between Plenary Assemblies is covered by the procedure laid down in CCIT Resolution No. 2 (Melbourne, 1988). Recommendation F.86 was prepared by Study Group I and was approved under the Resolution No. 2 procedure on the 1 lth of
6、 October 1991. CQT NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication Administration and a recognized private operating agency. O ITU 1991 All rights reserved. No part of this publication may be reproduced or utilized in any form
7、 or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. CCITT RECMN*F.Bb 91 4Bb2.591 0561LbL 4 9 Recommendation F.86 INTERWORKING BETWEEN THE INTERNATIONAL TELEX SERVICE AND THE VIDEOTEX SERVICE 1 introduction 1.1 the internauonal
8、 telex service and the videotex service. This Recommendation defines the service requirements and operational procedures for interworking between 1.2 Other relevant Recommendations are: - F.300 defining videotex service aspects; T-Series Recommendations on videotex technical aspects; - - F.60, F.69
9、and other F-Series Recommendations on the international telex service aspects; . - U-, R- and S-Series Recommendations on switching, terminal and transmission aspects of the telex service; U.206 on technical aspects specific to telex/videotex interworking. - 2 Service principles 2.1 Quality of Servi
10、ce perceived by subscribers to either service and within that service is not degraded. Interworking is intended to extend the usefulness and accessibility of both services, while ensuring that the 2.2 Interworking between the telex and videotex services shall be provided by means of a telexlvideotex
11、 conversion facility (VTXCF), the two sides of which comply with the telex and videotex service requirements respectively. The additional service requirements concerning interworking are specified below. 2.3 At least in international relations, the following general principles apply: a) interworking
12、 shall be automatic; b) in principle, the telex network should be used to provide the international connection; consequently the VTXCF should normally be located in the same country as the videotex service user, as shown in Figure lF.86; c) nevertheless, where bilaterally agreed by the two Administr
13、ations concerned, an international videotex connection may be used with the VTXCF in the telex subscribers country. In that case, arrangements may be needed to cover practical operational aspects such as routing, differing protocois and tariffs. 2.4 Interworking in the telex-to-videotex direction sh
14、ould allow for a message handling. Telex subscribers should normally limit their messages to a 40 character line length, otherwise the format of the original message cannot always be preserved when presented on the videotex terminal. Where necessary, the VTXCF will automatically adjust the layout to
15、 suit the videotex terminal requirements. Telex subscribers should be made aware that some videotex terminals are not able to provide a hard copy of the message received. The Administration may provide a hard copy delivery service as an additional option, Recommendation F.86 1 international boundary
16、 Service boundary Country A Country B / / I d-p: Videotex service )-L Videotex Telex network )-f Telex network service user -. -_ Telex - -/ -/ - / terminal 4 L11 -7 b Videotex service TO1 O1 170-91 Telex service FIGURE 1E.86 Telex-videotex interworking model 2.5 Interworking in the videotex-to-tele
17、x direction shall provide the capability to terminals accessing a videotex service to send messages to terminais of the international telex service. The VTXCF shall handle such messages on a store-and-forward basis. In order to maintain similarity between the transmitted and received messages, the v
18、ideotex terminal or user should restrict each message to the character repertoire of International Telegraph Alphabet No. 2, any other characters being converted by the VTXCF to meet the requirements of the international telex service in accordance with Recommendation S.18. 2.6 It is the responsibil
19、ity of the VTXCF to perform the following conversions, where necessary: - service procedures; - transmission rate; - code; - linelength; - insertion of the necessary control characters (figure-shift, letter-shift, carriage-return, line feed). 3 Methods of interworking 3.1 Considering: a) that videot
20、ex terminals may have access to public data networks whose numbering plan is defined in Recommendation X. 121; that signalling on international telex trunks allows a maximum of 12 digits to be transmitted, b) the two following methods of interworking between the telex service and the videotex servic
21、e can be provided: i) ii) interworking with one-stage access from the telex subscriber; interworking with two-stage access from the telex subscriber. 3.2 account possible implications of the operational procedures to foreign telex subscribers. It is up to the Administration to decide which method ca
22、n be provided. Administrations should take into 2 Recommendation F.86 CCITT RECVN*F.Bb 91 = 4862593 0563363 8 3.3 The access method employed by the videotex user to the VTXCF is a national matter. 4 General service requirements for the telex-to-videotex direction 4.1 The complete call in the one-sta
23、ge selection case and access to the VTXCF in the two-stage selection case should appear to the calling telex subscriber as a normal telex call, apart from the composition of the VTXCF answerback. 4.2 national matter. The called videotex address should be validated on each call. The validation proced
24、ures applied are a 4.3 The procedure to be followed should the validation result be negative, Le. the called videotex address does not exist, or is in a not-ready condition, controlled or otherwise, will depend on whether both the telex network and the VTXCF are operated by the same Administration o
25、r not. These procedures are described in $5 6 and 7. 4.4 24000 characters for each call. The storage capacity of a VTXCF shall be enough to allow a guaranteed message of length of 4.5 If abnormal conditions occur (see Recommendation U.206, Annex A for details), the VTXCF shall route any message rece
26、ived so far to the videotex address, adding a header with information that the message might be incomplete. 4.6 It is the responsibility of the Administration providing the VTXCF to arrange alternative means of delivery of a message which was not retrieved by the videotex user, either through not lo
27、gging-in to the service or by not retrieving the message within a reasonable time after storage in the videotex system. This time period is for further study. 5 General service requirements for videotex-to-telex direction 5.1 The videotex user shall access the VTXCF in accordance with national requi
28、rements. 5.2 The message shall appear at the telex terminal as a normal telex message. 5.3 The sender shall always be informed, on request, of the status of each message. 6 interworking using one-stage selection procedure for the telex-to-videotex direction 6.1 messages and may be assigned a telex n
29、umber that is part of the national telex numbering plan. 6.2 subscriber. In this case, the videotex subscribers address shall be registered with the VTXCF for receipt of telex The call to the videotex address shall require normal telex procedures on the part of the calling telex 6.3 The received sel
30、ection information should be validated as being proper to a registered videotex address. If the validation is successful, the VTXCF should always provide the answerback of the requested videotex address, formatted in accordance with Recommendation F.74. Input of text may then commence. 6.4 on whethe
31、r the telex network and the VTXCF are operated by the same Administration. If validation of the received selection information is unsuccessful, the procedure to be followed will depend 6.4.1 Where the telex network and the VTXCF are both operated by the same Administration, the VTXCF may return the
32、service signal NP and clear in the case of unsuccessful validation. If the validation is successful but the videotex facility addressed is in a not-ready state, the appropriate service signal should be returned by the VTXCF to the originating telex subscriber (DER, ABS or OCC). Recommendation F.86 3
33、 - CCITT RECMN*F-Bb 91 m 4862591 05b11b4 T m VTXCF (Note 1) t national telex number 4 + VTXCF 6.4.2 followed in the case of an unsuccessful validation should be in accordance with Recommendation F.74. Where the telex network and the VTXCF are not provided by the same Administration, the procedures t
34、o be -0 5. 6.5 Foilowing clearing of the telex connection, text delivery from the VTXCF to videotex should be initiated. The videotex user should be informed about the presence of a message as soon as he logs-in to this service. 7 interworking using hvo-stage selection procedure for the teiex-to-vid
35、eotex direction 7.1 for a videotex user consists of more than 12 digits, two-stage selection must be used. Where it is not possible to assign a telex number to a videotex user and where the total selection information In this case, the VTXCF should be assigned a telex number which is part of the nat
36、ional telex numbering plan of the country in which the VTXCF is located. The address of the videotex service user should be input in the second stage, the first stage being required to access the VTXCF itself. 7.2 Connection to the VTXCF shall be accomplished using normal telex procedures. 7.3 accor
37、dance with Figure 2F.86. The format of the VTXCF answerback to be returned in the first stage of selection shall be formatted in 0 Telex network identification code in accordance with Recornmendation F.69. Note 1 - If the national telex number of the VTXCF exceeds 6 or 7 digits, the mnemonic part of
38、 the answerback may be reduced to VTX. However, this is not recommended and is for further study. Note 2 - It shouId be noted that networks exist which use answerback codes which are arranged in an order other than the preferred order as specified in Recommendation F.60. FIGURE 2P.86 Format of VTXCF
39、 answerback 7.4 The VTXCF should request the answerback of the calling telex subscriber in accordance with Recommendation S.23. The procedures to be followed to determine the calling telex address from the received answerback shall be in accordance with Recommendations U.74 and U.206. 7.5 The addres
40、s format shall be in accordance with Recommendation U.206. Following the answerback exchange, the calling telex subscriber should input the required videotex address. 7.6 Once the telex subscriber has entered the address, text input may commence. If, after a short delay, input has not commenced and
41、validation of the received videotex address is successful, the VTXCF should return the prompt GA TEXT, which can be preceded by other service codes (see Recommendation F.201). If the validation check fails, the VTXCF returns the service signal NP and clears. 7.7 completion of message deposit. An inp
42、ut message acknowledgement (MA) may be returned to the calling telex subscriber following 7.8 Recommendation U.206. The reactions to abnormal conditions arising during call Set-up or message deposit arc described in 4 Recommendation F.86 8 interworking in the videotex-to-telex direction for both typ
43、es, one-stage and two-stage VTXCFs 8.1 The videotex service user may send a message to a terminal of the international telex service in accordance with the principles contained in Recommendation F.300. The method of depositing a message on the part of the videotex service user for delivery to the in
44、ternational telex service is a national matter. 8.2 The VTXCF shall set up the connection to the required telex subscriber in accordance with normal telex procedures. Where validation of the telex recipient has been requested, the received telex answerback shall be verified in accordance with Recomm
45、endation U.75 to ensure correct delivery. Should the verification fail, the call attempt shall be deemed unsuccessful. This procedure should be applied at both the beginning and end of the call. 8.3 Having received the called telex answerback, the VTXCF shall forward its answerback to the called tel
46、ex subscriber in the case of a two-stage VTXCF. Where a one-stage selection procedure is used in the telex-to-videotex direction and the videotex subscriber has been assigned a telex number, the answerback to be forwarded should be that of the registered videotex address. The procedures for answerba
47、ck exchange shall comply with Recommendation S .23. 8.4 In the particular case of a two-stage VTXCF on the telex side, it is recommended that the VTXCF attach a herald to the text of the message to indicate the source of the message and the recall address. As a minimum, and as shown in Figure 3F.86,
48、 such a herald should include two fields, as follows: - - the VTXCF answerback. the recall address, preceded by the text FOR RECALL; Exchange of answerbacks between the VTXCF and the telex subscriber ,-.-.- HERALD FOR RECALL: Videotex address (Note) VTXCF answerback I ._._-_._- MESSAGE I Exchange o
49、answerbacks between the VTXCF and the telex subscriber T0101930-91 Note - The videotex address may be preceded by a sequence indicating the particular videotex service, e.g. BTX. FIGURE 3F.86 General layout of message sent from a videotex service user to a terminal of the international telex service via a two-stage VTXCF 8.5 conversion rules laid down in Recommendation S.18. The text of the message shall be forwarded to the called telex subscriber in accordance with the code Recommendation F.86 5 CCITT RECNN*F.Bb
