1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 3 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%2!0(9!,0(!“%4)#!,G0G04%,%2!0(G0G04%2-).!,%15)0-%.4!.37%2G0G13G0“!#+G0G05.)4G0G03)-5,!4/23)45G134G0G0RecommendationG0G03 (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation S.17 was published in Fasci
2、cle VII.1 of the Blue Book. This file is an extract from theBlue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identical to the Blue Book version and copyright conditions remain unchanged (see below).2 In this
3、Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic ormechani
4、cal, including photocopying and microfilm, without permission in writing from the ITU.Fascicle VII.1 - Rec. S.17 1Recommendation S.17Fascicle VII.1 - Rec. S.17ANSWER-BACK UNIT SIMULATORS(former Recommendation V.13, Mar del Plata, 1968)1 The answer-back code must be released by a device capable of re
5、cognizing the Who are you? signal inInternational Telegraph Alphabet No. 2 (five-unit code). Hence, this device must keep in a store unit the figuressituation indicated by combination No. 30 received before combination No. 4 of this alphabet.2 In view of the procedure adopted for the use of the sequ
6、ence of four No. 19 combinations as the signal forpassage from the telex position to the data position in terminal equipment, the introduction of this sequence (four timescombination No. 19) in the 20 signals of the simulator answer-back code is to be avoided, since it is incompatible withthe proced
7、ure already adopted.Note It should be noted that, for the same reason of procedure, this four times combination No. 19 sequenceshould not be introduced in the answer-back code signals of a teleprinter associated with a manual or automatic call-transfer device.3 The composition of the signals of the
8、answer-back unit simulator can obviously be used for identification of thestation obtained by the station that requests the call. If the identification is negative, it is up to this calling station tointerrupt the unwanted connection.Note On the other hand, it was agreed that identification in the o
9、pposite direction could not be achieved in asimple way by the answer-back unit simulator, since the answer-back code to be checked in this direction is that of theopposite station, which is normally the one that has requested the connection.4 In a telex installation intended for data transmission and equipped with an answer-back unit simulator insteadof a teleprinter, the device for changeover from telex to data working by the passage of the sequence of fourcombinations No 19 must be automatic.5 The characteristics of the answer-back unit simulator should conform with Recommendation S.6.
