1、ITU-T RECMN*S.L, 93 W 48b2591 05903L,3 72T = INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU TELEGRAPHY ALPHABETICAL TELEGRAPH TERMINAL EQUIPMENT s.4 (03/9 3) SPECIAL USE OF CERTAIN CHARACTERS OF THE INTERNATIONAL TELEGRAPH ALPHABET No. 2 ITU-T Recommendat
2、ion S.4 (Previously “CCITT Recommendation”) ITU-T RECMN*S-4 73 4862591 05903V4 bbb FOREWORD The ITU 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 an
3、d issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. 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 Recommendation
4、s on these topics. ITU-T Recommendation S.4 was revised 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
5、1993. In its place, the ITU Telecommunication Standardization 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 Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector.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
6、 in the text to references containing the acronyms “CCITT, 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 reco
7、gnized operating agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a O ITU 1994 Ali 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 micr
8、ofilm, without permission in writing from the ITU. ITU-T RECMN+S.Y 93 m YBb259L 0590345 5T2 m Recommendation S.4 SPECIAL USE OF CERTAIN CHARACTERS OF THE INTERNATIONAL TELEGRAPH ALPHABET No. 2 Iformer CCIT Recommendations C.7, C.8 and C.12; modified at New Delhi, 1960, Geneva, 1964,1972,1976,1980, M
9、alaga-Torremolinos, 1984, Melbourne, 1988, and Helsinki, 1993) 1 Sequences of combinations used for special purposes As quoted in Recommendations F.l, F.30, R.79, S.ll, S.15, U.21, U.22, U.43, U.44 and U.46, certain sequences of combinations from the International Telegraph Alphabet No. 2 are devote
10、d to special purposes (see Table 1) and they should not be used for other purposes when the equipment on such networks introduces special facilities for which these sequences are reserved. NOTE - The sequences of secondaries of these combinations - although they are not to be used for the purposes d
11、evoted to these sequences - are subject to the same restrictions in use, unless otherwise indicated, the equipment having to recognize only the sequence of combinations. ZCZC (combination Nos. 26, 3, 26, 3), start-of-message signal in retransmission systems using perforated tape or equivalent device
12、s; + + + + (combination Nos. 26,26,26,26), end-of-input signal or end of transaction signal; NNNN (combination Nos. 14, 14, 14, 14), end-of-message signal, a switching signal in switching systems using perforated tape or equivalent devices for retransmission. In the store-and-forward and interworkin
13、g environment this signal indicates a follow-on message or call. This sequence is also used for restoring the waiting signal device in accordance with Recommendation U.22; CCCC (combination Nos. 3, 3, 3, 3), for switching into circuit, by remote control, a reperforator (or equivalent device); SSSS (
14、combination Nos. 19, 19, 19, 19), for switching into circuit data transmission equipment, in accordance with Recommendation S. 15. In addition, this sequence may be used for switching into circuit, by remote control, equipment operating with a nationally standardized alphabet; FFFF (combination Nos
15、6, 6, 6, 6), for switching out of circuit, by remote control, a reperforator (or equivalent device); KKKK (combination Nos. 11, 11, 11, li), ready-for-test signal, for automatic tests of transmission quality, in accordance with Recommendation R.79; KLKL (combination Nos. 11, 12, 11, 12), for switchi
16、ng into circuit, by remote control, a reader (or equivalent device); XXXXX (combination Nos. 24, 24, 24, 24, 24), error signal when using automatic error correction devices (see Recommendation F. 1); the line-feed signal (combination No. 28) followed by four carriage-return signals (combination No.
17、27) for the operator-recall signal on a telex connection made over a radiotelegraph circuit (see Recommendation U.21); HHHH (combination Nos. 8, 8, 8, 8), to prevent transmission of the delay signals described in Recommendation U.22 made up from combination No. 32 as described in clause 2 below; TTT
18、 . (combination Nos. 20, 20, 20, .), to stop transmission from the distant terminal as described in Recommendations F.60 and U.46; SZ . (combination Nos. 30, 10, .), one or more combinations No. 10 in figure-shift after the call is established could trigger the transmission of a “conversation imposs
19、ible” “CI” sequence of signals and/or a prerecorded message from distant terminal (it should be noted that the combination No. 10 in figure- shift could also be used to attract the operators attention). Recommendation S.4 (03/93 1 ITU-T RECMN*S.4 93 = 4862591 0590346 439 14) MMMM (combination Nos. 1
20、3, 13, 13, 13), during a broadcast call, to signal the desire of the calling party to know those parties who cleared prematurely. See Recommendations U.44 and S.20. NOTE - This sequence is to be recognized in letter shift mode only. A minimum of 4 Ms would clear a telex broadcast call, usage of a fi
21、fth or more Ms is a national matter. 15) LLLL (combination Nos. 12, 12, 12, 12), to signal the desire of the calling party to terminate the present call and to make a follow-on call as described in Recommendation U.43. Usage of a fifth or more Ls is a national matter. This combination should be reco
22、gnized in letter shift mode only. 2 Use of combination No. 32 In addition to the purposes described in Recommendation S.l, combination No. 32 can be used for the following purposes: 2.1 error-correcting device is controlling a repetition. Combination No. 32, repeated at intervals of 1.2 seconds, can
23、 be used as a delay signal to indicate that the 2.2 storage device is not yet empty. Combination No. 32, repeated at intervals of 5 seconds, can be used as a delay signal to indicate that the 2.3 teleprinters. NOTE - Clause 1, 10) and 1,ll) as well as 2.1 and 2.2 apply directly only to start-stop eq
24、uipment operating at 50 bauds, since this is the modulation rate for telex. However, in the event of suitable synchronous error-correcting systems being used for the interconnection of start-stop circuits that operate at higher modulation rates, similar facilities might be desirable and could be pro
25、vided by similar means. The reception of combination No. 32 shall not cause any spacing of the paper on tape-printing or page-printing 2 Recommendation S.4 (03/93) ITU-T RECMN*S.4 93 m 4862573 0590347 375 m Purpose of sequence Start of message Suppression of delay signals End of input End of message
26、 Connection of reperforator (or equivalent device) Disconnection at distance of reperforator (or equivalent device) Connection of data equipment Ready for test Connection of a reader (or equivalent device) Error signal TABLE US.4 The use of various sequences of combinations for special purpose Seque
27、nceof combinations recommanded 26 3 26 3 8 888 26 26 26 26 14 14 14 14 6666 19 19 19 19 11 11 11 11 11 12 Il 12 24 24 24 24 24 Point-to-point operation Not ordinarily required Not required on public systems (delay signal not envisaged) Not ordinarily required Not ordinarily required Could be useful
28、for special purposes; requires special equipment at point of reception Could be useful for special purposes Could be useful for special purposes Could be useful for special purposes Could be useful for special purposes; requires special equipment at point of reception Method of operation Through swi
29、tching (without message storage) Could be useful in special cases Required for some types of message (e.g. cypher) when routed over synchronous error-corrected radiotelegraph channels Could be useful in special cases Required only when it is necessary positively to reconnect delay signal facility af
30、ter use of suppression of delay signals facility Could be useful for special purposes; requires special equipment at point of reception Used for switching into data transmission equipment in association with telex networks Used for automatic maintenance of telex circuits Could be useful for special
31、purposes Used for automatic correction of operator errors Message switching (including storage) Required in most systems Not required (delay signal not envisaged) Could be useful in special cases Essential in most systems to separate individual message at relay centres and to control message switchi
32、ng Not normally used (as storage is incorporated in the system): could be used for connection and disconnection of a supplementary storage device Not normally used Not required Not normally used Not required IWU/SFU Not normally used Not required Used in some cases (e.g. U.201 + U.206) Used in most
33、cases to signal a follow-on call or message Not normally used Not used Not used Not normally used Not normally used Recommendation S.4 (03/93) 3 Purpose of sequence Interruption of automatic transmission Triggering a pre-recorded message Information about premature clearing in a broadcasting call Fo
34、llowing-on call TABLE US.4 (conf.) The use of various sequences of combinations for special purpose Sequence of combinations recommanded 20 20 20 . 10 10 10 . 13 13 13 13 12 12 12 12 Point- to-point operation Required Not required Not required Not required Method of operation Through switching (without message storage) Required Required Required Required Message switching (including storage) Required Not required Required Required IWU/SFW Required Not normally used Not normally used Not required 4 Recommendation S.4 (03D3)
