1、INTERNATIONAL TELECOMMUNICATION UNION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE TERMINAL EQUIPMENT AND PROTOCOLS FOR TELEMATIC SERVICES T.51 (09/92) LATIN BASED CODED CHARACTER SETS FOR TELEMATIC SERVICES Recommendation T.51 ITU-T RECMN*T-53 92 = 4862593 0607293 VbO m FO
2、REWORD The CCITT (the Internationai Telegraph and Telephone Consultative Committee) is a permanent organ of the International Telecommunication Union (KU). CCIT is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing tele
3、communications on a worldwide basis. The Plenary Assembly of CCIT which meets every four years, es;iblishes the topics for study and approves Recommendations prepared by its Study Groups. The approval of Recommendations by the members of CCI” between Plenary Assemblies is covered by the procedure la
4、id down in CCIT Resolution No. 2 (Melbourne, 1988). Recommendation revised T.51 was revised by Study Group VIII and was approved under the Resolu- tion No. 2 procedure on the 18 September 1992. CCIT NOTES 1) telecommunication administration and a recognized private operating agency. 2) In this Recom
5、mendation, the expression “Administration” is used for conciseness to indicate both a A list of abbreviations used in this Recommendation can be found in Annex C. O IT 1993 Ail rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, elecuonic or mechan
6、ical, including photocopying and microfh, without permission in writing from the ITU. Recommendation T.51 LATIN BASED CODED CHARACTER SETS FOR TELEMATIC SERVICES (Malaga-Torremolinos, 1984: Amended at Melbourne 1988; revised 1992) 1 scope 1.1 The CCITT, considering (a) the increasing interdependence
7、 of the various CCIT chanicter sets and coding schemes in various telematic services; (b) the introduction of new facilities such as code conversion and interworking between various telematic services: (c) the advantage of having a single unified repertoire and coding of Latin based character set in
8、 a Recommendation to act as a reference for the telematic services; (d) that Recommendations T.60lT.61 and T.100.101 define the character coding systems for teletex and videotex; (e) that Recommendation T.50 specifies the International Reference Version (JRV) of the 7-bit coded character set, provid
9、es the following Recommendation as a reference document towards which the Latin based portion of the coded character sets of telematic services should migrate and from which coded character subsets and elements of code extension mechanisms can be derived for individual telematic services. 1.2 This R
10、ecommendation specifies a primary set and a 96-character supplementary set of graphic characters. When various telematic services restrict their primary and supplementary sets to be respective subsets of those given in this Recommendation, it wiii be ensured that no code position in any of the speci
11、fied code tables is assigned more than one meaning within different telematic services. 94-character subsets of the supplementary code table can be found in Recommendations of specific telematic services, 1.3 graphic characters, to be used according to the code extension techniques specified. This R
12、ecommendation gives the escape sequences for designating the primary and supplementary sets of 1.4 Non-Latin based character sets are to be dealt with in Recommendation T.52. 1.5 This Recommendation describes those code extension mechanisms that are relevant to existing telematic services. Additiona
13、l mechanisms will be included in this Recommendation as the need for such is identified for one or more telematic services. The purpose of this Recommendation is to include an up-to-coding systems in various telematic services. 1.6 In this Recommendation 7-bit code tables are described which can be
14、used either in a 7-bit or in an 8-bit environment, with applicable code extension mechanisms that are given in other Recommendations specific to given telematic services. 1.7 Annex A). This Recommendation gives a unified superset of the repertoire of Latin based alphanumeric characters (see Recommen
15、dation T.51 (09/92) 1 ITU-T RECMN*Tm5L 92 48b2591 Ob07295 233 1.8 Annex B). This Recommendation gives a table of character and control sets used in CCIT telematic services (see 1.9 There is no conformance clause in this Recommendation specifying the mandatory and optional subsets of code extension m
16、echanisms and coded character sets. Conformance requirements will be the subject of other CCITT Recommendations specific to particular telematic services. 1.10 2 Graphic character sets The TSlStnng is defined in Annex D. A 2.1 Primary set 2.1.1 of the International Reference Version (IRV) of the 7-b
17、it coded character set of Recommendation T.50. The primary set of graphic characters specified in Figure 1iT.5 1 is identical with the set of graphic characters 2.1.2 The primary set is designated as Go by the sequence ESC 2/8 4/2. It can also be alternatively designated as G1, G2 or G3 by the seque
18、nces ESC u9 4/2, ESC 2/10 4/2 or ESC 2/l 1 4/2 respectively. See 3 for details on code extension techniques. Terminais used for telematic services which make reference to the 1988 version of Recommendation T.51 use, for the designation of the primary set as GO, the sequence ESC 2/8 4/0 and alternati
19、vely as G1, G2 and G3, the sequences ESC 2/9 4/0, ESC 2/10 4/0, ESC U1 1 4/0. 2.2 Supplementary set 2.2.1 The supplementary set of graphic characters is specified in Figure m.51. 2.2.2 identified. Unallocated code positions are subject to future standardization and will be allocated when a need for
20、such is 2.2.3 as G1 or G3 by the sequences ESC 2/13 5/2 or ESC U15 5/2 respectively. The supplementary set is designated as G2 by the sequence ESC 2/14 5/2. It can be alternatively designated Termmah used for telematic services which make reference to the 1988 version of Recommendation T.51 use, for
21、 the designation of the supplementary set as G2, the sequence ESC 2/10 6/2 and alternatively as GO, G1 and G3, the sequences ESC 2/8 6/2, ESC 2/!3 6/2, ESC Y1 1 6/2. 2.2.4 Notes on the primary and supplementary sets of graphic characters for Figures lL.51 and m.51 In the figures the number of the no
22、te being referred to is encircled. Note 1 - All the characters in column 4 of the supplementary set are non-spacing characters. They are all diacritical marks. Nore 2 - Cross-shaded code positions are reserved for future standardization by the CCIT. Note 3 - Terminals used for current “U-T defined t
23、elematic services may send and receive the codes 2/6 and U4 of the supplementary set for the NUMBER SIGN and DOLLAR SIGN, respectively. When receiving codes 2/3 and U4 from the primary set of graphic characters, terminais may interpret them as # and IX respectively. Future applications in telematic
24、services should code the NUMBER SIGN, CURRENCY SIGN and DOLLAR SIGN in accordance with Figures 1R.51 and U.T.51. Note 4 - Terminais used for -T defined telematic services should send only the codes 4/1 of the supplementary set followed by SPACE for a stand-alone grave accent, 4/3 of the supplementar
25、y set followed by SPACE for a stand-alone circumflex accent, and 414 of the supplementary set followed by SPACE for a stand-alone tilde. Whenever a telematic terminal is capable of receiving and interpreting codes 6/0,5/14 and 7/14 from the primary set of graphic characters, terminals shall interpre
26、t them as GRAVE, CIRCUMFLEX and TILDE respectively. 1 n Note 5 - This code position is reserved and shall not be used. 2 Recommendation T.51 (09/92) ITU-T RECNN*T.51 92 48b259L Ob07296 L7T Nute 6 - Current telematic services may interpret this as the non-spacing underline. The non-spacing underline
27、character is never used individually but always in combination with some other graphic character to represent the graphic rendition “underlined” for the associated character. The non-spacing underline character can be used in combination with any graphic character of the repertoire, including an acc
28、ented letter or an umlaut, or space. It is recommended to implement the “underline” function by means of tbe control function SGR(4) instead of the “non- spacing underline” graphic character. However, both must be correctly interpreted when received. b,O O O O 1 1 1 1 b6 O O 1 1 O O 1 1 b, O 1 O 1 O
29、 1 O 1 To81 16N Note - Notes to this figure are contained in 5 2.2.4. FGURE lfl.51 The primary set of graphic characters for telematic services (coded representation when invoked in columns 2-7 of the code table) Recommendation T.51 (09/92) 3 b, O 1 O 1 O 1 O Note - Notes to this figure are containe
30、d in 5 2.2.4. FIGURE m.51 “be supplementary set of graphic characters for telematic services (coded representation when invoked in mlumns 2-7 of the code table) 4 Recommendation T.51 (09/92) 3 Code extension technique 3.1 General 3.1.1 their invocation in the 7-bit set or 8-bit set in use. Such tech
31、niques are derived from IS0 Standard 2022. 3.1.2 This Recommendation describes only those code extension techniques currently specified for existing telematic services. Additional techniques will be further incorporated as they are identified for use in one or more telematic services. Code extension
32、 techniques are required for the designation of various graphic or control character sets and 3.2 Definitions For the purpose of code extension techniques given in this Recommendation, the following definitions apply. 3.2.1 bit combination An ordered set of bits used for the representation of charac
33、tem. 3.2.2 byte A bit string that is operated upon as a unit and the size of which is independent of redundancy or framing techniques. 3.2.3 character A member of a set of elements used for the organization, control or representation of data. 3.2.4 coded character set; code A set of unambiguous rule
34、s that establishes a character set and the one-to-one relationship between the characters of the set and their bit combinations. 3.2.5 code extension The techniques for the encoding of characters that are not included in the character set of a given code. 3.2.6 codetable A table showing the characte
35、r allocated to each bit combination in a code. 3.2.7 control character A control function the coded representation of which consists of a single bit combination. 3.2.8 control function An action that affects the recording, processing, transmission or interpretation of data and that has a coded repre
36、sentation consisting of one or more bit combinations. 3.2.9 to designate To identify a set of characters that are to be represented, in some cases immediately and in others on the occurrence of a further control function, in a prescribed manner. 3.2.10 environment The characteristic that identifies
37、the number of bits used to represent a character in a data processing or data communication system or in part of such a system. Recommendation T.51 (09/92) 5 V8625L Ob07239 389 W 3.2.1 1 escape sequence A bit string that is used for control purposes in code extension procedures and that consists of
38、two or more bit combinations. The first of these bit combinations represents the character ESCAPE (111 1). 3.2.12 final character The character the bit combination of which terminates an escape sequence. 3.2.13 graphic character A character, other than a control function, that has a visual represent
39、ation normally handwritten, printed or displayed. 3.2.14 intermediate character A character the bit combination of which occurs between that of the ESCAPE character and that of the Final character in an escape sequence consisting of more than two bit combinations. 3.2.15 to invoke To cause a designa
40、ted set of characters to be represented by the prescribed bit combinations whenever those bit combinations occur, until an appropriate code extension function occurs. 3.2.16 position That part of a code table identified by its column and row coordinates. 3.2.17 to represent a) to use a prescribed bi
41、t combination with the meaning of a character in a set of characters that has been designated and invoked; or to use an escape sequence with the meaning of an additional control function. b) 3.218 Repertoire A specified set of characters that are represented by the combination of a coded character s
42、et. A 3.3 Code extension facilities These are depicted io Figure 3.51 for the 7-bit environment and Figure 4f.51 for the 8-bit environment. They include the following functions: a) designation and invocation of control sets CO and C1 by means of the relevant escape sequences given in Q 3.4; b) c) de
43、signation of a graphic character set Go by means of the relevant escape sequence given in Q 3.4; designation of up to three additional G-sets called GI, G2 and G3 by means of the relevant escape sequences given in 8 3.4; d) invocation of the designated graphic sets, by means of locking andor non-loc
44、king shift functions, given in 6 3.5; e) designation and invocation of a complete code by means of the relevant escape sequence given in 4 3.4. 3.4 Types of character sets There are a number of different types of control and graphic character sets that can be designated and invoked for use in the 7-
45、bit or ESC 2/4 411; ESC 2/4 4/2. 10 Recommendation T.51 (09/92) ITU-T RECMN*T=SL 92 4862593 0607304 076 W A set Go G1 G2 G3 TABLE 4tT.5 1 Allocation of shift functions to the graphic character sets to be invoked Locking-shift functions Non-locking shift functions Columns 2 to 7 of 7-bit or 8-bit cod
46、e Columns 10 to 15 of 8-bit code Columns 2 to 7 of 7-bit or 8bit code - SI(7-bit), LSO(8-bit) - S0(7-bit), Ls l(8- bit) LSlR - Ls2 LS2R SS2 Ls3 LS3R ss3 TABLE 5tT.51 Coding for sh functions _ Shift functions Single-shift two Single-shift three Shift in SI(7-bit), locking-shift zero Shift out S0(7-bi
47、t), locking-shift one Locking-shift one right Locking-shift two Locking-shift two right Locking-shift three Locking-shift three right ss2 ss3 LSO(8-bit) LSl(8-bit) LSlR LS2 LS2R Ls3 LS3R coding 1 I9 1/13 0115 0114 ESC 7/14 ESC 6/14 ESC 7/13 ESC 6/15 ESC 7/12 Recommendation T.51 (09192) 11 ANNEX A (t
48、o Recommendation T.5 i) Superset of the repertoire of the Latin based character set A. 1 This annex contains a unified superset of the repertoire of Latin based alphanumeric graphic characters. Each graphic character is identified by the identification system (seeA.2). A A.2 Identification system A
49、system was developed that allows for the identification and description of each graphic character or control function. The system is shown in Figure A- l.5 1. Each identifier consists of two letters and two digits. The first letter indicates the alphabet, the language, etc. The second letter indicates the letter of an alphabet or, in the case of a non-alphabetic graphic character or a control function, the group of characters or control functions. The first digit indicates whether the letter in the second position is an accente
