1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 3 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%2!0(9!,0(!“%4)#!,G0G04%,%2!0(G0G04%2-).!,%15)0-%.4#/$).G0G03#(%-%G0G053).G0G0).4%2.!4)/.!,4%,%2!0(G0G0!,0(!“%4G0G0.O G0 G0G0 )4! G9G0G04/!,/7G0G04(%G0G042!.3-)33)/.G0G0/(b) that there are advantages in es
2、tablishing an international standard for the transmission of capital and smallletters using International Telegraph Alphabet No. 2,unanimously declares the view(1) that the ability to transmit and print capital and small letters should be based on an extended use of ITA2;(2) that figure-shift (FS) a
3、nd letter-shift (LS) should be the only shift characters used;(3) that the number of shift characters introduced in the transmitted information should be minimized;(4) that the operating principles described in this Recommendation should apply.1 Scope1.1 Existing terminal equipment making use of ITA
4、2 may not discriminate between capital and small letterprinting. The decision to print in all capital or all small letters is a national matter and not affected by the received codecombination of ITA2.1.2 This Recommendation specifies a procedure whereby the terminal equipment may transmit informati
5、on toallow the receiving terminal to discriminate between capital and small letter printing.1.3 To assist understanding, Figure 1/S.2 shows diagrammatically the operating procedure of existing terminalequipment; Figure 2/S.2 shows the operating procedure specified in this Recommendation.2 Fascicle V
6、II.1 - Rec. S.22 Operating principles2.1 Operating modes2.1.1 The terminal equipment should operate in the following two modes:Mode 1 Transmission/reception of small letters, single capital letters and figures;Mode 2 Transmission/reception of capital letters and figures.The introduction of two modes
7、 of operation is to minimize the number of shift-characters transmitted.2.1.2 At the beginning of any transmission, it may normally be assumed, that the equipment concerned is in Mode 1,small letters. If an initialization sequence is required it should consist of a contiguous sequence of FS, LS, LSc
8、haracters.2.2 Selection within operating modes2.2.1 Where the terminal equipment is set to small letters in Mode 1 and a single capital letter is to be transmitted itshould be denoted as a capital letter by preceding the character transmission with a single LS character. Two LScharacters will be req
9、uired when the previously transmitted character was a figure. If the next character is a non-shiftcharacter then it will be transmitted/printed and the terminal equipment should be reverted to small letter operation. Ifthe next character is a shift character, the terminal equipment should be prepare
10、d to branch on the next character.2.2.2 In Mode 1 a single FS character should change the terminal equipment from small letter to figuretransmission/reception.Fascicle VII.1 - Rec. S.2 32.2.3 In Mode 2 a single FS or LS character should change the terminal equipment between figure and capital letter
11、operation respectively.2.3 Selection of operating mode2.3.1 Where the terminal equipment is set to Mode 1 and a group of three or more capital letters is to be transmitted,ignoring any non-letter characters separating them, then to improve efficiency of transmission, the terminal equipmentmay be set
12、 to Mode 2 (capital letters) and precede subsequent letter character transmission by a contiguous sequence ofa single FS and a single LS character.The receiving terminal equipment on detecting the FS, LS sequence should set the receiving terminal to Mode 2and print all following received letter char
13、acters as capital letters.2.3.2 Where the terminal is set to Mode 2 and small letter is to be transmitted the terminal equipment should be set toMode 1 and precede subsequent letter character transmission by a single LS character. Two LS characters will berequired where the previously transmitted ch
14、aracter was a figure.The receiving terminal equipment on detecting the one or two LS characters respectively should set thereceiving terminal to Mode 1 and print the following received letter character as a small letter.2.4 Manual terminal operation2.4.1 For manual operation the terminal should be p
15、rovided with, in addition to the normal shift key, a capital-lockkey or a shift-lock key or both.2.4.2 Where the terminal is set to Mode 1 the condition of the lock key should be examined for the groups of capitalletters. If the locked condition is detected the terminal should be set to Mode 2 and t
16、he subsequent letter charactertransmission preceded by the transmission of a contiguous sequence of a single FS and single LS character.2.4.3 Where the terminal is set to Mode 2 the shift key (single character) and the lock key (groups of characters)should be simultaneously examined. If neither the
17、shift key is operated nor the locked condition is detected, theterminal should be set to Mode 1 and the subsequent letter character transmission should be preceded by a single extraLS character.2.4.4 A start key to generate the initialization sequence may be provided.2.5 Automatic terminal operation
18、2.5.1 Where the terminal is set to Mode 1 and the next letter character to be transmitted is a capital letter, the nexttwo letter characters should be examined for capital letters, ignoring any non-letter characters separating them. If allthree letter characters are capital letters then the terminal
19、 should be set to Mode 2 and subsequent letter charactertransmission should be preceded by a contiguous sequence of a single FS and a single LS character. If the first lettercharacter to be transmitted is a capital letter but either, or both, of the two subsequent letter characters are not, the firs
20、tletter character should be transmitted preceded by a single extra LS character.2.5.2 Where the terminal is set to Mode 2 the next character to be transmitted should be examined and if it is a smallletter the terminal should be set to Mode 1.3 Transmission of WRU and answerback3.1 The coding and tra
21、nsmission of the WRU and answerback signals is not affected by this Recommendation.4 Provision of LS and FS functions4.1 It should be noted that in some circumstances it may be necessary to generate separate LS and FS characters fornational applications.5 National versions5.1 The use of ITA2 combina
22、tion No. 32, either in an escape sequence or as a single character, to enter a nationalalphabet is not affected by this Recommendation.5.2 It is possible to apply the principles described in this Recommendation to small and capital lettertransmission/printing of a national alphabet.5.3 Figure 3/S.2 of this Recommendation gives some guidance to Administrations, who may wish to includenational capital and small letters.4 Fascicle VII.1 - Rec. S.2
