1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 3 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%2!0(9!,0(!“%4)#!,G0G04%,%2!0(G0G04%2-).!,%15)0-%.453%G0G0/.G0G02!$)/G0G0#)2#5)43/ amended at New Delhi, 1960,Geneva, 1964, Mar del Plata, 1968, and Geneva, 1972)(This Recommendation corresponds to CCIR Re
2、commendation 342-2, New Delhi, 1970)The CCITT,considering(a) that it is essential to be able to interconnect terminal start-stop apparatus employing International TelegraphAlphabet No. 2 by means of radiotelegraph circuits;(h) that radiotelegraph circuits are required to operate under varying condit
3、ions of radio propagation,atmospheric noise and interference, which introduce varying degrees of distortion that may at times exceed the marginof the receiving apparatus;(c) that, in consequence, the transmission of 5-unit code signals over radio circuits is liable to errors and thatsuch errors are
4、not automatically detectable by the receiving apparatus;(d) that an effective means of reducing the number of wrongly printed characters is the use of codes permittingthe correction of errors by detecting the errors and automatically causing repetition;(e) that the method using synchronous transmiss
5、ion and automatic repetition (ARQ) is now well proven;(f) that it is desirable to permit the correct phase to be established automatically on setting up a circuit;(g) that certain circumstances can occur that result in a loss of the correct phase relationship between areceivedsignal and the receivin
6、g apparatus;(h) that it is desirable to permit the correct phase relationship to be re-established automatically after such aloss, without causing errors;(i) that to avoid misrouting of traffic, it is essential to prevent phasing to a signal that has been unintentionallyinverted;(j) that in certain
7、cases there is a need to subdivide one or more channels in order to provide a number ofservices at a proportionately reduced character rate;(k) that the method of automatically achieving the correct phase relationship between the received signal andthe sub-channelling apparatus should be an integral
8、 part of the phasing process;(l) that compatibility with existing equipment designed in accordance with the former Recommendation S.13(New Delhi, 1960) is a requirement,unanimously declares the view(1) that, when the direct use of a 5-unit code on a radio circuit gives an intolerable error rate and
9、there is areturn circuit, a 7-unit ARQ system using International Telegraph Alphabet No. 3 should be used;(2) when automatic phasing of such a system is required, the system described in the Annex should be adoptedas a preferred system;(3) that equipment, designed in accordance with (2) above, shoul
10、d be provided with switching, to permitoperation with equipment designed in accordance with Recommendation S.13, New Delhi, 1960;(4) that the start-stop sections of the receiving and transmitting portions of the radiotelegraph circuit, points Xand Y in Figure 1/S.12, should satisfy the conditions of
11、 Recommendations S.3 and S.12. In conformity withRecommendation S.12, the aggregate modulation rate for a 2-channel time-division multiplex system will be 96 baudsand for a 4-channel system will be 192 bauds;(5) that if such systems are used in establishing telex connections, the signalling position
12、 should conform to thearrangements shown in Recommendations U. 11 1, U.20 2, U.21 3, U.22 4.2 Fascicle VII.1 - Rec. S.13(5.1) For circuits on switched telegraph networks, the conditions of Recommendation U.20 2 should apply.In this usage the polarity retransmitted by the terminal of the radio channe
13、l towards the start-stop section of the circuitduring a repetition cycle shall be start polarity when the circuit is in the “free line” condition and stop polarity when thecircuit is in the “busy circuit” condition.(5.2) For point-to-point circuits, Administrations may adopt, at the terminal equipme
14、nt under theirjurisdiction, their own method of stopping and starting the motors of the receiving machines, based onRecommendation S.7. Signal should normally be transmitted to indicate the idle circuit condition. However, forsignalling purposes, the signals and may be employed.ANNEX A(to Recommenda
15、tion S.13)A.1 Conversion tableA.1.1 Table A-1/S.13 shows the correspondence between International Telegraph Alphabet No. 3 used in 7-unit ARQsystems and International Telegraph Alphabet No. 2 (defined in the Recommendation cited in 5).A.2 Repetition cyclesA.2.1 Four characters for normal circuits th
16、at are not subject to excessive propagation time. The cycle shouldcomprise one signal repetition and three stored characters.A.2.2 Eight characters on circuits for which the four-character repetition cycle is inadequate. The cycle shouldcomprise one signal repetition, three signals and four stored c
17、haracters, or one signal repetition and seven storedcharacters.A.3 Channel arrangementA.3.1 Channel AA.3.1.1 For equipments employing a 4-character repetition cycle: one character inverted followed by threecharacters erect see (a) of Figure A-1/S.13.A.3.1.2 For equipments employing an 8-character re
18、petition cycle: one character inverted followed by sevencharacters erect see (a) of Figure A-2/S.13.A.3.2 Channel BA.3.2.1 For equipments employing a 4-character repetition cycle: one character erect followed by three charactersinverted see (b) of Figure A-1/S.13.A.3.2.2 For equipments employing an
19、8-character repetition cycle: one character erect followed by seven charactersinverted see (b) of Figure A-2/S.13.A.3.3 Channel CAs for Channel B see (c) of Figures A-1/S.13 and A-2/S.13.A.3.4 Channel DAs for Channel A see (d) of Figures A-1/S.13 and A-2/S.13.Fascicle VII.1 - Rec. S.13 3TABLE A- 1 /
20、S.13Code conversion tableCombination No.in InternationalTelegraphAlphabet No. 2LettercaseFigurecaseCode in International TelegraphAlphabet No. 2(see Note 1)Code in InternationalTelegraphAlphabet No. 3(see Note 1)12345ABCDE?:Note 23ZZAAAZAAZZAZZZAZAAZAZAAAAAAZZAZAAAZZAAZZAAZZAAAAZZZAAAZZZAAA678910FGH
21、IJNote 28Note 2ZAZZAAZAZZAAZAZAZZAAZZAZAAAZAAZZZZAAAAZZAZAAZAZZZAAAAAZAAAZZ111213141516171819202122232425KLMNOPQRSTUVWXY().,901457=2/6ZZZZAAZAAZAAZZZAAZZAAAAZZAZZAZZZZAZAZAZAZAZAAAAAAZZZZAAAZZZZZZAAZZAZZZZAZAZAAAZAZZZZAAAZAZAZAAAZZAZAZAAZAAAZZAZAAZAZAAAAZZAZZZAAZAAAZAZAZAZAAAZAZAZZAAZAZAAZAAZAZAAZAZ
22、AAZAZZAAAZAZAZ26272829303132Z +Carriage-returnLine-feedLetter-shiftFigure-shiftSpaceNot normally usedSignal repetitionSignal Signal ZAAAZAAAZAAZAAAZZZZZZZAZZAAZAAAAAAA(permanent A polarity)(permanent Z polarity)AZZAAAZZAAAAZZZAZZAAAAAAZZZAAZAAZZAZZAZAAAAAAAZZZAZZAZAAAZAZAAZAZAZZAANote 1 - Symbols A
23、and Z have the meanings defined in 6.Note 2 - See Recommendation S.4.A.3.5 Order of transmissionA.3.5.1 Characters of Channels A and B are transmitted consecutively see (e) of Figures A-1/S.13 and A-2/S.13.A.3.5.2 Elements of Channel C are interleaved with those of Channel A see (g) of Figures A-1/S
24、.13 andA-2/S.13.A.3.5.3 Elements of Channel D are interleaved with those of Channel B see (g) of Figures A-1/S.13 andA-2/ S.13.A.3.5.4 In the aggregate signal, A elements precede those of C, and B elements precede those of D see (g) ofFigures A-1/S.13 and A-2/S.13.4 Fascicle VII.1 - Rec. S.13A.3.5.5
25、 The first erect character on A, transmitted after the inverted character on A, is followed by the erectcharacter on B see (e) of Figures A-1/S.13 and A-2/S.13.A.3.5.6 The erect character on C is followed by the inverted character on D see (f) of Figures A-1/S.13 andA-2/S.13.A.3.5.7 The inverted cha
26、racter on A is element-interleaved with the erect character on C see (g) ofFigures A-1/S.13 and A-2/S.13.A.4 Subchannel arrangementA.4.1 The character transmission rate of the fundamental subchannel should be a quarter of the standard characterrate.A.4.2 Subchannels should be numbered 1, 2, 3 and 4
27、consecutively.A.4.3 Where a 4-character repetition cycle is used, subchannel 1 should be that subchannel which has opposite keyingpolarity to the other three subchannels of the same main channel see (a), (b), (c) and (d) of Figure A-3/S.13. When an8-character repetition cycle is used, subchannel 1 s
28、hould be that subchannel which has alternately erect and invertedkeying polarity see (e), (f), (g) and (h) of Figure A-3/S.13.A.4.4 When subchannels of half-character rate, or three-quarter-character rate are required, combinations of thefundamental subchannels should be arranged as shown in Table A
29、-2/S.13.A.5 Designation of aggregate signalTo assist in identifying the signal condition when applying the aggregate telegraph signal to modulate the radiochannel, the designation for the aggregate signal should be used as shown in Table A-3/S.13.A.6 DiagramsAs a result of the characteristics specif
30、ied in A.2, A.3 and A.4 above, the transmission of characters will beas shown in Figures A-1/S.13, A-2/S.13 and A-3/S.13.A.7 Automatic phasingA.7.1 Automatic phasing should normally be used. It should be initiated either:a) after a waiting period during which cycling due to the receipt of errors has
31、 occurred continuously on bothchannels on a 2-channel system, or on at least two main channels of a 4-channel system;b) after equal counts of A and Z elements have been made over at least two consecutive system cycles whilstcontinuous cycling due to the receipt of errors is occurring on all main cha
32、nnels.A.7.2 When the slave station is phasing, it should transmit in each channel, in place of the signal repetition, a7-element signal in which all seven elements are of the same polarity, all other characters in the repetition cycle beingtransmitted unchanged.Fascicle VII.1 - Rec. S.13 5 6 Fascicl
33、e VII.1 - Rec. S.13 Fascicle VII.1 - Rec. S.13 7 8 Fascicle VII.1 - Rec. S.13TABLE A-2/S.13Proportion of full-channelcharacter rateCombination offundamental subchannels(1) quarter(2) quarter(3) halfNo. 1No. 3Nos. 2 and 4(1) half(2) halfNos. 1 and 3Nos. 2 and 4(1) quarter(2) three-quartersNo. 1Nos. 2
34、, 3 and 4TABLE A-3/S.13Seven-unit codeconditionAggregate signal conditionErect character Inverted characterAZBYYBNote - With a frequency shift system, the higher frequency should correspond to aggregate condition B and the lowerfrequency should correspond to aggregate condition Y.References1 CCITT R
35、ecommendation Telex and gentex signalling on intercontinental circuits used for intercontinentalautomatic transit traffic (Type C signalling), Rec. U.11.2 CCITT Recommendation Telex and gentex signalling on radio channels (synchronous 7-unit systems affordingerror correction by automatic repetition)
36、, Rec. U.20.3 CCITT Recommendation Operator recall on a telex call set up on radiotelegraph circuit, Rec. U.21.4 CCITT Recommendation Signals indicating delay in transmission on calls set up by means of synchronoussystems with automatic error correction by repetition, Rec. U.22.5 CCITT Recommendation Operational provisions for the international public telegram service, Rec. F.1, C.8.6 CCITT Definition: Position A; position Z, Vol. X, Fascicle X.1 (Terms and Definitions).
