ITU-T R 44-1988 6-UNIT SYNCHRONOUS TIME-DIVISION 2-3-CHANNEL MULTIPLEX TELEGRAPH SYSTEM FOR USE OVER FMVFT CHANNELS SPACED AT 120 Hz FOR CONNECTION TO STANDARDIZED TELEPRINTER NETW.pdf

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1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 2 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%2!0(94%,%2!0(G0G042!.3-)33)/.G135.)4G0G039.#(2/./53G0G04)-%G13$)6)3)/.G13 G13#(!%,G0G0-5,4)0,%8G0G04%,%2!0(3934%-G0G0(b) that such an increase may be of interest in the case of long submarine cables of th

2、e telephone type in viewof the resulting economies;(c) that, in addition to the signals of International Telegraph Alphabet No. 2, transmission of the selection andsupervisory signals is essential when incorporating the telegraph channels thus provided into the internationalswitching network;(d) tha

3、t it is desirable to allow for the provision of half-rate and quarter-rate channels;(e) that correct phase-relationship should be established and also maintained automatically;(f) that systems using 5- and 6-unit codes have been proposed,unanimously declares the viewthat, where the synchronous multi

4、plex system uses a 6-unit binary code, the equipment should be constructed tothe following standards (Administrations may of course by mutual agreement use a different system with a 5-unit codesuch as that described in 1).1 Telegraph modulation1.1 The character period should be 145 5/6 ms.1.2 The mu

5、ltiplexing should provide for the derivation of either 2 or 3 time-division channels from each voice-frequency telegraph (VFT) channel. The aggregate modulation rate will be 82 2/7 bauds for a 2-channel multiplex and123 3/7 bauds for a 3-channel multiplex. Generally it is found that VFT systems conf

6、orming to Recommendation R.35will operate satisfactorily at 82 2/7 bauds, but to ensure satisfactory operation at 123 3/7 bauds, it is necessary toemploy characteristic distortion compensation (CDC) at the receiving end of the VFT channel.1.3 The time derived channels shall be element interleaved to

7、 form the aggregate signal.2 Connection to start-stop circuits2.1 The channel inputs shall be capable of accepting signals from start-stop equipment conforming toRecommendation S.3 2 (except 1.6 of S.3). The channel output should be start-stop with a modulation rate of50 bauds. Standards of performa

8、nce are given in 9 below.3 Alphabet3.1 Combinations 1 to 31 of the 5-unit International Telegraph Alphabet No. 2 shall each be preceded by anA-condition element, while the continuous start and continuous stop conditions shall utilize the 6-unit combinationsAAAAAA and ZZZZZZ respectively. The remaini

9、ng combination No. 32 shall be preceded by a Z element.3.2 The alphabet should be as shown in Annex A.2 Fascicle VII.1 - Rec. R.444 Grouping of multiplex systems4.1 A common phasing control can be used for a number of multiplex systems carried by different channels of thesame VFT system. A group of

10、multiplexes shall comprise a maximum of six systems. Some time-derived channels shallbe capable of being further divided to provide sub-channels. The various channels should be identified by a figuredenoting the number of the multiplex system within the group of six, i.e. 1-6 followed by a letter de

11、noting the channelwithin that system, i.e. A, B or C. Thus the complete channel numbering will be as follows:Multiplex system/channel1A, 2A, 3A, 4A ,5A, 6A2B, 3B, 4B, 5B, 6B 1C, 2C, 3C, 4C, 5C, 6Cfull rate,(1B is not available as a full-rate channel see 7 below.)4.2 Each A channel should be full cha

12、racter rate only.4.3 Each B channel should be capable of full character rate and subdivision (except 1B, which is permanentlysubdivided).4.4 The full-rate channels A and B in the case of 2-channel multiplexing, or A, B and C in the case of 3-channel,should be multiplexed on an element-interleaved ba

13、sis in the following sequence:Al, B1, A2, B2, etc. for 2-channel operation (where Al is the first element of channel A etc.);Al, B1, C1, A2, B2, C2, etc. for 3-channel operation.5 Subdivision of channels5.1 All full character-rate channels B (except B1) and C should be capable of subdivision into qu

14、arter character-rate channels, and into multiples of quarter-rate, i.e. one half-rate, using two quarter-rate channels. (Althoughtheoretically three-quarter rate channels could be provided, controlled by means of pulses from the multiplexequipment, provision of this facility is not recommended.)5.2

15、The sub-channels should be identified basically in the same manner as the full-rate channels with the additionof a numeral denoting the quarter-rate channel, i.e. 1-4. In the case of half-rate channels, the numbers of the twoquarter-rate channels used for it should be shown, i.e. 1/3 or 2/4. Thus th

16、e complete sub-channel numbering will be asfollows:Multiplex system/channel/sub-channel1B1, 2B1, 3B1, 4B1, 5B1, 6B1. 1C1, 2C1, 3C1, 4C1, 5C1, 6C1 1B2, 2B2, 3B2, 4B2, 5B2, 6B2. 1C2, 2C2, 3C2, 4C2, 5C2, 6C2 1B3, 2B3, 3B3, 4B3, 5B3, 6B3. 1C3, 2C3, 3C3, 4C3, 5C3, 6C3- , 2B4, 3B4, 4B4, 5B4, 6B4. 1C4, 2C4

17、, 3C4, 4C4, 5C4, 6C4quarter rate(1B4, phasing control only)1B1 / 3, 2B1 / 3, 3B1 / 3, 4B1 / 3, 5B1 / 3, 6B1 / 3 - , 2B2 / 4, 3B2 / 4, 4B2 / 4, 5B2 / 4, 6B2 / 4 (1B2 / 4 not available) 1C1/ 3, 2C1/ 3, 3C1 / 3, 4C1 / 3, 5C1 / 3, 6C1 / 31C2 / 4, 2C2 / 4, 3C2 / 4, 4C2 / 4, 5C2 / 4, 6C2 / 4 half rate5.3

18、The sub-channels 1, 2, 3 and 4 shall be operated in the following character sequence:A B1 A B2 A B3 A B4 A B1, etc. for 2-channel operation,A B1 C1 A B2 C2 A B3 C3 A B4 C4 A B1 C1, etc. for a 3-channel operation.Fascicle VII.1 - Rec. R.44 35.4 All the sub-channels shall be transmitted with the same

19、polarity except those of channel 1B, which should beinverted.6 Transposition pattern6.1 To avoid inadvertent cross-connections between channels when the system is out of phase, elementtranspositions should be allocated to the channels and sub-channels as follows:Channel A 1 2 3 4 5 6Channel B 1 3 2

20、4 5 6Channel C 1 2 4 3 5 6sub - channel 1Channel A 1 2 3 5 4 6Channel B 1 2 3 4 6 5Channel C 1 4 3 2 5 6sub - channel 2Channel A 1 2 5 4 3 6Channel B 1 2 3 6 5 4Channel C 1 5 3 4 2 6sub - channel 3Channel A 1 2 6 4 5 3Channel B 1 6 3 4 5 2Channel C 1 6 5 4 3 2sub - channel 46.2 Full character-rate a

21、nd half character-rate channels should take that sequence which is allocated to their lowest-numbered sub-channel, i.e. a full character-rate channel should take the sequence for its sub-channel 1, a half character-rate sub-channel using sub-channels 1 and 3 should take the sequence for its sub-chan

22、nel 1, and a half character-ratesub-channel using sub-channels 2 and 4 should take the sequence for its sub-channel 2.6.3 The element transpositions shall be carried out in the permanent wiring to the start-stop input and output unitsso that each of these units may be used in any position without al

23、teration.7 Phasing7.1 Provision should be made for:a) automatic phasing, automatically initiated (normal working condition);b) automatic phasing, manually initiated;c) manual phasing.7.2 One quarter-rate channel of the group (1 B4) should be permanently allocated for phasing control purposes, andsho

24、uld continuously send the character ZZAAZZ (the phasing signal).7.3 Automatic initiation of phasing should occur when three successive phasing signals have not been recognized.7.4 Automatic phasing may be in steps of one element per expected reception of the phasing signal, i.e. every fourtransmissi

25、on cycles (583 ms), or alternatively a method that will carry out rephasing in one operation thus reducing thetime spent on phasing. Phasing shall automatically cease when the phasing signal is recognized on the phasing sub-channel receiving unit.7.5 Visual indication of the correct reception of the

26、 phasing signal should be given.8 Telex and gentex signalling8.1 The multiplex equipment should be capable of accepting CCITT types A, B and C signals and shall sensiblyreproduce them with minimum delay or change.8.2 It is especially desirable to transmit the signals used for calling and call confir

27、mation with the minimum delayin order to minimize the probability of simultaneous seizure from both ends where circuits are used for both-wayworking.4 Fascicle VII.1 - Rec. R.448.3 To meet this requirement of minimum delay it is necessary that both the normal character storage inherent in arandom ar

28、rival system should be bypassed during the free-line condition and the incoming signal from telex should beinspected at the most frequent intervals possible, with element interleaving between channels. Thus effectively the lineinput circuit is connected directly to the multiplex aggregate, and is in

29、spected at intervals of 24 11/36 ms causing anelement of this length and input polarity to be transmitted over the aggregate signal path. At the receiving end thiselement would be distributed to the appropriate channel and produce an element of like polarity at the output. Theresult of this is to tr

30、ansmit elements of 24 11/36 ms of a polarity determined by the channel input.8.4 With the character store bypassed in this way the transmission of pulse signals, which may be signalling ordialling, during the setting up of a telex call is also permitted. The character store must, however, be switche

31、d into useprior to the transmission of teleprinter characters whether these are signalling or traffic.8.5 The method of switching start-stop stores into the connection depends on the type of signalling and it may varywith the direction of calling. Normally each direction of signalling may be conside

32、red separately and the stores can beswitched into the connection within a period less than one character length of the inversion to stop polaritys beingrecognized, but with calls to type B dial selection systems switching must be deferred until such conversion hasoccurred on both signalling paths.8.

33、6 It seems desirable to guard against reproduction of short spurious pulses on the input line as full elements.Pulses of up to 8-10 ms should therefore be rejected. Thus pulses would result as follows:Input to system Multiplex aggregate Output from system0-9 ( 1) ms of eitherpolarity9 ( 1)-33 11/36

34、ms33 11/36-57 11/18 msNo pulse1 element (24 11/36 ms)2 elements (48 11/18 ms)No pulseFor A polarity 45 msFor Z polarity 33 msBoth polarities 48 11/18 ms8.7 An alternative method of producing pulses, as follows, would be acceptable:0-9 ( 1) ms9 ( 1)-24 11/36 ms24 11/36-48 11/18 ms48 11/18-72 11/12 ms

35、No pulse1 element (24 11/36 ms)1 element (24 11/36 ms)or 2 elements (48 11/18 ms)2 elements (48 11/18 ms)or 3 elements (72 11/12 ms)For A polarity, 45 msFor Z polarity, 33 msBoth polarities 48 11/18 msBoth polarities 72 11/12 ms8.8 Dial pulse trains when received within the speed and ratio limits sp

36、ecified in Recommendation U.2 should beregenerated within the bypass unit, to be retransmitted by the multiplex equipment when the store is bypassed with aminimum duration of Z polarity of 32-34 ms and that of A polarity of 44-46 ms. Two or more elements of either A or Zpolarity should be transmitte

37、d as multiples of 24 11/36 ms and within the ratio limits specified should not exceed 73 msfor Z polarity and 98 ms for A polarity.8.9 The type B call confirmation or proceed-to-select signal when received by the multiplex equipment within thelimits specified by Recommendation U.1 should, on retrans

38、mission by the multiplex equipment, fall within the limits of32-50 ms. The interval of A polarity between call-confirmation and proceed-to-select signals should be not less than60 ms.8.10 In order to discriminate between the various type B backward path signals and to preserve their duration withina

39、cceptable limits it may be necessary to delay their transmission. This delay should be kept to a minimum in all cases.9 Standards of performance9.1 The stability of the master oscillator controlling the timing of each group should not be worse than 1 part in106.9.2 The degree of isochronous distorti

40、on of the aggregate output should not exceed 3%. The degree of synchronousstart-stop distortion of the channel output should not exceed 3%.9.3 The receiving input margin for both the aggregate and start-stop channel input should not be less than 45%.9.4 The maximum speed error for the start-stop out

41、put signals should not be greater than 0.5%.Fascicle VII.1 - Rec. R.44 510 Miscellaneous facilities10.1 It should be arranged that when phase is lost the output of the multiplex channels becomes a continuouscondition. When a channel is used for telex, the continuous condition should be A. When a cha

42、nnel is used for otherservices the condition may be Z if required.10.2 With the exception of combination No. 32, the 6-unit equivalents to the combinations of InternationalTelegraph Alphabet No. 2 have the first element of condition A. If the first element is received erroneously ascondition Z, the

43、character need not be rejected but may be passed to the channel output.Note The requirements to be met by synchronous multiplex equipment for telex and gentex operation aredefined in Recommendation U.24.ANNEX A(to Recommendation R.44)Combination No.in International TelegraphAlphabetNo. 2Letter case

44、Figure caseCode in InternationalTelegraphAlphabet No. 2(see Note 1)Code in InternationalTelegraphAlphabet No. 4(see Note 1)12345ABCDE?:Note 23ZZAAAZAAZZAZZZAZAAZAZAAAAAZZAAAAZAAZZAAZZZAAZAAZAAZAAAA678910FGHIJNote 28Note 2ZAZZAAZAZZAAZAZAZZAAZZAZAAZAZZAAAZAZZAAAZAZAAZZAAAZZAZA1112131415KLMNO().,9ZZZZ

45、AAZAAZAAZZZAAZZAAAAZZAZZZZAAAZAAZAAAZZZAAAZZAAAAAZZ1617181920PQRST0145AZZAZZZZAZAZAZAZAZAAAAAAZAAZZAZAZZZAZAAZAZAAZAZAAAAAAAZ2122232425UVWXY7=2/6ZZZAAAZZZZZZAAZZAZZZZAZAZAZZZAAAAZZZZAZZAAZAZAZZZAZAZAZ26 Z + ZAAAZ AZAAAZ27282930carriage returnline-feedletter-shiftfigure-shiftAAAZAAZAAAZZZZZZZAZZAAAAZ

46、AAAZAAAAZZZZZAZZAZZ3132-spacenot normally usedphasing signalsignal signal AAZAAAAAAApermanent A polaritypermanent Z polarityAAAZAAZAAAAAZZAAZZAAAAAAZZZZZZNote 1 Symbols A and Z have the meanings defined in Definition 31.38 of Recommendation R.140.Note 2 See Recommendation S.4 3.6 Fascicle VII.1 - Re

47、c. R.44References1 Report on synchronous telegraphy over standardized telegraph channels, White Book, Vol. VII, SupplementNo. 8, ITU, Geneva, 1969.2 CCITT Recommendation Transmission characteristics of the local end with its termination (ITA No. 2), Rec.S.3.3 CCITT Recommendation Use of International Telegraph Alphabet No. 2, Rec. S.4.