1、60 ITU-R RECMN*M- SERIES*PT*3 95 4855232 0527913 171 RW. ITU-R M.476-5 RECOMMENDATION ITU-R M.476-5* DIRECT-PRINTING TELEGRAPH EQUIPMENT IN THE MARITIME MOBILE SERVICE* (Question IT-R 518) (1970- 1974- 1978- 1982-1986- 1995) Summary The Recommendation provides in Annex 1 characteristics for error de
2、tecting and correcting systems for existing direct-printing telegraph equipment. Annex 1 contains the technical characteristics of the transmission, the code and the modes of operation to be employed in the maritime-mobile service. New equipment should conform to Recommendation IT-R M.625. The ITLJ
3、Radiocommunication Assembly, considering a) that there is a requirement to interconnect mobile stations, or mobile stations and coast stations, equipped with start-stop apparatus employing the ITU-T International Telegraph Alphabet No. 2, by means of radiotelegraph circuits; b) that direct-printing
4、telegraphy communications in the maritime mobile service can be listed in the following categories: b.a telegraph service between a ship and a coast station; b.b telegraph service between a ship and an extended station (ships owner) via a coast station; b.c telex service between a ship and a subscri
5、ber of the (international) telex network; b.d broadcast telegraph service from a coast station to one or more ships; b.e telegraph service between two ships or between one ship and a number of other ships; c) that those categories are different in nature and that consequently different degrees of tr
6、ansmission quality may be required; d) that the categories given in b.a, b.b and b.c above may require a higher transmission quality than categories b.d and b.e for the reason that data could be handled through the services in the categories b.a, b.b and b.c, while the messages passed through the se
7、rvice of category b.d, and via the broadcast service of category b.e are normally plain language, allowing a lower transmission quality than that required for coded information; * This Recommendation should be brought to the attention of the International Maritime Organization (IMO) and the Telecomm
8、unication Standardization Sector (U-T). This Recommendation is retained in order to provide information concerning existing equipment, but will probably be deleted at a later date. New equipment should conform to Recommendation -R M.625 which provides for the exchange of identification signals, for
9、the use of 9 digit maritime mobile service identification signals and for compatibility with existing equipment built in accordance with this Recommendation. Note by the Secretariar: The references made to the Radio Regulations (RR) in this Recommendation refer to the RR as revised by the World Radi
10、ocommunication Conference 1995. These elements of the RR will come into force on 1 June 1998. Where applicable, the equivalent references in the current RR are also provided in square brackets. * ITU-R RECMN*N. SERIES*PT*3 95 M 4855212 0527914 O08 M Rec. ITU-R M.476-5 61 e) method, as there is in pr
11、inciple no return path; that the service in category b.d and the broadcast service in category b.e cannot take advantage of an ARQ 0 forward error-correcting (FEC) mode should be used; that for these categories of service which by their nature do not allow the use of AQ, another mode, i.e. the 9 tha
12、t the period for synchronization and phasing should be as short as possible and should not exceed 5 s; h) that most of the ship stations do not readily permit simultaneous use of the radio transmitter and radio receiver; j) that the equipment on board ships should be neither unduly complex nor expen
13、sive, recommends 1 that when an error-detecting and correcting system is used for direct-printing telegraphy in the maritime mobile service, a 7-unit ARQ system or a 7-unit forward acting, error-correcting and indicating time-diversity system, using the same code, should be employed; 2 that equipmen
14、t designed in accordance with 8 1 should meet the characteristics laid down in Annex 1. ANNEX 1 1 General (Mode A, ARQ and Mode B, FEC) 1.1 7-unit error-detecting code as listed in 8 2 of this Annex. The system in both Mode A (ARQ) and Mode B (FEC) is a single-channel synchronous system using the 1.
15、2 should have an accuracy of better than 30 parts in lo6. FSK modulation is used on the radio link at 100 Bd. The equipment clocks controlling the modulation rate NOTE 1 - Some existing equipments may not conform to this requirement. 1.3 Alphabet No. 2 at a modulation rate of 50 Bd. The terminal inp
16、ut and output must be in accordance with the 5-unit start-stop ITU-T International Telegraph 1.4 The class of emission is F1B or J2B with a frequency shift on the radio link of 170 Hz. When frequency shift is effected by applying audio signals to the input of a single-sideband transmitter, the centr
17、e frequency of the audio spectrum offered to the transmitter should be 1 700 Hz. NOTE 1 - A number of equipments are presently in service, using a centre frequency of 1500 Hz. These may require special measures to achieve compatibility. 1.5 The radio frequency tolerance of the transmitter and the re
18、ceiver should be in accordance with Recommendation ITU-R SM.1137. It is desirable that the receiver employs the minimum practicable bandwidth (see also Report ITU-R M.585). NOTE 1 - The receiver bandwidth should preferably be between 270 and 340 Hz. - ITU-R RECMN*M. SERIES*PT*3 75 = 4855212 0527735
19、T44 Rec. ITU-R M.476-5 Combi- nation No. 1 2 62 2 Table of conversion Letter case A B 2.1 Traffk information signals 26 28 29 30 31 32 TABLE 1 2 = (Line feed) .1 (Letter shift) ? (Figure shift) Space Unperforated tape Control signal 1 (CSl) Control signal 2 (CS2) Control signal 3 (CS3) Idle signai I
20、dle signai a Signal repetition 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 _ BYBYYBB YBYBYBB BYYBBYB BBYYBBY BBBBYYY Phasing signal 1 YBBYYBB Phasing signal 2 C D E F G H I J K L M N O P Q R S T U V W X Y Figure case - ? International Telegraph Alphabet No. 2 Code ZZAAA ZAAZZ AZZZA
21、 ZAAZA ZAAAA ZAZZA AZAZZ AAZAZ AZZAA ZZAZA ZZZZA AZAAZ AAZZZ AAZZA AAAZZ AZZAZ ZZZAZ AZAZA ZAZAA AAAAZ ZZZAA AZZZZ ZZAAZ ZAZZZ ZAZAZ ZAAAZ AAAZQ AZAAA z7.7.7.7. ZZAZZ AAZAA AAAAA Emitted 7-unit signal() BBBYYYB YBYYBBB BYBBBYY BBYYBYB YBBYBYB BBYBBYY BYBYBBY BYYBYBB BYBBYYB BBBYBYY YBBBBYY BYBYYBB B
22、YYBBBY BYYBBYB BYYYBBB BYBBYBY YBBBYBY BYBYBYB BBYBYYB YYBYBBB YBBBYYB YYBBBBY BBBYYBY YBYBBBY BBYBYBY BBYYYBB YYYBBBB YYBBYBB YBYBBYB YBBYBBY YYBBBYB YBYBYBB (1 B represents the higher emitted frequency and Y the lower. At present unassigned (see ITU-T Recommendation F.l C8). Reception of these sig
23、nals, however, should not initiate a request for repetition. The pictorial representation shown is a schematic of which may also be used when equipment allows (IT-T Recommendation F. 1). (3) 2.2 Service information signals TABLE 2 Mode A (ARQ) I Emitted signal 1 Mode B (FEC) 1TU-R RECMN*M. SERIES*PT
24、*3 75 W 4855212 0527716 780 = Rec ITU-R M.476-5 63 3 Characteristics 3.1 Mode A (ARQ) (see Figs. 1 and 2) A synchronous system, transmitting blocks of three characters from an information sending station (ISS) towards an information receiving station (IRS). which stations can, controlled by the cont
25、rol signal 3 (see 8 2.2), interchange their functions. 3.1.1 Master and slave arrangements 3.1.1.1 the station that has been called will be the “slave” station; The station that initiates the establishment of the circuit (the calling station) becomes the “master” station, and this situation remains
26、unchanged during the entire time in which the established circuit is maintained, regardless of which station, at any given time, is the information sending station (ISS) or information receiving station (IRS); 3.1.1.2 the clock in the master station controls the entire circuit (see circuit timing di
27、agram, Fig. 1); 3.1.1.3 transmission pause during which reception is effected; the basic timing cycle is 450 ms, and for each station consists of a transmission period followed by a 3.1.1.4 the master station transmitting time distributor is controlled by the clock in the master station; 3.1.1.5 the
28、 slave station receiving time distributor is controlled by the received signal; 3.1.1.6 the time interval between the end of the received signal and the start of the transmitted signal (t in Fig. 1) is constant; the slave station transmitting time distributor is phase-locked to the slave station rec
29、eiving time distributor; i.e. 3.1.1.7 the master station receiving time distributor is controlled by the received signal. 3.1.2 The information sending station (ISS) 3.1.2.1 necessary, “idle signals ” to complete or to fill blocks when no traffic information is available; Groups the information to b
30、e transmitted into blocks of three characters (3 x 7 signal elements), including, if 3.1.2.2 emits a “block” in 210 ms after which a transmission pause of 240 ms becomes effective, retaining the emitted block in memory until the appropriate control signal confirming correct reception by the informat
31、ion receiving station (IRS) has been received; 3.1.2.3 numbers successive blocks alternately “Block 1” and “Block 2” by means of a local numbering device. The first block should be numbered “Block 1” or “Block 2” dependent on whether the received control signal (see Q 3.1.4.5) is a control signal 1
32、or a control signal 2. The numbering of successive blocks is interrupted at the reception of: - a request for repetition; or - a mutilated signai; or - a control signal 3 (see Q 2.2); 3.1.2.4 emits the information of Block 1 on receipt of control signal 1 (see 5 2.2); 3.1.2.5 emits the information o
33、f Block 2 on receipt of control signal 2 (see 5 2.2); 3.1.2.6 emits a block of three “signal repetitions” on receipt of a mutilated signal (see 0 2.2). 64 1TU-R REC“KN. SERIES*PT*3 95 4855232 0527917 837 = Rec. ITU-R M.476-5 FIGURE 1 A-Mode operation Selective call No. 32610 transmitted as -1 -1 (se
34、e Recommendation m-R M.49 1 $2,3) statim I Station ii Transmitter Receiver Receiver Transmitter II Masterstation Slave station 03.1.6.1 -C I3.1.6.1 Y Basic timing cycle a) Start of communication b) c) End of communication Change of the direction of the mffic flow CS: control signal ISS: information
35、sending station IRS: information receiving station RQ: signal repetition information signal 2 I t: figureshift tp: (one way) pmpagation time E: (fixed) equipment delay * The transmission of these signais may be omitted mi ITU-R RECMN*M- SERIES*PT*3 75 4855212 0527718 753 Rec. ITU-R M.476-5 F - * RO
36、FIGURE 2 Mode A under error receiving conditions CS1 Station I Master Transmitter Receiver RQ c- CSI G Station II Slave Receiver Transmitter CS1 6 3.1.2.4 -. 6 3.1.2.5 -. 9 3.1.2.3 0 3.1.2.6 + B C I Block1 I C - I E F E F I Block2 DI *- Block 2 (repeated) DIJ E RQ I H I I Block1 4 I 1 I * Detected e
37、rror symbol 3.1.3.4 Printing 5 3.1.3.4 J-5 3.1.3.3 - J- 3.1.3.3 . A B C stop Poianty D E F StOP polarity G H I w2 65 3.1.3 The information receiving station (IRS) 3.1.3.1 device, the numbering being interrupted at the reception of: - - 3.1.3.2 pause of 380 ms becomes effective; Numbers the received
38、blocks of three characters alternately “Block 1” and “Block 2” by a local numbering a block in which one or more characters are mutilated; or a block containing at least one “signal repetition”; (8 3.1.2.6) after the reception of each block, emits one of the control signals of 70 ms duration after w
39、hich a transmission 3.1.3.3 - - - emits the control signal 1 at the reception of: an unmutilated “Block 2”. or a mutilated “Block 1”. or “Block 1” containing at least one “signal repetition”; ITU-R RECHNUM. SERIES*PT*3 95 4855212 0527919 b9T 66 Rec. ITU-R M.476-5 3.1.3.4 - - - emits the control sign
40、al 2 at reception of: an unmutilated “Block l”, or a mutilated “Block ”, or a “Block 2” containing at least one “signal repetition”. 3.1.4 Phasing 3.1.4.1 or IRS and no master or slave position is assigned to either of the stations; 3.1.4.2 three signals (see Note 1); 3.1.4.3 the call signal contain
41、s: - When no circuit is established, both stations are in the “stand-by” position. In this stand-by position no ISS the station desiring to establish the circuit emits the “call” signal. This “call” signal is formed by two blocks of in the first block: “signal repetition” in the second character pla
42、ce and any combination of information signals (see Note 2) in the first and third character place, in the second block: “signal repetition” in the third character place preceded by any combination of the 32 information signals (see Note 2) in the first and second character place; - 3.1.4.4 the contr
43、ol signal 1 or the control signal 2; 3.1.4.5 on receipt of two consecutive identical control signals, the calling station changes into ISS and operates in accordance with 0 3.1.2.4 and 3.1.2.5. NOTE 1 - A station using a two block call signal, shall be assigned a number in accordance with RR Nos. S1
44、9.37, S19.83 and S19.92 to S19.95 Nos. 2088,2134 and 2143 to 21461; NOTE 2 - The composition of these signals and their assignment to individual ships require international agreement (see Recommendation ITU-R M.49 1). on receipt of the appropriate call signal the called station changes from stand-by
45、 to the IRS position and emits 3.1.5 Rephasing (Note 1) 3.1.5.1 When reception of information blocks or of control signals is continuously mutilated, the system reverts to the “stand-by” position after a predetermined time (a preferable predetermined time would be the duration of 32 cycles of 450 ms
46、), to be decided by the user, of continuous repetition; the station that is master station at the time of interruption immediately initiates rephasing along the same lines as laid down in 0 3.1.4; 3.1.5.2 if, at the time of interruption, the slave station was in the IRS position, the control signal
47、to be returned after phasing should be the same as that last sent before the interruption to avoid the loss of an information block upon resumption of the communication. (Some existing equipments may not conform to this requirement); 3.1.5.3 however, if, at the time of interruption, the slave statio
48、n was in the ISS position, it emits, after having received the appropriate call blocks, either: - the control signal 3; or - the control signal 1 or 2 in conformity with 0 3.1.4.4, after which control signal 3 is emitted to initiate changeover to the ISS position; if rephasing has not been accomplis
49、hed within the time-out interval of 0 3.1.9.1, the system reverts to the 3.1.5.4 stand-by position and no further rephasing attempts are made. NOTE 1 - Some coast stations do not provide rephasing (see also Recommendation FU-R M.492). 3.1.6 Change-over 3.1.6.1 - The information sending station (ISS) Emits, to initiate a change in the direction of the traffic flow, the information signal sequence “Figure shift” - “Plus” (“figure case of 2”) - “Question mark” (“figure case of B”) (see Note 1) followed, if necessary, by one or more “idle signals
