Summary. Rec. ITU-R M RECOMMENDATION ITU-R M.476-5*

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1 Rec. IU-R RONDION IU-R Rec. IU-R DIR-PRININ LRPH UIPN IN H RII OBIL RVI (uestion IU-R 5/8) ( ) ummary he Recommendation provides in nnex characteristics for error detecting and correcting systems for existing direct-printing telegraph equipment. nnex 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 IU-R.65. he IU Radiocommunication ssembly, considering a) that there is a requirement to interconnect mobile stations, or mobile stations and coast stations, equipped with start-stop apparatus employing the IU- International elegraph lphabet No., by means of radiotelegraph circuits; b) that direct-printing telegraphy communications in the maritime mobile service can be listed in the following categories: b.a b.b b.c b.d b.e telegraph service between a ship and a coast station; telegraph service between a ship and an extended station (ship s owner) via a coast station; telex service between a ship and a subscriber of the (international) telex network; broadcast telegraph service from a coast station to one or more ships; 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 transmission 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 service 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; his Recommendation should be brought to the attention of the International aritime Organization (IO) and the elecommunication tandardization ector (IU-). his 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 IU-R.65 which provides for the exchange of identification signals, for 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 ecretariat: he references made to the Radio Regulations (RR) in this Recommendation refer to the RR as revised by the World Radiocommunication onference 995. hese elements of the RR will come into force on June 998. Where applicable, the equivalent references in the current RR are also provided in square brackets.

2 Rec. IU-R e) that the service in category b.d and the broadcast service in category b.e cannot take advantage of an method, as there is in principle no return path; f) that for these categories of service which by their nature do not allow the use of, another mode, i.e. the forward error-correcting (F) mode should be used; g) that 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 expensive, recommends that when an error-detecting and correcting system is used for direct-printing telegraphy in the maritime mobile service, a 7-unit system or a 7-unit forward acting, error-correcting and indicating time-diversity system, using the same code, should be employed; that equipment designed in accordance with should meet the characteristics laid down in nnex. NN eneral (ode, and ode B, F). he system in both ode () and ode B (F) is a single-channel synchronous system using the 7-unit error-detecting code as listed in of this nnex.. FK modulation is used on the radio link at 00 Bd. he equipment clocks controlling the modulation rate should have an accuracy of better than 30 parts in 0 6. NO ome existing equipments may not conform to this requirement..3 he terminal input and output must be in accordance with the 5-unit start-stop IU- International elegraph lphabet No. at a modulation rate of 50 Bd..4 he class of emission is FB or JB with a frequency shift on the radio link of 70 Hz. When frequency shift is effected by applying audio signals to the input of a single-sideband transmitter, the centre frequency of the audio spectrum offered to the transmitter should be 700 Hz. NO number of equipments are presently in service, using a centre frequency of 500 Hz. hese may require special measures to achieve compatibility..5 he radio frequency tolerance of the transmitter and the receiver should be in accordance with Recommendation IU-R.37. It is desirable that the receiver employs the minimum practicable bandwidth (see also Report IU-R.585). NO he receiver bandwidth should preferably be between 70 and 340 Hz.

3 Rec. IU-R able of conversion. raffic information signals BL ombination No. Letter case Figure case International elegraph lphabet No. ode mitted 7-unit signal () B : D (3) 3 F () () H () I 8 J udible signal K ( L ). N, O 9 P 0 R 4 5 U 7 V = W / Y 6 Z (arriage return) (Line feed) (Letter shift) (Figure shift) pace 0 Unperforated tape ZZ ZZZ ZZZ ZZ Z ZZZ ZZZ ZZ ZZ ZZZ ZZZZ ZZ ZZZ ZZ ZZ ZZZ ZZZZ ZZ ZZ Z ZZZ ZZZZ ZZZ ZZZZ ZZZ ZZ Z Z ZZZZZ ZZZZ Z BBBYYYB YBYYBBB BYBBBYY BBYYBYB YBBYBYB BBYBBYY BYBYBBY BYYBYBB BYBBYYB BBBYBYY YBBBBYY BYBYYBB BYYBBBY BYYBBYB BYYYBBB BYBBYBY YBBBYBY BYBYBYB BBYBYYB YYBYBBB YBBBYYB YYBBBBY BBBYYBY YBYBBBY BBYBYBY BBYYYBB YYYBBBB YYBBYBB YBYBBYB YBBYBBY YYBBBYB YBYBYBB () B represents the higher emitted frequency and Y the lower. () t present unassigned (see IU- Recommendation F. 8). Reception of these signals, however, should not initiate a request for repetition. (3) he pictorial representation shown is a schematic of which may also be used when equipment allows (IU- Recommendation F.).. ervice information signals BL ode () mitted signal ode B (F) ontrol signal () ontrol signal () ontrol signal 3 (3) Idle signal Idle signal ignal repetition BYBYYBB YBYBYBB BYYBBYB BBYYBBY BBBBYYY YBBYYBB Phasing signal Phasing signal

4 4 Rec. IU-R haracteristics 3. ode () (see Figs. and ) synchronous system, transmitting blocks of three characters from an information sending station (I) towards an information receiving station (IR), which stations can, controlled by the control signal 3 (see.), interchange their functions. 3.. aster and slave arrangements 3... he station that initiates the establishment of the circuit (the calling station) becomes the master station, and the station that has been called will be the slave station; this situation remains 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 (I) or information receiving station (IR); 3... the clock in the master station controls the entire circuit (see circuit timing diagram, Fig. ); the basic timing cycle is 450 ms, and for each station consists of a transmission period followed by a transmission pause during which reception is effected; the master station transmitting time distributor is controlled by the clock in the master station; the slave station receiving time distributor is controlled by the received signal; the slave station transmitting time distributor is phase-locked to the slave station receiving time distributor; i.e. the time interval between the end of the received signal and the start of the transmitted signal (t in Fig. ) is constant; the master station receiving time distributor is controlled by the received signal. 3.. he information sending station (I) 3... roups the information to be transmitted into blocks of three characters (3 7 signal elements), including, if necessary, idle signals to complete or to fill blocks when no traffic information is available; 3... emits a block in 0 ms after which a transmission pause of 40 ms becomes effective, retaining the emitted block in memory until the appropriate control signal confirming correct reception by the information receiving station (IR) has been received; numbers successive blocks alternately Block and Block by means of a local numbering device. he first block should be numbered Block or Block dependent on whether the received control signal (see ) is a control signal or a control signal. he numbering of successive blocks is interrupted at the reception of: a request for repetition; or a mutilated signal; or a control signal 3 (see.); emits the information of Block on receipt of control signal (see.); emits the information of Block on receipt of control signal (see.); emits a block of three signal repetitions on receipt of a mutilated signal (see.).

5 aster station a) b) Line output, 50 Bd c) k l m n o top polarity tation I ransmitter Receiver I IR I K L N O P 3 R tand-by tand-by all block all block all block all block K L N O P 3 k l m n o Block Block Block Block Block over Block nd of communication hange of direction 3 Block over R 3 k l m n o Rec. IU-R tation II Receiver ransmitter aster station lave station Block Block IR lave station I IR FIUR -ode operation elective call No. 360 transmitted as () () (see Recommendation IU-R.49, 3) Block tand-by tand-by 450 ms 450 ms 450 ms 0 ms 0 ms 40 ms 70 ms t p Line output, 50 Bd K L N O P top polarity R a) b) c) Information block Information block ontrol signal ontrol signal ontrol signal Information block Basic timing cycle t p 0 ms 70 ms t t tart of communication hange of the direction of the traffic flow nd of communication : control signal I: information sending station IR: information receiving station : signal repetition information signal t: t p: t : aster station I lave station IR lave station I aster station IR figure shift (one way) propagation time (fixed) equipment delay he transmission of these signals may be omitted D0 FIUR...[D0] = 3

6 6 Rec. IU-R FIUR ode under error receiving conditions tation I aster ransmitter Receiver tation II lave Receiver ransmitter B Block B Printing D F Block D F B D F Block (repeated) D F top polarity Block D F H I Block H I top polarity H I Detected error symbol D0 FIUR..[D0]= he information receiving station (IR) Numbers the received blocks of three characters alternately Block and Block by a local numbering device, the numbering being interrupted at the reception of: a block in which one or more characters are mutilated; or a block containing at least one signal repetition ; ( 3...6) after the reception of each block, emits one of the control signals of 70 ms duration after which a transmission pause of 380 ms becomes effective; emits the control signal at the reception of: an unmutilated Block, or a mutilated Block, or Block containing at least one signal repetition ;

7 emits the control signal at reception of: an unmutilated Block, or a mutilated Block, or a Block containing at least one signal repetition Phasing Rec. IU-R When no circuit is established, both stations are in the stand-by position. In this stand-by position no I or IR and no master or slave position is assigned to either of the stations; the station desiring to establish the circuit emits the call signal. his call signal is formed by two blocks of three signals (see Note ); the call signal contains: in the first block: signal repetition in the second character place and any combination of information signals (see Note ) in the first and third character place, in the second block: signal repetition in the third character place preceded by any combination of the 3 information signals (see Note ) in the first and second character place; on receipt of the appropriate call signal the called station changes from stand-by to the IR position and emits the control signal or the control signal ; on receipt of two consecutive identical control signals, the calling station changes into I and operates in accordance with and NO station using a two block call signal, shall be assigned a number in accordance with RR Nos. 9.37, 9.83 and 9.9 to 9.95 [Nos. 088, 34 and 43 to 46]; NO he composition of these signals and their assignment to individual ships require international agreement (see Recommendation IU-R.49) Rephasing (Note ) 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 3 cycles of 450 ms), 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 3..4; if, at the time of interruption, the slave station was in the IR position, the control signal 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. (ome existing equipments may not conform to this requirement); however, if, at the time of interruption, the slave station was in the I position, it emits, after having received the appropriate call blocks, either: the control signal 3; or the control signal or in conformity with , after which control signal 3 is emitted to initiate changeover to the I position; if rephasing has not been accomplished within the time-out interval of 3..9., the system reverts to the stand-by position and no further rephasing attempts are made. NO ome coast stations do not provide rephasing (see also Recommendation IU-R.49) hange-over he information sending station (I) mits, to initiate a change in the direction of the traffic flow, the information signal sequence Figure shift Plus ( figure case of Z ) uestion mark ( figure case of B ) (see Note ) followed, if necessary, by one or more idle signals to complete a block; emits, on receipt of a control signal 3, a block containing the signals idle signal idle signal idle signal ; changes subsequently to IR after the reception of a signal repetition.

8 8 Rec. IU-R he information receiving station (IR) mits the control signal 3: a) when the station wishes to change over to I, b) on receipt of a block in which the signal information sequence Figure shift Plus (figure case of Z) uestion mark (figure case of B) terminates (see Note ) or upon receipt of the following block. In the latter case, the IR shall ignore whether or not one or more characters in the last block are mutilated: changes subsequently to I after reception of a block containing the signal sequence idle signal idle signal idle signal ; emits one signal repetition as a master station, or a block of three signal repetitions as a slave station, after being changed into I. NO In the elex network, the signal sequence combination No. 6 combination No., sent whilst the teleprinters are in the figure case condition, is used to initiate a reversal of the flow of information. he IR is, therefore, required to keep track of whether the traffic information flow is in the letter case or figure case mode to ensure proper end-to-end operation of the system Output to line the signal offered to the line output terminal is a 5-unit start-stop signal at a modulation rate of 50 Bd nswerback he WRU (Who are you) sequence, which consists of combination Nos. 30 and 4 in the IU- International elegraph lphabet No., is used to request terminal identification he information receiving station (IR), on receipt of a block containing the WRU sequence, which will actuate the teleprinter answerback code generator: changes the direction of traffic flow in accordance with 3..6.; transmits the signal information characters derived from the teleprinter answerback code generator; after transmission of blocks of idle signals (after completion of the answerback code, or in the absence of an answerback code), changes the direction of traffic flow in accordance with NO ome existing equipments may not conform to this requirement nd of communication When reception of information blocks or of control signals is continuously mutilated, the system reverts to the stand-by position after a predetermined time of continuous repetition, which causes the termination of the established circuit (a preferable predetermined time would be the duration of 64 cycles of 450 ms); the station that wishes to terminate the established circuit transmits an end of communication signal ; the end of communication signal consists of a block containing three idle signal : the end of communication signal is transmitted by the I; if an IR wishes to terminate the established circuit it has to change over to I in accordance with 3..6.; the IR that receives an end of communication signal emits the appropriate control signal and reverts to the stand-by position; on receipt of a control signal that confirms the unmutilated reception of the end of communication signal, the I reverts to the stand-by position; when after a predetermined number of transmissions (see Note ) of the end of communication signal no control signal has been received confirming the unmutilated reception of the end of communication signal, the I reverts to the stand-by position and the IR times out in accordance with NO preferable predetermined number would be four transmissions of the end of communication signal.

9 3. ode B, forward error correction (F) (see Figs. 3 and 4) Rec. IU-R synchronous system, transmitting an uninterrupted stream of characters from a station sending in the collective B-mode (B) to a number of stations receiving in the collective B-mode (BR), or from a station sending in the selective B-mode (B) to one selected station receiving in the selective B-mode (BR). 3.. he station sending in the collective or in the selective B-mode (B or B) 3... mits each character twice: the first transmission (D) of a specific character is followed by the transmission of four other characters, after which the retransmission (R) of the first character takes place, allowing for timediversity reception at 80 ms time space; 3... emits as a preamble to messages or to the call sign, alternately the phasing signal (see.) and the phasing signal (see.) whereby phasing signal is transmitted in the R, and phasing signal in the D position. t least four of these signal pairs (phasing signal and phasing signal ) should be transmitted. 3.. he station sending in the collective B-mode (B) 3... mits during the breaks between two messages in the same transmission the phasing signals and the phasing signals in the R and the D position, respectively he station sending in the selective B-mode (B) mits after the transmission of the required number of phasing signals (see 3...) the call sign of the station to be selected. his call sign is a sequence of four characters that represents the number code of the called station. he composition of this call sign should be in accordance with Recommendation IU-R.49. his transmission takes place in the time diversity mode according to 3...; emits the call sign and all further signals in a 3B/4Y ratio, i.e. inverted with respect to the signals in able in the column emitted 7-unit signal. onsequently, all signals, i.e. both traffic information signals and service information signals, following the phasing signals are transmitted in the 3B/4Y ratio; emits the service information signal idle signal during the idle time between the messages consisting of traffic information signals he station(s) receiving in the collective or in the selective B-mode (BR or BR) hecks both characters (D and R), printing an unmutilated D or R character, or printing an error symbol or space, if both are mutilated Phasing When no reception takes place, the system is in the stand-by position as laid down in 3..4.; on receipt of the sequence phasing signal phasing signal, or of the sequence phasing signal phasing signal, in which phasing signal determines the D and phasing signal determines the R position, and at least one further phasing signal in the appropriate position, the system changes from stand-by to the BR position; when started as BR the system changes to the BR (selectively called receiving station) position on receipt of the inverted characters representing its selective call number; having been changed into the BR or into the BR position the system offers continuous stop-polarity to the line output terminal until either the signal carriage return or line feed is received; when started as BR, the decoder re-inverts all the following signals received to the 3Y/4B ratio, so that these signals are offered to the BR in the correct ratio, but they remain inverted for all other stations; both the BR and the BR revert to the stand-by position if, during a predetermined time, the percentage of mutilated signals received has reached a predetermined value.

10 0 Rec. IU-R FIUR 3 B-mode operation tation I D R R LF 80 ms nd of emission signal tand-by tation II tand-by D R BR R LF ms Line output kept to stop-polarity top-polarity Printing rror symbol 6 times call signal ms ms ms ollectively electively : phasing signal B: B-mode - ending collectively : phasing signal BR: B-mode - Receiving collectively : carriage return (R) B: B-mode - ending selectively : line feed (LF) BR: B-mode - Receiving selectively Detected error symbol Overlined symbols (e.g. ) are transmitted in the 3B/4Y ratio tation I D R Τ nd of emission signal 0 ms tand-by tation II elective call No. 360 D Χ Τ Τ R LF tand-by R BR BR Line output kept to stop-polarity Printing D04 FIUR 3...[D04] = 3

11 Rec. IU-R FIUR 4 Flow chart showing processes in B-mode operation -mode end tand-by Receive B-mode.. L.L. equence Phasing signal - or phasing signal - Phasing signals and in the R and D position respectively, minimum 4-pairs -mode IR D and R positioning B B Phasing signal in the R position or Phasing signal in the D position arriage return and/or line feed all six times BR rrors all arriage return and/or line feed Determine percentage of mutilated signals BR essage essage When more than predetermined value Re-invert all further signals to 4B/3Y in D position in D position arriage return or line feed De-lock line output terminal from stop-polarity mission realized manually essage mission realized automatically in D position Delay 0 ms D and R faulty Print error-symbol D and/or R signal correct Print character Overlined symbols (e g ) are transmitted/detected in the 3B/4Y ratio D05 FIUR 4...[D05] = 3

12 Rec. IU-R Output to line he signal offered to the line output terminal is a 5-unit start-stop IU- International elegraph lphabet No. signal at a modulation rate of 50 Bd nd of emission he station sending in the B-mode (B or B) that wishes to terminate the emission transmits the end of emission signal ; the end of emission signal consists of three consecutive idle signals (see.) transmitted in the D position only, immediately after the last transmitted traffic information signal in the D position, after which the station terminates its emission and reverts to the stand-by position; nd of emission signal 0 ms D-position R-position Revert to stand-by D03 FIUR...[D03] = the BR or the BR reverts to the stand-by position not less than 0 ms after receipt of at least two consecutive idle signals in the D position.

RECOMMENDATION ITU-R M * DIRECT-PRINTING TELEGRAPH EQUIPMENT EMPLOYING AUTOMATIC IDENTIFICATION IN THE MARITIME MOBILE SERVICE **

RECOMMENDATION ITU-R M * DIRECT-PRINTING TELEGRAPH EQUIPMENT EMPLOYING AUTOMATIC IDENTIFICATION IN THE MARITIME MOBILE SERVICE ** Rec. ITU-R M.65- RCOMMNDTION ITU-R M.65- * DIRCT-PRINTING TLGRPH QUIPMNT MPLOYING UTOMTIC IDNTIICTION IN TH MRITIM MOBIL RVIC ** (Question ITU-R 5/8) Rec. ITU-R M.65- (986-990-99-995) ummary The Recommendation