Direct-printing telegraph equipment employing automatic identification in the maritime mobile service




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Rec. ITU-R M.625-3

RECOMMENDATION ITU-R M.625-3*

DIRECT-PRINTING TELEGRAPH EQUIPMENT EMPLOYING AUTOMATIC
IDENTIFICATION IN THE MARITIME MOBILE SERVICE**

(Question ITU-R 5/8)

(1986-1990-1992-1995)

Rec. ITU-R M.625-3




Summary


The Recommendation provides in Annex 1 characteristics of direct-printing telegraph equipment employing a 7-unit ARQ method for selective communication, a 7-unit FEC method for broadcast mode and automatic identification to be used for newly developed equipment to provide compatibility with existing equipment conforming to Recommen­dation ITU-R M.476.

The ITU Radiocommunication Assembly,



considering

a) that there is a requirement to interconnect ship stations or ship 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 telegraph equipment in the maritime mobile service is used for:

– telex and/or telegraph service between a ship station and a subscriber of the (international) telex network;

– telegraph service between a ship station and a coast station or between two ship stations;

– telegraph service between a ship station and an extended station (ship owner) via a coast station;

– telegraph service in a broadcast mode from a coast station, or a ship station, to one or more ship stations;

c) that the broadcast mode cannot take advantage of an ARQ method, as a return path is not used;

d) that for the broadcast mode a forward error-correcting (FEC) method should be used;

e) that the period for synchronization and phasing should be as short as possible;

f) that most of the ship stations do not readily permit the simultaneous use of radio transmitter and receiver;

g) that a direct-printing telegraph system employing error-detecting and error-correcting methods in accordance with Recommendation ITU-R M.476, is in actual operation;

h) that the increased use of direct-printing telegraph equipment has emphasized the importance of an unambiguous identification of both stations when a circuit is established or re-established;

j) that unambiguous identification could be accomplished by the exchange of self-identification signals between the ARQ equipments at the 7-unit level;

k) that Appendix 43 of the Radio Regulations (RR), Recommendation ITU-R M.585 and ITU-T Recommen­dations E.210 and F.120 provide for a comprehensive system of assigning maritime mobile service identities;

l) that, in the interest of having a unique identity assigned to each ship station for distress and safety and other telecommunication purposes, the address capability should allow the use of maritime mobile service identities in accordance with the provisions of Appendix 43 of the RR;

m) that equipment built in accordance with Recommendation ITU-R M.476 cannot provide for the use of maritime mobile service identities mentioned in § k);

n) that there is a need to provide for compatibility to the extent possible with equipments built in accordance with Recommendation ITU-R M.476; however, unambiguous identification of both stations cannot be achieved when circuits are established with equipments built in accordance with Recommendation ITU-R M.476,



recommends

1 that for direct-printing telegraph circuits in the maritime mobile service, a 7-unit ARQ method should be employed;

2 that for the direct-printing telegraph service in the broadcast mode, a 7-unit forward acting error-correcting method, using time diversity, should be employed;

3 that equipment designed in accordance with § 1 and 2 should employ automatic identification and have the characteristics given in Annex 1.
ANNEX 1

CONTENTS


Page

1 General (mode A (ARQ) and mode B (FEC)) 4

2 Conversion tables 4

2.1 General 4

2.2 Traffic information signals 4

2.3 Service information signals 4

2.4 Identification and check-sum numbers and signals 6

2.5 Check-sum signal derivation 6

3 Characteristics, mode A (ARQ) 7

3.1 General 7

3.2 Master and slave arrangements 7

3.3 The information sending station (ISS) 7

3.4 The information receiving station (IRS) 7

3.5 Phasing procedure 8

3.6 Automatic identification 9

3.7 Traffic flow 11

3.8 Rephasing procedure 12

3.9 Summary of service blocks and service information signals 14

4 Characteristics, mode B (FEC) 14

4.1 General 14

4.2 The sending station (CBSS and SBSS) 14

4.3 The receiving station (CBRS and SBRS) 15

4.4 Phasing procedure 15

4.5 Selecting calling procedure (selective B-mode) 15

4.6 Traffic flow 15

Page


Appendix 1  – SDL diagrams (mode A) 27

Appendix 2  – Phasing procedure with automatic identification in the case of a 7-signal call identity (calling station) 31

Appendix 3  – Rephasing procedure with automatic identification in the case of a 7-signal call identity (calling station) 34

Appendix 4  – Phasing procedure without automatic identification in the case of a 4-signal call identity (calling station) 37

Appendix 5  – Rephasing procedure without automatic identification in the case of a 4-signal call identity (calling station) 38

Appendix 6  – Phasing procedure with automatic identification in the case of a 7-signal call identity (called station) 39

Appendix 7  – Rephasing procedure with automatic identification in the case of a 7-signal call identity (called station) 42

Appendix 8  – Phasing procedure without automatic identification in the case of a 4-signal call identity (called station) 45

Appendix 9  – Rephasing procedure without automatic identification in the case of a 4-signal call identity (called station) 46

Appendix 10  – Traffic flow in the case of a 4-signal call identity and in the case of a 7-signal call identity (station is in the ISS position) 47

Appendix 11  – Traffic flow in the case of a 4-signal call identity and in the case of a 7-signal call identity (station is in the IRS position) 50

Appendix 12  – State overview diagrams 52

Sheet 1 – Phasing procedure with automatic identification in the case of a 7-signal call identity (calling station) and traffic flow if the station is in the ISS position 52

Sheet 2 – Rephasing procedure with automatic identification in the case of a 7-signal call identity (calling station) and traffic flow if the station is in the ISS position 53

Sheet 3 – Phasing procedure without automatic identification in the case of a 4-signal call identity (calling station) and traffic flow if the station is in the ISS position 54

Sheet 4 – Rephasing procedure without automatic identification in the case of a 4-signal call identity (calling station) and traffic flow if the station is in the ISS position 55

Sheet 5 – Phasing procedure with automatic identification in the case of a 7-signal call identity (called station) and traffic flow if the station is in the IRS position 56

Sheet 6 – Rephasing procedure with automatic identification in the case of a 7-signal call identity (called station) and traffic flow if the station is in the IRS position 57

Sheet 7 – Phasing procedure without automatic identification in the case of a 4-signal call identity (called station) and traffic flow if the station is in the IRS position 58

Sheet 8 – Rephasing procedure without automatic identification in the case of a 4-signal call identity (called station) and traffic flow if the station is in the IRS position 59


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