T2/6.06 COMSAR/Circ.25
15 March 2001



1 The Sub-Committee on Radiocommunications and Search and Rescue (COMSAR), at its fifth session (11 to 15 December 2000), revised COMSAR/Circ.21 on Procedure for responding to DSC distress alerts by ships, as reproduced at annex.

2 This circular revokes COMSAR/Circ.2 and COMSAR/Circ.21.




1 Introduction

The Sub-Committee on Radiocommunications and Search and Rescue (COMSAR), at its fourth session (12 to 16 July 1999), decided that digital selective calling (DSC) relays of distress alerts on all shipbome DSC equipment should be reduced and prepared a procedure for responding to VHF/MF and HF distress alerts, given in flow diagrams 1 and 2, recommending that it be displayed on the ship's bridge as A4 size posters. It also prepared the following guidance.

2 Distress relays

2. 1 Radio personnel serving on ships should be made aware of the consequences of transmitting a distress relay call and of routeing a DSC distress relay alert to other than coast stations (CS).

2. 2 The number of unintended activations of DSC distress alerts and DSC distress relay alerts creates extra work load and confusion to (M) RCCs and also causing delay in the response-time. The original distress alert from a ship in distress should not be disrupted by other ships, by transmitting a DSC distress relay alert.

2. 3 Recommendation ITU-R M. 541-8 on Operational procedures for the use of DSC equipment in the Maritime Mobile Service identifies only two situations in which a ship would transmit a distress relay call (distress relay alert):

.1 on receiving a distress alert on a HF channel, which is not acknowledged by a coast station within 5 minutes. The distress relay call should be addressed to the appropriate coast station (Annex 1, paragraph 3. 4. 2 and Annex 3, paragraph 6. 1. 4); and

.2 on knowing mat another ship in distress is not itself able to transmit the distress alert and the Master of the ship considers that further help is necessary. The distress relay call should be addressed to "all ships" or to the appropriate coast station (Annex 3, paragraph 1. 4).

2. 4 In no case is a ship permitted to transmit a DSC distress relay call on receipt of a DSC distress alert on either VHF or MF channels.

2. 5 Distress relay calls on HF channels should be initiated manually.

2. 6 Compliance with operational and technical provisions above would prevent transmissions of inappropriate distress relay calls.

3 All coast stations call

3. 1 Recommendation ITU-R M. 493-9 on DSC systems for use in the Maritime Mobile Service provides for "group calls" an address consisting of the characters corresponding to the station's Maritime Mobile Service identity (MMSI) and a number of administrations have already assigned a "group call" MMSI to their coast stations in addition to the coast station's individual MMSI.

3. 2 By multilateral agreements, a "group call" MMSI could be assigned to all coast stations of a specific region, e. g., an RCC area and could comply with IMO's requirement without reed of introducing further modifications to GMDSS equipment.

3. 3 An alternative method to implement an "all coast stations" call without the need to modify Recommendation ITU-R M. 493-9 could be to define one MMSI world-wide as an address for all coast stations, in accordance with Nos. SI 9. 100 to SI 9. 126 of the ITU Radio Regulations. However, this solution would also require a modification of the setup at each coast station participating in the GMDSS.

4 Authorization

It should be noted that on ships, distress alerts, distress acknowledgements and distress relay calls can only be transmitted with permission of the Master of the ship.

5 Flow diagrams

5. 1 The simplified flow diagrams* 1 and 2 describe actions to be taken aboard ships upon receipt of distress alerts from other ships. Administrations should give wide distribution of these flow diagrams to ships and training institutions.

5. 2 Member Governments are invited to bring the above guidance and the attached flow diagrams to the attention of their shipowners, seafarers, coast stations, RCCs and all others concerned.

* Elements of flow diagrams are shadowed in different shades meaning different colours if printed on a colour printer.