CIRCULAR LETTER
COMSAR/Circ.25
PROCEDURE FOR RESPONDING TO DSC DISTRESS ALERTS BY SHIPS
(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.
ANNEX.
PROCEDURE FOR RESPONDING TO DSC DISTRESS ALERTS BY SHIPS
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.
2.1
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.
3.1
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.
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.
5.1
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.
________________
* Elements of flow diagrams are shadowed in
different shades meaning different colours if printed on a colour printer.
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.
FLOW
DIAGRAM 1.
ACTION BY SHIPS UPON RECEPTION OF VHF / MF DSC DISTRESS ALERT
REMARKS:
Note 1: Appropriate or
relevant RCC and / or Coast Station shall be informed accordingly. If the
further DSC alerts are received from the same source and the ship in distress
is beyond doubt in the vicinity, a DSC acknowledgement may, after consultation
with an RCC or Coast Station be sent to terminate the call.
Note 2: In no case is a ship
permitted to transmit a DSC distress relay call on receipt of a DSC distress
alert on either VHF channel 70 or MF channel 2187,5 kHz
CS = Coast Station
RCC = Rescue Co-ordination
Center