Emergency communication includes distress, urgengy and safety messages. These messages have absolute prioriy over other radio communication. Today, emergency communication is initiated with the appropriate "all stations" calling procedures using communication equipment with Digital Selective Calling capability, which is an essential part of the Global Maritime Distress and Safety System. After the appropriate alerts have been sent over the DSC channels, voice communication as described in the following will be conducted on the appropriate distress channels.
Code of Conduct during a Distress SituationAfter a distress situation has been made public on one of the distress and calling channels, the following rules should be respected:
A vessel is in distress when a crew member or the vessel itself are in grave
and imminent danger, which cannot be averted and requires immediate assistance.
The distress signal is the word "Mayday" and is to be used only on
the authority of the captain or person responsible for the vessel.
After the distress alarm has been sent to all the radio stations in the vicinity by the DSC controller (alerting all the receiving DSC stations by optical and acoustical signals), the distress voice communication is conducted on VHF channel 16 (156.8 MHz) or on MF 2182 kHz according to the following procedures:
1. Distress Call
After having transmitted the distress alarm, the vessel requiring help will send a distress call "to all stations" including information on it's position, the nature of distress, which kind of assistance is expected. To obtain best possible understandability, this information is sent in a fixed formatted Distress Call. This format ensures that vital information is communicated in a clear and concise way.
Radio stations receiving a distress call, must immediately
stop all communication on channel 16 and continue to listen and record the distress
Distress alarms sent over DSC will also be stored in the memory of the receiving
DSC controller and may contain additional information such as position, time and
nature of distress.
2. Distress Acknowledge Message
After receiving a distress alarm, allow at least 5 Minutes of time for the coast stations or the Search-and-Rescue stations to prepare suitable actions. Should a distress call appear to remain unanswered after this period of time, then any vessel able to reply should acknowledge the distress call even if it is not in a direct position to assist.
This Distress Acknowledge message will also be communicated in the shown format.
Every effort should then be made to relay the distress message to a Search-and-Rescue or Coast Guard authority in order that further action can be taken to assist the vessel in distress.
3. Distress Relay Call
If a vessel or coast station receives a distress call and feels that further assistance is necessary, or a distress message has only been received (and acknowledged) by a vessel not in a position to assist, the "Distress Relay Call" may be used to re-transmit the received distress call. Also in situations in which a vessel in distress is unable to transmit a distress call for itself, a vessel in the vicinity may initiate a distress alarm on behalve of the vessel in distress using this "Distress Relay Call".
Note, that DSC radio equipment stores all incoming
DSC alerts automatically.
In the case that such an alarm has to be relayed, the stored distress call can
be re-transmitted (to all stations or selectively to the nearest coast station)
using the digital DSC channel.
In this case no voice communication as described above is conducted.
However, if the vessel in distress has no DSC equipment it may be interested
in hearing a voice message in which the Distress Relay is reported.
In this case, the vessel in distress is addressed directly with a
"Distress Relay Call".
Control of all distress traffic is primarily the responsibility of the station in distress. However, this responsibility is usually handed off to a Maritime Rescue Coordination Centre (MRCC) by the distress vessel as they are in a better position to coordinate communication, and impose silence on any station that may be interfering with distress traffic.
All vessels who are aware of the existence of a distress
situation and are not in a position to be of assistance are forbidden to
transmit on any frequency being used for distress traffic and / or search
and rescue related activity.
Having been made aware that a distress situation exists,
the coordinating radio station will normally make use of the signal
"Silence Mayday" to impose radio silence
on Channel 16. This indicates that distress traffic is being passed on that
channel and that it is not to be used for any traffic that is of less than
If the distress situation is relieved, the station in distress
(or an involved search and rescue station) may want to end the ongoing distress
condition that imposes radio silence on the distress channel.
Therefore, as soon as normal communication can be resumed on the distress channel,
the coordinating radio station will make an announcement to this effect on
the distress channel in use with the call "Silence Fini".
5. Cancellation of a false Distress Alarms
In the DSC system, false distress alarms may easily be transmitted
by accident and should be cancelled immediately with the
"Cancel Distress" message.
An urgency situation exists if a crew member or the vessel itself require urgent help, without being in immediate danger. The urgency signal is "Pan Pan".
Exemplary situations allowing urgency communication:
The urgency communication will be initiated using a DSC
urgency alarm sent to all stations in the vicinity of the station requiring help.
Additionally, a "Urgency Call"
may be broadcast on the distress channel with the indication of a
working channel on which the details of the urgency call will be repeated.
The shift to a working channel is required to keep the distress channel
clear for higher priority communication.
The safety signal is "Securité" and indicates that an important message concerning the safety of shipping will follow. Such messages usually originate ashore, but they can be used by ships at sea to report a navigational hazard.
Exemplary situations allowing safety communication:
Safety communication has lower priority than
distress and urgency communication.
Therefore, the transmission of a safety alarm on the DSC calling
channel, will include a working channel on which the
"Safety Call" will be transmitted.
|Cover << Sail Away << Marine Radio Communication << .||.>> Data Transmission||last updated: 22-Feb-2008|