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Distress Signals And Distress Traffic

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Within the GMDSS system, all maritime distress and safety communications are based on radiocommunication using terrestrial links on the VHF, MF and HF bands, and via satellites.

Ships must be able to transmit ship-to-shore alerts to RCC’s via coast radio stations or Coast Earth Stations (CES).

A ship can make use of the following 3 methods to transmit a distress alert:

  1. DSC (Digital Selective Calling) on the VHF/MF and HF bands.
  2. INMARSATA/B or C.
  3. EPIRB.

The International SOLAS (Safety of Lives at Sea) Convention of 1974 was adapted to the GMDSS system in 1988 (SOLAS 1988) and brought into effect on February 1, 1992.

The GMDSS system was launched as a programme commencing on February 1, 1992, and reaching complete implementation on February 1, 1999. Regulations and Traffic ProceduresGMDSS regulations apply to all passenger vessels sailing in international waters and to all cargo vessels over 300 gr. t. sailing in international waters. Categories of vessels sailing in national waters such as freighters under 300 gr. t. and fishing vessels are exempted from the 1988 SOLAS Convention as applied to GMDSS.

In practice, this means that these categories of vessels (non-convention vessels) are at liberty to use the frequencies and procedures described in SOLAS 1974 until new regulations have been developed and implemented at a national level. GMDSS Distress and Safety CommunicationsThe distress and safety procedures for radiotelephony (SOLAS 1974) will be dealt with in this and the following articles.

General regulations

The procedures described in this article are compulsory for the mari time mobile service and for correspondence between ships, aircraft and survival craft stations.

Communication with the ship's side
Distress messages between ships
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No regulations in the instruction manual shall prevent a coast station in extraordinary circumstances, from using any means available to give assistance to a distressed mobile station. Distress signals and distress messages must only be transmitted on the direct orders of Master the Psychology of Selling Your Boat: Essential Tips and Techniquesthe master or the officer in charge. Distress signals and distress messages must be transmitted on the following frequencies designated for distress, urgency and safety communications on radiotelephony:

  • 156,8 Mhz – channel 16;
  • 2 182 kHz;
  • 4 125 kHz;
  • 6 215 kHz;
  • 8 291 kHz;
  • 12 290 kHz;
  • 16 420 kHz;

The two most commonly used are VHF channel 16 and MF 2 182 kHz. In distress situations, speech and radiotelephony must be as slow and clear as possible. If language problems should occur, the phonetic alpha­bet and the “International Signalbook 1969” can be used.

The international distress and callins frequency 2 182 kHz

The 2 182 kHz frequency is the international radiotelephony distress fre­quency, and shall be used for this purpose by ship stations, aeromobile stations and survivor craft stations working on the MF frequency band.

Read also: Digital Selective Calling-DSC During Disasters or Emergencies

This frequency may be used for distress calls and distress traffic, urgency signals and urgency messages, and the Emergency Preparedness: The Role of EPIRBs and SARTs in Maritime Safetysafety signal.

Otherwise, the 2 182 kHz frequency can be used for calling and replying to calls.

All coast stations open for public correspondence on MF telephony, shall keep listening watch on 2 182 kHz (consult List of Coast Stations for further information). Ship stations shall, when not engaged in traffic, maintain listening watch on 2 182 kHz.

Silence periods

To increase the safety of lives at sea, it is of vital importance that all ships make every attempt to listen to the Importance of Reliable Marine Communications and Empowering Maritime Industryinternational distress frequency during the silence periods. The silence periods are the first 3 minutes of every hour and half hour (from xxOO hours to xx03 hours and from xx30 hours to xx33 hours). During these three minutes, all transmission on 2 182 kHz must cease, with the exception of distress or urgency traffic.

Ships fitted with MF radio installations, shall keep listening watch by means of a watch receiver in the wheel house.

The radiotelephony alarm signal

The radiotelephone alarm signal consists of two substantially sinusoidal audio frequency tones transmitted alternately. One tone shall have a frequency of 2 200 Hz and the other tone a frequency of 1 300 Hz, the duration of each tone being 250 milliseconds.

When generated by automatic means, the radiotelephone alarm signal shall be transmitted as continuously as possible over a period of at least 30 seconds, but not exceeding one minute.

When generated by other means, the signal shall be transmitted as continuously as possible for a period of approximately one minute. The purpose of the alarm signal is to attract the attention of a person on watch or to actuate automatic devices sounding the alarm or activating a silenced loudspeaker for the message which will follow.

The distress signal – MAYDAY

The distress call shall have absolute priority over all other transmissions.

All stations hearing it shall immediately cease any transmission capable of interfering with the distress traffic and shall continue to listen to the frequency used for the emission of the distress call. This call shall not be addressed to a particular station, and acknowledgement of receipt shall not be given before the distress message which follows it is sent.

Fire ship
A fireboat ready to put out a fire at any moment
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The distress call and message shall only be transmitted on the authority of the master or the person responsible for the ship, aircraft or other vehicle carrying the mobile station or ship-earth station.

The radiotelephone distress signal consists of the word MAYDAY a derivative of the French word “M’ AIDER”. The distress signal indicates that a ship, aircraft or other vehicle is threatened by grave and imminent danger and requests immediate assistance.

The distress call

The radio telephony distress call consists of:

  • The distress signal MAYDAY, spoken three times;
  • The words THIS IS (or DE spoken as DELTA ECHO in case of language difficulties);
  • The callsign or other identification of the mobile station in distress, spoken three times.

The distress message

The distress message consists of:

  • The distress signal MAYDAY;
  • the name, or other identification, of the mobile station in distress;
  • particulars of its position;
  • the nature of distress and the kind of assistance required;
  • any other information which might facilitate the rescue.

As a general rule, the ship shall signal its position in latitude and longitude, using figures for degrees and minutes, together with one of the words NORTH or SOUTH, and one of the words EAST or WEST.

The distress message, preceded by the distress call, shall be repeated at intervals, especially during the periods of silence mandatory in radiotelephony, until an answer is received.

Acknowledgement of receipt of a distress message

Ship stations receiving a distress message from another mobile station which is, beyond any possible doubt, in their vicinity, shall immediately acknowledge receipt.

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However, in areas where reliable communications with one or more coast stations are practicable, ship stations should defer this acknowledgement for a short interval so that a coast station may acknowledge receipt.

In telephony, acknowledgement of the receipt of a distress message shall be given in the following form:

  • MAYDAY;
  • the call sign or other identification of the station sending the distress message, spoken three times;
  • the word THIS IS (or DE, pronounced as DELTA ECHO in case of language difficulties);
  • the call sign or other identification of the station acknowledging receipt, spoken three times;
  • the words RECEIVED (or RRR pronounced as ROMEO ROMEO ROMEO) in case of language difficulties;
  • the distress signal MAYDAY.

Any mobile station acknowledging receipt of a distress message shall, on the order of the master or person responsible for the ship, aircraft or other vehicle, transmit the following information as soon as possible:

  • its name;
  • its position;
  • the speed at which it is proceeding towards the mobile station in distress, and the approximate time it will take to reach it;
  • additionally, if the position of the ship in distress appears doubtful, ship stations should also transmit, when available, the true bearing of the ship in distress.

Distress traffic

In distress traffic, the distress signal (MAYDAY) shall be sent before the call and at the beginning of the preamble of any telegram.

The station in distress or the station in control of distress traffic may impose silence either on all maritime mobile service stations in the same area, or on any stations which interfere with the distress traffic. Such instructions shall be addressed “to all stations“, or to one station only, according to circumstances.

Example:

  • MAYDAY;
  • ALL STATIONS;
  • SEELONCE MAYDAY.

Wherever necessary, any maritime mobile service station near the ship, aircraft or other The Global Maritime Distress and Safety System – Principles & Practicevessel in distress, may impose silence. This is done in the following way:

Example:

  • MAYDAY;
  • ALL STATIONS;
  • SEELONCE DISTRESS;
  • THIS IS;
  • OWN CALLSIGN OR IDENTIFICATION.

When complete silence is no longer necessary on a frequency being used for distress traffic, the station controlling the traffic shall transmit a message addressed to all stations indicating that restricted working may be resumed.

  • MAYDAY;
  • ALL STATIONS, sent three times;
  • THIS IS;
  • the call sign or other identification of the station sending the message;
  • the time the message was submitted;
  • the name and the callsign of the mobile station which was in distress;
  • the word PRU-DONCE.

The same message as above, but indicating that normal working can be resumed:

  • MAYDAY;
  • ALL STATIONS, sent three times;
  • THIS IS;
  • the call sign or other identification of the station sending the message;
  • the time the message was submitted;
  • the name and call sign of the mobile station which was in distress;
  • the words SEELONCE FEENEE.

Transmission of a distress message by a station not itself in distress

Any mobile station, or land station learning that a mobile station is in distress, shall transmit distress messages in any of the following cases:

  • when the station in distress is not itself in a position to transmit the distress message;
  • when the master or person responsible for the ship, aircraft or other vehicle not in maritime distress, or the person responsible for the land station, considers that further help is necessary;
  • when an unacknowledged distress message is heard, and one is not in a position to render assistance.

In such cases, Ship’s Antennas Systems and Radio Wave Propagationthe transmission of the distress message shall always be preceded by the call indicated below, which shall itself be preceded when ever possible by the radiotelephone alarm signal.

MAYDAY RELAY, spoken three times:

  • the words THIS IS (or DE pronounced as DELTA ECHO in case of language difficulties;
  • the call sign or other identification of relaying station, spoken three times;
  • the following received from CALLSIGN or IDENTIFICATION of station station in distress on YYYY kHz time ZZZZ UTC;
  • followed by the correct repetition of the received distress message.
Author
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Literature
  1. Global Maritime Distress and Safety System: IMO 1987.
  2. Manual for use by The Maritime Mobile and Maritime Mobile- Satellite Services: ITU 1992.
  3. Radio Regulations 1-2-3: ITU 1990.
  4. Manual for Norwegian Mobile Radiotelephone Stations: The Norwegian Telecom 1992.
  5. Modem Electronic Communication: Gary M. Miller 1978.
  6. Brochures and data sheets from manufacturers of GMDSS Equipment.
  7. Inmarsat: Inmarsat-A User’s Manual, Inmarsat-C User’s Manual.
  8. Nodposisjonering: Bjomar Augdal, 1992.
  9. Skipsantenner: Bjomar Augdal 1991.
  10. COSPAS-SARSAT Secretariat: COSPAS-SARSAT System Data Documents.
  11. Admiralty List of Radio Signals.
Footnotes
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