DSC is used to establish initial contact between stations. Following an alert by DSC, communications are normally carried out by radiotelephone or Narrow Band Direct Printing (NBDP - radio telex). DSC can be considered as a replacement for the radiotelephone and radiotelegraph (Morse) alarm signals. Rather than just indicate that the sending station is in distress, the DSC system allows a great deal more information to be transmitted, including:
The priority of the call - DISTRESS, URGENCY, SAFETY or ROUTINE;
The address - ie: all ships or a single ship/station;
The identification of the ship in distress;
The position of the ship in distress; and
The nature of the distress.
A DSC message will trigger an audio alarm and the procedure will then be to switch to a designated voice channel for further action. Aural alarms for reception of HF distress messages, including relays, sound only if the distress position is within 500 nautical miles of the receiving ship's position .
DSC Channels
The International Telecommunications Union (ITU) has allocated a DSC distress and safety channel in the MF, each of the HF and the VHF marine radio bands. These are:
MF/HF DSC - DISTRESS AND SAFETY CHANNELS
2187.5 4207.5 6312.0 8414.5 12577.0 16804.5 (kHz)
VHF DSC - DISTRESS AND SAFETY CHANNEL
VHF Marine Channel 70
( Voice transmissions are PROHIBITED on the DSC channels)
The MF/HF channels are restricted to distress, urgency and safety traffic only because of the relatively low speeds of transmission of 100 baud. If too many calls were permitted on the MF/HF channels, the channels would quickly become overloaded to the point where a distress call may be blocked.
VHF DSC operates at 12 times the speed of MF/HF - accordingly, all priorities of call are allowed on the VHF channels.
The ITU has also allocated a suite of HF channels dedicated to DSC commercial operations.
DSC Call Categories
The DSC system supports a number of call categories. These categories mirror the standard maritime prioritisation of message traffic, ie: DISTRESS, URGENCY, SAFETY & ROUTINE. Distress alerts are automatically addressed to all stations. Urgency, safety and routine calls can be addressed to all stations, an individual station, or a group of stations.
Maritime Mobile Service Identities (MMSI)
All DSC equipment is programmed with a unique nine digit identification number, known as a Maritime Mobile Service Identity (MMSI). The MMSI is sent automatically with each and every DSC transmission made.
Maritime Identification Digits (MID)
The first three digits of the MMSI are known as the Maritime Identification Digits (MID). The MID represents the country of registration of the vessel, or the country in which the DSC shore station is located. MID's are allocated on an international basis by the ITU, in much the same way as a callsign prefix.
Formation of MMSI's
MMSI's allocated to merchant vessels are normally allocated with three trailing zero's. Those allocated to recreational craft have two or one trailing zero, and Coast Station MMSI's are formed with two leading zero's. For example:
Typical Australian merchant vessel MMSI- 503001000
where:
503 is the Australian MID;
and 01000 is the individual ship number
Typical Australian recreational vessel MMSI - 503000100
where: 503 is the Australian MID; and 000100 is the individual ship number
Coast Station MMSI - 005030001
where:503 is the Australian MID; and 0001 is the individual Coast Station number
More Information
The ITU web site has more information about DSC (http://www.itu.int/home/)
The Problem
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| Prevention
Keep a working carbon monoxide detector on board the vessel. In Australia First Alert, the market leading fire safety brand, has introduced a portable battery-operated detector that allows users to move the unit around the boat at will, and is available at major hardware retailers. For enquiries call 03 9538 9228.
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Safety while sailing is such a huge topic that it cannot be fully examined here. However, there are a number of useful hints and tips that have been found useful by experienced sailors. The hints are of a general nature – more to establish the safety-conscious frame of mind. Although they are more applicable to larger vessels many are relevant for the dinghy sailor. The list is by no means exhaustive and other avenues should be explored to provide the best practicable level of safety for all those on board.
1. Never assume that the vessel you are traveling on is totally seaworthy. If you see something apparently out of order bring it to the attention of the skipper or at least another crew member.
2. Move around on a boat under sail with caution – always have one hand for the boat and the other for yourself. As skipper make sure all on board understand what is safe and secure to hold and what is not.
3. Continually plan ahead and expect the unexpected. Sod’s law works all the time on most boats. It says that “when something can go wrong it will and always at the worst time.”
4. Be weather conscious – in a sailing vessel you will not often be in a position to run away from the nasty weather. The corollary is that you should know what it takes to best prepare the vessel for the encounter – especially as skipper.
5. Know the limitations of your vessel and all the crew – even for local recreational activities in benign conditions. Use the right techniques for crossing bars.
6. Don’t allow crew to expose themselves unnecessarily to potential danger – such as the height of the boom to leeward. Crew should move forward and aft along the windward side of a vessel under sail whenever possible.
7. Ensure all on board wear appropriate clothing and footwear – having warm and waterproof gear – especially for longer voyages.
8. Ensure crew have a basic understanding of navigational marks and collision avoidance regulations.
9. As a skipper know how to use all equipments on the boat as well as their detailed capabilities and limitations.
10. As skipper ensure a decent range of tools and spares is carried.
11. As skipper ensure all crew on board are briefed of the safety equipment carried, the safety rules to be followed, the location and sometimes the use of important items. For such a briefing to be thorough the crew needs to understand what will have to be done if the skipper falls overboard or is otherwise incapacitated - say by a heart attack. MOB procedures should be well understood as should basic use of radio, engine, electrics and sails.
12. Organise a safety watch with either an established agency of someone on shore. Minimum facts to be passed are vessel description, number on board (POB), sailing intentions / area and expected time of return.
13. Check presence, condition & currency of emergency equipment before departure – Life Jackets, Communications, Flares, V Sheet, EPIRB, Life Raft etc.
14. Have at least one set of safety harness readily available.
15. Seek advice and information before entering unfamiliar waters – particularly close to shore. This includes crossing barred entrances for the first time.
16. Become as well informed as possible before undertaking new activity – e.g. night sailing in unfamiliar waters or entering a mooring area for the first time.
17. When inexperienced crew are given control they must be closely and continually monitored from a position where control can be quickly resumed.
18. It is in the interests of all on board to be as knowledgeable and skillful as possible. Therefore the skipper should encourage all crew to try various skills under supervision. Attempts to develop good crew coordination should be encouraged – a sense of satisfaction comes to most people in this way. However patience will often be required for those with either little experience or natural aptitude. The skipper should politely but firmly correct wrong actions or concepts as they arise.
19. Where time permits pass on basic rope skills – e.g. a few basic commonly used knots and how to hold and manipulate a line under tension.
20. Keep the crew informed of future intentions and do not carry out tacks, jibes or other abrupt manoeuvres without appropriate warning to those both on and below deck.
21. When the skipper goes below for all but a short period instructions should be given to the helmsman – they may be very brief or very detailed if the absence is to be a long one.
22. On long voyages establish a proper watch system.
These funds are used by Coastal Patrol to maintain its free Search and Rescue services to the boating public. Being a member of MRSS helps Coastal Patrol to help you.
Membership of MRSS has other benefits too. Coastal Patrol provides marine education and training on boating and related subjects such as Seamanship, Basic and Coastal Navigation, Seaman's Meteorology, First Aid and Marine Radio. Cost of these courses is reduced by 10% to financial members of MRSS.
These details are recorded and remain 'active,' until you return and log off. If you do not log off or call in to tell us you are safe the Coastal Patrol begins a search to determine whether you need help. You can call in at any time to vary your estimated time of return. If requested, the Coastal Patrol will call your family to tell them the fish are biting and you will be staying out longer, or to pass along other important messages. As well, you can call in at any time to obtain an update on the weather; the latest Bureau of Meteorology forecast is always at hand at the base or you may want details of tidal information. Coastal Patrol broadcasts weather warning information as soon as it is received by fax from the Weather Bureau.
While you are 'logged on' Coastal Patrol is on standby. Coastal Patrol bases operate at different times. Therefore the boat owner should contact the nearest Coastal Patrol base for operating hours. This base will also send out a membership form for new members and provide advice on the appropriate use of both 27Mhz and VHF radios. When returning a membership form it will usually be a good idea to include a colour image of the vessel - to allow easier provision of assistance in case of trouble.
