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Digital Selective Calling (DSC) And Maritime Mobile Service Identity (MMSI Number)

Your VHF radio equipped with Digital Selective Calling (DSC) is an important piece of safety equipment on board your vessel. Having your MMSI number registered with the appropriate agency is also an essential part of your Safety Management System. DSC allows the radio to transfer information digitally, not just by voice, and to instantly send a digital distress alert to the Coast Guard.

Part of that alert is a nine-digit Maritime Mobile Service Identity (MMSI) number that identifies your vessel. The MMSI number is a bit like a phone number for your boat, and all DSC capable equipment (including AIS units) associated with the specific vessel should use the same MMSI number, since the MMSI serves to identify the vessel, not the equipment. If you sell your boat, the MMSI number is normally transferred with it. Without an MMSI, the digital functions on a DSC-equipped VHF radio will not function.

The MMSI number must be registered in a database that is relayed to the Coast Guard for use in Search and Rescue. DSC-equipped radios also need to be interfaced with a GPS when they are installed so that your position will be sent with the emergency message in a distress situation. If the vessel already has an MMSI number you will need to update the old license with new owner’s details. This is very important, as you can’t change the radios electronic MMSI number, which is particular to the set and the vessel. It can’t be changed! You will need to renew the vessels license with your names, the vessels home port and any new registration number.

Should you ever contact another vessel or the Coastguard by VHF the other persons VHF will display your MMSI number. As long as their set is DSC (Digital Selective Calling). They will also see your position displayed on their set as your latitude and longitude is shown off your GPS / chart plotter as they are connected to each other. The Coastguard will see info such as your names, the boats name, your port of registration, vessel description etc that you filled in on the forms.

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Learn more about what other safety equipment you might need, so you can manage potential risks aboard your vessel. Check out Ocean Time Marine’s interactive Forms and Checklists.

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