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VOL. 11 NO. 11
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Digital Selective Calling 101

What to know about DSC-VHF marine radios, MMSI numbers

Digital Selective Calling 101

In an on-the-water emergency, calling for help using a Digital Selective Calling VHF marine radio gives rescuers critical GPS location information, making it the best way to call for assistance. But you need to keep a few things in mind when buying or selling a boat with a DSC-VHF radio aboard.

MMSI numbers stay with the boat
DSC-VHF radio-equipped vessels must be registered and issued a Maritime Mobile Service Identity number, which is then entered into the radio. Unlike a phone number that stays with you when you move across town, an MMSI number always stays with the boat, so subsequent owners must update the MMSI number with his or her new contact information. To make this easier, print a copy of your MMSI certificate, write down your registration login name and password, and keep it in a safe place. This makes managing your boat’s MMSI number easier if registration details change or your boat is sold to a new owner.

Handheld DSC-VHF radios should stay with the boat
Some boaters have both fixed-mount and hand-held DSC-VHF marine radios aboard that share the same MMSI number. When selling, it’s wise to include any hand-held DSC-VHFs in the purchase and not take them with you to the new vessel. It would be dangerous to have the same MMSI being used by more than one vessel, and hand-held DSC-VHF radios often need to be sent to the manufacturer for a factory reset before they can be updated with a new MMSI number, a time-consuming process.

Using DSC-VHF marine radios in international waters
It’s OK to use your DSC-VHF radio for communications when transiting foreign waters. Once you communicate with or enter a foreign port, however, a U.S.-registered boat must have a federal Ship Station License issued by the Federal Communications Commission, which also provides an appropriate internationally accessible MMSI number as part of the $220 10-year Ship Station License fee. Receiving an MMSI from the FCC means that your emergency contact information goes into an internationally accessible database (also accessible to the U.S. Coast Guard), which could speed a foreign rescue. MMSI numbers not issued by the FCC are only entered into the USCG database used for domestic waters.

The differences between DSC-VHF radio and AIS
DSC-VHF radio and Automatic Identification System don’t share anything except the vessel’s MMSI number. Each system has a completely different process to follow when buying and selling a boat, or when changing a boat’s name (an AIS requirement).

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