Maritime Mobile Service Identities (MMSIs) are nine-digit numbers used by maritime digital selective calling (DSC), automatic identification systems (AIS) and certain other equipment to uniquely identify a ship or a coast radio station. MMSIs are regulated and managed internationally by the International Telecommunications Union in Geneva, Switzerland, just as radio call signs are regulated.
If you have a marine radio with DSC capability, you must obtain a nine-digit maritime mobile service identity number, and have it programmed into the unit before you transmit. Each vessel requires only one MMSI number.
An MMSI is vital data point for both domestic and international emergency personnel. Maintaining updated and accurate data in your license record is critical to ensuring maritime safety. To update a license record, please file an application in ULS to maintain the accuracy of your vessel’s information.
MMSI Numbers are:
Required to be programmed into radios with Digital Selective Calling (DSC) capability
Entered into AIS (Automatic Identification System) transceiver
Should be used for all INMARSAT B/C/M terminals
The system is comprised of a series of nine (9) digits which are transmitted over the radio path to uniquely identify ship stations, ship earth stations, coast stations, coast earth stations and groups of stations. The first three digits of an MMSI indicate the issuing country.
MMSI numbers may only be used for one vessel and may not be re-used, unless in the special case of a vessel transfer (please see the Vessel Transfer Tab).
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