MMSI Numbers Flashcards

What is the MMSI of a vessel whose number starts with '338'?

Answer: A US-registered vessel (MID 338)

The MID 338 identifies vessels registered in the United States. Each country is assigned specific MID ranges by the ITU, and 338 is one of the US allocations. This allows any coastguard to immediately identify the flag state from an MMSI.

What is the difference between MMSI, call sign, and vessel name in radio procedures?

Answer: MMSI is for DSC digital calls; call sign and vessel name are both used in voice communications

In radio procedure, the vessel name is used in voice MAYDAY calls and routine conversations. The call sign is the official alphanumeric identifier used in voice communications. The MMSI is the nine-digit number used exclusively in DSC digital communications.

Can an MMSI be reused after a vessel is decommissioned?

Answer: No, Ofcom policy is that MMSIs are not reused to prevent database confusion

MMSIs are not reused after a vessel is decommissioned or the licence is cancelled. This prevents confusion in SAR databases where an old MMSI might still be associated with historical vessel data.

What action should be taken if a DSC radio is stolen from a vessel?

Answer: Report the theft to Ofcom and request MMSI cancellation to prevent fraudulent use

A stolen DSC radio with a programmed MMSI could be misused to send false distress alerts. The owner should report the theft to Ofcom to cancel the MMSI and update the SAR database to flag the number as invalid.

What does it mean when a DSC radio displays an unrecognised MMSI in an incoming call?

Answer: The calling vessel's MMSI is not in the local database — this is normal as databases are not comprehensive

VHF DSC radios typically cannot look up vessel names from MMSIs on their own — only coast stations have full database access. An unrecognised MMSI simply means the number is not stored in the radio's limited memory.

What does the term 'ship station' mean in radio licensing?

Answer: Any vessel carrying radio equipment that is required to hold a Ship Radio Licence

In Ofcom licensing terms, a 'ship station' is any vessel (including recreational boats) that carries radio transmitting equipment. All ship stations must hold a valid Ship Radio Licence from Ofcom to operate legally.