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What is a MMSI?

Maritime mobile service identity (MMSI) is a means of identification for ship stations, ship earth stations, coast stations, coast earth stations, and other non-shipborne stations operating in the maritime mobile service or the maritime mobile-satellite service, and group calls. It is formed of a series of nine digits including maritime identification digits (MID) and transmitted over the radio path. In accordance with RR19.111 administrations shall follow Annex 1 of Recommendation ITU R M.585 6 concerning the assignment and use of maritime mobile service identities.

How is an MMSI formed for a ship station?

The nine digit unique ship station identity is in the format MIDXXXXXX where in the first three digits represent the Maritime Identification Digits (MID) and X is any figure from 0 to 9, as indicated in Recommendation ITU-R M.585. The MID denotes the administration having jurisdiction over the ship station so identified.

How is an MMSI formed for a coast station?

​Coast stations and other stations on land participating in the maritime radio services should be assigned a nine-digit unique coast station identity in the format 00MIDXXXX where the digits 3, 4 and 5 represent the MID and X is any figure from 0 to 9, as indicated in Recommendation ITU-R M.585.
The MID reflects the administration having jurisdiction over the coast station or coast earth station.

How is an MMSI formed for Search and Rescue (SAR) aircraft?

When an aircraft is required to use maritime mobile service identities for the purposes of search and rescue operations and other safety-related communications with stations in the maritime mobile service, the responsible administration should assign a nine-digit unique aircraft identity, in the format 111MIDXXX where the digits 4, 5 and 6 represent the MID and X is any figure from 0 to 9, as indicated in Recommendation ITU-R M.585.
The MID represent the administration having jurisdiction over the aircraft call identity.

How is an MMSI formed for AIS Aids to Navigation (AtoNs)?

When a means of automatic identification is required for a station aiding navigation at sea, the responsible administration should assign a nine-digit unique number in the format 99MIDXXXX where the digits 3, 4 and 5 represent the MID and X is any figure from 0 to 9, , as indicated in Recommendation ITU-R M.585.
The MID represent the administration having jurisdiction over the navigational aid.

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