Maritime Mobile Service Identity
| Acronym | MMSI |
|---|---|
| Organization | International Telecommunication Union |
| Introduced | 1982 |
| No. of digits | 9 |
| Example | 311001109 |
A Maritime Mobile Service Identity (MMSI) is an assigned Unique identifier (UID), comparable to a maritime object's international maritime telephone number, issued by that object's current flag state (unlike an IMO number, which is a permanent global UID). When the vessel changes ownership or name within the same country of registration then the assigned MMSI remains with the vessel. If the ship is reflagged then the different country’s (flag state) MMSI must be assigned.
An MMSI comprises a series of nine digits, consisting of three Maritime Identification Digits (country-codes), concatenated with a specific identifier. Whenever an object is re-flagged, a new MMSI must be assigned that corresponds with the new state's identity.
A "maritime object" could be anything that requests an MMSI identifier.—e.g., a vessel, fixed offshore installation, mobile unit, maritime aircraft, coast station, etc. Communications may be routed to "individual objects" or to "groups of objects". A group call to objects can be based on an object's locale, owner/operator/fleet, type, etc. or combinations thereof.
MMSI's are formed in such a way that the identity or part thereof can be used by telephone and telex subscribers connected to the general telecommunications network to call any of these objects automatically. Communications are sent in digital form over a radio frequency channel.