Maritime Mobile Service Identity

A Maritime Mobile Service Identity (MMSI) is a series of nine digits which are sent in digital form over a radio frequency channel in order to uniquely identify ship stations, ship earth stations, coast stations, coast earth stations, and group calls. These identities 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 ships automatically.

There are now six kinds of maritime mobile service identities:

An MID consists of three digits, always starting with a number from 2 to 7 (assigned regionally). A second MID can be assigned once the first or subsequently allocated MID is more than 80% exhausted, and the rate of assignments is such that 90% exhaustion is foreseen. A listing of MIDs assigned to each country is written in Table 1 of ITU Radio Regulations Appendix 43.

The initial digits of an MMSI categorize the identity, as defined in by Recommendation M.585. The meaning of the first digit is:

The 9-digit code constituting a ship station identity is formed as follows:

where MID represent the Maritime Identification Digits and X is any figure from 0 to 9. If the ship is fitted with an Inmarsat B, C or M ship earth station, or it is expected to be so equipped in the foreseeable future, then the identity should have three trailing zeros:

If the ship is fitted with an Inmarsat C ship earth station, or it is expected to be so equipped in the foreseeable future, then the identity could have one trailing zero:

If the ship is fitted with an Inmarsat A ship earth station, or has satellite equipment other than Inmarsat, then the identity needs no trailing zero.

Group ship station call identities for calling simultaneously more than one ship are formed as follows:

where the first figure is zero, and X is any figure from 0 to 9. The particular MID represents only the country assigning the group ship station call identity and so does not prevent group calls to fleets containing more than one ship nationality.

Coast station identities are formed as follows:

where the first two figures are zeros, and X is any figure from 0 to 9. The MID reflects the country in which the coast station or coast earth station is located.

Group coast station call identities for calling simultaneously more than one coast station have the same format as individual coast station IDs: two leading zeros, the MID, and the four digits. They are formed as a subset of coast station identities, as follows:

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