Commandant (G-TTM) U.S. Coast Guard 26 May 1995 Washington DC 20593 Maritime Mobile Service Identities (Adapted from Appendix 43 of the International Telecommunications Union Radio Regulations) Maritime Mobile Service Identities are formed of a series of nine digits which are transmitted over the radio path 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 principally to call ships automatically. There are four kinds of maritime mobile service identities: a. Ship station identities, b. Group ship station identities, c. Coast station identities, d. Group coast station identities. Maritime Identification Digits (MID) A single MID has been allocated to each country. A second MID can be assigned once the MID first or subsequently allocated 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 provided in table 1 to Appendix 43 of the ITU Radio Regulations. Ship Station Identities The 9-digit code constituting a ship station identity is formed as follows: MIDXXXXXX wherein MID represent the Maritime Identification Digits and X is any figure from 0 to 9. Group Ship Station call Identities Group ship station call identities for calling simultaneously more than one ship are formed as follows: 0MIDXXXXX 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 Coast station identities are formed as follows: 00MIDXXXX 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 Group coast station call identities for calling simultaneously more than one coast station are formed as a subset of coast station identities, as follows: 00MIDXXXX where the first two figures are zeros and X is any figure from 0 to 9. In the U.S., federal MMSIs are assigned by the National Telecommunications and Information Administration, and are normally, but not always, formed as 3669XXXXX. Non federal MMSIs are assigned by the Federal Communications Commission as part of the ship station license application (Form 506), and are formed as 366XXX000 for ships on international voyages, or 366XXXXX0 for all other ships. The U.S. Coast Guard group ship station call identity is 036699999, and group coast station call identity is 003669999. In the U.S., MMSIs are primarily used for digital selective calling and for assigning Inmarsat identities. See the file DATA.TXT. Assignment of Ship Station Identification (adapted from ITU-R Recommendation M.585-2) Restrictions may apply with respect to the maximum number of digits which can be transmitted on some national telex and/or telephone networks for the purpose of ship station identification. At present, the maximum number of digits that are transmitted that are able to be transmitted over the national networks of many countries for the purpose of determining ship station identity is six. The digits carried on the network to represent the ship station identity is referred to as the "ship station number" in this text and in the relevant ITU-T Recommendation. The use of the techniques described below should make it possible for the coast stations of such countries to engage in the automatic connection of calls to ship stations. To obtain the required nine digit ship station identity a series of trailing zeros is added to the ship station number by the coast station for shore-originated automatic services, e.g.: Ship station number Ship station identity MIDXXX MIDXXX000 As long as the restrictions above apply in one's own network limiting ship station numbers to 6 digits, ships that intend to receive automatic network traffic from national coast stations only, should be assigned identities wherein X(9), but not X(8), =0. This assumes that "9" is used to abbreviate the national MID for such ships for network purposes. Ship station number Ship station identity 9XXXXX MIDXXXXX0 As long as the restrictions above apply it may be useful for some administrations to expand the capacity for numerical ship station identification by using as many as ten "8Y" abbreviations for MIDs. Such a technique may allow the assignment of ship station identities wherein trailing zeros are applied only to X(8) and X(9). Ship station number Ship station identity 8YXXXX MIDXXXX00 The usefulness of this technique to a given administration may depend on whether its abbreviation (e.g. 83) of its own MID is duplicated in other administrations in which some of its ships have a community of interest. When such is the case the ship in question can be called using the same ship station number in all the automatic networks of interest to that ship. As an example, a group of up to ten countries, with community of interest, might agree to assign the same abbreviation for their respective MIDs. The abbreviation should always relate to the numerically lowest MID, when more than one is assigned to a given country. Country "8Y" Assignment A 80 B 81 C 82 D 83 E 84 F 85 G 86 H 87 I 88 J 89 All countries recognize a particular 8Y abbreviation as associated with a particular country. For example a coast station in any of the countries A-J receiving "83" as the first two digits of a ship station number would transmit the MID of the country D. As long as the restrictions described above apply, ships that reply regular automatic communications from foreign coast stations additional to those that may conform to the abbreviation arrangements above shall only be assigned ship station identities with X(7)X(8)X(9) = 000 to support 6 digit ship station numbers. When it becomes necessary to progress to stage 2, (seven digit ship station numbers for automatic shore-originated traffic) in the ship station identity scheme the format of ship station identities described in the previous paragraph would change from MIDXXX000 to MIDXXXX00. If "8Y" abbreviations are used in stage 1 (six digit ship station numbers for automatic shore-originated traffic) some ship station identity assignments will already have taken the MIDXXXX00 format. It would therefore be useful to reserve at least one value in the X(7) digit position if ship station identity assignments are made on the basis of "8Y" network abbreviations: Ship station number Ship station identity 8YXXXX MIDXXXX00 Because all ships on international voyages, as well as all ships fitted with an Inmarsat B, C or M ship earth station, are assigned MMSIs of the format MIDXXX000, a serious problem has arisen internationally in assigning sufficient numbers of MIDs to all administrations that need them. For example, a country having 10,000 Inmarsat-equipped ships would require 10 MIDs just to accommodate those 10,000 ships. If 50,000 boaters decided to fit small Inmarsat M or C terminals, 50 additional MIDs would be required to accommodate them. The problem exists with Inmarsat-equipped ships because ITU-T recommendations require that Inmarsat ship earth stations be assigned the identity (MESIN) TMIDXXXYY, where T indicates the type of Inmarsat station, YY indicates the Inmarsat station extension (e.g. "00" might indicate a telephone in the bridge, "01" might indicate a fax machine in the radio room, etc), and MIDXXX indicates the ship station number, which relates to the assigned ship station identity MIDXXX000. The MMSI was meant to be an all-inclusive ship electronic identity, used in one form or another by every GMDSS or telecommunications instrument on the ship. It is doubtful however that the MMSI can in practice totally fulfill that role. ITU is now considering ending the practice of relating Inmarsat MESIN identities with the ship MMSI identity. For more information on Inmarsat MESIN and other electronic identities, see the file DATA.TXT.