Теңіз кемелері үшін цифрлық радио идентификациялық коды

Digital radio identification code for marine stations
A Maritime Mobile Service Identity (MMSI) is effectively a maritime object's international maritime telephone number, a temporarily assigned UID issued by that object's current flag state (unlike an IMO number, which is a permanent global UID). 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. 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 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.

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 can be found in Table 1 of ITU Radio Regulations Appendix 43.

In the United States (one of whose MIDs is 366), 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 normally as part of the ship station license application, and are formed as 366xxx000 for ships on international voyages and ships needing an Inmarsat mobile earth station, or 366xxxxx0 for all other ships. The United States 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.

Because all ships on international voyages, as well as all ships fitted with an Inmarsat B 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 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. Questions have been raised, however, whether the MMSI can in practice totally fulfill that role. ITU may eventually end the practice of relating Inmarsat MESIN identities with the ship MMSI identity. To help mitigate against MMSI number exhaustion, manufacturers are required to cripple DSC capable radios so that an MMSI number can only be entered once, which means that a device owner cannot move the radio from one boat to another. This is especially egregious for hand held VHF devices, for which a single MMSI number makes little sense. The World Radio Conference, Geneva, 1997 (WRC 97), adopted Resolution 344 concerning the exhaustion of the maritime mobile service identity resource. In view of improvements to public switched telephone networks, and new capabilities of the Inmarsat system other than Inmarsat B or M, previous restrictions should no longer be applicable. All nine digits of the MMSI can be used in such cases, and no longer need to end in trailing zeros.