MMSI

A Maritime Mobile Service Identity is a unique nine-digit number assigned to a ship station, coast station, or group, defined in ITU-R M.585 and administered nationally. The first three digits are the Maritime Identification Digits that identify the flag administration. The MMSI is the address used by DSC and AIS to identify and call a specific station; a coast station MMSI begins with two leading zeros, and a group call begins with a single zero. It is programmed once into the radio and AIS and changed only on a change of flag or ownership.