Maritime Mobile Service Identities (MMSI) numbers are nine-digit numbers used by Marine DSC radios, Automatic Identification Systems (AIS) and certain other equipment to uniquely identify a ship or a coast station. This number is used like a telephone number to selectively call other similarly equipped radios. In the USA, the MMSI number begins with one of the following sets of three numbers (which are Maritime Identification Digits or MID): 366, 367 (both issued by the FCC), or 338 (issued by Boat US, Sea Tow or US Power Squadron). A table of MID’s can be found HERE.
It is important to stress the requirement for a MMSI number to be entered in each radio. If this number is not entered, no DSC calls can be made or answered, but more importantly, DISTRESS CALLS ARE DISABLED!