Megahertz (1 000 000 hertz). A measurement unit of radio frequency, oscillation and vibration, equaling 1 000 000 cycles per second.
Minimum Keyboard and Display. A minimal text only display provided for AIS Class–A transceivers.
Mobile Packet Data Service. An Inmarsat service allowing continuous connection of ships to terrestrial networks with payment for volume of data exchanged, rather than the duration of ‘airtime’ used.
Marine Radio Operator’s Certificate of Proficiency. Replaced by Long Range Operator Certificate of proficiency.
Maritime Safety Committee of the IMO.
Maritime Safety Information. Navigational and meteorological warnings, meteorological forecasts and other urgent safety related messages.