AIS - Automatic Identification System - When the Man Overboard Beacon (MOB) is activated, an emergency symbol  instantly appears on the AIS enabled units of all ships in range (line of sight),  including ECDIS (Electronic Chart Display and Information System) , Chart  Plotters, and Radars. 

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DSC- Digital Selective Calling- Emergency broadcast to your VHF radio.  Requires MMSI Number