EPIRB

An EPIRB or Emergency Position Indicating Radio Beacon, is a distress beacon used by mariners worldwide to alert Search and Rescue (SAR) forces that they are in distress. EPIRBs transmit a 406 MHz distress signal that contains a unique 15 digit identification number to the Cospas-Sarsat Satellite System (which is a government run system so there are no subscription fees). Search and Rescue forces then pull up your beacon registration (mandatory of all EPIRB owners) which tells them who the beacon belongs to as well as provides additional emerency contact information. EPIRBs provide Search and Rescue forces with your location either via GPS data if your EPIRB is equipped with a GPS receiver, or via triangulation from the low earth orbiting satellites.