Epirb

Another very important aid to one – way radio communication is the EPIRB.
EPIRB stands for Emergency Position Indicating Radio Beacon.
The EPIRB transmits the distress alert to a satellite.
The satellite locates the EPIRB’s position and relays the information to a Land Station, and in turn the Land Station relays the information to a rescue coordination center.
EPIRBs contain an optional 121.5 MHz homing beacon.
This homing device facilitates Search and Rescue Helicopters with VHF direction finders.
The EPIRB is also fitted with a hydrostatic release unit, Which, if the vessel sinks, releases at a certain depth the EPIRB automatically from its stowage position.
When the EPIRB emerges on the surface it will automatically start the distress alert.