Emergency Position Indicating Radio Beacon

Definition
An Emergency Position-Indicating Radio Beacon (EPIRB) is

"a device that can be automatically or manually activated to transmit a distress signal to a satellite. EPIRBs that activate automatically typically have a hydro-static release mechanism that allows the beacon to release from its bracket, float to the surface and start transmitting. The beacon, along with the bracket, has to sink to approximately 3 meters before it will activate automatically."