An Emergency Position Indicating Radio Beacon or EPIRB is used in the event of an emergency to alert search and rescue teams to your location. It transmits a coded message via satellite and earth stations on the distress frequency to the nearest rescue centre.
A Personal Location Beacon (PLB) works in the same way as an EPIRB, by transmitting a coded message on the distress frequency that is relayed by the Cospas-Sarsat global satellite system
An EPIRBs differs to a PLB as it is registered to the boat or vessel, whereas a PLB is registered to an individual. As a result an EPIRB tends to be much larger than a PLB and will generally have a longer battery life.