What is an EPIRB?
EPIRB stands for Emergency Position Indicating Radio Beacon. This is a battery powered radio 
transmitter designed to release and float free from a sinking ship and to send an automatic distress signal. Over 250,000 EPIRBs have been installed world-wide, operating in the 406MHz frequency band. These EPIRBs relay their messages to ground stations via the COSPAS-SARSAT satellite network. The distress messages are then passed on the nearest Maritime Rescue Coordination Centre (MRCC) to come to the aid of the survivors. Most EPIRBs also include a flashing strobe light and a second low-power radio transmitter to assist in final location of the survivors by the Search And Rescue (SAR) forces. The COSPAS-SARSAT system also processes signals from aircraft beacons, known as ELTs (Emergency Locator Transmitters) and from Personal Locator Beacons (PLBs).
All 406MHz beacons must be type approved by COSPAS-SARSAT in order to ensure compatibility with the satellite system. This sets a minimum standard which means that the signal from any of these beacons should be processed by the system and produce the necessary alert.
There have been incidents where vessels have sunk quickly and crew have not had time to deploy an EPIRB. In these cases " float free " EPIRB's may have reduced rescue times and saved lives.
Yachting Australia requires all crew in Cat1 and Cat2 ocean races to carry a PLB whilst on deck. An EPIRB also must be carried in the yacht. PLB's are not considered a substitute for EPIRB's when complying with marine regulations for the carriage of EPIRB's.
406 Mhz Epirbs and PLB's come in 2 basic types. Those that include a GPS position as part of the distress signal and those that do not. The satellite system can calculate a beacon location but locating a distress site is usually much faster with the GPS signal transmitted..... GPS Vs Non-GPS Beacon
For more detail on EPIRBs for leisure marine, click here.
For more detail on EPIRBs for commercial shipping, click here.