An Emergency Position Indicating Radio Beacon or EPIRB is used to alert search and rescue services in the event of an emergency. It does this by transmitting a coded message on the 406 MHz distress frequency via satellite and earth stations to the nearest rescue co-ordination centre.
Some EPIRBs also have built-in GPS which enables the rescue services to accurately locate you to +/- 50 metres.
EPIRBs are installed on boats and can either be operated automatically after an incident or manually.
A Search and Rescue Transponder (SART) is an electronic device that automatically reacts to the emission of a radar. This enhances the visibility on a radar screen. SART transponders are used to ease the search of a ship in distress or a life craft.
If the SART detects a signal it immediately transmits twelve pulses on the same frequency.