The use of special-purpose radiobeacons, either manually or automatically activated by an aircraft crash or maritime distress situation, reduces the time required to alert the appropriate authorities and for final location of the distress site by the rescue team
The 1988 amendment to the Convention for the Safety of Life at Sea, 1974 (SOLAS Convention) establishing the Global Maritime Distress and Safety System (GMDSS) mandates that ships of 300 tons and over carry a Satellite Emergency Position Indicating Radio Beacon (Satellite EPIRB). This carriage requirement became effective on 1 August 1993. Cospas-Sarsat compatible 406 MHz EPIRBs satisfy the alerting requirement of the GMDSS.
The International Civil Aviation Organization (ICAO) recommends that, from July 2008, all aircraft under the jurisdiction of the ICAO Convention carry an Emergency Locator Transmitter (ELT) operating on the frequency 406 MHz for compatibility with the Cospas-Sarsat System, and on 121.5 MHz for "homing" purposes.
Various national requirements also exist for the carriage of ELTs/EPIRBs on various types of craft not otherwise subject to international conventions, and some countries have authorised the use of 406 MHz Personal Locator Beacons (PLBs) on land, in remote or rugged areas.
A large number of 121.5 MHz beacons are installed on board light aircraft and carried on board pleasure craft, either as a result of voluntary fitting or in response to specific national carriage requirements. These users should consider replacing their 121.5 MHz beacons with 406 MHz beacons as the satellite processing of 121.5 MHz emission was terminated on 1 February 2009.