An emergency locator beacon is a radio beacon, a battery poweredradio transmitter, used to locate airplanes, vessels, and persons in distress and in need of immediate rescue. Various types of emergency locator beacons are carried by aircraft, ships, vehicles, hikers and cross-country skiers. In case of an emergency, such as the aircraft crashing, the ship sinking, or a hiker becoming lost, the transmitter is deployed and begins to transmit a continuous radio signal, which is used by search and rescue teams to quickly find the emergency and render aid.
Defined officially as emergency position-indicating radiobeacon stations in the ITU Radio Regulations, these transmit a coded data burst once every 50 seconds, conforming to the specification, C/S T.001 Specification for COSPAS-SARSAT 406 MHz Distress Beacons, and are designed to be detected and located by an international set of search-and-rescue transponders on various satellites. The different types include:
ELTs signal aircraft distress
EPIRBs signal maritime distress
SEPIRBs are EPIRBs designed only for use on submarines
SSASes are used to indicate possible piracy or terrorism attacks on sea-going vessels
PLBs are for personal use and are intended to indicate a person in distress who is away from normal emergency services; e.g., 9-1-1. They are also used for crewsaving applications in shipping and lifeboats at terrestrial systems. In New South Wales, some police stations and the National Parks and Wildlife Service provide personal locator beacons to hikers for no charge.
* A specialized radar beacon that emits a string of 12 dots for display on an X-band radar screen when scanned.
Man-overboard beacons
MSLDs are man-overboard signalling devices, first standardized in 2016.
* A Maritime Survivor Locator Device is a man-overboard locator beacon. In the U.S., rules were established in 2016 in 47 C.F.R. Part 95. A MSLD may transmit on 121.500 MHz, or one of these: 156.525 MHz, 156.750 MHz, 156.800 MHz, 156.850 MHz, 161.975 MHz, 162.025 MHz.
* A hand-held automatic identification system transmitter that emits only an emergency beacon. It does not have a receiver and thus cannot be a transponder.
