Distress radiobeacon

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Distress radio beacons, also known as emergency beacons, ELT or EPIRB, are tracking transmitters which aid in the detection and location of boats, aircraft, and people in distress. Strictly, they are radiobeacons that interface with worldwide offered service of Cospas-Sarsat, the international satellite system for search and rescue (SAR). When manually activated, or automatically activated upon immersion, such beacons send out a distress signal. The signals are monitored worldwide and the location of the distress is detected by non-geostationary satellites, and can be located by trilateration in combination with triangulation, respecting the varying quality of the signal received.[1]

In the case of 406 MHz beacons which transmit digital signals, the beacons can be uniquely identified almost instantly (via GEOSAR), and furthermore a GPS or GLONASS position can be encoded into the signal, which provides instantaneous identification of the registered user and its location. Frequently, by using the initial position provided via the satellite system, SAR aircraft and ground search parties can home in on the distress signals from the beacons and come to the aid of the concerned boat, aircraft, or people.

There are three types of distress radio beacons compatible with the Cospas-Sarsat system:[2]

  • EPIRBs (emergency position-indicating radio beacons) signal maritime distress.
  • ELTs (emergency locator transmitters) signal aircraft distress.
  • PLBs (personal locator beacons) 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.[3]

The basic purpose of distress radiobeacons is to get people rescued within the so-called "golden day"[4] (the first 24 hours following a traumatic event) during which the majority of survivors can usually be saved.

Since the inception of Cospas-Sarsat in 1982, distress radiobeacons have assisted in the rescue of over 22,000 people in more than 6,000 distress situations.[5] In 2006, distress radiobeacons aided in the rescue of 1,881 people in 452 distress situations.[5] There are roughly 556,000 121.5 MHz beacons and 429,000 406 MHz beacons.[6]


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