Distress beacon

An Emergency Position-Indicating Radiobeacon Station or Emergency Position Indicator Radio Beacon (short: EPIRS or EPIRB) is a station in the mobile service used in search and rescue operations. In marine use the terminology Emergency Position Indicating Radio Beacon (EPIRB) is used.

EPIRBs are tracking transmitters which aid in the detection and location of boats, aircraft, and people in distress. A PLB (personal locator beacon) is particular type of EPIRB that is typically smaller, has a shorter battery life and unlike a proper EPIRB is registered to a person rather than a vessel. The terms ELB (emergency locator beacon) and ELT (emergency locator transmitter) are used interchangeably with EPIRB only when used on aircraft. Strictly, they are radiobeacons many of which interface with worldwide offered service of Cospas-Sarsat, the international satellite system for search and rescue (SAR). Transmitters broadcasting on 406 MHz are recognized. When manually activated, or automatically activated upon immersion or impact, such beacons send out a distress signal. The signals are monitored worldwide and the location of the distress is detected by non-geostationary satellites using the doppler effect for trilateration, and in more recent EPIRBs also by GPS.

The basic purpose of a distress radiobeacon is to help rescuers find survivors within the so-called "golden day" (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 28,000 people in more than 7,000 distress situations. In 2010 alone, the system provided information which was used to rescue 2,388 persons in 641 distress situations.

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