EPIRB

An EPIRB, or emergency position-indicating radio beacon, is a portable or fixed device used to alert search and rescue authorities in maritime, aviation, or land emergencies. When activated, it broadcasts a distress signal that can be detected by satellites and ground stations operating under the COSPAS-SARSAT program, enabling rapid response and location data for rescuers.

Most modern EPIRBs operate at 406 MHz and may include a GPS receiver to transmit precise coordinates. A 406 MHz signal carries a unique beacon identifier and, if GPS is fitted, a location fix. Older or regional models may also emit 121.5 MHz or 243 MHz signals for homing by SAR teams, but satellites primarily rely on 406 MHz.

Activation and installation: EPIRBs can be manually activated by crew or automatically activated when water immersion occurs, if equipped with a hydrostatic release unit (HRU) or a crash sensor. They come in portable handheld units for vessels or aircraft and fixed-mount units aboard ships, offshore platforms, or aircraft. Fixed units on life rafts may be linked to the raft's hydrostatic release mechanism.

Networking and response: On activation, the beacon sends data to the COSPAS-SARSAT satellites, which relay it to national Mission Control Centers and Rescue Coordination Centers. Information registered to the beacon, such as vessel name, call sign, and contact details, is used to coordinate rescue operations.

Regulation and maintenance: EPIRBs are typically registered with national authorities. They require battery replacement every several years, and periodic testing using approved self-tests. In SOLAS-regulated ships and many commercial aircraft, EPIRBs must meet performance standards and be readily accessible and properly maintained. False alarms are subject to penalties in many jurisdictions.

See also: Personal locator beacon (PLB) is a similar device intended for individuals on land or in remote areas; EPIRBs are intended for vessels or aircraft.