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The Emergency Position Indicating Radio Beacon is designed to assist rescuers in finding you during an emergency. alengo / Getty ImagesEPIRB, which stands for Emergency Position Indicating Radio Beacon, is a device that helps rescuers pinpoint your location in urgent situations. These radios, first introduced in the 1970s, have saved countless lives, with boaters being the primary users.
A modern EPIRB is a highly advanced gadget equipped with the following features:
- A 5-watt radio transmitter operating on a 406 MHz frequency (see How the Radio Spectrum Works for more on frequency details)
- A 0.25-watt radio transmitter working on 121.5 MHz
- A GPS receiver
Upon activation, both radios begin transmitting. A GOES weather satellite in geosynchronous orbit, approximately 24,000 miles (39,000 km) above the Earth, picks up the 406-MHz signal. Embedded in this signal is a unique serial number, and if the unit includes a GPS receiver, the signal also relays the precise location of the radio. If the EPIRB is registered, the serial number enables the Coast Guard to identify its owner. Rescuers aboard planes or boats can use either the 406-MHz or 121.5-MHz signal to locate the EPIRB.
Earlier versions of EPIRBs lacked GPS receivers, so the GOES satellite only received the serial number. To find the EPIRB's location, other satellites, such as the TIROS-N satellite, orbiting the Earth in low polar orbits, could detect the signal when passing overhead. This would provide a rough location, but it took hours for a satellite to be in range.
Here are some resources to help you understand more:
- U.S. Coast Guard: EPIRB
- TIROS-N satellite
- GOES Science
- How Radio Works
- How the Radio Spectrum Works
- How GPS Receivers Work
