What is an EPIRB and PLB: How Do They Work?

Emergency position indicating radio beacons, commonly called EPIRBs, and their smaller siblings personal locator beacons (PLBs), are life-saving devices that can greatly increase the level of boating safety you enjoy while out on the water.

These devices send out an SOS via satellite communications at the flip of a switch, and inform search-and-rescue personnel of your position from virtually anywhere on Earth. Every year hundreds of lives are saved thanks to the use of EPIRBs and PLBs.

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What is the Difference Between an EPIRB and a PLB?

The biggest difference between these two devices is that EPIRBs are registered to a boat while PLBs are designed for use by an individual. EPIRBs are mounted on the boat itself, while PLBs are usually worn on a PFD or carried in a pocket or “ditch bag” (a bag of emergency gear you can grab in a hurry).

Category I EPIRBs are designed to automatically release from their mounted position and activate when they become submerged, while Category II EPIRBs may be hard-mounted or carried in a bag and are released and activated manually. EPIRBs are larger than PLBs, usually have more battery life (they’re required to have a minimum of 48 hours of activation time versus 24 hours for PLBs), and they always have a strobe light built in, while PLBs may or may not have a strobe light.

How Does an EPIRB Work?

When a locator beacon is activated it transmits an SOS message on the 406 MHz frequency (which is reserved for emergency distress communications) to the Cospas-Sarsat international search and rescue satellite constellation, and other geostationary satellites.
The distress signal is then relayed to a network of ground stations and the U. S. Mission Control Center (USMCC) in Suitland, MD.
Once alerted, the USMCC alerts the appropriate local or national authorities to initiate a search and rescue mission.
Commonly, the very first thing the authorities will do is attempt to contact the beacon owner and/or his or her emergency contacts to make sure that it hasn’t been triggered accidentally, but assuming it hasn’t, rescuers can initiate a response within minutes.

Photo Courtesy: BoatUS Foundation

In the past, the search and rescue personnel would have had a general location and homing in on the exact location of the beacon could take hours, as opposed to minutes. Today, however, modern EPIRB and PLB models generally have internal GPS (sometimes people call them “GPIRBs”). This allows them to transmit their exact location when activated, radically reducing the search-time. In fact, many mariners are fond of saying that a modern GPS-equipped EPIRB or PLB takes the “search” out of “search and rescue.”

By law, all locator beacons are registered with the National Oceanic and Atmospheric Administration (NOAA). Once registered the beacon’s unique 15-digit identification code is then associated with either your boat or you personally, so if it ever gets triggered and begins transmitting its signal the authorities immediately know who you are, the size and type of boat the unit may be associated with, and additional information such as your port of call and emergency contacts.

Where Can I Get an EPIRB?

Although these devices must be registered to a boat or a person, boaters who may be taking a long or unusual cruise who want to boost their safety margin can rent an EPIRB of PLB. The BoatUS Foundation has an EPIRB rental program just for this purpose. The beacons you rent are registered to the Foundation, and when renting one you’ll provide your vessel type, itinerary, and other pertinent information. If a unit gets triggered, the BoatUS Foundation immediately passes this information on to the US Coast Guard.

These rentals are extremely reasonable ($10 a day or $65 a week for an EPIRB or $7 a day or $45 a week for a PLB). However, the truth is that EPIRBs and PLBs are very affordable in the first place.

An average GPS-enabled Category II EPIRB unit costs in the $500 to $700 range, while an average PLB with GPS functionality costs around $300 to $400.

Considering how much these units enhance your safety at sea, most boaters would surely agree that getting a modern EPIRB or PLB is well worth the investment.