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Beacons and MOB

Beacons and man-overboard gear.

Satellite beacons alert search and rescue on shore. AIS man-overboard beacons alert the boats nearby. They do different jobs, and the official sources treat them differently.

Get trained

This page explains the principles. It is not a substitute for hands-on instruction from a recognized program such as US Sailing, the RYA or ASA, and it does not replace the safety rules that apply where you sail.

Three kinds of beacon

The Coast Guard describes three kinds of 406 MHz distress beacon, all of which alert rescuers through the SARSAT satellite system: the PLB (personal locator beacon), carried by a person; the EPIRB (emergency position-indicating radio beacon), mounted on a vessel and larger and more powerful; and the ELT, installed in aircraft. A separate category, the AIS MOB beacon, works differently.

PLBEPIRBAIS MOB beacon
Who it alertsSearch and rescue via satelliteSearch and rescue via satelliteNearby boats and plotters with AIS
Carried byA personA vesselA person
Part of the satellite systemYesYesNo (Seas of Solutions)
Switched onBy hand (Coast Guard, 2015)Category I automatically on release; Category II by handSome switch on when the lifejacket inflates (Ocean Signal's claim)
Transmit timeAt least 24 hours (Coast Guard, 2015)At least 48 hours (Ocean Signal's claim for its units)Not covered by our sources; range claims are below

PLBs

A 2015 Coast Guard SARSAT presentation says a PLB is switched on by hand, may or may not float, and must be held out of the water to transmit. The beacon maker Seas of Solutions notes that a PLB alert goes to a Rescue Coordination Centre, so nearby boats hear nothing until the shore authorities contact them, and that its PLBs also carry a 121.5 MHz homing signal.

EPIRBs

The same 2015 presentation says a Category I EPIRB sits in a bracket with a hydrostatic release that frees the beacon and switches it on at 1.5 to 4.0 m depth, while a Category II must be taken out of its bracket and switched on by hand. It says the hydrostatic release must be replaced every two years from installation or four years from manufacture. The Coast Guard's 2024 DSC article recommends carrying an EPIRB alongside a DSC radio, since receiving both alerts helps confirm a real emergency (see electronics).

AIS MOB beacons

Seas of Solutions stresses that an AIS MOB device is not part of the COSPAS-SARSAT network and should not be called a PLB. Ocean Signal explains that it alerts nearby AIS-equipped boats and chartplotters rather than satellites. Range figures come only from manufacturers and do not agree: Ocean Signal claims a typical 1 to 2 miles for its unit, and Seas of Solutions claims about 4 miles for its FastFind CREW1.

US Sailing's Safety at Sea Committee calls personal AIS the best way for a nearby boat to find someone in the water. It reports that night tests relocated casualties well beyond visual range, and recommends AIS for night sailing, very fast boats, wavy conditions and all shorthanded boats.

Registering a 406 MHz beacon

The Coast Guard says every 406 MHz beacon must be registered, and anyone who buys a new or used US-coded beacon must register it with NOAA. NOAA says this is required by law. As the official sources state it:

  • Registration is free and required by federal regulation (47 CFR). Not registering, or not reporting a change of owner, can lead to penalties or fines (Coast Guard brochure).
  • Registrations expire after two years and must be renewed. You update them online using the beacon's 15-digit Unique ID, and paper forms can be mailed or faxed (NOAA, Coast Guard).
  • When a beacon is sold, the seller must notify NOAA and the buyer must re-register it. Otherwise rescuers may call the seller when it goes off (Coast Guard).

Registration matters because, according to the Coast Guard, its data helps confirm accidental activations and avoid unnecessary rescue missions. Its 2024 DSC article says 98% of EPIRB, ELT and PLB activations are false alerts. Check NOAA's current registration rules before you buy or sell a beacon.

Recovery gear

The cited sources describe these pieces of equipment, and how to use them is something to practise with an instructor.

  • Lifesling. Practical Sailor describes it as a flotation collar in a bag, attached to a long floating line, usually hung on the transom. It was introduced by the Sailing Foundation in Seattle. US Sailing's Safety at Sea Committee says it is common in the US and cited in US Sailing Safety Equipment Requirement 3.7.1, and recommends adding a small drogue, lights facing both up and down, and SOLAS reflective tape on the line.
  • Marker pole. The committee recommends a MOM8-type marker, which combines a six-foot pole with a light and a horseshoe buoy.
  • Throw line and throwable. US Sailing's 2025.2 nearshore requirements, in force for 2026, call for a floating polypropylene throw line of at least 15 m (50 ft) and an approved throwable device. They also require two-thirds of the racing crew to practise man-overboard recovery each year.

The same committee calls wearing a harness and tether on deck the real solution to crew overboard; see life jackets, harnesses and tethers.

Offshore racing rules

World Sailing's Offshore Special Regulations cover EPIRBs and personal beacons for offshore races. According to an April 2026 Irish Sailing notice, the EPIRB and communications sections were among those amended for 2026-2027, and we could not find the new wording. Check the current OSR and your Notice of Race rather than relying on older summaries.

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