At a glance
| Beacon | Who it alerts | Registered to | Best for |
|---|---|---|---|
| EPIRB | Search and rescue, via the Cospas-Sarsat satellites on 406 MHz | To the vessel | The boat in serious trouble, or abandoning to the liferaft |
| PLB | Search and rescue, via the Cospas-Sarsat satellites on 406 MHz | To a person | A person in the water or separated from the boat, worn on the lifejacket |
| AIS MOB beacon | AIS screens on nearby vessels, including your own; some also trigger a DSC alert | Coded to the beacon, not a satellite registration | Getting your own boat back to someone who has gone overboard |
EPIRBs
An emergency position-indicating radio beacon sends a distress alert on 406 MHz to the Cospas-Sarsat search and rescue satellites, which pass it to a rescue coordination centre, with the boat's identity and, for models with GPS, its position. EPIRBs float, are built to transmit for a long time, and can be mounted in a bracket that releases them automatically if the boat sinks. Signals from an EPIRB are one of the recognised distress signals in COLREGS Annex IV.
PLBs
A personal locator beacon works through the same satellite system but is small enough to carry on a lifejacket. It is registered to a person rather than a boat, and usually has to be held up out of the water to work well. For offshore sailing, many crews carry PLBs as well as the boat's EPIRB.
AIS man overboard beacons
An AIS MOB beacon, usually fitted inside a lifejacket and activated when it inflates, transmits the casualty's position as an AIS target. It shows up on AIS-equipped plotters and radios nearby, including your own, so you can steer back to the person. Some also send a DSC alert to nearby radios. It doesn't use the satellite system, so it won't raise the alarm with search and rescue far away.
Using them
- Send a DSC alert and a Mayday by radio first if you can. Beacons back up the radio, they don't replace it.
- If you abandon to the liferaft, take the EPIRB and switch it on.
- Once activated in a real emergency, leave it on: switching it off and on confuses the search.
- If you set one off by mistake, switch it off and tell the Coastguard straight away.
- Test beacons only as the manufacturer instructs, and check battery expiry dates.
For the rest of the distress picture, see distress signals, sending a Mayday and man overboard.