Safety kit
What Is a PLB? Personal Locator Beacons for Sailors
Published · Last checked October 2026
A PLB (Personal Locator Beacon) is a small 406 MHz distress beacon registered to a person rather than a boat. When you deploy the antenna and switch it on, it sends your identity and GPS position via the Cospas-Sarsat satellites to rescue services, plus a 121.5 MHz homing signal. It is small enough to wear on a lifejacket. A PLB alerts shore-based rescue; a personal AIS beacon instead alerts your own boat and nearby vessels. Many sailors carry one of each type.
How a PLB works
A PLB uses the same satellite system as an EPIRB. The difference is size and registration: it belongs to you, so it goes with you whether you are on your own boat, crewing for someone else or walking in the hills (check the rules for land use in your country). Most PLBs must be switched on by hand, and many need the antenna unfolded. Battery life once activated is designed to be at least 24 hours.
PLB, personal AIS or EPIRB?
| Device | Who it alerts | Range | Registered to |
|---|---|---|---|
| PLB (406 MHz) | Rescue coordination centre via satellite | Global | Person |
| Personal AIS beacon (MOB) | AIS receivers nearby, including your boat | Line of sight, typically a few miles | Person (no registration, MMSI starts 972) |
| DSC MOB beacon | Your boat's DSC VHF, then all stations if not cancelled | Line of sight | Programmed to your boat's MMSI |
| EPIRB | Rescue centre via satellite | Global | Vessel |
For a person overboard, the fastest rescue is usually your own boat turning back. A personal AIS beacon shows the casualty on the plotter immediately. A PLB brings in the coastguard, which matters if the boat cannot recover you, for example if you go over when single-handed.
Choosing and fitting one
- Look for a unit small enough to fit in a lifejacket pocket or attach to the waist belt.
- Make sure the antenna can deploy and point upwards while you are in the water.
- Built-in GPS speeds up the position fix significantly.
- Some lifejackets are designed to take a specific PLB or AIS beacon in the bladder cover; check compatibility.
Registration
In the UK, register your PLB free with the UK Beacon Registry and keep your emergency contacts up to date. Do not use the live alert to test: use the self-test only. If you activate it by mistake, call the coastguard. See the personal safety lesson and man overboard lesson for how beacons fit into recovery.