Module 9 - GMDSS & Safety Equipment
EPIRB, PLB, and SART
What you will learn
Distinguish satellite distress alerting, personal alerting and on-scene locating without treating any device as a complete rescue plan.
EPIRBs and PLBs alert through the 406 MHz satellite system; SARTs help rescue units find survival craft at the scene. Their jobs overlap only at the edges.
An EPIRB is associated with a vessel. It sends a 406 MHz distress alert through the Cospas-Sarsat system towards a rescue coordination centre and provides an on-scene 121.5 MHz homing signal. It is designed to float upright and is commonly carried in a float-free bracket so it can release if the vessel sinks, subject to its approved installation and operating instructions.
A PLB is a personal 406 MHz beacon. It is manually activated, is not normally fitted to a vessel, may not float in the operating attitude and should normally be held out of the water with its antenna correctly deployed. It supports a person, but carriage, registration and operating details still matter.
A radar SART replies to 9.2–9.5 GHz search radar and creates a distinctive response on the rescuer's display. An AIS-SART transmits a locating signal for compatible AIS equipment. These are on-scene locating aids, not substitutes for the initial satellite or radio distress alert.
Worked example
A crew abandons into a liferaft after sending a VHF DSC distress alert; the vessel EPIRB has released and a radar SART is carried aboard the raft.
- 1Confirm the EPIRB is transmitting correctly and keep its antenna clear according to its instructions.
- 2Deploy the radar SART as high as practicable in the survival craft when searching units may be approaching.
- 3Maintain voice and visual watch; neither beacon carries the full incident conversation.
Sense check: The EPIRB can alert distant coordination services; the SART becomes most useful when compatible search equipment is near enough to detect it.
| Device | Primary job | Operating boundary |
|---|---|---|
| EPIRB | Vessel-associated 406 MHz satellite alert plus homing | Correct registration, bracket, deployment and maintenance |
| PLB | Personal 406 MHz satellite alert | Manual operation; normally held clear of water |
| Radar SART / AIS-SART | Help rescue units locate survivors on scene | Requires compatible receiving/search equipment |
Ask what function is still missing
A skipper says a PLB makes a vessel EPIRB, VHF and SART unnecessary.
1. Separate the functions
List alerting, two-way communication and on-scene locating rather than counting gadgets.
2. Check the wearer
Confirm the PLB can be reached, deployed and held correctly if the person is injured or immersed.
3. Check the vessel plan
Review the route, crew, legal carriage requirements and independent systems.
Sense check: If one manually operated personal item is the only route to assistance, several foreseeable failures still have no answer.
Common mistake or limitation
- Calling a PLB a smaller vessel EPIRB and assuming it will float upright.
- Expecting 121.5 MHz to carry the satellite alert instead of the local homing signal.
- Describing a SART vaguely as a long-range distress beacon.
Recap
- EPIRBs and PLBs use 406 MHz for satellite alerting; 121.5 MHz supports homing.
- A PLB is personal and manually activated; follow its out-of-water deployment instructions.
- Radar SART and AIS-SART are principally on-scene locating aids.
Optional quick check
Section 2 of 10
What is the primary GMDSS role of a radar SART?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
Continue studying GMDSS & Safety Equipment
This public lesson is part of Revision Module 9. Full revision access adds the guided Learn, Practise and Test flow, flashcards and revision progress.