EPIRB vs PLB: Choosing the Right Beacon for Offshore Sailing

Posted on June 16, 2025

By James Hewitt, Managing Director, Ocean Signal

When you’re hundreds of miles from land, your GPS plotter might show nothing but blue. It’s in that moment—far beyond VHF range and reliant on satellite connectivity for weather, routing, and contact—that the real importance of emergency preparedness becomes clear. As someone who’s spent countless nights offshore—from Biscay gales to Pacific doldrums—I’m often asked: Should I carry an EPIRB, a PLB, or both?

The short answer? If you’re serious about offshore safety, you need both. But understanding the differences between EPIRBs and PLBs—and their roles on board—is key to building a reliable emergency plan.

What’s the Difference? A Technical Overview – EPIRB vs PLB

EPIRBs (Emergency Position Indicating Radio Beacons) and PLBs (Personal Locator Beacons) both transmit a 406 MHz distress signal to the Cospas-Sarsat satellite network, used by global search and rescue organizations (when activated). They also both transmit a 121.5 MHz homing signal for SAR aircraft or vessels.

But beyond that, there are fundamental differences between EPIRBs and PLBs in function, form, and use case:

Feature	Ocean Signal EPIRBs (e.g., EPIRB3)	Ocean Signal PLBs (e.g., PLB3)
Registration	Tied to a vessel (MMSI/IMO)	Registered to an individual
Activation	Automatic (float-free) or manual	Manual only
Battery Life (transmit)	~48 hours	~24 hours
Deployment Location	Mounted on vessel, auto-release options	Worn on lifejacket or kept in grab bag
Return Link Service (RLS)	Yes, on EPIRB3 (Galileo RLS)	Yes, on PLB3
AIS Transmission	Yes (EPIRB3 includes AIS and strobe)	Yes (PLB3 includes AIS and strobe)
GNSS Support	Multi-constellation (GPS, Galileo, etc.)	Multi-constellation
Primary Use	Vessel-level emergency beacon	Personal overboard or abandon ship backup

Understanding the Tech: Acronyms & What They Mean

If you’re investing in offshore safety gear, it’s worth understanding what all those acronyms in the spec sheets actually mean. Here’s a plain-language breakdown of the most important terms you’ll see when comparing an EPIRB vs PLB:

📡 406 MHz

The international distress frequency used by EPIRBs and PLBs.
Transmits your emergency signal to the Cospas-Sarsat satellite system.
Global coverage and monitored 24/7 by rescue coordination centers.

📡 121.5 MHz

A homing signal transmitted after activation to help local rescuers (SAR aircraft or vessels) zero in on your location.
Not satellite-monitored anymore, but crucial in final approach for rescue.

🛰️ GNSS (Global Navigation Satellite System)

The umbrella term for satellite navigation systems like GPS (USA), Galileo (EU), GLONASS (Russia), and BeiDou (China).
Ocean Signal beacons use multi-constellation GNSS to get a faster and more accurate location fix – even in difficult satellite conditions.

🛰️ GPS (Global Positioning System)

The American GNSS system.
Still the most widely used satellite positioning service, especially in marine electronics.

🛰️ Galileo

Europe’s global navigation satellite system.
Offers high precision and supports advanced features like Return Link Service (RLS)

🔁 RLS (Return Link Service)

A game-changing feature via the Galileo network.
Sends a confirmation message back to your beacon once your distress signal has been received and processed by rescue authorities.
Provides psychological reassurance in an emergency (“Help is on the way”).

📡 AIS (Automatic Identification System)

A local maritime VHF system used to track vessels in real time.
Ocean Signal’s PLB3 and EPIRB3 both transmit AIS signals when activated, allowing nearby ships to see your position on their chart plotters—even before global SAR assets arrive.

💡 Strobe

High-intensity LED flashing light integrated into the beacon.
Makes you visually easier to locate in darkness or poor visibility.

🚨 MMSI (Maritime Mobile Service Identity)

A unique 9-digit number assigned to your vessel or handheld device.
Used in the registration of EPIRBs and PLBs for identification during distress scenarios.

🛰️ Cospas-Sarsat

The international satellite network used by all 406 MHz distress beacons.
Operated by a coalition of global governments for non-commercial, emergency-only use.
Zero subscription fees—this system exists to save lives, not sell data.

Why You Need an EPIRB for Offshore Voyaging

An EPIRB is the gold standard for offshore emergencies. The Ocean Signal EPIRB3 is a modern example of how far the tech has come: it’s compact, includes AIS for local tracking by nearby vessels, and features Return Link Service to confirm that your distress signal has been received.

Mounted on deck or near your grab bag, the EPIRB3 can float free and self-activate if your vessel sinks rapidly. That’s not something a PLB can do.

I see the EPIRB as your vessel’s primary global distress beacon. It broadcasts your GPS position, vessel information, and distress signal to global SAR authorities. Once activated, it can transmit for up to 48 hours—double the PLB’s endurance.

In short, the EPIRB is what gets the cavalry coming, even if you’re unconscious, adrift, or unable to manually activate anything.

Where PLBs Come In: Crew-Level Safety

Now imagine a different scenario—you’re tossed overboard on a night watch, separated from the vessel. In that moment, your ship’s EPIRB is irrelevant. What you need is a beacon that stays with you.

That’s where the Ocean Signal PLB3 shines.

It’s small enough to wear on a lifejacket, rugged enough for offshore conditions, and smart enough to include:

AIS, so nearby AIS-equipped vessels (like your own) can see your MOB position real time.
RLS, to let you know your signal has been received
Strobe light, for visual locating in darkness or rough seas.

It’s a vital tool for singlehanders and crewed boats alike. I’ve personally mandated that everyone aboard wears a PLB on night watch or in rough conditions. And in liferaft abandon-ship drills, it’s a secondary means of distress signalling that complements the EPIRB.

EPIRB vs PLB: Redundancy is Not a Luxury Offshore

In offshore sailing, redundancy equals survivability.

Your EPIRB ensures that global rescue assets are alerted to a vessel-level emergency—especially if you’re incapacitated or unconscious.
Your PLB ensures that you personally are findable—even if separated from the boat or liferaft.

And don’t forget that both devices now offer RLS, a game-changing feature providing reassurance that your call for help has reached someone. When you’re bobbing in 4-meter seas with 20 knots on the nose, that blinking RLS confirmation is more than a morale booster—it’s a lifeline.

Final Thoughts – EPIRB vs PLB: It’s Not Either/Or

Too many sailors still treat PLBs and EPIRBs as interchangeable. They’re not.

An EPIRB is essential. It’s among the first things I reach for in a vessel emergency. A PLB is a personal safety device that covers scenarios the EPIRB can’t. Together, they create a layered safety net.

Ocean Signal’s lineup—especially the EPIRB3 and PLB3—sets a new benchmark for integrated offshore safety with AIS, GNSS, and RLS in both formats.

If you’re heading offshore, don’t compromise. Carry both. Register both. And drill your crew on their use. Because when the sea shows its teeth, it’s too late to wish you’d brought the right gear.