EPIRB or PLB? The Question That Matters Most
EPIRBs (Emergency Position Indicating Radio Beacons) are registered to a vessel and are typically mounted to the boat, often in a bracket designed to release automatically if the vessel sinks. PLBs (Personal Locator Beacons) are registered to a person, are smaller and lighter, and are designed to be carried on your body, in a pocket, on a pack strap, or clipped to a lifejacket.
That registration difference drives the real-world decision. If you mostly fish or cruise from one boat and want a beacon that floats free and starts transmitting the moment your vessel goes down, an EPIRB is the right call. If you move between boats, also hunt, tramp or kayak, or want a beacon that stays with you specifically if you go overboard separated from the vessel, a PLB makes more sense, and it'll cover you on land too.
EPIRBs run longer once activated, a minimum of 48 hours, against a PLB's minimum 24 hours, which matters if you're operating somewhere genuinely remote where rescue could take time. Plenty of serious offshore operators carry both: a Category I EPIRB mounted to the boat as the primary line, and a PLB on each crew member as personal backup.
If you're weighing a PLB against a satellite messenger rather than an EPIRB, we've covered that specific comparison in our emergency satellite messenger guide.
Category I vs Category II EPIRBs Explained
Once you've settled on an EPIRB, the next decision is activation type.
| Category | Activation | Best Suited To |
|---|---|---|
| Category I | Automatic, float-free release | Vessels at real risk of sudden capsize or sinking |
| Category II | Manual (some also water-activated) | Vessels where you'll have time to grab the beacon |
Category I EPIRBs sit in a special bracket fitted with a hydrostatic release. If the vessel sinks past a set depth, the mechanism releases the EPIRB, which floats to the surface and begins transmitting automatically, no action required from anyone on board. That makes positioning important: it needs to be mounted outside the cabin where it can genuinely float free, not somewhere it'll be trapped inside a sinking hull.
Category II EPIRBs require someone to physically activate them, though many modern units also include water activation as a backup. They're a sound choice where you'll realistically have time to grab the beacon before abandoning ship, and they're generally the more affordable option.
What Actually Changes Between Models
Every modern EPIRB and PLB transmits the same core signal: 406MHz to the Cospas-Sarsat satellite network, carrying a unique identification code, plus a lower-power 121.5MHz homing signal that search teams use to close the final distance once they're in the general area. Beyond that baseline, a handful of things genuinely separate one model from another.
- GPS or GNSS accuracy: built-in GPS narrows your position to around 100 metres, a major improvement over satellite-only detection, which can take longer and locate you to within a couple of kilometres.
- AIS: some EPIRBs broadcast an AIS alert on VHF as well as the satellite signal, meaning any nearby vessel with AIS can see your position directly, not just the rescue coordination centre.
- Return Link Service (RLS): newer beacons can show a visual confirmation, usually a flashing light, that your distress signal has actually been received, which matters a great deal psychologically in a genuine emergency.
- Battery life: check both the standby storage life (typically five to eight years before replacement) and the operating life once activated.
- Strobe light: EPIRBs are required to include one; PLBs aren't always, but it's worth having for visibility during a night rescue.
None of these features change the fundamental job the beacon does. They change how quickly and confidently rescuers can find you once it's done its job.
Real EPIRB and PLB Options from Mobile Systems
Here's current, in-stock hardware spanning both categories and price points.
If you want a two-way device that lets you send check-in messages as well as an SOS, rather than a one-way distress-only beacon, that's a satellite messenger, a different category covered in our satellite devices range.
Registration: The Step People Skip
An unregistered beacon still works. It just works a lot worse for you. When an EPIRB or PLB activates, the satellite system identifies the beacon by its unique code. If that code is registered, Rescue Coordination Centre New Zealand (RCCNZ) can immediately pull up who you are, your emergency contacts, and details about your vessel or trip, letting them launch a targeted response. If it's not registered, that confirmation and context simply isn't there, which can genuinely slow things down.
Registration with RCCNZ is free and takes a few minutes, whether you do it online, by email, or by post. It's also a legal requirement for 406MHz beacons in New Zealand. Update your details whenever your contact information, vessel, or planned activity changes, an outdated registration is only marginally better than none at all.
