⚠️ To remember before buying
An AIS MOB beacon is not an EPIRB/PLB: it alerts nearby vessels via AIS (within a few miles), not rescue services via satellite. For offshore sailing, you need 406 MHz Cospas-Sarsat (EPIRB or PLB). Confusing the two means false offshore security.
In brief
The essential in 30 seconds
- Three devices NOT to confuse: the PLB (personal beacon, 406 MHz satellite, registered to a person), the EPIRB (vessel beacon, 406 MHz satellite, registered to a boat), and the AIS MOB beacon (man overboard, local AIS only — no satellite).
- The category determines activation: Cat. 1 = automatic float-free release (hydrostatic release unit HRU, sometimes called "zafe"), Cat. 2 = manual activation.
- The key features in 2026: GNSS (fast position), AIS (local tracking by nearby vessels), RLS (Galileo acknowledgment), NFC (testing/configuration via the app).
- A beacon that is not coded or registered is a beacon that slows down — or loses — your rescue. This is the issue we handle most often in the workshop.
🛠️ Workshop note
Skysat distributes, codes and provides after-sales service for beacons (Ocean Signal, ACR…) in Carnac. This guide outlines what we would choose for our own boat, program by program.
1. EPIRB, PLB, AIS MOB: three devices, three uses
This is the most dangerous — and most common — confusion.
- EPIRB (Emergency Position-Indicating Radio Beacon) — the boat's beacon. Transmits on 406 MHz to Cospas-Sarsat satellites (global coverage) + 121.5 MHz for homing. Registered to the vessel. The reference distress alert for "the boat is sinking / we are abandoning ship".
- PLB (Personal Locator Beacon) — same principle 406 MHz satellite, but registered to a person, compact, manual activation, no automatic float-free. Carried on the person. Ideal as a complement, or for those who change boats often.
- AIS MOB beacon (man overboard) — note: it does NOT transmit to satellites. It triggers a local AIS alert received by nearby vessels (typically within a few miles) and displays the man overboard on their chartplotter/AIS. Perfect for recovering a crew member who has fallen overboard near the boat; it is not a satellite alerting device.
In short: AIS MOB = recover a crew member now, via nearby vessels. EPIRB/PLB = trigger global rescue via satellite. Both are complementary, not interchangeable.
2. Category 1 vs 2: automatic or manual float-free
For EPIRBs, the category describes the activation method:
- Category 1 (float-free) — mounted in a cradle with a hydrostatic release unit (HRU) that automatically releases the beacon at ~4 m depth if the boat sinks. The beacon floats and activates on its own. Essential if the scenario "the boat sinks quickly, crew incapacitated" is plausible (offshore, delivery, short-handed crew).
- Category 2 (manual) — fixed in an interior mount; a human must grab and activate it. Cheaper, ideal for coastal sailing where you keep control, but useless if no one can reach it.
With Ocean Signal, the EPIRB3 is Cat. 2 (manual) and the EPIRB3 Pro is Cat. 1 (float-free) — this is the main difference between the two, beyond price.
3. GNSS, AIS, RLS, NFC: the features that matter
Modern 406 MHz beacons are not all equal. What truly changes the speed and reliability of rescue:
GNSS
Precise position, fast
The beacon transmits its precise position within the first minutes, instead of leaving satellites to triangulate. Non-negotiable today.
AIS
Local tracking
In addition to 406 MHz satellite, the beacon appears on the AIS of nearby vessels: a cargo ship or neighboring mooring can locate you before even state resources arrive.
RLS
Acknowledgment
Via Galileo, an acknowledgment: an LED confirms your alert has been received and located. Psychologically huge when you're waiting alone in survival mode.
NFC
Test & monitoring
Test and configuration via smartphone app (check self-test, read history). Handy for monitoring.
Autonomy: a minimum of 24 h of transmission at -20 °C, with "Pro" models aiming for 48 h. The battery has a lifespan (often 7 to 10 years) that must be respected (see §5).
The EPIRB3 / PLB3 from Ocean Signal combine AIS + RLS + NFC; the EPIRB1 / PLB1 are the 406 + GNSS "essential" versions, without AIS.
4. Coding and registration: the costly trap
This is the issue we handle most often in the workshop — and the one that online "cheapest" purchases overlook.
A 406 MHz beacon is only operational once coded and then registered. In France, three steps:
- MMSI + vessel station license — ANFR. If the boat is equipped with VHF/ASN, the MMSI (9 digits) and the vessel station license are obtained from the ANFR, online at maritime.anfr.fr. The license — to be kept on board — lists the MMSI and the reference of each declared beacon.
- Beacon coding. Programming with the French country code + the identifier (the MMSI for a maritime EPIRB, or a serial number). A beacon purchased abroad is often coded for another country → the alert would go to the wrong coordination center. Skysat recodes for France (70 € excl. VAT flat rate).
- Registration — mandatory and free. Declaration of the beacon in the national 406 MHz beacon registry, operated by CNES (FMCC France): registre406.cnes.fr. Here you associate your emergency contacts: this is what allows rescue services to identify you — the vast majority of alerts are false alarms, which a call to the emergency contacts can resolve without mobilizing resources. This is a regulatory requirement under the Division 175 of the vessel safety regulations.
Resale / boat change: a beacon that changes hands must be re-registered; we regularly see beacons that still point to the former owner.
Buying the beacon is just the start. Coding + license + registration = what makes it truly operational — and that's precisely where an installer saves you time (and maybe more).
5. Maintenance: battery, hydrostatic release unit, overhaul
A beacon must be maintained — otherwise it won't activate when needed:
- Battery — typical lifespan 7 to 10 years; beyond that, mandatory replacement (flat rate EPIRB1 battery replacement: 233 € excl. VAT at our workshop). A regular self-test (TEST button / NFC app) does not replace the battery expiry date.
- Hydrostatic release unit (HRU) for Cat. 1 — a perishable part (usually every 2 years): past the date, automatic float-free is no longer guaranteed.
- Shore-based maintenance (SBM) — for beacons that require it, flat rate Shore-Based Maintenance from 230 € excl. VAT. We also handle the overhaul of certain beacons (e.g., Kannad).
In short: a beacon has an expiry date, like a life raft. Check the battery and hydrostatic release unit during the boat's annual refit — this is the habit that avoids a nasty surprise when it matters.
6. Comparison table
| Criteria | PLB1 | PLB3 | EPIRB1 Cat. 2 | EPIRB3 Cat. 2 | EPIRB3 Pro Cat. 1 |
|---|---|---|---|---|---|
| Type | personal | personal | vessel | vessel | vessel |
| 406 MHz satellite | ✓ | ✓ | ✓ | ✓ | ✓ |
| Integrated GNSS | ✓ | ✓ | ✓ | ✓ | ✓ |
| AIS | — | ✓ | — | ✓ | ✓ |
| RLS (Galileo) | — | ✓ | — | ✓ | ✓ |
| NFC (app) | — | ✓ | — | ✓ | ✓ |
| Activation | manual (on person) | manual (on person) | manual | manual | auto float-free |
| Transmission autonomy | ≥24 h | ≥24 h | ≥48 h | ≥48 h | ≥48 h |
| Battery lifespan | 7 years | 7 years | ~10 years | ~10 years | 10 years |
| 2026 price excl. VAT | 345 € | 570 € | 499 € | 810 € | 945 € |
Prices excl. VAT — Skysat catalog (Odoo), June 2026. Other references in the catalog: ACR GlobalFIX V5 Cat. 2 (835 €), AIS MOB1 / MOB2 beacons (307 € / 387 €), AIS SART safeSEA S200 (750 € — the AIS-SART is used to be located from a life raft, another function altogether), ready-to-deploy safety kits. Coding for France 70 €. See also the satellite communication comparison.
7. 5 workshop traps
Trap #1
Confusing AIS MOB with EPIRB/PLB.
Trap #1. An AIS MOB beacon works locally (AIS); for offshore rescue, you need 406 MHz.
Trap #2
Buying a beacon coded for another country.
Common with purchases abroad: the alert goes to the wrong center. Must be recoded before the first departure.
Trap #3
Never registering (or failing to update).
An unregistered beacon deprives rescuers of your file. On resale/boat change: re-register.
Trap #4
Choosing Cat. 2 when the program requires float-free.
Offshore or short-handed crew: if no one can grab the beacon, only a Cat. 1 will activate on its own.
Trap #5
Forgetting expiry dates.
Battery (7-10 years) and hydrostatic release unit (HRU) (expiry ~2 years): a beacon that "looks new" can be out of service. Self-test does not replace the schedule.
8. Which beacon for which program
- Coastal / day sailing, where you keep control → EPIRB1 Cat. 2 (499 €) or EPIRB3 Cat. 2 (810 €) if you want AIS + RLS. A PLB1 (345 €) as a complement on the skipper.
- Offshore / delivery / short-handed crew → EPIRB3 Pro Cat. 1 float-free (945 €): it activates on its own if the boat sinks quickly. Plus a PLB3 (570 €) on each watch crew member.
- Regatta, multi-boat, or "I want it to follow me" → the PLB3 AIS/RLS personal beacon is the most versatile.
- Man overboard recovery (crew member overboard) → an AIS MOB beacon (MOB1/MOB2), in addition to the boat's EPIRB — not instead of it.
And the workshop's honest take: the most expensive beacon poorly coded is worth less than a basic EPIRB1 properly registered. The priority budget is the 406 MHz + coding + registration; the rest is comfort (useful, but secondary).
9. FAQ
What's the difference between an EPIRB and a PLB?
The EPIRB is registered to the boat (and can be Cat. 1 with automatic float-free); the PLB is registered to a person, compact, manual activation. Both transmit on 406 MHz to Cospas-Sarsat satellites. Many boats carry both.
Is an AIS MOB beacon enough for offshore sailing?
No — it only alerts vessels within AIS range (a few miles). For offshore, you need a 406 MHz EPIRB or PLB.
Category 1 or 2?
Cat. 1 = automatic float-free (the boat sinks, the beacon activates on its own). Cat. 2 = manual activation. Offshore or short-handed crew: Cat. 1 is strongly recommended.
What is RLS?
The Return Link Service (via Galileo): an acknowledgment. An LED on the beacon confirms your alert has been received and located. Available on EPIRB3 / PLB3.
Do I need to register my beacon, and is it free?
Yes, it's mandatory. The beacon is registered free of charge in the national 406 MHz beacon registry (CNES / FMCC France) at registre406.cnes.fr, with your emergency contacts. For a vessel equipped with VHF/ASN, the MMSI and vessel station license come from the ANFR (maritime.anfr.fr). The coding of the beacon, however, is a technical service — we provide it for 70 € excl. VAT.
How long does the battery last?
Depending on the model, 7 to 10 years. Beyond that, mandatory replacement. On Cat. 1, the hydrostatic release unit (HRU) also needs periodic replacement (~2 years).
Can I buy a cheaper beacon abroad?
You can, but it will often be coded for another country: you'll need to recode it for France and re-register it, otherwise the alert goes to the wrong coordination center. The "good deal" comes with risk.
Transparency — Skysat distributes, codes and provides after-sales service for Ocean Signal and ACR beacons at the Carnac workshop (Morbihan). The recommendations in this guide are based on our coding, installation and maintenance practice, not on a supplier data sheet. When a simpler solution is enough for your program, we say so.
