The essentials in 30 seconds
- 3 technologies, 3 uses: the EPIRB protects the boat (activated by sinking, global satellite alert), the PLB protects the person (worn on the body offshore), and the AIS MOB alerts nearby boats within a 4-8 NM radius in seconds.
- French legal framework — division 240: EPIRB mandatory beyond 60 NM from shore. PLB and MOB recommended but not mandatory for crewed vessels. In OSR racing, equipment is mandated by class (IMOCA, Class40, etc.).
- 2026 generation: modern beacons (Ocean Signal EPIRB3, PLB3, MOB1) combine 406 MHz Cospas-Sarsat + local AIS + RLS (Return Link Service confirming receipt by the CROSS) + NFC for transmitting medical data.
- Workshop verdict: coastal solo = personal MOB1 on lifejacket (291 $). Coastal crewed = MOB1 + 1 collective PLB. Offshore = boat EPIRB + PLB per crew member + MOB1 on lifejacket (~1,500-2,000 $ total for a 4-person sailboat).
- Mistake #1: relying on AIS MOB alone offshore. The 4-8 NM range only works if there is a boat nearby — in the middle of the Atlantic, AIS MOB alone will not save anyone without an EPIRB or PLB that uses satellite.
A distress beacon is not chosen like a handheld GPS. It is the equipment that decides, sometimes, whether you are rescued in 2 hours or 2 days. The three technologies (EPIRB / PLB / AIS MOB) address three different needs — and choosing the wrong one is like buying a parachute to go sailing.
This article distinguishes the three families, outlines the French legal framework (division 240) and international standards, presents the references stocked by Skysat, and provides a workshop verdict by navigation program. For the VHF/AIS Class B that complements this system, see our Fixed vs portable VHF + AIS Class B for sailboats.
The three families of distress beacons
EPIRB — Emergency Position Indicating Radio Beacon
Boat-mounted beacon, anchored in the cockpit or helm station, in a hydrostatic housing (Category 1) or manual mount (Category 2). Transmits on 406 MHz to the global Cospas-Sarsat satellite system upon activation. Global coverage, 24/7, anywhere on the planet. Minimum transmission duration guaranteed for 48 hours at -20 °C. Requires ANFR registration in France (free) with a dedicated MMSI.
PLB — Personal Locator Beacon
Personal version, worn on a lifejacket or immersion suit. Same frequency and satellite system as the EPIRB (406 MHz Cospas-Sarsat) but with a smaller battery — minimum transmission duration guaranteed for 24-30 hours. Separate ANFR registration per individual. Essential for solo offshore racing and crewed offshore passages where each person must have their own beacon.
AIS MOB — Automatic Identification System Man Overboard
Small beacon triggered by water contact, transmitting on local VHF (162 MHz) over the AIS network. Alerts boats within a 4-8 NM radius in seconds — but not the global satellite system. Serves as a short-range complement, not a replacement for EPIRB/PLB.
French legal framework — division 240 and obligations
The division 240 (order of March 11, 2008, as amended) governs the safety equipment required for recreational vessels ≤ 24 m in metropolitan France.
- More than 6 NM from shore (offshore category): no specific beacon required, but a fixed VHF radio is mandatory.
- More than 60 NM from shore (oceanic category): 406 MHz satellite beacon mandatory, along with a fixed VHF radio with ASN (DSC) and registered MMSI.
- Personal equipment: not mandatory but strongly recommended for offshore crews (1 PLB per person minimum, ideally + 1 AIS MOB on the lifejacket).
For races governed by World Sailing OSR rules (Offshore Special Regulations) — IMOCA, Class40, Mini, Figaro, RORC — equipment requirements are stricter:
- Boat EPIRB + personal redundancy per crew member (PLB + MOB1).
- MOB1 activation tested systematically before each departure.
- Manufacturer registration and inspection within the last 12 months.
EPIRB — boat-mounted, global satellite alert
The EPIRB is the reference equipment for offshore navigation. Skysat stocks the Ocean Signal range, which has been the European leader since 2018.
Ocean Signal EPIRB3 — Category 2 + AIS + RLS
The Ocean Signal EPIRB3 cat.2 (810 $) is the Category 2 reference (manual activation) with a wall-mount bracket in the helm station. 2024 generation integrating 406 MHz Cospas-Sarsat + local AIS (alerts nearby boats simultaneously) + RLS Return Link Service (the satellite confirms back to the unit that the alert has been received) + NFC for rapid transmission of medical data.
Ocean Signal EPIRB3 Pro — Category 1 hydrostatic
The EPIRB3 Pro cat.1 (785 $) adds a hydrostatic housing: if the boat sinks, the beacon is automatically released at 4 m depth, floats to the surface, and activates. Essential for oceanic or solo sailing (the skipper may be unconscious or already in the water).
EPIRB3 vs older generations — key differences
- RLS (Return Link Service): new 2023+ standard. The beacon receives visual/audible confirmation that the CROSS has received the alert, which reassures the crew and changes behavior during the wait.
- Integrated AIS: in addition to satellite, transmits on local VHF to alert boats within a 4-8 NM radius (time-saving if traffic is nearby).
- NFC: allows a rescuer to read pre-recorded medical data (blood type, allergies, medical history) by approaching their smartphone to the beacon.
- Battery life: 10 years before replacement by the manufacturer. Minimum transmission duration guaranteed for 48 hours at -20 °C.
PLB — personal, offshore and racing
Ocean Signal PLB3 — personal 406 MHz + AIS + RLS
The Ocean Signal PLB3 (570 $) is the 2026 reference PLB, functionally equivalent to the EPIRB3 in a personal format. Same 406 MHz Cospas-Sarsat system, same local AIS, same RLS, same NFC for medical data. Compact 14 × 6 × 3 cm, 150 g — fits in a lifejacket pocket or clips onto an immersion suit.
- Activation: manual, pull the pin and deploy the antenna. No automatic activation on water contact (vs. MOB1).
- Transmission duration: 24 hours minimum at -20 °C (vs. 48 hours on EPIRB).
- Standby battery life: 7 years before replacement by the manufacturer.
- Registration: separate per individual (ANFR France, free, online).
For whom: every offshore crew member should have their own PLB. It is the survival assurance if the boat sinks (the EPIRB is on the boat, not with you) or if you are alone on board (solo skipper, offshore courier).
AIS MOB — local alert in seconds
Ocean Signal MOB1 — reference AIS MOB for sailboats
The Ocean Signal MOB1 (291 $) is the most widely deployed AIS MOB in recreational sailing and offshore racing. Tiny format (40 × 80 × 25 mm, 80 g), fits in a lifejacket pocket. Activates automatically when the lifejacket inflates on water contact (mechanical lanyard connected to the lifejacket’s trigger).
- Transmission: AIS Class M on 162 MHz, GPS position every 5 seconds for 24 hours minimum.
- Practical range: 4-8 NM in calm seas, 2-5 NM in rough seas — depends on the height of the AIS receiver’s antenna.
- ASN-DSC alert: in addition to AIS, triggers a VHF DSC distress call on channel 70, heard by nearby boats and CROSS stations.
- Battery: 7 years of standby life before replacement by the manufacturer. No RLS on this generation.
Critical limit: AIS MOB is useless in the middle of the Atlantic without a boat within 5 NM. It saves lives in busy coastal areas (English Channel, Bay of Biscay, Mediterranean), not in isolated offshore waters.
Complements — MOB buttons on the helm
The Navico NMEA 2000 MOB button (175 $) is wired to the helm and automatically triggers an MOB position marker on all B&G/Simrad/Lowrance chartplotters on board. Complements the AIS MOB without replacing it.
The Fell Marine MOB+ (258 $) is a wireless engine kill switch worn by the skipper. If the skipper falls overboard (and thus moves away from the sensor), the engine automatically stops. Critical safety for solo sailing or reduced-crew motorized passages.
Technical comparison chart
2026 distributor prices in USD, ANFR registration included but excluding any installation/configuration fees.
| Criteria | EPIRB (boat) | PLB (personal) | AIS MOB |
|---|---|---|---|
| Skysat 2026 reference | Ocean Signal EPIRB3 / EPIRB3 Pro | Ocean Signal PLB3 | Ocean Signal MOB1 |
| Price (USD) | 785-810 | 570 | 291 |
| Transmission frequency | 406 MHz Cospas-Sarsat + AIS 162 MHz | 406 MHz Cospas-Sarsat + AIS 162 MHz | AIS 162 MHz + DSC 156.525 MHz |
| Alert range | Global (satellite) | Global (satellite) | 4-8 NM (local VHF) |
| Response time | 30 min to 2 h via CROSS | 30 min to 2 h via CROSS | Seconds (if boat nearby) |
| Activation | Manual (cat. 2) or hydrostatic (cat. 1) | Manual (pin + antenna) | Automatic on lifejacket inflation |
| Transmission duration | 48 h at -20 °C | 24 h at -20 °C | 24 h at -20 °C |
| Format | Boat-mounted housing (~ 30 × 12 × 10 cm) | Compact pocket size (14 × 6 × 3 cm) | Tiny, lifejacket pocket (4 × 8 × 2.5 cm) |
| Standby battery life | 10 years | 7 years | 7 years |
| RLS (Return Link Service) | Yes (EPIRB3 / EPIRB3 Pro) | Yes (PLB3) | No |
| Registration | ANFR France, boat MMSI | ANFR France, individual ID | Boat or individual MMSI |
| Primary use | Offshore ≥ 60 NM, transatlantic, OSR racing | Offshore crewed, solo, OSR racing | Coastal, crewed, offshore complement |
Workshop verdict by navigation program
Coastal cruising (≤ 6 NM, day sails)
Minimum recommended: 1 MOB1 (291 $) on the helm’s lifejacket. Optional: 1 Navico NMEA 2000 MOB button (175 $) at the helm for chartplotter markers. Total budget: 300-470 $ USD.
Offshore cruising (6-60 NM, multi-day trips)
Recommended: 1 Ocean Signal EPIRB3 cat.2 (810 $) on board + 1 MOB1 per crew member minimum. For solo skipper: add Fell Marine MOB+ (258 $). Budget for 4 crew: ~ 2,000-2,300 $ USD.
Oceanic offshore (≥ 60 NM, transatlantic)
Mandatory (division 240): 1 Ocean Signal EPIRB3 Pro cat.1 (785 $) with hydrostatic release. Recommended: 1 PLB3 (570 $) per crew member + 1 MOB1 per lifejacket. Budget for 4 crew: ~ 4,500-5,000 $ USD.
Offshore racing IMOCA / Class40 / Mini / Figaro
Mandated by OSR: hydrostatic EPIRB + personal PLB + MOB1 per lifejacket + race tracking beacon (YB Tracking YB3 portable (789 $) or equivalent). Budget for a solo skipper: ~ 2,000-2,500 $ USD, excluding race tracking beacon. The MOB1 beacon must be tested systematically before each departure.
4 observed purchasing mistakes
Beacon mistakes — seen in the Skysat workshop
- Buying an old generation without RLS. RLS (Return Link Service) was introduced in 2023 on Ocean Signal’s 3rd generation. Without RLS, you activate the beacon and wait 2 hours in distress without knowing if anyone received your signal. With RLS, the unit visually confirms receipt by the CROSS — psychologically and operationally, it makes all the difference.
- Not registering the beacon. An unregistered beacon works technically but the CROSS receives the signal without knowing WHO to alert (relatives, on-board medic, owner). Identification delay: an additional 30 min to 2 h. Registration is free, online, takes 10 minutes. Do it as soon as you receive the beacon, not "someday."
- Relying on AIS MOB alone offshore. The 4-8 NM range is effective in busy coastal areas. In the middle of the Atlantic 1,000 NM from shore, AIS MOB alerts no one. Satellite EPIRB or PLB are essential. AIS MOB is a local complement, not a replacement.
- Storing the beacon in the bottom of a locker. A Category 2 EPIRB must be within easy reach from the cockpit (manual activation). A Category 1 must have its hydrostatic housing unobstructed. A PLB and MOB1 must be on the lifejacket, not in a dry bag at the bottom of the cabin. If you cannot grab and activate the beacon in 10 seconds under stress, it is poorly positioned.
FAQ — Distress beacons for sailboats in practice
How long before rescue arrives after activating an EPIRB?
In France, the CROSS (Gris-Nez, Étel, La Garde, Antilles-Guyane) receives the 406 MHz signal via satellite in 5-15 minutes, depending on satellite position at the time. The time to deploy rescue assets then varies: SNSM within 30 min to 2 h for coastal zones, helicopter or diverted vessel 2-12 h offshore. RLS confirms back to the unit that the alert is being processed, which helps psychologically during the wait.
Do I need an EPIRB or PLB for a crewed coastal passage?
Neither is mandatory under 6 NM from shore. If you want to invest, a personal PLB (570 $) on the skipper covers better than an EPIRB alone (800 $) because the PLB protects the person even if they leave the boat. For 60% of our coastal customers, we recommend PLB + MOB1 (~ 860 $ total) over EPIRB alone.
Does AIS MOB trigger an automatic CROSS alert?
No, AIS MOB only alerts boats within a 4-8 NM radius via VHF AIS. The MOB1 also transmits a DSC distress call on channel 70 — if a nearby boat or shore station receives this DSC, the CROSS is notified within minutes. But without a nearby boat, AIS MOB alone does not trigger an official alert.
How much does a manufacturer inspection/revision of an EPIRB cost?
Ocean Signal’s EPIRB3/PLB3/MOB1 inspection costs 80-120 $ USD at an approved workshop. Recommended frequency: every 5 years for cruising, 12 months for OSR racing. Replacement of the sealed battery costs 150-250 $ USD and can only be done by an approved workshop (DIY is not possible — the beacon loses its registration and certification). Skysat is an approved Ocean Signal service center in France.
Can I activate the beacon for testing without triggering an alert?
Yes, all Ocean Signal 3rd generation beacons have a "self-test" mode that checks electronics, battery, internal GPS, and antenna without transmitting to Cospas-Sarsat. Test monthly for coastal cruising, weekly for racing. For the MOB1 specifically, there is a "TX test" mode that transmits a very short AIS signal (1-2 transmissions) audible to nearby boats but identified as TEST by receivers — useful for validating real-world range from the boat.
EPIRB on a 7 m sailboat — relevant or overkill?
On a 7 m sailboat used for summer coastal cruising, an EPIRB is likely overkill — 800 $ for 90% coastal use. At this size, the combo MOB1 (291 $) + PLB3 (570 $) covers most realistic situations for ~ 860 $ total. An EPIRB becomes relevant once the program includes night sailing, inter-archipelago transfers, or trips > 30 NM from shore.
What’s the difference between Ocean Signal, McMurdo, and ACR?
Three major brands in the European market. Ocean Signal (UK, acquired by ACR/Drew Marine in 2018) has been the standard for sailboat safety in France since 2020 — compact products, rational design, RLS since 2023. McMurdo (UK) is the historic SOLAS commercial brand, with a more pro-oriented range. ACR (USA) is the US leader, present in Europe but with slower service. Technically, all three are equivalent — Ocean Signal wins on compactness and France’s network of approved service centers.
Skysat is an approved Ocean Signal distributor and service center in France. This article reflects our experience equipping over 200 sailboats with safety gear since 2018, from coastal solo sailing to OSR offshore racing. 2026 distributor prices are indicative and in USD, excluding ANFR registration (free, to be done by the owner) and excluding periodic manufacturer inspection/battery replacement.
