Man Overboard Device

1. AIS MOB beacons
   These transmit an AIS message on VHF to create a target with a bearing and range on the yacht’s displays, including ECDIS and plotters. Many also trigger a Digital Selective Calling, DSC, alert on Channel 70 to the mothership or, in newer models, to “all ships” nearby, depending on configuration. Crucially, AIS MOBs are intended for local rescue by your vessel and nearby traffic, they do not automatically contact shore authorities. That limitation is explicit in the European AIS-MOB standard EN 303 098.

2. Personal Locator Beacons, PLBs
   PLBs transmit on 406 MHz into the COSPAS SARSAT satellite network. That alert is routed to a rescue coordination center with your GPS position and, when available, homing aids on 121.5 MHz for the last meters of the search. Think of PLBs as the global reach option that directly engages formal Search and Rescue.

3. Electronic tethers and crew trackers
   These create a local alarm if a tag goes out of range or gets wet, prompting an immediate turn back while dropping a GPS mark. They are fast and simple, but they don’t notify other vessels or shore.

Why this matters to yachts

For owners and managers, a MOB device is inexpensive risk reduction that complements mandatory lifesaving gear under IMO and SOLAS regimes. On vessels required to carry AIS, typically ships of 300 GT and above, an AIS MOB integrates directly with existing bridge systems, making it easy for the watch to steer to the casualty without fiddling with new interfaces. For professionally crewed yachts, pairing AIS MOB on every lifejacket with at least a few PLBs in the grab bag ensures both immediate local recovery and escalated satellite alerting when the situation demands it.

Crews benefit because these devices shorten the loop between the splash and the helm’s reaction. Management teams benefit because device choice, carriage policy and drills can be standardized across a fleet, and compliance with evolving radio rules can be tracked centrally.

How MOB devices actually work, the short technical tour

• AIS MOB, when fired, sends specially coded AIS bursts with GPS position every few seconds. Plotters and ECDIS show a distinctive target and often draw a course-to-steer. The European harmonized standard also requires clear instructions and warnings that AIS MOB is for short range signaling, not a direct call to emergency services.

• DSC with AIS, Class M, is the new European approach for personal MOB transmitters. These devices alert via DSC on Channel 70, then track via AIS. The CEPT ECC Decision, often called the Class M rule, is being adopted in several European countries and, from 2025 in those waters, restricts AIS channels to Class M DSC-capable devices for off-ship uses like personal beacons. If you operate in Europe, check your inventory for Class M compliance before you sail.

• PLB, once activated, uses a 406 MHz burst to satellites monitored globally, pushing your position to a Maritime Rescue Coordination Centre. It is part of the GMDSS ecosystem alongside EPIRB on the vessel, but unlike an EPIRB it is assigned to the person, not the boat.

Comparison infographic (AIS MOB, PLB, Electronic tether)

Selecting and integrating for a yacht operation

Use this quick framework when specifying gear during a refit or updating your planned maintenance:

• Operating area and watch model, coastal day trips with tight bridge discipline favor AIS MOB, offshore passages where you might be alone on deck justify both AIS MOB and PLB for redundancy.

• Bridge integration, confirm your AIS, plotters and ECDIS render MOB symbols correctly and that your VHF supports the DSC modes your beacons use, individual or all-ships. Test the Channel 70 behavior dockside with a training mode if available.

• Regulatory posture in your cruising grounds, if you plan to cruise in European waters, verify Class M adoption on your flag and coastal states, and ensure any new units are Class M labeled to avoid becoming non-compliant during audits or port calls.

• Crew numbers and roles, issue AIS MOB to everyone and add PLBs for key roles or night watches. Make sure lifejackets are compatible with automatic activation options and that strobe lights are fitted and synced with beacon placement per the OEM manual.

Training and upkeep that actually saves lives

Devices are only half the story. Drills close the gap between electronics and seamanship. Schedule MOB recovery drills that practice a quick stop, a Williamson turn when appropriate, pickup alongside and lifting techniques for an unconscious casualty. Flag administrations regularly emphasize realistic MOB drills with recovery gear and a time standard, and surveyors can ask to see you perform one. Keep battery replacement dates in your PMS and verify registration data for PLBs and MMSI-related features after yard periods or crew changes.

Man Overboard Device alert process (technical diagram)

A real-world scenario that adds clarity

Night passage, 15 knots apparent wind, light swell. A deckhand stumbles and is gone from view. His lifejacket triggers the AIS MOB. The bridge alarm sounds on the VHF via DSC, the target pops up on the chart display and the OOW punches “navigate to target” while hitting the general alarm. The yacht turns, the rescue swimmer preps, and nearby traffic also sees the target. If the crewman had also triggered a PLB, shore-side SAR would already be reading his coordinates. This is what layered protection looks like, and it is exactly what these devices are built to deliver.

A man overboard device is a small, smart addition that changes outcomes. On a professionally run yacht, equip every lifejacket with AIS MOB, add PLBs according to the voyage profile, confirm bridge integration and train until the response is muscle memory. As regulations and radio standards evolve, especially in Europe, keep your equipment list current and your crew fluent. The goal is simple, if someone goes over the side, your yacht sees them, calls them in and gets them back on board fast.

FAQ: Man Overboard Devices For Yachts

Do AIS MOB devices alert the coast guard automatically?
No. AIS MOB beacons create a target on your yacht’s AIS/plotter and can trigger a DSC alarm on VHF, which alerts your vessel and nearby ships. They do not contact shore authorities by themselves. For that, carry a PLB registered to the crew member within the GMDSS ecosystem alongside the vessel’s EPIRB.

How far does a man overboard beacon reach in real conditions?
Expect 2 to 5 nautical miles to your own receiver in moderate seas, often farther if your yacht’s AIS antenna is high on the mast. Range drops in heavy chop because the person and the beacon antenna are low at the waterline. A PLB’s satellite alert is global, which is why many yachts layer AIS MOB and PLBs.

Do I need both AIS MOB and a PLB for my crew?
If you sail offshore or at night, yes, that pairing gives you immediate local homing via AIS and a parallel satellite alert via 406 MHz. In coastal day use with tight watch routines, AIS MOB alone may be acceptable, but many captains still add a few PLBs for higher-risk roles.

What is “Class M” DSC for personal beacons and does it affect me in Europe?
Class M refers to personal MOB transmitters that send a DSC alert on Channel 70 and then track on AIS. Several European administrations are adopting Class M rules, so check your flag and cruising states. If you cruise Europe in 2025, choose Class M-capable beacons to stay aligned with emerging requirements.

Will a MOB device work if the person is unconscious?
Only if it is fitted and configured correctly. Choose models with automatic activation on inflation or water contact, mount them high on the lifejacket, and pair with a bright strobe for visual acquisition. Drills should include recovering an unresponsive casualty so the crew practices the lift, not just the turn-back.

How do I test MOB devices without triggering a real rescue?
Use the manufacturer’s self-test mode and observe battery status and GPS acquisition without sending live distress traffic. If you need a full system test with live AIS/DSC, coordinate in advance with your port authority or coast radio station and perform it at the dock with clear “test” announcements.

Can AIS MOB targets show on my ECDIS and plotter automatically?
Yes, as long as your navigation suite supports AIS safety-related messages and is up to date. Verify symbol display, audible alarms, and “navigate to target” behavior during a dockside check. If your setup includes ECDIS, confirm MOB symbology per your vendor’s current software version.

How often should we service or replace MOB device batteries?
Follow the OEM interval, typically every 5 to 7 years, sooner if the device is triggered or if self-tests show low voltage. Add battery expiry to your planned maintenance system and replace O-rings and seals during service. After any refit or long lay-up, recheck function and revalidate registrations.

Are electronic “tethers” or wireless crew trackers enough on their own?
They are a helpful first layer, especially for solo or night watches, because they alarm immediately when a tag goes out of range or gets wet. However, they do not notify other vessels or shore. Treat them as a supplement to AIS MOB, not a substitute.

Where should I mount a MOB beacon on the lifejacket?
Mount on the shoulder or collar area so the antenna clears the water and the body. Avoid positions that get trapped under sprayhoods or straps when the jacket inflates. During fitting, don the jacket, inflate it, and confirm the beacon remains upright and visible with the strobe unobstructed.

Do I need an MMSI or programming for DSC features to work?
Yes. For individual-call DSC alerts, the beacon and your VHF need correct MMSI programming and pairing per the manual. After crew changes or a yard period, confirm MMSIs, radio settings, and that any “all-ships” DSC modes are compliant with local rules.

What training actually moves the needle in a real MOB?
Run short, frequent drills that time the sequence from splash to helm response, not just the turn. Practice night recovery with strobes, assign clear roles at the rail and on the bridge, and rehearse lifting an unconscious person with your chosen recovery gear. Capture drill timings and debrief to improve.

Will a beacon interfere with other electronics, like VSAT or Wi-Fi?
No. AIS and DSC use VHF channels designed for marine safety and coexist with your other systems. The key is proper antenna installation on the yacht and correct placement of the wearable unit on the person.

What should yacht managers standardize across a fleet?
Set a carriage policy, one AIS MOB per lifejacket and PLBs for high-risk watches, define battery and service intervals, and specify model families to simplify spares. Standardize programming, MMSI handling, and drill templates so crews transfer smoothly between yachts.

How does weather or sea state affect beacon performance?
More spray and higher waves reduce VHF line-of-sight, which can delay the first fix and shorten range. Many beacons mitigate this with frequent GPS updates and repeated transmissions, but mounting high and adding a strobe still make a big difference in rough conditions.

What’s a sensible budget plan for outfitting the crew?
Plan for one AIS MOB per issued lifejacket and add PLBs for night or offshore roles. Most units are in the low three figures per device, plus periodic battery kits and service time. Budget the training hours too, they often deliver the biggest performance gain per euro.