A sailor falls overboard at night. The crew needs to find that person quickly. On another boat, flooding forces everyone into a liferaft far offshore. They need rescue authorities to know what has happened and where to search.

Both are emergencies, but they make different demands on the equipment. That is why EPIRBs, personal locator beacons and AIS man-overboard devices should be understood by the jobs they do, rather than treated as three versions of the same gadget.

The useful starting question is simple: Who will receive this alert, and what can they do with it?

The EPIRB: raise the alarm beyond the boat

An Emergency Position-Indicating Radio Beacon is designed for maritime distress. Its 406 MHz transmission travels through the Cospas-Sarsat satellite system to the rescue coordination network. The beacon's identity helps authorities connect the alert with its registration record. A GNSS-equipped model can also provide a position.

An EPIRB belongs in the vessel's emergency plan. Everyone should know where it is, how to release it and how to use it according to its instructions. Some installations use a float-free bracket with a hydrostatic release; others require someone to remove the beacon manually. These arrangements are not interchangeable. Choose and mount the equipment for the boat, then inspect both beacon and bracket on their specified schedules.

NOAA's beacon overview explains the maritime role of EPIRBs and the personal role of PLBs. The distinction matters when deciding what stays with the boat and what stays with each sailor.

Modern EPIRBs may combine several signals. For example, the ACR GlobalFix V5 adds AIS locating transmissions, a 121.5 MHz homing signal and Return Link Service to its satellite distress alert. These are additional ways to support locating and communication, not promises about how quickly assistance will arrive.

The PLB: carry a personal route to the rescue network

A Personal Locator Beacon also uses the 406 MHz distress system, but is intended to be carried by an individual. That can be valuable for someone separated from the boat or moving between vessels.

The important word is carried. A beacon buried in a locker may be inaccessible when the wearer needs it. Decide how it will remain attached and reachable, including when the sailor is wearing gloves or an inflated lifejacket. Check the manufacturer's requirements for antenna deployment, operating position and flotation. Do not assume a small waterproof device will float or transmit effectively in any orientation.

Features vary. The Ocean Signal PLB3 combines satellite alerting with AIS and supports a specified lifejacket integration arrangement. Other PLBs have different activation and attachment arrangements. Learn the exact model rather than transferring habits from a different beacon.

A personal beacon can add resilience to the plan. It should not lead the crew to neglect the vessel's EPIRB arrangements, communications equipment or recovery skills.

AIS MOB: help the nearby boat find the person

An AIS man-overboard device broadcasts a locating signal that suitably equipped vessels within VHF radio range can receive. Its particular strength is local recovery: helping the yacht that lost a crew member, and potentially nearby vessels, locate the casualty.

Some models also use Digital Selective Calling to alert compatible VHF radios. That adds another alerting path, but the details depend on the device, radio and national rules.

A stand-alone AIS-MOB device does not send a 406 MHz satellite distress alert. Conversely, a product described as a PLB may include AIS as an additional feature. Read the actual transmission specifications rather than relying on a broad product category.

Reception is only part of the job. Does the boat's AIS receiver pass the target to the plotter? Does the plotter recognize the emergency target? Is there an audible alarm the watchkeeper can hear? Those questions need answers before departure.

Ocean Signal's MOB2 documentation recommends compatibility checks, particularly for older equipment, and explains vessel-MMSI programming. At the 6 November 2026 source check, its U.S. page marked MOB2 as unavailable for sale in the United States or Canada and stated that U.S. FCC authorization had not been obtained. Regional availability and DSC rules can change; check the exact model and current local requirements before buying or fitting one.

Return Link Service, or RLS, gives a compatible beacon an acknowledgment that its alert has been received. That feedback can be reassuring, but it has a specific meaning.

ACR's guidance explicitly says it does not mean a rescue has already been organized or launched. Do not interpret an acknowledgment light as an arrival estimate or a reason to stop following the beacon's operating instructions. Weather, distance and available rescue resources still matter.

Registration is part of readiness

A registration record connects an otherwise unfamiliar beacon identity with useful information about its owner and emergency contacts.

For U.S.-coded 406 MHz beacons, NOAA requires registration, updates when information changes and renewal every two years. Its system accepts specified U.S. country codes. A beacon coded for another country needs the appropriate registration route; contact the manufacturer or national authority rather than assuming NOAA can register any device purchased online.

Manufacturer warranty registration is separate. Completing it does not establish that rescue authorities have your beacon details.

MMSIs are another identity system. U.S. Coast Guard guidance for U.S. MMSIs distinguishes domestic recreational use, international voyages and portable handheld radios. Follow the route that fits your operation. For an AIS/DSC MOB beacon, distinguish its factory identity from the vessel MMSI it may be programmed to call.

Fit the beacon as part of the lifejacket system

A beacon that fits inside the cover is not necessarily correctly installed. Mounting, lanyards and activation ribbons must not obstruct inflation, antenna deployment or access to the manual controls.

Use instructions from both manufacturers for the exact combination. Some lifejacket makers publish model-specific fitting guides; Mustang Survival's Elite 190 page is one example. If the combination is unclear, ask the manufacturers or a competent service provider before improvising.

Include batteries, inflators, cylinders, lights and release mechanisms in the maintenance record. Their service dates need not coincide.

A drill that does not send a distress alert

Make this a dry briefing first, with live activation controls left alone:

  • Point out every beacon and explain who it alerts
  • Have each sailor describe how they would reach their equipment
  • Review the model's activation instructions without operating the distress control
  • Check registration details, emergency contacts and service dates
  • Inspect attachment and lifejacket integration against the relevant guides
  • Locate the radio and plotter's emergency-target guidance and alarm settings
  • Perform only the manufacturer's authorized self-test, observing its frequency limits and instructions
  • Rehearse lookout, helm, communication and recovery roles using a clearly identified training scenario

Never activate a live beacon simply to see whether somebody receives it. Proper self-tests and a practiced crew make a stronger safety plan than a collection of unfamiliar devices.

Research dated 18 October 2026; manufacturer and NOAA source pages checked 6 November 2026. Recheck regional approvals and current model instructions before purchase or installation.