EPIRBs and PLBs, explained

Cospas-Sarsat, the international satellite system, stopped processing 121.5 and 243 MHz beacons on 1 February 2009, so only 406 MHz beacons alert by satellite. The 121.5 MHz transmitter inside a 406 MHz beacon is a local homing signal for rescuers, which the change did not affect; 47 CFR 80.1061 requires every 406 MHz EPIRB to contain one. Class A, B, S and INMARSAT-E EPIRBs may not be made, imported, sold or used (47 CFR 80.1053).^{[15][20][2][1]}

NOAA says the US Mission Control Center receives the alert, matches the beacon's ID against the registration database and adds the registration data, then passes it to the closest US search and rescue service, such as an Air Force or Coast Guard rescue coordination center. The Coast Guard says one of the first things its rescue coordination center watchstanders do is try to reach the owner, to rule out an accidental activation.^[8][9][15]

The Coast Guard recommends a 406 MHz EPIRB, preferably with an integral GPS receiver. It says an alert through the geostationary satellites carries no location unless the EPIRB has one; its federal requirements guide says that without a GPS position the system takes about an hour on average, almost always under two, to work one out, while a GPS-equipped EPIRB gives an immediate position.^[15][19]

NOAA says an EPIRB transmits for at least 48 hours once activated, and a PLB for at least 24.^[10]

• Category I EPIRB

  Capable of floating free of a vessel and activating automatically if the vessel sinks (46 CFR 161.011-5). NOAA says it sits in a bracket with a hydrostatic release.^[7][10]

• Category II EPIRB

  Removed from its mounting bracket by hand and activated (46 CFR 161.011-5). The Coast Guard says some models also switch on in water.^[7][15]

• Personal locator beacon

  A portable, handheld beacon for personal use (Coast Guard), activated by hand (NOAA). ACR says a PLB must be held out of the water or attached high on a life jacket.^[16][10][25]

The Coast Guard says EPIRBs are designed to be mounted on a vessel and are typically larger and more powerful than PLBs. ACR's comparison: an EPIRB floats upright to transmit, runs at least 48 hours at -20°C, can be water-activated and is registered to the vessel; a PLB need not float, runs at least 24 hours, is activated by hand and is registered to the person. NOAA says a PLB used on a boat should be registered with the boat's call sign, MMSI, AIS MMSI, name and home port as well.^[16][25][12]

ACR calls an EPIRB generally preferred for boaters, and suggests a PLB as a backup carried on the person and as the main beacon for someone alone on deck.^[25]

A satellite messenger is a different service. Garmin says its inReach Mini 2 needs an active satellite subscription before its SOS can be used, and that pressing SOS sends a message to the Garmin Response team, which notifies emergency responders. The NTSB says alerts from such devices go to a commercial satellite and a coordination center run by the device's service company.^[35][22]

The Coast Guard's federal requirements guide does not list an EPIRB as required for recreational boats; it lists one under equipment beyond the minimum federal requirements that boats operating offshore should consider. It also says the FCC does not require most recreational operators to hold an individual license to operate an EPIRB. If you do carry a 406 MHz beacon, registering it is mandatory.^[19][2][5]

47 CFR 80.1061(f) makes it mandatory to register each 406 MHz EPIRB with NOAA before installation and to keep the information up to date, and requires owners to tell NOAA in writing when the vessel or EPIRB changes hands, the EPIRB moves to another vessel, or any other registration information changes. 47 CFR 95.2905 requires each PLB owner to register with NOAA and report any change of ownership or other registration information.^[2][5]

NOAA says registration is free, is valid for two years and must be renewed, with reminders by email or letter starting two months before. A second-hand beacon is registered by its new owner as if new, and the Coast Guard says the seller must first change its status to sold or transferred. A beacon must be registered in the country it is coded for, and NOAA recommends owning one coded for the country where you live.^[12][11][15]

An unregistered or lapsed beacon still transmits, but the Coast Guard says an unregistered EPIRB's alert may take as much as two hours longer to reach it. NOAA says failing to register a beacon, or to report a change of ownership, could bring penalties or fines from the FCC, and a Coast Guard bulletin of April 2025 (MSIB 02-25) says the Coast Guard is continuing to enforce the registration rule.^[12][15][18]

Return Link Service shows on the beacon that the distress alert was received and forwarded to the authorities; NOAA and ACR both say it does not mean a rescue has been launched. NOAA says RLS-equipped EPIRBs and PLBs coded for the US have been legal for sale and use in the US since 1 June 2022. ACR says the acknowledgement is aimed to reach its GlobalFix V6 within 30 minutes of activation, though it may take significantly longer.^[9][24]

Some EPIRBs and PLBs also transmit an AIS alert. Ocean Signal says an AIS EPIRB alarms AIS-equipped vessels within VHF range soon after activation, often the quickest help. When you register one, NOAA says to enter the beacon's own AIS MMSI, which should start with 970, 972 or 974. ACR's GlobalFix V6 has no AIS; ACR's AIS EPIRB is the GlobalFix V5 AIS.^[34][12][23]

The Coast Guard's guide says to mount an EPIRB to float free, following the maker's instructions, if possible, and otherwise to make sure it is readily accessible. The Coast Guard says a Category I EPIRB should be purchased if it can be installed properly, and NOAA says it is very important to mount one outside the cabin, where it can float free of a sinking vessel.^[19][15][10]

The makers give their own rules. ACR says the GlobalFix V6 housing is for external installation only, on a vertical surface where the beacon can float free, at least 1.0 m from any steering compass, away from strong magnets such as loudspeakers and out of a radar beam. Ocean Signal says to mount its EPIRB3 Pro housing high on the superstructure, free from obstruction and where it cannot be trapped whatever the angle of the sinking vessel, with at least 150 mm (6 in) clear around it and 1.0 m from a steering compass, and to install the EPIRB3's manual bracket inside the vessel, so heavy seas cannot dislodge and set off the beacon.^[24][32][34]

There is no single release depth. ACR's V6 manual gives 4 m maximum, a Coast Guard inspection sheet says a hydrostatic release usually acts at 3 to 5 meters, and NOAA gives 3 to 10 feet; check the figure for your model.^[24][17][10]

The hydrostatic release has its own expiry. ACR says to check monthly that the V6's HydroFix release (P/N 9490.1, the only one to use) is within its expiry, two years after installation, and its V6 page says to mark the installation date and that the unit is good three years from manufacture. Ocean Signal says to replace the EPIRB3 Pro's HR1E (P/N 701S-00608) two years after installation, with the expiry label no more than three years from its date of manufacture.^[24][23][32]

NOAA says to keep a Category II EPIRB in the most accessible spot on board. ACR says some owners keep one without its bracket in an abandon-ship bag, which it calls OK if the bag stays in a dry spot.^[10][25]

ACR's GlobalFix V6 Category II is taken out of its bracket and put in the water, where it switches on; ACR says not to leave it in the bracket if the boat is in danger of sinking, and never to tether an activated V6 to the boat, because a sinking boat can pull it under or you can drift away from it. Ocean Signal's EPIRB3 cannot switch on in its bracket; out of it, it activates on contact with water, with the antenna fully extended, or by hand on deck or in a life raft.^[24][34]

The Coast Guard says some EPIRBs must be floating in the water for their antenna to work at peak efficiency, and that the maker's instructions say whether yours should be.^[17]

On ACR's ResQLink 400, you unclip the antenna latch, rotate the antenna 90 degrees upright and hold the ON/OFF button for 2 seconds. ACR says not to cover the activated beacon with any body part, water or clothing, because that blocks its GPS; that it will not work submerged and must be held above the water; and to leave it on until you are rescued.^[30][29]

EPIRB transmissions may be used only in emergencies (47 CFR 80.1161), and PLBs only for distress and safety of life (47 CFR 95.2931). The Coast Guard says testing a 406 MHz EPIRB by letting it radiate outside a shielded container is illegal. NOAA says the beacon's own self-test changes its code so ground stations ignore it and no rescue center is notified, needs no approval, and that any activation other than self-test is read as a distress signal.^{[3][6][15][14]}

The Coast Guard's EPIRB inspection sheet makes monthly testing mandatory only on vessels required to carry a 406 MHz EPIRB. ACR recommends a ResQLink self-test once a month, or at least two weeks before a trip, in the first 5 minutes of an hour; it says the battery allows 60 self-tests and 20 GPS self-tests over its 5-year life. Its V6 manual recommends a monthly self-test and a GNSS test at least every six months, with 60 GNSS tests over the battery's life, and says to test the V6 only in the first five minutes of an hour, because the test sends a short burst on 121.5 MHz.^[17][30][24]

If an EPIRB goes off by mistake, 47 CFR 80.335(e) says to contact the nearest Coast Guard unit or appropriate rescue coordination center immediately and cancel the alert. NOAA says to call the Coast Guard for an EPIRB (1-855-406-8724) and the Air Force for a PLB (1-800-851-3051). ACR says its V6 sends its first alert about 50 seconds after switch-on, so switching it off within that time means no distress alert has been sent, but its manual still says to contact the nearest search and rescue authority and report any false alert. Thresholds differ by model, so follow your maker's manual. A 2013 FCC advisory says even a brief inadvertent activation can generate a false alert and is a rule violation that may bring monetary penalties.^{[4][13][24][21]}

NOAA says most false alerts happen during testing, handling, repair and installation. The Coast Guard's MSIB 02-25 gives NOAA's figures for distress alert devices: 88, 78, 80, 60 and 104 distress alerts in 2020 to 2024, against 2,014, 1,971, 2,209, 2,066 and 2,149 false alerts.^[13][18]

NOAA says to replace the battery no later than the date on the beacon's label, or after an activation in an emergency. The Coast Guard says to use the battery the maker specifies, fitted by a dealer the maker approves; the wrong type may not run for the full duration.^[12][15]

For the models we cover, the makers say the owner must not replace the battery. ACR gives the GlobalFix V6 a 10-year battery replacement period, says to replace it after any activation, even a brief one, and not to replace it yourself; Ocean Signal gives the EPIRB3 10 years and says replacement must be done at its authorised centres; ACR's ResQLink battery is replaced after 5 years or emergency use, through a factory-authorized battery replacement center. ACR's battery page says you may have to ship the beacon, and gives no price.^{[24][34][30][26]}

NOAA says a beacon you dispose of must be made inoperable and must not go in the trash, because that could set off a false alert, and asks you to update its registration. The makers say the owner must not replace the battery, so ask the maker or an authorised centre to deal with it.^{[9][13][24][34]}

The two ACR V6 listings are the same beacon in its Category I housing and its Category II bracket. ACR lists the HydroFix release (9490.1) among accessories rather than clearly in the Category I box, so confirm it is included. The EPIRB3 Pro is Ocean Signal's Category I version of the EPIRB3, with a hydrostatic release in its housing. Of the PLBs, the 410 RLS is the Return Link version of the 400; ACR says its RLS light does not confirm a rescue dispatch or give an arrival time.^{[23][33][31][28]}

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  ACR · Safety Equipment

  ACR GlobalFix V6 EPIRB, Category I Float-Free

  ACR's GlobalFix V6 (model RLB-43) in its Category I float-free housing; ACR's US part is 2853: GPS, Galileo and GLONASS, a 121.5 MHz homer and Return Link Service, but no AIS. ACR gives it a 10-year battery replacement period and over 48 hours at -20°C, and says only an authorized center may replace the battery. Its HydroFix release (9490.1) must be replaced two years after installation, and ACR's V6 page also caps it at three years from manufacture, so check the label; ACR lists it as an accessory, so confirm it is in the box. Check the beacon is coded for the US, and register it with NOAA before installing it.

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• 
  ACR · Safety Equipment

  ACR GlobalFix V6 EPIRB, Category II Manual Bracket

  The same GlobalFix V6 in its Category II manual bracket (ACR's US part 2854). ACR says it is taken out of the bracket and switches on in contact with water, warns not to leave it in the bracket if the boat is in danger of sinking, and says never to tether it to the boat. GPS, Galileo and GLONASS, Return Link Service, no AIS; 10-year battery replacement, by an authorized center only. Check it is coded for the US and register it with NOAA.

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  Ocean Signal · Safety Equipment

  Ocean Signal EPIRB3 Pro, Category I with AIS

  Ocean Signal's Category I EPIRB with an AIS alert (SKU 702S-03933), in an auto-release housing with an HR1E hydrostatic release, plus Return Link Service, a 72-channel multi-GNSS receiver and a 121.5 MHz homer. Ocean Signal gives a 10-year battery replacement period and over 48 hours at -20°C, and says to replace the HR1E (701S-00608) two years after installation, with an expiry label no more than three years from its date of manufacture. When registering, NOAA says to enter the beacon's own AIS MMSI. Check it is coded for the US.

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  Ocean Signal · Safety Equipment

  Ocean Signal rescueME EPIRB3, Category II with AIS

  Ocean Signal's Category II EPIRB with an AIS alert (SKU 702S-03932), supplied with a manual-release bracket that Ocean Signal says to mount inside the boat. It cannot switch on in the bracket; out of it, it activates in contact with water or by hand. GPS, Galileo and GLONASS, Return Link Service and a 121.5 MHz homer; 10-year battery replacement and over 48 hours at -20°C, at an authorised centre only. Check it is coded for the US.

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  ACR · Safety Equipment

  ACR ResQLink 400 Personal Locator Beacon

  ACR's ResQLink 400 PLB (model PLB-400, US part 2921), with GPS and Galileo, a 121.5 MHz homer and visible and infrared strobes, and no Return Link Service or AIS. ACR calls it buoyant, so it can be retrieved, but says it will not work submerged: hold it above the water with the antenna up. The battery is replaced after 5 years or emergency use, through ACR's authorized centers. Register it with NOAA.

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  ACR · Safety Equipment

  ACR ResQLink 410 RLS Personal Locator Beacon

  The Return Link version of the ResQLink 400 (model PLB-410; ACR's US part is 2931, but the listing shows no part number, so check it is coded for the US): GPS and Galileo, a 121.5 MHz homer, and a blue light that shows the alert was received. ACR says that light does not confirm a rescue dispatch or give an arrival time. Buoyant but, like the 400, it must be held above the water to work; the battery is replaced after 5 years or emergency use, through an authorized ACR center. Register it with NOAA.

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Carriage rules for commercial vessels, which do not apply to recreational boats; state rules; fine amounts, since the official sources disagree and the figures we found were out of date; McMurdo and Kannad EPIRBs whose pages say US authorization is pending; ACR's older GlobalFix V4, which ACR lists as Legacy; and coverage, range and position-accuracy claims beyond NOAA's own. Check that any beacon you buy, new or used, is authorized for sale in the US and coded for the US.