Types Of Marine Emergency Beacons

It is crucial to have reliable marine emergency beacons on board. This guide clarifies the various types, addressing questions about their use and regulations.

I know choosing the right beacons can seem overwhelming. But keep reading to understand each type so you can make an informed decision.

Whether you’re a seasoned sailor or a boating novice, this guide is tailored to your needs, with explanations that are both comprehensive and accessible.

As a fellow mariner, I understand the importance of being prepared. Let’s explore these vital devices that could be your lifeline at sea.

At a Glance:

1️⃣ Along with flares, VHF radios are the arguably the most critical (and low-cost) beacons available for vessels.

2️⃣ EBIRPs enable a distress system to be activated globally and instigate the fastest rescue service.

3️⃣ PLBs provide a location for individuals who may have separated from the main body.

4️⃣ AIS devices provide a localized emergency location system.

5️⃣ Carrying flares is a legal requirement; however, I recommend that more flares be carried than the regulations state.

🆘 Types Of Emergency Beacons

The different distress beacons that provide a useful function in an emergency on a sailboat include the following:

  • VHF Radios
  • EPIRBs
  • Personal Locator Beacons (PLBs)
  • AIS
  • MOB devices
  • Flares (pyrotechnic and non-pyrotechnic)
  • RLS

VHF Radios

After life jackets, flares, and VHF Radios are a boat’s most important safety equipment. They represent the first line of defence for a boat captain facing potential or serious real-time problems.

Whereas all other distress signals are activated when the vessel is in a real and present emergency situation, a VHF radio can notify other vessels or the coastguard of a developing situation, placing them on standby. 

If the vessel is used in US tidewaters or in the open sea, VHF radios are only required for passenger boats that carry more than six passengers for hire. 

Even if not required, if the boat is used for offshore use, I recommend that VHF radios be carried.


Emergency Position Indicating Radio Beacons are specialized radio transmitters used in emergencies that are activated where there is a grave and imminent danger to the occupants of a boat.

EPIRBs are a last line of defence and must only be activated when radio transmissions are no longer possible.

Here’s a quick overview to understanding how an EPIRB works to provide you with a clearer picture.

The beacon’s primary transmission is on 406 MHz, and the most recent devices include a GPS location as part of the transmission “packets.”

A secondary transmission is sent on 121.5MHz and enables rescuers to use radio direction finder (RDF) equipment to locate the position of the EPIRB when close by.

The primary EPIRB signals are received by satellites in geostationary and polar orbits, which maintain an ongoing “listening watch” on the frequency.

The satellites relay the signal to the 38 Local User Terminals (LUTs) in member states worldwide.

The LUT processes the signal into a useful form and sends it to the nearest Mission control center (MCC.)

The MCC collates all the messages (there may be several received from different satellites and LUTs) and sends a single message to the most appropriate (by location) Rescue Coordination Center (RCC.)

The RCC assigns the rescue to the Coast Guard or another equipped rescue service that will activate the service.

Regulations only require EPIRBs to be carried on the following vessels:

  • Commercial fishing industry vessels operate on the high beyond the three-mile territorial limit.
  • Commercial fishing industry vessels that operate beyond three miles from the shore of the Great Lakes.
  • Uninspected vessels that carry more than six passengers.
  • Uninspected commercial vessels.

Personal Locator Beacons (PLBs) 

One type of marine emergency beacon you should be familiar with is the Personal Locator Beacon.

As the name implies, PLBs are distress transmitters attached to the person (normally the life jacket) instead of the vessel.

It makes them for individual crew emergencies (man overboard) where the boat may not be at risk. 

PLBs transmit on the same frequency as EPIRBs (406 MHz), and the chain of notifications is the same.  

Like EPIRBs, most PLBs also transmit on a location frequency of 121.5MHz to allow rescuers to use an RDF signal to hone in on the actual location of the transmitter.

Only PLBs that transmit on 406 MHz are approved as distress and location transmitters.

AIS (Automatic Identification System)

AIS was originally intended to enable ships and their locations to be identified and, therefore, to assist in avoiding collisions.

There are two classes of AIS transmitters.

AIS ClassTransmission Frequency (Underway)Transmission Frequency (At Anchor)Packet Information PointsTypical Range
Class AEvery 2-10 secondsEvery 3 minutes20 points of information20 miles
Class BEvery 3 minutes (under 2 knots) / Every 30 seconds (over 2 knots)Every 6 minutes6 points of information6 miles

Class A devices transmit much longer packets containing 20 points of information.

Primary Uses Of AIS Devices

There are several functions of AIS devices.

Collision Avoidance

The original purpose of AIS was to broadcast the vessel’s position, bearing, and speed, enabling other ships to take the necessary avoiding action to prevent a collision.

The AIS system generates alarms when vessels are nearby or have made course corrections that place the receiving boat in danger. It is particularly useful when the visibility is low.

AIS works like a real-time radar.

MOB (Man Overboard) 

AIS devices can be supplemented with individual MOB (Man Overboard) devices that the boat occupants wear.

If someone falls overboard, the MOB devices will transmit to the boat’s (and surrounding vessels) AIS transceiver, and the rescue can be started.  

Commercial Traffic Information

AIS enables interested parties (such as the ship managers) to locate the vessel’s position.

Coastal authorities use AIS to monitor the movement of marine traffic through their area.

In addition, fishing vessels use AIS to transmit and warn other vessels about the location of fishing nets enabling them to avoid becoming entangled.

Although most AIS systems should never be used as the primary distress beacon, as the technology across the different devices converges, systems such as AIS are being developed to include distress functionality.

There are AIS systems that are integrated with chart plotters. An example is the Garmin 7400/7600 series of chart plotters which includes an AIS distress signal device that can transmit emergency position reports when this component is activated.

These Garmin devices are enabled to provide the following:

  • Receive signals from Search and Rescue Transmitters (SART)
  • Provide Emergency Position Indicating Radio Beacons (EPIRB).
  • Full Man Overboard functionality.


The Return Link Service feature is an indication (e.g., a light or text display) on the beacon that confirms to the user that the distress signal from the beacon has been received and localized by the Cospas-Sarsat system and forwarded to government authorities for action.

It does NOT mean that a rescue has yet been organized/launched, only that the distress alert has been received and routed to the appropriate government agencies. 

An activated RLS-enabled beacon receives an automatic acknowledgment that its 406 MHz distress alert and location have been received.

When the RLS-enabled beacon receives the Return Link Message (RLM), it provides the user with the reassurance the distress alert has been received. This is visible on the beacon e.g.

MOB (Man Overboard) Devices

The Man Overboard Location Alert System (OLAS) is another type of marine emergency beacon that enhances safety at sea.

A range of MOB devices are available, which include the following:

  • Manual activation of an event on the chart plotter.
  • Personal units attached to the boat occupants signal the AIS device.
  • Bluetooth-enabled locators that activate when the connection is broken.
  • Video-based surveillance systems that detect an event (on large ships.)

Flares (Pyrotechnic And Non-Pyrotechnic)

Flares are essential marine safety equipment, a VHF radio, and life jackets. 

Although the US Coastguard requires a minimum number of flares to be carried, we recommend doubling the quantity if the vessel is to be used at night or in bad weather.

Parachute flares can signal an emergency, and handheld flares can be used to guide the rescuers to the location of the emergency.

📖 Read Next: Types Of Flares: Understanding Distress Pyrotechnics

⚖️ Differences Between EPIRBS, PLBS, And AIS MOB Devices

A common question when exploring marine emergency beacons is the difference between an EPIRB and a PLB. The table below lists the differences between EPIRBS, PLBS, and AIS MOB Devices.

RangeInternationalInternationalIf it does not have satellite functionality, the AIS signal transmits to a +- 5-mile radius.
Battery Life48 hours24 hours24 hours
FlotationYesCertain modelsYes
GPS locationOn newer devicesYesYes
RegisteredTo boatTo personTo boat
SizeBulky (fitted to the boat)Compact (easy to carry)Transceiver is bulky
ApplicationMarine onlyAnywhereMarine only
MOB FunctionsYesNoYes

📜 Regulations And Guidelines Governing The Use Of Beacons

The US Coast Guard regulations regarding the use of beacons are listed below.

  • PLBs are not mandated due to a lack of standards, and the ongoing reliability issues are a problem.
  • EPIRBs are mandated for specific categories of vessels (46 CFR Part 199 Subpart B for inspected vessels) and Vessels subject to SOLAS Regulation IV/7.
  • Varying numbers of flares must be carried on specific categories of vessels.

Duration And Range Of Different Types Of Beacons

To be designated as an EPIRB, the battery must last for at least 48 hours when activated.

PLBs and portable AIS transmitters are only designed to transmit for 24 hours.

EPIRBs and PLBs transmit on 406 MHz, which is received by satellites; therefore, they have a global range.

AIS devices may have a global satellite transmission range or be restricted to a VHF signal range.

🧰 Proper Storage And Maintenance Of Beacons

All marine distress signal beacon devices should be checked and maintained according to the manufacturer’s instructions.

The US Coastguard requires all flares and other emergency beacons to be within easy reach.

It is also vital that all of the regulatory requirements are complied with and where expiry dates are given that they are withdrawn from service.


What Is The Difference Between Category 1 And 2 EPIRB? 

There are two categories of EPIRB:

Category One EPIRBs: Have a hydrostatic switch that automatically instigates the emergency signal once it comes into contact with water.

To prevent a false transmission, the hydrostatic switch only activates when the switch exceeds 3 meters in depth.

Category Two EPIRBs have to be manually activated.

What Is The Difference Between EPIRB And SART? 

EPIRBs provide notification of an emergency when the boat’s occupants are in grave and imminent danger.

In this regard, they initiate a radio signal that the satellite systems receive and commence a chain of activities that lead to the location and rescue.

SARTs (Search And Rescue Transponder) are emergency location devices that assist the rescuers in accurately locating the survivors when in radar range.

When a radar scans the SART device, it responds by increasing the vessel’s radar image on the search vessel’s radar screen, making identification easier.

🔑 Key Takeaways

Knowing your emergency beacons is crucial for safety. The next step in your emergency preparations is to have all the essentials in your ditch bag.

There are several types of Marine Emergency Beacons available.

1️⃣ The two most important are flares and VHF radios.

2️⃣ If the vessel is traveling offshore, an EPIRB should be seriously considered.

3️⃣ Personal Locator beacons do not have the same battery life but still provide a useful function.

4️⃣ AIS and Man Overboard devices should be considered if appropriate for the boat’s normal uses.

I’m the founder and chief editor here at Sailing Savvy. I spent a decade working as a professional mariner and currently, I mix those experiences with digital publishing. Welcome, and I hope that we can be the hub you need for safe passage.