Marine Emergency Beacons When Rescue Cannot Wait
02:17 HOURS. The vessel is taking water faster than the pumps can remove it. The crew are about to enter a rescue chain in which every piece of equipment has a different job.
Alert
The EPIRB places the emergency into the international satellite search-and-rescue system.
Locate
AIS-SART or radar SART equipment helps rescue assets close the final distance to the survival craft.
Communicate
A GMDSS handheld radio gives survivors direct voice contact when ships or rescue units are within radio range.
Marine emergency beacons are often described as though they all perform the same task. They do not. An EPIRB raises the long-range distress alert. An AIS-SART or radar SART helps rescue units find survivors during the final approach. A survival craft radio gives the crew a voice once assistance is close enough.
Understanding those differences matters because a strong emergency communications arrangement is not built around one impressive device. It is built around several compatible devices, each positioned, maintained and registered for its own part of the rescue.
This guide follows a fictional abandonment scenario to explain how the equipment works together. The scenario is illustrative, but the equipment roles and technical distinctions are real.
The liferaft clears the vessel. The painter is released. The EPIRB is activated and secured where it has a clear view of the sky. Somewhere beyond the horizon, the first signal begins moving through a rescue system the crew cannot see.
How an EPIRB Starts the Rescue Chain
The EPIRB is the equipment that announces the emergency beyond normal line-of-sight radio range.
A 406 MHz Emergency Position Indicating Radio Beacon transmits a digitally coded distress signal for detection through the Cospas-Sarsat search-and-rescue satellite system . The transmitted beacon identity allows the alert to be associated with registration information held for the beacon.
Modern EPIRBs normally include a navigation receiver so that position information can be incorporated into the distress transmission. Rescue authorities can then combine the beacon message, location information and registration record when assessing and coordinating the response.
1. The beacon is activated
Activation may be manual, or a correctly installed float-free EPIRB may be released by its bracket if the vessel sinks.
2. The distress transmission begins
The coded 406 MHz signal identifies the beacon and may include position information obtained by the beacon.
3. The alert reaches the rescue system
Satellite and ground infrastructure distributes the alert toward the appropriate rescue coordination process.
4. Registration adds essential context
Correct registration can provide vessel details and emergency contacts that help authorities assess the alert.
Marine engineer’s note
An EPIRB should be mounted and maintained as an emergency system, not treated as general bridge equipment. A float-free installation needs a clear release path. A manual-bracket beacon needs to be immediately accessible during abandonment.
Do not confuse alerting with final homing
An EPIRB begins the long-range distress-alerting process. Search-and- rescue locating devices and survival craft radios support different parts of the operation after the alert has been raised.
For the historical development of beacon technology, see the history of the EPIRB . For the wider regulatory communications framework, read what GMDSS is and how it works .
Standard EPIRB vs AIS EPIRB
Both types raise the satellite distress alert. The AIS-equipped EPIRB also transmits an AIS locating signal for compatible nearby receivers.
The key comparison is not “GPS EPIRB versus AIS EPIRB”. An AIS EPIRB can also contain a navigation receiver. The important distinction is whether the beacon additionally transmits an AIS signal that can be displayed by compatible AIS equipment in the local area.
Standard EPIRB
- Raises a 406 MHz distress alert through Cospas-Sarsat.
- Transmits the programmed beacon identity.
- May include position information from an internal navigation receiver.
- Supports the long-range search-and-rescue alerting process.
AIS EPIRB
- Performs the core 406 MHz EPIRB distress-alerting role.
- Adds an AIS locating signal for compatible nearby receivers.
- Can improve local situational awareness during the rescue.
- Does not replace the need for correct registration and installation.
Why the AIS transmission matters
A rescue unit or nearby vessel equipped with compatible AIS equipment may receive the locating transmission and display it within the local navigation picture. That additional path can be valuable during the final stages of a rescue, particularly where several vessels or rescue assets are converging on the incident area.
AIS performance still depends on the radio environment, antenna height, receiver installation and local conditions. Explore the wider system in What Is AIS and How Does It Work on a Boat?
System integration point
The benefit of an AIS-equipped emergency beacon is strongest when the vessel’s own AIS installation—and the AIS equipment used by responding vessels—is correctly installed and functioning. Poor antenna location or RF faults can limit practical AIS performance.
AIS-SART: Making the Survival Craft Visible
The AIS-SART is a locating device. It is not the equipment that sends the original distress alert through Cospas-Sarsat.
The EPIRB alert has already started the response. The survivors now need to be found inside a dark, moving search area. The AIS-SART is activated and raised into the best practical position above the survival craft.
An AIS Search and Rescue Transmitter sends AIS messages that identify the unit as a search-and-rescue target and include its position. Compatible AIS receivers on nearby vessels or rescue units may then present that target to the operator.
Critical technical distinction
An AIS-SART does not send a 406 MHz satellite distress alert. Its role is to support locating after the emergency has already been raised by other means, such as an EPIRB or GMDSS distress communication.
What it does
Transmits search-and-rescue AIS messages containing the unit’s identity and position for reception by compatible AIS stations.
What affects it
Practical range is influenced by antenna height, the surrounding structure, receiver antenna installation and normal VHF propagation conditions.
For a deeper explanation of AIS display behaviour and vessel classes, read AIS Class A vs Class B . Installation-related reading includes marine AIS and VHF antenna placement , where to mount an AIS antenna and why AIS range may be poor .
Radar SART: Turning a Radar Sweep into a Trail
A radar SART waits for an X-band radar transmission and responds so that the search unit receives a recognisable indication on its radar display.
Unlike an EPIRB, a radar Search and Rescue Transponder is not a satellite distress beacon. Unlike an AIS-SART, it does not rely on an AIS target display. It is designed to respond when interrogated by compatible X-band radar.
Position above the survival craft matters
A radar SART should be deployed according to its instructions and raised as effectively as the survival craft arrangement permits. Obstruction and low mounting height can reduce practical detection performance.
The searching vessel also depends on a correctly functioning radar installation. Interference, poor tuning or installation faults can make a difficult search harder. See Marine Radar Interference Explained .
GMDSS Handheld Radio Communications
Once rescue units are within VHF range, the survival craft radio can turn a search target into a crew that can answer questions and follow instructions.
A light appears beyond the rain. The survivors can hear a vessel but cannot yet identify it. The handheld radio breaks the silence: “Survival craft in position reported by AIS-SART, this is rescue unit approaching from the south.”
A GMDSS survival craft VHF radio supports direct communication between survivors, rescue craft and nearby ships. It can be used to confirm the survival craft’s condition, describe injuries, coordinate approach and relay instructions during recovery.
Why voice communication still matters
Position alone cannot explain whether the liferaft is damaged, whether a casualty requires urgent medical attention, whether another survival craft is missing or from which side a rescue vessel should approach. That operational detail is where a suitable handheld radio becomes critical.
Learn more in Marine VHF Radio Systems Explained and What Is DSC on a Marine VHF Radio?
Battery and readiness
Survival craft radios must be stored, inspected and managed in accordance with their approved arrangements and the vessel’s applicable requirements. Emergency equipment should not be casually borrowed for routine deck communication.
Where the Personal Locator Beacon Fits
A PLB is attached to an individual. An EPIRB is associated with the vessel’s maritime distress arrangement. That distinction should remain clear.
A 406 MHz Personal Locator Beacon can raise a distress alert through the Cospas-Sarsat system when manually activated. For crew exposed to a risk of separation from the vessel—such as lone workers, delivery crews, offshore sailors or personnel working on deck—a PLB can add an important personal layer of protection.
EPIRB
- Associated with the vessel.
- Available in float-free and manual-bracket arrangements.
- Designed for maritime distress alerting.
- Forms part of the vessel’s emergency communications provision.
PLB
- Carried by an individual.
- Normally manually activated.
- Useful where a person could become separated from the vessel.
- Should not automatically be treated as a substitute for a required EPIRB.
A PLB is not automatically an EPIRB replacement
The correct equipment depends on vessel type, operation, flag, area of service and applicable carriage requirements. Personal equipment may strengthen the safety arrangement without replacing vessel equipment that is required or operationally appropriate.
SOLAS Survival Craft Communications
On vessels subject to SOLAS and related flag requirements, emergency communications equipment is selected and carried according to the vessel’s applicable category and arrangement—not from a universal one-size-fits-all list.
EPIRB
Raises the long-range 406 MHz distress alert and provides the beacon identity, with position information where incorporated.
AIS-SART
Transmits search-and-rescue AIS messages to compatible nearby AIS equipment.
Radar SART
Responds to interrogation by compatible X-band radar and supports final locating.
GMDSS VHF Radio
Enables direct communication with rescue units and nearby vessels when within usable VHF range.
Confirm the vessel-specific requirement
Carriage rules vary. Vessel size, construction date, trading area, passenger or cargo status, flag requirements and approved safety arrangements can all affect the required equipment and quantities. Obtain vessel-specific regulatory or survey advice where required.
The International Maritime Organization’s SOLAS information provides the wider convention context. F&C Marine’s GMDSS guide explains how distress alerting and maritime safety communications fit together.
UK EPIRB and PLB Registration
The beacon can transmit its identity, but registration explains who and what may be behind that identity.
Register through the UK Beacon Registry
UK-coded 406 MHz EPIRBs and maritime PLBs should be registered using the official UK Beacon Registry service . Registration should also be updated when ownership, vessel details, emergency contacts or relevant equipment information changes.
The beacon’s programmed identity and the information in the registry must refer to the correct vessel or user. A beacon transferred from another vessel should not simply be mounted and forgotten.
Check the beacon identity
Confirm that the beacon is correctly programmed for its intended vessel, user and national requirements.
Create or update the registration
Enter accurate owner, vessel and emergency-contact information in the official registry.
Update changes promptly
Ownership transfers, contact changes and vessel changes should be reflected in the registration record.
Keep records with the vessel documentation
Maintain suitable evidence of programming, registration, service and battery-expiry status.
Registration does not repair incorrect programming
Registration and beacon programming are linked but separate matters. Where the programmed identity is wrong, the beacon may require authorised reprogramming or service rather than only an online registry update.
Vessel identity also connects with wider maritime radio administration. See What Is an MMSI Number? and What Is a Maritime Radio Licence?
Selecting Marine Emergency Beacons and Survival Equipment
Start with the required safety function, vessel arrangement and operating profile. The product comes after the system decision.
| Operational need | Equipment type | Important selection question |
|---|---|---|
| Long-range vessel distress alert | 406 MHz EPIRB | Is float-free release required or is a manual-bracket arrangement appropriate for the vessel? |
| Local AIS locating capability | AIS EPIRB or AIS-SART | Is AIS functionality required as part of the beacon or as a separate survival craft locating device? |
| Radar-based final locating | Radar SART | What carriage arrangement and approved survival craft stowage apply to the vessel? |
| Personal distress alert | 406 MHz PLB | Could the individual become separated from the vessel, and how will the PLB be carried and activated? |
| Survival craft voice communications | GMDSS handheld VHF radio | What approval, battery and carriage requirements apply to the vessel? |
Jotron Tron 60AIS with Float-Free Bracket
An AIS-equipped EPIRB option for installations requiring a float-free bracket arrangement. Final suitability should be checked against the vessel’s required approval, coding and installation arrangement.
View Tron 60AIS Float-FreeJotron Tron 60AIS with Manual Bracket
An AIS-equipped EPIRB supplied for a manual-bracket arrangement where that configuration is appropriate to the vessel and required safety provision.
View Tron 60AIS ManualJotron Tron AIS-SART
A dedicated AIS search-and-rescue locating transmitter for reception by compatible AIS stations during the local search phase.
View Tron AIS-SARTJotron Tron SA20 PLB
A personal locator beacon option for users who require an individual 406 MHz distress-alerting device. Confirm coding, registration and operational suitability before deployment.
View Tron SA20 PLBJotron Tron TR30 GMDSS VHF Radio Package
A GMDSS handheld VHF package for approved emergency and survival craft communications applications, subject to the vessel’s applicable carriage requirements.
View Tron TR30 PackageJotron TR-8000 AIS Class A
A commercial AIS Class A system relevant to the wider vessel AIS installation. Product suitability depends on vessel category, interface requirements and the approved bridge arrangement.
View TR-8000 AISApproval and coding must match the application
Before ordering, confirm the required product approval, bracket type, beacon coding, registration jurisdiction, vessel identity and any statutory carriage requirements. Do not select emergency equipment solely from a photograph or general product title.
Installation, Inspection and Maintenance
Emergency equipment is only useful when it can be released, activated, transmitted and operated under real casualty conditions.
Keep access clear
Do not obstruct float-free release paths, bury manual equipment behind stores or create an abandonment route that depends on finding tools.
Verify programming
Confirm that programmed identities, vessel details and registry records remain correct after equipment replacement or vessel transfer.
Track expiry dates
Monitor battery and hydrostatic-release expiry dates where applicable. Arrange authorised servicing before the equipment becomes overdue.
Use approved test procedures
Carry out only the manufacturer-approved self-test or inspection routine. Do not activate live distress modes for casual testing.
Check survival craft stowage
Confirm that SARTs and radios are retained in their intended location and can be transferred or deployed as the vessel’s procedure requires.
Train the crew
Crew should understand which device raises the alert, which device supports locating and which device is used for direct communication.
The bridge system matters too
Emergency communications depend on more than portable devices. Vessel AIS, radar, VHF, DSC, antennas, cabling, power arrangements and bridge procedures all contribute to the wider response.
For preventive work, see Bridge Radio System Maintenance , Common Marine AIS Installation Faults and AIS Antenna vs VHF Antenna .
Marine Emergency Beacons FAQ
What is the difference between an EPIRB and a PLB?
An EPIRB is associated with the vessel and is designed for maritime distress alerting. A PLB is carried by an individual and is normally manually activated. A PLB should not automatically be treated as a replacement for an EPIRB required or appropriate for the vessel.
Does an AIS-SART send a satellite distress alert?
No. An AIS-SART transmits search-and-rescue AIS messages for reception by compatible AIS equipment. It does not send the original 406 MHz distress alert through Cospas-Sarsat.
What radar detects a radar SART?
A radar SART is designed to respond to compatible X-band radar transmissions. The response creates a recognisable indication on the searching vessel’s radar display.
Is an AIS EPIRB still a 406 MHz EPIRB?
Yes. An AIS EPIRB retains the 406 MHz satellite distress-alerting function and adds an AIS locating transmission for compatible nearby receivers.
Should a UK EPIRB be registered?
UK-coded 406 MHz EPIRBs should be registered with the UK Beacon Registry. The record should be updated when ownership, vessel details or emergency-contact information changes.
Does registration activate an EPIRB?
No. Registration creates the information record associated with the beacon identity. It does not activate the beacon and does not replace correct programming, installation, inspection or servicing.
Should an emergency beacon be tested?
Follow only the manufacturer-approved self-test and inspection procedures. Do not initiate a live distress transmission as a routine test.
Which emergency beacon should I choose?
Selection depends on the vessel, flag, operating area, applicable carriage rules and the safety function required. Confirm whether the need is vessel distress alerting, personal distress alerting, AIS locating, radar locating or survival craft voice communication.
The Rescue Chain Is Only as Strong as Its Preparation
The crew in our scenario were not protected by one miraculous beacon. They were protected by a sequence: the EPIRB raised the alert, locating equipment helped rescue units close the distance, and the handheld radio allowed the survivors to communicate during recovery.
That sequence depends on correct equipment selection, installation, registration, servicing and crew familiarity. Marine emergency beacons should therefore be treated as an integrated communications system—not as isolated yellow or orange boxes purchased to complete a checklist.
F&C Marine supplies and supports professional marine communications, AIS, GMDSS and emergency beacon equipment for commercial and specialist vessel applications.
Authoritative Resources
- Cospas-Sarsat — international satellite-aided search-and-rescue system.
- UK Beacon Registry — official UK registration service for 406 MHz beacons.
- UK Government 406 MHz Beacon Guidance — registration and beacon information.
- International Maritime Organization — SOLAS — convention background and maritime safety framework.
- IMO Radio and Navigation Equipment Documents — relevant IMO documentation and performance standards.