Bakengids: Hoe werken EPIRB's?


An EPIRB (Emergency Position Indicating Radio Beacon) is a vital safety device for alerting search and rescue services and ensuring the protection of human life at sea. In an emergency on the water, the distress signal from a marine radio beacon tells the coast guard you need help and enables your boat and people overboard to be located and rescued as quickly as possible. There is no device more reliable that will increase a person's chances of survival in an emergency at sea than a radio beacon.

In this guide, SVB explains the most important functions of this life-saving equipment, especially EPIRBs, and compares them with other beacons. We provide help and assistance in choosing the right EPIRB from the wide range of devices available. Read on and find out more about the features, differences, and benefits of marine radio beacons.

What is an EPIRB?

Wherever your boat is, when an EPIRB marine beacon transmits an alert, it sends a locating distress signal to more than 200 countries around the world. The signal sent by the beacon contains a unique identification number that is assigned to the vessel and enables the boat or person to be located and rescued. The global distress signal ensures the fastest possible rescue in case of distress at sea. When a beacon is deployed, the radio transmitter sends out a signal.

The origins of emergency beacons started in commercial shipping and air traffic. Depending on the intended use of your transmitter, they can be differentiated according to transmission frequency, power, and purpose. There are two main common types of emergency locator beacon, aka radio beacon, to transmit position and immediate distress signals in dangerous emergency situations. These are EPIRBs for boats, and the portable PLB marine beacons (Personal Locator Beacons) for people.

EPIRB emergency radio beacons are specially designed for marine use and should be mounted in the outer deck area so that they are easily accessible and ready for use at all times. In an emergency, an EPIRB can be activated manually or automatically on contact with water. Once activated, the unit sends out both a digital and analogue locating signal for long-range localisation. An EPIRB must only be activated in an emergency.

Eprib illustration graphic

What are the frequencies 121.5 MHz and 406 MHz used for in EPIRBs?

On 1 February 2009, the international rescue system for detecting and locating EPIRBs, COSPAS-SARSAT, was reprogrammed to detect only 406 MHz signals for positioning and alerting. Satellite detection and processing of 121.5/243 MHz beacons was thus ceased, which today can only be detected by analogue receivers and SAR-equipped rescue vehicles using “homers”.

It only takes a few minutes for the alarm from an EPIRB with GPS to reach the Maritime Rescue Coordination Center (MRCC). However, if conditions are poor, it can take up to 4 hours to activate a COSPAS-SARSAT beacon without GPS. As the respective LEOSAR system consists of several satellites that follow an orbit around the earth, the time it takes to receive a 406 MHz signal depends on one's own position.

Satellites can determine the position of an EPIRB-GPS fairly accurately. An EPIRB GPS module improves the accuracy of a COSPAS-SARSAT maritime emergency radio beacon (EPIRB) from 5 km to 100 metres.

Consequently, on newer devices, this distress signal has been running since 2009 via the GMDSS, the Global Maritime Distress and Safety System, for international and worldwide coverage for emergencies at sea.

When a modern EPIRB is activated, it usually sends out a dual signal: a digital satellite signal transmitted on 406 MHz frequency containing the vessel's identification and coordinates if equipped with GPS. An additional search signal is transmitted at low power on 121.5 MHz. This homing signal also allows coast guards and rescue vehicles such as SAR vessels, aircraft, or helicopters to locate the exact position of the emergency. Older devices that are not compliant with GMDSS operate exclusively via radio on the 121.5 MHz homing frequency (close range). The short-range frequency is used, for example, by the German Sea Rescue Society and by helicopters.

Certain EPIRBs can be deployed either on water contact or manually. Wherever a vessel is in the world, the distress signal is quickly sent out to initiate Search and Rescue (SAR) within minutes of it being sent.

The satellite signal is primarily used to alert organisations and define the scope of the sea area where search operations are to be concentrated. The analogue signal has a limited range and is used by rescue teams that have been dispatched to locate the exact position of the incident with greater precision.

In the past, using a dual signal would compensate for each signal's weakness, today most devices have GPS that allows them to locate the distressed craft immediately and accurately.

In Mediterranean and coastal areas, response is expected to arrive within 24 hours of the distress signal being sent. In more remote marine areas, rescue crews should arrive within 72 hours.

Until today, more than 30,000 rescues are thought to have been carried out worldwide with this system, which is why the device is becoming increasingly more popular today.

What is inside an EPIRB?

Epirb Box

The key components of an EPIRB are an antenna and manual or additional automatic switch. Note that most common EPIRB units do not have a housing to protect from splash water or rain on deck, but only have a bracket for mounting. These devices should therefore not be mounted outside, as they could be triggered accidentally. “Float-free” EPIRBs are fitted in a float-free bracket and use a hydrostatic release function and a water activated switch.

Epirb in the Box

They can be mounted outside on the deck. A powerful light also ensures that the scene of the accident and the shipwrecked persons are visible from afar in the dark. A long-life, non-rechargeable, lithium battery is built in, which is designed for a transmission time of at least 48 hours in temperatures as low as -20 °C, plus a test button, which is used to check regularly for correct function. Many of today's units are also fitted with GPS for more precise localisation.

How does an EPIRB emergency beacon work?

There are basically two different modes of operation:

Category I: Units that can be activated either manually or automatically upon water contact.

Category II: Units that are only deployed manually can only be activated by a button.

Float Free Epirb

Not all automatic EPIRBs feature a “Float-free” mount. Automatic Satellite Emergency Transmitters are housed in a simple mounting bracket that does not protect the EPIRB from water contact. The bracket allows the unit to be easily mounted on a wall on the inside. You shouldn't mount such simpler EPIRBs outside on deck, as without a float free bracket these units are not waterproof and could result in a trigger failure. Use a float free EPIRB mount for outdoor use.

The new IMO resolution MSC 471 (101) requires automatic devices to be equipped with a GNSS system and an AIS transmitter from 1 July 2022, which will greatly simplify the location of shipwrecks. Manual devices are not affected by the requirements of the new MSC 471, nor are automatic EPIRBs installed before 01.07.2022.

SVB has a range of the latest products that are always up-to-date and comply with international guidelines, such as the MCMURDO SmartFind G8 AIS EPIRB marine beacon. Featuring AIS automatic identification system and GNSS, the unit meets all new requirements and combines the following features:

  1. International Emergency (COSPAS-SARSAT Rescue System) 406 MHz
  2. Analogue bearing frequency (detection frequency) 121.5 MHz
  3. The GNSS system for precise GPS coordinates with reception from 72 satellites (GPS, Galileo, GLONASS), reducing position error from 5 km to 100 m.
  4. Class A and B AIS transmitters to warn other vessels in the vicinity.

When a 406 MHz transmitter is activated and detected by the COSPAS-SARSAT system, one of the first steps taken by SAR authorities is to contact the owner of the transmitter or the emergency contact point provided by the owner to obtain confirmation of the emergency situation.

The COSPAS-SARSAT is a satellite-based alarm system in the Global Maritime Distress and Safety System (GMDSS), which was established internationally in 1982 by the USA, Russia, Canada, and France. The 406 MHz signal received by the COSPAS-SARSAT satellites is transmitted to globally positioned ground stations, so-called LUTs, also called Local User Terminals, which in turn forward the data to the respective MRCC, the Maritime Rescue Coordination Centre. The data received is then transmitted to the closest appropriate SAR authority, which launches rescue assets such as air or sea rescue craft.

What does EPIRB stand for?

The following is an overview of all technical terms:

COSPAS Cosmicheskaya Sistyema Poiska Ava riynich Sudov (= Space System for the Search of Vessels in Distress), Polar-orbiting, low-flying satellites
EPIRB Emergency Position Indicating Radio Beacon (406 MHz or 1,6 GHz emergency beacon)
GMDSS Global Maritime Distress and Safety System, worldwide system for automated emergency signal communication for ships at sea
GEO Geosynchronous Equatorial Orbit, earth-orbiting satellites
LEO Low Earth Orbit, small and fast satellites for high-speed, low-latency communication
LUT Local User Terminal, ground station
MDI Maritime Identification Digits, three-digit marine radio station identifier
MMSI Maritime Mobile Service Identity, maritime telephone number sent in digital form over a radio frequency (VHF, KW & GW))
MRCC Maritime Rescue Coordination Centre
PLB Personal Locator Beacon (121.5 MHz transmitter worn on the body)
SAR Search and Rescue (rescue service)
SARSAT Search and Rescue Satellite, polar orbiting satellites
SART Search and Rescue Radar Transponder
SBM Shore Based Maintenance, regular maintenance of equipment on land
SOLAS Safety of Life at Sea, Treaty / rules on the minimum safety standards in the equipment of ships over 300 GT
IMO International Maritime Organisation, UN specialised agency for maritime safety and environmental protection

What information must be visible on an emergency satellite beacon (EPIRB)?

Emergency Information
  1. Vessel name/call sign/MMSI/Identifier/UIN-HEX (Unique Idenfication Number
  2. Serial number
  3. Battery expiry date
  4. Expiry date of the water pressure release (Only for EPIRBs with Float-Free bracket)

Once activated, the distress buoy emits a 5-watt signal every 50 seconds for at least 48 hours, which contains a unique serial number called a hexadecimal code. All important information is stored on this code, e.g., to alert the next of kin registered with the respective authority. Any important information that could be useful for the rescue forces is transmitted together with the data of the vessel or person, the port of origin and any additional information.

There are technical differences, certainly fewer than in the past, but the most notable is that the EPIRB is part of the GMDSS and requires the use of an MMSI (Maritime Mobile Service Identity) code that uniquely identifies the vessel. A PLB does not have an MMSI but a serial number given by the manufacturer which does not identify the vessel but only the person through a registration form and cannot be used instead of the EPIRB. It is essential to have as many sources of information as possible for a rescue. For US EPIRBs, it is also necessary to register on the COSPAS-SARSAT website with a form which also contains all the important information on the rescue at sea of the person and the boat.

What is the difference between EPIRB and PLB?

A Personal Locator Beacon is an excellent addition to your equipment, and not just because of its small, compact size. Such devices are handy, personal, and perfect for skippers, on charters, crossings, or activities such as hiking or other outdoor activities. There are no special legal obligations, only personal registration.

Like EPIRBs, PLBs with integrated GPS transmit digitally on 406 MHz, although they also operate on the low-power analogue frequency MHz 121,500 in homing mode. Also, like EPIRBs, PLBs must be registered. However, units do not activate automatically compared to many EPIRB units.

When should an EPIRB be tested?

To ensure reliable operation of an EPIRB, regular maintenance is essential but not mandatory in every country. Many EPIRB units have a self-test function to check that the unit is working properly before a long sea voyage. You should certainly consider a reputable brand when selecting a product, especially for blue water sailing, as well as worldwide maintenance and service points.

If a device is removed from its bracket prior to an EPIRB test, ensure that no false alarm can be triggered! When doing so, refer to the operating instructions for the device. The estimated life of the device and battery is 10 years or less. The built-in lithium batteries are not rechargeable and must be replaced. During this lifetime, regular maintenance must be carried out on your EPIRB. According to guidelines for Shore Based Maintenance (SBM), the battery or EPIRB device itself must be exchanged to ensure problem-free operation. Batteries must usually be replaced every 5 years, even if the expiry date has not expired. There exists no EPIRB device on the market where the battery change can be done by yourself. Check regularly whether the unit still functions according to the manufacturer's specifications. After all, once the batteries have been activated in an emergency, they must function without failure for at least 48 hours at temperatures as low as -20 °C. In addition, the hydrostatic release of automatic units must be replaced every 2 years. More detailed replacement times can be found on the respective model.

The 1974 SOLAS treaty, the International Convention for the Safety of Life at Sea, includes a regulation regarding maintenance of EPIRBs. In some countries, it is necessary to comply with the requirements of the SOLAS Convention for the maintenance of their EPIRBs at all times. In Italy, for example, these guidelines state that EPIRB units must be replaced every 4 years. This ensures that the latest, more technologically advanced equipment is always on board to keep passengers safe.

Maintenance Epirb

EPIRB devices with Float-Free fixture

What is EPIRB programming and EPIRB registration?

EPIRBs must be programmed and registered with the relevant regulatory authority in your country. Failure to comply with EPIRB registration may result in a fine. All 406 MHz EPIRBs must be programmed with a unique, country-specific identification number. Normally this is related to the country whose flag your boat is flying.

After purchase, the EPIRB must first be programmed with an MMSI (Maritime Mobile Service Identity), a globally unique number. When first programming marine beacons, a 15-digit alphanumeric hex ID code is assigned to the EPIRB and the vessel. In comparison, a PLB is assigned a number that is registered to a person.

Do you have an EPIRB and want to programme it with new settings? Reprogramming of the identification and registration parameters can be done by the same retailer where the EPIRB was purchased, by the manufacturer's national importer or by SVB for a reprogramming fee for EPIRBs. Please ask us about programming your existing EPIRB unit for you. Some devices are not eligible for our reprogramming service.

Please use the SVB Programming Data Sheet and our Initial Programming of Distress Transmitters. If you intend to have your newly purchased EPIRB programmed, this must be done with the order.

What is a Beacon ID for EPIRBs?

This number is a globally unique character string in the form of a 15-hexadecimal character string consisting of numbers and characters on the beacon and on the manufacturer-supplied label:


Beacon ID = MMSI-Code (MID + 6-digit code + international callsign)

The MMSI (Maritime Mobile Service Identity) code consists of 9 digits, the first three of which form the maritime identification number, the MID (Maritime Identification Digit), and indicates nationality.

To ensure that search and rescue authorities can retrieve all relevant information about you, your vessel and your emergency contacts in an emergency, you can voluntarily register your EPIRB via the COSPAS-SARSAT website. Once the unit has been programmed and registered, it is ready for use.

Providing your device with a unique digital identifier and registration details given by the boat owner are small bureaucratic hurdles to overcome to ensure your personal safety for an emergency that hopefully will never occur.

Eprib in use

Are EPIRBs mandatory?

PLBs are an alternative for vessels that are not required to be equipped and can never replace an EPIRB. In some countries, such as Germany, a portable emergency distress beacon (EPIRB) is a recommendation for additional maritime distress equipment on board a recreational craft. In other countries, however, carrying an EPIRB is compulsory, e.g., in Italy an EPIRB has been mandatory for navigation over 50 miles (approx. 80 km) since 2000. The same applies to chartered vessels sailing more than 12 nautical miles or carrying more than twelve passengers, commercial fishing vessels licensed for more than 6 nautical miles, vessels subject to the GMDSS, cargo vessels, passenger vessels, high-speed craft, yachts, and large fishing vessels. Be sure to check the applicable regulations if you plan to operate a boat in another country.

Which licence is required for an emergency radio beacon (EPIRB)?

You must register your EPIRB after programming it in order to use it on board. In most countries, it is mandatory to have a boat radio licence as a document on board. This avoids problems and fines if you are inspected by a local authority. Order an electronic MMSI radio licence for your boat in a few minutes using a form, you don't even have to take a course, just have some information about you and your boat ready. However, these permits are only issued for a maximum of 10 years. They also have the option of periodically limiting the permit each year upon application. Depending on the country, fees are payable for these permits.

Also note the SBM regulations applicable in other countries (Shore Based Maintenance). For example, every 4 years in Italy. In addition to replacing the lithium batteries, the waterproofness and signal strength are also checked and measured in a protected environment to avoid false alarms. It is also mandatory to replace the hydrostatic release every 2 years (for automatic models) and to carry out an annual test if it is a professional vessel.

In accordance with IMO resolution MSC 1040, each EPIRB must also be subject to an annual operational audit. Mandatory for commercial vessels carrying liquids containing benzene or liquefied carbon dioxide in bulk, but not required for recreational craft.

IMO resolutions are only issued in the field of GMDSS systems, to which ships and recreational craft do not apply.

Automatic EPIRBs must be mounted outdoors in an easily accessible location so that they can also be triggered manually and carried at all times.

First of all, a distinction must be made between manual, automatic and hydrostatic release.

Many modern EPIRBs are both types and can be activated depending on the circumstances. These distress beacons can either be activated manually or automatically when they are submerged in water.

What should you do in case of an EPIRB false alarm?

An accidental 406 MHz alarm causes costly disruption to search and rescue services or, in the worst case, can endanger lives. Intentional misuse of the beacon may result in a penalty and fine.

If for any reason an EPIRB is activated accidentally, the alarm can be switched off or cancelled. The transmission of the emergency signal does not mean the immediate dispatch of rescue vehicles, but the ship should contact the nearest coast station or an appropriate coast earth station or RCC and cancel the distress alert. When the EPIRB buoy is linked to the international call sign or MMSI, the actual need for a rescue is immediately verified by VHF contact or with a call to a mobile phone that was registered during the programming process.

In the event of an accidental activation, attempt to switch off the EPIRB device, immediately call the RCC or MRCC and inform the nearest port authority of the false alarm and the cause that triggered it.

The signal starts 90 seconds after activation to leave a margin for correction in case of an error. However, if in doubt, it is better to contact the Harbour Master's office as soon as possible!


What is the difference between EPIRB and SART?

A SART, Search and Rescue Radar Transponder, is a portable marine navigation device used on ships during the time of distress and has SOLAS approval. In the event of a man-overboard situation, a SART provides a higher chance of survival. If a SART detects radar waves from boats or ships within a radius of 20 miles (about 32 km) to 30 miles (about 48 km), it sends an identifiable signal back to them as a unique distress call. This signal is seen by the radar as strong and distinctive “echoes”.

SART only works when there is a vessel with active radar nearby or an aircraft or helicopter in the air. An AIS SART distress transmitter, on the other hand, allows a shipwreck to be located using an AIS signal, but is limited to a transmitting power of 1 watt and has a range of 5 miles (approx. 8 km). When a SART is activated, any boat with AIS is able to locate the live position of people and view it on a PC or plotter. A GPS, sound and light signal is sent out which informs all ships in the vicinity about survivors of a shipwreck.

EPIRBs and SARTs are both outdoor beacons used to indicate your position in an emergency when you need rescuing at sea, but they are different pieces of safety equipment. EPIRBs communicate directly with international search and rescue coordinators, and the distress signal from an EPIRB device is detected by them and confirmed. SARTs are detected by other vessels that are close enough to detect them on their radar.