What is An Emergency Position Indicating Radio Beacon (EPIRB)?

Emergency Position Indicating Radio Beacon (EPIRB) is a device to alert search and rescue services (SAR) in case of an emergency out at sea. It is tracking equipment that transmits a signal on a specified band to locate a lifeboat, life raft, ship or people in distress.

They are installed on ships and other vessels after being registered with the national search and rescue forces to that boat. The registration allows confirmation of false alerts faster and quick rescue operations in case of emergencies.

An EPIRB is a SECONDARY means of DISTRESS alerting, which is to say that it comes later in the hierarchy of alerting SAR authorities in case of distress.

It is mandatory to carry one EPIRB on every ship and two EPIRBS for all Registered ships (and other types of vessels).

Types Of EPIRB

  1. COSPAS-SARSAT– EPIRBS under the COSPAS-SARSAT system work on the 406.025 MHz and 121.5 MHz bands and are applicable for all sea areas
  2. INMARSAT E– 1.6 GHz band is the one on which this EPIRB works. These are applicable for sea areas A1, A2 and A3.
  3. VHF CH 70– This works on the 156.525 MHz band and is applicable for sea area A1 only

How Does An EPIRB Work?

The device contains two radio transmitters, a 5-watt one and a 0.25-watt one, each operating at 406 MHz, the standard international frequency typically signalling distress, 406MHz.

The 5-watt radio transmitter is synchronised with a GOES weather satellite going around the earth in a geosynchronous orbit.

The COSPAS-SARSAT is an international satellite-based search and rescue system founded by the U.S., Russia, Canada and France to detect emergency radio beacons.

Due to the many advantages of 406 MHz beacons and the disadvantages of the 121.5 MHz beacons, the International Cospas-Sarsat Program stopped the satellite processing of 121.5 MHz by satellites on February 1st, 2009. Encouragements were given by National Oceanic and Atmospheric Administration/ NOAA and FAA to switch to 406 for obvious reasons.

However, Emergency Locator Transmitter might still be used by aircraft, and alerts from these devices would not be acted upon unless confirmed by two other independent non-satellite sources or devices.


An EPIRB transmits signals to the satellite. The signal consists of an encrypted identification number (all in digital code) which holds information such as the ship’s identification, date of the event, the nature of distress, emergency contacts and the position.

A UIN is a Unique Identifier Number programmed into each beacon at the factory. The UIN number consists of 15 digit series of letters and numbers that make up the unique identity of the beacon. The UIN is on a white label on the exterior of the beacon. The UIN is also referred to as the Hex ID.

The Local User Terminal (satellite receiving units or ground stations) calculates the position of the casualty using Doppler Shift (which is the change in frequency or wavelength of a wave (or other periodic events) for an observer moving relative to its source).

The LUT passes the digital message to the MRCC (Mission Rescue Co-Ordination Centre). Furthermore, the MRCC is responsible for the SAR ops and oversees the execution of the rescue mission.


If the EPIRB is not compatible with a GPS receiver, the geosynchronous satellite orbiting the earth can pick only the radio signals emitted by the radio. The location of the transmitter or the identity of the owner cannot be deduced in this case.

These satellites can only pick up trace elements of such signals, and they can only give a rough idea of the location of the EPIRB. A signal of 406MHz is treated as an emergency signal per international standards.

The signal could help you locate the transmitter even if it is 3 miles away. The vessel or the individual in distress could be identified if the EPIRB is registered.

If an emitter transmits signals of 121.5 MHz, the rescuer or concerned party can reach the lost person even if they are at a distance of 15 miles. The accuracy of reaching the target could be magnified if an EPIRB also contains a GPS receiver.

Using an EPIRB

The EPIRB needs to be activated to emit signals by the beacon owner. This could be done by pushing a button on the unit, in the case of category II EPIRBs, or it could happen automatically if and when it comes in contact with water through hydrostatic release.

The latter is known as hydrostatic EPIRB; the quality makes it the best choice for sailors because it could be automatically activated in case the ship or vessel meets an accident and finds itself in deep waters.

The point to be kept in mind is that EPIRB needs activation to be operative, and this could happen only when it emerges from the bracket it is placed in. As said earlier, this could be done manually or happen automatically. The device is essentially battery-operated. This helps because power is the first entity to be affected in case of a calamity.


  • 12 Volt battery
  • 48 hours of transmitting capacity
  • Normally replaced every 2 to 5 years
  • Use proper replacement battery

False Alerting

The EPIRB might get activated by mistake by an individual onboard and send false alarms. If the EPIRB is falsely activated, the nearest coast station or RCC (Rescue Co-Ordination Center) must be informed immediately of this event and cancel it.

The cancellation intimation must also be sent to the appropriate authority (for example, DG Shipping for Indian Registered Ships or ships plying in Indian waters when the false alert is transmitted). The shipowner and/or the agent must also be informed.

Emergency Position Indicating Radio Beacon

Testing EPIRB

The EPIRB should be tested once a month to ensure operational integrity. The procedure to do so is as follows:

  1. Press and release the test button on the EPIRB
  2. The red lamp on the EPIRB should flash once
  3. Within 30 seconds of pressing the button, the strobe, as well as the red light, should flash several times
  4. After 60 seconds of operation, the EPIRB will switch off

Maintenance of EPIRB

  1. The EPIRB must be inspected visually for any defects such as cracks
  2. It is advisable to clean the EPIRB once in a while with a dry cloth
  3. While cleaning, the switches must be specifically checked
  4. The lanyard of the EPIRB must be neatly packed into the container of the EPIRB without any loose ends dangling about
  5. The expiry date of the battery must be checked to cover the immediate as well as the next voyage at the least
  6. Send the EPIRB back to the service agent or the supplier if the EPIRB fails the monthly checks
  7. Change the battery onboard if the facilities are available or send it to the servicing agent if there isn’t
  8. If the EPIRB has been used in an emergency, it must be returned to an authorised service agent for a battery change.
  9. If the HRU has crossed its expiry date, the HRU ought to be replaced on board, and HRU must be marked with an expiry date two years into the future.

PLBs (Personal Locator Beacons)

PLBs are EPIRBs but for individual entities. These indicate distress for an individual not in the proximity of emergency services. PLBs work like EPIRBS and transmit on the COSPAS SARSAT satellite system at 406.025 MHz. PLBs are much smaller in size as compared to an EPIRB. They work all across the world, at sea and on land.

They should be kept in a safe place on the vessel, in a ditch bag or in an easily accessible spot. Some have strobe lights and can be manually or automatically activated.

Once activated, PLBs transmit for a minimum of 24 hours, while the battery life on an EPIRB is at least double (a minimum of 48 hours). An EPIRB is registered to a vessel, whereas a PLB is registered to an individual.

The EPIRB is one of THE MOST important emergency pieces of equipment available onboard in the case of distress. Their care, testing and maintenance must be given considerable time to function at their optimum level when the situation arises.

Frequently Asked Questions

1. What are EPIRBs?

Emergency Position Indicating Radio Beacon is a device used to alert search and rescue forces in case of an emergency at sea. It tracks the position of the vessel, raft, lifeboat or ship through the distress signal sent.

2. What is the difference between an EPIRB and a PLB?

A significant difference between the two is that EPIRBs are registered to a vessel, whereas PLBs are designed for individual use. The former is mounted on the ship, whereas the latter is worn on a personal flotation device, kept in a pocket or bag so that they are accessible during an emergency.

3. There are how many types of EPIRBs?

There are generally two kinds of EPIRBs, Category I and Category II. Category I EPIRBs can be activated either manually or automatically, while Category II EPIRBs can be activated only manually. However, both devices transmit a 406MHz frequency.

4. How much does an EPIRB cost?

EPIRBs cost about 200 dollars at least. The price varies depending on the brand, features and other specifications. One should research properly before buying an EPIRB to meet one’s needs. EPIRB can be registered for free.

5. How long does an EPIRB last?

Beacon batteries have a lifespan of 5 to 10 years. It is advisable to change the batteries before their expiry date so that the EPIRB works appropriately in an emergency.

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Disclaimer: The author’s views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used in the article, have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 

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About Author

Shilavadra Bhattacharjee is a shipbroker with a background in commercial operations after having sailed onboard as a Third Officer. His interests primarily lie in the energy sector, books and travelling.

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  1. Note the Inmarsat 1.6 GHz EPIRB has ceased operation since 1 Dec 2006 (though it’s still referred to in the SOLAS convention).

  2. I am a public school teacher in senior high school maritime tract. we do not have available resources for maritime articles. Your site really help us a lot to equip our maritime students to be a future marine officers. we are very thankful for everything you’ve dine for your aspirants like us. Thank you and more power on your group.

  3. I work at an RCC and the information is overall good but not completely accurate. VHF-DSC is not an EPIRB not is INMARSAT. EPIRBs are also not a secondary distress.

  4. 1. There comes a special type of EPIRB called VHF-DSC EPIRB. This is used by vessels trading exclusively within A1 areas to carry an EPIRB operating on VHF channel 70 in lieu of a 406 MHz EPIRB.

    However, this is a type of EPIRB that is seldom used.

    2. Regarding EPIRB as secondary means of alerting, it is said so because usually the initial distress alerts are sent through the terrestrial (VHF, MF, HF) or Satellite (INMARSAT) system. Yes, EPIRB is also equally important in emergencies but we have written it as secondary for the sake of distinction as it works on a different system alltogether.

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