What Is An EPIRB?

The full name of EPIRB is Emergency Position Indicating Radio Beacon, and it performs a vital role in keeping mariners safe.

As the name implies, EPIRBs are used in an emergency as a location finder for the rescue services to find the survivors of sailors in an emergency.

At a Glance:
1️⃣ The system is deployed in sea-going vessels (EPIRB) and aircraft (EL).

2️⃣ All owners of the units must register the devices, which preloads them with all the owner’s details. The registration includes important details about the owner, as well as the aircraft or vessel, and may assist the rescuers in identifying the position.

3️⃣ This enables the SAR authority to contact the next of kin and inform them about the situation, enabling the SAR organization to ask questions and get more information to help with the rescue.

📡 The Definition Of An ERIB

There are two categories of EPIRBs:

  • Category I – these can be activated automatically or manually and transmits on 406MHz frequency.
  • Category II – these can only be activated manually, and they also transmit on a frequency of 406MHz.

Before 2007 EPIRBs transmitted the distress signal at 121.5 and 243 MHz. Effective January 2007, all EPIRB were required to transmit on 406MHz, which became the only frequency that International COSPAS-SARSAT Satellite System would detect.

The rule did not affect man overboard systems that operated with a main base station and not through a satellite constellation.

Is The EPIRB System Effective?

The first generation of EPIRBs was developed by the US Navy in the 1950s. Since their introduction, they have significantly impacted the prospects of sailors’ survival by being rescued in time.

In 2021 EPIRB enabled 300 rescues, of which 195 were at sea. Between 1982 and 2021, the system enabled the rescue of 48,000 people globally.

During 2022 in America alone, the following number of rescues were undertaken:

  • Sea rescues: more than 270 people in more than 75 incidents.
  • Aviation rescues: More than 42 individuals in more than 28 emergencies.
  • Inland PLBs:  More than 75 individuals in more than 51 emergencies.

Which Countries Operate The EPIRB System?

The system is politically agnostic and irrespective of the relationships between countries, those who participate activate their SAR services irrespective of the nationality of the survivors.

The system was originally sponsored by Canada, France, Russia, and the United States. 

The 45 countries that participate in the service are listed here.

🚀 How EPIRBs Work

Category 2 EBIRPs are activated automatically when they come into contact with water (hydrostatic system) or if the activation button on the unit is pressed.

To learn more about this process, check out our article on how an EPIRB works. Once activated (manually or automatically), the following steps are followed:

1System transmits a 406MHz distress signal upon activation
2The signal is received by either a low earth orbiting (LEO) satellite or a COSPAS-SARSAT geostationary satellite
3The system transmits a 406MHz distress signal upon activation
4The signal carries the unit’s registration details for user identification
5COSPAS-SARSAT satellites orbit the Earth every 105 minutes, while LEO satellites do so every 100 minutes
6If the EPIRB has a GPS, its position is included in the signal
7Alerts are directed to an automated Mission Control Center (MCC) in one of the 38 countries operating a Local User Terminal (LUT)
8The LUT verifies and processes the signal
9Geosynchronous orbit satellites provide instant alerting, with location information if GPS data is included
10If a LEO satellite receives the message, the beacon location is computed by the LUT
11The signal is then forwarded to the nearest Rescue Coordination Center (RCC)
12In the US, the RCCs are operated by the US Airforce and the Coast Guard
13The rescue mission is activated and conducted following the rescue organization’s protocols

The Technology And Components Of An EPIRB 

Each component of the EPIRB system consists of the following parts:

The EPIRB Unit

The EPIRB Unit contains the following equipment:

  • One 5-watt radio transmitter (406 MHz, the standard international frequency, typically signaling distress)
  • One 0.25-watt transmitter (406 MHz)
  • A push button activation switch.
  • A Hydrostatic switch that is released when it comes into contact with water (Only Category I devices.)
  • A GPS Location device (Newer units)
  • A 12 Volt battery that should be replaced every 2 to 4 years.

Under normal operation, the 5-watt radio transmitter communicates and synchronizes with G.O.E.S weather satellites orbiting the Earth in a geosynchronous orbit.

The LEO (Low Earth Orbit Satellites) Constellation

The LEO Satellites are placed in a polar orbit around the Earth. Each satellite orbits the Earth every 100 minutes.

The LUT sites can use the LEO satellites to provide a location calculated by Doppler positioning.


COSPAS-SARSAT Satellites are in a geostationary orbit around each satellite passes over the same location every 105 minutes.

Although the COSPAS-SARSAT Satellites cannot provide a location using a Doppler, they can receive the GPS from the EPIRB Unit if it has a GPS on board.

If the EPIRB device is not fitted with a GPS, COSPAS-SARSAT Satellites cannot determine the position. The RCC can determine the location by knowing when the satellite received the signal.

When the LEO satellite also overflies the position, it enables the LUT to calculate a doppler determined position that can be cross-checked with the COSPAS-SARSAT Satellites.

The COSPAS-SARSAT satellite constellation is managed by three organizations:

  • National Oceanic and Atmospheric Administration (NOAA)
  • The United States Airforce (USAF)
  • The United States Coastguard.

NASA provides technical and problem-solving assistance.

Local User Terminals (LUT)

The Alerts are routed to one of the automated Mission Control Centers (MCC) in one of the 38 countries that operate a Local User Terminal (LUT).

The nearest LUT to the position where the EPIRB Unit was activated receives the redirected signal from the satellites.

The LUT authenticates and processes the signal and calculates the position of the signal by measuring the Doppler shift of the LEO satellites.

When the 406MHZ frequency is used, the LUT can calculate the transmitter’s position to 5 nautical miles.

The location data is then relayed to the nearest Rescue Coordination Center (RCC) in the country nearest to the transmitter’s location. 

The relevant country then activates the search and rescue actions according to local protocols.

Rescue Coordination Centers (RCC)

The TCCs are located in each participating country and are responsible for conducting search and rescue activities.

In America, they are managed by the following organizations:

  • United States Airforce regarding inland accidents (The Air Force RCC located at Langley AFB, Virginia.)
  • In most situations, inland search and rescue operations are conducted by the Civil Air Patrol (CAP) or local rescue services.
  • The coastguard in respect of maritime alerts.

🔄 Comparison With PLBs

The primary difference between EPIRBs and PLBs (Personal Locator Beacons) is that EPIRBs are assigned to a marine vessel, while PLBs are used as personal locators.

For more details on the differences, see our comparison of EPIRB vs PLB.

EPIRBs are generally mounted on the vessel, while the PLB will be attached to the individual’s lifejacket or personal flotation device (PFD.)

PLBs are not restricted to maritime situations and can be used when hiking, mountaineering, 4×4 driving, and any other remote activity. Learn more about what a personal locator beacon is.

While most countries require an EPIRB to be fitted to a vessel traveling more than 2nm off the coast, there is no requirement for PLBs to be carried.

PLBs are much smaller than EPIRBs because they are designed to be carried in the person, whereas EPIRBs are bigger and bulkier.

EPIRBs are legally required to be fully waterproof, whereas there is no such requirement for PLBs.

Once activated, PLBs will continue transmitting for 24 hours, whereas EPIRBs are required to continue transmitting for 48 hours.

Both systems generally transmit on 406 MHz. This is not a legal requirement for PLBs; some still transit on 121.5 and 243 MHz. The COSPAS-SARSAT satellite constellation cannot receive these signals and, therefore, will only be received by the LEO (Low Earth Orbit) satellites.

🛰️ EPIRBs And Satellites

EPIRBs are considered an alarm of last resort. Most emergency situations at sea are first communicated by a radio conversation or distress call.

If the EPIRB has been activated, it means that no radio communication is available, possibly because the system has been disabled by fire or sinking.

If they are activated, either manually or automatically, it normally means that the crew have become survivors of the emergency event and are in distress, possibly in a life raft or lifeboat.

The official terminology from NASA is that the system is activated when the person or vessel is in “situations of grave and imminent danger,” and lives are at risk.

When the system is activated, the following happens:

1️⃣ The EPIRB signal is received by one of the LEO satellites (In a polar orbit) and/or the COSPAS-SARSAT satellite (in a geostationary orbit.) These satellites are part of the various types of marine emergency beacons used in maritime safety.

2️⃣ The signal is automatically retransmitted to the registered rescue authority, one of forty-five nations, and two independent SAR organizations (that will be unique to the country in which they are located.)

3️⃣ The SAR organization coordinates the vessel’s search in a different location and will hand it over to a closer jurisdiction.

4️⃣ The system uses two methodologies to locate the transmitting unit (satellite Doppler position and Global Positioning Systems -GPS.)

5️⃣ With the introduction of GPS systems, much more accurate location data is available.

6️⃣ The SAR organization uses the system to accurately locate the survivors.

7️⃣ The local organization tasked with the rescue will enact its own protocols to effect their rescue.


Does EPIRB Have GPS? 

Newer models of EPIRB have GPS technology included. When properly registered devices, they enable the fastest and most accurate response to the transmitting EPIRB beacon.

When the device is registered, authorities can contact the next of kin in an average of 46 minutes. This means that accurate details of the vessel and passengers can be quickly given to the rescue centers making it easier to coordinate the SAR activities.

Who Monitors EPIRBs? 

The two satellite systems and the Local User Terminal (LUT) in 38 countries automatically monitor the system.

The signals are automatically processed and forwarded to Rescue Coordination Centers (RCC) in the closest country.

In the US, these are listed below.

  • United States Airforce regarding inland and aviation accidents (The Air Force RCC located at Langley AFB, Virginia.)
  • The coastguard in respect of maritime alerts.

Is An EPIRB Mandatory? 

SOLAS (Convention for Safety) requires all registered vessels to carry EPIRB devices.

In addition to this, many countries have their own enforcement requirements. In the US, by law, the following vessels are required to have EPIRB installed:

  • Commercial fishing vessels.
  • Passenger vessels that carry six or more people.
  • All other commercial vessels.

🔑 Key Takeaways

In many instances, EPIRBs are mandatory; however, even if they were not, they should be considered as important as a life jacket being carried on a boat. Another essential item for any boat is a ditch bag.

1️⃣ When the system is activated, rescuers can work out the signal’s location and respond quickly.

2️⃣ The system is becoming more advanced, and with the newer GPS-enabled units, the system can provide very accurate locations that substantially increase the chances of survival.

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.