An EPIRB is an Emergency Position Indicating Radio Beacon, which is used as a distress alerting system, indicating to SAR authorities both the identity and position of a person or a vessel, which is in grave and imminent danger and requires immediate assistance.

Simrad EG50 EPIRB

EPIRB Sample

Mandatory registration

Every EPIRB is pre-programmed with a unique identity before it reaches the customer. This is done by the manufacturer or, in some cases, the distributor. The identity includes a 3 digit country code. This is the country that takes responsibility for storing that particular EPIRB’s registration details. In most cases this is the country to which the vessel is flagged. The country programmed into your EPIRB can be found from its identity label where usually all the necessary markings are, except the vessel's name. Marking vessel's name is customers responsability. Customer must register his EPIRB with the appropriate authorities in that country. All he has to do is complete details of his vessel and provide contact numbers on pre-printed forms with his EPIRB’s identity. When he has completed the form, he can choose to fax it or mail it and wait for confirmation.

EPIRB identity label
EPIRB Identity Label sample

EPIRBs must not be transferred from vessel to vessel without informing the appropriate registration authority.

EPIRB components

The key components of an EPIRB are:

  • Antenna; it must be near vertical when operating (transmitting),
  • Sea switch; activates the EPIRB automatically when submerged in water,
  • Activation switch; enables to activate EPIRB manually,
  • Test button; enables the user to run test sequences to verify the readiness of the EPIRB,
  • Lanyard; the cord is used to tether the EPIRB to a life raft,
  • Strobe light; when the EPIRB is activated it will flash and give a visual aid to SAR unit,
  • LEDs and buzzer; are used to show which mode the EPIRB is in and to show the result of the EPIRB test sequences,
  • internal battery supply which lasts for at least 48 hours (transmitting),
  • GPS position fixing system in most but not all models; it enables SAR operation to start instantaneously.

EPIRBs may either be portable and capable of being manually activated or they must be able to be deployed automatically without any operator intervention.

Manualy activated EPIRBs

Manualy activated EPIRBs are suitable for leisure vessel installation, for example sail or small fishing boat. They are normally supplied with a bulkhead mounting bracket, but even they are dismounted,usualy they also have "carry safe" removable collar that deactivates EPIRBs sea switch so they cannot be activated by moisture.

EPIRB in carrysafe collarEPIRBs removable collar

EPIRB in "carry safe" removable collar, arrow is showing the magnet on the removable collar that actually deacivates sea switch

Automatically activated EPIRBs

Automatically activated EPIRB must be used on SOLAS vessels, for example passenger cruise liner, container ship or oil tanker. They are supplied with a plastic enclosure in which the sea switch of the EPIRB is deactivated. The plastic enclosure contains a spring-loaded lever which automatically pushes the enclosure lid off and releases the EPIRB if the vessel sinks. This automatic ejection is controlled by a device called a HRU (Hydrostatic Release Unit) that will automatically release the EPIRB once a depth of approximately 4-5 m is reached. At which time it will float free to the surface that enables it to be activated by the sea switch.


An example of a HRU mounted on the enclosure base (under the lever and HRU is well visible compressed spring)

EPRIB automatic release sequence

EPIRB automatic release sequence

What happens when an EPIRB is activated

When an EPIRB is activated in an emergency it begins to transmit radio signals that includes also its identity number. Radio signals are detected and processed by sattelites which relayes the message with the identity number and position to the nearest MRCC (Maritime Rescue Coordination Centre). MRCC will then decode the country code from the message. After that they will access the registration database for that country and expect to find details of the vessel to which the EPIRB belongs to, its radio equipment and who to contact. If they fail to find this information, this may slow down any rescue. Then, they will start with SAR operation. SAR vessel/helicopter/plane involved in SAR operation will try to find EPIRB based on it's radio signal with the direction finding equipment.

You can find detailed technical overview about what happens when an EPIRB is activated in the next chapter.

The EPIRB stowage

The bulkhead bracket of an manually activated EPIRB should ideally be sited in plain view near an emergency exit.

The enclosure of automatically activated EPIRB should ideally be sited in a clear location on a ship, for example on the wing of the bridge or on the “monkey island” above the bridge, because it is critical that you choose a position where the released EPIRB will not get trapped by overhangs, rigging, antennas and so forth, should the vessel ever sink.

When choosing a suitable mounting position you should also consider:
  • Ease of access in an emergency.
  • Mount at least 1 m from any compass equipment.
  • Mount at least 2 m from any radar antenna.
  • Avoid direct impact of waves.
  • Avoid positions with insufficient space for lid ejection and
The EPIRB is usually supplied with a self-adhesive instruction plate that should be mounted next to the EPIRB so that is easily visible in an emergency.
EPIRB instruction plate
An example of an instruction plate

IMO EPIRB Safety Sign label could be used to show the position of EPIRB.

IMO EPIRB Safety Sign

IMO EPIRB Safety Sign

The SOLAS convention requirements

SOLAS vessels must carry a COSPAS-SARSAT EPIRB operating on 406 MHz and 121.5 MHz. 406 MHz radio signals are used for locating purposes to detect the casualty (this is explained in details in the next chapter), while 121.5 MHz radio signals are used for homing purposes by SAR vessel/helicopter/plane involved in SAR operation which is trying to find EPIRB with the direction finding equipment.

In accordance with the efficiency requirements of the SOLAS convention, EPIRBs are equipped with a battery, with a capacity of working 48 hours (transmitting time).

Last modified: Saturday, 25 April 2020, 7:50 PM