What it is:

• An EPIRB is a small, portable, battery-powered radio transmitter.
• It is designed to be used in emergencies to alert search and rescue (SAR) authorities that a vessel is in distress.
• When activated, it transmits a continuous radio signal on the internationally recognized 406 MHz distress frequency.
• Many modern EPIRBs also contain a GPS receiver, which allows them to transmit the precise location of the vessel in distress. They may also have a lower power 121.5 MHz homing signal to help rescue crews pinpoint the location once they are in the vicinity.
• EPIRBs are registered to a specific vessel, providing SAR authorities with vital information about the boat and its owners.

How it works:

1. Activation: An EPIRB can be activated manually or automatically. Some are designed to automatically activate when submerged in water due to a hydrostatic release mechanism.
2. Signal Transmission: Once activated, the EPIRB transmits a distress signal to the COSPAS-SARSAT satellite system. This is a global network of polar-orbiting and geostationary satellites dedicated to search and rescue.
3. Location Determination: Satellites detect the 406 MHz signal. If the EPIRB has GPS, the location is transmitted directly. Otherwise, the satellite system can often determine the approximate location using Doppler shift analysis.
4. Alerting Authorities: The satellite system relays the distress alert and location information to ground stations, which then forward it to the appropriate Rescue Coordination Center (RCC).
5. Search and Rescue Response: The RCC uses the information to initiate search and rescue efforts. The 121.5 MHz homing signal (if present) helps rescue aircraft or vessels to locate the distressed vessel once they are in the general area.

Key uses and benefits:

• Alerting SAR: The primary purpose is to quickly and reliably alert search and rescue authorities in the event of a life-threatening maritime emergency, such as sinking, fire, or a serious medical situation.
• Providing Location: EPIRBs with GPS provide highly accurate location information, significantly speeding up the rescue process. Even without GPS, the satellite system can provide a much more accurate location than older signaling methods.
• Global Coverage: The COSPAS-SARSAT system provides worldwide coverage, so an EPIRB can be effective no matter where a vessel is located.
• Reliability: Satellite technology is generally very reliable, even in areas where other forms of communication (like cell phones) may not work.
• Mandatory Equipment: In many countries, it is mandatory for certain types of commercial and recreational vessels to carry a registered EPIRB, especially when operating offshore.
• Increased Chance of Survival: By quickly alerting rescuers to your location, an EPIRB significantly increases the chances of a timely rescue and survival in a maritime emergency.