How do EPIRBs and PLBs operate

Ocean Signal EPIRBs operate in the 406MHz satellite band monitored by Cospas-Sarsat, the international satellite organisation, ensuring a signal can be located wherever it is activated around the globe

On activation, the EPIRB commences transmission of a distress alert, which is picked up by two groups of satellites.

The geostationary (GEOSAR) CS satellitessatellites will typically receive the alert first, but these satellites do not have the ability to generate location information and do not cover the Polar Regions.

The second group of low earth orbiting (LEOSAR) satellites give complete global coverage, including the Polar Regions. As each satellite passes over an active EPIRB, it can calculate the approximate location (typically within 5Nm) of the beacon, using Doppler processing of the signal.

The satellites pass the received alerts to Cospas-Sarsat headquarters, where it is then passed to the relevant National Rescue Coordination Centre.

EPIRB without GPS: The SafeSea E100 EPIRB will have initiated a rescue attempt almost immediately after activation, but because of the nature of the satellite location process your position may not be known for some time afterwards as it depends on the orbit of the LEOSAR satellites which can take up to an hour to come into view..

EPIRB with GPS: The SafeSea E100G EPIRB will transmit its known location as soon as a position fix has been obtained by the built-in GPS, These transmissions will be picked up by both types of satellite. This provides two significant advantages

  • Immediate location of the vessel in distress
  • Excellent positional accuracy of the distress