An EPIRB serves as an alarm for SAR stations in case of accidents at sea or in the air. In order to do this, the EPIRB first determines its own position after an alarm and then transmits the distress call via one or several satellites.

In case of an accident the EPIRB automatically transmits the following data via the satellites to the base stations: the vehicle's call sign, type of accident, its last position with actual time as well as the direction in which it is moving and its velocity. An elaborate CRC defect protection guarantees transmission and decoding even in case of disturbances on the transmission path. Tests have shown that all base stations can receive the signals even with only 100 mW transmission power (1/10^th of the nominal transmission power). .
 

The picture shows the signal paths after an emergency.

Firstly the emergency transmitter determines its own position with the help of the GPS satellite navigation system. This is performed by a built-in GPS receiver. The determination of the position can also be guaranteed by connecting the EPIRB to the vehicle's own navigation system.

After the stipulated waiting period of two to eight minutes the EPIRB starts to transmit the distress call via one or several Inmarsat satellites. During this waiting period an audio signal is emitted to give the user one last chance to de-activate the unit. This is to reduce the possibility of false alarms.

The EPIRB mostly comes as a floating buoy. In case of an accident it automatically ejects from its cradle, surfaces and transmits a distress signal. The navtec EPIRB can also be activated by remote control from a ship's bridge. Furthermore, it can be taken along as a separate unit and activated manually.

If the EPIRB is installed in a cradle on board a ship, the distress call can also be transmitted via a remote control unit. The remote control unit makes it possible to state the type of accident. Compared to the simple ELT's (including locating by polar-circumnavigating satellites), EPIRBS provide the user with a much higher rate of security. This is caused by a more exact way of locating on one hand and an improved satellite availability on the other.

First of all, EPIRB's are intended for use and safety on ships, which are required to carry such equipment . The portable and easy-to-carry navtec system has also made it possible to use EPIRBs on sailing yachts and in aircraft.

Take a look at a  comparison of ELT and EPIRB systems on our web pages and what to do in case of false alarms.

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