The 406 MHz satellite EPIRB is a small battery-powered transmitting device designed to provide rapid alerting, identification and accurate location information to search and rescue crews. As the name implies, it is used only in case of emergency and usually only as a last resort when your marine radio is inoperable or out of range.
There are several types of EPIRBs. If disaster strikes, some float free and automatically activate – others must be activated manually. All EPIRBs float and will send out a continual signal for 48 hours. Since EPIRB signals are primarily detected by satellites that pass overhead, occasionally there may be a delay in detection (perhaps an hour) if there is no satellite currently in the area to pick up the signal. Once activated, the EPIRB should be left on to make sure the signal is available for detection by the satellite and for purposes of homing in on your location.