How an EPIRB Works.
An EPIRB or Emergency Position Indicating Radio Beacon, is a distress beacon used by mariners worldwide to alert Search and Rescue (SAR) forces that they are in distress. EPIRBs transmit a 406 MHz distress signal that contains a unique 15 digit identification number to the Cospas-Sarsat Satellite System (which is a government run system so there are no subscription fees). Search and Rescue forces then pull up your beacon registration (mandatory of all EPIRB owners) which tells them who the beacon belongs to as well as provides additional emergency contact information.
EPIRBs provide Search and Rescue forces with your location either via GPS data if your EPIRB is equipped with a GPS receiver, or via triangulation from the low earth orbiting satellites. This positional data is provided to the Rescue Coordination Center closest to your location. They in turn embark on your rescue mission and use the EPIRBs 121.5 MHz homing signal to ultimately pin-point your location and bring you home safety.
You are required to register your EPIRB with your local authority. If you purchase a new or used 406 MHz beacon, you MUST register it with your local government. If you change any information on your registration (such as phone number, address, bought a new boat, etc.) you MUST update the 406 MHz beacon registration. Also, if you sell your 406 MHz beacon, notify your local government that you have done so, and make sure the buyer registers the beacon personally. Otherwise, you may be contacted by rescue authorities if it is activated! Please provide the new owner a link to our registration web page so he/she can register their beacon. Visit ACR's Registration Data for more information about your country's registration requirements.
(Sourse:Sea Tow Monthly Newsletter)