3 levels of signal technology. A built-in 66-channel GPS receiver determines your position and transmits it via a 406MHz signal to satellites. Those satellites immediately relay your position to Search and Rescue agencies worldwide. A 121.5MHz homing signal and integrated LED strobe light guides them to your exact location. A built-in test mode ensures internal circuitry, battery power, GPS, and 406MHz signaling are all functional. The AquaLink broadcasts a unique signal that tells rescuers who you are. Only 2.3" x 5.8" x 1.45" with a weight of 9.2oz. and will float. Battery life is typically 35 hours @ -4°F, has a shelf life of 6 years from date of manufacture or 5 years from the date it's placed in service, and is a non-hazardous lithium design. No subscription or registration fees required.