[Digital (406 MHz) Beacons] A unique 15, 22, or 30 digit serial number called a Hex Code is transmitted The Hex Code can contain a plethora of information, such as:[27] the Country of beacon registration the identification of the vessel or aircraft in distress, and Identification for aircraft ELTs can be in the form of the aircraft's callsign or its ICAO 24-bit address (from its Mode-S transponder) optionally, position data from onboard navigation equipment (GPS) [Analog (121.5 MHz) Beacons] 
Anonymous siren tone