Emergency Locator Transmitter. The ELT is a small radio transmitter that is installed in an aircraft and is designed to being transmitting upon impact (the crash) or it can be manually switched on. The ELT transmits a distincive signal on the international emergency frequencies of 121.5 MHz (VHF) and 243.0 MHz (UHF). This signal is picked up by ground stations, search and resuce aircraft (see Civil Air Patrol and Coast Guard, and satelites. Direction-finding equipment is then used to "home-in" on the signal and locate the downed aircraft.
by IrishRepublicanArmy January 18, 2004