emergency locator beacon/transmitter

emergency locator beacon/transmitter (ELT)

A generic term for all radio beacons used for emergency locating purposes. These may be personal locator beacons or crash locator beacons. These beacons may be automatically activated by impact or water immersion and transmit a code on emergency frequencies (121.5, 243, or 406 MHz), enabling SAR (search and rescue) satellites or search units equipped with a direction finder (DF) to locate the crash or ditching site. ELTs aid in locating downed aircraft or personnel by radiating a sweeping audio tone two to four times per second. Sometimes called ADELT, automatically deployable ELT, or ELB, emergency locator beacon. Some of these transmitters are activated manually. Automatic fixed ELTs [ELT (AF)] are permanently attached to aircraft. Automatic portable ELTs [ELT (AP)] are rigidly attached to aircraft but can be readily removed after a crash. They can also be manually deployed. Survival ELTs [ELT (S)] are removable from an aircraft; they are stowed so as to facilitate their ready use by survivors.