Plain English Meaning
A small emergency radio fitted to the aircraft. If the aircraft crashes, it switches itself on and sends out a signal so rescuers can find where the aircraft came down.
Full Definition
A self-contained, battery-powered radio transmitter installed in an aircraft that automatically activates on impact and broadcasts a distress signal on designated emergency frequencies (typically 121.5 MHz, 243.0 MHz, and 406 MHz) to help search and rescue services locate a downed aircraft.
Context Anchor
Pilots encounter ELTs during preflight checks, aircraft equipment inspections, emergency procedures, and search-and-rescue discussions.
Derivation
From 'emergency' (a sudden requiring action), '' (something that helps find a ), and '' (a device that sends out a radio signal). The name describes exactly what it does — sends a signal to help locate you in an emergency.