ELT
Emergency Locator Transmitter. A device, which can either be portable or fixed in the aircraft that transmits a signal in the event of an emergency. Depending on the ELT, it may have to be manually turned on, or in most cases will be automatically turned on after some high impact. There is the possibility that a hard landing could activate an ELT. There are specific time periods to test an ELT on 121.5 MHz