Final answer:
The ELT will automatically activate upon significant impact if the ELT ON/ARM switch is set to the ARM position. The ON position is for continuous operation, TEST for functionality checks, and RESET for turning off or resetting the unit.
Step-by-step explanation:
The Emergency Locator Transmitter (ELT) is designed to activate upon a significant impact, transmitting a distress signal to assist search and rescue operations. For the ELT to activate automatically upon impact, the ELT ON/ARM switch must be set to the ARM position. Setting the switch to ON would turn it on continuously, whereas the TEST mode is for testing the functionality of the unit, and the RESET position is typically used to reset the system or turn off an activated ELT.