from ATR FCOM part 1.07.20....
TEST/RESET pb: this permits a test of oxygen flow without removing the mask from the container. It is springloaded to the RESET position.
TEST: provided MAIN SUPPLY is selected ON, oxygen flows through to the mask. The blinker momentarily displays yellow cross and the flow is audible.
If the main supply is selected OFF you ain't gonna get any oxygen!
hope the above helps
aeroconejo
