Plain English Meaning

A small lever on the oxygen regulator that lets the system mix the right amount of cabin air with the oxygen based on how high you are flying. Flip it the other way and you get pure oxygen instead of a mix.

Full Definition

A control on a diluter-demand oxygen regulator that, when set to the automix or 'normal' position, allows the regulator to automatically blend cabin air with oxygen in proportions appropriate to the cabin altitude, delivering progressively more pure oxygen as altitude increases. When moved to the '100 percent oxygen' position, the lever shuts off the cabin-air dilution and the regulator delivers undiluted oxygen on demand.

Context Anchor

Seen on the oxygen regulator or oxygen control panel when using a diluter-demand oxygen system in higher-altitude operations.