From my handbook -
Switching between outside air and recirculated air modes
Press .
The mode switches among (recirculated air mode), automatic and
(outside air mode) modes each time the button is pressed.
When the system is switched to automatic mode, the air conditioning system operates
automatically.
The indicator above the selected button comes on.
Outside/recirculated air mode may automatically switch depending on the temperature
setting or the inside temperature
From the Lexus EU tech doc for my car
Also as posted above the light sensor on the dash top is dual function, providing the a/c amplifier control with light intensity info.