Which button, A or M, represents the external air circulation in a car?

[StLilah]

The M button is the forced internal circulation button, while the A button is the automatic control button. Below are detailed explanations: When the A button is lit and the M button is off: The A button represents the automatic control of the car's internal and external air circulation. When the A button is lit, the air conditioning system will automatically determine whether to use internal or external circulation based on the outside air quality. When the M button is lit: When the M button is lit, regardless of whether the A button is on or off, the car's air conditioning system will operate in internal circulation mode. When both A and M buttons are off: Only when both the A and M buttons are off will the air conditioning system operate in external circulation mode. The main feature of external circulation is maintaining fresh air inside the car, primarily for ventilation purposes.