Honda Odyssey Service Manual: Automatic Dimming Inside Mirror System Description

The automatic dimming inside mirror has a front-facing lux level sensor (A), rear-facing lux level sensor (B), and a control unit. The control unit receives signals from each sensor. Based on the difference between the two lux levels (the light outside the vehicle and the light from the headlights of the other vehicle, etc.), the control unit controls the electro-chromic gel to reduce glare. This dimming function is canceled when the transmission is in reverse and the indicator (C) goes off.