[Huadong]

Can anyone tell me what the function of the button inside the front roof? There are 4 buttons, two for lights, one for intrusion, the fourth? I check the manual book, and could not find the answer

 

[Karmalakas]

 

[Huadong]

I missed this page.., page 491! Thanks. I played the button several times, and could mot figure it out ☺😟. Now I know...