The unknown port should be the lighting switch for the "master room" in the other word once you enter the master room you have to close the door in order to switch on the light.
ps. 仲有你地估下陪電視既power cord夠唔夠長拉上天花再過門檻啦?買電視時真係度清楚啦.... (雖然電線可以駁長...) 恆昌可能係件傢俬頂部開窿 俾你走線 但相信呇a唔會細心到幫你度埋你電視機既電線長度lor.....