If I unplug the charger cable, the display stops working and uses the UBMP display. If I plug it back in, it starts using dual displays. So I restart again and it uses the ACD. When the ACD charger is plugged into the UBMP, it emits a annoying high-pitched noise. When I remove it, the UBMP goes to SLEEP!!!!!! What the hell! And, when the UBMP goes to sleep/shutdown, the ACD emits ANOTHER high-pitched frequency AND a "frequency ticking". This is ridiculous. This has to be the worst quality control there is. I'm never recommending Apple again and I'm regretting my purchase of a UBMP because of this. What I can't stand is the damn frequency noise, it's so annoying. It's funny how review sites RARELY mention these problems and how recommendations given here doesn't mention them either.