Very powerful - chirps unfortunately occasionally

This charger I bought, because at common holidays squabbles in my circle of friends, or in the family for the few available outlets are the norm. I was also tired of multiple chargers for my phone, the lugging my wife and my tablet. This charger anchor invited smoothly on my Lumia 1020, my Windows Tablet, my power and my GoPro Bank. It heats up far less than the manufacturer chargers. Furthermore, the equipment load in Power mode.
The only negative is that if you charge only one device, you hear a chirping. Once at least one other device is connected, listen to the chirping. Since I do not charging my devices usually in the bedroom, I do not mind the chirping. Maybe just my anchor has this phenomenon. The function is not affected in any case.