It is quite difficult (almost impossible) to find a compatible bell in CH. Two answers (one here, one on another forum) I don't understand at all, because the products which seem to be used are only 12VAC bells. But both OP's think it's ok, e.g. the three-channel electric bell from Jung is 12VAC and then the similar product from Feller is also 12VAC. The DoorBellG4 itself needs between 16VAC and 24VAC. What am I doing wrong here?