On the product page for the Doorbell Wired , in the Tech specs section, only the official Ring Plug-In Adapter 2nd Generation should be used for DC power. This refers to the power that would come out of a wall outlet. In the case of using a transformer, the following specs of 8-24 VAC, 40VA max, 50/60Hz should be met. You will not be able to use a DC transformer. If you wish to use a transformer, this Ring Transformer here will meet the power requirements. I hope this clears up the confusion.