2 rings (front & back door) mechanical chime

Hi all,My fiance wants 2 rings installed. One on the front door and one on the back door. I would like to keep the hardwired system vs using batteries and would like to maintain a mechanical chime. I looked for cut sheets online and wasn't successful but came across this board.My questions are:1) what voltage and VA transformer do I need for this setup with a mechanical chime?2) is there a compatibility list for chimes?3) can any of the rings work in this scenarioThanks in advance