The transformer is 16V and 10Va. I’ve attached two pics. In case it’s hard to see, white wires from the power module are connected to the Front (ADC doorbell installed there) and transformer terminals on the mechanical chime. Gray wires are crimped to the wires that were connected to those terminals. The chime transmitter has 3 wires, one each for Front, Rear, and Transformer, and is connected accordingly. You may also see one extra wire that is not connected; it never was, probably from a 3rd doorbell that this old house had once upon a time.
