One wire runs unbroken from the terminal screw on the button or the bell or buzzer to the terminal screw on the transformer. The second wire runs from the button to one terminal screw on the bell, then from the second terminal screw back to the other screw on the transformer, (Fig. 3).
The button can be mounted on any door as far away from the bell as desired and the bell and transformer can be mounted in any concealed location.