door buzzer alarm
first of all if the contacts are magnetic, place the contact that is to be wired on the door frame, the magnet on the door,
Run the red wire from the transformer to one lead on the contact, from the other lead on the contact take the red to the buzzer. From the transformer run the white to the buzzer. The power will be on the red wire.
If this doesnt help post with more info. I've done hundreds of these