Can I disable an old security system by disconnecting the transformer?
The wire from the transformer goes into the wall and right back into your alarm panel with the rest of the wires to energize it. Unscrew the wires from the transformer and just tuck them into the wall by the outlet in case you ever want to use the panel again. Tuck the transformer into the alarm box and shut it. There doesn't appear to be any backup batteries but if there are, disconnect them too.