That's a good idea. The other idea I have been kicking around is to put a doorbell button next to my door and have a solenoid on the inside of the door that would create a knocking sound when the button is pressed.
That's a good idea. The other idea I have been kicking around is to put a doorbell button next to my door and have a solenoid on the inside of the door that would create a knocking sound when the button is pressed.