Door Alarm

  
This circuit emits a beep and/or illuminates a LED when someone touches the door-handle from the outside. The alarm will sound until the circuit will be switched-off. The entire circuit is enclosed in a small plastic or wooden box and should be hanged-up to the door-handle by means of a thick wire hook protruding from the top of the case. A wide-range sensitivity control allows the use of the Door Alarm over a wide variety of door types, handles and locks. The device has proven reliable even when part of the lock comes in contact with the wall (bricks, stones, reinforced concrete), but does not work with all-metal doors.
Door Alarm - schematic




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