The robust aluminum opening detector is a magnetic contact that you can use to secure larger doors (garages). Unauthorized opening is detected and reported to the alarm center. This opening detector is ideal for mounting on steel and metal doors. Its special design allows you to use it on these materials. The detector consists of a magnetic contact (reed) and a magnet. These are mounted parallel to each other. The circuit of this NC opening detector is closed in the idle state. If the distance between the reed and the magnet increases, the circuit is interrupted and an alarm is reported. Thanks to its extremely robust aluminum housing, the detector is protected against damage caused by driving over it.