Reed switch built into magnetic catdch allows longterm, trouble free service.
Designed to detect when a door is closed or open.
Use provided counter plate when stationary part is non-magnetic material.(aluminum, wood, glass etc.)
Type A: Switch opens (off) when counter plate and magnet are together.
Type B: Switch closes (on) when counter plate and magnet are together.
Special design provides screw mounting options in 2 different places.