Magnetic contact detectors belong to the essential devices of perimeter protection. They are used to protect doors, windows, etc., by triggering alarm when they are open. The S-1 detector is designed for surface mounting by fastening it with screws e.g. to window frame or door frame. S-1 consists of two watertight parts: the reed switch (magnetic) sensor and the magnet. Moving one part away from the other breaks the sensor circuit, which is indicated as a violation. Additionally, the detector is provided with a tamper loop.