Magnetic contact sensor Magnetic Contact MS-20M AM422 — reed switch security sensor, surface-mount

Magnetic Contact MS-20M AM422 is a surface-mount reed switch security sensor designed to detect the opening of doors and windows. The device consists of a magnet and a contact unit; when the magnet moves away from the contact unit, the circuit changes state and the sensor signals an opening event. Compact and simple in design, this magnetic contact sensor integrates with alarm panels and control systems for residential and commercial intrusion detection and perimeter monitoring.

Advantages

The sensor offers dependable contact switching with low power requirements and compact dimensions suitable for discreet installation. Its surface-mount format simplifies fitting on a variety of frame and sash profiles without recessed mounting. The reed switch mechanism provides a mechanical, fail-safe means of detecting relative movement between magnet and contact, enabling straightforward wiring to conventional alarm inputs.

Suitable for

• Monitoring doors and windows in homes and apartments
• Perimeter and access control for offices and small commercial premises
• Integration with wired alarm panels, control panels and automation systems
• Temporary or retrofit installations where recessed mounting is not possible

Key specifications

• Type: Surface-mount reed switch magnetic contact
• Operation: Magnet and contact unit that change state on separation
• Contact type: Normally closed / normally open switching depending on wiring
• Mounting: Surface mounting for frames, sashes or flat surfaces
• Power requirements: Passive reed switch (no internal power source required)
• Connection: Wired terminals for direct alarm panel input
• Dimensions: Compact profile suited for discreet placement

How to use

Mount the contact unit on the fixed frame and align the magnet on the moving sash or door so that the two elements come within the specified gap when closed. Connect the sensor’s wires to the alarm or control panel input following the panel’s wiring scheme for magnetic contacts. Test the alignment and circuit operation by opening and closing the door or window and verifying that the control panel registers the change of state. Ensure secure fastening and protect wiring runs from mechanical damage.

Usage recommendations

Install the sensor where the magnet and contact can remain aligned within the recommended gap; avoid placing the magnet on curved or uneven surfaces that may change alignment. For reliable operation, route and secure connection wires to prevent pulling or water ingress, and perform periodic tests as part of routine security system maintenance.