Door magnetic contact sensor BLOW 4927# HO-03G white, reed switch door/window sensor

Wired door/window magnetic contact sensor BLOW 4927# HO-03G in white is a two-part reed switch sensor that detects the opening and closing of doors and windows. The compact sensor body contains a magnetic reed switch and is paired with a separate magnet; when the magnet moves away, the circuit changes state to signal an open or closed condition. Designed for integration into wired alarm systems and access control installations, this reed switch sensor provides a simple and reliable method for monitoring entry points.

Advantages

The BLOW reed switch sensor offers a straightforward wired connection that is compatible with a wide range of control panels and alarm devices. Its compact white housing enables discreet installation on door and window frames. The mechanical reed switch design delivers low power consumption and a stable contact signal with minimal electronic complexity. Installation requires only basic tools and standard wiring practices, making it practical for both professional installers and experienced DIY users.

Suitable for

• Wired burglar alarm systems for perimeter protection
• Access control systems for door state monitoring
• Intrusion detection on windows, doors, cabinets or gates
• Remote monitoring setups where a dry contact input is required

Key specifications

• Sensor type: reed switch magnetic contact
• Configuration: two-part sensor body and magnet
• Mounting: surface mount on door or window frame
• Connection: wired contacts for dry contact input
• Operating state: detects open/closed positions based on magnet proximity
• Housing color: white

How to use

Position the sensor body on the fixed frame and align the magnet on the moving part of the door or window so that both parts are adjacent when closed. Secure each part with screws or adhesive according to the surface material and application. Connect the sensor’s wired contacts to the alarm panel or control unit input configured for normally closed or normally open operation as required by the system. Test the installation by opening and closing the door or window to confirm that the control panel registers the state changes correctly.

Usage recommendations

For reliable operation, mount the sensor on clean, dry surfaces and maintain the recommended gap between the sensor body and magnet—typically a few millimetres—so the reed switch changes state consistently. Route wiring to avoid sharp bends, mechanical stress, or exposure to moisture. If used outdoors or in high-humidity environments, protect connections and the sensor with appropriate sealing or enclosures. Verify compatibility with the control panel input type (NC/NO) before final wiring.