Door contact sensor BLOW HO-03F — reed switch magnetic door/window sensor

BLOW HO-03F is a compact reed switch magnetic door/window sensor designed to detect the opening and closing of doors and windows. The sensor operates as a normally closed/open magnetic contact and is intended for integration with alarm panels, security systems and DIY monitoring setups. Its small form factor and straightforward wiring enable reliable state reporting for perimeter protection and basic access control applications.

Advantages

The BLOW HO-03F offers a minimal footprint and simple mechanical design that supports long-term, low-maintenance operation. As a reed contact device it provides fast and unambiguous switching when the magnet is moved away or brought close, ensuring clear open/closed signals. Installation requires only basic wiring and mounting, making it suitable for both professional installers and DIY users. The sensor is compatible with a wide range of alarm panels and wired input modules.

Suitable for

• Perimeter intrusion detection on doors and windows
• Integration with wired alarm panels and control units
• Home and small-office basic access control monitoring
• DIY security and monitoring projects

Key specifications

• Switch type: reed (magnetic) contact, normally closed/open operation
• Mounting: surface mount for door or window frames (two-piece sensor and magnet)
• Connection: wired contacts suitable for alarm panel input wiring
• Operating principle: magnetic actuation by separate magnet piece
• Typical applications: perimeter protection, access state reporting
• Form factor: compact inline contact housing for discreet installation

How to use

Mount the sensor body on the fixed frame and the magnet on the moving part of the door or window so that the two parts align when closed. Connect the sensor wires to the appropriate input terminals of the alarm panel or monitoring device, observing the panel's wiring diagram for normally closed or normally open configuration as required. Test operation by opening and closing the door or window and verifying the change of state on the control panel or monitoring system.

Usage recommendations

Place the sensor and magnet with minimal gap and firm alignment to ensure consistent reed actuation. Avoid installing the magnet near other strong magnetic sources or ferrous objects that could affect operation. For outdoor or damp locations, use appropriate sealing or protective housing to prevent moisture ingress. Periodically check wiring connections and physical mounting for secure contact and reliable performance.