Door contact sensor BLOW 4933# model HO-03i — magnetic reed switch for alarm systems

Wired door contact sensor BLOW HO-03i is a magnetic reed switch intended for integration with alarm and security systems. The sensor detects opening of doors or windows by monitoring the relative position of a magnet and a reed contact: when the magnet moves away, the reed opens and the sensor signals an alarm input. The compact plastic housing is designed for surface mounting on door/window frames and sashes and provides a simple, low-profile solution for perimeter intrusion detection and access monitoring.

Advantages

The device offers simple wired connectivity compatible with standard alarm control panels and low power consumption due to its passive reed mechanism. Its compact dimensions and lightweight housing allow discreet installation on most door and window types without structural changes. The magnetic operation provides reliable, maintenance-light performance with minimal risk of false activation from power interruptions.

Suitable for

• Perimeter intrusion detection on external and internal doors
• Window opening monitoring in residential and commercial premises
• Access control monitoring for cabinets, gates, and secondary entrances
• Integration with alarm control panels and wired security loops

Key specifications

• Operating principle: magnetic reed contact (normally closed / opens when magnet separated)
• Connection type: wired two/three conductor interface for alarm zones
• Mounting: surface mount on frames and sashes
• Housing material: durable plastic enclosure
• Dimensions: compact form factor suitable for tight mounting locations
• Environmental suitability: designed for indoor use in typical residential and commercial environments

How to use

Install the sensor body on the stationary frame and align the magnet element on the moving sash so that the two parts are adjacent when the door or window is closed. Connect the sensor leads to the alarm panel zone input following the panel manufacturer’s wiring scheme, observing polarity if required and including any tamper or end-of-line resistors recommended by the control panel. After installation, test the zone by opening and closing the door or window to confirm the panel registers open and closed states correctly.

Usage recommendations

Place the sensor where the magnet and reed align within the specified gap for reliable detection, avoid mounting where heavy vibration or direct water exposure occurs, and periodically inspect mounting and wiring for secure attachment. For best results, follow the alarm panel manufacturer’s guidelines for zone termination and any required supervision or tamper circuits.