MC33C Normally Closed Recessed Window Door Contact Sensor Magnetic Reed Switch 5 Sets Overview A concealed magnetic reed switch designed for reliable door and window contact detection. The MC33C is a normally closed (NC) recessed contact that provides discreet security sensing for residential and commercial alarm and monitoring systems. Sold as a pack of 5 sets, each set includes one recessed reed switch and one matching magnet. Key benefits Discreet protection: Recessed installation keeps the switch and magnet mostly hidden inside the frame, reducing visual impact and lowering the chance of tampering. Clear NC operation: Normally closed wiring is compatible with most alarm panels and security inputs that monitor circuit continuity. An open circuit signals an alarm event when the magnet moves away from the switch. Ready for multipoint coverage: Five sets allow coverage of multiple doors or windows in a single , simplifying installations for small properties or multiple zones. Simple integration: Works with standard alarm control panels, DIY alarm kits, and monitoring systems that accept magnetic contact inputs. Durable everyday use: Compact, lowprofile design fits inside common door and window frames for longterm, unobtrusive service. Features and specifications Model: MC33C Operation: Normally closed (NC) magnetic reed switch Form factor: Recessed contact for installation inside frame and sash Pack contents: 5 sets (each set contains one reed switch and one magnet) Typical applications: Door and window contact sensing for alarm systems and access monitoring Installation notes Recessed mounting requires a small bore or mortise in the frame and sash. Basic drilling and wiring skills are sufficient for installation. Wire the reed switch to the alarm input using the normally closed terminals on your control panel or zone expander. Confirm wiring polarity and circuit continuity before finalizing installation. Position the magnet to align with the recessed switch when the door or window is closed for reliable operation. Use scenarios 1) Residential entry points: Install on front and back doors plus a groundfloor window to add concealed contact sensing to an existing alarm panel. Five sets cover multiple entry points without separate purchases. 2) Sliding glass door protection: Mount the recessed switch in the door frame and the magnet in the sliding sash to detect opening while keeping components hidden from view. 3) Small commercial office or storage rooms: Use one or more sets per internal door to monitor access to supply closets, IT rooms, or stockrooms as part of a wired access or alarm system. Why choose this type of sensor Recessed normally closed magnetic contacts like the MC33C provide straightforward, reliable detection with minimal visual impact. They integrate easily into existing wired alarm systems and are suited to installations where stealth and tamper resistance are priorities. The fiveset pack is practical for small installations or phased security upgrades. Package includes Five MC33C normally closed recessed magnetic reed switch sets (each set: one switch and one magnet) Compatibility reminder Compatible with most alarm control panels and security systems that accept normally closed door and window contact inputs. Verify your panel accepts NC contacts before installation.