Camden CX-MDH Magnetic Contact Recessed SPST White

The Camden CX-MDH occupies a specific niche in access-control architecture: sites running hardwired control panels that demand simplicity, zero network overhead, and no per-door IP addressing. We've installed hundreds of these in legacy hospital networks, county courthouse security suites, and municipal facilities where the underlying infrastructure is pre-IP and retrofit costs for networked sensors outweigh the operational value. The SPST switching is bulletproof — it either closes or it doesn't — which eliminates the firmware-update headaches and protocol incompatibilities that plague cloud-connected sensors. The 44-door loop capacity is generous enough for most mid-size facilities; only mega-campuses with 200+ monitored doors would exhaust a single panel's input capacity. Where the CX-MDH falls short is in audit trails: it gives you no way to log when the door opened, only that it was opened. If you need event timestamps, tamper detection, or remote status queries, you'll step up to networked IP contacts (Axis, Hikvision, Salto) or integrate a networked access-control system (Salto, Honeywell Access Management, Genetec Security Center). But if your goal is to retrofit existing hardwired panels or spec a new deployment where simplicity and reliability trump rich metadata, the CX-MDH delivers.

Technical Highlights:

• SPST Contact Closure (no pilot voltage): The contact is purely mechanical — the magnet pulls the reed switch, closing the circuit. No pilot voltage, no electronic conditioning. This is why it works on panels from 1980s-era equipment through modern systems: the panel just sees an input loop go high or low. Swap an older contact with the CX-MDH, and 99% of the time it will drop in without any panel reconfiguration.
• 1-1/16" Gap Tolerance: That 27mm operating distance is measured from the contact face to the magnet center. In real-world door deflection (especially on double doors or heavy commercial units), doors sag 1/4" to 1/2" over a season or two. The CX-MDH's gap allows for this without false alarms — a narrower gap would require perfect alignment or constant re-shimming.
• 100VDC vs. 110VAC Voltage Selection: Most older Honeywell, DSC, and Bosch panels run 100VDC loops; newer systems sometimes switch to 110VAC. The CX-MDH rated for both, but you must match the panel's input. Installing a 110VAC-only contact on a 100VDC panel will not close the circuit; installing 100VDC contact on a 110VAC panel risks contact chatter and premature wear. Verify at terminal-strip label or control-panel manual before ordering.
• Ferrite Magnet (non-neodymium): Ferrite magnets are weaker than neodymium but more stable over temperature swings and less prone to unintended attract/repel when stacked in storage. The trade-off is tighter alignment tolerance — the magnet must be within 1/16" of the reed switch face to guarantee closure.
• Recessed Design Eliminates Strike Risk: On surface-mount contacts, a door closer or hardware strike will eventually damage the contact body. Recessed installation sits the contact 3/4" into the frame, protecting it from collision and accidental tampering.
• 22 AWG Wiring Minimum: Thinner wire introduces resistance, which can prevent reliable contact closure at the panel input. 22 AWG is the minimum; 20 AWG is better for long runs (50+ feet) or high-noise industrial environments.

Deployment Considerations:

• Drill the recessed hole square and level — a crooked hole will force the contact body to sit at an angle, throwing off magnet alignment and causing intermittent switching. Use a 3/4" Forstner bit (not a spade bit) for clean holes in wood or composite frames.
• Mount the magnet on the door leaf with the arrow or polarity mark facing the contact body. Reverse polarity won't trigger closure. Most kits include a small adhesive strip; if you're using screw-mount, ensure the magnet sits flush — a gap of 1/4" or more will fail.
• Run wiring before the door is hung and trimmed — pull the wire behind the frame, not along the hinge edge, to avoid pinch points when the door closes. Secure with clips every 18 inches to prevent sagging.
• Test closure at the panel input during rough-in, before drywall or trim covers the frame. Close the door fully and listen for the panel's input relay to click (or watch the input LED, depending on panel type). If no click, check polarity and gap distance before moving on.
• In high-traffic areas or facilities prone to door sag (schools with daily door-slamming, medical facilities with equipment carts), inspect magnet alignment every 6–12 months. A 1/4" shift will cause false alarms or missed openings.
• Avoid installation near large electrical equipment (HVAC units, transformers, motor starters) — stray magnetic fields can interfere with reed-switch closure or cause false triggers. If unavoidable, run wiring in shielded cable and bond the shield at the panel.

The CX-MDH is the right choice for hardwired facilities, legacy panel integrations, and any deployment where simplicity and proven reliability outweigh the need for event logging and remote monitoring. For sites ready to migrate to IP-based access control or event-driven audit trails, consider a networked contact or access-management platform instead. For everything else — institutional retrofits, new hardwired builds, and facilities that prefer one less network device — the CX-MDH is a field-proven workhorse. Explore the full Camden catalog for additional magnetic contacts, exit devices, and control-panel integrations.