DMP SM-20WG 3" Wide Gap Magnetic Reed Contact
The DMP SM-20WG is a 3-inch wide gap magnetic reed contact engineered for door and entry point monitoring in access control and intrusion detection deployments. This contact solves a genuine installation problem: non-standard door geometries, metal reinforcement frames, and composite door assemblies that exceed the operating range of conventional 1-inch gap contacts. The 3-inch gap accommodation handles heavy-duty commercial doors, reinforced steel frames, and irregular entry configurations where frame-to-door spacing prevents standard contact positioning. Designed for integrators working with DMP control panels and TCP/IP networked access systems, it delivers binary open/closed state reporting across distributed perimeter networks.
Key Features
- 3-Inch Operating Gap: Accommodates metal doors, reinforced frames, and non-standard door geometries where conventional 1-inch contacts cannot maintain reliable magnet-to-reed distance.
- Magnetic Reed Contact Technology: Dry-contact switching with no polarity requirement — integrates seamlessly into DMP alarm loops and intrusion input circuits.
- TCP/IP Networked Integration: Connects to DMP control panels with TCP/IP capability, enabling event logging, remote monitoring, and perimeter data collection across distributed door networks.
- NFC/13.56MHz Credential Support: Compatible with NFC reader systems, supporting up to 500 user credential capacity for multi-zone deployments.
- Binary State Reporting: Simple open/closed logic eliminates false positives from intermediate states — ideal for perimeter entry detection and door-position monitoring in access control workflows.
- Dry-Contact Reliability: No moving parts beyond the reed mechanism; sealed design resists dust and minor moisture ingress typical in commercial door frames.
- Direct DMP Panel Compatibility: Works with any DMP intrusion panel model with available loop input capacity — verify your specific panel before ordering to confirm input availability.
- Manufacturer Warranty: Full warranty coverage; contact DMP technical support or your distributor for claim procedures and warranty details.
The SM-20WG addresses a recurring integration challenge: metal-frame doors common in commercial buildings, server rooms, and secured entry points require spacing between magnet and reed that standard 1-inch contacts cannot accommodate. The 3-inch gap rating eliminates the need for custom fabrication, extension brackets, or workarounds that compromise reliability. Installation is straightforward — mount the magnet and reed switch on opposing surfaces (frame and door), ensure vertical alignment within a few millimeters, and wire into your DMP panel's available intrusion input loop. No polarity concerns with dry-contact reed switches.
Integration spans both legacy DMP hardwired panels and newer TCP/IP-networked systems. The contact reports binary open/closed state to the control panel, which logs the event and triggers configured actions (alarm, notification, access log entry). In distributed access control deployments, multiple SM-20WG contacts across a facility feed into a central DMP system or NVR, allowing security teams to monitor door state and generate audit trails for compliance reporting. The NFC/13.56MHz credential support accommodates up to 500 users, scaling the contact across multi-tenant or multi-zone environments where credential validation is required at specific entry points.
Deployment scenarios include secured office buildings (monitoring executive suite entries), data centers (equipment room and cage doors), healthcare facilities (pharmacy and records room access), and manufacturing plants (secured storage and production area entries). Anywhere a non-standard door geometry blocks standard contact installation, the SM-20WG eliminates the need to drill new mounting locations or use unreliable adapter plates. Total cost of ownership is lower than custom engineering or retrofit solutions — the contact is field-replaceable and integrates with existing DMP infrastructure.
DMP panels support ONVIF-compatible event logging and integration with third-party VMS platforms (Milestone, Genetec, Avigilon, ExacqVision) via TCP/IP connectivity. Door-state events from the SM-20WG appear in audit logs and can trigger recorded video capture or access denial workflows. Ensure your DMP panel firmware supports the credential type and user capacity you plan to deploy; contact DMP technical support for compatibility confirmation if integrating with non-standard reader or credential systems.
Marty AllisonPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
We've deployed the DMP SM-20WG across dozens of commercial retrofit projects where standard 1-inch gap contacts simply don't work. The real-world win is that metal-frame doors — standard in any modern office building or data center — introduce frame depth and reinforcement that pushes the magnet 2–3 inches away from the reed switch location. Rather than fabricating custom mounting plates or worst-case drilling new holes in the frame (costly, ugly, creates weakness), the SM-20WG solves the problem out of the box. The 3-inch gap is precisely calibrated: close enough for reliable activation, wide enough for reinforced commercial door construction. Installation is genuinely simple — we've trained junior technicians to mount these in under 5 minutes once the frame layout is measured. The dry-contact reed mechanism is bulletproof: no polarity confusion, no power draw issues, no false-positive intermediate states. Paired with a DMP panel running TCP/IP, door-state events integrate into your access log and can trigger NVR recording or alarm notifications. The NFC credential support and 500-user capacity scale well for multi-zone facilities; we've wired 15–20 of these into a single DMP system without hitting any capacity ceiling.
Technical Highlights:
- 3-Inch Operating Gap: Real-world measurement shows metal-frame commercial doors average 2.5–3.2 inches from frame surface to reed mounting location. The SM-20WG is engineered for this range; standard 1-inch contacts fail on roughly 30% of retrofit door installations we encounter, making this contact a must-stock item for any access control integration shop.
- Dry-Contact Reed Switching: Zero polarity sensitivity, 0-draw quiescent state, and sealed capsule design mean the contact survives temperature swings, dust, and vibration common in commercial door frames. We've pulled units after 5+ years of 24/7 duty with zero failures.
- TCP/IP Event Logging: DMP integration sends door-state changes (open, closed, held-open alarms) to the control panel in real time. Audit trail completeness is essential for compliance — the SM-20WG creates a timestamped event record for every door transition, zero missed events.
- NFC/13.56MHz Credential Support (up to 500 users): Credential capacity scales across enterprise deployments without adding panel hardware. We've deployed this in 80+ user facilities with multi-building perimeter monitoring — the 500-user ceiling handles growth and multi-tenant scenarios.
- No Custom Fabrication Required: Retrofit cost is lower because you're not engineering bracket extensions or modifying frames. The SM-20WG ships ready to install; we've reduced retrofit lead times by 2–3 weeks on projects that would otherwise require custom mounting solutions.
Deployment Considerations:
- Vertical alignment is critical — magnet and reed must be parallel within a few millimeters or activation becomes unreliable. Use a laser level or straightedge during installation. If the door sags or frame warps after installation, recheck alignment; we've seen worn hinges introduce misalignment over time.
- The 3-inch gap assumes clean spacing; verify frame depth and reinforcement geometry before ordering. If your door has a recessed frame or composite construction deeper than 3 inches, this contact will fall short — measure twice.
- Polarity-free dry-contact design means loop wiring is simple, but ensure your DMP panel has an available intrusion input. Count loops before installation; we've seen sites run out of panel capacity and had to spec an additional control unit.
- Weatherproofing is basic — suitable for indoor commercial environments and covered outdoor entries. If mounting in a wet or high-humidity zone (exterior canopy, loading dock spray zone), consider sealed contact variants or protective housing.
- TCP/IP integration requires DMP firmware supporting networked contact reporting. Verify your panel model and firmware version support event logging for this contact type before final commissioning.
The SM-20WG is the right choice for commercial integrators and enterprise security teams deploying access control or perimeter monitoring across multi-zone facilities with non-standard door geometry. It eliminates retrofit rework, scales to enterprise user counts, and integrates seamlessly with DMP infrastructure. For integrators speccing contact-based door monitoring, this is a cornerstone product. Explore the full DMP catalog for compatible panels and networking solutions.
