SDC MS-16 Mortise Lock Latch Monitor
The SDC MS-16 is a latch status monitor designed for mortise lock applications in credential-based access control systems. It provides continuous SPDT contact feedback to your access control panel, confirming whether the latchbolt is secured or retracted in real time — eliminating assumptions about strike energization and door closure state. Operating at 30VDC with a 5 Amp contact rating, the MS-16 integrates directly into standard mortise lock door frames where HID credential systems and real-time latch verification are required. This is the tool for facilities that need auditable proof of door latch state on every access event.
Key Features
- SPDT Contact Feedback: 5 Amp rated at 30VDC resistive. Delivers both normally open (NO) and normally closed (NC) terminals to your access control panel, confirming latch state without requiring secondary sensors.
- 30VDC Operation: Runs on standard strike power voltage — no separate monitoring supply needed. Compatible with HID credential systems and legacy access control panels that support deadbolt strike feedback.
- Mortise Lock Integration: 4 13/16" × 11/16" face plate with 1 1/4" minimum depth into mortise pocket. Fits standard commercial door frames without additional modification.
- Continuous Latch Monitoring: Real-time status reporting prevents ghost access (credential read but door latch fails to retract) and confirms door closure after every transaction.
- Deadbolt Strike Compatible: Designed for mortise deadbolt applications where mechanical and electrical latch state must align for audit and safety compliance.
- Lifetime Warranty: Factory backed for the life of the product — reflects SDC's confidence in component reliability in high-traffic commercial environments.
Deployment Context
The MS-16 solves a specific integration problem: access control panels can energize a strike and assume the door opened, but they cannot see whether the mechanical latch actually retracted. On high-security doors, multi-tenant facilities, and healthcare environments where door closure audit trails are required, that assumption is unacceptable. The SPDT feedback wired to your panel's input terminals makes latch state explicit — your access log will show not just credential presentation, but mechanical confirmation of door latch position. Pair it with your existing HID reader and strike power supply; the MS-16 adds visibility without architectural complexity.
Installation is straightforward for integrators familiar with mortise lock preparation. The unit mounts into the standard latch monitor pocket of a mortise lock body — no drilling or custom fabrication. Measure your door frame cutout against the 4 13/16" × 11/16" face dimensions before ordering to confirm fitment. Route a two-conductor wire from the SPDT terminals back to your access control panel's monitoring input. 30VDC strike power and the monitor feedback wire can run parallel in the same conduit; confirm your panel accepts SPDT input at 30VDC before final wiring to avoid compatibility surprises.
Total cost of ownership on mortise lock latch monitoring is low: the MS-16 eliminates the need for secondary magnetic or mechanical latch sensors and adds no ongoing maintenance burden. Unlike wireless door sensors (which require battery management), the MS-16 is hardwired, powered by strike voltage, and delivers contact closure — no network dependency, no edge device firmware, no cloud connectivity. In legacy and modern access control systems alike, the SPDT contact is universally understood, making this a long-term integration anchor.
Jerry TildsenPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
We've specified the MS-16 on hundreds of commercial door retrofits, and it remains one of the most reliable ways to add latch-state transparency to mortise lock systems without tearing apart the door frame. The strength of the MS-16 is its simplicity: it's a mechanical switch mounted in the latch pocket of the mortise lock body. When the latch retracts, the follower arm moves, the switch closes — that's it. No solenoids, no powered moving parts within the monitor itself. On a 10-year-old mortise lock body paired with a new HID reader and an upgraded access control panel, the MS-16 is the fastest path to real-time latch feedback. We've rarely encountered integration friction because SPDT contact input is a native feature on every access control panel made in the last 30 years. The 30VDC operating voltage means you're not managing a separate 12V supply — the strike power drives the monitor, and the contact just reports state.
Where the MS-16 earns its place: high-security suites, healthcare facilities that audit door closure per HIPAA protocols, multi-tenant office buildings where tenant lockouts must be provable, and data centers where physical access logs are tied to logical access. On parking-garage egress doors and loading docks where unexpected closure is a liability, latch feedback prevents the scenario where a resident thinks the door opened (credential beeped) but the strike jammed. We recommend it in any deployment where your access log will be audited by compliance teams or litigation teams — the SPDT contact is evidence, not assumption.
Technical Highlights:
- SPDT Contact (5A @ 30VDC resistive): Wiring to the panel is two conductors — NO and NC terminals let you choose monitoring logic (latch state) that maps to your panel's input card. No external relay or converter needed; the contact closes and opens at latch transition, delivering galvanic isolation between strike power and the panel's input circuit.
- 30VDC Strike-Powered Operation: The monitor draws negligible current — milliamps. It shares the strike power source, eliminating a separate supply and associated voltage drop calculations. Standard 18 AWG or larger conductor pairs the strike power to the mortise lock body; the MS-16 taps that without additional infrastructure.
- Mortise Lock Integration (1 1/4" depth): The latch monitor pocket is standard on commercial mortise locks (Corbin, Schlage, Best, etc.). Fitment is mechanical; if the mortise body is genuine, the MS-16 mounts without modification. Depth is critical — shallow door frames (under 1 1/4" mortise depth) will not accommodate the monitor body, requiring a shallow-depth variant or field adaptation.
- Lifetime Warranty: SDC's warranty reflects component robustness. Mortise lock latch monitors rarely fail under normal service — the switching mechanism is mechanical, not electronic. Over 10–15 years in commercial use, we've seen failure rates under 0.5% across thousands of installations.
Deployment Considerations:
- Measure mortise lock body depth before ordering — the MS-16 requires a minimum 1 1/4" pocket. Older or shallow-frame doors may need a shallow-mount variant or a different monitoring strategy (magnetic sensor on the strike head instead).
- SPDT feedback wiring to your panel is two conductors plus ground if using shielded cable. In high-EMI environments (near heavy electrical equipment), run the monitor feedback in separate conduit from strike power to avoid noise coupling into the contact signal — though in practice, contact closure is robust against EMI.
- Latch alignment is critical during installation. If the latch follower doesn't fully engage the switch cam during retraction, you'll lose contact closure or get false positives (contact flickering as the door bounces). Confirm mechanical alignment before closing the door frame.
- The MS-16 is a latch monitor only — it provides no strike control or solenoid operation. Pair it with a separate 30VDC strike (SDC 1069 or equivalent) controlled by your access panel's output relay. The monitor reports state; the strike is the actor.
- Integration with modern cloud-based access control (Salto, Kastle, etc.) requires that your on-premises panel has native SPDT input handling. Cloud-only systems without local hardware may require a gateway or edge device to capture the contact signal and relay it via API — confirm architecture before specifying on green-field builds.
The MS-16 is built for integrators and security teams who need auditable, galvanic feedback from mortise lock systems. It's not the fastest or most feature-rich latch monitor on the market, but it's the most battle-tested and the easiest to integrate into existing infrastructure. If your facility runs a legacy access control panel, an HID reader, and a mechanical strike, the MS-16 adds latch transparency without replacing the entire stack. Browse our full SDC catalog for compatible strikes and power supplies.
