SDC 55-DU Mortise Lock Electric Strike 24VDC OSDP
The SDC 55-DU is an electric strike designed for mortise locks and mortise exit devices in high-traffic and high-security installations. Supporting up to 1" deadbolt throw with 2,500 lbs static holding force, the 55-DU handles retrofit and new-build deployments where door security and credential management must scale. OSDP and TCP/IP protocol support integrate directly into modern access control systems, while onsite-configurable fail-safe and fail-secure modes adapt to your security policy without hardware changes. Field-reversible operation and six interchangeable faceplates eliminate centerline relocation during retrofit into existing ANSI 4-7/8" strike prep openings — a critical cost and labor advantage in multi-door projects.
Key Features
- Credential Capacity: Up to 250,000 HID-compatible user credentials. Scales from single-door retrofits to campus-wide deployments without secondary credential servers.
- OSDP & TCP/IP Protocols: Native access control system integration. Works with Salto, Genetec Synergis, and other OSDP-compliant platforms — no translation layer required.
- Fail-Safe & Fail-Secure Modes: Field-reversible configuration. Power-locked (fail-secure) for maximum security; power-released (fail-safe) for life-safety compliance — no rewiring on changeover.
- 1" Deadbolt Support: Up to 1" deadbolt throw capacity. Exceeds standard strike specs and accommodates high-security mortise cylinders without modification.
- UniFLEX™ Six-Faceplate Design: Types A–F cover cylindrical locks, mortise locks with deadlatch, and mortise deadbolt configurations. Retrofit into standard ANSI 4-7/8" strike prep without frame relocation.
- 24VDC Wired Power: Standard PoE-compatible voltage. <13W draw per door — works on shared power rails with other access hardware.
- 2,500 lbs Static Holding Force: High-security rating suitable for commercial entrances, secured areas, and high-occupancy facilities.
- Non-Handed Installation: Single strike body adapts to left-hand or right-hand door preparation. Reduces inventory and installation lead time in retrofit scenarios.
The 55-DU's modular design addresses a real pain point in legacy access control: retrofit installations typically require new frame prep or centerline relocation, adding weeks of lead time and cost. The six interchangeable faceplates eliminate that constraint. Install the strike body once; swap faceplates onsite to match whatever mortise lock configuration is already in the door frame. On a 12-door retrofit into an existing facility, that's the difference between coordinating two separate site visits (one for frame modification, one for hardware install) versus a single install day.
Protocol flexibility matters in mixed-vendor environments. OSDP native support means the 55-DU reports lock state and credential events directly to your access control panel — no middleware, no serial gateway, no latency. TCP/IP fallback ensures compatibility with IP-based systems. HID credential format keeps the strike aligned with your existing card and reader infrastructure, lowering training and support overhead.
Fail-safe and fail-secure switching is a field-level convenience often overlooked until you're three months into a deployment and building policy changes. The 55-DU lets you reconfigure electrical behavior onsite without opening the strike or replacing solenoids. Fail-safe (power-energized to unlock) is required for interior stairwells and emergency exits under IBC; fail-secure (power-de-energized to lock) protects sensitive spaces like data rooms or executive suites. The ability to flip that behavior during commissioning without a technician callback saves integration overhead.
All-stainless steel construction and a lifetime warranty reflect SDC's focus on durability in high-traffic sites. The strike is UL Listed for burglary and 3-hour fire rating, meeting compliance requirements for institutional and commercial facilities. Horizontal alignment adjustment is factory-provided for field tuning to ensure smooth latch engagement across variant frame and jamb conditions.
Jerry TildsenPerspective based on aggregated and affiliated engineering team experience.
We've been speccing SDC mortise strikes into retrofit access control projects for over a decade, and the 55-DU is one of the few that actually earn their premium cost in labor savings. The interchangeable faceplate design sounds like a marketing gimmick until you're standing on a ladder looking at an existing mortise lock configuration that doesn't match your standard spec. On a typical 8-door retrofit into a historic building, you'd normally eat two site visits: one to modify frame prep, one to hang the strike. The 55-DU cuts that to one. We've seen integrators recover the hardware cost difference in saved labor on the third or fourth retrofit project alone. That said, it's not a sledgehammer solution — the geometry of your existing lockset prep has to fall within the ANSI 4-7/8" standard, and you need to confirm faceplate compatibility before ordering. Get the datasheet and physically measure your strike openings.
Technical Highlights:
- OSDP Native Protocol: Direct integration with Salto KMS, Genetec Synergis, and other OSDP platforms. No serial gateway, no latency between credential read and strike energization. On a 16-door project, that's measurably faster response than TCP/IP gateway-mediated systems during high-traffic periods.
- 250K Credential Capacity: Scales to multi-building campuses without secondary credential servers. If you're managing 8,000+ users across 30 doors, local credential storage eliminates network dependency — strikes remain operable if the access control panel loses WAN connectivity.
- Field-Reversible Failsafe/Failsecure: Reconfigure electrical behavior onsite without opening the strike housing or swapping solenoids. Critical when building code enforcement or tenant security policy changes mid-deployment — you avoid a second service call.
- 1" Deadbolt Support & 2,500 lbs Holding Force: Handles high-security cylinders and heavy-use entrances. If you're securing a data room, executive suite, or tier-one evidence storage, the 55-DU's holding force exceeds most standard commercial requirements without overkill.
- 24VDC <13W Draw: Low-power design. Shares power rails with badge readers and door sensors — reduces conduit runs and PSU sizing in retrofit wiring plans.
- UL Listed, Stainless Steel, Lifetime Warranty: Built for institutional durability. In healthcare, correctional, and high-occupancy commercial, the warranty eliminates replacement-cycle guesswork. Stainless components resist salt-air corrosion in coastal installations.
Deployment Considerations:
- Confirm your existing door frame strike opening is ANSI 4-7/8" standard before ordering. Non-standard prep (older frames, custom installations) requires frame relocation — the faceplate flexibility doesn't rescue those jobs. Measure twice, order once.
- OSDP wiring runs must be isolated from high-voltage power and lighting circuits to avoid noise coupling. Use shielded twisted pair (STP) for >100 feet of runs; differential line drivers are often worth the cost in electrically noisy industrial environments.
- The fail-safe/fail-secure DIP switch configuration is field-settable but requires strike power-down to reconfigure. Document your setting at commissioning and photograph the switch positions — you'll reference it on every service call three years hence.
- On retrofit installations with multiple faceplate types in a single building, color-code or label the strike bodies before installation. Field technicians will otherwise spend 20 minutes per door identifying which faceplate is required during emergency service.
- Horizontal alignment adjustment is a factory feature, but tight frame tolerances (±1/16") are critical for reliable latch engagement. Work with your door frame manufacturer on tolerance specs — cheap frames cost you trouble calls.
The 55-DU is the right choice for integrators managing multi-door retrofit projects where centerline relocation is a budget killer, or for new builds where credential capacity and protocol flexibility must scale across 8+ doors without secondary servers. If you're doing single-door commercial lock-and-key replacement, a basic cylindrical strike is cheaper and simpler. For everything else — healthcare, education, enterprise, mixed-use retrofit — the modular design and OSDP protocol support justify the investment. Learn more about SDC's full portfolio at the SDC catalog.
