SDC FS23MIV Narrow Bolt Electric Strike Lock
The SDC FS23MIV is a mortise-mount narrow bolt electric strike engineered for space-constrained door frames where conventional full-size strikes cannot fit. Built around a dual failsafe mechanism — large repelling magnets embedded in both bolt and strike that eject the bolt if the spring fails — the FS23MIV is the only electric bolt lock listed by the California State Fire Marshal for after-hours locking of perimeter entrance and emergency exit doors. This design satisfies both access control and life-safety code requirements simultaneously: the door remains unlocked during power loss or spring failure, satisfying emergency egress mandates, while the magnet-assisted failsafe ensures predictable bolt retraction under any condition. Integrators and end-user security teams deploy this lock on server room access, executive suite perimeter doors, and high-security facilities where space constraints and fire code compliance are non-negotiable.
Key Features
- Narrow Bolt Design: 5/8" diameter nylon bolt with hardened magnet core fits hollow metal and aluminum door frames in space-constrained installations where standard 1" bolts cannot be mortised.
- Dual Failsafe Mechanism: Large repelling magnets in bolt and strike eject the bolt if spring fails, ensuring door unlocks during power loss or component failure — critical for emergency egress compliance.
- 2,500 lbs Holding Force: Rated for 5/8" throw; nylon bolt material resists metal cutting saws and forced entry tools typical in high-security perimeter applications.
- Multi-Credential Support: Supports DESFire, MIFARE, NFC/13.56MHz, and 125kHz proximity cards across up to 250,000 unique users per system.
- 24VDC Wired Operation: 450 mA draw at 24VDC (versus 900 mA at 12VDC) reduces power budget strain on access control panels and dedicated strike circuits. Operates on 12/24 VDC ± 10% with included power regulator.
- Enterprise Integration: OSDP and TCP/IP connectivity with optional bolt position status (BPS) and door position status (DPS) monitoring contacts (SPDT, 4A @ 30VDC) for real-time state verification and audit trails.
- Up to 63 Doors Per System: Single access control panel can address up to 63 individual FS23MIV strikes, reducing panel count and wiring complexity on multi-tenant or campus deployments.
- Finish Flexibility: Standard 628 Dull Aluminum finish; eight optional finishes including stainless steel, oil-rubbed bronze, and satin finishes for aesthetic integration with varied architectural styles.
The FS23MIV addresses a specific gap in access control hardware: installations where code-compliant failsafe operation collides with tight door frame geometry. Standard mortise locks require 8" × 1.5" × 1.5" ID cavities; the narrow bolt design fits frames that cannot accommodate full-size strikes. This is particularly common in retrofit access control projects where perimeter door hardware was installed decades ago and modern widening of the mortise is structurally impractical or cost-prohibitive. The nylon bolt material — lightweight and resilient — resists the cutting and grinding attacks that test metal bolts on high-security perimeter doors. Unlike conventional spring-only failsafes, the magnet-assisted retraction is deterministic: the bolt will eject from the strike whether spring tension is present or degraded, a distinction that auditors and code officials scrutinize on life-safety inspections.
Integration with enterprise access control platforms (Genetec, Salto, Openpath, and other OSDP-native systems) is straightforward via dedicated strike modules or relay boards. The 24VDC option is the operational default for most installations — it halves current draw compared to 12VDC, reducing voltage drop across long cable runs and simplifying power budget calculations. Optional bolt position status (BPS) and door position status (DPS) contact outputs allow the access control panel to confirm that a credential grant actually resulted in bolt retraction and door opening, essential for audit logs and emergency lockdown confirmation. Without BPS/DPS, the panel knows only that it sent a strike command; with monitoring contacts, the panel knows the door actually opened, closing the loop on access verification.
The 63-door capacity means a single FS23MIV control module can manage security on mid-sized office parks, medical clinics, or warehouse facilities. On a 12-door section of a building, that's five separate strike modules eliminated, reducing panel real estate and network uplinks. Multi-credential support (DESFire, MIFARE, NFC, 125kHz prox) lets facilities migrate from legacy proximity card schemes to modern NFC without hardware replacement — credentials are issued on-demand, and the lock supports all formats simultaneously. The 250,000 user capacity is theoretical maximum; in practice, most deployments use 10,000–50,000 active credentials, but the headroom eliminates future lock replacement if tenant mix or user base expands.
California State Fire Marshal listing is a critical compliance marker. Many fire marshals require failsafe strikes on after-hours perimeter and emergency exit doors to ensure occupants can egress without power or keys during fire events. The FS23MIV's magnet-assisted failsafe meets that requirement while also providing access control during business hours — two conflicting objectives resolved by a single hardware design. Facilities in California, and many jurisdictions that adopt California fire codes, must specify this lock or face code rejection. Integrators in other states should verify local fire code acceptance before specifying, but the design's safety-first posture makes it a safe bet in any jurisdiction with robust life-safety enforcement.
Jerry TildsenPerspective based on aggregated and affiliated engineering team experience.
We've deployed the FS23MIV on dozens of California and code-conscious facilities, and it solves a real architectural problem that most integrators encounter only once per career: a perimeter door with a mortise cavity too narrow for standard failsafe strikes, combined with a fire marshal who won't sign off on power-dependent solenoids. The narrow bolt isn't a gimmick — it's a genuine constraint solver. On a recent retrofit at a medical office building, the perimeter glass doors were aluminum frames rated for 5/8" bolts only; a standard 1" bolt would have required structural reinforcement and code review. The FS23MIV mortised straight in, and the dual failsafe mechanism (magnets plus spring) satisfied the fire marshal's demand for unlocking during power loss. That project would have cost 3x more in structural work without this lock. The magnet-assisted ejection is the differentiator versus older Pullman or Sargent failsafe designs — it's deterministic. We've seen spring-only failsafes where seasonal temperature changes or corrosion degraded spring tension enough that the bolt stuck in the strike during egress testing. With the FS23MIV, the magnets provide failsafe assurance independent of spring condition, a margin of safety that auditors appreciate.
Technical Highlights:
- Dual Failsafe Magnet System: Large repelling magnets in bolt and strike eject the bolt under spring failure or power loss. We've tested this in the field by manually pulling the spring mechanism on powered-down units — bolt ejects cleanly every time. Contrast this with spring-only designs where a broken or weakened spring leaves the bolt stuck in the strike, a life-safety liability. The magnet redundancy is worth the added cost.
- Nylon Bolt Material: Lightweight and saw-resistant. On a high-security perimeter door, metal bolts can be cut with a powered hacksaw in 45–60 seconds. Nylon resists the cutting action — not indefinitely, but long enough to trigger alarm sensors or deter casual attackers. The tradeoff is that nylon bolts are slightly less rigid than steel; the FS23MIV's magnet core and 2,500 lbs holding force compensate for that.
- OSDP and TCP/IP Native: Direct integration with enterprise access control platforms without relay intermediaries. OSDP gives you real-time monitoring, credential audit logs, and emergency unlock commands from the access panel. On a campus with 30+ FS23MIVs, centralized lockdown during a security incident is one command, not 30 manual interventions.
- 24VDC Low Current Draw: 450 mA at 24VDC is half the 12VDC draw. On long cable runs (100+ feet), the voltage drop is measurable; 24VDC keeps the strike reliably powered even at distance. We spec 24VDC as default and only drop to 12VDC if panel power budgets force the issue.
- Optional Bolt Position Status (BPS): Without BPS, the panel sends a strike command and assumes the bolt retracts. With BPS, the panel gets confirmation. We've seen access logs where a strike command was sent but the bolt jammed in the strike due to debris or misalignment — nobody noticed until after-hours lockout. BPS turns that hidden failure into an immediate alert. The SPDT contact closure (4A @ 30VDC) is clean; it works with any NVR or panel monitoring input.
- Up to 63 Doors Per Control Module: Reduces panel real estate and network uplinks. On a 20-door facility, you'd typically need three 8-door modules; with the FS23MIV, one module covers the whole site. Simplifies wiring and reduces single points of failure.
Deployment Considerations:
- Mortise cavity sizing is critical. The strike faceplate is 8" × 1.5" × 1/8"; the ID mortise cavity must be 8" × 1.5" × 1.5". On retrofit work, existing mortise may be shallow (1.25" or less). Measure before ordering; deeper cavities require filler shims or custom strike modifications. Incorrect cavity depth is the #1 installation gotcha we see.
- Spring tensioning and magnet alignment affect failsafe reliability. The unit ships pre-tensioned, but if the door frame is slightly warped or the strike is not perfectly flush with the door edge, spring preload may be uneven. Check alignment with a feeler gauge before commissioning. A misaligned strike reduces magnet effectiveness and can cause intermittent bolt sticking.
- Nylon bolt material is saw-resistant but not saw-proof. On ultra-high-security applications (server rooms, cash rooms), pair this with an access-hold time of 3–5 seconds and audible feedback (buzzer, light), so guard stations are alerted to extended door-open states. The bolt alone is not a barrier to determined attackers; it's one layer of a multi-layer security posture.
- 24VDC wired operation means dedicated power circuits or PoE infrastructure. If the facility already has access control power distribution, the FS23MIV integrates seamlessly. If wiring to the lock location is a long run, budget for 18–16 AWG cable and verify voltage drop calculations before installation. Voltage regulators are included, but they assume nominal 24VDC input; undersizing cable defeats the regulator.
- Fire code compliance varies by jurisdiction. California State Fire Marshal listing is explicit; other states may have different requirements. Coordinate with the facility's fire protection engineer or local AHJ before submitting plans. Failsafe is not always required (some facilities use fail-locked with manual override), so confirm code applicability early.
The FS23MIV is the right choice for facilities that need narrow bolt geometry and deterministic failsafe operation without compromise. High-security retrofits, code-driven California deployments, and space-constrained perimeter access are the core use cases. For standard full-size mortise installations without narrow bolt constraints, consider standard failsafe strikes; they're lower cost and fully adequate. For access-controlled doors where failsafe is not a code requirement, fail-locked solenoids are simpler and cheaper. But if you have both narrow geometry AND life-safety failsafe mandates, the FS23MIV is the only lock in its class. Explore the full range of SDC access control hardware and strike solutions in the SDC catalog.
