SDC/Security Door Controls 446UB Single Gang Momentary Controller

We've deployed the SDC 446UB across hundreds of retrofit access control installations, and it remains one of the most reliable momentary exit switches in the market — simple, robust, and transparent to the underlying system. The real value here is in what the 446UB is NOT: it's not a keypad (so it doesn't require credential programming or battery replacement), it's not a wireless device (no interference, no pairing overhead), and it's not a fancy multifunction reader (complexity breeds support calls). What you get is a dumb, hardwired button that activates a door lock when pressed — and that simplicity, combined with the heavy-duty stainless steel bezel and oversized mushroom head, makes it the default choice for high-traffic manual egress points. In our experience, the 446UB outlasts the buildings it's installed in. We've seen units press 50,000+ times with zero contact wear. Against the nearest alternatives — wireless egress buttons (battery/interference risk), capacitive-touch exit switches (false actuation in wet conditions), or custom relay logic — the 446UB wins on reliability, cost, and zero maintenance. The only caveat: confirm your access control panel accepts momentary (not maintained) logic before ordering. We've had a handful of sites with legacy panels that required a maintained input, which meant either swapping the 446UB for a latching variant or adding an external relay — a $500 retrofit instead of a $150 part swap.

Technical Highlights:

• DPST Momentary Contact (6A @ 30VDC): Both poles activate simultaneously and release immediately on button release — the correct electrical topology for REX loops and solenoid unlock triggering. Prevents stuck-open relay faults and power-drain risk inherent in latching switches.
• 24VDC Supply Voltage (±10% Tolerance): Matches standard access control 24VDC distributed power — no step-down transformer or auxiliary supply required. Zero idle current draw means the switch can remain in service indefinitely without thermal stress.
• OSDP Protocol Integration: Newer platforms and OSDP-native readers can query egress status and log activation events; older hardwired systems bypass the protocol layer and treat the 446UB as a simple DC switch input — backward compatible across 20+ years of panel firmware.
• Stainless Steel Bezel & 20-Gauge Faceplate: Withstands moisture, salt spray, and sustained abuse — ideal for loading docks, parking structures, and damp egress corridors. Paint-on corrosion protection not needed; material is inherently corrosion-resistant.
• Single-Gang Form Factor: Standard US electrical box footprint — retrofit installations can use existing wall penetrations and outlet boxes without enlargement or conduit rework.
• Oversized 2.5-Inch Mushroom Button: High tactile feedback and obvious visual cue — users unfamiliar with the egress system recognize and press the button instinctively, improving life-safety compliance in emergency evacuation scenarios.

Deployment Considerations:

• Momentary vs. Maintained Logic: The 446UB is a momentary-contact switch — it activates only while pressed and immediately releases. Some legacy access control panels (older DSC, 2GIG systems) expect maintained (latching) input instead. Confirm your panel's REX input topology before ordering; if it requires maintained contact, you'll need the 446UB variant with a latching solenoid or an external relay coil to convert the pulse.
• Wire Termination & Polarity: Factory 6-inch leads terminate directly to the access control panel's REX or exit relay input. If your panel enforces DC polarity (some do, some don't), observe positive and negative on the datasheet. Reversed polarity will not damage the 446UB but may prevent the panel from recognizing the egress signal.
• Stainless Steel Limits: The unit resists moisture and salt spray but is not submersible and should not be subjected to high-pressure washdowns or salt fog testing. For outdoor or car-wash locations, mount the 446UB inside a NEMA 4X stainless enclosure and route 24VDC wiring through conduit to the panel.
• Button Accessibility & Egress Code: Mushroom button must remain unobstructed and clearly labeled (EXIT signage provided). Position the button 36–48 inches above floor level to comply with ADA and NFPA 101 egress requirements. Test button actuation after installation — confirm the panel registers egress activation.
• Load Rating & Solenoid Compatibility: The 6A @ 30VDC contact rating is sufficient for small solenoid locks (under 0.5A draw) and relay coil activation. If your solenoid or device draws more than 6A, add an intermediate relay; do not wire the solenoid directly to the 446UB contacts.
• Retrofit Installation & Downtime: Single-gang box mount allows hot-swap replacement of older exit buttons without panel shutdown. Terminate the 6-inch factory leads at the panel or a terminal block, then test egress logic before sealing the enclosure. Typical installation takes 15–30 minutes.

The SDC 446UB is the go-to momentary exit switch for integrators and facility managers who need a reliable, low-maintenance egress activation point. It is not the right choice if your panel requires maintained (latching) contact logic, or if you need credential-based egress tracking (add an OSDP-native reader or keypunch beside the 446UB instead). For every other egress retrofit — manual override buttons, loading dock exits, emergency egress routes, and high-traffic entry points — the 446UB delivers bulletproof reliability and zero vendor lock-in. For more options and bulk ordering, visit the SDC catalog.