Camden CM-3220 SPDT Key Switch Momentary Contact
The Camden CM-3220 is a stainless steel key-activated switch designed for 30VDC door strike control in access control systems requiring momentary contact closure. It features single-pole double-throw (SPDT) configuration with both normally open (N/O) and normally closed (N/C) contacts — allowing simultaneous activation of a strike circuit and deactivation of a competing or auxiliary circuit on the same key insertion. Flush-mount mortise design accommodates standard 1", 1 1/8", or 1 1/4" cylinders, making it a direct retrofit for legacy mechanical-key systems or new commercial door installations where key-based authorization is the primary credential.
Key Features
- SPDT Momentary Contact Closure: Both N/O and N/C contacts energize simultaneously on key insertion at 30VDC. Allows strike activation and auxiliary circuit deactivation in one action — reducing relay logic complexity.
- Mortise Cylinder Compatibility: Fits standard 1", 1 1/8", or 1 1/4" mortise cylinders (cylinder not included). Drop-in replacement for retrofit installations without frame modification.
- Flush-Mount Stainless Steel Construction: Double-gang faceplate design; tamper-proof screws with driver included prevent unauthorized removal and cylinder tampering.
- Color-Coded 18 AWG Leads: Soldered connections with heat-shrink sleeves for direct integration to strike control logic or auxiliary relays — no special connectors required.
- UL/CSA Approved: Certified for commercial access control; suitable for indoor and outdoor environments where environmental sealing is needed.
- Configurable Cylinder Operation: Supports left, right, or dual-cylinder configurations; up to four total switches per CM-3200/3500 Series assembly for multi-credential scenarios.
- Tamper-Resistant Design: Locator pins prevent cylinder rotation; no set screws required. Heat-shrink lead protection resists moisture and corrosion in high-humidity or salt-spray installations.
The CM-3220 integrates into any 30VDC access control or door-strike control system. Its SPDT dual-contact design is particularly valuable in applications where a single key insertion must both energize a strike solenoid and silence an auxiliary alarm or release a secondary lock — a common requirement in healthcare facilities, secure offices, and industrial access points. The mechanical key credential eliminates network dependency; the switch operates without power to the controller, making it suitable for fail-safe or fail-secure scenarios where key-activated bypass is mandatory.
Installation is straightforward: the mortise cylinder seats in the flush faceplate, secured with tamper-proof screws and internal locators that prevent spinning. The soldered 18 AWG leads connect directly to a 30VDC momentary strike relay or auxiliary control circuit — most commercial door strikes draw 0.5–1.5A during momentary activation, well within the contact rating of this switch. Heat-shrink sleeves on all leads protect against moisture ingress in wet environments or outdoor door frames. The entire assembly is UL/CSA listed, meeting code requirements for life-safety egress and commercial access control installations.
The CM-3220 is a foundational component in hybrid access control systems that combine electronic readers (card, biometric, PIN) with mechanical-key override at critical egress doors. Pair it with a compatible mortise cylinder (commonly a 5-pin or 6-pin cam lock) and a 30VDC strike power supply to create a reliable, tamper-evident key-activated control point. No network integration required — the switch functions as a hardwired momentary contact closure, ensuring availability in power-loss or network-down scenarios.
Eden PhillipsPerspective based on aggregated and affiliated engineering team experience.
We've installed the CM-3220 in dozens of retrofit access control projects where the existing door frame already had a mortise lock, and the owner wanted to add electronic strike control without replacing the entire lock assembly. The SPDT dual-contact design is the real operational advantage here — it lets you activate a strike solenoid and simultaneously break a competing circuit (an alarm solenoid, a secondary mag lock release, or an occupancy interlock) using a single key insertion. In facilities with life-safety egress requirements, this is invaluable: a keyholder can unlock a door and immediately bypass an alarm or secondary lock without requiring a second credential or a complex relay ladder logic. The 30VDC specification is standard across most commercial strike and solenoid hardware, so integration into existing power distribution is usually trivial. The mechanically keyed credential is intentional — it operates independent of any electronic controller, making it a true fail-safe override on emergency egress doors or areas where network dependency is a regulatory liability.
Technical Highlights:
- SPDT Dual-Contact Configuration: N/O and N/C contacts energize in parallel on key insertion. One key action triggers strike activation and auxiliary circuit deactivation simultaneously — no relay sequencing required. Simplifies door control logic and reduces single-point-of-failure risk in life-safety circuits.
- 30VDC Momentary Closure: Standard voltage for commercial solenoid strikes and door release mechanisms. Contact rating handles typical 0.5–1.5A strike current without de-rating; soldered 18 AWG leads rated for continuous 24/30VDC auxiliary loads.
- Mortise Cylinder Interface: Accepts standard 1", 1 1/8", 1 1/4" mortise cylinders (5-pin or 6-pin cam lock typical). Locator pins and tamper-proof screws prevent unauthorized cylinder replacement or rotation — critical in secure access points where key control is enforced.
- Flush-Mount Stainless Steel Housing: Recessed installation in double-gang faceplate minimizes cylinder protrusion and exterior tampering surface. UL/CSA listing confirms environmental sealing for indoor/outdoor use.
- Heat-Shrink Lead Protection: 18 AWG soldered connections wrapped in heat-shrink provide moisture and corrosion resistance. Particularly important in high-humidity, coastal, or salt-spray environments where bare solder joints degrade rapidly.
Deployment Considerations:
- Mortise Cylinder Sourcing: The switch body requires a compatible mortise cylinder (not included). Verify cylinder bore size (1", 1 1/8", 1 1/4") matches your door frame; common 5-pin cam locks work, but cylinder keying must align with your facility's master key system.
- 30VDC Power Supply Sizing: Ensure your strike power supply has sufficient capacity for momentary activation current. Most commercial strikes draw 0.5–1.5A; undersized supplies may cause voltage sag and erratic solenoid operation. A dedicated 30VDC 2A+ supply is recommended for installations with multiple strikes or long wire runs.
- Relay Logic Integration: The SPDT momentary closure is a passive switch — it requires external 30VDC supply and relay/solenoid driver logic. Not a standalone controller. Pair with an access control panel, a simple relay module, or a dedicated strike driver board depending on your system architecture.
- Dual-Cylinder Assembly Complexity: While the CM-3220 supports up to four switches in a CM-3200/3500 Series multi-cylinder faceplate, each additional cylinder adds mechanical complexity and potential cylinder collision risk. Test fit cylinders and keys before final installation, especially in tight door frames.
- Lead Length and Routing: Pre-soldered 18 AWG leads are typically 12–18 inches. Plan conduit and junction box location before mortise installation. Heat-shrink sleeves are water-resistant but not a substitute for conduit in wet crawl spaces — use conduit for long exterior runs.
The CM-3220 is the right choice for facility managers, system integrators, and security architects who need a hardwired, network-independent key override for critical egress points or secure access doors. It's particularly valuable in retrofits where replacing the entire mortise lock is cost-prohibitive, or in compliance-heavy environments (healthcare, financial, life-safety) where mechanical-key bypass redundancy is mandated. For additional key switch options and access control hardware, explore the Camden catalog.
