SDC ACM-1 Six Input Control Relay Module
The SDC ACM-1 is a six-input access control relay module designed to consolidate multiple activation signals—badge readers, keypads, request-to-exit buttons, door sensors—into a single electromagnetic lock or strike output. Operating at 24VDC with an isolated SPDT (Single Pole Double Throw) relay, the ACM-1 tolerates low-impedance trigger wiring runs up to 1000 feet on 22 AWG cable, eliminating the need for heavy gauge bundles or intermediate power conditioning in long corridor and multi-floor deployments. The module accepts both normally closed and normally open input logic—three inputs of each type—accommodating momentary and maintained activation sequences without rewiring.
Key Features
- SPDT Relay Output: 5A at 30VDC resistive rating. Directly drives 24VDC electromagnetic locks, magnetic strikes, and door holders without additional drivers or relays.
- Six Configurable Inputs: Three N/C (normally closed) and three N/O (normally open) inputs. Allows six separate devices to trigger one strike or lock independently.
- Extended Wire Run Tolerance: Accepts low-impedance signaling up to 1000 feet on 22 AWG cable. Eliminates long-run voltage drop headaches in campus or multi-floor installations.
- Wide Input Voltage Range: 12/24 VDC ±10% (18–26.4V nominal). Tolerates supply sag across extended runs; no external regulation required for standard access control power supplies.
- HID-Compatible Input Logic: Works with HID credential readers, Salto wireless locks, Honeywell access control panels, and any device outputting 12/24 VDC trigger signals.
- Low Current Draw: Maximum 75 mA input load. Negligible impact on access control power supply sizing.
- Compact Footprint: 3¼" × 2" dimensions fit standard DIN rail or surface-mount enclosures in equipment rooms and cabinet installations.
- Lifetime Warranty: Manufacturer warranty covers defects in materials and workmanship for the life of the product.
The ACM-1 bridges the gap between multi-reader deployments and single-strike hardware. In typical commercial and institutional door access control systems, multiple credential readers (main entrance badge reader, emergency exit keypad, accessibility button) often need to release the same strike. Without a relay module, integrators must either wire readers directly in parallel—risking impedance mismatches and voltage drop—or use a separate low-voltage control relay for each reader, multiplying both cost and panel real estate. The ACM-1 solves this by providing a single consolidated relay with flexible input logic.
The isolated relay design is particularly valuable in retrofit and renovation projects where reader locations or strike hardware change mid-deployment. Because the module decouples input signal processing from output relay switching, you can swap readers or adjust input wiring without de-energizing the strike circuit. Input impedance tolerance also means the module works reliably across older, lower-spec access control power supplies common in legacy institutional buildings—no need to replace infrastructure-grade 24VDC PSUs to accommodate new readers.
Integration is straightforward on any system using 12/24 VDC signaling. Wire each reader (or button, or sensor) output to an available N/O or N/C input; connect the SPDT relay output across the strike coil or solenoid latch; supply 24VDC common to the module. No special API, ONVIF compliance, or software licensing—pure relay logic. This simplicity makes the ACM-1 a reliable choice for facilities with limited IT resources or security teams managing heterogeneous hardware (mixed HID/Salto/Honeywell readers on the same floor).
One critical installation consideration: the datasheet does not specify external fuse or surge protection on the relay output. Local fire code and AHJ requirements often mandate strike circuit protection; confirm whether a Class 2 fused disconnect or surge suppression is required in your jurisdiction before final wiring. If the module is mounted in a cabinet remote from the strike, verify voltage regulation under full load across the wire run—extended 22 AWG runs at full 5A relay current can introduce measurable drop, reducing coil voltage and potentially causing incomplete latch engagement. Standard practice is to test strike function at the furthest point in the run during commissioning.
Jerry TildsenPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
We've installed the SDC ACM-1 across office parks, universities, and retail chains where multi-reader door control is standard. The appeal is straightforward: it's a simple, voltage-agnostic relay module that solves the real-world problem of consolidating six independent activation sources (badge reader, emergency egress button, accessibility pad, request-to-exit sensor, manual override, and a supplemental reader for after-hours access) into one strike without daisy-chaining readers in series or rewiring the entire access panel. In our experience, the 1000-foot 22 AWG wire tolerance is the quiet strength—it means you can run trigger wires in conduit alongside building automation runs without upgrading to heavier gauge or intermediate repeater logic. On a typical 300-person office build-out with readers distributed across three floors, that saves labor and materials versus point-to-point 18 AWG runs. The N/C and N/O input flexibility is also underrated; many older badge reader outputs are N/C (de-energize to activate), while newer HID readers are N/O. The ACM-1 doesn't force you to choose—three of each type means mixed reader ecosystems can coexist on one door without logic inversions.
Technical Highlights:
- SPDT Relay Isolation: The dry relay design means the module's logic ground is isolated from the strike power circuit. This prevents ground loop noise from creeping back into reader signaling, a persistent issue in older buildings with long runs. Cleaner signals = fewer false denials and nuisance alarms.
- Voltage Tolerance (12/24 VDC ±10%): Most legacy access control supplies drift toward 22–23V over time; this module is unfazed. No external buck converter, no voltage regulator—just plug it in. On multi-card reader installations where power budgets are tight, that 75 mA input draw is negligible.
- SPDT Output (5A at 30VDC): Sufficient for standard 24VDC electromagnetic locks and mag strikes (typically 2–4A continuous). If you're planning a heavy-duty security door with a 6A+ solenoid, spec a separate contactor. But for 95% of commercial applications—standard electric strikes, mag locks, door holders—the relay handles it without external drivers.
- Compact Dimensions (3¼" × 2"): Fits a standard DIN rail inside any cabinet. In retrofit jobs where panel space is at a premium, this footprint matters—you're not asking for a dedicated 4U enclosure just for one relay module.
- Lifetime Warranty: SDC backs this with a lifetime warranty. In the access control sector, that's a confidence signal; it reflects maturity of the design and minimal field failure rates.
Deployment Considerations:
- Fire code compliance: The datasheet does not list external fuse or surge protection on the relay output. Confirm with your AHJ whether Class 2 or Class 3 fusing is required on the strike circuit. If you're in a fire-rated corridor or high-occupancy space, don't skip this step.
- Long wire runs at full load: The 1000-foot specification assumes low-impedance signaling (inputs). If you're running the 5A relay output 300+ feet to a remote strike, measure voltage drop under load. A 22 AWG run carrying 5A over 300 feet can lose 1–2 volts; verify your strike coil will engage reliably at 22V instead of the nominal 24V.
- Mixed reader logic on one door: The module's N/C and N/O inputs make it easy to integrate a legacy N/C reader alongside newer N/O HID equipment. But document your wiring—if three inputs are N/C (de-energize to activate) and three are N/O (energize to activate), any future technician needs to know that configuration, or they'll commission the door incorrectly.
- Power supply sizing: At 75 mA per module and up to six readers drawing 50–100 mA each, a single door control point can pull 300–400 mA from a 24VDC supply. On larger installations (8–10 doors), you'll need a 2–4 amp supply; this is cheap but easy to overlook in initial budgeting.
- Integration with access control software: The ACM-1 is a dumb relay—there's no API, no software interface, no field wiring protocol. It works with any access control system that outputs 12/24 VDC trigger signals. If you need audit logs, door-open alerts, or remote unlock capability, that logic lives in your main access control panel or cloud platform, not in the module itself.
The SDC ACM-1 is the right choice for integrators and facilities teams managing commercial door access in the 5–50 door range where readers are distributed and you need a bulletproof relay to consolidate activation logic. It's not a full access control system—it's a workhorse component that fits into any 24VDC ecosystem. Explore the full SDC catalog for complementary strike hardware and power supplies.
