SDC CR4 4-Door Access Control Board
The SDC CR4 is a 4-door access control board designed for mid-scale deployments requiring independent lock control across multiple entrance points. Operating on standard 24VDC power, the CR4 communicates via OSDP (Open Supervised Device Protocol) with compatible readers and management platforms, enabling credential-based access decisions at the door level without reliance on large centralized panel infrastructure. The board supports up to 250,000 stored credentials, making it practical for multi-building campuses, office parks, or enterprise facilities where distributed access control reduces installation complexity and improves fault tolerance.
Key Features
- Four-Door Control: Individual relay output for each of four doors on a single compact board. Eliminates the need for separate single-door controllers or larger panels in medium-density deployments.
- OSDP Communication: Open Supervised Device Protocol ensures interoperability with OSDP readers, keypads, and management software. No proprietary reader lock-in; standardized protocol reduces vendor dependency.
- 250,000 Credential Capacity: Supports local credential storage for large multi-tenant or multi-building access rosters. Suitable for enterprise-scale facilities without requiring external database queries for every transaction.
- 24VDC Operation: Standard DC power supply eliminates AC infrastructure requirements. Compatible with existing door strike hardware, electromagnetic locks, and maglocks rated for 24VDC.
- Compact Form Factor: 4¼" × 3 13/16" × 5/8" dimensions allow installation in tight electrical enclosures, above-door controller boxes, or cabinet-mounted layouts typical of retrofit projects.
- Lifetime Warranty: Manufacturer warranty covers defects in materials and workmanship for the life of the product, reducing long-term replacement risk on permanent building infrastructure.
- Wired Connectivity: No wireless interference or battery dependency. Direct RS-485 or Wiegand connections to readers ensure deterministic, auditable access events.
- Local Decision Logic: Credential matching and lock control happen at the board level, reducing latency and network traffic compared to centralized cloud-dependent systems.
The CR4 fits the operational sweet spot for mid-scale access control: larger than a single-door controller, smaller than a multi-panel system, and free from vendor-specific communication protocols. OSDP standardization means you can source readers and expansion hardware from multiple manufacturers without rewiring or reprogramming the core controller logic. On a 30-door campus, you deploy four CR4 boards and manage them as a cohesive system through any OSDP-compatible management platform (Salto, Kaba, certain Honeywell suites, or open-source OSDP software).
The 250,000-credential capacity addresses real-world scale: for a multi-tenant office building with 50 tenants and 200 employees per tenant, plus visitors, contractors, and service personnel, local storage eliminates the operational overhead of network failover logic. If your management platform goes offline, the CR4 continues enforcing the last-downloaded credential set. For campuses managing access across multiple buildings, the CR4 allows you to segment control at the building or zone level without centralized single-point-of-failure architectures.
Power consumption is minimal on 24VDC: door strikes and maglocks draw the load, while the controller itself draws milliwatts. Standard industrial 24VDC power supplies (AC/DC converters or battery-backed supplies) are widely available, inexpensive, and easy to integrate into existing electrical distribution. No specialized panel power distribution or UPS engineering is required for typical installations.
The SDC CR4 integrates seamlessly with OSDP readers, keypads, and card/mobile credential platforms that support the protocol. Deployment scenarios include office parks (one board per building, four doors per board), retail chains (entry, emergency exit, manager office, stock room on a single board), and healthcare facilities (isolation zone entry control). The OSDP standard ensures future-proof upgrades: if your credential technology changes from cards to mobile credentials, reader hardware may change, but the CR4 continues functioning as the access-decision point without firmware updates.
Jerry TildsenPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
We've deployed the CR4 across a range of mid-scale facilities — office parks, light manufacturing, healthcare administrative buildings — and it consistently delivers the operational simplicity that OSDP brings to access control. The real differentiator is the protocol: OSDP removes the proprietary reader coupling that trapped you in legacy systems for 10+ years. You get vendor flexibility, standardized credential formats, and the ability to swap readers or management platforms without rewiring the door control logic. On a 12-door office park, we've specified three CR4 boards (one per building section) and integrated them with both Salto cloud and Kaba on-prem management in the same deployment. The 250,000-credential capacity meant zero network round-trips for access decisions on typical tenant rosters. We've also seen the board handle credential changes within 30 seconds of a sync from the management platform — fast enough for same-day onboarding workflows. The one scenario where you might outgrow the CR4 quickly: if you're managing a 500-door campus and need highly granular scheduling (e.g., individual time-windows per tenant per door per day of week), you'd want a true enterprise platform like Genetec or Milestone with a larger controller backbone. For 4–16 doors per physical location, the CR4 is the right cost and complexity match.
Technical Highlights:
- OSDP Protocol Stack: Eliminates Wiegand and proprietary bus dependencies. OSDP 2.2 compliance ensures reader interoperability and future support for emerging credential types (mobile, multi-factor). Real-world consequence: a reader manufacturer discontinues their old line, you swap in a new OSDP reader without controller reprogramming.
- 250,000-Credential Local Storage: No database query latency on each access attempt. For a 500-person multi-tenant building, access grant/deny decisions complete in sub-100ms at the door. Network outage doesn't freeze access to authorized personnel.
- Four Independent Relay Outputs: Each door is individually controlled. One door can be in access-denied mode while another grants entry. Useful for emergency lockdown (lock three doors, leave one open for evacuation) or tenant-specific access windows without panel-level configuration changes.
- 24VDC Standard Power: Off-the-shelf industrial power supplies, no special UPS hardware. For retrofit into existing electrical closets, you can reuse existing 24VDC infrastructure (lighting drivers, HVAC controllers, etc. often already run DC).
- Compact DIN-Rail or Wall Mount: 5/8" depth allows installation above doorframes, inside junction boxes, or on shallow cabinet rails. Retrofit projects where space is constrained — tight electrical rooms or cable trays — benefit from this form factor.
Deployment Considerations:
- OSDP Reader Inventory: Your readers must support OSDP. If you have legacy Wiegand-only readers in the field, the CR4 won't retrofit them without new readers. Audit your existing reader base before committing to OSDP architecture. You may need to plan a phased replacement cycle.
- Four-Door Ceiling: The CR4 controls exactly four doors. If your building section grows to eight doors, you'll need a second board and a way to synchronize credentials across boards (via your management platform). Plan your facility layout before deployment to avoid a split-board scenario mid-project.
- Strike/Magloc Power Isolation: Door hardware power draws (maglocks pull 2–3A at 24VDC) must come from a dedicated supply, not the controller supply. Under-specifying power can cause brownout resets on the board. Size your 24VDC supply for peak simultaneous lock loads plus 20% headroom.
- Network Failover Mode: The CR4 stores credentials locally, so if your management platform is offline, access continues using the last-synced credential set. However, real-time audit logging and credential revocation (e.g., terminating an employee instantly) won't take effect until the network restores. Plan your credential sync intervals and logging strategy accordingly.
- Credential Sync Frequency: Updates to the credential list (adding/removing users) push from your management platform to the board. Sync latency is typically <30 seconds on modern platforms, but in high-turnover environments (retail, hospitality), you may want push-based revocation for immediate employee terminations.
The CR4 is the right choice for integrators and facility managers running 4–16-door deployments where OSDP standardization, local credential storage, and compact form factor outweigh the need for centralized multi-hundred-door panel infrastructure. If you're standardizing on open protocols and want vendor flexibility, the CR4 is a straightforward upgrade path. For a deeper look at OSDP ecosystem options and board sizing, explore the SDC catalog.
