SP-RDM2 Dual Reader Interface Module

The SP-RDM2 is a relay module designed for industrial access control and security automation systems. It provides dual reader interface capabilities, allowing up to two card readers (or biometric devices) to be connected to an access control panel via an RS‑485 bus. The module also includes SPDT relays for door strike control, alarm output, and auxiliary functions. The SP-RDM2 is part of the SP‑C access control system family, commonly used in building security, industrial facility access, and perimeter control.

Technical Specifications

The SP-RDM2 module supports two independent reader ports, each capable of interfacing with Wiegand, Clock/Data, or RS‑485 based card readers. Power supply: 12‑24 V DC (max 500 mA). Relay outputs: two SPDT relays rated at 2 A at 30 V DC (resistive) for door strike, alarm, or auxiliary control. The module also provides two supervised inputs for door position switches and request‑to‑exit buttons. Communication with the host controller (e.g., SP‑C) is via RS‑485 bus at baud rates up to 115.2 kbps. The module includes tamper detection (enclosure open detection) and LED indicators for power, reader activity, relay status, and bus communication. Dimensions: approx. 120 mm × 80 mm × 30 mm. The module is designed for DIN rail or surface mounting. Operating temperature: 0‑55°C, humidity 5‑95% non‑condensing.

Key Features

• Dual reader interface (Wiegand, Clock/Data, RS‑485)

• Two SPDT relay outputs for door strike and alarm

• Two supervised inputs (door position, REX button)

• RS‑485 bus communication to access control panel

• Tamper detection switch

• Status LEDs for power, communications, and relays

• DIN rail or surface mountable

• Wide power supply range (12‑24 V DC)

• Compatible with SP‑C and similar access controllers

Function in Access Control System

The SP-RDM2 acts as a remote I/O unit for an access control panel. It connects to card readers located at doors, reads credential data, and sends it to the master controller over the RS‑485 bus. When the controller validates the credential, it commands the SP-RDM2 to energize its relay output for the corresponding door, unlocking the door strike. The module also monitors the door position (via a magnetic contact) and the request‑to‑exit (REX) button, feeding those statuses back to the controller to enforce anti‑passback and forced‑door alarms. The RS‑485 bus allows multiple SP-RDM2 modules to be daisy‑chained, serving up to 32 readers per line.

Installation and Wiring

Mount the SP-RDM2 on a DIN rail or directly to a wall using screws. Connect the power supply (12‑24 V DC) to the designated terminals. For each door, connect the card reader’s data lines (D0, D1) and power to the reader port terminals. Wire the door strike (locking device) to the normally open (NO) and common (COM) contacts of the relay. For supervised inputs, connect the door position switch and REX button. The RS‑485 bus (A, B) is connected to the host controller; terminate the bus with a 120 Ω resistor at the last module on the line. Configure the module address using DIP switches (1‑16). The module also includes a built‑in tamper switch that triggers an alarm if the enclosure is opened.

Compatibility

The SP-RDM2 is specifically designed for use with the SP‑C access control panel (e.g., SP‑C, SP‑C4, SP‑C8). It can also be integrated with third‑party access control systems that support Wiegand‑over‑RS‑485 or similar protocols, though configuration may require custom scripting. Supported reader types include 125 kHz proximity, 13.56 MHz smart cards, and biometric readers with Wiegand output.

Applications

Typical installations include industrial facility door control, server room access, laboratory security, and perimeter gate control. The dual reader interface allows two doors (or in/out readers for a single door) to be managed by one module, reducing hardware cost. The supervised inputs ensure that door forced‑open or held‑open conditions are detected and reported.

Diagnostics and Maintenance

LED indicators: PWR (green) – power present; BUS (green) – RS‑485 communication active; RD1, RD2 (yellow) – card read activity on reader ports; RLY1, RLY2 (red) – relay energized. If the BUS LED is off, check RS‑485 wiring and address settings. If a reader fails to read, verify power to the reader (12 V or 5 V, depending on model) and the data line connections. The module retains no user data; all credentials are stored in the central controller. No periodic maintenance beyond visual inspection of wiring and connectors is required.

Environmental and Compliance

The SP-RDM2 is CE and RoHS compliant. It is designed for indoor use in pollution degree 2 environments. Operating humidity 5‑95% non‑condensing. The module is not rated for outdoor use without an additional weatherproof enclosure. The relay contacts are suitable for low‑power DC loads; for AC door strikes, an external contactor may be required.

Conclusion

The SP-RDM2 relay module provides a flexible and reliable interface for connecting card readers and door hardware to access control systems. Its dual reader support, supervised inputs, and RS‑485 bus make it a practical choice for industrial security applications.