The Yokogawa ALR121‑S53 S1 is a serial communication module designed for integration within Yokogawa Safety Control Stations (SCS) and Field Control Station (FCS) platforms. It supports RS‑422 (point-to-point) and RS‑485 (multipoint) interfaces, enabling Modbus slave and subsystem communications with external devices such as PLCs and sequencers. Dual serial ports and support for dual-redundant configuration make it ideal for mission-critical automation systems.

Technical Specifications

Industry Applications

• Enables Modbus Slave communication between Yokogawa SCS and external systems

• Facilitates subsystem communication (e.g. sequencers or PLCs)

• Supports fail-safe architectures in process and safety control environments

• Suitable for use in petrochemical, power generation, water treatment, and industrial automation facilities

• Ideal for long-distance serial communications in distributed installations

Key Advantages

• Dual RS-422/485 Ports allow flexible connectivity and redundancy

• Wide Baud Support accommodates diverse application protocols

• Robust Distance Support: up to 1200 m over RS‑485 networks

• Redundant Configuration Support for critical system reliability

• Compact and Lightweight (approx. 0.34 kg), easing rack-based installation

• Low Power Usage (~0.5 A) and no interference with safety loops.

• Seamless Integration with Yokogawa safety/control stations

Frequently Asked Questions (FAQ)

1. What ports and protocol support does the ALR121‑S53 S1 provide?

   RS‑422 and RS‑485 with Modbus Slave and subsystem communication support.

2. Is it suitable for redundant configurations?

   Yes, dual-module redundancy is supported.

3. What are the maximum transmission distances?

   RS‑422 up to ~15 m; RS‑485 up to ~1200 m total.

4. Which controllers is this module compatible with?

   Yokogawa SSC60, SSC50, SSC57, SSC10, and SNB10D units.

5. What baud rates are supported?

   Ranges from 1,200 up to 38,400 bps.

6. What is the device’s power consumption?

   Approximately 0.5 A.

7. How heavy is the module?

   Approximately 0.3 kg.

8. What are the exact dimensions?

   126.7mm × 32.8mm × 130 mm.

9. Which communication functions can it perform?

   Modbus slave and subsystem communication.

10. Does the module interfere with safety loops?

    No; it is designed to avoid interference with safety control systems.