The Yokogawa ALR121‑S50 S1 is a serial communication module designed for deployment within Yokogawa Field Control Station (FCS) platforms. It enables reliable communication using RS‑422 or RS‑485 interfaces, and supports functions such as Modbus slave and subsystem communications (e.g. sequencing systems), facilitating data exchange between the FCS and external subsystems or supervisory systems.

This dual‑port module provides both point‑to‑point (RS‑422) and multipoint (RS‑485) communication, with robust industrial-grade performance and seamless integration into Yokogawa’s control architecture.

Technical Specifications

Industry Applications

• Enables Modbus slave communication between Yokogawa FCS and external supervisory systems.

• Facilitates subsystem communications (e.g., sequencing or FA-M3 controllers).

• Used in safety control stations (SCS) for process safety applications (e.g., SSC50, SSC60 series).

• Ideal for industrial automation systems that require serial interfacing over long distances.

• Supports dual-redundant configurations for high-availability critical systems.

Key Advantages

• Versatile Serial Interfaces: Supports both RS‑422 and RS‑485, with broad transmission speed options.

• Dual-Port Design: Two RS‑422/485 ports enable flexible configuration and redundancy.

• Supports Multiple Communication Modes: Compatible with Modbus slave and subsystem communication protocols.

• Long-Distance Capability: Up to 1200 m overall RS‑485 range, ideal for distributed systems.

• Redundancy Support: Allows dual‑module redundancy for mission-critical installations.

• Compact and Lightweight: Weighs only ≈ 0.3 kg, easy for rack-mounted installation.

• Low Power Usage: Simple interface with low current draw (≤ 0.5 A).

• Seamless Integration: Designed for Yokogawa FCS/SCS platforms including AFV/A2FV/ANB units.

Frequently Asked Questions (FAQ)

1. What serial protocols does this module support?

   Supports RS‑422 (point‑to‑point) and RS‑485 (multipoint), with Modbus or subsystem communication.

2. What transmission speeds are supported?

   Ranges from 1200 bps up to 38,400 bps (baud rates selectable per channel).

3. What is the maximum communication distance?

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

4. Can this module operate in redundant mode?

   Yes, the ALR121 supports dual‑module redundancy for critical system reliability.

5. How many ports are available on the module?

   Two independent RS‑422/485 serial ports.

6. What are the power and weight specifications?

   Consumes 0.5 A (24 V DC), weight 0.3 kg.

7. Which control stations does it support?

   Compatible with AFV30/40, A2FV50/70 FCS and ANB10/11 nodes installation.

8. What communication functions are available?

   Includes Modbus slave communication and subsystem communication capabilities.

9. What synchronization method is used?

   Half‑duplex with start-stop synchronization; lag time ~1 ms after transmission.

10. Which types of devices can it connect to?

    Suitable for Modbus masters, FA-series PLCs, safety subsystems, sequencers, and similar devices.