The Yokogawa SNT401 Optical ESB Bus Repeater Master Module is designed to extend ESB bus communication in safety control systems by converting electrical signals to optical signals. It enables long-distance communication (up to 5 km, or 10 km in specific configurations) between safety control units, safety node units, and N-IO nodes. The SNT401 works as the master module in a repeater pair and is typically paired with an SNT501 slave module or S2EN501.

Technical Specifications

Applications

The SNT401 is used in industrial safety and automation environments where long-distance, reliable ESB bus communication is required:

• Extending ESB bus connections between distributed control and safety systems

• Optical signal conversion for improved noise immunity

• Redundant and duplex configurations in critical safety systems

• Centralized or distributed installations in chain or star topologies

Advantages

The SNT401 provides several benefits:

• Enables long-distance (up to 10 km) ESB communication

• Supports both star and chain topologies for flexible system design

• Compact and lightweight design, easy to integrate into existing racks

• Enhanced noise immunity through optical signal transmission

• Supports redundant configurations for high system availability

FAQ

Q1: What is the maximum communication distance of the SNT401?

A1: The SNT401 supports up to 5 km in standard configurations, and up to 10 km in R1.03+ systems with two stages.

Q2: Can the SNT401 be used alone?

A2: No, it must be paired with an SNT501 or S2EN501 at the slave side.

Q3: What are the supported connection types?

A3: Both star and chain topologies are supported.

Q4: Does the SNT401 support redundant configurations?

A4: Yes, it supports duplex configurations for redundancy.

Q5: Is the SNT401 compatible with SNT10D racks?

A5: Yes, it can be installed in SNT10D units specifically designed for optical repeater modules.

Q6: What is the power consumption of the SNT401?

A6: The SNT401 consumes approximately 0.5 A.

Q7: Does the SNT401 include a terminator?

A7: Both options are available: with (/CU1T) or without (/CU1N) terminator.

Q8: What is the weight of the SNT401?

A8: The module weighs approximately 0.3 kg.

Q9: What environmental conditions can the SNT401 operate in?

A9: Optional versions support –20°C to +70°C and ISA G3 standard.

Q10: Can the SNT401 connect directly to the safety node unit?

A10: Yes, through the ESB bus interface module (SSB401) on SNB10D.