The Yokogawa SNT401 is an Optical ESB Bus Repeater Master Module used in Yokogawa ProSafe-RS Safety Instrumented Systems (SIS).
It is designed to convert ESB bus electrical signals into optical fiber signals, enabling long-distance, high-reliability communication between safety control units, safety nodes, and I/O subsystems.
When paired with the SNT501 slave module, the SNT401 allows engineers to build extended ESB bus networks (star or chain topology) for large distributed safety systems in oil & gas, petrochemical, and power plants.
Technical Specifications
| Parameter | Specification |
|---|---|
| Brand | Yokogawa |
| Model | SNT401 |
| Product Type | Optical ESB Bus Repeater (Master) |
| System Compatibility | ProSafe-RS / ESB bus architecture |
| Function | Electrical-to-optical ESB signal conversion |
| Pairing Module | SNT501 slave module |
| Network Type | ESB bus optical fiber communication |
| Topology | Star type / Chain type |
| Max Connection Stages | 2 stages |
| Max Transmission Distance | 5 km (up to 10 km in certain Vnet/IP configurations) |
| Current Consumption | ~0.5 A |
| Operating Temperature | -20°C to +70°C (ISA G3 class) |
| Installation | Rack-mounted system unit |
The SNT401 is part of Yokogawa’s optical ESB bus extension system, ensuring stable and deterministic communication across distributed safety networks.
Physical Characteristics
| Item | Specification |
|---|---|
| Dimensions (W × H × D) | Approx. 482.6 × 221.5 × 146 mm (rack system dependent) |
| Weight | Approx. 0.3 kg (module only) |
| Mounting Type | 19-inch industrial rack |
| Structure | Optical repeater module assembly |
| Installation | Control cabinet / SIS rack system |
System Role
The SNT401 acts as the master-side optical repeater in the ESB communication chain.
Typical architecture:
-
ESB bus from controller (SSC / SCS / SNB systems)
→ SNT401 (Master)
→ Optical fiber link
→ SNT501 (Slave)
→ Remote safety node / I/O system
This enables long-distance distributed safety system design without signal degradation.
Recommended Related Models
- Yokogawa SNT501 – Optical ESB bus repeater slave module
- Yokogawa SNT10D – ESB bus repeater rack unit
- Yokogawa SNB10D – safety node unit
- Yokogawa SSC series – safety control stations
- Yokogawa SNT411 – optical interface variants
