The Yokogawa SNT401-53 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 and stable communication between safety control units, safety nodes, and I/O systems. It is typically used together with the SNT501-53 slave module to form a complete optical ESB communication link.
This module is a key component for building large distributed safety networks (star or chain topology) in industrial plants.
Technical Specifications
| Parameter | Specification |
|---|---|
| Brand | Yokogawa |
| Model | SNT401-53 |
| Product Type | Optical ESB Bus Repeater (Master) |
| System Compatibility | ProSafe-RS SIS |
| Function | ESB electrical → optical signal conversion |
| Pairing Module | SNT501-53 (slave side) |
| Network Type | ESB bus optical fiber communication |
| Topology | Star / Chain connection |
| Max Connection Stages | 2 stages |
| Transmission Distance | Up to 5 km (up to 10 km in extended configurations) |
| Current Consumption | ~0.5 A |
| Weight | Approx. 0.25–0.3 kg |
| Operating Temperature | -20°C to +70°C (ISA G3 class) |
| Installation | 19-inch rack system |
According to Yokogawa system documentation, SNT401 is used with ESB coupler modules (SEC401/SEC402 or SSB401) to extend safety node communication via fiber optics.
Physical Characteristics
| Item | Specification |
|---|---|
| Dimensions (W × H × D) | Approx. 32.8 × 130 × 142.5 mm (module dependent rack layout) |
| Weight | ~0.3 kg |
| Mounting Type | 19-inch industrial rack |
| Structure | Optical repeater master module |
| Installation | Control cabinet / SIS rack system |
System Role
The SNT401-53 acts as the master-side optical ESB converter in a distributed safety network.
Typical configuration:
-
ESB bus from safety controller (SSC / SCS / SNB systems)
→ SNT401-53 (Master)
→ Optical fiber link
→ SNT501-53 (Slave)
→ Remote safety node / I/O system
This structure enables long-distance deterministic communication in safety-critical systems.
Recommended Related Models
- Yokogawa SNT501-53 – Optical ESB Bus Repeater Slave
- Yokogawa SNT401 – standard version (non “-53”)
- Yokogawa SNT10D – rack-mounted ESB repeater unit
- Yokogawa SNB10D – safety node unit
- Yokogawa SEC401 / SEC402 – ESB coupler modules
