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3Wire Dual-Slave Isolated RS485 Hub
3Wire RS2S2 Dual Slave Isolated RS485 Hub
3Wire RS2S2 is a high-performance isolated RS485 hub designed to extend one RS485 bus into two reliable isolated RS485 output channels. It is suitable for industrial environments where RS485 communication is affected by long cable runs, electromagnetic interference, ground potential difference, surge exposure or complex site wiring.
RS2S2 uses optoelectronic isolation and surge protection to improve RS485 communication reliability. It supports automatic RS485 data direction control, transparent half-duplex communication, baud rates up to 115.2kbps and long-distance communication up to 3,000m depending on baud rate and wiring conditions.
Function 1 RS485 input to 2 isolated RS485 outputs
Isolation 2,500V RMS optoelectronic isolation
Protection 600W surge protection and ±15kV ESD protection
Power Supply 9–40VDC, 500mA
Product Overview
RS485 networks are widely used for Modbus meters, PLCs, sensors, remote I/O and control equipment. However, long cable runs, multiple branches, outdoor panels and electrically noisy environments can create communication faults, time delay issues or unreliable data transmission.
RS2S2 helps improve RS485 network reliability by splitting and isolating the RS485 communication line into two output channels. This allows an existing RS485 bus to be extended into two more reliable RS485 interfaces, while reducing the effect of common ground interference and electrical disturbance.
Positioning: Dual-slave isolated RS485 hub for extending, isolating and improving reliability of RS485 / Modbus RTU networks.
Typical Communication Flow
The existing RS485 bus connects to the RS2S2 input. The RS2S2 then provides two isolated RS485 output ports for connecting two separate RS485 device branches or for cascading to additional RS2S2 hubs.
1 Existing RS485 Bus
2 RS2S2 Input
3 Isolated Hub
4 Output Port 1
5 Output Port 2
Key Features
Dual RS485 Output
Extends one RS485 input bus into two isolated RS485 output channels for more reliable branch communication.
Optoelectronic Isolation
Built-in optoisolator provides up to 2,500V RMS isolation for improved communication safety and reliability.
Surge and ESD Protection
Provides 600W lightning and surge protection per RS485 line and ±15kV ESD protection.
Automatic Direction Control
Automatically detects RS485 data flow direction and switches direction accordingly for half-duplex communication.
Long Distance Communication
Supports transmission distance from 0 to 3,000m depending on baud rate, cable type and installation conditions.
Communication Delay Improvement
Designed to help solve RS485 communication time-delay and reliability issues in difficult networks.
Industrial Power Design
Uses external SMPS power supply to reduce common ground interference and improve suitability for outdoor applications.
Wide Temperature Range
Operates from -40°C to +85°C for industrial and outdoor panel environments.
Status Indicators
LED indicators for Power, Transmit and Receive support quick troubleshooting and commissioning.
Typical Applications
RS485 Bus Extension
Extend an existing RS485 bus into two reliable RS485 interfaces for distributed device branches.
Modbus RTU Meter Networks
Improve reliability of RS485 Modbus networks used for power meters, energy meters and PQ meters.
Industrial Automation
Use with PLCs, remote I/O, drives, sensors, controllers and factory automation devices.
Remote Monitoring
Suitable for remote monitoring panels, telemetry systems and distributed site data collection.
Outdoor RS485 Panels
Useful for outdoor cabinets where surge, ESD, ground difference and long cable runs are concerns.
IoTWatt 4.0 Projects
Improve RS485 branch reliability for IoTWatt 4.0 metering, energy monitoring and digital energy audit systems.
Application Modes
The datasheet shows two main application arrangements. In the first, one RS2S2 extends an existing RS485 bus into two reliable RS485 device interfaces. In the second, multiple RS2S2 hubs are connected in parallel to extend the RS485 bus into multiple reliable RS485 branches.
| Application |
Description |
Typical Use |
| 1-to-2 RS485 Extension |
One existing RS485 input bus is extended to two isolated RS485 output ports. |
Splitting one RS485 trunk to two device branches or two remote devices. |
| Multi-Branch RS485 Extension |
Multiple RS2S2 hubs can be connected in parallel to create several reliable RS485 branches. |
Large plants, distributed metering panels, building blocks or long RS485 networks. |
| Cascaded / Expanded Network |
Output ports can be used to continue RS485 communication to additional devices or hub branches, subject to proper network design. |
Extending RS485 networks while maintaining better isolation and branch management. |
| Outdoor / High-Interference Sites |
Isolation, surge and ESD protection help reduce communication problems caused by harsh site conditions. |
Pump stations, outdoor electrical panels, substations, plant perimeters and remote cabinets. |
Application note: The datasheet indicates that a maximum of 128 RS485 hubs can be connected to the RS485 bus in parallel. Practical network capacity depends on cable design, termination, baud rate, device loading, noise level and grounding.
Interface Definition
RS2S2 has one RS485 input terminal block and one output terminal block with two isolated RS485 output channels. The input terminal block also includes the DC power supply terminals.
| Terminal Block |
Block / Terminal |
Definition |
Signal Description |
| Input |
1 |
485B |
RS485 negative input |
| Input |
2 |
485A |
RS485 positive input |
| Input |
3 |
V- |
Power ground |
| Input |
4 |
V+ |
9–40VDC input |
| Output |
1 |
485A1 |
Channel 1 RS485 positive output |
| Output |
2 |
485B1 |
Channel 1 RS485 negative output |
| Output |
3 |
GND |
Isolated ground wire |
| Output |
4 |
485A2 |
Channel 2 RS485 positive output |
| Output |
5 |
485B2 |
Channel 2 RS485 negative output |
| Output |
6 |
GND |
Isolated ground wire |
Wiring note: Always confirm RS485 A/B polarity for each connected device. Different manufacturers may label RS485 polarity differently, so commissioning should include communication verification at each output branch.
Technical Specifications
| Category |
Specification |
| Product Type |
Dual slave isolated RS485 hub / RS485 bus extender |
| Standard |
RS485, EIA / TIA compliant |
| RS485 Input |
4-pin terminal block |
| RS485 Output |
6-pin terminal block, two RS485 output channels |
| Transmission Media |
Twisted-pair or shielded cable |
| Communication Mode |
Asynchronous half-duplex |
| Data Direction Control |
Automatic RS485 data direction control |
| Power Supply |
9–40VDC, 500mA |
| Indicators |
LED indicators for Power (PWR), Transmit (TXD) and Receive (RXD) |
| Isolation Voltage |
2,500V RMS; 500VDC with DC/DC isolation module |
| Baud Rate |
300bps to 115.2kbps |
| Protection |
600W lightning and surge protection per RS485 line; ±15kV ESD protection |
| Transmission Distance |
0 to 3,000m depending on baud rate, from 115.2kbps to 300bps |
| Dimensions |
80 × 50 × 31mm |
| Operating Temperature |
-40°C to +85°C |
| Relative Humidity |
5% to 95%, non-condensing |
Why Use RS2S2?
RS2S2 is useful when an RS485 network needs to be extended, split or protected from interference. Instead of creating unreliable RS485 branches directly from the main bus, RS2S2 provides isolated output channels with protection and automatic direction control.
- Extends one RS485 input bus into two isolated RS485 output channels.
- Improves RS485 reliability in high-interference environments.
- Reduces common ground interference through isolated design.
- Supports long-distance RS485 communication when installed correctly.
- Provides surge and ESD protection for industrial and outdoor wiring.
- Useful for splitting Modbus RTU meter networks into cleaner branches.
- Helps troubleshoot and segment large RS485 systems.
Integration with IoTWatt 4.0
RS2S2 can be used in IoTWatt 4.0 deployments where multiple Modbus meters or RS485 devices are distributed across a site. It helps extend the RS485 network, split the network into better branches and improve communication reliability for energy data collection.
- Use RS2S2 to split one RS485 trunk into two isolated Modbus meter branches.
- Improve communication reliability for IoTWatt 4.0 gateways and RS485 meters.
- Reduce RS485 failures caused by long cable runs, electrical noise or grounding problems.
- Use in remote metering panels, outdoor enclosures and factory floor RS485 networks.
- Support energy dashboards, alarms, analytics, EECA reporting and digital energy audit projects.
Recommended Deployment Checklist
- Confirm RS485 communication protocol, normally Modbus RTU or similar half-duplex protocol.
- Confirm baud rate and match it across the RS485 input and output branches.
- Confirm RS485 A/B polarity at the input and both output channels.
- Use twisted-pair or shielded cable suitable for RS485 communication.
- Confirm cable length, termination resistors, biasing and shielding strategy.
- Confirm whether the installation is indoor or outdoor and whether surge protection coordination is needed.
- Confirm 9–40VDC power supply with 500mA capacity.
- Check LED indicators for Power, TXD and RXD during commissioning.
- Test each output branch individually before connecting the full network.
RS2S2 Supply, Configuration and IoTWatt 4.0 Integration
Saturn Pyro supports 3Wire RS2S2 dual-slave isolated RS485 hubs for RS485 network extension, Modbus RTU branch isolation, industrial automation, remote monitoring, energy metering, outdoor panels and IoTWatt 4.0 data collection projects in Malaysia.
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