SCADALink SS20 SCADASwitch Modbus Multiplexer (Mux)

  • SS20 SCADASwitchThe SCADASwitch is used for Modbus Multiplexing & Communication Monitoring


SCADALink SS20 SCADASwitch – Modbus Multiplexer (Mux) / RS-232 Switch

The SS20 is a datacom interface device for SCADA & industrial control applications where two independent host or master devices need access to a slave device or network of slave devices, and/or to provide communications failure detection of serial networks.
The SCADASwitch SS20 has two RS-232 input ports and one output port that has both RS-232 and RS-485 interfaces. The SS20 also has a USB connection for configuration, Local operator interface to connected devices, and built-in protocol analyzer. With low power draw, small size, DIN rail mounting, and Class I Div 2 rating it is ideal for use in remote EFM/RTU applications.

SCADA Host/Modbus Multiplexing Mode

Allows 2 SCADA hosts to simultaneously poll the same network of RTU / EFM devices. The SS20 can perform multiplexing on any request-response protocol including Modbus RTU, ASCII,  ROC Protocol, and BSAP Protocol.


Modbus RTU Address Translation

Translates Modbus address on Input Port to a different address on Output Port. This feature is useful when the same RTU exists on 2 different SCADA networks and needs to be addressed with a different Modbus address on each network.

Modbus Register Write Blocking

Prevent Modbus Writes to PLC/RTU/EFM on a specific Input Port. This feature can be used to grant Read-Only access to a third-party SCADA host.

Communication Watchdog

Monitor communications traffic through the SS20 and indicate com failure via relay output. This feature can be configured to watch for specific types of messages or specific addresses and has configurable timeout settings and relay output states.

RS232 Radio Keying

Allows an RTU with no handshaking signals to key a radio modem that requires keying.

RS485 Conversion

Converts RS-232 to RS-485.

Simultaneous RS232/RS485 Outputs

Allows flexibility in SCADA Installations where both RS-485 and RS-232 devices need to be interfaced without adding extra converters or serial splitters.  Isolated RS-485 Outputs prevent ground loops.

Relay Output

The SS20 has a Form-C Relay that can be used for communications monitoring. The relay can be configured to switch on time-out of SCADA communications. This can be used as an input to a PLC or RTU input to indicate  SCADA communication failure.

USB Override (LOI) Mode

When the USB Port is connected and the USB mode switch is set to LOI (Local Operator Interface), the USB port overrides the RS232 inputs and routes USB traffic directly to the RS232/RS485 outputs. This mode is used for programming and maintenance access of downstream devices.

USB Data Tap Mode

When the USB Port is connected and the USB mode switch is set to TAP, the USB port can be used to monitor the output port traffic. This mode can be used for data communications troubleshooting.

Custom Industrial Serial Applications

The flexible SS20 platform can be the basis for custom industrial serial applications including:

  • Protocol Conversion such as Modbus Protocol interfaces for specialized devices
  • Serial Communications Monitoring


The SCADALink SS20 is configured using the SS20 GUI Software connected via the USB port.






Features & Specs

Features & Specs

  • Class I Div 2 Certification
  • Integrated protocol analyzer
  • Galvanically isolated RS-485 output with selectable termination
  • Low power draw
  • Compact size
  • DIN Rail Mounting
  • Easy configuration via included software
  • USB connectivity for modern computers lacking RS-232 ports
  • Multiplexing of Modbus RTU, Modbus ASCII, ROC, BSAP Protocols


Input Power10 to 30 VDC
Power Connector4 position Removable Terminal Block
Operating Temperature-40 to 70 °C
ApprovalsCSA Class I Div 2 Group C, D T3C
Suitable for use in Class I Zone 2, IIB T3C
Data Rate1200 to 115200 bps
RS-232 ConnectionsTx, Rx, GND, RTS
RS-232 Connector4 position Removable Terminal Block
RS-485 ConnectionsData A(-), Data B(+), Isolated GND
RS-485 Connector4 position Removable Terminal Block
Mounting35mm DIN-rail
Dimensions0.9″ (23 mm) L x 4.25″ (108 mm) W x 4.5″ (114 mm) H
Terminal BlocksType: 4 position pluggable/removable
Wire Size Accepted: 24AWG to 12AWG
Connection Method: Screw

More Details…



Modbus Multiplexer / SCADA Multiplexer

The SS20 enables 2 SCADA Masters to simultaneous communicate to a single PLC, RTU, or EFM.

This is a common need in Oil and Gas Industries.  One SCADA Host could the local field host; the other host could be a Cloud Host. Sometimes the two SCADA host could belong to separate companies; the well operator, and the well owner; the pipeline company and the well owner.

SS20 to Connect to Flow Computers and Smart Instruments with RS485 Connections

Use the SS20 to connect devices with RS485 connectivity to the SCADA host or Master RTU.  The SS20 has a USB port with override function which allows programming and maintenance access of device without connection of radio-modem or master RTU.

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Connectivity for Long Multidrop RS485 Runs, Multidrop EFM, and Smart Instruments

The SS20 with Isolated RS485 connectivity prevents grounding issues and protects plant equipment from lightning surges.

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Wellsite SCADA Installations, Multi-Well Pad Instrumentation, and Plant Instrumentation

Maintenance Access

The SS20 allows multiple masters to access devices multi-dropped in an RS485 network.  The 2nd host or LOI port may be used for maintenance software access used to configure, or diagnostic of smart instrumentation, flow computers, or analyzers.


Documentation & Software

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