TB20 Bus coupler, Modbus/TCP

The Modbus/TCP bus coupler makes it possible to access data from peripheral modules using the Modbus/TCP protocol, but can accommodate up to 64 modules of any kind connected in series with the bus coupler.
The Modbus/TCP bus coupler features an integrated two-port switch that allows for star and line topology configurations.
A large I/O image table size of 2 kbytes makes it possible to implement comprehensive and complex systems.
The control and status registers can be used to configure and monitor the coupler’s behavior with Modbus/TCP.
TB20 ToolBox can be used to easily configure the system structure and the various module parameters, and transfer the corresponding settings to the coupler.

A functioning TB20 configuration will always require a bus coupler and at least one peripheral module. The bus coupler supports hot-swapping for replacing modules during operation.

  • Modules can be replaced during operation (hot-swapping)
  • 24 V DC power supply
  • Integrated power supply unit for powering peripheral modules (2.5 A)
  • Supplies the system’s I/O voltage (24 VDC)
  • USB device port for online diagnostics, configuring parameters, setup, and firmware updates with TB20 ToolBox
  • TB20 ToolBox simulation for commissioning the I/O system without a higher-level controller in order to test the system's operation (I/O check)
  • Concealed "factory reset" switch for restoring the module to its factory settings
  • Simultaneous access to up to 10 stations (TCP connections)
  • The coupler's behavior can be configured using control registers
  • The coupler's status can be read out using status registers
Dimensions (DxWxH)110 x 35 x 73 mm
WeightApprox. 115 g
Supports Modbus function codes1, 2, 3, 4, 5, 6, 15, 16, 22, 23
TCP connection10 stations
Voltage supply24 V DC, 18–30 V DC
Current drawMax. 250 mA with DC 24 V



TB20 Modbus/TCP Coupler600-170-1AA11