TB20-C, Bus coupler

TB20-C, Buskoppler ModbusTCPTB20-C, Buskoppler ModbusTCP Front
TB20-C, Buskoppler ModbusTCP
TB20-C, Buskoppler ModbusTCP Front


The ModbusTCP bus coupler makes it possible to access data from peripheral modules using the ModbusTCP protocol, but can accommodate up to 64 modules of any kind connected in series with the bus coupler.
The ModbusTCP 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 ModbusTCP.
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.

Note: Individual modules cannot be combined with the IO systems of other manufacturers.

  • 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 functionality (I/O check)
  • Concealed "factory reset" switch for restoring the module to its factory settings
  • Connection watchdog for connection monitoring
  • Simultaneous access to up to 10 stations (TCP connections)
  • Integrated two-port switch
  • Up to 64 peripheral modules
  • 2 x RJ45 connections
  • 2048 bytes of input, 2048 bytes of output data
  • 126 bytes of parameter data per module
  • The coupler's behavior can be configured using control registers
  • The coupler's status can be read out using status registers
  • 7 LEDs, one of them bi-color
Download PDF datasheet
General information
Order number600-170-1AA11
Article nameTB20-C, ModbusTCP bus coupler
Scope of deliveryBus coupler ModbusTCP, 24 V power supply connector, bus cover element, base module
Dimensions (DxWxH)73 x 35 x 110 mm
WeightApprox. 115 g
ModbusTCP interface
Transmission rate10/100 Mbps, automatic detection
I/O image size2048/2048 bytes
Parameters per module126 bytes
integrated switchYes
Supports Modbus function codes1, 2, 3, 4, 5, 6, 15, 16, 22, 23
TCP connection10 stations
USB interface
ProtocolFull-speed USB 1.1 device
Isolation voltage1.5 kV
Electrical isolationYes
Number of modules that can be connected in series64
Voltage supply24 VDC, 18–28 VDC
Current draw
Current draw without modules (internal)75 mA
Power supply for modules5 V DC, max 2.5 A
Power dissipationMax. 8 W
Permissible cable cross-sectionAWG 16 .. 22
Mounting positionAny
Ambient conditions
Ambient temperature0 °C … +60 °C
Transport and storage temperature-20 °C … +80 °C
Relative air humidity95 % r H without condensation
Protection ratingIP 20
CertificationsCE, UL
Surrounding Air Temperature0 °C … +50 °C
Pollution degree2
Noise immunityDIN EN 61000-6-2 “EMC Immunity”
Interference emissionDIN EN 61000-6-4 “EMC Emission”
Vibration and shock resistanceDIN EN 60068-2-6:2008 „Vibration“, DIN EN 60068-2-27:2010 „Shock"

Technical Documentation

TB20 – ModbusTCP Koppler, Manual 3 7 MB
EU Declaration of Confirmity 04-2020 55 KBEU Declaration of Confirmity


Flyer, TB20 IO-system for numerous applications 08-2022 6 MBTB20 IO-system for numerous applications


TB20-ToolBox V2 Setup V2.10.008 29 MB History TB20-ToolBox, TB20, Toolbox


TB20, USB Driver 1.20 7 KBTB20, USB Driver

Planning Tools

TB20, Macros for EPLAN Electric P8* from V2.0 in EDZ format 07.02.2018 84 MB
TB20, STEP files 1.00 8 MB
TB20-C, Buskoppler ModbusTCP, STEP Files 3 MBTB20-C, Buskoppler ModbusTCP, STEP Files

The 24 V power supply connector, the bus cover element, and the base module are included as standard.

“TB20 ToolBox” makes it easy to plan the system. Integrated terminal mapping, system width calculations, and current-carrying capacity monitoring all make it possible to quickly design systems without making any mistakes.