A functioning TB20 configuration will always require a bus coupler and at least one peripheral module.
The PROFINET bus coupler is designed to connect a PROFINET bus to TB20 peripheral modules. It can accommodate up to 63 modules of any kind connected in series with the bus coupler. The bus coupler supports hot-swapping for replacing modules during operation.
In addition, it will recognize all connected peripheral modules and assign each module the corresponding inputs/outputs from the process image table.
A functioning TB20 configuration will always require a bus coupler and at least one peripheral module.