This item's description can be found on the Roco website as follows:
This feedback module is the basis for all automatic functions to be controlled by a computer (with relevant control software): It has eight galvanically separated outputs with screw terminals, to which momentary or permanent contacts can be connected.
If a contact is activated, the corresponding LED lights up. The feedback module is connected to the z21®/Z21® interface with the cable included and power is also supplied via this cable.
A total of 16 feedback modules can be connected to the interface.