This is where you configure the interface to communicate with one or more Modbus masters. You can select the type of packet to be sent and the type of connection, which may be either serial or socket. Further properties of the selected interface, such as the port, or line speed, can also be edited here.

You may also configure the slaves you want to respond to the master(s) when you are connected.

To navigate to these settings, type Ctrl-W to bring up the Edit Settings... dialog, then with the Interface tab selected, click on the subpanel title under Edit Interface to Master.