I think the automatic input selection is the same on Mojo and Mojo 2, which means that the inputs are checked/selected in order of priority.
USB has priority 1, and is selected by default if Mojo 2 detects 5V on the VBUS pin of the plug/socket.
This is partly explained in this post for the Mojo
- When you have both USB and Toslink plugged in (and switched on at the source) your Mojo 2 is detecting the 5V VBUS and selecting the input from your PC, even if your Streamer is switched on.
- When you unplug the USB cable (or alternatively switch your PC off), the 5V on the VBUS disappears, so the Mojo 2 will next check and use your Toslink input.
I'm not sure I completely understand. I get the priority thing, and the manual states that selection of inputs should be automatic, depending on where the signal is coming from.
"Mojo 2 will auto-select the correct input when music is played to the device. Mojo 2 will prioritise specific inputs if all four are connected simultaneously. USB has priority followed by coaxial and then optical. It is only possible to connect one USB at a time (Micro-USB takes priority over USB-C)."