I had a look around to see if I could find you a manual, but I had no luck. I did find some diagrams on the Nolan site that shows how things work. If the system has the functionality to mute your music if your phone is in use or if your passenger speaks then you can normally not use the wired MP3 connection without the actual comms device being on. This is because the comms device controls the playback from the wired MP3 connection to the speakers.
I wanted to have the same thing with my Scala Rider, but it turned out impossible because of the way it works.