Dock audio playback on sansa e200r

[John Brown]

Audio plays back on my sansa e200r dock but  not the other features of the dock (volume on dock itself that controls sansa volume). I read some were that the sansa dock specifications should not allow for dock features so my question is
How come audio plays though dock connection and not other features ?

[Llorean]

Because Audio probably simply uses the Line Out pin, which doesn't require special knowledge about the dock protocol or anything else, just how to enable line out.