If I understand correctly, the hinged disconnector attached to the tripping lever lifted the hinged trigger bar extension to disengage the trigger when the selector was set to repetition. When the selector was moved to automatic, the cam would push the disconnector back, keeping the disconnector from lifting the trigger bar extension.
The hinged trigger bar extension would reposition the tripping lever when the selector was in repetition. But what repositioned the tripping lever when the selector was in automatic? There must also be a spring of some sort to reposition the tripping lever each time the breech block passes? Have you seen one?
It's a very good book. Aside from the fantastic documentation, it's a joy to read.