I was in GuitarCenter yesterday and purchased a used "Schecter Diamond Series 004" and I had a couple small questions about it since I'm new to basses hardware and such. From what I could tell (And what I've found online so far) it's the 2003 version (Or at least the very newest there was before it was discontinued) Bolt on neck. On to my questions: First! What do each of the four knobs do? The salesmen wasn't able to answer that question at the time. Second! From what I found online the pickups are "Active/Passive" with the 9v battery in the back. I literally have no idea what this means. Does one of the knobs change it between active and passive mode or something? Or if I take the battery out will they become passive and won't need the battery? Any help on these two questions would be vastly appreciated. Thank you!