Unused Tape/MD input

Hi, I've only had my 3 for a little over a week. I've read a lot of the posts here and seen some people trying to connect their MP3 players to their HU. I like the idea, but I don't like the idea of just injecting an audio signal into a signal wire already being used. I am an electrical engineer and there are a lot of problems with that scenario.

What I am wondering though, is I didn't get the Tape or MD option, but I still have the button on my dash control. There must be a way to use that unused audio input on the back of the headunit to accept line input from some other source. I hope to do some more research on this and maybe we can come up with some solutions. I just need to get ahold of some wiring diagrams and electrical information on this car.

if you use the p.i.e. unit, it attaches to the 16 pin connector on the back of the stock adio and makes it an aux in... as seen here... http://www.mazda3forums.com/viewtopic.php?t=8831 (mj)

Awesome. Thanks for the link. But I was actually wondering if there was a way to interface with the black connector shown on the underside the 6 disc changer as shown in one of the pics on that link. That would allow you to use the Tape/MD button, I'm guessing. I'll keep looking. Thanks a bunch for that link!