[ShaftedTwice]

Behind the faceplate of the car stereo, there is an odd-looking parallel port (best I can describe it), is there a way to hook this up to an external audio source, such as an MP3 player?

 

[Gino]

Modern head units have aux inputs for Ipods. Some JVCs have mini jacks up front. Older ones have adaptors which go into cd changer sockets in the head units. Alpine has these adaptors for their Ainet sockets. Pioneer would have adaptors (cd-rb20) for their ip-bus sockets.

Newer HUs can integrate Ipod controls in the head unit.