[ale] iTouch headphone detection

[Chris Fowler]

Last night I built a breakout cable for my iTouch with the purpose of
plugging the audio output of a HW-8 into the mic jack of the iTouch.
There is a program I want to use called iDSP.

What I need to know is how (hardware) does the iTouch detect a
microphone.  When you plug in the 4 conductor cable it does something to
see the mic.  I can plug in a real mic and it will detect it.  I can
then plug in the HW-8 and all works well.  It only does the detection
with the 4 conductor cable is attached.

Chris