Lets do a comparison, first the unit and manual I was reading, trying to troubleshoot my audio issue. (Prefix Y or Higher)
Now lets take a look at the actual unit I have in the plane. (Prefix X or Lower)
Look at the labels below the switches TEL-AUX-MUTE-SPR. With MY unit I have to push a combination of TEL and one of the remaining three Functions A,B,or C.
I'll be back out to the plane tomorrow to give it another try from the PAX headset jacks, and try the additional jack in the center console. I'm even going to try the iPod for music input, along with setting up the music control preferences.