aux function on the 2005 zx4 ses 6 cd mp3 player

What is the aux button for on the deluxe 6 cd mp3 player system in the 2005 Focus ZX4 SES? I can't find any audio input lines on the stereo, but it doesn't make sense to me that a manufacturer would put a button
on the radio that serves no purpose. Hopefully someone more familiar with the Focus audio options can resolve this issue. I searched this group for any discussions on this, and only found one thread from last year that appears to leave the issue unresolved.
Thanks,
Dan Pilloff
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.