Tried searching but couldn't find.

I have an Eclipse CD8454 (unfortunately no manual).

Tried using the optional AUX adapter that plugs into the CD changer port. How do I toggle to the source?

I tried holding down the "disc" button for a few seconds, but that takes me to the direct AUX input of the HU, and not the adapter cable. Is there a way to activate the CD Changer AUX adapter?

Thanks in advance.