Sony cdx-c490 Auxilary input

[Craig]

I have an old Sony cdx-c490 headunit that has rca audio inputs as well
as a changer control plug on the back. I want to hook the audio
output of a Delphi Roady to the Sony. Does any one know/remember how
to wire the changer plug so it thinks it has a changer attached? Just
sending audio alone to the inputs does not trigger the headunit's
auxilary source input.

Thanks,
Craig