Cannot Hear Line-In Device through S/PDIF

Like the title says. Any ideas as to why this is? I've tried both optical and coaxial outputs, no dice. I am trying to connect a radio scanner for some ACARS and data decoding via soundcard but I also want to hear it through my receiver. I can hear any line-in device through my headphones via the front/rear headphone outputs just fine.

Edit: Whoops, I guess this should have gone in the sound section, oh well.