Detecting AC vs. DC coupling would be obvious to a practicing EE, if presented with the problem, yes? I'm just a software guy with an electronics hobby and I think I could have figured that one out.

That said, DC vs. AC coupling detection could probably be granted a patent if nobody had "disclosed" the idea prior to filing of such a patent, based on my experience with software patents.

Sorry to vent, but patents on this sort of thing drive me crazy. I don't have any gripe with you or your post.