Ray, that's interesting. Thanks for the reply. I have a 25' travel trailer, not nearly as sophisticated as your rig. Although, it's possible that there's a hidden outlet, it's not likely. I just tested both the line and the load terminals on the back of the outlet, and they are both getting 120 v. So, if I interpret that correctly, the outlet itself is functioning properly. Cancel trip to Home Depot. All of my outlets have a sticker that says GFCI protected outlet, so it seems they should all be on the same circuit, since only one has the test/reset buttons.