This is unused, in the box. I bought it, it was installed by a certified technician, tested and worked but it wasn't actually the problem after all. So he removed it immediately and I put it back in the box. Carrier will not take back electronic components, so I'm offering it at a steep discount.
If you need it, you already know what it is and you'll save a couple hundred bucks. If you don't know what it is, you don't need it.