I bought a townhouse in Northern Virginia that was built in 1987. Behind my couch there is a strange outlet of some kind. It is 2 round prongs sticking out of the face plate. There is a "cap" that goes over the prongs that sayd "Slater" (symbol looks like a >). I have searched the web and found a Slater Electric, Inc. that was bought by Pass & Seymour in the late 1980s. I was hoping any electricians could shed some light on my mystery!