My wife asked that the switched outlet in the loft be dimmable for a floor lamp. Knowing I could not just install a dimmer switch in lieu of the toggle switch and feed a standard 15A receptacle with dimmed power I did a little code research and came up with this. A dimming receptacle. The name is a little misleading as the receptacle does not actually do the dimming but is approved for the application with modifications to it in conjunction with the special plug. Notice the undersized slot on the hot side of the receptacle and the "nub" in the center. I usually install the switched half of on outlet to be on the bottom to facilitate plugging in a vacuum or other device and this outlet has it on the top. Interesting. Learn something every day.