Ah - I was being a bit slow, although I would have been impressively fast if you'd typed 'RFC'Ring Final. Of the three circuits protected by the RCD, two are RF circuits.
Mind you, I don't really like 'RFC', because it could just as easily be 'Radial Final Circuit' (like the disused shower circuit!)!
Kind Regards, John.
Yes, but rather RFC than RF Circuit - a thing with tuned circuits, local oscillators. mixers etc. operating somewhat above 50Hz.