Sorry Everhelpful, but I'm not sure how they work. However we have two in our house, both linked to the sky system so we have sky in the conservatory and the master bedroom without having to pay the extra (very expensive) sky costs and they are brilliant. We can even change channels adjust colour / brightness / contrast / volume etc through them. Only drawback is you can only watch one channel at a time (they don't work like an extra sky box) but if you still have an aerial then you can still watch terrestial tv in one room and sky in another.