We bought the set with a transmitter and a receiver for my father. He has his own room 2 floors below our bedroom. In between are 2 reinforced concrete slabs. Too much for the normal transmission power of the original sets. We have the repeater installed halfway in the stairwell. Now it funzt as it should. Although all in all not a cheap pleasure, but at least you can rely on. And then also justifies the price.
