Breitbandiger Frequenzverdoppler (Mit SO 42P)

The front-door bell or telephone cannot always be heard all over the house. Extending the bell usually means running wires all over the house, which is not a particularly elegant solution to the problem. However, the mains wiring already runs all over the house, so if this could be used there would be no need for additional cables. The circuit shown here makes use of this possibility.