The invention relates two lines each with two terminals. A first line provides a first terminal and a second terminal. A second line provides a first terminal and a second terminal. The lines extend in spatial proximity and are coupled. The two lines transport an electromagnetic signal fed into the line system. Distanced from the first terminal of the second line and distanced from the second terminal of the second line, at least one controllable element is arranged along the second line. The invention further relates to a switch, a controllable diplexer, a controllable frequency filter, a controllable attenuator and a controllable phase shifter.