Abstract: The invention relates to a method and a device for conditioning electric installations in buildings for the rapid transmission of data. A frequency range of between 1 MHz and up to more than 30 MHz is designated for rapid data transmission via power supply systems. In known methods of signal coupling, installation power supply systems in buildings act as electromagnetically open structures with a negligible shielding effect and a high degree of asymmetry. This leads to poor transmission quality and to problems of electromagnetic compatability, meaning that only a fraction of the available channel capacity can be used. The aim of the novel conditioning method for power supply systems is to produce symmetrical transmission paths, along which high frequency signals can be transmitted with substantially no interference, using low-level emission.