an apparatus and a method for transferring data and energy over network units of a defined network . the apparatus has at least two units , a bus coupling the units with a receive line and a transmit line and a bus control device coupled with the bus , the bus control device having first means for controlling the transfer of data defined by the defined network as data voltage signals over the transmit line and over the receive line , second means for charging the data voltage signals on the transmit line with first supply voltage signals adapted for voltage supply of units of a first plane system , and third means for charging the data voltage signals on the receive line with second supply voltage signals adapted for voltage supply of units of a second plane system .