This part of ISO 17458 specifies the electrical physical layer for FlexRay communications systems. The electrical physical layer for FlexRay is designed for time-triggered networks with data-rates up to 10 Mbit/s to connect automotive electronic control units (ECUs). The medium that is used is dual wires. Signalling on the bus is accomplished by asserting a differential voltage between those wires. Topology variations range from point-to-point connections via linear passive busses and passive stars up to active star topologies. This part of ISO 17458 includes the definition of electrical characteristics of the transmission itself and also documentation of basic functionality for bus driver (BD) and active star (AS) devices.