The FlexRay communications system is an automotive focused high speed network. Some of the basic characteristics of the FlexRay protocol are synchronous and asynchronous frame transfer, guaranteed frame latency and jitter during synchronous transfer, prioritization of frames during asynchronous transfer, single or multi-master clock synchronization, time synchronization across multiple networks, error detection and signalling, and scalable fault tolerance. The FlexRay communications system is defined for advanced automotive control applications. It serves as a communication infrastructure for future generation high-speed control applications in vehicles by providing: - A message exchange service that provides deterministic cycle based message transport; - Synchronization service that provides a common time base to all nodes; - Start-up service that provides an autonomous start-up procedure; - Error management service that provides error handling and error signalling; - Wakeup service that addresses the power management needs; 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.