Fieldbus is a digital serial, multidrop, data bus for communication with low-level industrial control and instrumentation devices such as transducers, actuators and local controllers. The Physical Layer provides for transparent transmission of Data Link Layer entities across physical connections. Specifies the requirements for Fieldbus component parts. Also specifies the media and network configuration requirements necessary to ensure agreed levels of: a) data integrity before Data Link error checking; b) interoperability between devices at the Physical Layer. The contents of the corrigendum of July 2004 have been included in this copy.