Fieldbus is an all-digital, serial, two-way communications protocol (HS1)that standardizes the interconnection of field devices at a communications rate of 31.25 kB/s.

The field devices are made accessible to communication networks (running at 1 or 2.5 Mb/s), through use of linking devices. Because a simple twisted pair of wires can carry the signals between the field devices and the networks, Fieldbus users can reduce the amount of I/O and control equipment (due to distribution of control into the field devices), plus they can use fewer intrinsically safe (IS) barriers, cabinets, cables and connectors.

And, since the pair wire can support multiple functions within a single device (such as diagnostics, control and auto error correction), the twisted pair cable becomes the integral part of a more efficient, more reliable, and

more cost-effective industrial control system.