Field bus is the name of a family of industrial computer network protocols used for real-time distributed control, now standardized as IEC 61158.A Field bus is a digital, bidirectional, multi-drop, serial-bus communication network.Replaces the existing 4-20 mA analog signal standard.It specifies the way to connect instruments in a manufacturing plant.It works on a network structure which typically allows daisychain, star, ring, branch, and tree network topologies.

It links the PLCs to the components which actually do the work such as sensors, actuators, electric motors, console lights, switches, valves, and contactors.