Fieldbus is a generic term describing any means of networking digital devices into a system of such devices, usually with the devices spaced over a wide area. There are at present several commercial fieldbuses to meet this requirement. Profibus, FF, WorldFIP, CANopen, LonWorks, DeviceNet and more recently Ethernet has taken a role in this arena. New technologies are bringing more options, particularly with radio networking.

They are effective as means of networking but the Standards that have arisen around each one is exclusive to its own means of communication.

R&D and other costs are such that manufacturers are unwilling to commit to any one fieldbus for fear of choosing the wrong one. Since the communications technologies are still evolving and will continue to do so, this has been wise. But as far as the development and use of Smart devices is concerned, it is has been unfortunate because, in consequence, most devices are still being manufactured with analogue signaling.

The feature of the fieldbuses that lies at the core of this problem is the fact that the messaging protocols are built into the communication protocols, and by so doing lock the design of a particular device into one or another means of communication.