Patent ID: 7684167

Claim:
A communication bus suitable for use in a hazardous area of a process plant to transmit electrical signals from one process device to a second and different process device disposed within the process plant and to interrupt the transmission of electrical signals in response to the detection of a fault condition in the communication bus, the communication bus comprising: a first end to connect to the one process device; a second end to connect to the second and different process device; a first transmission path between the first end and the second end that communicates electrical signals in a first direction between the first end and the second end; a second transmission path between the first end and the second end that communicates electrical signals in a second direction between the first end and the second end; and a safety device coupled to each of the first and second transmission paths between the first and second ends, wherein the safety device includes a first control unit to detect a fault condition associated with the communication bus, and wherein the safety device further includes a first switch unit connected to the first and second transmission paths and having a closed position allowing a flow of electrical signals along the first and second transmission paths and an open position preventing the flow of electrical signals along the first and second transmission paths, and wherein the first control unit causes the first switch unit to move to the open position to interrupt the flow of electrical signals between the first and second ends along each of the first and second transmission paths in response to detecting a fault condition in the communication bus at the first control unit, wherein the first control unit does not use the first and second transmission paths to detect the fault condition in the communication bus.