An interface module for use in a process monitoring and control system has an Ethernet port, a controller, and at least one segment I/O module. The Ethernet port is adapted to send and receive signals in an Ethernet protocol over a cable comprising a plurality of wires and to receive a voltage potential from at least one pair of the plurality of wires. The controller is coupled to the Ethernet port and powered from the received voltage potential. The at least one segment I/O module is coupled to the controller and is adapted to couple to an associated field device segment with at least one attached field device. The at least one segment I/O module is adapted to interact with the at least one attached field device on the associated field device segment.