Process control interface system having triply redundant remote field units

A process control interface system (10) having a rietwork of distributed triply redundant input/output field computer units (12). The system includes a plurality of self-contained remotely located triply redundant field computer units (12) connected to decision making redundant process control computers (14) through a bi-directional communication network having at least two concurrently active communication channels (46, 48). Each of the field computer units include a set of at least three redundant field computers (92, 94, 96) for arbitrating both input and output signals. The field computer units also include individual abort circuits (510, 606) for each output signal to be transmitted to a device (84, 86) which affects the operation of the physical process. These abort circuits effectively enforce the output value signals arbitrated independently through each of the three redundant field computers using a voting procedure.