Abstract: A control system for a printing press in which a central computer is interfaced to a plurality of printing units through peripheral units located near the press units. The central unit utilizes digital signals to address particular peripheral units and to select control functions at the selected peripheral unit. The controlled functions in the press units provide analog feedback signals which are to be sensed by the central computer. A multi-function bus comprising both analog and digital sections couples the central computer to the peripheral units. The integrity of the analog feedback signals on the bus is maintained by assuring that the digital signals on the bus are maintained in a quasi-steady condition during intervals when the central computer is evaluating analog feedback signals on the analog section of the bus.