A device for conveying piece goods. The electronic control includes control logic which generates an operation fault indication signal based on the application of predetermined criteria to operation conditions, with concomitant display of data indicative of the operation fault indication signal accompanied by inhibiting or altering raising or lowering of the lift. A microphone is positioned adjacent an edge of the acoustic driver. A plurality of sensors detects light reflected back from a bar code and generates a plurality of electrical signals proportional to the intensity of the reflected light. Thus, the memory controller implements a first set of rule in the coherent mode of operation to insure that all copies of data stored by the agents are coherent with data stored in the memory.