left or right without utilizing the data transmission system of the control room to the control logic 15 of each control unit is added monitoring logic 16 which takes over the security functions in the event of a failure of the minicomputer and ensures that the control data outputted by the control room of the right hand neighbor is passed on via the transmissions paths 23 and 24 the control arrangement according to fig2 differs from the one shown in fig1 essentially by the feature that 34 operation with control room 34 or 34 operation without control room 34 is preselected from the control room and that only the lines 23 and 24 are used for the cyclic call up of the control units a1 to an by the control room as well as for the data exchange of the control units with the respective adjacent control units if the control room fails for this purpose the control room contains a further transmitter 36 which is connected via a control line 30 to a receiver e6 in the control unit a1 which is directly connected to the control room transmitter 36 transmit the chosen mode of operation to the minicomputer 10 of the control unit a1 through receiver 6 the chosen mode of operation is.