Abstract: A control and monitoring system for cigarette packaging machines comprises a control station (1) connected in cascade to each of a plurality of remote stations (2 and 3) in turn, in a ring. The control station 1 supplies an interrogation signal to a D-type latch (20, 30) of the first remote station, which changes state on the next clock pulse edge and applies an interrogation signal to the D-type latch of the second remote station so that the stations are sequentially interrogated in essentially non-overlapping time periods. An interrogated station communicates with the control center (1) via an information line (16) either to receive machine control signals to be passed on to a machine or machine part with which the remote station is associated, or to send machine fault signals indicating a fault in the associated machine or machine part.