Abstract: The device comprises two pick-up elements which can cooperate independently with a transmission line for control signals and are aligned in the direction of movement of a conveyor unit so as to be positioned respectively upstream and downstream in the direction of movement of the conveyor unit. The two pick-up elements are separated by a distance such that, during traversal of the gaps between successive sections of the line, at least one of the two pick-up elements is able to receive signals from the transmission line. A signal treatment circuit generates selectively an output control signal corresponding either to the single signal received by the two pick-up elements or to the control signal received by the pick-up element in the position upstream relative to the direction of movement of the conveyor unit when the pick-up elements receive different signals.