Abstract: The invention concerns a sequential safety system associated with a moving closing panel driven so as to slide by an electric motor (6), this safety system including means (20) exploiting the signal originating from an optical fibre to stop and reverse the direction of movement of said moving panel in the event of a change in the signal, as well as additional safety means allowing the end-of-travel positions of the moving panel to be determined without ambiguity via the joint exploitation of the results derived from measuring the frequency of the pulses caused by the rotation of the electric motor (6) driving said moving panel, as well as data originating from the optical fibre.