[57] Monitoring device for a lift, which comprises at least one contactlessly actuable switching device (1), which comprises an active unit (2) and a passive unit (3), wherein the active unit and the passive unit are so constructed that the passive unit is excited exclusively by a pattern (M) generated by the active unit, wherein the passive unit is excited by the pattern of the active unit from a defined spacing between the active and passive units and generates an answer (M'), wherein the answer is transmissible as identification signal to the control unit, characterized in that several switching devices and a central checking unit are provided which are serially connected together via a bus into a safety chain and that the pattern and the answer are numbers which can be represented by a bit pattern / bit sequence.
