The invention relates to an apparatus (1) for monitoring the state of a protective device (2) of a machine (4), in particular a safety switch for monitoring the closed state of a protective door or the like, wherein the apparatus (1) has a switch housing (22) with a switch head (24) and an actuator (8), which in the closed state of the protective device (2) interacts with the switch head (24) and, as a result, the closed state of the protective device (2) can be signalled, and wherein the apparatus (1) has a tumbler device (20) with a tumbler element (30), which is mounted movably in the apparatus (1) and by means of which the closed state of the protective device (2) can be locked releasably, characterized in that the tumbler device (20) has at least one permanent magnet (34), by means of whose magnetic force the tumbler element (30) can be fixed in a first position when the power supply to the apparatus (1) is switched off, in which first position the tumbler device (20) locks the closed state of the protective device (2), and/or can be fixed in a second position, in which the tumbler device (20) does not lock the closed state of the protective device (2).