For a device for the detection of substrates stacked at an opening of a wall element, there existed the problem of constructing the detection device in such a way that the detection of the position of the substrates can be performed more flexibly with respect to the course of measurement and the measuring method employed and a defined approach of a sensor system to the semiconductor substrate to be detected is ensured in a definite position of measurement with a lowered risk of particle generation. A transmitting and receiving device (11) consists of a vertical drive mechanism (10) mounted on the wall element (1) and a sensor head (13) that can be adjusted between a lower and an upper position by means of the vertical drive mechanism (10), said sensor head being arranged so as to pivot on the vertical drive mechanism (10) in order to pivot into the opening (4). The device finds application, in particular, in the semiconductor industry for recording the state of occupancy of cassettes or containers with substrates, such as semiconductor wafers, flat-screen displays, or masks.