The invention relates to a method and a device which reduces the phase space volume of ions in an ion beam in such a way that their injection into a downstream time-of-flight mass spectrometer optimizes the performance of that spectrometer. A plurality of prop lugs are formed on the underside of the lid and aligned with a rear edge banding which forms a fulcrum support for the prop lugs when the lid is in an intermediate open position. Firstly, first clock signals are provided in parallel in response to a first clock signal transferred from a motherboard. In the case of a fault in the region of one of the shaft doors, the controller permits operation of the elevator car between those floors that can be reached by the elevator car without having to pass the floor at the shaft door where the fault has occurred. An antenna may be configured to transmit the filtered multicarrier transmit signal. If the rise is not a normal one, an electronic control unit judges that a coil failure has occurred.