Abstract: Piezoelectric user interface arrangement comprises a voltage converter for controllably generating voltage waveforms driving one or more piezoelectric elements. The voltage converter has a control input. A controller is coupled to said control input to control an output voltage of said voltage converter. The controller has one or more scaling inputs. The controller forms said control signals to make said output voltage follow a target waveform as a function of time. The controller is configured to scale said target waveform on the basis of scaling information received through said one or more scaling inputs.

Abstract: The present invention relates to an apparatus for detecting a state of an elevator door, the apparatus configured to: determine, on a basis of a pressure data, at least one indicator value indicative of a change in the pressure; compare the at least one indicator value to a respective reference value; and set, in accordance with a comparison between the at least one indicator value and the respective reference value, a detection result to express one of the following: (i) the elevator door is open, (ii) the elevator door is closed. Furthermore, the invention relates to a method, a computer program product and an elevator system.