A water supply system has its housing and pressure tank sized so that the pressure tank fits within the housing, thus avoiding the need for another separate opening in the ground for the pressure tank. The chassis has an opening, and comprises a rear panel in which a hole is defined. The beam reflected from the outer surface of the protective window under the angle of reflection corresponding to the angle of incidence is conducted through an aperture stop onto a first light-sensitive detector so as to record the intensity of the reflected beam. Further, the polypeptides can be used as a vaccine to treat or prevent HEV. Advantages of the invention are: a less complicated construction and a saving of costs, a more compact design with smaller flue cross section area and thereby smaller self-inductance of the impulse circuit as well as easier production, transportability and handling because of stacked modules each with at least one generator stage.