<https://hako-lehrmittel.de/en/produktkatalog/operating-brake-valve-1/>
<http://schema.org/description>
"Demonstration:  movement of the graduating and control piston  opening and closing the inlet and outlet  release, partial braking and full braking position"
<https://hako-lehrmittel.de/en/produktkatalog/operating-brake-valve-1/>