A dispenser for mixing and dispensing a liquid chemical concentrate from a container with a stream of diluting water. In some embodiments, a token is issued by one or more remote media servers that allows the client device to download video, media or other data from one or more remote media servers. The user sits on the second platform and rests their legs on the first platform in various positions. The switching function is defined as a linear function of a deviation between the output of the plant and a control target value.