A switching device for switching a current between a first connection and a second connection including a series circuit of at least two JFETs, with further JFETs, which are connected in series to a lowest JFET, and wherein a wiring network for stabilizing the gate voltages of the JFETs is connected between the second connection and the first termination. An electromagnet is energizable to bias the shoe to one or other of the first and the second positions and a power supply is provided having a direct current source for supplying a direct current flow to energize the electromagnet. An observation module collects observation data relating to user behavior for each treatment.