A method for forming a bevel cut at an end of a wood member is disclosed. Each electrode comprises a skin-contacting gel layer, a current-spreading layer, and an adhesive layer for adhering the electrode to the patient. The group IV substrate contains a p-n junction whose change of characteristics during epitaxial growth of As-containing layers is minimized by the AlAs nucleating layer. The second control unit is powered in an isolated manner from the input voltage, conveniently via a transformer constituting the signal coupler.