The invention relates to a switch for an electrical device, in particular for an electrical tool, comprising a slide control for setting a rotational speed of the electrical device, a switch housing, and at least one circuit board arranged in the switch housing for holding electrical components of the slide control. According to the invention, a movably supported operating element of the slide control is inserted into a contact chamber of the switch housing in a sealed manner through a first feed-through and is led out of the contact chamber in a sealed manner through a second feed-through in all adjustment positions of the operating element. Thus, a switch that ensures reliable function even under ambient conditions of high contamination is provided.