Abstract: The interior of a rheostatic device, such as a throttle-valve position potiometer having a rotor with sliding spring contact and a housing exposing at least one end of the rotor for operation, is sealed off against environmental effects by at least two hollow cylindrical rotor walls which are located concentrically within each other and extend towards a lid attached to a bottom part of the housing and at least two hollow cylindrical walls of said lid which are concentrically disposed within each other and extend between the rotor walls.

Abstract: In a switch, for example, for a device such as a drill, a key switches an ectrical switching bridge at the beginning of the key displacement. A variable resistor is adjusted depending on the travel of the key, thereby controlling device speed. In order to achieve an adjustment of the key end stop, a slide displaceable in the transverse direction is mounted on the key, which slide has a stop edge projecting in the longitudinal direction. A stop border is provided on the switch cover and configured relative to the travel of the slide so that the distance between the stop edge and the stop border varies according to the displaced position of the slide, thereby enabling operator control of the device speed.