A minicomputer has a processor and a display unit and a communication unit and a haptic operating device. The haptic operating device has a rotatable rotating unit with a rotational resistance which can be changed by way of a control device. Selectable menu items are displayed on a display unit and a menu item is selected by rotating the rotating unit. A rotational resistance of the rotating unit is dynamically changed during a rotation of the rotating unit and the rotating unit is latched at a plurality of haptically perceptible latching points during the rotation of the rotating unit.

A hand-held power tool has a motor, a tool holder, and a percussion mechanism disposed between the motor and the tool holder in the drive train. The percussion mechanism includes a first shaft and a second shaft. A magnetically conductive ring gear is connected to the first shaft. An inner wall of the ring gear is eccentric to an axis of the second shaft. A magnetically conductive impeller is connected to the second shaft and is arranged to rotate within the ring gear. The impeller is spaced from the ring gear by a first air gap in a first position while being spaced from the ring gear by a second air gap in a second position, the first air gap being smaller than the second one. A magnet array is arranged coaxially to the second shaft. A magnetorheological fluid fills a cavity between the ring gear and the impeller.