Abstract: A motor-vehicle seat adjuster has a sun gear with which at least one planet gear is in continuous mesh. A link has an outer end carrying this planet gear and an inner end pivoted at the axis of the sun gear to allow pivoting of the planet gear between two angularly offset positions in each of which is meshes with a respective output gear. A control element is provided for displacing this gear between these two positions and the sun gear is rotated from an electrical motor. When the planet gear is in mesh with one of the output gears it displaces the seat in one direction and when in mesh with the other output gear it displaces it in another different direction.