The Mercedes driving system

The movie shows the disengagement of the numeral wheels. The intermediate gears are in a vertical position when the toothed racks go forward, then the toothed racks are engaged with the numeral wheels. When the toothed racks go backward, they are disengaged and the numeral wheels stay at rest. The gears that are under the revolving bar are always engaged with the toothed racks, this explains there clockwise and counterclockwise rotation.