In trucks, a cord mounted on the ceiling of the operator's cab is pulled or in buses, a valve lever on the side of the dashboard is pushed down or pulled up to open the valve, supplying varying amounts of air to the horn. Thus, an outstretched hand reaching upward and pumping is a signal to the driver of an air horn equipped vehicle, requesting a toot. In modern trucks and buses, the horn is actuated by a button on the steering wheel (just like a normal car horn).