In a piston for a compressor, the piston comprises a stem by which the piston may be guided in the housing in an axially displaceable manner, and a force introducing section where an outer drive force can be introduced into the piston. The automatic transmission control device, in an interval prior to a deceleration required interval, controls an automatic transmission so as to ease a shifting operation that corresponds to a decrease in the accelerator opening. A spring biases the pivot arm to rotate in a tensioning direction. The merchandiser also includes a controller in communication with the first and second product simulators.