When the foot pedal is not depressed, the front stopper is in the UP position and the rear stopper is in the DOWN position (only front stopper is working).
When the foot pedal is depressed, the front stopper releases the front container and the rear stopper holds the next container (only rear stopper is working).
When the foot pedal is released, the rear stopper returns to the DOWN position and the container proceeds to the front stopper.