Abstract: A system for sensing a media stack to detect a given stack height includes a stack site in an output bin and a mechanical flag mounted adjacent to a side thereof in a counterbalanced state at a home position where an exposed portion of the flag extends into a media sheet delivery path where it is struck by an edge of repetitive media sheets moving to the site. The striking of the exposed portion by the sheet edge causes the flag to deflect to a displaced position outside of the delivery path, allowing the sheet to land on the site increasing the height of a media sheet stack at the site. The counterbalanced state further allows the flag to return to the home position with its exposed portion in the media path until a given stack height is reached where the stack blocks further return of the flag indicating that the output bin is full.