operable in two or more distinct sets

Full Title

Special arrangements or measures in connection with doors or windows ( ; screening or similar protective devices E06B9/00) > for providing ventilation, e.g. through double windows; Arrangement of ventilation roses (airflow control members per se F24F13/08) > Louvre doors, windows or grilles > with rotatable lamellae > interconnected for concurrent movement > operable in two or more distinct sets