Abstract: The invention relates to an operator system for an aperture member, such as a window or a door, comprising a fixed frame and removable means such as a movable sash, said operator system being designed for operating said movable means associated with said aperture member, e.g. for opening and closing of said aperture. The invention further relates to an aperture member, such as a window or a door, comprising a fixed frame and movable means such as a movable sash, said aperture member comprising an operator system for operating said movable means associated with said aperture member, e.g. for opening and closing of said aperture. The components of the system are designed in a modular manner and arranged for installation in e.g. a window prior to installation of said window in e.g., a wall and after installation of e.g. a window, an operator system according to the invention may readily be made operational.