An operator for controlling the movement of a window sash relative to a frame, including a base attachable to a frame; a linkage secured to the base and attachable to a window sash to control the movement of the window sash relative to a frame; a rotatable input shaft rotatably secured to the base and driveably engaging the arm, the input shaft having a female drive region formed therein; a drive member; a transmission shaft secured on one end to the drive member and having a male drive region disposable within and mateable with the input shaft female drive region to transfer rotation of the transmission shaft to the input shaft; and means for locking the transmission shaft to one of the base and the input shaft to hold the male drive region in mateable engagement with the female drive region.