Abstract: An operating mechanism for a blind or shielding device having angularly adjustable and retractable slats 12, said mechanism comprising a first driven element 27 for pivotally adjusting the angular orientation of the slats and a second driven element 30 for transversely moving the slats towards and away from the retracted position, a common actuating member 22 for driving said first and second driven elements, a coupling device 24 directly coupling said first driven element to said common actuating member, a final engagement and lost motion mechanism 28, 30 for releasibly engaging said common actuating member to said second driven element and allowing entraining of said second driven element after a predetermined number of revolutions of said actuating member neither of two different rotational senses, the final engagement associated with said lost motion mechanism in each rotational sense inducing a reactive force in an axial direction, said reactive force assisting in declutching of said coupling device.