Abstract: A turnstile mechanism comprising a rotatable hub adapted to be driven by a person using a turnstile, the hub being connected to (or incorporating) a disc formed with a number of stop surfaces which are engageable by a stop member which is movable between a first position clear of the path of the stop surfaces and a second position lying in the path of the stop surfaces, the stop member being connected to control means which are operable to hold the stop member against a bias in either the first or second position, the control means being activated to change the position of the stop member from the first position to the second position when the hub has been rotated through a predetermined angle.