Keyed on shaft 1 is ratchet wheel 2 which engages pawl 3. Pawl 3 turns about axis A of drum 4. Shaft 1 can rotate freely clockwise because pawl 3 slides over the ratchet teeth. If shaft 1 begins to rotate counterclockwise, it is braked by band 6 running over drum 4 and having its ends pivoted to lever 5.
$1980$FL,Br$