Three identical pulleys 3 rotate about axes A of board 1. Flexible link 2 runs over the upper left and the right pulleys 3, and is attached at points B and C to, the base. Flexible link 4 runs over the lower left and the right pulleys 3, and is attached at points E and D to the base: Board 1 can be raised or lowered with translational motion along axis y-y.
$3547$CFL,ML$