Abstract: An actuating mechanism of a three-position switch, the switch comprising a main shaft supporting or actuating contacts and able to be moved selectively to three stable positions and a center crank which is pivotally mounted and can be actuated so as to take the three positions of the main shaft, the mechanism in addition having a mechanical system which produces a kinetic ratio between the angular movement of the center crank and that of the main shaft which increases when the center crank moves from the open position to the closed position, which results in the force transmitted to the electrical contacts increasing continuously as movement takes place from the open position to the closed position.