An electric switch of the normally closed type has a housing including a lower part that supports a fixed contact track, an internal contact blade that is resiliently deformable in order to assume a bottom rest position in order to establish an electric switching way, a first high non-stable position, in which the switching track is interrupted, and a second high stable position, in which the electric switching track is interrupted and in which the internal contact blade is locked such as by retractable locking structure, and an actuator to control the deformations of the internal contact blade.