Abstract: Disclosed is a switch housing having a cylindrically shaped cavity therein. An armature within the housing has a generally cylindrical shape and is movable with respect to the housing between two stable or quiescent positions. One end of the armature has a substantially hemispherical depression and forms, in combination with a matching depression in the base, a substantially spheroid portion of a chamber. Extending radially from the segment of the sphere within the base are two frusto-pyramidal depressions which extend downwardly to and in tangency with the spheroid segment in the base. Electrical conductors are adjacent the frusto ends of the pyramids and extend out of the base. Mercury is placed in the spheroid portion of the chamber. The armature has a collar of steel extending axially. A toroidal magnet is placed about the exterior of the cylindrical housing. A magnetically responsive keeper is secured to the housing top. The magnet is held by the metal keeper secured to the top of the housing.