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A novel unsymmetrical bistable mechanism with a parallel beam and three magnets arranged in the three-dimensional space is proposed, and the combined effect of the magnetic force and the mechanical force on the bistability of such a structure is analyzed based on the magnetic-charge model and the material mechanics theory. By employing the nonlinear combined force during the snap-through procedure to enhance the contact force, a novel fast response threshold acceleration switch with low contact resistance is designed and fabricated, which consists mainly of an inertial mass supported by two parallel elastic beams, one metal contact point, and three permanent magnets with one imbedded in the inertial mass and the other two fixed in the case along the vertical direction. The dynamic design model subjected to different shock pulses is proposed to optimize the design process, and the effect of the pulse shapes on the switch's sensing threshold and response time is investigated, and the simulation results show that the acceleration switch is closed in less than 9.0 ms after being triggered by the rectangular shock pulse of amplitude of 50.0 g, and also, the contact force is greater than 0.5 N, which can reduce the contact resistance to an acceptable value and guarantee the contact reliability. According to the working principle of the acceleration switch, a series of test benches are established to test the static and dynamic performance of the switch. The contact resistance is less than 1.9 Â¿ with a minimum resistance only 0.5 Â¿. The average threshold acceleration of the switch sample is 51.4 g with only 2.8% deviation from the design value of 50.0 g. Both the dynamic simulation results and experiments validate the feasibility of introducing permanent magnetic actuated bistable structures in designing the threshold acceleration switch.