Inertial switch

1. An inertial switch comprising a cylinder, a cap secured to one end of said cylinder, said cap having a central bore therethrough running parallel to said cylinder and a transverse hole communicating with said bore a wire inserted in the hole in said cap; a shearing member mounted in the bore, having a hole in which said wire is inserted and having a portion extending into the interior of said cylinder; a coil spring located within said cylinder having one end contacting said cap; a base secured to the other end of said cylinder; and a piston contacting said spring and base and having an elongated central portion; said spring being relatively long compared to the length required to stop the elongated portion of said piston from striking the portion of said shearing member extending into the interior of said cylinder when the switch is dropped from a distance of 40 feet onto a steel plate, whereby said wire is broken only when a predetermined sufficient energy is imparted to said spring.