Earthquake detection system with pendulum switch

An earthquake alert and fire prevention system comprising a pendulum-actuated switch in series with a relay controlling parallel circuits to an alarm and a house, said relay, in response to the closure of said pendulum switch, being movable from a first position wherein said alarm is inoperative and the house circuit is operative to a second position wherein the alarm circuit is operative and the house circuit inoperative, in further combination with holding circuit means in parallel with said pendulum-actuated switch wherein said switch comprises a base affixed to a rigid support having an enveloping hood, further including an electrically conducting ring electrically connected to said relay mounted on and electrically insulated from said base and further including a pendulum support affixed to said base and extending thereabove having a pendulum disc suspended by a wire conductor therefrom concentrically within said ring, said pendulum having an electrically conducting peripheral annulus electrically connected to said relay via said wire normally spaced from and disposed within said ring, including an additional mass suspended between said support and disc.