1. A DEVICE OF THE CHARACTER DESCRIBED COMPRISING THE COMBINATION OF AN ELONGATE HOUSING, END PLATES FOR CLOSING OPPOSITE ENDS OF SAID HOUSING, ELECTRICAL CONTACT MEANS MOUNTED ON EACH END PLATE WITHIN SAID HOUSING, A GUIDE SHAFT EXTENDING BETWEEN AND SUPPORTEWD IN THE HOUSING BY SAID END PLATES; A BALL BUSHING ENCIRCLING SAID SHAFT AND MOVABLE THEREUPON, AN ANNULAR ACCELERATION RESPONSIVE MASS HAVING CENTRALLY DISPOSED RECESSES IN OPPOSITE ENDS THEREOF SURROUNDING SAID SHAFT AND AFFIXED TO SAID BUSHING A SHORTING RING DISPOSED IN EACH OF SAID RECESSES, MEANS SECURING SAID RINGS TO SAID MASS AND INSULATING THEM THEREFROM, A SELECTIVELY SETTABLE ADJUSTING RING CARRIED BY SAID HOUSING, AND HELICAL COMPRESSION SPRING MEANS ENCIRCLING SAID MASS AND DISPOSED BETWEEN ONE END OF SAID SETTABLE ADJUSTING RING AND A PORTION OF SAID MASS FOR CONTINUOUSLY