Abstract: A device adapted to respond to a mechanical shock as in an earthquake or the like, and including a first movable element to be controlled, a second element which normally blocks movement of the first element but is displaceable by shock-induced movement of a weight to permit movement of the first element, together with resetting mechanism operable to move the first element back toward its initial position and operable also to deflect the second element laterally back to an active position again blocking movement of the first element from its normal setting. The weight is preferably supported by a universal connection including a ball and socket joint in which the ball has an upper truncated portion defining a surface engageable with a movable part in a manner shifting that part axially in response to shock-induced pivotal movement of the weight structure.