Seismic movement detector responsive in both vertical and horizontal planes

A warning device for detecting occurrence of seismic movements, comprising:

• a first pair of electric contacts, one of said contacts of said first pair being vibratile relative to a generally horizontal rest position, the other contact of said first pair being adjustably spaceable from said rest position;
• a second pair of electric contacts, in which one of said contacts of said second pair is vibratile relative to a generally vertical rest position, the other contact of said second pair being adjustably spaceable from said rest position;
• an electric circuit connected to both said pairs of electric contacts, said circuit being closed when a vibration of sufficient amplitude imparted by an earthquake to the vibratile contact of at least one of said pairs causes it to touch its corresponding adjustable contact;
• and
• at least one warning unit inserted into said circuit and energized by the closure of said circuit.