The original tilt sensors used a metal ball in a tube with two contacts at one end. when the ball rolled to the end of the tube with the contacts, then Closed is indicated, when the ball rolls away, then Open is indicated.
Better is if the ball is replaced by mercury since it can't get stuck like the ball often does after a couple years.
Obviously mercury is toxic and the number of manufacturers is probably reduced, but many of us have purchased after-market mercury switches to replace the rolling ball tubes in our older Tilt Sensors.
But the point is, tilt sensors generally means this "contact" mechanism vs an angular. I think accelerometers provide that.
