Abstract: A shopping cart security system assists in preventing the theft of a shopping cart from a parking lot of an establishment where the carts are used. The parking lot has at least one entrance and exit driveway. The system includes a magnet mounted on the shopping cart and an actuator buried below the surface of the driveway for generating a signal in response to passage of the cart with the magnet over the driveway. The actuator extends generally transversely with respect to and substantially completely across the driveway. An alarm issues a warning in response to the signal generated by the actuator. Also, a system for monitoring unauthorized entry into a restricted area having a door, a magnet carried by the door and an actuator controlled by the magnet for signalling opening of the door.

Abstract: Layers of a thin, electrically insulating material are bonded together to form a switch. The bottom layer of the switch has electrically conductive areas aligned with openings through a second layer. A third layer has a pattern of spaced lines of an electrical conductor positioned over the openings in the second layer. Fluid pressure applied to the bottom layer causes flexing of the bottom layer toward the third layer to bring the electrically conductive areas into contact with the pattern of conductive lines on the third layer, thereby closing the switch. A vent chamber in the second layer is pneumatically coupled to the openings in the second layer so that when the switch is closed air in the openings in the second layer can be vented to the vent chamber. The switch can be used to sense changes in fluid pressure in a water system, for example.