development of warning devices made an intrusion into a new area

摘要

A signalling apparatus with pressure sensors, in particular for sensing intrusion into a closed surface area, with a yielding pipe embedded underground along the periphery of the surface area and filled with fluid; the pipe being divided into two separate sections by a deformable baffle plate to which are connected sensor means for supplying a signal depending on the deformation of said baffle plate, for initiating signalling means when said baffle plate is deformed.