Abstract: An electrically conductive anti-intrusion device characterized by a free-standing grill of brittle frangible rods cantilevered across an opening to be protected, with a breakable electrical conductor within the rods, the rods and conductor being sufficiently fragile to snap upon an attempt to dislodge the grill, thereby generating an alarm.

Abstract: A screen assembly includes a rectangular mesh sheet with several parallel security strands of insulated conductive wire extending between opposite sides of the sheet. Insulated cross wires lie on a face of the mesh near the opposite sides thereof, are joined by welding or soldering to points on the security strands, and are cut at selected locations to provide a sinuous electrical path through the screen. A spline of insulative material extends around the border of the mesh sheet and encapsulates the locations where the cross wire is joined to the security strands, the spline including upper and lower spline portions lying on opposite faces of the mesh and sealed together through the mesh. A frame for holding the screen includes a pair of frame halves that snap together, with the lower half having an undercut slot that receives a flange at the periphery of the spline, the lower frame half also having a stop surface opposite the undercut slot which abuts the inner edge of the spline.