Burglar alarm system

Claim 1

A burglar alarm system mounted in a doorway framing which comprises a wooden door jamb having two substantially parallel major faces and two minor faces substantially perpendicular to the major faces, one of the major faces having a recessed end portion delimited by one of the minor faces and a shoulder constituting a stop for a door, and the door jamb defining a door latch bolt hole in the recessed end portion, a wall including wooden wall stud means adjacent the other major face of the door jamb, the door jamb being mounted on the wall and the minor faces of the door jamb extending substantially parallel to the wall, and a reinforcement metal plate extending over a substantial portion of the wall stud means and a substantial portion of the one minor face of the door jamb, the reinforcement plate being securely affixed to the wall stud means and the one minor face of the door jamb and covering a substantial region of the minor door jamb face adjacent and beyond the door latch bolt hole, the securely affixed plate holding the door jamb firmly in position, the burglar alarm system comprising (a) a pair of elongated electrically conductive sheets arranged between the minor door jamb face and the reinforcement plate, the electrically conductive sheets extending in side-by-side relationship along a major portion of the reinforcement plate and being electrically insulated from each other, (b) an electrically insulating sheet arranged between the reinforcement plate and the pair of electrically conductive sheets, (c) a burglar alarm, and (d) an electric control circuit connected to the burglar alarm and energizable to set off the alarm, the circuit being connected to the electrically conductive sheets and being energized upon electrical contact being made between the sheets.