System for signalling unauthorized displacement of an article

Claim 1

SYSTEM FOR SIGNALLING UNAUTHORIZED DISPLACEMENT OF AN ARTICLE POSITIONED ON A SURFACE SUCH AS A PICTURE SUSPENDED ON A WALL, SAID SYSTEM COMPRISING A SIGNALLING CIRCUIT INCLUDING A SIGNALLING DEVICE, A SOURCE OF CURRENT AND A PAIR OF MAGNETICALLY OPERABLE SWITCHES FOR CONNECTING SAID DEVICE TO SAID SORUCE FOR CURRENT, EACH OF SAID SWITCHES BEING OF THE TYPE WHICH TENDS TO ASSUME ITS CONNECTING POSITION BUT WILL STAY IN ITS DISCONNECTING POSITION WHEN SUBJECTED TO A MAGNETIC FIELD, A HOUSING ENCASING SAID DEVICE, SAID SOURCE OF CURRENT AND SAID SWITCHES AND THEREWITH CONSTITUTING A SELF-CONTAINED UNIT DISPOSED IN A NORMAL POSITION BETWEEN SAID SURFACE AND SAID ARTICLE AND HIDDEN BY THE LATTER, AND A PLURALITY OF MAGNETS, AT LEAST ONE OF SAID MAGNETS BEING FIXED TO SAID PICTURE FOR MAINTAINING ONE OF SAID SWITCHES IN ITS DISCONNECTING CONDITION AS LONG AS SAID ARTICLE IS LEFT UNDISPLACED RELATIVE TO SAID UNIT, ANOTHER ONE OF SAID MAGNETS BEING FIXED TO SAID WALL FOR MAINTAINING THE OTHER ONE OF SAID SWITCHES IN ITS DISCONNECTING CONDITION AS LONG AS SAID UNIT IS LEFT UNDISPLACED RELATIVE TO SAID WALL, SAID UNIT HAVING PORTIONS OF FERROMAGNETIC MATERIAL FOR ATTRACTION BY ONE OF SAID MAGNETS FIXED TO SAID PICTURE AND BY ONE OF SAID MAGNETS FIXED TO SAID WALL WHEREBY SAID UNIT IS NORMALLY HELD IN SAID NORMAL POSITION.