Abstract: A magnetic alarm sensor (80) includes a magnet (84) positioned so that dominant length components (108) of its magnetic field lines (104) are oriented so that they are transverse to a switch axis (96) of a magnetically sensitive switch (88). This orientation permits more versatile mounting options for placement of the alarm sensor, especially to positions that are less prone to displacements over time. A preferred embodiment of the magnetic alarm sensor (110) employs two spatially collinear magnetic switches (116, 118) vertically oriented along a door bracket (14) and a magnet (120) positioned on a door panel (22) such that the magnetic field lines (152) of the magnet are generally perpendicular to the switch axis (136) of the magnetic switches. The magnetic switches are electrically connected in parallel to extend the range of vertical critical distance between the magnet and the magnetic switches to inhibit false alarms caused by door sag.

Abstract: A method and an apparatus employing a compact magnetic security switch for detecting the open or closed position of corresponding fixed frame and movable closure members, such as door and window assemblies, of entryways of buildings. The security switch assembly includes a high intrinsic coercive force rare earth, preferably neodymium, alloy magnet mountable on a movable closure member within a close clearance and within a predetermined gap and break distance of a switch mounted on a corresponding fixed frame member when in closed position, such that the electrical contacts interact with the magnet and thereby place the switch in a nonalarm position. The method of the present invention provides for mounting the rare earth alloy magnet without invading the subsurface structural integrity of the movable closure member.

Abstract: A self-contained smoke detector system has internal self-diagnostic capabilities and accepts a replacement smoke intake canopy (14) without a need for recalibration. The system includes a microprocessor-based self-diagnostic circuit (200) that periodically checks sensitivity of the optical sensor electronics (24, 28) to smoke obscuration level. By setting tolerance limits on the amount of change in voltage measured in clean air, the system can provide an indication of when it has become either under-sensitive or over-sensitive to the ambient smoke obscuration level. An algorithm implemented in software stored in system memory (204) determines whether and provides an indication that for a time (such as 27 hours) the clean air voltage has strayed outside established sensitivity tolerance limits. The replaceable canopy is specially designed with multiple pegs (80) having multi-faceted surfaces (110, 112, 114).