Abstract: A central vacuum cleaning system 3 has a central vacuum unit 17 with a motor 10, a motor compartment 19, and a vacuum chamber 25. The system 3 also has a control circuit 1 for controlling power to the motor 10, and one or more airborne contaminant sensors 15 for sensing contaminants within the system 3. The sensors 15 may be located in pipes 31 motor compartment 19, vacuum chamber 25 and hose handle 34. Vacuum air may be drawn through aperture 37 in wall valve 38.

Abstract: A central vacuum cleaning system 3 has a central vacuum unit 17 with a motor 10, a motor compartment 19, and a vacuum chamber 25. The system 3 also has a control circuit 1 for controlling power to the motor 10, and one or more airborne contaminant sensors 15 for sensing contaminants within the system 3. The sensors 15 may be located in pipes 31 motor compartment 19, vacuum chamber 25 and hose handle 34. Vacuum air may be drawn through aperture 37 in wall valve 38.

Abstract: A central vacuum cleaning system 3 has a central vacuum unit 17 with a motor 10, a motor compartment 19, and a vacuum chamber 25. The system 3 also has a control circuit 1 for controlling power to the motor 10, and one or more airborne contaminant sensors 15 for sensing contaminants within the system 3. The sensors 15 may be located in pipes 31 motor compartment 19, vacuum chamber 25 and hose handle 34. Vacuum air may be drawn through aperture 37 in wall valve 38.

Abstract: A segmented optical system for use in an alarm system. A plurality of optical elements such as mirrors are arranged so that each of them directs radiation from a predetermined direction towards a common focal point. Each optical element defines a respective discrete field of view to a detector at the focal point, adjacent fields of view overlapping so that an object moving from within one field of view towards an adjacent field of view enters an area which is common to the two adjacent fields of view. There is thus a stepwise change in the intensity of radiation reaching the detector from a single source when that single source crosses the boundary of a field of view and yet there is no space between adjacent fields of view from which no radiation can be received by the detector.

Abstract: Apparatus for preventing the formation of condensation within a cabinet. A light reflective surface is mounted within the cabinet and thermally linked to the exterior of the cabinet so that the reflective surface temperature responds more rapidly to changes in the external ambient temperature than the cabinet itself. The formation of condensation on the reflective surface is detected by monitoring a light beam reflected from the reflective surface. When the formation of condensation on the reflective surface is detected a heater inside the cabinet is turned on to cause the condensation to evaporate.