Abstract: An air curtain control system for a solar thermal receiver comprising: at least one air jet (505) arranged to produce a continuous planar air curtain (507) over at least a portion of a receiver aperture 509 of a solar thermal receiver, an air flow control device (517) for controlling a speed of air flow out of the air jet (505), at least one angular control device (503) for controlling an angle of the air curtain (507) relative to the receiver aperture 509, and a system controller (501) arranged to control the air flow control device (517) and angular control device (503) to isolate the receiver aperture (509) from ambient elements external to the receiver aperture (509).

Abstract: A safety system for alerting occupants of a fire or smoke occurring within a building in which the safety system includes a smoke detector associated with an electric door release mechanism of a locked door that is energised to unlock the door automatically in response to receiving a signal from a control unit which in turn receives a signal from a smoke detector when fire or smoke is detected so that the door is automatically opened by the electric door release mechanism being released by movement of an electrically operated striker plate to allow occupants trapped within the building to escape from the burning building, whilst allowing access to the building for emergency rescue personnel.

Abstract: A convertible ladder is provided which can be set up as an extension ladder, a step ladder or a trestle. A pair of leg assemblies each have a pair of sides connected by a plurality of rungs. Each leg assembly has regularly spaced hooks along its length which engage with the end lugs of a plank member. The plank member has arms provided with lugs which engage another pair of hooks on each leg assembly to form a trestle. The leg assemblies are also provided with a pair of upturned hook lugs which engage a rung of the other leg to form an extension ladder. In the step ladder configuration, the leg assemblies are maintained at maximum angular relationship by means of ties pivotally connected to one leg assembly with openings to engage pins on the other leg assembly.