Abstract: A burner comprising a primary mixing chamber having one or more gas inlets and one or more primary air inlets; and one or more secondary mixing chambers, a perforated portion being provided in a side wall of each of said secondary mixing chambers, and each of said secondary mixing chambers communicating with the primary mixing chamber; each primary air inlet 6 comprising an aperture in a wall of the primary mixing chamber and a sliding member attached to the primary mixing chamber over the aperture and movable between a first limit position when the aperture is completely covered by the member and a second limit position when the aperture is completely uncovered by the member, means being provided to retain the member at any position intermediate the first and second limit positions.

Abstract: This invention relates to a gas fire appliance of the kind which simulates an open fire burning solid fuel. In accordance with the invention such a gas fire appliance comprises a casing in which is mounted a support on which solid fuel simulating elements are supported, a transparent panel above and in front of said solid fuel simulating elements and a burner assembly. The burner assembly comprises a heater burner portion having burners disposed in at least two independently controllable sections together with a flame effect burner portion which also has burners disposed in at least two independently controllable sections. Conveniently the heater burner portion and the flame effect burner portion each has two sections namely an inner section and an outer section disposed on opposite sides of the respective inner section.

Abstract: An impedance element formed from a single-port, surface acoustic wave transucer which generates a conductance versus frequency response characteristic having first and second peaks separated by a valley at a predetermined frequency and which generates a susceptance versus frequency response characteristic having a substantially constant portion over a finite bandwidth on both sides of said predetermined frequency.