Abstract: A device for generating an electric output signal in response to the positioning of a mechanical member. The mechanical member carries an optical fibre, and the optical fibre coacts with one of several, preferably two, phototransistors in response to the setting position of the mechanical member. The phototransistors are connected to an amplifier generating the electric output signal corresponding to the member's position.The device may be used in control equipment for controlling the draught in a boiler, preferably an oil-fired boiler.

Abstract: A coupling arrangement between a shaft and a knob adapted for rotating the shaft, the knob being provided with a recess having a cross-sectional area which is substantially greater than the cross-sectional area of the shaft, and having a sleeve arranged to encircle the shaft with its inner surface and with its outer surface intended to be encircled by the recess in the knob. The outer surface of the sleeve has a cross-sectional area which is somewhat larger than the cross-sectional area of the recess of the knob. The knob is pressed over the sleeve and as a result of its elasticity imparts to the sleeve a compressing force which acts on the shaft and thereby presses the sleeve and the knob into firm, co-action with the shaft.