Abstract: The lowering and raising of slats of a venetian blind are controlled by control signals from a photodetector circuit which is mounted adjacent to the venetian blind and which acts responsive to predetermined limit values of the background brightness being exceeded. Following lowering of the venetian blind, control of the closing or screening angle of the slats is provided by a sun-tracking photodetector affixed to a slat and operating in dependence upon the angular alignment of the slat. In order to fix the closing angle of the slats at a selected value, subsequent adjustment of the slats is controlled by the sun-tracking photodetector which can, in turn, be controlled externally by a manually operated keying mechanism. The photodetector used in measurement of background brightness comprises three aligned photodiodes which are directed skyward in three different directions and which together detect the incident light over the full range of 180.degree. in front of the venetian blind.

Abstract: The protective covering for a marquee consists of a casing (22) carrying a winding shaft and having a discharge opening extending along the entire length of the casing, which can be closed tightly by a top flap (42) and a bottom flap (46). Top flap (42) is pivoted upward during the discharge of the marquee by its outer tube (14) counter to the force of gravity and following the re-entry of the marquee drops back into its closed position. Bottom flap (46) drops during the discharge of the marquee by its own specific gravity into open position and is drawn back into closed position at the end of the re-entry movement by means of closing levers (76) remaining in the movement path of the outer tube. The quite small top flap (42) cleans off the marquee, but loads it with only a slight weight. The pressure of the outer tube (14) against the closing levers (76) holds flaps (42, 46) dependably closed tightly in the re-entry position/closed position.