Abstract: A drain device for draining flat roofs, balconies, terraces or other flat structures, has an inflow body provided with a collar rim. When the inflow body is mounted, the collar rim lies on the surface of the roof. A loose flange can be introduced into the inflow body. The flange also has a collar rim. A connector film can be tensed between the collar rims of the inflow body and the loose flange for establishing a tight connection of a covering layer between said two elements. In order to allow for abnormally large amounts of water to be drained, the inflow body is provided with a cavity, into which two drain pipes and lead. One of the drain pipes co-operates with a pressurized, i.e., a pumped drainage system, and the other one of the drain pipes cooperates with a free-flowing drainage system.

Abstract: Double propeller for propelling aircraft, with two coaxially and axially offset propellers that can be driven separately by associated drive mechanisms through a central shaft and a hollow shaft. To reduce noise and maintain safe operation even when one propeller drive breaks down, the propellers rotate in the same direction and can at at least one prescribed angle of rotation to each other be coupled together in such a way that they cannot rotate in relation to each other by means of a clutch that can be disengaged.

Abstract: The control unit for switching on a teaching device for conveying optical and/or acoustical learning information which includes a transducer for converting the pulse, skin resistance, blood pressure or respiration as to intensity and rhythm into an electrical analog signal followed by a detector for delivering an electrical digital signal when the alpha-state of the test subject is reached. The detector controls a switching unit for switching on the teaching device when the digital signal is applied. The analog signal is additionally applied to a signal generator which feeds an output signal corresponding to the analog signal to a lamp and/or a loudspeaker for purposes of biofeedback.