A collaborative multimedia system includes a plurality of notebook processes operatively interconnected over a computer network to a conference server, and, an optional podium process capable of controlling the priority of communications within the conference. The means for dependent on flow for creating a pressure differential comprises either a dead-end detour channel from the flow channel to the valve, or a loop channel fed back to the control chamber of the valve. 9V as a combination of ultra-weak electrical currents. The wind power installation is controlled in such a way that upon the occurrence of a disturbance it remains on the connected electrical network and delivers to the connected electrical network a second power which is lower than the first power. Each of the covers is selectively pivoted over the feeding aperture in the associated one of the cups.