Abstract: A centrifugal pump has a housing forming a chamber having intake and output ports and a plastic lining in the chamber An impeller wheel in the chamber is formed by a hub rotatable about an axis, a rear disk projecting radially from the hub, a front disk projecting radially from the hub and offset axially from the rear disk, and radial vanes extending axially between the disks. The hub, disks, and vanes are formed of a high-strength material such as metal and carries a coating on outer surfaces of the hub, disks, and vanes of a plastic of lower strength than the material.

Abstract: A microwave circuit in strip line technology contains metallic resonator strips on one side of a dielectric layer. Alternatively another end of consecutive resonator strips is connected by means of at least one via to a metallic surface on an opposite side of said dielectric layer. Said end of each resonator strip is connected to at least one via and is formed relative to said at least one via so that the effective electrical length of each resonator strip connected through the via is identical.

Abstract: An apparatus and method are described for producing a test signal with a desired signal-to-noise ratio on a selectable output frequency for measuring a transmission system. A carrier signal, generated from a carrier signal, and a noise signal are remixed with the carrier signal in a bandwidth equal to or smaller than a smallest signal bandwidth of the transmission system. The levels of the carrier signal and the noise signal are adjusted to a predetermined ratio based on a measurement of the remixed carrier signal and the remixed noise signal. The noise signal is attenuated and added to the carrier signal until the desired signal-to-noise ratio is attained.