Abstract: Known fluid friction clutches, which are electromagnetically controlled from either an engine side or a driving side, require very strong and space-consuming coils in order to produce magnetic forces which are sufficient to control valve levers which, on the side of the clutch away from the coil, open or close a connection opening between a storage chamber and a working chamber. To address this problem, the magnet coil is placed as close as possible to the clutch housing and, by way of inserted flux guiding rings, achieve a magnetic shunt of the lines of magnetic flux such that the coil does not have to be overdimensioned. The flux guiding rings extend to just in front of an armature of the valve lever and, with small radial air gaps, to the housing of the coil. The rings can otherwise be arranged opposite the rotatable shaft made of a magnetic material. Such clutches are appropriate for use as fan clutches of vehicle engines.