Abstract: A drilling device including a hydraulically actuated drive for exerting an oscillatory action on the drive including the drive element, inserting device for hoses conducting a working medium to a pressure-actuated hammer mounted on a front end of the rod and the flushing head at an oscillation angle ranging between 180.degree.-360.degree.. The flushing head is fixed oscilatorily with the drive member and both are swingable about a swivelling axis out of an alignment with the slide and the drive member is formed with a recess for selectively attaching a respective plug-in rod end of the drill rod, so that a torque produced by the drive is transmitted to the drill rod by the drive unit upon interlocking of the flushing head and rod.

Abstract: A circuit arrangement for bicycle lighting systems including a dynamo having an output winding. Front and rear lamps connected in series across the winding. A tap divides the winding into two parts, the lamps each connecting to a corresponding winding part and interconnecting at a junction joint. An impedance is interposed between the tap and lamp junction point. The number of turns and resistances of the winding parts are of value such that the junction point and tap are at the same potential, establishing system equilibrium, under normal operating conditions, despite variation in dynamo voltage and lamp resistance with bicycle speed. The impedance may be provided as the inherent resistance of a further winding connecting the junction point and tap and compensating for a difference in winding part resistance and turns ratios required for equilibrium. A further impedance may be coupled across the rear lamp.