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.