A circuit that receives signals from a dynamo and provides signals for charging a battery and indicating bicycle speed. The circuit includes a first switching circuit adapted to receive the dynamo signals and provide first signals for charging the battery; and a second switching circuit adapted to receive the dynamo signals and provide second signals for indicating bicycle speed. If the dynamo outputs periodic signals, the first signals may correspond to one of the half periods of the periodic signals (e.g., the positive half periods), and the second signals may correspond to the other half periods (e.g., the negative half periods) of the periodic signals.