Abstract: A control circuit (16) mounted on a faucet (10) operates an ultrasonic transducer (20) that transmits ultrasound into a target region (22) below the outlet (24) of the faucet. The control circuit receives electrical signals from the transducer when the transducer receives echoes from objects within the target region. The control circuit times the echoes to determine the distance of the object causing the echoes, and, if the distance of the object changes between successive measurements, the control circuit operates a valve (12) to permit water to flow. The circuit is powered by a rechargeable battery (18) that is charged by the action of a generator (31) that is driven by a turbine (34) powered by the flow of water through the faucet.