Abstract: An apparatus and method for supplying a regulated direct electric current comprises a switch mode regulator having an input for receiving a varying source of electrical power. A linear regulator provides a source of low noise direct current and has an input connected so as to receive a voltage that is dependent upon an output of the switch mode regulator. A first servo-loop provides a first control signal to the switch mode regulator. The first control signal is varied according to a variation in the voltage across the linear regulator. A second servo-loop provides a second control signal to the linear regulator. The second control signal is varied according to the difference between a voltage that is related to an output of the linear regulator and a reference voltage. The second servo-loop has a higher gain than the first servo-loop when both of the servo-loops are operating at frequencies that are within their operating frequency ranges.

Abstract: A metal detector apparatus and a metal detection method for detecting and discriminatory interrogating a metal target buried in the ground. The detector includes a transmitter for providing a first varying magnetic field including at least two frequency components and a receiver for providing a resultant voltage dependent upon a second magnetic field resulting from the combined effects of the ground and metal targets buried in the ground, upon the first alternating magnetic field. The detector samples at least three voltage measurements of the resultant voltage over three different time periods to provide three sampled values which are then processed by a microprocessor to provide three average ground balanced signals from which at least two ratios are calculated and compared against a pre-defined response.

Abstract: An apparatus and method for ultrasonic cleaning is disclosed in which a transducer (35) in a liquid bath is driven by electronic circuitry causing rapid change of frequency to limit development of high concentration for any significant period of time. The electronic circuitry uses two field effect transistors (19 and 20) driving a square wave into an inductor (31) and capacitor (32) in series with a transformer inductor (33) which is coupled in parallel to the transducer (35) the inductor (31) and capacitor (32) and the transformer inductor (33) which is coupled in parallel to the transducer (35) being selected to be resonant at a mean driving frequency.