Abstract: A power converting apparatus and method comprising a transformer and converting circuit mounted with the transformer for converting direct current to a series of pulses in the primary winding which includes a pulse train forming an effective current with reciprocal positive and negative sine wave components for each half cycle of chosen frequency. A gating circuit is mounted with the transformer for sequentially passing the pulses in the positive sine wave components followed by the pulses in the negative sine wave component, the gating circuit passes the pulses received in the secondary winding synchronously with the pulses in each half cycle of the pulse train to form a chosen frequency alternating current component. A filter is mounted with the gating circuit for removing selected components of the received signal while providing an output of the chosen frequency alternating current.

Abstract: In one exemplary embodiment, the efficiency of an acoustic-energy-type cleaner for vessels, such as heat exchangers, is substantially increased by propagating through the fluid in the vessel, a plurality of opposing acoustic wave trains, and continuously varying at least the frequency or phase relationship of said opposing wave trains for causing constructive interference between said opposing acoustic waves to create a series of augmented acoustic waves that are spatially displaced in relation to each other and successive in time interval for sweeping over the surfaces of the body to be cleaned.

Abstract: In one of the embodiments disclosed, apparatus is provided for communicating, in digital form, information from a plurality of analog sources located in a borehole to a location on the surface. A multiplexer is provided with a plurality of inputs for connecting the analog signal output of the data sources to an analog to digital converter in response to a sequence control circiut. The analog to digital converter converts the analog signals to digital data signals. A digital address signal is added to each data signal indicating the source of the data. The digital data signals and their addresses are applied to modulate or vary the power factor of power on a power cable mounted in the borehole. Receiver means is provided at the surface location for recovering the digital data and address signals for use on the surface. These signals may be displayed by display means, stored or used in a computer.