Abstract: Apparatus for communicating information across a solid wall has one or two outside ultrasonic transducers coupled to an outside surface of the wall and connected to a carrier generator for sending an ultrasonic carrier signal into the wall and for receiving an output information signal from the wall. One or two inside ultrasonic transducers are coupled to an inside surface of the wall and one of them introduces the output information signal into the wall. When there are two inside transducers inside the wall, one receives the carrier signal and the second transmits the carrier after it is modulated by the output information from the sensor. When there is one inside transducer, the output information from the sensor is transmitted by changing the reflected or returned signal from the inside transducer. A power harvesting circuit inside the wall harvests power from the carrier signal and uses it to power the sensor.

Abstract: An EIT system includes a plurality of voltage sources for supplying a corresponding plurality of voltages to a corresponding number of other structures, voltage source calibration means for calibrating each voltage source, and switching means for individually connecting the calibration means to each voltage source in succession during a period when each other structure is in an inactive condition. Calibrating respective voltages and currents for each voltage source compensates for shunt impedance of each voltage source. A method for calibrating the system includes individually connecting the calibration means to each voltage source in succession during a period when each other structure is in an inactive condition for calibrating all of said voltage sources in the same way.

Abstract: The wheel rim protector is a concave-convex disk for covering a vehicle wheel rim to protect the wheel rim from the application of fluids that may stain or corrode the wheel rim during detailing of the tires. The wheel rim protector has a pair of crossed ribs forming a cruciform handle to provide a grip for the user, and may have a lower lip for engagement with the wheel rim when the user presses the disk against the wheel rim. The contour of the disk permits multiple wheel rim protectors to be stacked together during transport, display or storage, and accommodates dust caps or ornamentation projecting from the wheel hub.

Abstract: A circuit for applications such as electrical impedance tomography includes a voltage-to-current converter having an input for receiving a voltage waveform and an output for outputting a current waveform to a load at an output resistance for the voltage-to-current converter. The voltage-to-current converter includes resistance control means for adjusting the output resistance of the voltage-to-current converter under computer control. The circuit of the present invention also includes an inductance control circuit operatively connected to the voltage-to-current converter for synthesizing a selected inductance. The inductance control circuit includes inductance control means for adjusting the value of the selected inductance by computer control.