Abstract: The present invention converts an alternating current input into a direct current output by switching a current load at high speeds to create a voltage envelope having a maximum allowed voltage and a minimum allowed voltage. Complementary switching elements are employed to take advantage of both the positive and negative portions of an AC cycle. Load switching is arranged so that the current vector which represents the load is nearly coincident with the voltage vector which represents the power source. The system can operate in an open loop mode at a constant frequency, in a closed loop mode, or in a hysteresis mode. During open loop operation, the voltage envelope is not rigidly defined as the switching frequency remains constant. During hysteresis mode control, the voltage envelope remains fixed and the current switching frequency varies.

Abstract: A method of sequentially analyzing various body conditions with a plurality of probes is disclosed. Also disclosed, is a catheter which can be used to practice the method. The catheter has several independent lumens extending longitudinally therethrough for accepting probes and for introducing fluid therethrough and into a body cavity. The catheter outer body has a cross-sectional maximum outer dimension. The first lumen is circular in cross-section, and has a cross-sectional dimension of approximately half the maximum outer dimension of the catheter body. The first lumen is capable of accepting various probes, as well as allowing simultaneous fluid flow through the lumen. The second lumen is crescent-shaped in cross-section and occupies at least a quarter of an arc around the cross-section of the catheter body. The large cross-section of the second lumen allows for a high fluid flow rate through the lumen.

Abstract: A control circuit for a fluid-filled heating pad is described. The control circuit is unique in that it includes a thermistor that is located in close proximity to the heating pad. The circuit is also unique in that it includes a single high-precision reference resistor to self-calibrate the control circuitry.