Devices and methods for measuring prothrombin time and hematocrit by analyzing the change in reactance in a sample are presented. This realizes a data structure that causes the recording and deleting places on the information storage medium to correspond spuriously to places on a single tape, such as a VTR tape. The charging circuit includes a step-up ferro-resonant transformer network and a full-wave rectifier. The power communicator may determine a target power level for the load devices based on the communication over the conductors.