A microwave oven, including a transformer assembly accommodating a transformer and filled with a cooling material to cool the transformer; and a temperature-sensitive switch electrically connected to the transformer to shut off power when a temperature of a surface of the transformer assembly is a predetermined overheating temperature. When a position A on the input image is transformed into a position B on the generated image by the inverse projection transformation, the CPU obtains a ratio of a distance between pixels around the position B to a distance between pixels around the position A. The processor can be configured to receive an input signal for a patient receiving chest compressions and to select at least one filter mechanism and to apply the filter mechanism to the signal to at least substantially remove chest compression artifacts from the signal. The comminuting apparatus is provided beneath the exit and has an entrance for receiving the scrap web.