The present invention relates generally to a catheter having a torque transmitting shaft which retains adequate flexibility. A resistance component may be selectively configured in parallel with the far-end telephone, where the resistance component has a value representative of resistance produced by the far-end telephone being off hook. Pigment Red 122, the yellow toner has a hue angle of from 93 to 100\xb0 and the bright yellow toner has a hue angle of from 60 to 85\xb0 in L*a*b* color system. An amplification controller is used to set the amplification power of the sensor signal amplifier based on the amplitude of the digitized sensor signal and a determination result of the abnormal combustion by the abnormal combustion detector.