Abstract: An FM/FMX stereophonic receiver is capable of receiving an FM or an FMX stereophonic broadcast signal. The FM stereophonic broadcast signal includes a stereo sum signal and stereo difference signal, whereas the FMX stereophonic broadcast signal further includes a compressed stereo difference signal and an FMX ID signal indicating the FMX stereophonic broadcast signal. The FM/FMX stereophonic receiver has a stereo demodulator for receiving said broadcast signal and for producing left and right stereo signals, a detector for detecting the field strength of the receiving signal, and a noise reducer, which may be a circuit for changing the mode from stereophonic mode to monaural mode or a high cut circuit for attenuating the signals of high frequency region, for reducing noise signals contained in the left and right stereo signals.

Abstract: A variable reactance circuit which can produce equivalent reactance varying from negative given values to positive given values in accordance with fundamental reactance elements such as capacitor, coil, etc. The present invention has a big advantage of being capable of easily producing the positive, negative equivalent reactance given times as much as the basic reactance element with the use of a circuit which can be integrated.