PURPOSE:To reduce the interference between codes, by detecting a peak voltage of a tuning circuit output and controlling the gain in the frequency at an emphasis circuit depending on the comparison between the peak voltage and the reference voltage. CONSTITUTION:If the interference between codes is produced in an output of an adder 5, deficient or excessive output level is caused for peack voltage detecting circuits 71, 72-7N. If this output level is greater than the reference voltage Vref, the output of control circuits 81, 82-8N is smaller, resulting that the gain of emphasis circuits 91, 92-9N is smaller. Inversely, if the output level of peak voltage detecting circuits 71, 72-7N smaller than the referenve voltage Vref, the output of the control circuits 81, 82-8N is greater, resulting that the gain of emphasis circuits 91, 92-9N is greater. Thus, with the control like this, thein terference between codes can be rejected with the output of the emphasis circuit 9N.