a circuit arrangement which includes an fm demodulator having a delay circuit which subjects the received fm signal to a preset time delay and a signal combining circuit which combines the delayed and undelayed fm signal to derive a combined signal the mean value of which is proportional to the frequency of the fm signal . a low pass filter derives the demodulated signal from such combined signal . the proportionality factor is determined by the preset time delay , which is controllable by a control signal supplied to the delay circuit by a datum level detector which detects a selected datum level of the demodulated signal ; for example , the lowest level of such signal . by controlling the time delay in accordance with such datum level , the datum level detector thereby stabilizes the maximum amplitude of the demodulated signal relative to the datum level thereof despite variations in the maximum frequency swing of the received fm signal .