Abstract: A playback/recording modulating-demodulating device, having a voltage-controlled oscillator (VCO), a voltage-current inverter (VCI), a band-pass filter, an amplitude limiter, and a phase-locked loop. In playback mode, the playback input signal is applied to the band-pass filter, the phase-locked loop is activated, and the VCI is set to produce a reference signal which controls the band-pass filter to tune the playback input signal. The tuned playback signal is applied to the amplitude limiter which produces an amplitude-limited signal which is applied to the phase-locked loop to produce a demodulated playback output signal. In record mode, the phase-locked loop is deactivated, the VCO produces a signal having a frequency which varies according to the voltage of a record input signal, and the VCI outputs a current control signal, having an output current related to the voltage of the record input signal, which is applied to the band-pass filter to control its bandwidth.