Abstract: A multi-band processing system for automatically tuning the oscillator of a phase-locked loop to the frequency and phase of an applied input. The system includes an error detection circuit, a frequency controller, a scaling circuit, and a phase and frequency controller. The applied input and the oscillator output are coupled to the error detection circuit whose error output drives a charge pump/filter circuit. An error signal is derived from the difference between the loop charge pump output V.sub.1 and a preset charge pump zero error reference signal V.sub.ref, wherein the frequency controller regulates the oscillator output frequency according to a frequency error component of V.sub.1 -V.sub.ref, the scaling circuit scales the oscillator output frequency according to a system scaling signal N, and the phase and frequency controller adjusts the oscillator output frequency and phase according to V.sub.1 -V.sub.

Abstract: A circuit for filtering electrical waveforms in which the useful information is contained in patterns and spacing of zero-voltage crossings is disclosed. Illustratively, a disk memory system is disclosed in which the voltage peaks developed by the disk memory read-transducers are converted into zero-voltage crossing waveforms by differentiation. To eliminate false zero-voltage crossings caused by noise, the digital filter generates a linear ramp waveform whose magnitude is proportional to the time duration between successive zero-voltage crossings. False zero crossings typically have a short time duration between successive crossings. They are eliminated from the integrated ramp waveform by a comparator which only responds when the integrated waveform reaches a predetermined threshold level indicating the time between successive zero-voltage crossing exceeds a minimum time duration.