SYSTEMS FOR READING MAGNETIC RECORDINGS

摘要

A system for reading information stored on a flexible magnetic disk is disclosed. The system involves an amplitude detector for detecting at predetermined times whether the amplitude of the read signal is positive, zero or negative. This system includes an amplifier for the differential raw data signal whose gain is variable in response to changes in the amplitude of the raw data signal which occur over a relatively long period. The output of the automatic gain control amplifier is an equalized differential signal applied to the detector and to a threshold generator which provides an output reference signal which is a predetermined percentage of the input signal, and which is capable of following relatively rapid changes in the amplitude of the input signal. A positive and negative comparator circuit continually compares the differential equalized data signal against the generated threshold reference signal. The outputs of these comparators are sampled at clock times established from a phase-locked loop which is synchronized by pulses derived from the peaks of the input data signal.