Sperry Corporation

Magnetic Peripherals Inc.

Jorgen P Vinding

George V Jacoby

Martin Cohn

A ternary magnetic recording system wherein groups of binary input digits are transformed into corresponding groups of ternary recording code symbols utilizing a hierarchical code substitution system in which the longest valid group in the code is encoded. The code substitution system provides retention of the advantageous properties of a prior ternary recording system while significantly enhancing the automatic gain control utilized in amplitude discrimination between two of the ternary recording symbols. Anomalous detection of chained doublets is also obviated. Data recovery is effected by decoding apparatus utilizing an eight bit addressable ROM addressed with a twelve bit ternary word.

Encoding and decoding apparatus and method utilizing hierarchical code

A data recovery circuit useful in magnetic data recording systems employs doublet pulses to at least partially encode data. Measurement of the slope of the transition between doublet pulse half-cycle peaks and of the amplitude of this transition allows rejection of high frequency low amplitude noise and high amplitude low frequency noise. The use of nearly the entire peak-to-peak voltage swing of doublet pulses makes identifying them relatively reliable.

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Monte Sereno, CA, United States of America

Jorgen P Vinding