Sperry Corporation

Sperry Rand Corporation

John W Craig

Robert Price

Hartvig E Melbye

Chao S Chi

Avraham Perahia

Chad S Chi

A detector for determining whether the time duration between a positive and a negative peak of a waveform is greater or less than a predetermined time interval comprises a delay line for delaying the waveform by the predetermined time interval. A peak detector of a first polarity for detecting the first occurring peak of the waveform is responsive to the delayed waveform to provide a signal upon the occurrence of the first occurring peak thereof. A peak detector of a second polarity for detecting the second occurring peak of the waveform is responsive to the undelayed waveform for providing a signal upon the occurrence of the second occurring peak thereof. A time sequence comparator provides a first output indication when the signal from the first peak detector occurs prior to the signal from the second peak detector and a second output indication when the signal from the second peak detector occurs prior to the signal from the first peak detector.

Precision time duration detector

A digital magnetic recording system is disclosed that utilizes partial response signalling to achieve the Nyquist data pulse rate with minimum bandwidth. A. C. bias is introduced to linearize the magnetic medium which, inter alis, permits reliable multilevel (greater than 2) data storage without impairing data accessibility. Preferably Class IV partial response is utilized with one or more sinusoidal lobes in the data frequency spectrum. The basic binary data to be stored is converted to, for example, ternary and the ternary data is precoded. The precoded ternary data is recorded on the magnetic medium via an interleaved dipulse sequence having a spectral null slightly outside the data frequency band. A pilot tone is inserted at the spectral null for timing recovery and automatic gain control.

High density bias linearized magnetic recording system utilizing Nyquist

Data channel gain-variation distortions are reduced by the following combination of operations. Successively occurring data items are cumulatively added in modulo fashion thereby providing a sequence of partial sums. An exponentiating circuit is introduced to provide an exponential function of the partial sums. The exponentiated partial sums are then recorded or transmitted on a data channel wherein the signals are distorted by relatively slow gain variations thereof. The received distorted signals are applied to a logarithmic circuit wherein the multiplicative gain variation distortions are converted to additive distortions. The logarithmically converted signals are applied to a subtractor that sequentially provides the differences in modulo fashion between successively occurring signals from the logarithmic circuit thereby yielding the data items with the distortions substantially reduced.

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Sudbury, MA, United States of America

John W Craig