Sri International

Joseph H Chadwick

Charles S Weaver

John M Yarborough, Jr

Donald J Burch

Floyd A Brown

A plural channel playback system comprising magnetic recording tape movable past a reproducing transducer head having at least one transducing element for each track is shown together with skew detecting means. At least two of the tracks are recorded with digital data signals comprising equal length data words with a parity bit, with the parity bits being simultaneously recorded along the tracks. Parity bit lock-on circuits are responsive to outputs from two tracks, which lock-on circuits generate word clock pulses in synchronization with the recorded parity bit signals. A phase detector responsive to word clock pulses from the parity bit lock-on circuits produces an error signal output proportional to the phase difference between said word clock pulse inputs thereto, which error signal is related to skew. The azimuthal position of the reproducing head relative to the recording tape is adjusted either manually or automatically to minimize the error signal.

Skew sensing for digital tape playback

A recording-playback system is disclosed wherein analog signals are converted to digital form which then are compressed and encoded using a variable length code. The encoded signals are temporarily stored in a buffer memory from which they are read out to a variable speed recorder for recording thereof. The rate at which the encoded signals are read out to the recorder and the recording speed are controlled in direct proportion to the percent fullness of the buffer memory for recording with substantially constant bit density on the recording medium. The ratio of the buffer memory read out rate and recording speed may be selected for recording with a substantially maximum bit density. A playback unit for the system includes a variable speed playback for playing back the recorded digital signals. The signals are temporarily stored in a buffer memory, from which memory they are read out to a decoder which operates at a substantially constant word rate. The speed of operation of the variable speed playback means is controlled in inverse proportion to the fullness of the buffer memory to maintain a supply of signals for use by the decoder. The decoded signals are supplied to a digital decompression filter for digital reconstruction thereof. A digital to analog converter converts the digital signals to analog form.

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Menlo Park, CA, United States of America

Joseph H Chadwick