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Use of Multibit Encoding to Increase Linear Recording Densities in Serially Recorded Records

IP.com Disclosure Number: IPCOM000093152D
Original Publication Date: 1967-Jun-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Mattson, RL: AUTHOR

Abstract

Through the use of multibit recording and detection, linear recording densities are increased in magnetic, thermoplastic, silver halide, and other recording media. Increased accuracy is obtained in timing and clocking circuits. A phase-encoded signal Sl is shown in drawing 1. S1, when recorded, is degraded by the bandwidth of the recording process. If the recording is magnetic, the readback signal S2, when integrated, appears as signal S3.

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Use of Multibit Encoding to Increase Linear Recording Densities in Serially Recorded Records

Through the use of multibit recording and detection, linear recording densities are increased in magnetic, thermoplastic, silver halide, and other recording media. Increased accuracy is obtained in timing and clocking circuits. A phase-encoded signal Sl is shown in drawing 1. S1, when recorded, is degraded by the bandwidth of the recording process. If the recording is magnetic, the readback signal S2, when integrated, appears as signal S3.

Decoding S3 is accomplished by a sequentiaI machine decoder operating as shown in the table. The inputs to the machine are formed on coincidence of clock signal G2 and the occurrence Z or nonoccurrence N of a zero crossing of S3. If the machine starts in state A and every record starts with a string of zeros, entries in the table give the next state of the machine and the present output, ? if unknown, 0 if the recorded bit is 0, and 1 if the recorded bit is 1. The zero crossing of S3 can vary +/- 25% with reliable decoding being realized.

Drawing 2 exemplifies two-bit operation utilizing I1.....I5 signals and their
complements. One of these can be used for a home address mark or a beginning of record mark. The other four signals can be used for the four possible combinations of two data bits 00, 01, 10, and 11. Each signal represents two bits and is divided into six clock periods. The sequential machine encoder and decoder operate as sho...