Browse Prior Art Database

DC Balanced Encoded Recording

IP.com Disclosure Number: IPCOM000083509D
Original Publication Date: 1975-Jun-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Furtney, RW: AUTHOR [+3]

Abstract

A DC-balanced (DC unbalance is constrained) recording signal results from selecting one of two (or more) encoded values for a given data value (symbol). The selection is based on accumulated deviation from DC balance and the data values. Initial signal polarity may also be an additional criterion.

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DC Balanced Encoded Recording

A DC-balanced (DC unbalance is constrained) recording signal results from selecting one of two (or more) encoded values for a given data value (symbol). The selection is based on accumulated deviation from DC balance and the data values. Initial signal polarity may also be an additional criterion.

A rotating head digital signal recorder exchanges signals with magnetic medium 10 via rotating head assembly 11 having write gap 12 and read gap 13. Rotating transformer assembly 14 couples gaps 12 and 13 to write line 15 and read line 16, respectively. Transport of tape 10 past the rotating head assembly 11 is in accordance with known techniques.

Data to be recorded on medium 10 is received over cable 20, supplied through multiple-pole, double-throw switch 21 to a pair of encoders 22, 23. Encoder 22 supplies a first type of record code values tending to make the record signal have a net negative charge, while encoder 23 supplies a second type of record code values tending to make the record signal have a net positive charge (or zero).

By sequencing encoder 22, 23, net accumulative signal DC imbalance is constrained to preset values. Hence, the activation of the respective encoders depends upon the accumulated digital sum variation of the signals previously recorded and the polarity of the last-recorded signal, as indicated by code selection circuit 24.

Circuit 24 actuates electronic switch 21 to synchronously pass data signals from cable 20 to...