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Variable Length Erasure on Write Error Recovery

IP.com Disclosure Number: IPCOM000092243D
Original Publication Date: 1968-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Scully, RF: AUTHOR [+2]

Abstract

Defects encountered during recording on magnetic tape are avoided during a rewrite operation by a variable length erase gap system. This stores a count relating to the distance of the defect from the beginning of a record. Prior systems for erasing tape areas containing defects results in excessive erasure of useable tape when the defect occurs near the beginning of a fixed length erasure, or requires wasted time in repetitive erasures and rewrite attempts when the defect originates near the end of a long record.

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Variable Length Erasure on Write Error Recovery

Defects encountered during recording on magnetic tape are avoided during a rewrite operation by a variable length erase gap system. This stores a count relating to the distance of the defect from the beginning of a record. Prior systems for erasing tape areas containing defects results in excessive erasure of useable tape when the defect occurs near the beginning of a fixed length erasure, or requires wasted time in repetitive erasures and rewrite attempts when the defect originates near the end of a long record.

A signal at terminal 20 indicates that a normal write operation is in process and permits the gating of capstan tachometer pulses appearing at 21 through And 1 and Or 3 into binary counter 4. In the event that a defect or recording error is encountered, a signal is introduced at 22, partially conditioning And 5. Then as soon as 3 is not producing a count pulse for 4, invert circuit 14 completely conditions 5, thus gating the contents of 4 through And's 6 into register 7. By logic not shown, 4 is then reset, the signal is removed from 20, and the tape is backspaced to the beginning of the record to initiate an erase gap operation. Initiation of the erase gap operation is indicated by a signal at three terminals EG, this signal remaining until the erase gap operation is completed.

And 13 is partially conditioned by an off indication from 7, but is deconditioned when a count is stored in 7. The absence of an output from 13 causes invert circuit 15 to complete the conditioning of And 2, thus again gating tachometer pulses at 21 into counter 4 to ref...