US3685015A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Character bit error detection and correction
Assignee: Xerox Corp
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Filing: 1970-10-06
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Granted: 1972-08-15
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Expires: 1990-10-06
Abstract
Abstract Method and apparatus for detecting and correcting single bit errors in a bit pattern recorded on a two-track magnetic recording medium, the bit pattern including a parity bit. The bits corresponding to binary ones are recorded as flux transitions on one track and the bits corresponding to binary zeros are recorded as flux transitions on the other track. An error is defined if a flux transition is not detected in both tracks for a particular bit location or if flux transitions are detected in both tracks for a particular bit location. A detected error is shifted into an error register at the associated bit location as the bit pattern is shifted into a binary storage register. If established parity is not lost and the number of errors in the bit pattern which ended with the parity bit is not greater than one, the bit detected to be in error is complemented in the binary storage register.
Inventors
- 👤 Robert P Bocek
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 16:57
CPC Classifications
G; G06; G06F; G06F11/00; G06F11/07; G06F11/16; G06F11/1608; G06F11/1612; G11; G11B; G11B20/00; G11B20/10; G11B20/18; G11B20/1833
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
253 words
Apparatus for correcting errors detected in a bit pattern recorded as transitions in a magnetic recording medium along first and second tracks, said bit pattern comprising a plurality of binary bits and a parity bit, each bit being either a binary one or zero, said apparatus comprising: means for recording the binary one bits of said bit pattern as flux transitions along said first track and the binary zero bits of said bit pattern as flux transitions along said second track, means for reading the bits recorded on said first and second tracks and producing electrical pulses corresponding to each transition, first means coupled to said reading means for generating an error signal when no flux transition occurs at a bit position along said first and second tracks or if there are flux transitions at a bit position along both of said first and second tracks, second means coupled to said reading means for generating said bit pattern, means coupled to said second means for storing said generated bit pattern, means coupled to said second means for forming a parity bit as the generated bit pattern is being stored, means responsive to said error signal for comparing the formed parity bit and the stored parity bit and produciNg a correction signal if the compared bits are not the same, and gating means coupled between said first means and said storage means and responsive to said correction signal for forming the complement in said storage means of the bit detected to be in error.
Claim 2
Dependent Claim
253 words
Apparatus for correcting errors detected in a bit pattern recorded as transitions in a magnetic recording medium along first and second tracks, said bit pattern comprising a plurality of binary bits and a parity bit, each bit being either a binary one or zero, said apparatus comprising: means for recording the binary one bits of said bit pattern as flux transitions along said first track and the binary zero bits of said bit pattern as flux transitions along said second track, means for reading the bits recorded on said first and second tracks and producing electrical pulses corresponding to each transition, first means coupled to said reading means for generating an error signal when no flux transition occurs at a bit position along said first and second tracks or if there are flux transitions at a bit position along both of said first and second tracks, second means coupled to said reading means for generating said bit pattern, means coupled to said second means for storing said generated bit pattern, means coupled to said second means for forming a parity bit as the generated bit pattern is being stored, means responsive to said error signal for comparing the formed parity bit and the stored parity bit and produciNg a correction signal if the compared bits are not the same, and gating means coupled between said first means and said storage means and responsive to said correction signal for forming the complement in said storage means of the bit detected to be in error.
Claim 3
Dependent Claim
37 words
The apparatus as defined in claim 1 further including means coupled between said second means and said storage means for determining if bit pattern parity has been lost and inhibiting said gating means if parity is lost.
Claim 4
Dependent Claim
41 words
The apparatus as defined in claim 2 further including means inhibiting said gating means when two or more errors are detected in said bit pattern or if the parity bit has been detected to be in error by said first means.
Claim 5
Independent Claim
209 words
A method of detecting errors in a bit pattern recorded as magnetic flux transitions on a magnetic recording medium along first and second tracks, said bit pattern comprising a plurality of binary bits and a parity bit, each bit being either a binary one or binary zero, said method comprising the steps of recording the binary one bits of said bit pattern as transitions along said first track, recording the binary zero bits of said bit pattern as transitions along said second track, reading said bit pattern from said first and second tracks, storing the bit pattern read from said first and second tracks, forming a parity bit as the bit pattern is being stored, generating an error signal during the step of reading if no flux transition is detected at a bit position along said first and second tracks or if there are flux transitions at a bit position along both said first and second tracks, comparing the formed parity bit with the stored parity bit in response to the error signal, producing a correction signal if the compared parity bits are not the same, and complementing the stored bit detected to be in error as indicated by said generated error signal in response to said correction signal.
Claim 6
Independent Claim
209 words
A method of detecting errors in a bit pattern recorded as magnetic flux transitions on a magnetic recording medium along first and second tracks, said bit pattern comprising a plurality of binary bits and a parity bit, each bit being either a binary one or binary zero, said method comprising the steps of recording the binary one bits of said bit pattern as transitions along said first track, recording the binary zero bits of said bit pattern as transitions along said second track, reading said bit pattern from said first and second tracks, storing the bit pattern read from said first and second tracks, forming a parity bit as the bit pattern is being stored, generating an error signal during the step of reading if no flux transition is detected at a bit position along said first and second tracks or if there are flux transitions at a bit position along both said first and second tracks, comparing the formed parity bit with the stored parity bit in response to the error signal, producing a correction signal if the compared parity bits are not the same, and complementing the stored bit detected to be in error as indicated by said generated error signal in response to said correction signal.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-08-15 | 1976-02-14 | 1976-08-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-08-15 | 1980-02-14 | 1980-08-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-08-15 | 1984-02-14 | 1984-08-15 | $7700.00 | Window Closed / Lapsed |