US3747079A
Expired / Lapsed
US
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Reducing dead-tracking in recording systems
Assignee: International Business Machines Corp
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Filing: 1971-06-01
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Granted: 1973-07-17
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Expires: 1991-06-01
Abstract
Abstract A self-clocking magnetic recording system, such as a magnetic tape system, is subject to dead tracking (i.e., loss of signals from a track on the media). During dead-tracking, the variable frequency clock VFC) associated with the dead track is synchronized to the data frequency of an adjacent operating track to thereby maintain the VFC of the dead track at approximately the desired frequency. This action enables resyncing the VFC to its track. Upon successful detection of data being read from a given dead track, synchronization of the given VFC is returned to the given track.
Inventors
- 👤 D Bailey
- 👤 B Fiorino
- 👤 J Rodriguez
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 08:22
CPC Classifications
G; G11; G11B; G11B20/00; G11B20/10; G11B20/18
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
166 words
A parallel track magnetic recording system having a signal detection circuit for each of a plurality of tracks with read means for supplying a readback signal, each circuit having variable frequency clock (VFC) means responsive to signals derived from the associated track for generating clock signals having a predetermined relation to the data rate thereof, the system being subjectable to malfunctions during which no reliable signal is producible by at least one of said circuits, said tracks being spaced apart along a recording media; the improvement including frequency synchronizing means comprising: first means for sensing and indicating that a given circuit operatively associated with a given track is producing no reliable signals, while another circuit is generating clock signals derived from its associated track; and second means responsive to said indication for deriving a signal from said another circuit for synchronizing said VFC means of said given circuit to said derived signal while said given circuit is not generating a reliable signal from said given track.
Claim 2
Dependent Claim
166 words
A parallel track magnetic recording system having a signal detection circuit for each of a plurality of tracks with read means for supplying a readback signal, each circuit having variable frequency clock (VFC) means responsive to signals derived from the associated track for generating clock signals having a predetermined relation to the data rate thereof, the system being subjectable to malfunctions during which no reliable signal is producible by at least one of said circuits, said tracks being spaced apart along a recording media; the improvement including frequency synchronizing means comprising: first means for sensing and indicating that a given circuit operatively associated with a given track is producing no reliable signals, while another circuit is generating clock signals derived from its associated track; and second means responsive to said indication for deriving a signal from said another circuit for synchronizing said VFC means of said given circuit to said derived signal while said given circuit is not generating a reliable signal from said given track.
Claim 3
Dependent Claim
61 words
The system of claim 1 having at least three tracks and each said signal detection circuit having an independent one of said first means, and said second means includes plural independent means operatively associated with pairs of said circuits respectively associated with adjacent ones of said tracks for exchanging signals between circuits in said pairs of respectively derived said VFC means.
Claim 4
Dependent Claim
64 words
The system of claim 1 wherein said second means includes plural independent means respectively associated with a plurality of adjacent tracks with said VFC means of said given track being operatively associated with at least two of said independent means such that VFC means in any of said adjacent tracks can be synchronized by signals derived from said VFC means of said given track.
Claim 5
Dependent Claim
96 words
The system of claim 1 wherein each said second means includes switching means, each said switching means receiving control signals from its respective operatively associated track and being supplied derived signals from a VFC means in a circuit operatively associated with another track, each said switching means capable of transferring said derived signals to said VFC means in its respective circuit and being responsive to said indication from said first means that said given circuit is the circuit operatively associated therewith to transfer one of said derived signals to said VFC means of said given circuit.
Claim 6
Dependent Claim
51 words
The system of claim 4, further including resync means in each of said circuits, said resync means being responsive to signals received from said given track to switch synchronization of said VFC means of said given track from signals derived from said another VFC means to signals from said given track.
Claim 7
Dependent Claim
28 words
The system of claim 1 including phase synchronizing means interposed between said VFC means in said given circuit and said another channel and said given circuit read means.
Claim 8
Dependent Claim
20 words
The system of claim 1 wherein said another channel VFC means supplies its clock signals to said given VFC means.
Claim 9
Dependent Claim
28 words
The system of claim 1 wherein said another channel VFC means has a stored signal and is operative to supply said stored signal to said given VFC means.
Claim 10
Dependent Claim
44 words
The system of claim 1 wherein said another channel VFC means includes amplifier means for supplying an analog signal representative of the frequency of operation thereof for use as a reference signal and said given VFC means includes means for receiving said analog signal.
Claim 11
Independent Claim
93 words
The method of reducing duration of dead-tracking in a recording system, including the steps of: detecting that a given channel is inoperative to supply readback signals and inhibiting operation of data circuits operatively associated therewith for dead-tracking said given channel; synchronizing a given variable frequency clock (VFC) in said given channel with a signal derived from anOther VFC of a data circuit which is not so inhibited; and eliminating said dead-tracking by detecting successful readback operation of said given channel and then resynchronizing said given VFC with readback signals of said given channel.
Claim 12
Independent Claim
93 words
The method of reducing duration of dead-tracking in a recording system, including the steps of: detecting that a given channel is inoperative to supply readback signals and inhibiting operation of data circuits operatively associated therewith for dead-tracking said given channel; synchronizing a given variable frequency clock (VFC) in said given channel with a signal derived from anOther VFC of a data circuit which is not so inhibited; and eliminating said dead-tracking by detecting successful readback operation of said given channel and then resynchronizing said given VFC with readback signals of said given channel.
Claim 13
Dependent Claim
35 words
The method of claim 10 wherein said another VFC means is selected always to be a VFC means associated with a track in the immediate geographic proximity on a magnetic media with said given track.
Claim 14
Dependent Claim
31 words
The method of claim 11 wherein said another VFC can be one of several VFC''s of several channels and is selected in accordance with predetermined criteria established for the recording system.
Claim 15
Dependent Claim
156 words
A parallel track magnetic recording system having a signal detection channel for each of a plurality of active tracks with read means for supplying a readback signal, each channel having variable frequency clock (VFC) means responsive to signals derived from the associated track for generating clock signals having a predetermined relation to the data rate thereof, the system being subjectable to malfunctions during which no reliable signal is producible by at least one of said circuits, said tracks being spaced apart along a recording media; the improvement including frequency synchronizing means, in combination: first means for sensing and firstly indicating that a given channel operatively associated with a given track is not producing reliable readback signals; and second means responsive to said indication for supplying a frequency synchronizing signal related to said data rate for frequency synchronizing said VFC means of said given circuit to an approximate frequency of any readback signal from said recording means.
Claim 16
Dependent Claim
156 words
A parallel track magnetic recording system having a signal detection channel for each of a plurality of active tracks with read means for supplying a readback signal, each channel having variable frequency clock (VFC) means responsive to signals derived from the associated track for generating clock signals having a predetermined relation to the data rate thereof, the system being subjectable to malfunctions during which no reliable signal is producible by at least one of said circuits, said tracks being spaced apart along a recording media; the improvement including frequency synchronizing means, in combination: first means for sensing and firstly indicating that a given channel operatively associated with a given track is not producing reliable readback signals; and second means responsive to said indication for supplying a frequency synchronizing signal related to said data rate for frequency synchronizing said VFC means of said given circuit to an approximate frequency of any readback signal from said recording means.
Claim 17
Dependent Claim
40 words
The system set forth in claim 13 further including means in said first means secondly indicating a reliable readback signal in said given channel and phase resynchronizing means responsive to said first means second indication to rephase said VFC means.
Claim 18
Dependent Claim
31 words
The system set forth in claim 14 wherein said second means receives a signal from another channel to supply said frequency synchronizing signal to said VFC means of said given circuit.
Claim 19
Dependent Claim
43 words
The system set forth in claim 13 wherein said second means includes means deriving a signal independent of said given circuit and related to the data rate in said system while said first indication is actively indicating dead tracking in said given circuit.
Claim 20
Dependent Claim
59 words
The system set forth in claim 13 wherein said second means includes switching means connected to a channel associated with an active record track with additional record tracks between said given and active record tracks and being responsive to said first indication to supply a signal to said given circuit derived from signals detected from said active record track.
Claim 21
Independent Claim
86 words
The method of reducing dead tracking in a recording system, including the steps of: detecting low-quality readback in a record channel, then, while the readback has a low-quality, inhibiting transfer of data signals therefrom while simultaneously frequency synchronizing said record channel to a data rate of the recording system based upon signals derived from the system independent of said record channel; and detecting possible recovery of said record channel from said low-quality readback, then rephasing said record channel to said readback signal for re-establishing readback operations.
Claim 22
Independent Claim
86 words
The method of reducing dead tracking in a recording system, including the steps of: detecting low-quality readback in a record channel, then, while the readback has a low-quality, inhibiting transfer of data signals therefrom while simultaneously frequency synchronizing said record channel to a data rate of the recording system based upon signals derived from the system independent of said record channel; and detecting possible recovery of said record channel from said low-quality readback, then rephasing said record channel to said readback signal for re-establishing readback operations.
References Cited (Backward Citations)
US3074027A
Cited
US3518625A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-16 | 1977-01-15 | 1977-07-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-16 | 1981-01-15 | 1981-07-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-16 | 1985-01-15 | 1985-07-17 | $7700.00 | Window Closed / Lapsed |