US4454548A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Bias control method and apparatus for magnetic recording
Assignee: Bang and Olufsen AS
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Filing: 1981-11-06
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Granted: 1984-06-12
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Expires: 2001-11-06
Abstract
Abstract An input signal and a variable amplitude AC bias signal are applied to a record head in a magnetic media recorder. The AC bias signal amplitude is controlled by a feedback circuit in response to the total active bias signal applied to the record head, the total active bias signal including the AC bias signal and the high frequency portion of the input signal.
Inventors
- 👤 Joergen S. Jensen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 11:11
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/02; G11B5/027; G11B5/03
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
90 words
Apparatus for recording an input signal on a magnetic medium comprising: record head means for recording on the magnetic medium, variable amplitude AC bias signal generator means, means for applying the input signal and bias signal to said record head means, and feedback circuit means for controlling the bias generator means, measuring the total active bias signal resulting from the sum of the applied variable bias signal and the high frequency portion of the input signal applied to the recording and having its output applied to control the bias generator.
Claim 2
Dependent Claim
90 words
Apparatus for recording an input signal on a magnetic medium comprising: record head means for recording on the magnetic medium, variable amplitude AC bias signal generator means, means for applying the input signal and bias signal to said record head means, and feedback circuit means for controlling the bias generator means, measuring the total active bias signal resulting from the sum of the applied variable bias signal and the high frequency portion of the input signal applied to the recording and having its output applied to control the bias generator.
Claim 3
Dependent Claim
31 words
Apparatus according to claim 1 in which said feedback circuit means controls the bias signal generator to provide dynamically a substantially constant total active bias signal amplitude at the recording head.
Claim 4
Dependent Claim
54 words
Apparatus according to claims 1 or 2 wherein said feedback circuit means comprises frequency selective circuit means for passing the total active bias signal, reference signal generator means, and comparator means for comparing the reference signal amplitude and the total active bias signal amplitude to generate a control signal for controlling the bias generator.
Claim 5
Dependent Claim
34 words
Apparatus according to claim 3 wherein the frequency selective circuit means comprises filter circuit means having a cut off frequency at a frequency corresponding approximately to the upper frequency limit recordable by the apparatus.
Claim 6
Dependent Claim
27 words
Apparatus according to claim 4 wherein the filter circuit means comprises a high pass filter having a 6 dB/octave characteristic rising up to the cut off frequency.
Claim 7
Dependent Claim
41 words
Apparatus according to claim 3 further comprising means for adjusting the reference signal amplitude according to the type of tape used in the recorder, whereby the amplitude of the substantially constant total active bias signal at the recording head is selectable.
Claim 8
Dependent Claim
26 words
Apparatus according to claim 3 wherein the record head means has a coil and the input of the feedback circuit means is connected to said coil.
References Cited (Backward Citations)
US4263624A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-06-12 | 1987-12-12 | 1988-06-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-06-12 | 1991-12-12 | 1992-06-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-06-12 | 1995-12-12 | 1996-06-12 | $7700.00 | Window Closed / Lapsed |