US3843573A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Noise reduction device of a tape recorder
Assignee: Pioneer Corp
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Filing: 1972-08-24
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Granted: 1974-10-22
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Expires: 1992-08-24
Abstract
Abstract A method and apparatus for reducing high frequency noise in a reproduced magnetically recorded signal. The recorded signal is reproduced by first and second magnetic heads. The frequency range of the second head is limited to a predetermined range and the output of the head is used to control a bypass circuit connected to the output of the first head. When no signal is reproduced by said second head the high frequency output of the first head is shunted to ground. In this manner, high frequency noise which is not within said predetermined range is not reproduced by said second head and therefore the noise reproduced by the first head is shunted to ground at the output of said first head rather than being amplified and emitted by a speaker.
Inventors
- 👤 T Kosaka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 17:23
CPC Classifications
G; G11; G11B; G11B23/00; G11B23/0007; H; H03; H03G; H03G9/00; H03G9/02; H03G9/12; H03G9/18
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
242 words
A noise reduction device for a magnetic tape recorder, said device comprising: a. first magnEtic head means for reproducing a signal recorded on a tape; b. amplifier means for amplifying said reproduced signal; c. second magnetic head means for reproducing only a first portion of said signal recorded on the tape, wherein said portion lies in a predetermined frequency range and wherein said second magnetic head means is positioned to reproduce said signal prior to said first magnetic head means; d. bypass circuit means coupled between said first magnetic head means and said amplifier means for controllably shunting to ground a second signal portion, above said predetermined frequency range, reproduced by said first magnetic head means in inverse proportion to the output level of said second magnetic head means; and e. means coupling said second magnetic head means and said bypass circuit means for applying the output of said second magnetic head means to said bypass circuit means; wherein said bypass circuit means is controlled by the output level of said second magnetic head means such that said second reproduced signal portion is shunted only when the output level of said second magnetic head means is below a certain level, whereby noise signals reproduced by said first magnetic head means and above said predetermined frequency range are shunted in proportion to the output level of the second magnetic head means by said bypass circuit means and not applied to said amplifier means.
Claim 2
Dependent Claim
242 words
A noise reduction device for a magnetic tape recorder, said device comprising: a. first magnEtic head means for reproducing a signal recorded on a tape; b. amplifier means for amplifying said reproduced signal; c. second magnetic head means for reproducing only a first portion of said signal recorded on the tape, wherein said portion lies in a predetermined frequency range and wherein said second magnetic head means is positioned to reproduce said signal prior to said first magnetic head means; d. bypass circuit means coupled between said first magnetic head means and said amplifier means for controllably shunting to ground a second signal portion, above said predetermined frequency range, reproduced by said first magnetic head means in inverse proportion to the output level of said second magnetic head means; and e. means coupling said second magnetic head means and said bypass circuit means for applying the output of said second magnetic head means to said bypass circuit means; wherein said bypass circuit means is controlled by the output level of said second magnetic head means such that said second reproduced signal portion is shunted only when the output level of said second magnetic head means is below a certain level, whereby noise signals reproduced by said first magnetic head means and above said predetermined frequency range are shunted in proportion to the output level of the second magnetic head means by said bypass circuit means and not applied to said amplifier means.
Claim 3
Dependent Claim
76 words
A noise reduction device as set forth in claim 1 wherein said bypass circuit means comprises: an integrating circuit for integrating the output of said second magnetic head means, and a variable impedance circuit responsive to the output of said integrating circuit and having a high impedance when the signal reproduced by said first magnetic head means lies within said frequency range and having a low impedance when said reproduced signal lies above said frequency range.
Claim 4
Dependent Claim
20 words
A noise reduction device as set forth in claim 2 wherein said variable impedance device includes a field effect transistor.
Claim 5
Dependent Claim
56 words
A noise reduction device as set forth in claim 3 wherein said variable impedance circuit further includes a condenser coupled between said second magnetic head means and said field effect transistor wherein a signal reproduced by said second magnetic head means charges said condenser thus causing said field effect transistor to assume a high impedance state.
Claim 6
Dependent Claim
26 words
A noise reduction device as set forth in claim 1 wherein said first and second magnetic head means each comprises a reproducing head and an amplifier.
Claim 7
Dependent Claim
24 words
A noise reduction device as set forth in claim 5 wherein said reproducing head of said second magnetic head means is an erasing head.
Claim 8
Dependent Claim
20 words
A noise reduction device as set forth in claim 1 wherein said frequency range is approximately 300 to 3,000 Hz.
Claim 9
Independent Claim
150 words
A method of reducing noise in a magnetic tape recorder comprising the steps of: a. reproducing a signal recorded on a magnetic tape using a first magnetic head means; b. reproducing, prior to the first reproducing step, only a portion of the signal recorded on said magnetic tape using a second magnetic head means, said portion including signal frequencies within a predetermined frequency range; c. shunting to ground the frequency components of said signal reproduced by the first magnetic head means, which are above said predetermined frequency range, when the level of the signal portion reproduced by said second magnetic head means is below a certain level, whereby noise above said predetermined frequency range is shunted to ground; and d. amplifying the entire frequency range of said signal reproduced by said first magnetic head means when the output level of said second magnetic head means is above said certain level.
Claim 10
Independent Claim
150 words
A method of reducing noise in a magnetic tape recorder comprising the steps of: a. reproducing a signal recorded on a magnetic tape using a first magnetic head means; b. reproducing, prior to the first reproducing step, only a portion of the signal recorded on said magnetic tape using a second magnetic head means, said portion including signal frequencies within a predetermined frequency range; c. shunting to ground the frequency components of said signal reproduced by the first magnetic head means, which are above said predetermined frequency range, when the level of the signal portion reproduced by said second magnetic head means is below a certain level, whereby noise above said predetermined frequency range is shunted to ground; and d. amplifying the entire frequency range of said signal reproduced by said first magnetic head means when the output level of said second magnetic head means is above said certain level.
Claim 11
Dependent Claim
20 words
The method as set forth in claim 8 wherein said predetermined frequency range is approximately from 300 to 3,000 Hz.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-10-21 | 1978-04-22 | 1978-10-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-10-21 | 1982-04-22 | 1982-10-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-10-21 | 1986-04-22 | 1986-10-22 | $7700.00 | Window Closed / Lapsed |