US4737991A
Expired / Lapsed
US
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Audio multiplex television tuner
Assignee: Pioneer Corp
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Filing: 1986-05-09
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Granted: 1988-04-12
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Expires: 2006-05-09
Abstract
Abstract In a sound multiplex television tuner, when the input field strength becomes smaller than a certain value, a level control means continuously attenuates the sub signal demodulation output with the aid of the field strength detection signal which a field strength detector circuit provides according to the input field strength. The characteristic of response to input field strength of the level control means is switched, according to a given sound multiplex mode, so that its operation becomes most suitable for the sound multiplex mode, thereby to suppress the noise without causing the television viewer to feel a sense of incongruity in the perceived sound.
Inventors
- 👤 Yoshiro Sugai
- 👤 Hiroyuki Kimura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 12:16
CPC Classifications
H; H04; H04H; H04H40/00; H04H40/18; H04H40/27; H04H40/36; H04H40/45; H04H40/63; H04B; H04B1/00; H04B1/06; H04B1/16; H04B1/1646; H04B1/1661; H04B1/1669; H04B1/1676; H04H40/72; H04N; H04N5/00; H04N5/44; H04N5/60; H04N5/607
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
149 words
A sound multiplex tuner for decoding an input signal comprised of an encoded main signal and an encoded subsignal, to provide audio output signals, said sound multiplex tuner comprising: a subsignal circuit comprising means for demodulating said encoded subsignal from said input signal before said encoded main signal and said encoded subsignal are subjected to said decoding; a field strength detector for detecting a field strength of said input signal; lever control means, responsive to said field strength detector, for continuously attenuating said encoded subsignal when said field strength is less than a predetermined value, said level control means being provided in said subsignal circuit; means for selecting the operation of said sound multiplex tuner to any one of a plurality of modes corresponding to a plurality of possible input signals modes; and wherein said level control means has a characteristic of response switched according to said selected mode.
Claim 2
Dependent Claim
149 words
A sound multiplex tuner for decoding an input signal comprised of an encoded main signal and an encoded subsignal, to provide audio output signals, said sound multiplex tuner comprising: a subsignal circuit comprising means for demodulating said encoded subsignal from said input signal before said encoded main signal and said encoded subsignal are subjected to said decoding; a field strength detector for detecting a field strength of said input signal; lever control means, responsive to said field strength detector, for continuously attenuating said encoded subsignal when said field strength is less than a predetermined value, said level control means being provided in said subsignal circuit; means for selecting the operation of said sound multiplex tuner to any one of a plurality of modes corresponding to a plurality of possible input signals modes; and wherein said level control means has a characteristic of response switched according to said selected mode.
Claim 3
Dependent Claim
42 words
A sound multiplex tuner as recited in claim 1, wherein said level control means comprises a low-pass filter that attenuates at frequencies higher than a low-pass band to a greater degree when said detected field strength is less than a predetermined value.
Claim 4
Dependent Claim
23 words
A sound multiplex tuner as recited in claim 2, wherein said low-pass filter further comprises a time constant circuit for smoothing said sub-signal.
Claim 5
Dependent Claim
46 words
A sound multiplex tuner as recited in claim 1, wherein said level control means comprises a variable attenuator, a degree of attenuation of said sub-signal being controlled inversely to said detected field strength over a range of said detected field strength less than said predetermined value.
Claim 6
Dependent Claim
61 words
A sound multiplex tuner as recited in claim 4, wherein said plurality of modes comprise a stereo mode and an alternate audio channel mode and wherein said level control means, when said field strength is less than said predetermined value, attenuates said sub-signal more when said stereo mode has been selected than when said alternate audio channel mode has been selected.
Claim 7
Dependent Claim
46 words
A sound multiplex tuner as recited in claim 1, wherein said level control means comprises a variable attenuator, a degree of attenuation of said sub-signal being controlled inversely to said detected field strength over a range of said detected field strength less than said predetermined value.
Claim 8
Dependent Claim
42 words
A sound multiplex tuner as recited in claim 6, wherein said level control means comprises a low-pass filter that attenuates at frequencies higher than a low-pass band to a greater degree when said detected field strength is less than a predetermined value.
Claim 9
Dependent Claim
22 words
A sound multiplex tuner as recited in claim 6, wherein said attenuator further comprises a time constant circuit for smoothing said sub-signal.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-04-12 | 1991-10-12 | 1992-04-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-04-12 | 1995-10-12 | 1996-04-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-04-12 | 1999-10-12 | 2000-04-12 | $7700.00 | Window Closed / Lapsed |