Patent US3921104A successfully refreshed from Google Patents.
US3921104A
Expired / Lapsed
US
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Adjustable equalizers useable in audio spectrum
Assignee: Dolby Laboratories Inc
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Filing: 1974-11-18
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Granted: 1975-11-18
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Expires: 1994-11-18
Abstract
Abstract In an equalizer using multiple, parallel-connected band-pass filters, the filters are removed from the signal path and connected to tap off inputs from the signal path and feed back outputs to combining means in the signal path. Adjustable potentiometers on the input or output side of the filters adjust the boost or cut in the bands of the filters individually. Failure of a filter results in a flat response in the corresponding band, not a notch as in prior art equalizers.
Inventors
- 👤 Kenneth James Gundry
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 22:32
CPC Classifications
H; H03; H03G; H03G5/00; H03G5/02; H03G5/025; H04; H04H; H04H60/00; H04H60/02; H04H60/04
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
152 words
A signal equalizer, comprising a signal path extending from an input terminal to an output terminal, two series-connected combining circuits in said path, a plurality of band-pass filters having their inputs connected to a point between the two combining circuits, a plurality of potentiometers individual to the filters and having adjustable taps, the outputs of the filters being connected to the adjustable taps respectively, and the two ends of each potentiometer being connected to the combining circuits respectively to contribute two signal components to the signal passing from the input terminal to the output terminal, which components are equal at an intermediate setting of the potentiometer, and the relative phases of the signals throughout the equalizer being such that the two signal components contributed by each potentiometer boost the signal passing from the input terminal to the output terminal at one combining circuit and cut this signal at the other combining circuit.
Claim 2
Dependent Claim
152 words
A signal equalizer, comprising a signal path extending from an input terminal to an output terminal, two series-connected combining circuits in said path, a plurality of band-pass filters having their inputs connected to a point between the two combining circuits, a plurality of potentiometers individual to the filters and having adjustable taps, the outputs of the filters being connected to the adjustable taps respectively, and the two ends of each potentiometer being connected to the combining circuits respectively to contribute two signal components to the signal passing from the input terminal to the output terminal, which components are equal at an intermediate setting of the potentiometer, and the relative phases of the signals throughout the equalizer being such that the two signal components contributed by each potentiometer boost the signal passing from the input terminal to the output terminal at one combining circuit and cut this signal at the other combining circuit.
Claim 3
Dependent Claim
17 words
A signal equalizer according to claim 1, wherein both combining circuits combine all signals applied thereto additively.
Claim 4
Dependent Claim
23 words
A signal equalizer according to claim 2, wherein the signal provided by the first combining circuit at the said point is phase inverted.
Claim 5
Dependent Claim
23 words
A signal equalizer according to claim 2, wherein the signal provided by the first combining circuit at the said point is non-phase inverted.
Claim 6
Dependent Claim
39 words
A signal equalizer according to claim 1, wherein both combining circuits combine all the signals supplied thereto from the potentiometers additively and subtract the resulting signal components from the input signal and the signal at the said point respectively.
Claim 7
Dependent Claim
12 words
A signal equalizer according to claim 1, wherein the filters are non-inverting.
Claim 8
Dependent Claim
12 words
A signal equalizer according to claim 1, wherein the filters are phase-inverting.
Claim 9
Dependent Claim
13 words
A signal equalizer according to claim 1, wherein the filters are active filters.
Claim 10
Dependent Claim
16 words
A signal equalizer according to claim 1, wherein the filters are spaced at one-third octave intervals.
Claim 11
Dependent Claim
17 words
A signal equalizer according to claim 1, wherein the potentiometers also have fixed taps connected to earth.
Claim 12
Dependent Claim
18 words
A signal equalizer according to claim 10, wherein the fixed taps are at the mid-points of the potentiometers.
Claim 13
Dependent Claim
107 words
A signal equalizer comprising a signal path extending from an input terminal to an output terminal, a combining circuit in said path, a plurality of band-pass filters having their outputs connected to the combining circuit, a plurality of potentiometers individual to the filters and having adjustable taps, the inputs of the filters being connected to the adjustable taps respectively, the two ends of the potentiometers being connected to the input and output terminals respectively, and inverting means so arranged that the phase of the signal at one end of each potentiometer is inverted relative to the phase of the signal at the other end of the potentiometer.
Claim 14
Dependent Claim
107 words
A signal equalizer comprising a signal path extending from an input terminal to an output terminal, a combining circuit in said path, a plurality of band-pass filters having their outputs connected to the combining circuit, a plurality of potentiometers individual to the filters and having adjustable taps, the inputs of the filters being connected to the adjustable taps respectively, the two ends of the potentiometers being connected to the input and output terminals respectively, and inverting means so arranged that the phase of the signal at one end of each potentiometer is inverted relative to the phase of the signal at the other end of the potentiometer.
Claim 15
Dependent Claim
30 words
A signal equalizer according to claim 12, wherein the inverting means comprise an inverter between one of the input and output terminals and the ends of the potentiometers connected thereto.
Claim 16
Dependent Claim
30 words
A signal equalizer according to claim 12, wherein the inverting means comprise an inverter in the signal path between the combining means and one of the input and output terminals.
Claim 17
Dependent Claim
12 words
A signal equalizer according to claim 12, wherein the filters are non-inverting.
Claim 18
Dependent Claim
12 words
A signal equalizer according to claim 12, wherein the filters are phase-inverting.
Claim 19
Dependent Claim
13 words
A signal equalizer according to claim 12, wherein the filters are active filters.
Claim 20
Dependent Claim
16 words
A signal equalizer according to claim 12, wherein the filters are spaced at one-third octave intervals.
Claim 21
Dependent Claim
17 words
A signal equalizer according to claim 12, wherein the potentiometers also have fixed taps connected to earth.
Claim 22
Dependent Claim
17 words
A signal equalizer according claim 19, wherein the fixed taps are at the mid-points of the potentiometers.
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) | 1978-11-17 | 1979-05-19 | 1979-11-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-17 | 1983-05-19 | 1983-11-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-17 | 1987-05-19 | 1987-11-18 | $7700.00 | Window Closed / Lapsed |