Patent US4023070A successfully refreshed from Google Patents.
US4023070A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrical circuit for audio services
Assignee: Individual
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Filing: 1975-04-07
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Granted: 1977-05-10
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Expires: 1995-04-07
Abstract
Abstract A mains safety isolating device is provided for an audio device e.g. guitar and microphone for preventing fatal electrical shock upon grounding breakdown and in which a transformer has a primary winding grounded at a point and connected to an electro-acoustic transducer to receive electrical signals therefrom, a secondary winding of said transformer is connected to a primary winding of a second transformer by signal conductors, a secondary winding of said second transformer being connected to the amplifier circuit of a mains powered amplifying and loudspeaker apparatus, said secondary winding being grounded at a second point separate and isolated from the first-mentioned point.
Inventors
- 👤 Charles Francis McCrory
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 14:58
CPC Classifications
H; H02; H02H; H02H9/00; H02H9/04; H04; H04B; H04B15/00; H04B15/02; H04R; H04R3/00
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
89 words
An audio device, comprising an electro-acoustic transducer, connected to a primary winding of a first transformer, said primary winding being also connected to ground at a first point and a secondary winding of said transformer being connected to the primary winding of a second transformer by signal conductors, a secondary winding of said second transformer being connected to an amplifier circuit of a mains powered amplifying and loud speaker apparatus, said secondary winding being connected to ground at a second point separate and electrically isolated from said first point.
Claim 2
Dependent Claim
89 words
An audio device, comprising an electro-acoustic transducer, connected to a primary winding of a first transformer, said primary winding being also connected to ground at a first point and a secondary winding of said transformer being connected to the primary winding of a second transformer by signal conductors, a secondary winding of said second transformer being connected to an amplifier circuit of a mains powered amplifying and loud speaker apparatus, said secondary winding being connected to ground at a second point separate and electrically isolated from said first point.
Claim 3
Dependent Claim
23 words
A device according to claim 1 wherein a potential divider is connected between the signal conductors, with a center tap connected to ground.
Claim 4
Dependent Claim
12 words
A device according to claim 1, wherein the transformer cores are grounded.
Claim 5
Dependent Claim
36 words
A device according to claim 1 wherein a hum rejection circuit, comprising a resistance and variable capacitor connected in parallel to each other and in series with a further capacitor, is connected between the signal conductors.
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) | 1980-05-09 | 1980-11-08 | 1981-05-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-05-09 | 1984-11-08 | 1985-05-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-05-09 | 1988-11-08 | 1989-05-10 | $7700.00 | Window Closed / Lapsed |