US4747142A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Three-track sterophonic system
Assignee: TOFTE SOUND SYSTEMS Inc A CORP OF OR
•
Filing: 1985-07-25
•
Granted: 1988-05-24
•
Expires: 2005-07-25
Abstract
Abstract In a stereophonic reproduction system, a true center-channel signal is derived by combining the left and right signals into a monophonic signal, and canceling and overriding this monophonic signal with a second modified monophonic signal, the latter derived by combining properly bandpassed left and right signals that have been compressed, combined, and expanded. True left-and true right-channel signals are subsequently derived by subtracting the true center-channel signal voltage from the left and right signal voltages.
Inventors
- 👤 David A. Tofte
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 05:10
CPC Classifications
H; H04; H04S; H04S3/00
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
115 words
A three-track stereophonic system, comprising: a stereo source having left and right channels; first and second groups of pass-band filters, each group comprising a plurality of filters, the inputs of the filters of said first group being responsive to said left channel, and the inputs of the filters of said second group being responsive to said right channel; a plurality of compressors, each compressor having its input coupled to a corresponding output of each filter, and each compressor administering a 2:1 logarithmic compression to the signal input thereto; a plurality of expanders responsive to the outputs of said compressors; a central amplifier means responsive to the outputs of said expanders to provide a third channel.
Claim 2
Dependent Claim
115 words
A three-track stereophonic system, comprising: a stereo source having left and right channels; first and second groups of pass-band filters, each group comprising a plurality of filters, the inputs of the filters of said first group being responsive to said left channel, and the inputs of the filters of said second group being responsive to said right channel; a plurality of compressors, each compressor having its input coupled to a corresponding output of each filter, and each compressor administering a 2:1 logarithmic compression to the signal input thereto; a plurality of expanders responsive to the outputs of said compressors; a central amplifier means responsive to the outputs of said expanders to provide a third channel.
References Cited (Backward Citations)
US3679832A
Cited
US4074083A
Cited
US4024344A
Cited
US4293821A
Cited
US4442546A
Cited
US4498060A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-05-24 | 1991-11-23 | 1992-05-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-05-24 | 1995-11-23 | 1996-05-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-05-24 | 1999-11-23 | 2000-05-24 | $7700.00 | Window Closed / Lapsed |