US3883815A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fail-safe selectable low-pass filtering
Assignee: Trane US Inc
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Filing: 1973-08-15
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Granted: 1975-05-13
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Expires: 1993-08-15
Abstract
Abstract This invention relates to a vital type of selectable active lowpass filtering circuit. The selectable low-pass filtering circuit includes a half section resistance-capacitance filter network and a variable gain transistor amplifier. The input of the transistor amplifier is coupled to the half section resistance-capacitance filter network and the output of the transistor amplifier is selectively coupled to one of a plurality of load resistors each of which establishes a different gain for the transistor amplifier.
Inventors
- 👤 Reed H Grundy
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 04:20
CPC Classifications
B; B61; B61L; B61L3/00; B61L15/00; B61L15/0094; H; H03; H03G; H03G3/00; H03G3/02
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
101 words
A vital type of a selectable low-pass filtering circuit comprising, a half section filter network including a resistive element and a four-terminal capacitive element, said fourterminal capacitive element having a first and a second pair of terminals, said first pair of terminals coupled to a source of a.c. input signals, and a variable gain amplifier having its input connected to said second pair of terminals and having its output coupled to at least a select one of a plurality of load resistors so that the gain of the amplifier is varied in accordance with the value of the selected load resistor.
Claim 2
Dependent Claim
101 words
A vital type of a selectable low-pass filtering circuit comprising, a half section filter network including a resistive element and a four-terminal capacitive element, said fourterminal capacitive element having a first and a second pair of terminals, said first pair of terminals coupled to a source of a.c. input signals, and a variable gain amplifier having its input connected to said second pair of terminals and having its output coupled to at least a select one of a plurality of load resistors so that the gain of the amplifier is varied in accordance with the value of the selected load resistor.
Claim 3
Dependent Claim
24 words
A vital type of a selectable low-pass filtering circuit as defined in claim 1, wherein said variable gain amplifier includes an active semiconductive device.
Claim 4
Dependent Claim
28 words
A vital type of a selectable low-pass filtering circuit as defined in claim 1, wherein said variable gain amplifier includes a transistor connected in a common emitter configuration.
Claim 5
Dependent Claim
38 words
A vital type of a selectable low-pass filtering circuit as defined in claim 1, wherein said variable gain amplifier includes a transistor having its collector electrode coupled to the selected one of said plurality of said load resistors.
Claim 6
Dependent Claim
39 words
A vital type of a selectable low-pass filtering circuit as defined in claim 1, wherein a switching device couples each of the selected ones of said plurality of said load resistors to the output of said variable gain amplifier.
Claim 7
Dependent Claim
37 words
A vital type of a selectable low-pass filtering circuit as defined in claim 1, wherein a relay contact couples a selected one of said plurality of said load resistors to the output of said variable gain amplifier.
Claim 8
Dependent Claim
80 words
A vital type of a selectable low-pass filtering circuit as defined in claim 1, wherein said variable gain amplifier includes a transistor having an emitter, a collector and a base electrode, said base electrode coupled to the junction of a voltage dividing network which is connected between a voltage supply terminal and ground, said emitter electrode resistively coupled to ground, said collector electrode coupled to said voltage supply terminal by the selected one of said plurality of said load resistors.
Claim 9
Dependent Claim
33 words
A vital type of a selectable low-pass filtering circuit as defined in claim 1, wherein said half section filter network is coupled to said input of said variable amplifier by a coupling capacitor.
References Cited (Backward Citations)
US3124760A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-05-12 | 1978-11-11 | 1979-05-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-05-12 | 1982-11-11 | 1983-05-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-05-12 | 1986-11-11 | 1987-05-13 | $7700.00 | Window Closed / Lapsed |