US3916110A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Line circuit employing constant current devices for battery feed
Assignee: AG Communication Systems Corp
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Filing: 1974-05-02
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Granted: 1975-10-28
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Expires: 1994-05-02
Abstract
Abstract An improved line circuit using two constant current devices, one of which is independently set to a desired DC current value, while the other is controlled so as to have its constant value the same as the independent source. In principle, the independent current source acts as a master source, while the dependent current source, under feedback control, acts as a slave DC current sink.
Inventors
- 👤 David Q Lee
- 👤 Dinesh K Srivastava
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 21:43
CPC Classifications
H; H04; H04M; H04M19/00; H04M19/001; H04M19/005
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
107 words
A constant current line circuit for a two conductor loop telephone line whose impedance may vary with length comprising a source of direct current, a first constant current device whose magnitude is fixed connecting one terminal of said source to one conductor of said line, a second constant current device whose magnitude is continuously varied connecting the other terminal of said source to the other conductor of said line, and means for continuously varying the magnitude of said second constant current source to be always equal to the magnitude of said first constant current source, whereby a balanced high impedance battery feed to said line is provided.
Claim 2
Dependent Claim
107 words
A constant current line circuit for a two conductor loop telephone line whose impedance may vary with length comprising a source of direct current, a first constant current device whose magnitude is fixed connecting one terminal of said source to one conductor of said line, a second constant current device whose magnitude is continuously varied connecting the other terminal of said source to the other conductor of said line, and means for continuously varying the magnitude of said second constant current source to be always equal to the magnitude of said first constant current source, whereby a balanced high impedance battery feed to said line is provided.
Claim 3
Dependent Claim
17 words
The constant current line circuit of claim 1, wherein said source of direct current comprises a battery.
Claim 4
Dependent Claim
26 words
The constant current line circuit of claim 2, wherein said means for continuously varying the magnitude of said second constant current source comprises a differential amplifier.
Claim 5
Dependent Claim
72 words
The constant current line circuit of claim 3, further including means coupled across said two conductors of said line and establishing a first reference potential, and means coupled across the terminals of said source and establishing a second reference potential, said first and second reference potential being coupled to said differential amplifier to operate it and the output thereof being coupled to said second constant current source to continuously vary its magnitude.
Claim 6
Dependent Claim
63 words
The constant current line circuit of claim 4, wherein said means coupled across said two conductors of said line comprises resistance means for establishing said first reference potential midway between the potential existing on said two conductors, and wherein said means coupled across the terminals of said source comprises resistance means for establishing said second reference potential midway between ground and battery potential.
Claim 7
Dependent Claim
26 words
The constant current line circuit of claim 5, wherein said differential amplifier is referenced by said second reference potential, thereby canceling out fluctuations in battery voltage.
Claim 8
Dependent Claim
22 words
The constant current line circuit of claim 6, wherein said first reference potential equals said second reference potential for conditions of balance.
Claim 9
Dependent Claim
61 words
The constant current line circuit of claim 3, wherein said first constant current source comprises a transistor having its collector-emitter circuit connecting one terminal of said source to one conductor of said line, and wherein said second constant current source comprises a transistor having its collector-emitter circuit connecting the other terminal of said source of the other conductor of said line.
Claim 10
Dependent Claim
55 words
The constant current line circuit of claim 8, further including means for establishing the magnitude of said first constant current source of an arbitrarily fixed magnitude, and means for establishing the magnitude of said second constant current source, said differential amplifier setting the magnitude of said second current source under control of said latter means.
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) | 1978-10-27 | 1979-04-28 | 1979-10-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-27 | 1983-04-28 | 1983-10-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-27 | 1987-04-28 | 1987-10-28 | $7700.00 | Window Closed / Lapsed |