US4088843A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electronic current feed circuit
Assignee: Post Office
•
Filing: 1976-11-09
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Granted: 1978-05-09
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Expires: 1996-11-09
Abstract
Abstract A current feed circuit for a telephone exchange transmission bridge comprising a pair of electronic circuit elements each of which has one terminal connected to a respective one of a pair of telephone lines and another terminal connected to one terminal of an electrical power supply. Each circuit element is a simulated inductance and can provide a resistive path for d.c. current from the power supply to a subscriber's telephone.
Inventors
- 👤 Alastair S. Rogers
- 👤 Norman T. Thurlow
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 09:52
CPC Classifications
H; H04; H04M; H04M19/00; H04M19/001; H04M19/005; H04Q; H04Q2213/00; H04Q2213/1308; H04Q2213/13082; H04Q2213/13305; H04Q2213/1332
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
108 words
A current feed circuit for a telephone exchange transmission bridge comprising: a pair of electronic circuit elements which form a balanced network, each circuit element having one terminal for connection to a respective one of a pair of telephone lines and another terminal for connection to one terminal of an electrical power supply, each circuit element being so arranged that when connected in a transmission bridge it forms a simulated inductance and can provide a resistive path for d.c. current from the power supply to a subscriber's telephone, each circuit element including an operational amplifier having a non-inverting input, and a common capacitor connected between the operational amplifiers.
Claim 2
Dependent Claim
108 words
A current feed circuit for a telephone exchange transmission bridge comprising: a pair of electronic circuit elements which form a balanced network, each circuit element having one terminal for connection to a respective one of a pair of telephone lines and another terminal for connection to one terminal of an electrical power supply, each circuit element being so arranged that when connected in a transmission bridge it forms a simulated inductance and can provide a resistive path for d.c. current from the power supply to a subscriber's telephone, each circuit element including an operational amplifier having a non-inverting input, and a common capacitor connected between the operational amplifiers.
Claim 3
Dependent Claim
63 words
A current feed circuit for a telephone exchange transmission bridge as claimed in claim 1, wherein each said electronic circuit element comprises a transistor having a collector-emitter circuit connected in series with resistive components between said terminals, the operational amplifier output being connected to the base of said transistor, and a resistor connected between said non-inverting input and the collector of said transistor.
Claim 4
Dependent Claim
37 words
A current feed circuit for a telephone exchange transmission bridge as claimed in claim 2, wherein each circuit element includes fault sensing means responsive to an overload condition between said terminals to render said circuit element inoperative.
Claim 5
Dependent Claim
57 words
A current feed circuit for a telephone exchange transmission bridge as claimed in claim 3, wherein said fault sensing means comprise a first diode connected between the collector of said transistor and the inverting input of the operational amplifier and a second diode connected between the non-inverting input of the operational amplifier and one of said terminals.
Claim 6
Dependent Claim
35 words
A current feed circuit for a telephone exchange transmission bridge as claimed in claim 2, wherein each electronic circuit element includes a zener diode connected to the collector of said transistor to absorb voltage surges.
Claim 7
Dependent Claim
22 words
A current feed circuit for a telephone exchange transmission bridge as claimed in claim 1, wherein said electrical power supply is stabilized.
Claim 8
Dependent Claim
15 words
A telephone exchange transmission bridge including a current feed circuit as claimed in claim 1.
Claim 9
Dependent Claim
17 words
A telephone exchange transmission bridge as claimed in claim 7, wherein said bridge is a transformer bridge.
Claim 10
Dependent Claim
17 words
A telephone exchange transmission bridge as claimed in claim 7, wherein said bridge is a capacitor bridge.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-05-08 | 1981-11-07 | 1982-05-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-05-08 | 1985-11-07 | 1986-05-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-05-08 | 1989-11-07 | 1990-05-09 | $7700.00 | Window Closed / Lapsed |