US4503289A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Line circuit with flux compensation and active impedance termination
Assignee: Nokia Bell Labs
•
Filing: 1983-01-17
•
Granted: 1985-03-05
•
Expires: 2003-01-17
Abstract
Abstract A telephone line circuit comprises a transformer that has a primary (13) and a secondary (14) winding. A low resistance (15) is connected in series with the primary winding. An amplifier circuit (17) is coupled across the resistance and serves to develop a predetermined dc control voltage. This control voltage is used to establish a dc current flow in the secondary which is n times that of any dc current flow in the primary, where n is the transformer turns ratio. The dc current flow established in the secondary is in a direction opposite that of the dc current flow in the primary. A second amplifier circuit (31, 36, 23) is coupled across the primary winding and serves to generate an ac control signal which is also delivered to the secondary winding to create a predetermined ac termination impedance.
Inventors
- 👤 Dewayne A. Spires
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 10:05
CPC Classifications
H; H04; H04M; H04M19/00; H04M19/001; H04M19/003
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
104 words
A circuit comprising a transformer (12) having a primary winding (13) and a secondary winding (14), a low resistance (15) connected in series with the primary, means (17) coupled to said resistance for developing a direct current control voltage, means (23) responsive to said control voltage for causing a direct flow in said secondary which serves to substantially cancel the flux induced in the transformer core by any direct current flow in the primary, and means (31-36, 23) coupled across the primary winding for developing an alternating current control signal which is delivered to said secondary to create a predetermined alternating current termination impedance.
Claim 2
Dependent Claim
104 words
A circuit comprising a transformer (12) having a primary winding (13) and a secondary winding (14), a low resistance (15) connected in series with the primary, means (17) coupled to said resistance for developing a direct current control voltage, means (23) responsive to said control voltage for causing a direct flow in said secondary which serves to substantially cancel the flux induced in the transformer core by any direct current flow in the primary, and means (31-36, 23) coupled across the primary winding for developing an alternating current control signal which is delivered to said secondary to create a predetermined alternating current termination impedance.
Claim 3
Dependent Claim
129 words
A telephone line circuit comprising a transformer (12) having a primary winding (13) and a secondary winding (14), a low resistance (15) connected in series with the primary, amplifier means (17) coupled to said resistance for developing a direct current control voltage, means (23) responsive to said control voltage for establishing a direct current flow in said secondary which is n times that of any direct current flow in said primary, where n is the transformer turns ratio, the direct current flow in said secondary being in a direction opposite that of any direct current flow in the primary, and means (31-36, 23) coupled across the primary winding for developing an alternating current control signal which is coupled to the secondary to create the proper alternating current termination impedance.
Claim 4
Dependent Claim
129 words
A telephone line circuit comprising a transformer (12) having a primary winding (13) and a secondary winding (14), a low resistance (15) connected in series with the primary, amplifier means (17) coupled to said resistance for developing a direct current control voltage, means (23) responsive to said control voltage for establishing a direct current flow in said secondary which is n times that of any direct current flow in said primary, where n is the transformer turns ratio, the direct current flow in said secondary being in a direction opposite that of any direct current flow in the primary, and means (31-36, 23) coupled across the primary winding for developing an alternating current control signal which is coupled to the secondary to create the proper alternating current termination impedance.
Claim 5
Dependent Claim
39 words
A telephone line circuit as defined in claim 2 including a resistance (25) connected in series with the secondary winding, and means (28, 29) coupling the voltage drop across the latter resistance to the input of the amplifier means.
Claim 6
Dependent Claim
27 words
A telephone line circuit as defined in claim 3 wherein the voltage drop across the latter resistance creates a null at the input of the amplifier means.
Claim 7
Dependent Claim
30 words
A telephone line circuit as defined in claim 4 wherein the direct current flow established in the secondary is 1.4 times that of any direct current flow in the primary.
Claim 8
Dependent Claim
110 words
A telephone line circuit as defined in claim 2 including a second resistance (25) connected in series with the secondary winding, a bridge circuit (18, 19, 28, 29), one side of said bridge circuit connecting a voltage drop across the first-recited resistance (15) to the input of the amplifier means, with the other side of said bridge circuit connecting a voltage drop across said second resistance to the input of the amplifier means, the amplifier means being connected across the mid-point of the bridge circuit, said second resistance being of a value such that the voltage drop across the same creates a null at the input of the amplifier means.
References Cited (Backward Citations)
US4096363A
Cited
US4241239A
Cited
US4182936A
Cited
US4321431A
Cited
US4243842A
Cited
US4319093A
Cited
US4387273A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-03-04 | 1988-09-03 | 1989-03-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-03-04 | 1992-09-03 | 1993-03-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-03-04 | 1996-09-03 | 1997-03-05 | $7700.00 | Window Closed / Lapsed |