Patent US2171542A successfully refreshed from Google Patents.
US4598172A
Expired / Lapsed
US
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Telecommunication terminal
Assignee: Telefonaktiebolaget LM Ericsson AB
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Filing: 1984-01-13
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Granted: 1986-07-01
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Expires: 2004-01-13
Abstract
Abstract Telecommunication terminal with automatic switching from 4-wire to 2-wire operation. The terminal is provided with a voltage sensing circuit (5) sensing the way in which DC voltage is fed to the terminal, and in repsonse therto controlling switches (8,11) which switch the terminal to prevailing operation conditions.
Inventors
- 👤 Erik A. Eriksson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 04:02
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/38; H04B1/40; H04B1/54; H04B1/58
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
217 words
In a telecommunication terminal including a transmitter and a receiver and having first and second sets of wire terminals connectable to telecommunication wires for four-wire operation and only said first set is used for two-wire operation, the kind of operation being determined by the value of DC voltages received by the wire terminals from the telecommunication wires, apparatus for controlling the telecommunication terminal to operate in four-wire operation or two-wire operation in accordance with the values of the DC voltages present at the wire terminals, said apparatus comprising first and second transformers each having a center-tapped primary winding connected to a different one of said sets of wire terminals and a secondary winding, a DC voltage sensing means having first and second inputs connected to the centertaps of said first and second transformers, respectively, said DC voltage sensing means generating first and second control signals in accordance with the levels of signals present at said first and second inputs and first switch means responsive to said first control signal for operatively connecting the transmitter to the secondary winding of said first transformer and the receiver to the secondary winding of said second transformer and being responsive to said second control signal for operatively connecting the transmitter and receiver only to the secondary winding of said first transformer.
Claim 2
Dependent Claim
217 words
In a telecommunication terminal including a transmitter and a receiver and having first and second sets of wire terminals connectable to telecommunication wires for four-wire operation and only said first set is used for two-wire operation, the kind of operation being determined by the value of DC voltages received by the wire terminals from the telecommunication wires, apparatus for controlling the telecommunication terminal to operate in four-wire operation or two-wire operation in accordance with the values of the DC voltages present at the wire terminals, said apparatus comprising first and second transformers each having a center-tapped primary winding connected to a different one of said sets of wire terminals and a secondary winding, a DC voltage sensing means having first and second inputs connected to the centertaps of said first and second transformers, respectively, said DC voltage sensing means generating first and second control signals in accordance with the levels of signals present at said first and second inputs and first switch means responsive to said first control signal for operatively connecting the transmitter to the secondary winding of said first transformer and the receiver to the secondary winding of said second transformer and being responsive to said second control signal for operatively connecting the transmitter and receiver only to the secondary winding of said first transformer.
Claim 3
Dependent Claim
29 words
The apparatus of claim 1 further comprising second switch means responsive to said first and second control signals for controlling the mode of operation of the transmitter and receiver.
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) | 1989-06-30 | 1989-12-30 | 1990-07-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-06-30 | 1993-12-30 | 1994-07-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-06-30 | 1997-12-30 | 1998-07-01 | $7700.00 | Window Closed / Lapsed |