Patent US3899641A successfully refreshed from Google Patents.
US3899641A
Expired / Lapsed
US
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Four-wire backup facility using DDD lines
Assignee: AT&T Inc
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Filing: 1974-03-04
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Granted: 1975-08-12
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Expires: 1994-03-04
Abstract
Abstract A pair of two-wire DDD lines are used as automatically switched backup for a four-wire private line data link from a central station to a remote station. Transfer to the backup facility is effected automatically at the remote station upon detection of failure of the four-wire link, provided the two DDD lines are dialed-up in a predetermined sequence within a predetermined time of each other. This precludes accidental or unwanted transfer to the backup DDD lines upon momentary failure of the four-wire link or upon improper (e.g., wrong number) incoming calls on the DDD lines.
Inventors
- 👤 Richard Henry Etra
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 13:50
CPC Classifications
H; H04; H04Q; H04Q3/00; H04Q3/0016; H04B; H04B1/00; H04B1/74
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
75 words
Backup facilities for a station normally connected to a fourwire Transmission line, said backup facilities using a pair of two-wire transmission lines and comprising, switching means operable for disconnecting said station from said four-wire line and connecting said station to said pair of two-wire lines, and means operative only upon failure of said four-wire line for operating said switching means automatically in response to a predetermined sequence of signals on said pair of two-wire lines.
Claim 2
Dependent Claim
75 words
Backup facilities for a station normally connected to a fourwire Transmission line, said backup facilities using a pair of two-wire transmission lines and comprising, switching means operable for disconnecting said station from said four-wire line and connecting said station to said pair of two-wire lines, and means operative only upon failure of said four-wire line for operating said switching means automatically in response to a predetermined sequence of signals on said pair of two-wire lines.
Claim 3
Dependent Claim
46 words
Backup facilities in accordance with claim 1 wherein said circuit means includes means operative for detecting a first signal on one of said two-wire lines and, responsive to detection of said first signal, operative for detecting a second signal on the other of said two-wire lines.
Claim 4
Dependent Claim
49 words
Backup facilities in accordance with claim 2 wherein said circuit means further includes means responsive to detection of said first signal for defining a fixed interval of time, and means for operating said switching means in response to detection of said second signal within said fixed interval of time.
Claim 5
Dependent Claim
84 words
Backup facilities in accordance with claim 1 wherein said circuit means comprises means operative upon failure of said four-wire line for detecting a first predetermined signal on one of said two-wire lines, means responsive to detection of said first predetermined signal for defining a fixed interval of time, means operative during said fixed interval of time for detecting a second predetermined signal on the other of said two-wire lines, and means responsive to detection of said second predetermined signal for operating said switching means.
Claim 6
Dependent Claim
94 words
A switching circuit comprising first and second input paths, an output path normally connected to said first input path, means for providing an indication of failure of said first input path, means enabled responsive to said failure indication for detecting predetermined signals on said second input path, switching means operative for disconnecting said first input path from said output path and for connecting said output path to said second input path, and means including said detecting means for operating said switching means responsive to detection of said predetermined signals on said second input path.
Claim 7
Dependent Claim
94 words
A switching circuit comprising first and second input paths, an output path normally connected to said first input path, means for providing an indication of failure of said first input path, means enabled responsive to said failure indication for detecting predetermined signals on said second input path, switching means operative for disconnecting said first input path from said output path and for connecting said output path to said second input path, and means including said detecting means for operating said switching means responsive to detection of said predetermined signals on said second input path.
Claim 8
Dependent Claim
80 words
A switching circuit in accordance with claim 5 wherein said second input path includes at least two lines, and wherein said detecting means includes a signal detector, means responsive to said failure indication for connecting said signal detector to one of said two lines, and means responsive to the detection of a predetermined signal on said one line for disconnecting said signal detector from said one line and for connecting said signal detector to the other of said two lines.
Claim 9
Dependent Claim
34 words
A switching circuit in accordance with claim 6 wherein said operating means includes means responsive to detection of said predetermined signal on said one line for defining the beginning of a predetermined time frame.
Claim 10
Dependent Claim
54 words
A switching circuit in accordance with claim 7 wherein said operating means further includes means responsive to said defining means for establishing a predetermined time frame, and wherein said operating means operate said switching means responsive to detection of a predetermined signal on the other of said two lines within said predetermined time frame.
Claim 11
Dependent Claim
33 words
A switching circuit in accordance with claim 7 wherein said operating means further includes means responsive to the termination of said predetermined time frame for disconnecting said signal detector from said other line.
Claim 12
Dependent Claim
75 words
A switching circuit operable for connecting a four-wire station set to a pair of two-wire lines comprising means for detecting a first signal on a predetermined one of said two-wire lines, means for detecting a second signal on the other of said two-wire lines, and control means for operating the switching circuit only in response to detection of said first and second signals in a predetermined sequence and within a predetermined time of one another.
Claim 13
Dependent Claim
75 words
A switching circuit operable for connecting a four-wire station set to a pair of two-wire lines comprising means for detecting a first signal on a predetermined one of said two-wire lines, means for detecting a second signal on the other of said two-wire lines, and control means for operating the switching circuit only in response to detection of said first and second signals in a predetermined sequence and within a predetermined time of one another.
Claim 14
Independent Claim
91 words
The method of using a pair of two-wire transmission lines for providing four-wire transmission facilities for a station comprising the steps of, enabling the detection of a predetermined signal on one of said two-wire transmission lines, defining a predetermined interval of time responsive to detection of said predetermined signal on said one line, detecting a predetermined signal on the other of said two-wire transmission lines, and connecting said station to said pair of lines responsive to detection of said predetermined signal on said other line within said predetermined interval of time.
Claim 15
Independent Claim
91 words
The method of using a pair of two-wire transmission lines for providing four-wire transmission facilities for a station comprising the steps of, enabling the detection of a predetermined signal on one of said two-wire transmission lines, defining a predetermined interval of time responsive to detection of said predetermined signal on said one line, detecting a predetermined signal on the other of said two-wire transmission lines, and connecting said station to said pair of lines responsive to detection of said predetermined signal on said other line within said predetermined interval of time.
References Cited (Backward Citations)
US3001027A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-08-11 | 1979-02-10 | 1979-08-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-11 | 1983-02-10 | 1983-08-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-11 | 1987-02-10 | 1987-08-12 | $7700.00 | Window Closed / Lapsed |