US3778554A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Single three-wire-port pbx intercom trunk circuit arrangement
Assignee: AT&T Inc
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Filing: 1971-05-24
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Granted: 1973-12-11
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Expires: 1991-05-24
Abstract
Abstract A single three-wire-port PBX intercom trunk circuit supplies battery, ringing, and supervision through a switching network from the trunk circuit to a pair of interconnected stations. The intercom trunk circuit and line circuits of the stations are arranged to provide all essential controls for the calling and called stations. Interconnections from the intercom trunk circuit to the stations are arranged so that talking current conducted to any one station is substantially independent of the loop resistance of any other station to which the one station is connected.
Inventors
- 👤 D Weiner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 14:05
CPC Classifications
H; H04; H04M; H04M7/00; H04M7/0096
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
118 words
A telephone system comprising first and second stations having tip and ring leads, a trunk circuit for providing a talking current power supply and ground return, first means connecting the talking current power supply from the trunk circuit to the tip lead of the first station for conducting talking current to the first station, second means, exclusive of the first means, connecting the talking current power supply from the trunk circuit to the tip lead of the second station for conducting talking current to the second station, and means connecting the ring leads of the first and second stations in common to the ground return for conducting the talking current of the first and second stations to ground.
Claim 2
Dependent Claim
118 words
A telephone system comprising first and second stations having tip and ring leads, a trunk circuit for providing a talking current power supply and ground return, first means connecting the talking current power supply from the trunk circuit to the tip lead of the first station for conducting talking current to the first station, second means, exclusive of the first means, connecting the talking current power supply from the trunk circuit to the tip lead of the second station for conducting talking current to the second station, and means connecting the ring leads of the first and second stations in common to the ground return for conducting the talking current of the first and second stations to ground.
Claim 3
Dependent Claim
62 words
A system in accordance with claim 1 wherein the first means comprise a first path through a switching network and through a first line circuit, the second means comprise a second path through the switching network and through a second line circuit, and the first and second line circuits respectively including unoperated and operated relays for completing the first and second paths.
Claim 4
Dependent Claim
65 words
A system in accordance with claim 2 wherein magnitude of the talking current in the first path is substantially independent of a loop resistance of the second path from the trunk circuit to the second station, and magnitude of the talking current in the second path is substantially independent of a loop resistance of the first path from the trunk circuit to the first station.
Claim 5
Dependent Claim
165 words
In a telephone system a telephone station having tip and ring leads, a trunk circuit supplying suppluing talking battery at first and second terminals and for providing a ground return through a third terminal, a switching network having first, second, and third leads, each including a first end connected to the first, second, and third terminals respectively, means for connecting the ring lead to a second end of the third lead when the station originates a call and when the station receives a call, means for connecting the tip lead to a second end of the first lead when the station originates a call, the second lead concurrently providing a signal for holding the means for connecting the tip lead to the first lead, and means for connecting the tip lead to a second end of the second lead when the station receives a call, the first lead concurrently providing a signal for holding the means for connecting the tip lead to the second lead.
Claim 6
Dependent Claim
165 words
In a telephone system a telephone station having tip and ring leads, a trunk circuit supplying suppluing talking battery at first and second terminals and for providing a ground return through a third terminal, a switching network having first, second, and third leads, each including a first end connected to the first, second, and third terminals respectively, means for connecting the ring lead to a second end of the third lead when the station originates a call and when the station receives a call, means for connecting the tip lead to a second end of the first lead when the station originates a call, the second lead concurrently providing a signal for holding the means for connecting the tip lead to the first lead, and means for connecting the tip lead to a second end of the second lead when the station receives a call, the first lead concurrently providing a signal for holding the means for connecting the tip lead to the second lead.
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) | 1976-12-10 | 1977-06-11 | 1977-12-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-10 | 1981-06-11 | 1981-12-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-10 | 1985-06-11 | 1985-12-11 | $7700.00 | Window Closed / Lapsed |