US3757056A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Bipolar multiplexing circuit for telephone line selection
Assignee: Telecommunication Engineering Corp
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Filing: 1972-03-16
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Granted: 1973-09-04
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Expires: 1992-03-16
Abstract
Abstract A telephone is selectively connectable with any one of a plurality of central office lines through tree-connected relay circuits located in a remote control box. Line selection switches located at the telephone operate the relay circuits over control leads, each lead being adapted for two functions by a pair of branch circuits with rectifiers connected to the lead at each end.
Inventors
- 👤 J Foulkes
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 13:49
CPC Classifications
H; H04; H04Q; H04Q3/00; H04M; H04M9/00; H04M9/002; H04M9/005; H04M9/007
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
237 words
Telephone line selection means including, in combination, a control unit having connections for a plurality of external line pairs, a ring terminal, a tip terminal, selector means including a plurality of relays and tree-connected contacts actuated by the relays, said contacts being adapted to cause a selected external line pair to be connected with the tip and ring terminals upon energization of a predetermined combination of the relays, and an energizing circuit electrically isolated from the external line pairs and tree-connected contacts and including connections to a source of alternating current, a common lead, a control lead, and a first pair of parallel circuits each including a current direction discriminator and one of said relays and completing a connection between the common lead and the conTrol lead through the source, the current direction discriminators being oppositely directed in said parallel circuits, and a telephone connected to the control unit by a cable, said cable including a talking pair connected with said ring and tip terminals and said common and control leads, said telephone including means electrically isolated from said talking pair and including a pair of independently operable line selection contacts and a second pair of parallel circuits each including a current direction discriminator and one of said line selection contacts and completing a connection between the common lead and the control lead, the current direction discriminators in the second pair of parallel circuits being oppositely directed.
Claim 2
Dependent Claim
237 words
Telephone line selection means including, in combination, a control unit having connections for a plurality of external line pairs, a ring terminal, a tip terminal, selector means including a plurality of relays and tree-connected contacts actuated by the relays, said contacts being adapted to cause a selected external line pair to be connected with the tip and ring terminals upon energization of a predetermined combination of the relays, and an energizing circuit electrically isolated from the external line pairs and tree-connected contacts and including connections to a source of alternating current, a common lead, a control lead, and a first pair of parallel circuits each including a current direction discriminator and one of said relays and completing a connection between the common lead and the conTrol lead through the source, the current direction discriminators being oppositely directed in said parallel circuits, and a telephone connected to the control unit by a cable, said cable including a talking pair connected with said ring and tip terminals and said common and control leads, said telephone including means electrically isolated from said talking pair and including a pair of independently operable line selection contacts and a second pair of parallel circuits each including a current direction discriminator and one of said line selection contacts and completing a connection between the common lead and the control lead, the current direction discriminators in the second pair of parallel circuits being oppositely directed.
Claim 3
Dependent Claim
245 words
Telephone line selection means including, in combination, a control unit having connections for a plurality of external line pairs, a ring terminal, a tip terminal, selector means including a plurality of relays and tree-connected contacts actuated by the relays, said contacts being adapted to cause a selected external line pair to be connected with the tip and ring terminals upon energization of a predetermined combination of the relays, and an energizing circuit electrically isolated from the external line pairs and tree-connected contacts and including connections to a source of alternating current, a common lead, a control lead, and a first pair of parallel circuits each including a current direction discriminator and at least one of which includes one of said relays, each of said parallel circuits completing a connection between the common lead and the control lead through the source, the current direction discriminators being oppositely directed in said parallel circuits, and a telephone connected to the control unit by a cable, said cable including a talking pair connected with said ring and tip terminals and said common and control leads, said telephone including means electrically isolated from said talking pair and including a pair of independently operable selection contacts and a second pair of parallel circuits each including a current direction discriminator and one of said selection contacts and completing a connection between the common lead and the control lead, the current direction discriminators in the second pair of parallel circuits being oppositely directed.
Claim 4
Dependent Claim
245 words
Telephone line selection means including, in combination, a control unit having connections for a plurality of external line pairs, a ring terminal, a tip terminal, selector means including a plurality of relays and tree-connected contacts actuated by the relays, said contacts being adapted to cause a selected external line pair to be connected with the tip and ring terminals upon energization of a predetermined combination of the relays, and an energizing circuit electrically isolated from the external line pairs and tree-connected contacts and including connections to a source of alternating current, a common lead, a control lead, and a first pair of parallel circuits each including a current direction discriminator and at least one of which includes one of said relays, each of said parallel circuits completing a connection between the common lead and the control lead through the source, the current direction discriminators being oppositely directed in said parallel circuits, and a telephone connected to the control unit by a cable, said cable including a talking pair connected with said ring and tip terminals and said common and control leads, said telephone including means electrically isolated from said talking pair and including a pair of independently operable selection contacts and a second pair of parallel circuits each including a current direction discriminator and one of said selection contacts and completing a connection between the common lead and the control lead, the current direction discriminators in the second pair of parallel circuits being oppositely directed.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-09-03 | 1977-03-05 | 1977-09-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-03 | 1981-03-05 | 1981-09-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-03 | 1985-03-05 | 1985-09-04 | $7700.00 | Window Closed / Lapsed |