US3909552A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Conference call circuit for use in a key telephone system
Assignee: NEC Platforms Ltd
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Filing: 1973-10-09
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Granted: 1975-09-30
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Expires: 1993-10-09
Abstract
Abstract A circuit means is disclosed for use in a key telephone system permitting the connection of a key telephone set to a plurality of central office or PBX line circuit means through the key telephone set and without making a direct parallel connection between the central office or PBX line circuit means. Means are also disclosed permitting the connection, and disconnection of the central office or PBX line circuit means to the key telephone set without requiring the connection and disconnection of the line circuit means by the central office or PBX.
Inventors
- 👤 Stephen E Kerman
- 👤 Tsuyoshi Shinoi
- 👤 Tsutomu Kataoka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 21:40
CPC Classifications
H; H04; H04M; H04M3/00; H04M3/42; H04M3/56; H04M9/00; H04M9/002
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
241 words
A conference call circuit for use in a key telephone system having a plurality of central office line circuits and at least one key telephone set with a telephone speech network circuit, in which the system is adapted to connect to and hold a first line circuit means while connecting a second line circuit means to the key telephone speech network, the conference call circuit means comprising: a relay circuit means for connecting and disconnecting the speech network circuit of the key telephone to the second line circuit means, a relay control means for controlling the operation and release of the relay, comprising a non-locking key means in combination with a first semiconductor switching means responsive to said non-locking key means, and a second semiconductor switching means, responsive to the output of said first semiconductor switching means, the output of said second semiconductor switching means controlling the operation and release of the relay, said relay means having a plurality of contacts for connecting the key telephone set to the second line circuit means, said relay control means operating the relay means when the key means is depressed to contact a holding circuit means and a speech path circuit means to the second line circuit means, and said relay control means releasing the relay means when the key means is depressed a second time to disconnect the holding circuit means and the speech path circuit means from the second line circuit means.
Claim 2
Dependent Claim
241 words
A conference call circuit for use in a key telephone system having a plurality of central office line circuits and at least one key telephone set with a telephone speech network circuit, in which the system is adapted to connect to and hold a first line circuit means while connecting a second line circuit means to the key telephone speech network, the conference call circuit means comprising: a relay circuit means for connecting and disconnecting the speech network circuit of the key telephone to the second line circuit means, a relay control means for controlling the operation and release of the relay, comprising a non-locking key means in combination with a first semiconductor switching means responsive to said non-locking key means, and a second semiconductor switching means, responsive to the output of said first semiconductor switching means, the output of said second semiconductor switching means controlling the operation and release of the relay, said relay means having a plurality of contacts for connecting the key telephone set to the second line circuit means, said relay control means operating the relay means when the key means is depressed to contact a holding circuit means and a speech path circuit means to the second line circuit means, and said relay control means releasing the relay means when the key means is depressed a second time to disconnect the holding circuit means and the speech path circuit means from the second line circuit means.
Claim 3
Dependent Claim
48 words
A conference call circuit as in claim 1 further comprising means, responsive to the operation of a key switching means, for maintaining the connection between the key telephone set and the second line circuit means when the key telephone set is disconnected from the first line circuit means.
Claim 4
Dependent Claim
34 words
A conference call circuit as in claim 1 further comprising means responsive to the operation of a hookswitch means, for disconnecting the key telephone set from both said first and second line circuit means.
Claim 5
Dependent Claim
49 words
A conference call circuit as in claim 1 further comprising means responsive to the connection of the key telephone set to both said first and second line circuit means for indicating at all key telephones in the system the busy status of said first and second line circuit means.
Claim 6
Dependent Claim
51 words
A conference call circuit as in claim 1 wherein the first semiconductor switching means comprises a transistor switching circuit and a zener diode circuit, said zener diode conducting upon the operation of the non-locking key means and said transistor switching circuit switching in response to the conduction of said zener diode.
Claim 7
Dependent Claim
76 words
A conference call circuit as in claim 5 wherein said second semiconductor switching means is comprised of two transistor circuits arranged in a flip-flop circuit, and having said relay means connected to the collector of one of said transistor circuits, whereby the relay operates and releases in response to the conduction and non-conduction of said first transistor circuit, and said first transistor circuit conducts and stops conducting in response to the conduction of said zener diode.
Claim 8
Dependent Claim
63 words
A conference call circuit as in claim 5 further comprising circuit means connected to said relay circuit means And responsive to a signal from said second line circuit means indicative of the busy condition of said second line circuit means for preventing the operation of the relay circuit means when said second line circuit means is in use by another key telephone set.
Claim 9
Dependent Claim
58 words
A conference call circuit as in claim 7 wherein the means for preventing the operation of the relay circuit means is connected to the second semiconductor switching circuit, said second semiconductor circuit thereby being responsive to the busy condition of the line circuit means and preventing the operation of the relay when said line circuit means is busy.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-29 | 1979-03-31 | 1979-09-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-29 | 1983-03-31 | 1983-09-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-29 | 1987-03-31 | 1987-09-30 | $7700.00 | Window Closed / Lapsed |