US4024349A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Quasi-resonant transfer conferencing circuit
Assignee: AT&T Inc
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Filing: 1976-04-22
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Granted: 1977-05-17
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Expires: 1996-04-22
Abstract
Abstract A conference port for permitting simultaneous voice communication among a plurality of local stations and an external or central office line is shown. The stations may be part of a time division PBX or may be arranged as a time-sampled key telephone system having access to the same line. The conference port includes a first operational amplifier for summing the station port voltages on a capacitor during an interval that is a predetermined fraction of the resonant transfer interval. This first, or quasi-resonant, interval is sufficient to reduce the initial voltage on each of the station port sampling capacitors to a predetermined fraction of their initial level. At the conclusion of this interval the voltage on the summing capacitor in the conference port is multiplied by an appropriate factor in a second operational amplifier and is applied back simultaneously to all of the conference ports together with the signal incoming over the external or central office line. The voltage impulse, so applied, causes the signal contributed by each station port to appear at each other station port attenuated by a suitable factor, illustratively 6dB, while the incoming signal appears full strength at each station port. Accordingly, good return loss is provided at each station port and contrast between signals from stations and the incoming line is reduced via the controllable station-to-station loss.
Inventors
- 👤 John Francis O'Neill
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 19:24
CPC Classifications
H; H04; H04M; H04M3/00; H04M3/42; H04M3/56; H04M3/568; H04J; H04J3/00; H04J3/20; H04M3/561
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
97 words
A conference port for a telephone switching system including a plurality of station ports each having a resonant transfer sampling circuit, said conference port comprising: a capacitor and first summing amplifier means for applying to said capacitor during a first time interval lasting a predetermined fraction of the normal resonant transfer interval summation voltage samples from all said station ports; and second summing amplifier means for returning to all of said station ports during a second time interval having a longer duration than said first time interval a predetermined fraction of the summation voltage on said capacitor.
Claim 2
Dependent Claim
97 words
A conference port for a telephone switching system including a plurality of station ports each having a resonant transfer sampling circuit, said conference port comprising: a capacitor and first summing amplifier means for applying to said capacitor during a first time interval lasting a predetermined fraction of the normal resonant transfer interval summation voltage samples from all said station ports; and second summing amplifier means for returning to all of said station ports during a second time interval having a longer duration than said first time interval a predetermined fraction of the summation voltage on said capacitor.
Claim 3
Dependent Claim
66 words
A conference port according to claim 1 wherein said first summing amplifier means includes a summing amplifier and a pair of first sampling switches, said sampling switches being connected between the input to and the output of said summing amplifier and said capacitor, and the input of said amplifier being connectable in common to all of said station ports via one of said first sampling switches.
Claim 4
Dependent Claim
62 words
A conference port according to claim 2 further including a terminal for an external line, and wherein said second summing amplifier means includes a differential amplifier and a second sampling switch connected at the output of said amplifier, one of the inputs of said differential amplifier being connected to said capacitor and the other of its inputs being connected to said terminal.
Claim 5
Dependent Claim
71 words
A conference port according to claim 1 wherein said first summing amplifier means includes a summing amplifier and a pair of first switches for connecting said amplifier means includes a differential amplifier, an input terminal for an external line, said capacitor and said input terminal being connected to the differential inputs of said differential amplifier, and a second switch for connecting the output of said differential amplifier to said station ports.
Claim 6
Dependent Claim
141 words
A telephone switching system comprising: a communications bus, a plurality of station ports each having a resonant transfer sampling circuit connectable to said communications bus, a common port circuit having a summing capacitor, a summing amplifier, a pair of first switches for connecting said summing amplifier between said bus and said summing capacitor, a differential amplifier having one of its inputs connected to said summing capacitor, a terminal for an external line connected to the other input of said differential amplifier, a second switch for connecting said differential amplifier to said bus; and a clock circuit means for controlling the connection of said pair of common port switches to said communications bus throughout the continuance of a first quasi-resonant transfer interval and for controlling the connection of said second switch to said common bus during a second, full resonant transfer interval.
Claim 7
Dependent Claim
141 words
A telephone switching system comprising: a communications bus, a plurality of station ports each having a resonant transfer sampling circuit connectable to said communications bus, a common port circuit having a summing capacitor, a summing amplifier, a pair of first switches for connecting said summing amplifier between said bus and said summing capacitor, a differential amplifier having one of its inputs connected to said summing capacitor, a terminal for an external line connected to the other input of said differential amplifier, a second switch for connecting said differential amplifier to said bus; and a clock circuit means for controlling the connection of said pair of common port switches to said communications bus throughout the continuance of a first quasi-resonant transfer interval and for controlling the connection of said second switch to said common bus during a second, full resonant transfer interval.
Claim 8
Dependent Claim
165 words
A time division switching system comprising a plurality of station ports each having a resonant transfer sampling circuit capable of exhibiting an instantaneous voltage corresponding to a local speech signal, a communications bus, a conference port circuit having an external line connected thereto capable of exhibiting an instantaneous voltage corresponding to an incoming speech signal, and means for simultaneously controlling all of the time division sampling switches in said plurality of said station ports and a first time division switch in said conference port during an interval less than a resonant transfer interval to reduce the voltage sample on each of said station port resonant transfer sampling circuits by a predetermined factor and for operating a second time division sampling switch in said conference port circuit to reapply simultaneously to all of said station port circuits a predetermined fraction of the voltage corresponding to the charge passed through said first conference port switch together with a sample of said incoming signal on said external line.
Claim 9
Dependent Claim
165 words
A time division switching system comprising a plurality of station ports each having a resonant transfer sampling circuit capable of exhibiting an instantaneous voltage corresponding to a local speech signal, a communications bus, a conference port circuit having an external line connected thereto capable of exhibiting an instantaneous voltage corresponding to an incoming speech signal, and means for simultaneously controlling all of the time division sampling switches in said plurality of said station ports and a first time division switch in said conference port during an interval less than a resonant transfer interval to reduce the voltage sample on each of said station port resonant transfer sampling circuits by a predetermined factor and for operating a second time division sampling switch in said conference port circuit to reapply simultaneously to all of said station port circuits a predetermined fraction of the voltage corresponding to the charge passed through said first conference port switch together with a sample of said incoming signal on said external line.
Claim 10
Dependent Claim
98 words
A conference port for a telephone switching system including an external line and a plurality of station ports, each of said ports having a resonant transfer sampling circuit and being connected to a common bus, the conference port comprising: a summing capacitor, a first operational amplifier having a first input connected to the common bus, a second input connected to ground and an output connected to said summing capacitor, and a second operational amplifier having a first input connected to said summing capacitor, a second input connected to external line, and an output connected to said common bus.
Claim 11
Dependent Claim
98 words
A conference port for a telephone switching system including an external line and a plurality of station ports, each of said ports having a resonant transfer sampling circuit and being connected to a common bus, the conference port comprising: a summing capacitor, a first operational amplifier having a first input connected to the common bus, a second input connected to ground and an output connected to said summing capacitor, and a second operational amplifier having a first input connected to said summing capacitor, a second input connected to external line, and an output connected to said common bus.
Claim 12
Dependent Claim
70 words
A conference port in accordance with claim 7 further comprising first means for connecting said common bus to said summing capacitor through said first operational amplifier for an interval of 1/3 pi radians at the resonant transfer frequency of the sampling circuits, and second means for connecting said summing capacitor to the common bus through said second operational amplifier for an interval of pi radians at said resonant transfer frequency.
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) | 1980-05-16 | 1980-11-15 | 1981-05-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-05-16 | 1984-11-15 | 1985-05-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-05-16 | 1988-11-15 | 1989-05-17 | $7700.00 | Window Closed / Lapsed |