US3900708A
Expired / Lapsed
US
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Selective echo suppressor
Assignee: Siemens AG
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Filing: 1973-04-05
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Granted: 1975-08-19
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Expires: 1993-04-05
Abstract
Abstract Selective echo suppression is provided in a four-wire transmission system. The voice frequency band is divided into a plurality of partial frequency ranges and the transmission of an echo in a partial frequency range is controlled by the reception of signals within that partial frequency range on the receiving side of an echo suppressor. Resetting of suppression is delayed for a time corresponding to the transit time of an echo between the distant end of a four-wire telephone connection. Speech clipping upon initial speech, or upon interruptions by the other party, are eliminated or minimized.
Inventors
- 👤 Hermann Bendel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 16:12
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20; H04B3/21
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
251 words
An echo suppressor for a speaking circuit of a fourwire transmission system having a transmitting path and a receiving path, comprising: a set of first filters connected in said transmitting path; a plurality of continuously controllable regulating means each of which is connected to and associated with a respective first filter to control signal passage therethrough; a set of second filters connected to said receiving path, each of said second filters having a partial frequency range covering a separate portion of the total frequency range of said second filters, and each of said first filters having a partial frequency range corresponding to that of a separate second filter; a plurality of signal evaluation elements each of which is connected between a respective second filter and the regulating means associated with its corresponding first filter and operable to control signal passage through said corresponding first filter in accordance with the level of speech signals in said receiving path which are within the corresponding partial frequency range; means for establishing an operation threshold for said plurality of evaluation elements, whereby attenuation is controlled in the respective partial frequency ranges proportionally with respect to signal levels above said threshold at the outputs of the respective second filters; and a speech detector connected to and controlled from the receiving path and a transfer device connected to said transmitting path and connected to and controlled by said speech detector to bridge and bypass said first filters if no speech signal is present in the receiving path.
Claim 2
Dependent Claim
251 words
An echo suppressor for a speaking circuit of a fourwire transmission system having a transmitting path and a receiving path, comprising: a set of first filters connected in said transmitting path; a plurality of continuously controllable regulating means each of which is connected to and associated with a respective first filter to control signal passage therethrough; a set of second filters connected to said receiving path, each of said second filters having a partial frequency range covering a separate portion of the total frequency range of said second filters, and each of said first filters having a partial frequency range corresponding to that of a separate second filter; a plurality of signal evaluation elements each of which is connected between a respective second filter and the regulating means associated with its corresponding first filter and operable to control signal passage through said corresponding first filter in accordance with the level of speech signals in said receiving path which are within the corresponding partial frequency range; means for establishing an operation threshold for said plurality of evaluation elements, whereby attenuation is controlled in the respective partial frequency ranges proportionally with respect to signal levels above said threshold at the outputs of the respective second filters; and a speech detector connected to and controlled from the receiving path and a transfer device connected to said transmitting path and connected to and controlled by said speech detector to bridge and bypass said first filters if no speech signal is present in the receiving path.
Claim 3
Dependent Claim
26 words
An echo suppressor according to claim 1, wherein parallel-connected band pass filters are provided as said first filters having the respective regulating means connected in series.
Claim 4
Dependent Claim
31 words
An echo suppressor according to claim 2, wherein the first band pass filters are dimensioned in a way that they have a lower band width than the second band pass filters.
Claim 5
Dependent Claim
31 words
An echo suppressor according to claim 2, wherein the pass band characteristics of said first filters are dimensioned to have greater steepress than the pass band characteristics of said second filters.
Claim 6
Dependent Claim
108 words
An echo suppressor according to claim 2, comprising a comparing device for each paRtial frequency range each connected to and controlled by the output signal of the respective band pass filter of the first filters and the output signal of the respective band pass filter of the second filters for adjusting the regulating means for the same partial frequency band to a lower absorption during the time when the output level of the band pass filter of the first filters exceeds the output level of the respective band pass filter of the second filters or if it exceeds the other level which lies a certain given difference lower.
Claim 7
Dependent Claim
26 words
An echo suppressor according to claim 1, wherein series-connected band suppressors are provided as said first filters having the respective regulating means connected in parallel therewith.
Claim 8
Dependent Claim
30 words
An echo suppressor according to claim 6, wherein each band suppressor includes several band suppressor elements with nearly the same suppression range, having a partial regulating means connected parallel thereto.
Claim 9
Dependent Claim
38 words
An echo suppressor according to claim 1, wherein the partial frequency ranges overlap and the second band pass filters are dimensioned in a way that their attenuation is small in the overlapping areas of the partial frequency ranges.
Claim 10
Dependent Claim
88 words
An echo suppressor according to claim 1, comprising a second plurality of evaluation elements in said transmitting path, and wherein each of said evaluation elements has a delay such that the reset of the attenuation in the respective partial frequency bands of the first filters is delayed for a hold-over time which is at least as great as the transit time of the echo signal from the branching point of the receiving path for the second filters to said second plurality of evaluation elements in the transmitting path.
Claim 11
Dependent Claim
45 words
An echo suppressor according to claim 1, wherein the evaluation elements are dimensioned in a way that the reset of the attenuation in the respective partial frequency bands of the first filters during the hold-over time has an essentially higher magnitude than the hold-over time.
Claim 12
Dependent Claim
47 words
An echo suppressor according to claim 10, wherein each said comparing device is operable to adjust the corresponding regulating means to smaller or minimum attenuation, excluding the hold-over time, during the time when the output signal of the corresponding band pass of the first filters is dominant.
Claim 13
Dependent Claim
77 words
An echo suppressor according to claim 1, wherein said transfer device is dimensioned in a way that the inserting of the first filters is effected very fast and the inserting of the bridging line is effected delayed at least for that time which corresponds to the transmission time of the echo signal from the connection point of said speech detector to the receiving path up to the connection point of said transfer device in the transmitting path.
Claim 14
Dependent Claim
41 words
An echo suppressor according to claim 12 comprising an evaluation device connected to said second filters, and wherein said transfer device is controlled by said evaluation device which evaluates the levels in the individual partial frequency bands of the receiving path.
Claim 15
Dependent Claim
17 words
An echo suppressor according to claim 1, wherein said second filters are connected into the receiving path.
Claim 16
Dependent Claim
37 words
An echo suppressor according to claim 14, wherein each of the filters second set of filters has a switching element connected in series which is controlled by the respective evaluation element of the same partial frequency band.
Claim 17
Dependent Claim
42 words
An echo suppressor according to claim 1, comprising a delay element connected into the path of the echo signal between the branch point of the receiving path for the second filters and said second pluraliy of evaluation elements in the transmission path.
Claim 18
Dependent Claim
57 words
An echo suppressor according to claim 16, wherein said delay element is dimensioned in a way that the transit time of the echo signal between the branch point of the receiving path for the second filters and the evaluation elements in the transmitting path is at least as long as the reaction time of the evaluation elements.
Claim 19
Dependent Claim
22 words
An echo suppressor according to claim 16, wherein said delay element is at least partly constituted by means of said first filters.
Claim 20
Dependent Claim
24 words
An echo suppressor according to claim 16, characterized in that said delay element is a delay line which is connected into the receiving path.
Claim 21
Dependent Claim
19 words
An echo suppressor according to claim 16, characterized in that said delay element is connected into the transmitting path.
Claim 22
Dependent Claim
66 words
An echo suppressor according to claim 19, wherein said delay element is a further switching device which is connected ahead of said first filters and which is controlled by said speech detector to interrupt the signal path of the first filters when a speech signal disappears in the receiving path and to connect the signal path delayedly when the speech signal starts in the receiving path.
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) | 1978-08-18 | 1979-02-17 | 1979-08-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-18 | 1983-02-17 | 1983-08-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-18 | 1987-02-17 | 1987-08-19 | $7700.00 | Window Closed / Lapsed |