EP0135843A2
Expired / Lapsed
EP
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Echo canceller systems
Assignee: NEC Corp
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Filing: 1984-08-31
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Granted: —
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Expires: 2004-08-31
Abstract
Abstract In an echo canceller system of the type comprising a circuit for measuring the characteristic of an echo path in accordance with input/output signals of the echo path and cancelling from an actual echo signal an approximate echo path signal synthesized in accordance with the echo characteristic, a level measuring circuit for measuring the level of the residual signal, a residual echo level estimating means for estimating the residual echo level based on the output of the level measuring circuit, and a comparator comparing the output of the residual echo level estimating means with the output of the residual echo level measuring circuit, the output of the comparator controlling the measuring operation of the echo path, there are provided a residual signal level measuring circuit including the residual signal level measuring circuit, a transmitted signal input level measuring circuit, and a detector for detecting an opened state of the echo path and producing an output which controls the residual signal level measuring unit.
Inventors
- 👤 Yukio C/O Nec Corporation Hagiwara
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 23:18
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20; H04B3/23; H04B3/234
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
164 words
An echo canceller system of the type comprising: an echo path; means for measuring a characteristic of the echo path in accordance with input/output signals of said echo path and cancelling from an actual echo signal an approximate echo path signal synthesized in accordance with the echo characteristic; a measuring circuit for measuring a level of a residual signal; residual echo level estimating means for estimating the residual echo level based on an output of said measuring circuit; and a comparator comparing an output of said residual echo level estimating means with an output of said residual echo level measuring circuit; an output of said comparator controlling a measuring operation of said echo path, characterized in that there are provided a residual signal level measuring unit including said residual signal level measuring circuit, a transmitted signal input level measuring circuit, and a detector for detecting an opened state of said echo path and producing an output which controls said residual signal level measuring unit.
Claim 2
Dependent Claim
164 words
An echo canceller system of the type comprising: an echo path; means for measuring a characteristic of the echo path in accordance with input/output signals of said echo path and cancelling from an actual echo signal an approximate echo path signal synthesized in accordance with the echo characteristic; a measuring circuit for measuring a level of a residual signal; residual echo level estimating means for estimating the residual echo level based on an output of said measuring circuit; and a comparator comparing an output of said residual echo level estimating means with an output of said residual echo level measuring circuit; an output of said comparator controlling a measuring operation of said echo path, characterized in that there are provided a residual signal level measuring unit including said residual signal level measuring circuit, a transmitted signal input level measuring circuit, and a detector for detecting an opened state of said echo path and producing an output which controls said residual signal level measuring unit.
Claim 3
Dependent Claim
58 words
The system according to claim 1 wherein said residual signal level measuring unit further comprises a switching circuit responsive to the output of said detector for detecting the opened state of said echo path to switch the echo path input signal or the output of said residual signal level measuring circuit to said residual echo level estimating means.
Claim 4
Dependent Claim
59 words
The system according to claim 1 wherein said residual signal level measuring unit further comprises a residual echo level subtractor responsive to the output of said detector for detecting the opened state of said echo path to decrease the output of said residual signal level measuring circuit and supply a decreased signal to said residual echo level estimating means.
Claim 5
Dependent Claim
170 words
An echo canceller system of the type comprising: an echo path; means for measuring a characteristic of the echo path in accordance with input/output signals of said echo path and cancelling from an actual echo signal an approximate echo path signal synthesized in accordance with the echo characteristic; a measuring circuit for measuring a level of a residual signal; residual echo level estimating means for estimating the residual echo level based on an output of said measuring circuit; and a comparator comparing an output of said residual echo level estimating means with an output of said residual echo level measuring circuit; an output of said comparator controlling a measurin operation of said echo path, characterized in that there are provided a transmitted signal input level measuring circuit, a detector for detecting an opened state of the echo path, and a double talk signal control circuit controlled by an output of said detector for detecting the opened state of the echo path so as to control the output of the comparator.
Claim 6
Dependent Claim
170 words
An echo canceller system of the type comprising: an echo path; means for measuring a characteristic of the echo path in accordance with input/output signals of said echo path and cancelling from an actual echo signal an approximate echo path signal synthesized in accordance with the echo characteristic; a measuring circuit for measuring a level of a residual signal; residual echo level estimating means for estimating the residual echo level based on an output of said measuring circuit; and a comparator comparing an output of said residual echo level estimating means with an output of said residual echo level measuring circuit; an output of said comparator controlling a measurin operation of said echo path, characterized in that there are provided a transmitted signal input level measuring circuit, a detector for detecting an opened state of the echo path, and a double talk signal control circuit controlled by an output of said detector for detecting the opened state of the echo path so as to control the output of the comparator.
References Cited (Backward Citations)
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