US4123626A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Digital echo attenuation circuit for a telephone system
Assignee: Nortel Networks Ltd
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Filing: 1977-11-23
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Granted: 1978-10-31
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Expires: 1997-11-23
Abstract
Abstract A digital echo attenuation circuit for a two-wire-four-wire local telephone circuit in which each digital sample of the transmit and receive signals is compared directly and the results used to augment an accumulator. Once the accumulator reaches a certain threshold level, its output controls a digital pad to attenuate the receive signal and thereby prevent severe distortion and near singing effects.
Inventors
- 👤 Ernst A. Munter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 11:51
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
165 words
In a telephone system having a two-wire analog transmission path coupled to a four-wire digital transmission path via a hybrid network interposed A/D and D/A converters in the four-wire path; a voice controlled digital echo attenuation circuit comprising: a comparator for comparing a sample of n-bits of each m-bit encoded word of tramsmit and receive pulse code modulated signals in the four-wire path to derive an output signal having a first or a second characteristic when the transmitted signal code is respectively not less than or less than the received signal code; a L-bit up/down counter, having a maximum non-overflow store of (2 L - 1) that is incremented or decremented by said output signal of the first or of the second characteristic respectively; a digital attenuator responsive to the output of the up/down counter for attenuating the receive pulse code modulated signal in the four-wire path wherein said output is generated only when the store in the counter is at least 2.sup.(L - 1).
Claim 2
Dependent Claim
165 words
In a telephone system having a two-wire analog transmission path coupled to a four-wire digital transmission path via a hybrid network interposed A/D and D/A converters in the four-wire path; a voice controlled digital echo attenuation circuit comprising: a comparator for comparing a sample of n-bits of each m-bit encoded word of tramsmit and receive pulse code modulated signals in the four-wire path to derive an output signal having a first or a second characteristic when the transmitted signal code is respectively not less than or less than the received signal code; a L-bit up/down counter, having a maximum non-overflow store of (2 L - 1) that is incremented or decremented by said output signal of the first or of the second characteristic respectively; a digital attenuator responsive to the output of the up/down counter for attenuating the receive pulse code modulated signal in the four-wire path wherein said output is generated only when the store in the counter is at least 2.sup.(L - 1).
Claim 3
Dependent Claim
34 words
A voice controlled digital echo attenuation circuit as defined in claim 1 in which the digital signals in the four-wire path are serial, and are coupled in parallel to the comparator via serial-parallel converters.
Claim 4
Dependent Claim
51 words
A voice controlled digital echo attenuation circuit as defined in claim 2 in which n = 4, m = 7, L = 8; the output signal from the comparator increments or decrements the up/down counter by 1; and the attenuation of the digital signal through the digital attenuator is about 6dB.
Claim 5
Dependent Claim
31 words
A voice controlled digital echo attenuation circuit as defined in claim 1 in which the digital signal from the attenuator when selected in the receive path, is coupled to the comparator.
Claim 6
Dependent Claim
29 words
A voice controlled digital echo attenuation circuit as defined in claim 1 in which the digital signal to the attenuator in the receive path is coupled to the comparator.
Claim 7
Dependent Claim
126 words
A digital echo attenuation circuit for a telephone system comprising: a comparator for comparing at least some of the most significant bits of each of the digitally encoded samples of transmitted and received signals from a telephone station to derive an output signal having a first or a second characteristic when the transmitted signal sample is respectively not less than or less than the received signal sample; an up/down counter, having a non-overflow store that is incremented or decremented in response to said first or second characteristics, respectively, of the output signal; and a digital attenuator responsive to the output of the up/down counter for attenuating the received signals wherein said output is generated only when the number stored in the counter exceeds a preselected count.
Claim 8
Dependent Claim
126 words
A digital echo attenuation circuit for a telephone system comprising: a comparator for comparing at least some of the most significant bits of each of the digitally encoded samples of transmitted and received signals from a telephone station to derive an output signal having a first or a second characteristic when the transmitted signal sample is respectively not less than or less than the received signal sample; an up/down counter, having a non-overflow store that is incremented or decremented in response to said first or second characteristics, respectively, of the output signal; and a digital attenuator responsive to the output of the up/down counter for attenuating the received signals wherein said output is generated only when the number stored in the counter exceeds a preselected count.
Claim 9
Dependent Claim
117 words
A digital echo attenuation circuit for a telephone system comprising: a comparator for comparing at least some of the most significant bits x and y of each of the digitally encoded samples of transmit signals and receive signals from a telephone station respectively, to derive an output: (|x| - |y|) = 1 if x ≧ y (|x| - |y|) = 0 if x < y an L-bit accumulator having an accumulated store O < A < (2 L - 1), and a present value: ##EQU2## a digital attenuator responsive to the output of the accumulator for attenuating the receive signals wherein said output is generated when the store in the accumulator is at least 2.sup.(L - 1).
Claim 10
Dependent Claim
117 words
A digital echo attenuation circuit for a telephone system comprising: a comparator for comparing at least some of the most significant bits x and y of each of the digitally encoded samples of transmit signals and receive signals from a telephone station respectively, to derive an output: (|x| - |y|) = 1 if x ≧ y (|x| - |y|) = 0 if x < y an L-bit accumulator having an accumulated store O < A < (2 L - 1), and a present value: ##EQU2## a digital attenuator responsive to the output of the accumulator for attenuating the receive signals wherein said output is generated when the store in the accumulator is at least 2.sup.(L - 1).
Claim 11
Dependent Claim
126 words
A digital echo attenuation circuit for a telephone system comprising: a comparator for comparing at least some of the most significant bits of each of the digitally encoded samples of transmitted and received signals from a telephone station to derive an output signal having a first or a second characteristic when the received signal sample is respectively not less than or less than the transmitted signal sample; an up/down counter, having a non-overflow store that is incremented or decremented in response to said first or second characteristics, respectively, of the output signal; and a digital attenuator responsive to the output of the up/down counter for attenuating the transmitted signals wherein said output is generated only when the number stored in the counter exceeds a preselected count.
Claim 12
Dependent Claim
126 words
A digital echo attenuation circuit for a telephone system comprising: a comparator for comparing at least some of the most significant bits of each of the digitally encoded samples of transmitted and received signals from a telephone station to derive an output signal having a first or a second characteristic when the received signal sample is respectively not less than or less than the transmitted signal sample; an up/down counter, having a non-overflow store that is incremented or decremented in response to said first or second characteristics, respectively, of the output signal; and a digital attenuator responsive to the output of the up/down counter for attenuating the transmitted signals wherein said output is generated only when the number stored in the counter exceeds a preselected count.
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) | 1981-10-30 | 1982-05-01 | 1982-10-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-10-30 | 1986-05-01 | 1986-10-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-10-30 | 1990-05-01 | 1990-10-31 | $7700.00 | Window Closed / Lapsed |