US3896273A
Expired / Lapsed
US
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Digital echo suppressor
Assignee: International Telecommunications Satellite Organization
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Filing: 1971-01-08
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Granted: 1975-07-22
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Expires: 1991-01-08
Abstract
Abstract A digital echo suppressor comprising a digital voice level detector which detects the instantaneous signal amplitude of voice being received over one line of a 4-wire transmission path. To suppress the echo of this signal the digital voice level detector activates for a predetermined period of time a gate generator which controls an associated threshold generator. The threshold generator adjusts the threshold in a digital level comparator to a level equal to n dB below the level of the received signal amplitude. The echo of the received signal, which is attenuated an amount equal to (n + 1) dB by a hybrid, is compared in the digital level comparator with the threshold level. Since the attenuated received signal amplitude level does not exceed the threshold level, the return path of the 4-wire transmission path is disabled by maintaining open an echo suppression switch. Break-in means are provided to enable a softer talker to break-in to a louder talker and to maintain the circuit after break-in even if the softer talker''s speech power decreases.
Inventors
- 👤 Ettore Fariello
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 15:38
CPC Classifications
G; G06; G06F; G06F7/00; G06F7/02; G06F7/026; H; H04; H04B; H04B3/00; H04B3/02; H04B3/20
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
137 words
In a comMunications system having a four-wire transmission circuit connected to a two-wire circuit via a terminal, apparatus for suppressing echo comprising: a. means for detecting the amplitude level of a signal being received on the receive line of said four-wire circuit; b. means, connected to said detection means, for generating a threshold level which is a predetermined value less than said detected amplitude level; c. means, connected to said generating means, for storing, for a predetermined period of time, said threshold level and comparing the amplitude of a signal on the transmit line of said four-wire circuit to said stored threshold level, and d. means, connected to said means for comparing, for maintaining the transmit line of said four-wire circuit disabled if the signal amplitude on the transmit line is less than said stored threshold level.
Claim 2
Dependent Claim
137 words
In a comMunications system having a four-wire transmission circuit connected to a two-wire circuit via a terminal, apparatus for suppressing echo comprising: a. means for detecting the amplitude level of a signal being received on the receive line of said four-wire circuit; b. means, connected to said detection means, for generating a threshold level which is a predetermined value less than said detected amplitude level; c. means, connected to said generating means, for storing, for a predetermined period of time, said threshold level and comparing the amplitude of a signal on the transmit line of said four-wire circuit to said stored threshold level, and d. means, connected to said means for comparing, for maintaining the transmit line of said four-wire circuit disabled if the signal amplitude on the transmit line is less than said stored threshold level.
Claim 3
Dependent Claim
30 words
The apparatus of claim 1 wherein said predetermined value is dependent upon the difference in amplitude between the receive line signal and the corresponding echo signal on the transmit line.
Claim 4
Dependent Claim
52 words
The apparatus of claim 2 wherein said threshold level is stored for a period of time which is equal to the total delay between the time said receive line signal and its corresponding echo signal are, respectively, first detected by said means for detecting and then compared in said means for comparing.
Claim 5
Dependent Claim
141 words
In a telephone communications system having a separate transmit and receive circuit, apparatus for suppressing echo comprising: a. means for detecting the amplitude levels of a signal being received on said received line, b. means, connected to said detecting means, for generating for a predetermined period of time for each detected amplitude level a corresponding threshold level which is at a predetermined level less than the detected amplitude level and for activating only one of said thresholds as an output; c. means, connected to said generating and activating means, for storing said activated threshold level and for comparing the amplitude of a signal on said transmit line to said stored threshold; and d. means, connected to said storing and comparing means, for maintaining said transmit line disabled if the signal amplitude on said transmit line is less than said stored threshold.
Claim 6
Dependent Claim
141 words
In a telephone communications system having a separate transmit and receive circuit, apparatus for suppressing echo comprising: a. means for detecting the amplitude levels of a signal being received on said received line, b. means, connected to said detecting means, for generating for a predetermined period of time for each detected amplitude level a corresponding threshold level which is at a predetermined level less than the detected amplitude level and for activating only one of said thresholds as an output; c. means, connected to said generating and activating means, for storing said activated threshold level and for comparing the amplitude of a signal on said transmit line to said stored threshold; and d. means, connected to said storing and comparing means, for maintaining said transmit line disabled if the signal amplitude on said transmit line is less than said stored threshold.
Claim 7
Dependent Claim
22 words
The apparatus of claim 4 wherein said stored threshold represents the highest signal amplitude level detected during said predetermined period of time.
Claim 8
Dependent Claim
74 words
The apparatus of claim 4 wherein, when said received signal amplitude is decreasing, said stored threshold level is adjusted at the end of said predetermined period of time to a threshold level corresponding to the next lower signal amplitude level detected during said predetermined period of time wherein said latter threshold is stored for a period of time up to said predetermined period of time commencing from the detection of said next lower signal.
Claim 9
Dependent Claim
44 words
The apparatus of claim 5 wherein, when said receive signal level increases, said stored threshold level is adjusted immediately upon detection of the higher amplitude level to a corresponding higher threshold level for a period of time up to said predetermined period of time.
Claim 10
Dependent Claim
30 words
The apparatus of claim 7 wherein said threshold level is dependent upon the difference in amplitude between the receive line signal and the corresponding echo signal on the transmit line.
Claim 11
Dependent Claim
42 words
The apparatus of claim 8 wherein said predetermined period of time is equal to the delay time between the time the receive line signal is detected by said means for detecting and the corresponding echo signal in the transmit line is compared.
Claim 12
Dependent Claim
23 words
The apparatus of claim 9 wherein said transmit line is enabled when the signal amplitude on said transmit line exceeds the stored threshold.
Claim 13
Dependent Claim
28 words
The apparatus of claim 10 further including means, anteriorly connected to said means for detecting, for attenuating the receive line signal amplitude when said stored threshold is exceeded.
Claim 14
Dependent Claim
99 words
The apparatus of claim 7 wherein sAid means for generating and activating comprises: a. a plurality of gating means, connected to said means for detecting, for emitting enabling pulses for said predetermined period of time wherein each gating means emits an enabling pulse when the receive line signal amplitude exceeds a level associated with that gating means; b. a plurality of threshold generators, each connected to a respective gating means; and c. means for enabling only the threshold generator corresponding to the highest detected receive line signal amplitude to change the threshold level stored in said means for storing.
Claim 15
Dependent Claim
59 words
The apparatus of claim 12 wherein said means for storing and comparing means for digitally comparing, in serial mode commencing with the most significant bit, a digital code word representing the signal on said transmit line and a stored digital code word representing the signal on said transmit line and a stored digital code word representing the threshold level.
Claim 16
Dependent Claim
36 words
The apparatus of claim 13 wherein said means for maintaining includes means for maintaining said transmit line enabled for a period of time following the end of an enabling pulse from said comparing and storing means.
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) | 1978-07-21 | 1979-01-20 | 1979-07-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-07-21 | 1983-01-20 | 1983-07-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-07-21 | 1987-01-20 | 1987-07-22 | $7700.00 | Window Closed / Lapsed |