US3860768A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Echo compensation circuit to erase echoes in telephone circuits
Assignee: Individual
•
Filing: 1973-03-05
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Granted: 1975-01-14
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Expires: 1993-03-05
Abstract
Abstract An echo compensation circuit for telephone connections by way of two-wire-four-wire circuits, where the echo is eliminated by superposing at 180* out of phase signal derived with the aid of a transversal filter from the speech signal which generates the echo, the transversal filter being preceded by a number k of simple delay members with delay times Tau for compensation of the basic transmission k X Tau of the echo path, the transversal filter being reduced by the same number k of coefficient members which partially degrade the transmission function of the circuit.
Inventors
- 👤 Rolf Wehrmann
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 21:19
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20; H04B3/23
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
342 words
In an echo compensation circuit for telephone connections over two wire-four wire cicuits of the type wherein the echo is eliminated by superposing a signal of opposing phase which is derived from the speech signal creating the echo by means of a transverse filter, wherein the transverse filter comprises a number of delay circuits having a delay time Tau and a number of adjustable coefficient members for the tapped voltages of the transverse filter, adjustment being effected by cross-correlation analysis between the tapped voltages of the transverse filter and the remaining echo at the transmission direction output, and wherein a delay line which compensates at least a part of the basic transit time of the echo path can be connected in front of the transverse filter, the improvement therein comprising the provision of said delay line as a number of delay members which in each case have the same delay time Tau as the delay members of the transverse filter, a pulse generator providing a test pulse to the echo path between the output in the receiving direction and the input in the transmitting direction and providing cyclically recurring pulses at intervals Tau , timing means connected to the input in the transmitting direction for measuring the time for pulse reply to exceed a predetermined threshold in response to the cyclically recurring pulses, and means connected between said time measuring means and said number of delay line members for connecting a number k of said delay members in front of said transverse filter to simulate the measured transit time, including a first plurality of switches operable in accordance with the echo path transit time by connecting said delay members in circuit ahead of said transverse filter, and a control unit including a second plurality of switchs cooperable with said first plurality of switches to effect said delay member connections, said pulse generator and said timing means and said first plurality of switches and said control unit and its second plurality of switches jointly connectible for serving a number of echo compensation circuits.
Claim 2
Dependent Claim
342 words
In an echo compensation circuit for telephone connections over two wire-four wire cicuits of the type wherein the echo is eliminated by superposing a signal of opposing phase which is derived from the speech signal creating the echo by means of a transverse filter, wherein the transverse filter comprises a number of delay circuits having a delay time Tau and a number of adjustable coefficient members for the tapped voltages of the transverse filter, adjustment being effected by cross-correlation analysis between the tapped voltages of the transverse filter and the remaining echo at the transmission direction output, and wherein a delay line which compensates at least a part of the basic transit time of the echo path can be connected in front of the transverse filter, the improvement therein comprising the provision of said delay line as a number of delay members which in each case have the same delay time Tau as the delay members of the transverse filter, a pulse generator providing a test pulse to the echo path between the output in the receiving direction and the input in the transmitting direction and providing cyclically recurring pulses at intervals Tau , timing means connected to the input in the transmitting direction for measuring the time for pulse reply to exceed a predetermined threshold in response to the cyclically recurring pulses, and means connected between said time measuring means and said number of delay line members for connecting a number k of said delay members in front of said transverse filter to simulate the measured transit time, including a first plurality of switches operable in accordance with the echo path transit time by connecting said delay members in circuit ahead of said transverse filter, and a control unit including a second plurality of switchs cooperable with said first plurality of switches to effect said delay member connections, said pulse generator and said timing means and said first plurality of switches and said control unit and its second plurality of switches jointly connectible for serving a number of echo compensation circuits.
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) | 1978-01-13 | 1978-07-15 | 1979-01-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-01-13 | 1982-07-15 | 1983-01-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-01-13 | 1986-07-15 | 1987-01-14 | $7700.00 | Window Closed / Lapsed |