US3647993A
Expired / Lapsed
US
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Tone disabler
Assignee: Wescom Inc
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Filing: 1970-05-18
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Granted: 1972-03-07
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Expires: 1990-05-18
Abstract
Abstract For use in a long-distance telephone link alternately employed for voice communications and data transmission, a tone disabler for inhibiting an associated echo suppressor in response to a tone signal, such as is transmitted under existing practices prior to the transmission of data to insure that all echo suppressor controlled attenuation is removed from the telephone link during data transmission. Series and parallel resonant filters tuned to the tone frequency and a comparator circuit are used to compare the level of the tone frequency energy in the tone disabler''s input signals against the level of all other voice frequency or so-called guard band energy, so that a tone signal confirming timing sequence is initiated only when the tone signal energy predominates. Once a tone signal is confirmed, the inputs to the comparator circuit are switched from the filters to a broad band load impedance, so that the tone disabler is transferred from a tone detecting to a holding mode in which the comparator circuit and a simple RC delay circuit maintain the associated echo suppressor in an inhibited condition throughout the data transmission and for a predetermined time after the tone disabler''s input signal level drops below a predetermined threshold characteristic of the completion of the data transmission. Solid state switching devices are used for inhibiting and releasing the associated echo suppressor and for transferring the tone disabler between its tone detecting and holding modes to eliminate switching transients and other potential sources of noise such as might interfere with or degrade the performance of the tone disabler, associated echo suppressor, or other equipment located nearby.
Inventors
- 👤 John D Foulkes
- 👤 Warren G Bender
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:27
CPC Classifications
H; H04; H04M; H04M11/00; H04M11/06; H04B; H04B3/00; H04B3/02; H04B3/20
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
236 words
In a tone disabler for use with an echo suppressor in a telephone system of the type including separate transmit and receive channels with attenuation inserted and removed therefrom by said echo suppressor in dependence on the signal conditions existing in said channels; the combination comprising summing means coupled to said transmit and receive channels for providing a sum signal representative of the signals in said transmit and receive channels; a first frequency rejection filter connected to said summing means for responding to all energy in said sum signal except for any energy substantially at a predetermined tone frequency to provide a guard band signal level; a second frequency selection filter connected to said summing means for responding to any energy substantially at said tone frequency and rejecting substantially all energy at any other frequency to provide a tone frequency signal level; and means for comparing the levels of said guard band and tone frequency signals including first and second amplifying means each having an inverting input and an output, said first amplifying means having its inverting input coupled across said second filter for providing an output signal representative of the level of said tone frequency signal, and said seCond amplifying means having its inverting input coupled across both said first and second filters and to the output of said second amplifying means to provide an output signal representative of the level of guard band signal.
Claim 2
Dependent Claim
236 words
In a tone disabler for use with an echo suppressor in a telephone system of the type including separate transmit and receive channels with attenuation inserted and removed therefrom by said echo suppressor in dependence on the signal conditions existing in said channels; the combination comprising summing means coupled to said transmit and receive channels for providing a sum signal representative of the signals in said transmit and receive channels; a first frequency rejection filter connected to said summing means for responding to all energy in said sum signal except for any energy substantially at a predetermined tone frequency to provide a guard band signal level; a second frequency selection filter connected to said summing means for responding to any energy substantially at said tone frequency and rejecting substantially all energy at any other frequency to provide a tone frequency signal level; and means for comparing the levels of said guard band and tone frequency signals including first and second amplifying means each having an inverting input and an output, said first amplifying means having its inverting input coupled across said second filter for providing an output signal representative of the level of said tone frequency signal, and said seCond amplifying means having its inverting input coupled across both said first and second filters and to the output of said second amplifying means to provide an output signal representative of the level of guard band signal.
Claim 3
Dependent Claim
46 words
The combination of claim 1 wherein said first filter comprises a series resonant circuit tuned to said tone frequency and coupled across said summing means, and said second filter comprises a parallel resonant circuit tuned to said tone frequency and also coupled across said summing means.
Claim 4
Dependent Claim
25 words
The combination of claim 2 wherein said series resonant and parallel resonant circuits are connected in series in the order named across said summing means.
Claim 5
Dependent Claim
53 words
The combination of claim 1 wherein said summing means is coupled to said transmit and receive channel by substantially linear circuit means, and further including a compressor means coupled between said summing means and said first and second filters for applying a substantially constant level sum signal to said first and second filters.
Claim 6
Dependent Claim
43 words
The combination of claim 4 wherein said first and second filters are series resonant and parallel resonant circuits, respectively, which are tuned to said tone frequency and connected in series in the order named across the inverting input of said second amplifying means.
Claim 7
Dependent Claim
138 words
The combination of claim 1 wherein said comparator means further includes biasing means coupled to said first and second amplifying means for biasing the outputs of one and the other of said amplifying means positively and negatively, respectively, by identical amounts relative to a predetermined reference potential, first and second oppositely poled diodes respectively connected to the outputs of said one and said other amplifying means, and a capacitor connected between a point at said reference potential and a junction between said diodes; said diodes being poled so that said capacitor is charged in one sense relative to said reference potential when the level of the tone frequency signal exceeds the level of the guard band signal and in the opposite sense when the level of the guard band signal exceeds the level of the tone frequency signal.
Claim 8
Dependent Claim
137 words
The combination of claim 6 wherein said tone disabler further includes switching means for inhibiting said echo suppressor to prevent said echo suppressor from inserting attenuation into said transmit and receive channel, said combination further including integrating means coupled to said capacitor for providing an output signal representative of the average level of the charge on said capacitor, threshold detecting means coupled to said integrating means for providing an output signal when the said capacitor has charged in said one sense to an average level in excess of a predetermined threshold level, and a first timing means coupled between said threshold detecting means and said switch means for delaying the actuation of said switch means until after the average charge on said capacitor has remained above said threshold level without any substantial interruption for a predetermined period.
Claim 9
Dependent Claim
43 words
The combination of claim 7 wherein said first and second filters are series resonant and parallel resonant circuits, respectively, which are tuned to said tone frequency and connected in series in the order named across the inverting input of said second amplifying means.
Claim 10
Dependent Claim
314 words
For use with an echo suppressor of the type employed in a telephone system including separate transmit and receive channels for controllably inserting and removing attenuation into and from said channels in dependence on the signal levels existing in said channels, a tone disabler for applying an inhibiting signal to said echo suppressor in response to a tone signal of predetermined frequency which persists without substantial interruption for at least a predetermined minimum time period, said inhibiting signal preventing said echo suppressor from inserting any attenuation into said channels regardless of the signal levels existing therein; said tone disabler comprIsing the combination of summing means coupled to said transmit and receive channels via substantially linear circuitry to provide a sum signal representative of the signals existing in said transmit and receive channels, frequency separating means coupled to said summing means for separating said sum signal into a first signal with a level representative of the tone frequency energy in said transmit and receive channels and a second signal with a level representative of the energy of substantially all signals in said transmit and receive channels other than said tone frequency energy, a comparator means coupled to said frequency separating means for comparing the level of said first signal to the level of said second signal, a threshold detector means coupled to said comparator means for providing an output signal when the level of said first signal exceeds the level of said second signal by a predetermined threshold amount, a timing means coupled to said threshold detecting means for providing an output signal only if the level of said first signal exceeds the level of said second signal without any substantial interruption for at least a predetermined minimum time period, and solid-state switching means coupled to said timing means and actuated by an output signal therefrom for applying an inhibiting signal to said echo suppressor.
Claim 11
Dependent Claim
314 words
For use with an echo suppressor of the type employed in a telephone system including separate transmit and receive channels for controllably inserting and removing attenuation into and from said channels in dependence on the signal levels existing in said channels, a tone disabler for applying an inhibiting signal to said echo suppressor in response to a tone signal of predetermined frequency which persists without substantial interruption for at least a predetermined minimum time period, said inhibiting signal preventing said echo suppressor from inserting any attenuation into said channels regardless of the signal levels existing therein; said tone disabler comprIsing the combination of summing means coupled to said transmit and receive channels via substantially linear circuitry to provide a sum signal representative of the signals existing in said transmit and receive channels, frequency separating means coupled to said summing means for separating said sum signal into a first signal with a level representative of the tone frequency energy in said transmit and receive channels and a second signal with a level representative of the energy of substantially all signals in said transmit and receive channels other than said tone frequency energy, a comparator means coupled to said frequency separating means for comparing the level of said first signal to the level of said second signal, a threshold detector means coupled to said comparator means for providing an output signal when the level of said first signal exceeds the level of said second signal by a predetermined threshold amount, a timing means coupled to said threshold detecting means for providing an output signal only if the level of said first signal exceeds the level of said second signal without any substantial interruption for at least a predetermined minimum time period, and solid-state switching means coupled to said timing means and actuated by an output signal therefrom for applying an inhibiting signal to said echo suppressor.
Claim 12
Dependent Claim
135 words
The tone disabler of claim 9 wherein said comparator means includes a first operational amplifier with an inverting input coupled to said frequency-separating means to receive only said first signal therefrom, a second operational amplifier with an inverting input coupled to said frequency separating means to receive said first and second signals therefrom, respective outputs for said first and second amplifiers, and cross coupling means between the output of said first amplifier and the inverting input of said second amplifier; said first and second amplifiers having substantially identical gains to signals received from said frequency separation means, and said second operational amplifier having substantially unity gain to signals received through said cross coupling means; whereby said first and second operational amplifiers supply output signals respectively representative of the levels of said first and second signals.
Claim 13
Dependent Claim
143 words
The tone disabler of claim 10 further including a broad band load impedance connected in shunt with said summing means, means coupling the inverting inputs of said first and second amplifiers across a predetermined portion of said load impedance, a normally conductive transistor having its collector-emitter circuit connected across said predetermined portion of said load impedance and a base coupled to said switching means, and a normally nonconductive transistor having its collector-emitter circuit connected across said frequency-separating means and a base coupled to said switching means; said switching means providing signals in response to an output signal from said timing means for switching said first and second transistors to nonconductive and conductive states respectively to thereby transfer said tone disabler to a holding mode to maintain said echo suppressor in an inhibited state until said sum signal drops below a predetermined threshold level.
Claim 14
Dependent Claim
43 words
The tone disabler of claim 11 further including a delay means coupled to said switching means for delaying the deactuation of said switching means until after the level of said sum signal has remained below said threshold level for a predetermined time period.
References Cited (Backward Citations)
US3069501A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-03-07 | 1975-09-06 | 1976-03-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-03-07 | 1979-09-06 | 1980-03-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-03-07 | 1983-09-06 | 1984-03-07 | $7700.00 | Window Closed / Lapsed |