US3602648A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Subscriber telephone circuit
Assignee: AT&T Inc
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Filing: 1969-12-08
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Granted: 1971-08-31
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Expires: 1989-12-08
Abstract
Abstract In a telephone set speech circuit employing a nonreactive hybrid network the transmitter branch and the receiver branch each includes a respective loop equalizer in the form of an operational amplifier with a feedback control path which includes a path to ground by way of a capacitive element. In the receiver branch a switch responsive to a preselected signal level in the transmitter branch disconnects the feedback path of the operational amplifier from the capacitive element which provides protection against singing and which helps to ensure a relatively flat frequency response for sidetone irrespective of loop length.
Inventors
- 👤 Roger E Holtz
- 👤 John A Markevich
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 15:28
CPC Classifications
H; H04; H04M; H04M1/00; H04M1/58; H04M1/585; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/126; H04L; H04L25/00; H04L25/02; H04L25/03; H04L25/03878; H04M9/00; H04M9/08
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
94 words
A speech network for a telephone set comprising, in combination, a substantially nonreactive hybrid network, a receiver, first means connecting said receiver to said hybrid network, a transmitter, second means connecting said transmitter to said hybrid network, each of said first and second means including a respective equalizer circuit comprising an operational amplifier circuit, means for frequency equalization connected between the feedback path of said operational amplifier and a source of reference potential, and means responsive to a preselected output level from said transmitter for disconnecting said frequency equalization means from said first means.
Claim 2
Dependent Claim
94 words
A speech network for a telephone set comprising, in combination, a substantially nonreactive hybrid network, a receiver, first means connecting said receiver to said hybrid network, a transmitter, second means connecting said transmitter to said hybrid network, each of said first and second means including a respective equalizer circuit comprising an operational amplifier circuit, means for frequency equalization connected between the feedback path of said operational amplifier and a source of reference potential, and means responsive to a preselected output level from said transmitter for disconnecting said frequency equalization means from said first means.
Claim 3
Dependent Claim
20 words
Apparatus in accordance with claim 1 wherein each of said first and second means further includes a respective AGC circuit.
Claim 4
Dependent Claim
14 words
Apparatus in accordance with claim 1 wherein said frequency equalization means comprises a capacitor.
Claim 5
Dependent Claim
13 words
Apparatus in accordance with claim 3 wherein said disconnecting means comprises a switch.
Claim 6
Dependent Claim
133 words
A speech network for a telephone circuit comprising, in combination, a substantially nonreactive hybrid network, a receiver, first means connecting said receiver to said hybrid network, a transmitter, second means connecting said transmitter to said hybrid network, each of said first and second means including a respective equalizer circuit comprising amplitude equalization means and frequency equalization means, power supply means for deriving DC power from a telephone line, a control path connecting each of said first and second means to said power supply thereby to effect amplitude equalization, and means responsive to an output from said transmitter exceeding a preselected level for disconnecting said frequency equalization means from said equalizer of said first means thereby to inhibit singing and to ensure a substantially flat frequency characteristic in the sidetone transmission of said set.
Claim 7
Dependent Claim
133 words
A speech network for a telephone circuit comprising, in combination, a substantially nonreactive hybrid network, a receiver, first means connecting said receiver to said hybrid network, a transmitter, second means connecting said transmitter to said hybrid network, each of said first and second means including a respective equalizer circuit comprising amplitude equalization means and frequency equalization means, power supply means for deriving DC power from a telephone line, a control path connecting each of said first and second means to said power supply thereby to effect amplitude equalization, and means responsive to an output from said transmitter exceeding a preselected level for disconnecting said frequency equalization means from said equalizer of said first means thereby to inhibit singing and to ensure a substantially flat frequency characteristic in the sidetone transmission of said set.
Claim 8
Dependent Claim
55 words
Apparatus in accordance with claim 5 wherein said amplitude eqUalization means comprises an operational amplifier with a feedback path, said frequency equalization means comprising a reactive element connected between said feedback path and a source of reference potential, and said disconnecting means comprising a switch arranged to isolate said reactive element from said feedback path.
Claim 9
Dependent Claim
19 words
Apparatus in accordance with claim 5 wherein said first and second means each further includes a respective AGC circuit.
Claim 10
Dependent Claim
57 words
Apparatus in accordance with claim 5 wherein said second means includes a preamplifier, a dial circuit, a control path connecting said dial circuit to said preamplifier whereby said preamplifier may be disabled during dialing, a control path connecting each of said equalizer circuits to said power supply means thereby to effect equalization in terms of loop length.
Claim 11
Dependent Claim
41 words
Apparatus in accordance with claim 5 further including third means for connecting said hybrid circuit to a telephone line, ringing means, means connecting said ringing means to said third means, and means connecting said power supply means to said third means.
Claim 12
Dependent Claim
107 words
A telephone speech network comprising, in combination, a nonreactive hybrid circuit, a transmitter branch connected to said hybrid circuit, and a receiver branch connected to said hybrid circuit, each of said branches including a respective equalizer circuit, said equalizer circuit comprising an operational amplifier including a feedback path, said operational amplifier in said receiver branch including dual function means responsive to a signal in said transmitter branch above a preselected level for inhibiting a singing action in said circuit and for maintaining the sidetone in said circuit substantially flat from the standpoint of frequency irrespective of the length of the loop to which said network is connected.
Claim 13
Dependent Claim
107 words
A telephone speech network comprising, in combination, a nonreactive hybrid circuit, a transmitter branch connected to said hybrid circuit, and a receiver branch connected to said hybrid circuit, each of said branches including a respective equalizer circuit, said equalizer circuit comprising an operational amplifier including a feedback path, said operational amplifier in said receiver branch including dual function means responsive to a signal in said transmitter branch above a preselected level for inhibiting a singing action in said circuit and for maintaining the sidetone in said circuit substantially flat from the standpoint of frequency irrespective of the length of the loop to which said network is connected.
Claim 14
Dependent Claim
38 words
Apparatus in accordance with claim 10 wherein said operational amplifier includes a capacitive element connected between said feedback path and a reference potential, said dual function means comprising a switch for disconnecting said capacitor from said feedback path.
Claim 15
Dependent Claim
31 words
Apparatus in accordance with claim 11 wherein said transmitter branch includes an AGC circuit and means for directing a control signal from said AGC circuit for the operation of said switch.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-08-30 | 1975-03-01 | 1975-08-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-08-30 | 1979-03-01 | 1979-08-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-08-30 | 1983-03-01 | 1983-08-31 | $7700.00 | Window Closed / Lapsed |