US3592971A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Equalizing and antisidetone telephone circuit
Assignee: Nortel Networks Ltd
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Filing: 1969-12-01
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Granted: 1971-07-13
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Expires: 1989-12-01
Abstract
Abstract A telephone circuit which equalizes transmit and receive signals to compensate for frequency dependent signal losses in a telephone line. Equalizing amplifiers are used which have a sloped frequency response and a variable gain characteristic that is responsive to the telephone line operating voltage which is itself responsive to the length of the telephone line. A balanced amplifier is also used to drive a telephone receiver with a balanced transmit signal and an unbalanced receive signal, the balanced transmit signal effectively cancelling out across the telephone receiver to provide antisidetone.
Inventors
- 👤 Michael C J Cowpland
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:52
CPC Classifications
H; H04; H04M; H04M1/00; H04M1/738; H04M1/76; H04B; H04B3/00; H04B3/02; H04B3/04; H04B3/14; H04B3/143; H04B3/145; H04M1/58; H04M1/585; H04M9/00; H04M9/08
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
192 words
A telephone circuit comprisiNg: transmitter terminals for connection to a source of transmit signals; line terminals for connection to a telephone line which is connected to sources of operating voltage and receive signals; a first amplifier means having an input connected to the transmitter terminals, a final output connected to the line terminals, and an intermediate output; a balanced amplifier means having first and second inputs connected in parallel across the intermediate output, first and second outputs connected in parallel, a receiver output having connections for connection to a telephone receiver, and first and second push-pull inputs; a second amplifier means having an input connected to the parallel connected first and second outputs, and an output connected to the said first push-pull input; and, a third amplifier means having an input connected to the line terminals, and an output connected to said second pushpull input, whereby a transmit signal at the transmitter terminals will be connected to the line terminals, the receiver output having a balanced transmit signal thereacross, and whereby a receive signal at the line terminals will be connected to the receiver output, appearing thereacross as an unbalanced receive signal.
Claim 2
Dependent Claim
192 words
A telephone circuit comprisiNg: transmitter terminals for connection to a source of transmit signals; line terminals for connection to a telephone line which is connected to sources of operating voltage and receive signals; a first amplifier means having an input connected to the transmitter terminals, a final output connected to the line terminals, and an intermediate output; a balanced amplifier means having first and second inputs connected in parallel across the intermediate output, first and second outputs connected in parallel, a receiver output having connections for connection to a telephone receiver, and first and second push-pull inputs; a second amplifier means having an input connected to the parallel connected first and second outputs, and an output connected to the said first push-pull input; and, a third amplifier means having an input connected to the line terminals, and an output connected to said second pushpull input, whereby a transmit signal at the transmitter terminals will be connected to the line terminals, the receiver output having a balanced transmit signal thereacross, and whereby a receive signal at the line terminals will be connected to the receiver output, appearing thereacross as an unbalanced receive signal.
Claim 3
Dependent Claim
108 words
A telephone circuit as defined in claim 1 further comprising; a voltage detector means connected across the line terminals for detecting the operating voltage, and obtaining therefrom a direct-current control voltage output; and wherein the first, second and third amplifier means each have a control input connected to the voltage detector means output; and wherein the first, second and third amplifier means have a variable gain and a predetermined frequency response, which variable gain is responsive to the magnitude of the said control voltage, whereby the transmit signal connected to the line terminals will be equalized, and the unbalanced receive signal across the receiver output will be equalized.
Claim 4
Dependent Claim
102 words
A telephone circuit as defined in claim 2 wherein: the balanced amplifier means consists of a pair of amplifiers with each amplifier comprising a first and a second transistor each having an emitter, a base and a collector, where, in the first transistors the emitters are connected to a ground connection, the bases from the first and second parallel inputs, and the collectors form the receiver output, and where, in the second transistors the emitters are connected to corresponding collectors of the first transistors, the bases form the first and second push-pull inputs and the collectors form the first and second outputs.
Claim 5
Dependent Claim
99 words
A telephone circuit as defined in claim 3 wherein: the second and third amplifier means each comprise a pair of amplifiers, the one having a substantially fixed gain and a uniform frequency response, and the other including the control input and having a variable gain responsive to the said control voltage and also having a sloped frequency response which rises with frequency, the inputs of each said pair of amplifiers being connected in parallel to form the said input thereof, and the outputs of each said pair of amplifiers being connected in parallel to form the said output thereof.
Claim 6
Dependent Claim
138 words
A telephone circuit as defined in claim 3 wherein: the second and third amplifier means each comprise a pair of amplifiers having a uniform frequency response, the one having a substantially fixed gain, and the other including the control input and having a variable gain responsive to the said control voltage; and the said circuit further comprising a pair of signal coupling networks each having a sloped frequency response which rises with frequency, each one of the said pair of networks being connected between the inputs of a respective pair of amplifiers, the input of the amplifier having a substantially fixed gain comprising the respective input of the second and third amplifier means, and the outputs of each said pair of amplifiers being connected in parallel and comprising the respecTive output of the second and third amplifier means.
References Cited (Backward Citations)
US3330912A
Cited
US3461240A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-07-12 | 1975-01-11 | 1975-07-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-07-12 | 1979-01-11 | 1979-07-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-07-12 | 1983-01-11 | 1983-07-13 | $7700.00 | Window Closed / Lapsed |