US3784755A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Long-line telephone circuit
Assignee: Nortel Networks Technology Corp
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Filing: 1971-09-07
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Granted: 1974-01-08
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Expires: 1991-09-07
Abstract
Abstract A long-line telephone circuit which utilizes a combination of two-wire and four-wire transmission to advantage in order to achieve subscriber loop lengths of up to 36,000 feet from a central office with less overall conductive material (i.e. finer gauge wire) than is currently used and without the necessity of employing loading coils in the lines.
Inventors
- 👤 R Cambridge
- 👤 M Chytil
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 13:21
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/38; H04B1/40; H04B1/54; H04B1/58; H04B3/00; H04B3/02; H04B3/03
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
225 words
A long-line telephone circuit for connection to a central office, comprising: a telephone set including a transmitter and a receiver; a three port network located between the telephone set and the central office, for connecting a variable length transmit path and a variable length receive path to a common path; the common path being a fixed length and connecting the three port network to the central office, the loss of the common path being sufficient to reflect a substantially constant impedance at the three-port network regardless of the terminating impedance at the central office; a transmit amplifier connecting the transmitter to the three port network via the transmit path, the gain of the transmit amplifier being such as to compensate for the transmission loss of the variable length transmit path and the common path; and a receive amplifier connecting the three port network to the receiver via the receive path, the gain of the receive amplifier being such as to compensate for the transmission loss of the variable length receive path and the common path; the gain of the transmit and receive amplifiers, less the loss of the variable length transmit and receive paths and the loss of the three port network between the variable length transmit and receive paths, being such as to maintain the sidetone level between the transmitter and receiver substantially constant.
Claim 2
Dependent Claim
225 words
A long-line telephone circuit for connection to a central office, comprising: a telephone set including a transmitter and a receiver; a three port network located between the telephone set and the central office, for connecting a variable length transmit path and a variable length receive path to a common path; the common path being a fixed length and connecting the three port network to the central office, the loss of the common path being sufficient to reflect a substantially constant impedance at the three-port network regardless of the terminating impedance at the central office; a transmit amplifier connecting the transmitter to the three port network via the transmit path, the gain of the transmit amplifier being such as to compensate for the transmission loss of the variable length transmit path and the common path; and a receive amplifier connecting the three port network to the receiver via the receive path, the gain of the receive amplifier being such as to compensate for the transmission loss of the variable length receive path and the common path; the gain of the transmit and receive amplifiers, less the loss of the variable length transmit and receive paths and the loss of the three port network between the variable length transmit and receive paths, being such as to maintain the sidetone level between the transmitter and receiver substantially constant.
Claim 3
Dependent Claim
223 words
A long-line telephone circuit for connection to a central office, comprising: a telephone set including a transmitter and receiver; a hybrid, having a two-wire termination and a four-wire termination, located between the telephone set and the central office, a fixed distance from said office; a first telephone line connected between the two-wire termination and the central office, and having sufficient loss to reflect a substantially constant impedance at the hybrid regardless of the terminating impedance at the central office; a second telephone line of variable length connected between an input of the four-wire termination and the telephone set; a third telephone line of variable length connected between an output of the four-wire termination and the telephone set; a transmit amplifier connected between the transmitter and the second telephone line and having sufficient gain to compensate for the loss of the first and second telephone lines; and a receive amplifier connected between the third telephone line and the receiver and having sufficient gain to compensate for the loss of the first and third telephone lines; the gain of the transmit and receive amplifiers less the loss of the second and third telephone lines and the loss through the hybrid between said input and said output of the four-wire termination, being such as to maintain the sidetone level between the transmitter and receiver substantially constant.
Claim 4
Dependent Claim
223 words
A long-line telephone circuit for connection to a central office, comprising: a telephone set including a transmitter and receiver; a hybrid, having a two-wire termination and a four-wire termination, located between the telephone set and the central office, a fixed distance from said office; a first telephone line connected between the two-wire termination and the central office, and having sufficient loss to reflect a substantially constant impedance at the hybrid regardless of the terminating impedance at the central office; a second telephone line of variable length connected between an input of the four-wire termination and the telephone set; a third telephone line of variable length connected between an output of the four-wire termination and the telephone set; a transmit amplifier connected between the transmitter and the second telephone line and having sufficient gain to compensate for the loss of the first and second telephone lines; and a receive amplifier connected between the third telephone line and the receiver and having sufficient gain to compensate for the loss of the first and third telephone lines; the gain of the transmit and receive amplifiers less the loss of the second and third telephone lines and the loss through the hybrid between said input and said output of the four-wire termination, being such as to maintain the sidetone level between the transmitter and receiver substantially constant.
Claim 5
Dependent Claim
36 words
A long-line telephone circuit as described in claim 2 in which an operating current connected from the central office over the first telephone line is phantomed over the second and third telephone lines through the hybrid.
Claim 6
Dependent Claim
23 words
A long-line telephone circuit as defined in claim 3 in which the length of the first telephone line is at least 6,000 feet.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-01-07 | 1977-07-09 | 1978-01-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-07 | 1981-07-09 | 1982-01-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-07 | 1985-07-09 | 1986-01-08 | $7700.00 | Window Closed / Lapsed |