Patent US4373121A successfully refreshed from Google Patents.
US4373121A
Expired / Lapsed
US
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Maintenance termination device
Assignee: AT&T Inc
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Filing: 1981-06-15
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Granted: 1983-02-08
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Expires: 2001-06-15
Abstract
Abstract Substantially identical, unique valued impedance termination networks (26,28) each comprising a resistor (32,38) and a capacitor (34,36) are connected between each telephone subscriber loop conductor (11,13) and ground at the entrance of the loop to the customer's premises (14). The impedance termination networks are balanced to ground for preventing noise from being induced in the loop. In response to an alternating current signal transmitted simultaneously on each conductor from a loop testing apparatus (10), if an impedance termination network is connected between a conductor and ground, the unique impedance value will be measured. The value of the measured impedance is compared with the unique impedance to determine whether there is an open conductor in the loop. Furthermore, a four-layer diode switch (30,40) is connected permanently in series with each loop conductor. In response to a signal greater than the diode threshold voltage, the diode switch breaks down and a path is established directly to the terminal equipment (16). In response to a signal below the threshold voltage the diode switch does not conduct and the loop appears open. Both opens and resistive faults in various sections of the loop may thus be detected and located without mechanically opening the loop.
Inventors
- 👤 Eugene F. Sartori
- 👤 Francis J. Uhrhane
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 12:33
CPC Classifications
H; H04; H04M; H04M3/00; H04M3/22; H04M3/26; H04M3/28; H04M3/30; H04M3/301; H04B; H04B3/00; H04B3/02; H04B3/46
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
126 words
A fault locating circuit (22) in a subscriber loop comprising a plurality of conductors (11,13) connecting a central office (12) with terminal equipment (16) for determining whether said fault is located on the central office side or the terminal equipment side of said locating circuit, said locating circuit comprising a plurality of voltage sensitive devices (30,40), each of said voltage sensitive devices being connected in series with one of said loop conductors between said central office and said terminal equipment, and a termination network comprising a plurality of substantially identical impedance termination networks (26,28), each of said impedance termination networks being connected permanently between different ones of said subscriber loop conductors (11,13) and ground on the central office side of said plurality of voltage sensitive devices.
Claim 2
Dependent Claim
126 words
A fault locating circuit (22) in a subscriber loop comprising a plurality of conductors (11,13) connecting a central office (12) with terminal equipment (16) for determining whether said fault is located on the central office side or the terminal equipment side of said locating circuit, said locating circuit comprising a plurality of voltage sensitive devices (30,40), each of said voltage sensitive devices being connected in series with one of said loop conductors between said central office and said terminal equipment, and a termination network comprising a plurality of substantially identical impedance termination networks (26,28), each of said impedance termination networks being connected permanently between different ones of said subscriber loop conductors (11,13) and ground on the central office side of said plurality of voltage sensitive devices.
Claim 3
Dependent Claim
35 words
The fault locating circuit according to claim 1 wherein said impedance termination networks (26,28) are balanced between said subscriber loop conductors (11,13) and ground, respectively, for preventing noise from being induced in said subscriber loop.
Claim 4
Dependent Claim
47 words
The fault locating circuit according to claim 1 wherein each of said impedance termination networks (26,28) comprises a resistor (32,38) and a capacitor (34,36) connected in series between different ones of said conductors and ground for providing a unique signature in response to an alternating current signal.
Claim 5
Dependent Claim
178 words
In a telephone subscriber loop comprising a plurality of conductors (11,13) connecting a telephone central office (12) with a terminal equipment (16) each of said conductors having a four-layer diode switch (30,40) connected in series therewith, a method for determining whether a fault in said subscriber loop is located on either said central office side or said terminal equipment side of each of said diode switches CHARACTERIZED BY THE STEPS OF transmitting a first direct current signal having a voltage greater than the threshold voltage of said diode switches and an alternating current signal, simultaneously, between each of said conductors and ground, determining the impedance of each of said conductors to ground in response to said first direct current signal and said alternating current signal, and comparing said impedance values with unique signatures impedance termination networks (26,28) connected between said conductors and ground on the central office side of the diode switch, thereby determining (a) whether one of said impedance termination networks is connected to a respective one of said conductors, and (b) whether said conductors are open.
Claim 6
Dependent Claim
178 words
In a telephone subscriber loop comprising a plurality of conductors (11,13) connecting a telephone central office (12) with a terminal equipment (16) each of said conductors having a four-layer diode switch (30,40) connected in series therewith, a method for determining whether a fault in said subscriber loop is located on either said central office side or said terminal equipment side of each of said diode switches CHARACTERIZED BY THE STEPS OF transmitting a first direct current signal having a voltage greater than the threshold voltage of said diode switches and an alternating current signal, simultaneously, between each of said conductors and ground, determining the impedance of each of said conductors to ground in response to said first direct current signal and said alternating current signal, and comparing said impedance values with unique signatures impedance termination networks (26,28) connected between said conductors and ground on the central office side of the diode switch, thereby determining (a) whether one of said impedance termination networks is connected to a respective one of said conductors, and (b) whether said conductors are open.
Claim 7
Dependent Claim
40 words
The method for determining faults in said subscriber loop according to claim 4 further CHARACTERIZED BY THE STEPS OF detecting whether any direct current flow exists in any of said conductors, thereby determining whether any fault exists in said conductors.
Claim 8
Dependent Claim
90 words
The method for determining faults in said subscriber loop according to claim 5 further CHARACTERIZED BY THE STEPS OF disconnecting said first direct current signal and said alternating current signal from one of said conductors and connecting said one conductor to ground, detecting if there is any direct current flow in said conductor thereby inferring whether any direct current leak exists between said conductors, and determining the impedance of said loop thereby detecting whether any said terminal equipment is connected to said loop conductors or whether said loop is open.
Claim 9
Dependent Claim
99 words
The method for determining faults in said subscriber loop according to claim 6 further CHARACTERIZED BY THE STEPS OF disconnecting said first direct current signal, said alternating current signals, and said ground connection from said loop conductors, transmitting a second direct current signal having a voltage less than the threshold voltage of said diode switches simultaneously between each of said conductors and ground, and determining whether any direct current flow exists between any of said conductors and ground, thereby determining whether any fault exists to ground in any of said conductors between said central office and said diode switches.
Claim 10
Dependent Claim
65 words
The method for determining faults in said subscriber loop according to claim 7 further CHARACTERIZED BY THE STEPS OF disconnecting said second direct current signal from one of said conductors and connecting said one conductor to ground, and detecting whether a direct current flow exists in said loop for determining whether a leak exists between said conductors on the central office side of said switches.
Claim 11
Dependent Claim
143 words
A maintenance termination unit (MTU) connected by a tip conductor and ring conductor between a central office and terminal equipment, said MTU comprising protection equipment connected between said tip and ring conductors, substantially identical signature networks, one of said signature networks being connected between said tip conductor and ground, the other of said signature networks being connected between said ring conductor and ground, each of said signature networks comprising a resistor and a capacitor connected in series, and substantially identical voltage sensitive devices, each of said voltage sensitive devices being connected in series with either said tip conductor or said ring conductor, and each of said voltage sensitive devices comprising in parallel a capacitor and two four-layer diodes, said two four-layer diodes being connected in opposite polarities said substantially identical signature networks being connected on the central office side of the diode switch.
Claim 12
Dependent Claim
143 words
A maintenance termination unit (MTU) connected by a tip conductor and ring conductor between a central office and terminal equipment, said MTU comprising protection equipment connected between said tip and ring conductors, substantially identical signature networks, one of said signature networks being connected between said tip conductor and ground, the other of said signature networks being connected between said ring conductor and ground, each of said signature networks comprising a resistor and a capacitor connected in series, and substantially identical voltage sensitive devices, each of said voltage sensitive devices being connected in series with either said tip conductor or said ring conductor, and each of said voltage sensitive devices comprising in parallel a capacitor and two four-layer diodes, said two four-layer diodes being connected in opposite polarities said substantially identical signature networks being connected on the central office side of the diode switch.
References Cited (Backward Citations)
US3636280A
Cited
JPS55100773A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-02-07 | 1986-08-09 | 1987-02-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-02-07 | 1990-08-09 | 1991-02-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-02-07 | 1994-08-09 | 1995-02-08 | $7700.00 | Window Closed / Lapsed |