US3671676A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Subscriber loop range extender
Assignee: AT&T Inc
•
Filing: 1969-12-17
•
Granted: 1972-06-20
•
Expires: 1989-12-17
Abstract
Abstract This disclosure describes a telephone subscriber loop range extender having a signaling mode and a transmission mode. In the former, a resistive shunt is applied across the loop with each dial pulse to aid operation of the pulsing relay for an originating cell. For a terminating call, the shunt is applied upon answer, either during ringing or during the silent interval, to aid operation of the ring-trip relay. In the transmission mode, voice frequency gain and greater transmitter voltage are applied to the loop. A control circuit consisting of logic, timing and relay driving circuits, acts upon loop voltage and current data to control shunt action and mode selection.
Inventors
- 👤 James L Henry
- 👤 Luther G Schimpf
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 13:26
CPC Classifications
H; H04; H04M; H04M19/00; H04M19/001; H04M19/006
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
207 words
A telephone subscriber loop range extender comprising: input and output terminals serially connected in said loop, a shunt circuit connected across said loop and comprising a resistive element and a first contact, a first relay for controlling said first contact, a first AND gate with means connecting the output of said first AND gate to said first relay, said gate fed with first, second, and third input signals and including means for logically inverting said second and third input signals, a loop current detector comprising first and second means responsive to loop current flow for generating first and second signals each proportional to loop current, said first signal reporting loop current substantially instantaneously and said second signal having a delayed response, said second means further comprising means for substantially filtering out ringing current, a pulsing level detector, responsive to values of said first signal from said loop current detector greater than preselected threshold levels for generating said first AND gate input signal, a line voltage detector responsive to either ringing voltage or relay surge voltage for generating said second AND gate input signal, and a ringing presence detector connected to said line voltage detector and responsive to ringing voltage for generating said third AND gate input signal.
Claim 2
Dependent Claim
207 words
A telephone subscriber loop range extender comprising: input and output terminals serially connected in said loop, a shunt circuit connected across said loop and comprising a resistive element and a first contact, a first relay for controlling said first contact, a first AND gate with means connecting the output of said first AND gate to said first relay, said gate fed with first, second, and third input signals and including means for logically inverting said second and third input signals, a loop current detector comprising first and second means responsive to loop current flow for generating first and second signals each proportional to loop current, said first signal reporting loop current substantially instantaneously and said second signal having a delayed response, said second means further comprising means for substantially filtering out ringing current, a pulsing level detector, responsive to values of said first signal from said loop current detector greater than preselected threshold levels for generating said first AND gate input signal, a line voltage detector responsive to either ringing voltage or relay surge voltage for generating said second AND gate input signal, and a ringing presence detector connected to said line voltage detector and responsive to ringing voltage for generating said third AND gate input signal.
Claim 3
Dependent Claim
93 words
A range extender as per claim 1, further comprising: a signaling path and a transmission path, means connected in said transmission path for effecting voice frequency gain, transfer switch means for connecting said loop through said signaling or said transmission path, a second relay controlling said transfer switch means which when operated establishes said transmission path, and which when unoperated establishes said signaling path, and means including a timer connecting said first AND gate output and said second relay, energizing of said first AND gate effecting a delayed operation of said second relay.
Claim 4
Dependent Claim
93 words
A range extender as per claim 2, wherein said connecting means comprises: a two-input OR gate for controlling said first relay, said OR gate having a first input from said first AND gate, said range extender further comprising a second AND gate providing a second input to Said OR gate and itself having a first input from said ringing presence detector and a second input, and a ring-trip level detector comprising means responsive to values of said second loop current detector output signal above a selected level for generating said last-named second input.
Claim 5
Dependent Claim
29 words
A range extender in accordance with claim 3, wherein said transfer switch means further comprises a break contact in the connection between said first relay and said OR gate.
Claim 6
Dependent Claim
33 words
A range extender in accordance with claim 4, wherein the response of said loop current detector second signal has a rise time of from 25 to 500 milliseconds and a like fall time.
Claim 7
Dependent Claim
26 words
A range extender in accordance with claim 4, wherein said timer comprises means effecting a delay of 100-150 milliseconds in the operation of said second relay.
Claim 8
Dependent Claim
41 words
A range extender in accordance with claim 4, wherein said means for effecting voice frequency gain comprises a series negative impedance gain unit and a shunt negative impedance gain unit for providing variable loop gain as a function of loop resistance.
Claim 9
Dependent Claim
164 words
A range extender in accordance with claim 4, wherein said loop current detector first output signal generating means comprises: circuit means comprising first and second low resistance elements connected in tip-and-ring leads of said loop, and a pair of branch circuits cross-connected with respect to said first and second low resistance elements and each including first and second high resistance elements, for sensing loop current and concurrently canceling the effect of longitudinal current on said first output signal; a network comprising first and second paths connected to the respective midpoints of said branch circuits and a pair of oppositely poled diodes connected in shunt relation across said first and second paths, the dc loop current tending to forward-bias one of said diodes; a medium frequency sine wave signal source; and a high voltage isolation coupling circuit connecting said source to said first and second paths, said coupling circuit transferring energy from said source to said output through said diodes in response to loop current.
Claim 10
Dependent Claim
44 words
A range extender in accordance with claim 8, wherein said loop current detector second output signal operating means comprises a circuit substantially identical to that recited in claim 8, and which further comprises means for preventing said diodes from being forward-biased by ringing current.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-06-20 | 1975-12-20 | 1976-06-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-20 | 1979-12-20 | 1980-06-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-20 | 1983-12-20 | 1984-06-20 | $7700.00 | Window Closed / Lapsed |