US3576450A
Expired / Lapsed
US
⏱️ 0.0 years remaining
System for remote testing of telephone subscribers lines
Assignee: AT&T Inc
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Filing: 1968-01-22
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Granted: 1971-04-27
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Expires: 1988-01-22
Abstract
Abstract In a system for remote testing of telephone subscribers'' lines as disclosed in U.S. Pat. No. 3,410,966, a lockout selector device is provided which selects one control signal at random from a plurality of possible control signals. The lockout selector device locks out all other control signals while the selected control signal is transmitted for a prescribed duration, and then proceeds to select the remaining control signals at random, one at a time, for similar transmission. Specifically, an array of PNPN junction diodes is connected through a common load impedance to a common voltage supply. The other terminals of these diodes are selectively grounded by requests for signals.
Inventors
- 👤 Chauncey R Davies
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 05:41
CPC Classifications
H; H04; H04M; H04M3/00; H04M3/22; H04M3/26; H04M3/28; H04M3/30
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
240 words
A selector circuit comprising a plurality of control circuits, an equal plurality of negative resistance devices having first and second terminals and having two stable regions of positive resistance separated by an unstable region of negative resistance, an equal plurality of series resistances each having first and second terminals, a load impedance having first and second terminals and comprising an inductive element in series with a resistive element, a source of operating voltage, a source of reference potential, means for connecting said first terminal of each of said negative resistance devices to said first terminal of said load impedance, means for connecting said second terminal of said load impedance to said source of operating voltage, means for connecting said second terminal of each of said negative resistance devices to said first terminal of a corresponding one of said series resistances, means for selectively connecting said second terminal of each of said series resistances to said source of reference potential, and a combination for selectively enabling one of said plurality of control circuits in response to the transition of a corresponding one of said devices from one of said stable regions to the other of said stable regions, said combination comprising a plurality of transistors, each of which is uniquely associated with a corresponding one of said series resistances, and means for connecting the emitter and base electrodes of each of said transistors across the corresponding one of said series resistances.
Claim 2
Dependent Claim
240 words
A selector circuit comprising a plurality of control circuits, an equal plurality of negative resistance devices having first and second terminals and having two stable regions of positive resistance separated by an unstable region of negative resistance, an equal plurality of series resistances each having first and second terminals, a load impedance having first and second terminals and comprising an inductive element in series with a resistive element, a source of operating voltage, a source of reference potential, means for connecting said first terminal of each of said negative resistance devices to said first terminal of said load impedance, means for connecting said second terminal of said load impedance to said source of operating voltage, means for connecting said second terminal of each of said negative resistance devices to said first terminal of a corresponding one of said series resistances, means for selectively connecting said second terminal of each of said series resistances to said source of reference potential, and a combination for selectively enabling one of said plurality of control circuits in response to the transition of a corresponding one of said devices from one of said stable regions to the other of said stable regions, said combination comprising a plurality of transistors, each of which is uniquely associated with a corresponding one of said series resistances, and means for connecting the emitter and base electrodes of each of said transistors across the corresponding one of said series resistances.
Claim 3
Dependent Claim
17 words
The selector circuit according to claim 1 wherein said negative resistance devices comprise PNPN semiconductor junction diodes.
Claim 4
Dependent Claim
217 words
A lockout selector circuit comprising a plurality of control circuits to be selected one at a time, a corresponding plurality of devices each having two regions of stable positive resistance separated by a region of unstable dynamic negative resistance, a corresponding plurality of series resistances, a source of potential, a common load impedance comprising an inductive element in series with a resistive element, primary means for connecting said source of potential in series with said common load impedance to form a series combination of source of potential and load impedance, a plurality of secondary connecting means, each connecting in series one of said devices, a corresponding one of said series resistances, and said series combination of source of potential and load impedance, means including a plurality of selector switches for selectively enabling said secondary connecting means, and a combination for selectively enabling one of said plUrality of control circuits in response to the transition of a corresponding one of said devices from one of said stable regions to the other of said stable regions, said combination comprising a plurality of transistors, each of which is uniquely associated with a corresponding one of said series resistances, and means for connecting the emitter and base electrodes of each of said transistors across the corresponding one of said series resistances.
Claim 5
Dependent Claim
217 words
A lockout selector circuit comprising a plurality of control circuits to be selected one at a time, a corresponding plurality of devices each having two regions of stable positive resistance separated by a region of unstable dynamic negative resistance, a corresponding plurality of series resistances, a source of potential, a common load impedance comprising an inductive element in series with a resistive element, primary means for connecting said source of potential in series with said common load impedance to form a series combination of source of potential and load impedance, a plurality of secondary connecting means, each connecting in series one of said devices, a corresponding one of said series resistances, and said series combination of source of potential and load impedance, means including a plurality of selector switches for selectively enabling said secondary connecting means, and a combination for selectively enabling one of said plUrality of control circuits in response to the transition of a corresponding one of said devices from one of said stable regions to the other of said stable regions, said combination comprising a plurality of transistors, each of which is uniquely associated with a corresponding one of said series resistances, and means for connecting the emitter and base electrodes of each of said transistors across the corresponding one of said series resistances.
Claim 6
Dependent Claim
55 words
The lockout selector circuit according to claim 3 further including timing means, means responsive to the enablement of any one of said control circuits for triggering said timing means, and means responsive to a delayed output from said timing means for disabling said connecting means corresponding to the enabled one of said secondary control circuits.
Claim 7
Dependent Claim
18 words
The lockout selector circuit according to claim 3 wherein said devices each comprise a PNPN semiconductor junction diode.
References Cited (Backward Citations)
USRE24303E
Cited
US3015755A
Cited
US2855524A
Cited
US3177036A
Cited
US3133204A
Cited
US3382371A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-04-26 | 1974-10-26 | 1975-04-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-04-26 | 1978-10-26 | 1979-04-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-04-26 | 1982-10-26 | 1983-04-27 | $7700.00 | Window Closed / Lapsed |