US3673330A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Two-party automatic number identification in subscriber carrier telephone system
Assignee: Telent Technologies Services Ltd
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Filing: 1970-09-18
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Granted: 1972-06-27
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Expires: 1990-09-18
Abstract
Abstract Automatic number identification for two subscribers who share a single channel in a subscriber carrier system. A d.c. ground connection is made to the subset of one of the two subscribers but not to the other''s. When the subscriber having the ground connection goes offhook, initiating transmission of the inbound carrier signal, the subscriber equipment modulates the inbound carrier for a brief interval with a signal at a frequency higher than the highest voice signal permitted on the line. The subscriber carrier terminal equipment at the central office responds to the modulating signal by actuating a relay which remains held up for the duration of the call and effects a ground connection detectable by the conventional automatic number identification equipment at the central office. If the nongrounded subscriber goes offhook, the inbound carrier signal is not modulated and the relay at the central office remains nonenergized. The system is not susceptible to ''''talk-down,'''' because the modulating signal is outside the pass band provided for transmitting voice signals. The circuit for sensing which of the two subscribers is offhook includes a transistor, means for grounding the base of the transistor during the identification interval, and means connecting an unreferenced source of direct current between the collector and emitter of the transistor in series with a relay winding. If the offhook subscriber has a d.c. ground connection, the current source becomes referenced by it, and the transistor becomes biased to saturation and conducts current to energize the relay. If the subscriber does not have a ground connection, the current source is referenced only through the base connection and the transistor does not conduct.
Inventors
- 👤 Morris A Suntop
- 👤 Uno Randmere
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 17:53
CPC Classifications
H; H04; H04Q; H04Q11/00; H04Q11/02; H01; H01J; H01J1/00; H01J1/02; H01J1/13; H01J1/14; H04Q5/00; H04Q5/24
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
238 words
A circuit arrangement for automatic number identification between two subscribers who share a single channel in a subscriber carrier telephone system of the frequency-divided type in which two carrier signals are provided for each channel, one carrier for transmission from a central office terminal to a subscriber terminal shared by said two subscribers and the other carrier for transmission in the opposite direction, said arrangement comprising: a. means providing a d.c. ground connection to the tip and ring leads at the subset of one of the two subscribers who share the channel, the ground connection being through the subscribers'' hookswitch contacts, the other subscriber being without a d.c. ground connection, b. an oscillator at the subscriber terminal connected selectively to modulate the subscriber terminal-to-central office terminal carrier, c. a detector at the subscriber terminal responsive to initiation of an offhook condition to energize said oscillator for a predetermined brief interval following the initiation of an offhook condition if the offhook condition is at the grounded subset, and to hold said oscillator de-energized at all other times, d. means at the central office terminal to demodulate the carrier signal received from the subscriber terminal and to detect the presence therein of a signal produced by said oscillator, and e. means responsive to said demodulating and detecting means for effecting a d.c. ground connection at the central office terminal readable by a conventional number identification system in the central office.
Claim 2
Dependent Claim
238 words
A circuit arrangement for automatic number identification between two subscribers who share a single channel in a subscriber carrier telephone system of the frequency-divided type in which two carrier signals are provided for each channel, one carrier for transmission from a central office terminal to a subscriber terminal shared by said two subscribers and the other carrier for transmission in the opposite direction, said arrangement comprising: a. means providing a d.c. ground connection to the tip and ring leads at the subset of one of the two subscribers who share the channel, the ground connection being through the subscribers'' hookswitch contacts, the other subscriber being without a d.c. ground connection, b. an oscillator at the subscriber terminal connected selectively to modulate the subscriber terminal-to-central office terminal carrier, c. a detector at the subscriber terminal responsive to initiation of an offhook condition to energize said oscillator for a predetermined brief interval following the initiation of an offhook condition if the offhook condition is at the grounded subset, and to hold said oscillator de-energized at all other times, d. means at the central office terminal to demodulate the carrier signal received from the subscriber terminal and to detect the presence therein of a signal produced by said oscillator, and e. means responsive to said demodulating and detecting means for effecting a d.c. ground connection at the central office terminal readable by a conventional number identification system in the central office.
Claim 3
Dependent Claim
153 words
A circuit arrangement according to claim 1, wherein the subscriber terminal includes a battery and means for isolating the battery from all d.c. reference potentials except through the line leading to the subscribers, and said detector at the subscriber terminal comprises: a. a transistor, b. d.c. resistive means connected between the base and emitter of said transistor, c. a relay, d. means for connecting said relay in series with the collector-to-emitter path of said transistor and the battery, and e. means for connecting the base of said transistor to a d.c. reference leaving the battery isolated from all d.c. references except through said transistor and the line, whereby when the subscriber having the d.c. ground connection goes offHook, said transistor will conduct and said relay will be energized, and when only the subscriber without a ground connection goes offhook the only d.c. reference is through said transistor and said transistor will not conduct.
Claim 4
Dependent Claim
174 words
A ground detector circuit for use in a telephone system of the kind including a battery and a subscribers'' line shared by two subscribers, means for isolating the battery from all d.c. reference potentials except through the line, means connecting a d.c. reference to the line through the hookswitch of one of the subscribers'' subsets, and means isolating the other subscriber''s subset from a d.c. reference, said detector circuit comprising: a. a transistor, b. d.c. resistive means connected between the base and emitter of said transistor, c. a relay, d. means for connecting said relay in series with the collector-to-emitter path of said transistor and the battery, e. means for connecting the base of said transistor to a d.c. reference leaving the battery isolated from all d.c. references except through said transistor and the line, whereby when the referenced subscriber goes offhook, said transistor will conduct and said relay will be energized, and when only the unreferenced subscriber goes offhook the only d.c. reference is through said transistor and said transistor will not conduct.
Claim 5
Dependent Claim
174 words
A ground detector circuit for use in a telephone system of the kind including a battery and a subscribers'' line shared by two subscribers, means for isolating the battery from all d.c. reference potentials except through the line, means connecting a d.c. reference to the line through the hookswitch of one of the subscribers'' subsets, and means isolating the other subscriber''s subset from a d.c. reference, said detector circuit comprising: a. a transistor, b. d.c. resistive means connected between the base and emitter of said transistor, c. a relay, d. means for connecting said relay in series with the collector-to-emitter path of said transistor and the battery, e. means for connecting the base of said transistor to a d.c. reference leaving the battery isolated from all d.c. references except through said transistor and the line, whereby when the referenced subscriber goes offhook, said transistor will conduct and said relay will be energized, and when only the unreferenced subscriber goes offhook the only d.c. reference is through said transistor and said transistor will not conduct.
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) | 1975-06-27 | 1975-12-27 | 1976-06-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-27 | 1979-12-27 | 1980-06-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-27 | 1983-12-27 | 1984-06-27 | $7700.00 | Window Closed / Lapsed |