US4093829A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Single line telephone hold circuit
Assignee: Individual
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Filing: 1977-03-14
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Granted: 1978-06-06
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Expires: 1997-03-14
Abstract
Abstract A solid-state circuit for maintaining line current in a two-wire telephone line placed on "HOLD" by the subscriber. A shunt impedance is connected in series with a pair of transistor switches, the first of which conducts only when the telephone line voltage is lower than a predetermined value and the second of which conducts whenever a momentary contact switch is manually actuated. The second transistor continues to conduct until a subsequent substantial decrease in telephone line voltage, indicative of a renewed off-hook condition, is detected.
Inventors
- 👤 Robert L. Silberman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 11:47
CPC Classifications
H; H04; H04M; H04M3/00; H04M3/42; H04M3/428; H04M3/4283
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
139 words
In combination with a two-wire telephone line connecting at least one telephone station set to a central exchange, an auxiliary hold circuit for maintaining line-current when said station set is placed in an on-hook state to prevent undesired disconnection of an active call at said central exchange, said hold circuit comprising, in combination, first and second semiconductor switching devices serially connected with a shunt impedance across said two-wire line; means for rendering said first semiconductor switching device conductive whenever the voltage across said two-wire line is less than a predetermined value; manually-operated switching means for rendering said second semiconductor switching device conductive to connect said shunt impedance across said line; and a control circuit for rendering said second device nonconductive whenever the voltage across said line exhibits a substantial decrease while said shunt impedance is connected across said line.
Claim 2
Dependent Claim
139 words
In combination with a two-wire telephone line connecting at least one telephone station set to a central exchange, an auxiliary hold circuit for maintaining line-current when said station set is placed in an on-hook state to prevent undesired disconnection of an active call at said central exchange, said hold circuit comprising, in combination, first and second semiconductor switching devices serially connected with a shunt impedance across said two-wire line; means for rendering said first semiconductor switching device conductive whenever the voltage across said two-wire line is less than a predetermined value; manually-operated switching means for rendering said second semiconductor switching device conductive to connect said shunt impedance across said line; and a control circuit for rendering said second device nonconductive whenever the voltage across said line exhibits a substantial decrease while said shunt impedance is connected across said line.
Claim 3
Dependent Claim
33 words
Apparatus as set forth in claim 1 including a capacitive time-delay network and a comparator connected to render said second switch nonconductive whenever the voltage across said two-wire line exhibits a substantial decrease.
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) | 1981-06-05 | 1981-12-05 | 1982-06-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-06-05 | 1985-12-05 | 1986-06-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-06-05 | 1989-12-05 | 1990-06-06 | $7700.00 | Window Closed / Lapsed |