Patent US4025729A successfully refreshed from Google Patents.
US4025729A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Telephone ringing control circuits
Assignee: AT&T Inc
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Filing: 1975-12-05
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Granted: 1977-05-24
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Expires: 1995-12-05
Abstract
Abstract A single channel carrier system is disclosed including a remote terminal having a battery charger for charging a battery during idle periods to power the remote carrier electronics. The remote electronics include a ringing generator and a supervisory circuit to implement normal telephone supervision over the carrier channel. The ringing generator is a dc-to-dc converter for stepping the battery voltage up to the ringing voltage level. In order to interrupt this unipolar ringing voltage and thereby to energize the telephone ringer, a switching circuit is provided including a transistor in shunt with the ringing voltage supply to provide a return path for alternate half cycles of ringing current. A constant current source from a low voltage supply connected to the base of the transistor provides bias current to saturate the transistor yet minimizes the amount of dissipated power.
Inventors
- 👤 Dale Eugene Stone
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 12:52
CPC Classifications
H; H04; H04M; H04M19/00; H04M19/02; H04M19/04; H04M19/06
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
66 words
A switching circuit for supplying an alternating current to a load from a unidirectional source comprising a unidirectional source of intermittent voltage, a capacitor connected across said source, an alternating current load, a diode connecting said capacitor and said load in a series circuit, a transistor having its collector-emitter path connected across said load, and a constant current source connected to the base of said transistor.
Claim 2
Dependent Claim
66 words
A switching circuit for supplying an alternating current to a load from a unidirectional source comprising a unidirectional source of intermittent voltage, a capacitor connected across said source, an alternating current load, a diode connecting said capacitor and said load in a series circuit, a transistor having its collector-emitter path connected across said load, and a constant current source connected to the base of said transistor.
Claim 3
Dependent Claim
26 words
The switching circuit according to claim 1 wherein said unidirectional source comprises a direct current to direct current voltage level converter enabled at a preselected rate.
Claim 4
Dependent Claim
14 words
The switching circuit according to claim 1 wherein said load comprises a telephone ringer.
Claim 5
Dependent Claim
75 words
A ringing generator comprising a source of ringing voltage, a capacitor connected to be charged by said ringing voltage, a transistor connected to provide a return path for negative half cycles of said ringing voltage, said capacitor being connected between the base and collector of said transistor, a diode connected in parallel with and poled oppositely to the base-emitter junction of said transistor, and a constant current source connected to the base of said transistor.
Claim 6
Dependent Claim
75 words
A ringing generator comprising a source of ringing voltage, a capacitor connected to be charged by said ringing voltage, a transistor connected to provide a return path for negative half cycles of said ringing voltage, said capacitor being connected between the base and collector of said transistor, a diode connected in parallel with and poled oppositely to the base-emitter junction of said transistor, and a constant current source connected to the base of said transistor.
Claim 7
Dependent Claim
25 words
The ringing generator according to claim 4 wherein said source of ringing voltage comprises a direct current level converter enabled at a ringing signal rate.
Claim 8
Dependent Claim
51 words
A switching circuit for high power signals comprising a load for said signals, a power source to operate said load, a transistor switch connected in shunt with said source and said load, and a constant current source derived independently of said power source connected to the control electrode of said transistor.
Claim 9
Dependent Claim
51 words
A switching circuit for high power signals comprising a load for said signals, a power source to operate said load, a transistor switch connected in shunt with said source and said load, and a constant current source derived independently of said power source connected to the control electrode of said transistor.
References Cited (Backward Citations)
US3475561A
Cited
US3471650A
Cited
US3536852A
Cited
US3601538A
Cited
US3681621A
Cited
US3628066A
Cited
US3714469A
Cited
US3904833A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-05-23 | 1980-11-22 | 1981-05-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-05-23 | 1984-11-22 | 1985-05-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-05-23 | 1988-11-22 | 1989-05-24 | $7700.00 | Window Closed / Lapsed |