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 07:53
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.
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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 |