US3708741A
Expired / Lapsed
US
⏱️ 0.0 years remaining
D.c. to d.c. converter for connection across telephone lines
Assignee: Hekimian Laboratories Inc
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Filing: 1971-06-21
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Granted: 1973-01-02
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Expires: 1991-06-21
Abstract
Abstract D.C. supervisory signals control tones and audio signals appearing across a pair of balanced floating telephone lines are converted to permit processing by a single-ended grounded system. The converter circuit includes a high-impedance diode bridge full wave rectifier connected across the floating telephone lines and feeding a self-excited oscillator with an output signal amplitude substantially proportional to the D.C. voltage across the floating lines. The output signals from the rectifier and oscillator are passed through an isolation transformer to a single-ended detector which restores the supervisory signal D.C. level. The relatively high D.C. level of the supervisory signal acts to forward bias the rectifier and detector to pass the relatively low level audio signal and touch tones without distortion.
Inventors
- 👤 N Hekimian
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 19:47
CPC Classifications
H; H02; H02M; H02M3/00; H02M3/22; H02M3/24; H02M3/28; H02M3/325; H02M3/335; H02M3/338; H02M3/3381
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
180 words
A circuit for passing D.C. and audio signals appearing across a balanced pair of floating telephone lines, said circuit comprising: a pair of input terminals; a diode bridge full wave rectifier having a pair of input junctions and first and second output junctions; first and second equal resistors, each connected between a respective input terminal and input junction; a transistor having collector, emitter and base electrodes; an isolation transformer having a primary winding and a secondary winding; means connecting said primary winding and said collector and emitter electrodes in series across the first and second output junctions of said rectifier; capacitor means connected in circuit with said primary winding and said transistor to provide an LC oscillator having a frequency of oscillation dependent upon the voltage applied to said base electrode; means coupling said base electrode to said first output junction of said rectifier; a detector including a diode and capacitor connected in series in the order recited between one end of said secondary winding and ground; and means directly coupling the other end of said secondary winding to ground.
Claim 2
Dependent Claim
180 words
A circuit for passing D.C. and audio signals appearing across a balanced pair of floating telephone lines, said circuit comprising: a pair of input terminals; a diode bridge full wave rectifier having a pair of input junctions and first and second output junctions; first and second equal resistors, each connected between a respective input terminal and input junction; a transistor having collector, emitter and base electrodes; an isolation transformer having a primary winding and a secondary winding; means connecting said primary winding and said collector and emitter electrodes in series across the first and second output junctions of said rectifier; capacitor means connected in circuit with said primary winding and said transistor to provide an LC oscillator having a frequency of oscillation dependent upon the voltage applied to said base electrode; means coupling said base electrode to said first output junction of said rectifier; a detector including a diode and capacitor connected in series in the order recited between one end of said secondary winding and ground; and means directly coupling the other end of said secondary winding to ground.
Claim 3
Dependent Claim
178 words
A circuit for use in monitoring DC supervisory signals and relatively low frequency signals appearing across a pair of ungrounded lines, wherein the peak amplitude of said low frequency signals is less than the amplitude of said DC signals, said circuit comprising: ungrounded high impedance input means for receiving said DC and low frequency signals from said ungrounded lines; an ungrounded self-excited oscillator for providing an oscillatory signal having a relatively high oscillation frequency and an amplitude of oscillation which is a known function of the amplitude of a DC signal applied to said oscillator; means for applying the received DC signal to said oscillator; an isolation transformer for passing the received low frequency signal and said oscillatory signal; a detector arranged to receive the oscillatory signal passed by said transformer for providing a DC ground-referenced signal at a level which is a specified function of the amplitude of said oscillatory signal; and output means for providing an outpUt signal from said circuit which includes said low frequency signal passed by said transformer and said ground-referenced DC signal.
Claim 4
Dependent Claim
178 words
A circuit for use in monitoring DC supervisory signals and relatively low frequency signals appearing across a pair of ungrounded lines, wherein the peak amplitude of said low frequency signals is less than the amplitude of said DC signals, said circuit comprising: ungrounded high impedance input means for receiving said DC and low frequency signals from said ungrounded lines; an ungrounded self-excited oscillator for providing an oscillatory signal having a relatively high oscillation frequency and an amplitude of oscillation which is a known function of the amplitude of a DC signal applied to said oscillator; means for applying the received DC signal to said oscillator; an isolation transformer for passing the received low frequency signal and said oscillatory signal; a detector arranged to receive the oscillatory signal passed by said transformer for providing a DC ground-referenced signal at a level which is a specified function of the amplitude of said oscillatory signal; and output means for providing an outpUt signal from said circuit which includes said low frequency signal passed by said transformer and said ground-referenced DC signal.
Claim 5
Dependent Claim
37 words
The circuit according to claim 2 wherein the frequency response of said detector is low-pass in nature such that said low frequency signals are passed substantially unaffected from said transformer through said detector to said output means.
Claim 6
Dependent Claim
55 words
The circuit according to claim 2 wherein said detector includes a diode connected in series between said isolation transformer and said output means, and wherein the amplitude of said oscillatory signal passed by said isolation transformer is sufficiently high to forward bias said diode for passage of said low frequency signal to said output means.
Claim 7
Dependent Claim
63 words
The circuit according to claim 2 wherein said high impedance input means comprises a diode bridge full wave rectifier and a high impedance connected in series between each of said ungrounded lines and a respective opposite junction of said bridge, and wherein the amplitude of said DC supervisory signals is sufficiently high to forward bias said bridge to pass said low frequency signals.
Claim 8
Dependent Claim
80 words
The circuit according to claim 5 wherein said detector includes a diode connected in series between said isolation transformer and said output means and wherein the amplitude of said oscillatory signal passed by said isolation transformer is sufficiently high to forward bias said diode for passage of said low frequency signal to said output means, and wherein the frequency response of said detector is low-pass in nature such that said low frequency signals are passed substantially unaffected through said detector.
Claim 9
Dependent Claim
37 words
The circuit according to claim 6 wherein said output means includes an amplifier with a low-pass frequency characteristic for passing said ground-referenced DC signal and said low frequency signal and attenuating signals at said relatively high frequency.
Claim 10
Dependent Claim
22 words
The circuit according to claim 7 wherein said pair of ungrounded lines are the ring and tip lines of subscriber telephone set.
Claim 11
Dependent Claim
22 words
The circuit according to claim 2 wherein said pair of ungrounded lines are the ring and tip lines of subscriber telephone set.
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) | 1976-01-02 | 1976-07-03 | 1977-01-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-01-02 | 1980-07-03 | 1981-01-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-01-02 | 1984-07-03 | 1985-01-02 | $7700.00 | Window Closed / Lapsed |