US3789803A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Inductor-less telephone line holding circuit giving high a.c. shunt impedances
Assignee: General Datacomm Inc
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Filing: 1971-11-15
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Granted: 1974-02-05
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Expires: 1991-11-15
Abstract
Abstract A circuit is disclosed for eliminating the inductor ordinarily used to provide large A.C. shunt impedances in a telephone line holding circuit. A relatively low resistance path through the output of an amplifier and one of its voltage supply inputs shunts the input of the line holding circuit. The input is also shunted by a phase shifting and voltage dividing network that phase shifts the input A.C. signal to cause the current signal to lead the voltage signal. The phase shifted signal is applied to the input of the amplifier. The amplifier has a gain of one and the voltage of the signal applied to it approaches the voltage at the input to the circuit. As a result, the A.C. signal voltage at the output of the amplifier has a magnitude and phase relation with respect to that of the input signal that produces a high A.C. shunt impedance.
Inventors
- 👤 S Davis
- 👤 S Domyan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 09:09
CPC Classifications
H; H04; H04M; H04M3/00; H04M3/42; H04M3/58
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
134 words
A telephone line holding circuit providing large A.C. shunt impedances comprising: an input having first and second leads; an output connected between said first and second input leads; an amplifier having a gain of one; a relatively low resistance D.C. path shunting said two leads, said path passing from said first input lead, through a resistor, the output of the amplifier and a voltage supply input to the amplifier, to said second input lead; and means connected between at least one input lead and an input to said amplifier for introducing a phase shift in an input A.C. signal such that the current leads the voltage at the input to the amplifier while also providing that the A.C. signal voltage at said amplifier input approaches the voltage across the first and second input leads.
Claim 2
Dependent Claim
134 words
A telephone line holding circuit providing large A.C. shunt impedances comprising: an input having first and second leads; an output connected between said first and second input leads; an amplifier having a gain of one; a relatively low resistance D.C. path shunting said two leads, said path passing from said first input lead, through a resistor, the output of the amplifier and a voltage supply input to the amplifier, to said second input lead; and means connected between at least one input lead and an input to said amplifier for introducing a phase shift in an input A.C. signal such that the current leads the voltage at the input to the amplifier while also providing that the A.C. signal voltage at said amplifier input approaches the voltage across the first and second input leads.
Claim 3
Dependent Claim
117 words
The line holding circuit of claim 1 wherein: said means connected between at least one input lead and an input to said amplifier comprises a first resistor and a first capacitor connected in parallel and a second resistor connected in series to the parallel combination of the first resistor and the first capacitor, thereby defining a node between one end of the second resistor and one end of both the first resistor and first capacitor; the other end of both the first resistor and first capacitor is connected to the first lead and the other end of the second resistor is connected to the second lead; and the input to the amplifier is connected to said node.
Claim 4
Dependent Claim
17 words
The line holding circuit of claim 2 wherein the first and second resistors have approximately equal resistance.
Claim 5
Dependent Claim
20 words
The line holding circuit of claim 1 further comprising a blocking capacitor that blocks a D.C. signal from the output.
Claim 6
Dependent Claim
54 words
The line holding circuit of claim 1 wherein: the input comprises two leads, one of which is more positive than the other; and the amplifier has a positive voltage supply terminal that is connected to the more positive input lead and a negative supply terminal that is connected to the less positive input lead.
Claim 7
Independent Claim
114 words
A method of eliminating the use of an inductor in a telephone line holding circuit to provide high A.C. shunt impedances comprising the steps of: establishing across first and second input leads to the circuit a low resistance D.C. shunt path passing from the first input lead, through a resistor, the output of an amplifier having a gAin of one and a voltage supply input to the amplifier, to the second input lead; phase shifting an A.C. input signal to cause the A.C. current to lead the A.C. voltage; and applying to an input to the amplifier the phase shifted A.C. signal at a voltage approaching that across the first and second input leads.
Claim 8
Independent Claim
114 words
A method of eliminating the use of an inductor in a telephone line holding circuit to provide high A.C. shunt impedances comprising the steps of: establishing across first and second input leads to the circuit a low resistance D.C. shunt path passing from the first input lead, through a resistor, the output of an amplifier having a gAin of one and a voltage supply input to the amplifier, to the second input lead; phase shifting an A.C. input signal to cause the A.C. current to lead the A.C. voltage; and applying to an input to the amplifier the phase shifted A.C. signal at a voltage approaching that across the first and second input leads.
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) | 1977-02-04 | 1977-08-06 | 1978-02-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-04 | 1981-08-06 | 1982-02-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-04 | 1985-08-06 | 1986-02-05 | $7700.00 | Window Closed / Lapsed |