US4491689A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Amplifier for use with telephone transmitter mounted in hand held telephone unit
Assignee: AG Communication Systems Corp
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Filing: 1983-05-02
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Granted: 1985-01-01
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Expires: 2003-05-02
Abstract
Abstract An amplifier for use with an electret microphone utilized as a telephone transmitter in a hand held telephone unit or handset. Incorporated into the circuitry is a band pass filter which substantially inhibits feedback "singing" which occurs because of reflection when the handset or telephone unit is placed in a downward position on a hard surface or similar environment. The filter circuitry employs the source resistance of the telephone transmitter and the input resistance of a transistor amplifier stage as elements of the included filter circuitry.
Inventors
- 👤 Eduard F. B. Boeckman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 11:50
CPC Classifications
H; H04; H04M; H04M1/00; H04M1/60; H04M1/6008; H04M1/02; H04M1/20
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
140 words
In combination, a telephone line, a hand held telephone unit including a telephone receiver and a telephone transmitter, connected to said telephone line, and an amplifier for said transmitter, said amplifier comprising: first and second circuit connections to a source of DC power; a transistor stage including an input and an output; a first filter element including said telephone transmitter; a second filter element connected between first filter element and said transistor stage input; a third filter element connected between said transistor stage input and said first circuit connection to said DC power source; and a fourth filter element including said transistor stage; said first, second, third and fourth filter elements in combination, comprising a band pass filter controlling the high and low frequency response of said telephone transmitter, whereby feedback oscillation coupled to said telephone receiver is substantially inhibited.
Claim 2
Dependent Claim
140 words
In combination, a telephone line, a hand held telephone unit including a telephone receiver and a telephone transmitter, connected to said telephone line, and an amplifier for said transmitter, said amplifier comprising: first and second circuit connections to a source of DC power; a transistor stage including an input and an output; a first filter element including said telephone transmitter; a second filter element connected between first filter element and said transistor stage input; a third filter element connected between said transistor stage input and said first circuit connection to said DC power source; and a fourth filter element including said transistor stage; said first, second, third and fourth filter elements in combination, comprising a band pass filter controlling the high and low frequency response of said telephone transmitter, whereby feedback oscillation coupled to said telephone receiver is substantially inhibited.
Claim 3
Dependent Claim
19 words
In combination as claimed in claim 1 wherein: said first filter element comprises the resistance of said telephone transmitter.
Claim 4
Dependent Claim
25 words
The combination as claimed in claim 2 wherein: there is further included an additional resistance connected between said telephone transmitter and said second filter element.
Claim 5
Dependent Claim
15 words
The combination as claimed in claim 2 wherein: said second filter element comprises a capacitor.
Claim 6
Dependent Claim
15 words
The combination as claimed in claim 1 wherein: said third filter element comprises a capacitor.
Claim 7
Dependent Claim
89 words
The combination as claimed in claim 1 wherein: said transistor stage comprises a transistor including first, second and third electrodes; a load resistance connected between said second circuit connection to said source of DC power and said second electrode; a bias resistance connected between said third electrode and said first circuit connection to said DC power source; and a feedback resistance connected between said second electrode and said first electrode; said transistor stage input connected to said first electrode and said transistor stage output connected to said second electrode.
Claim 8
Dependent Claim
20 words
The combination as claimed in claim 6 wherein: said fourth filter element comprises the resistance of said transistor stage input.
References Cited (Backward Citations)
US4414433A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-01-01 | 1988-07-02 | 1989-01-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-01-01 | 1992-07-02 | 1993-01-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-01-01 | 1996-07-02 | 1997-01-01 | $7700.00 | Window Closed / Lapsed |