US4389543A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Telephone-activated audio control circuit
Assignee: Individual
•
Filing: 1980-12-18
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Granted: 1983-06-21
•
Expires: 2000-12-18
Abstract
Abstract The inputs of an operational amplifier are connected across a telephone line and bridged by a capacitor. The output of the operational amplifier drives the coil of a relay via an intermediate amplifier. The relay is of the make-before-break type, and is interposed between an audio source, audio speakers, and dummy load resistors. When the voltage across the telephone line indicates an on-hook condition for a telephone, the audio source is connected to the speakers through the relay. When the voltage across the telephone lines indicates an off-hook condition of the telephone, the audio source is connected to the dummy resistors and disconnected from the speakers and is thereby muted, enabling telephone conversation to take place.
Inventors
- 👤 Martus Granirer
- 👤 Andrew Jason
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 10:26
CPC Classifications
H; H04; H04M; H04M11/00; H04M1/00; H04M1/82
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
122 words
A circuit for use with telephone lines and the like, designed to mute an audio source after a telephone receiver has been taken off the hook, comprising: a high-impedance front end which can be connected across a telephone line and which can respond to voltage changes thereacross; a comparator connected to the front end and comparing voltage across the telephone line to a voltage reference source, the comparator having an output at which a control voltage proportional to a difference between the voltage reference source and voltage across the telephone line appears; and control means coupled to the output of said comparator and connected to said audio source to activate or deactivate the source in response to changes in said control voltage.
Claim 2
Dependent Claim
122 words
A circuit for use with telephone lines and the like, designed to mute an audio source after a telephone receiver has been taken off the hook, comprising: a high-impedance front end which can be connected across a telephone line and which can respond to voltage changes thereacross; a comparator connected to the front end and comparing voltage across the telephone line to a voltage reference source, the comparator having an output at which a control voltage proportional to a difference between the voltage reference source and voltage across the telephone line appears; and control means coupled to the output of said comparator and connected to said audio source to activate or deactivate the source in response to changes in said control voltage.
Claim 3
Dependent Claim
30 words
The circuit defined by claim 1, wherein the front end contains an AC bypass path, whereby the circuit is made responsive to changes in DC voltage across the telephone line.
Claim 4
Dependent Claim
31 words
The circuit defined by claim 2, wherein the AC bypass path operates as a time delay which delays response of the circuit to an increase in voltage across the telephone line.
Claim 5
Dependent Claim
21 words
The circuit defined by claim 1, wherein said control means includes a relay with a coil responsive to the control voltage.
Claim 6
Dependent Claim
15 words
The circuit defined by claim 4, further including a reverse-biased diode connected across the coil.
Claim 7
Dependent Claim
14 words
The circuit defined by claim 4, wherein the relay is of a make-before-break type.
Claim 8
Dependent Claim
20 words
The circuit defined by claim 4, further including an amplifier interposed between said output or the comparator and the coil.
Claim 9
Dependent Claim
12 words
The circuit defined by claim 7, wherein the amplifier is a transistor.
Claim 10
Dependent Claim
13 words
The circuit defined by claim 1, wherein the comparator is an operational amplifier.
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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) | 1986-06-20 | 1986-12-20 | 1987-06-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-06-20 | 1990-12-20 | 1991-06-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-06-20 | 1994-12-20 | 1995-06-21 | $7700.00 | Window Closed / Lapsed |