US3801974A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Voltage responsive alarm system for telephone lines
Assignee: Applied Sciences Inc
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Filing: 1972-03-06
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Granted: 1974-04-02
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Expires: 1992-03-06
Abstract
Abstract An electrical alarm system is provided for responding to a telephone communication line normally having an operating voltage of predetermined magnitude to indicate loss of or removal of this voltage. This system includes an electrical power supply for energizing alarm apparatus independently of the telephone communication line voltage and a switching circuit responsive to the line voltage and operable to interconnect the power supply and alarm apparatus for energization thereof when the telephone communication line voltage has been removed or otherwise eliminated. The switching circuit includes a solid state switching device that is normally biased to a non-conducting state through a biasing circuit having voltage limiting and regulating means and a full wave rectifier.
Inventors
- 👤 D Aitken
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 04:48
CPC Classifications
G; G08; G08B; G08B21/00; G08B21/18; G08B21/185; H; H04; H04M; H04M1/00; H04M1/82
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
175 words
An electrical alarm system for responding to loss of communication lIne voltage comprising: A. an electrical power supply, B. alarm apparatus selectively connectable with said power supply to receive electrical power for energization, C. a switching circuit interconnected with said power supply and alarm apparatus and operable to effect selective energization thereof, said switching circuit including: 1. normally closed switch means responsive to a biasing voltage to switch to an open, non-conducting state, said switch means operatively connected to said power supply and said alarm apparatus for selective interconnection thereof, and 2. a voltage biasing circuit electrically isolated from said power supply adapted to be connected to a communication line and connected with said switch means to provide a biasing voltage to said switch means independent of the magnitude of said power source when a voltage is impressed on the communication line, said biasing circuit including a voltage rectifier connected in preceding relationship to said switch means and voltage regulating means limiting the biasing voltage applied to said switch means to a predetermined maximum value.
Claim 2
Dependent Claim
175 words
An electrical alarm system for responding to loss of communication lIne voltage comprising: A. an electrical power supply, B. alarm apparatus selectively connectable with said power supply to receive electrical power for energization, C. a switching circuit interconnected with said power supply and alarm apparatus and operable to effect selective energization thereof, said switching circuit including: 1. normally closed switch means responsive to a biasing voltage to switch to an open, non-conducting state, said switch means operatively connected to said power supply and said alarm apparatus for selective interconnection thereof, and 2. a voltage biasing circuit electrically isolated from said power supply adapted to be connected to a communication line and connected with said switch means to provide a biasing voltage to said switch means independent of the magnitude of said power source when a voltage is impressed on the communication line, said biasing circuit including a voltage rectifier connected in preceding relationship to said switch means and voltage regulating means limiting the biasing voltage applied to said switch means to a predetermined maximum value.
Claim 3
Dependent Claim
28 words
An electrical system according to claim 1 wherein said switch means is a solid state switching device having emitter-base terminals, said biasing circuit connected across said emitter-base terminals.
Claim 4
Dependent Claim
83 words
a voltage biasing circuit electrically isolated from said power supply adapted to be connected to a communication line and connected with said switch means to provide a biasing voltage to said switch means independent of the magnitude of said power source when a voltage is impressed on the communication line, said biasing circuit including a voltage rectifier connected in preceding relationship to said switch means and voltage regulating means limiting the biasing voltage applied to said switch means to a predetermined maximum value.
Claim 5
Dependent Claim
83 words
a voltage biasing circuit electrically isolated from said power supply adapted to be connected to a communication line and connected with said switch means to provide a biasing voltage to said switch means independent of the magnitude of said power source when a voltage is impressed on the communication line, said biasing circuit including a voltage rectifier connected in preceding relationship to said switch means and voltage regulating means limiting the biasing voltage applied to said switch means to a predetermined maximum value.
Claim 6
Dependent Claim
40 words
An electrical alarm system according to claim 2 wherein said biasing circuit includes a solid state diode connected across said emitter-base terminals to provide a reverse bias to the switching device when said diode is conducting in a forward direction.
Claim 7
Dependent Claim
22 words
An electrical alarm system according to claim 3 wherein said biasing circuit includes a capacitor connected in shunt relationship to said diode.
Claim 8
Dependent Claim
17 words
An electrical alarm system according to claim 3 wherein said voltage rectifier is connected across said diode.
Claim 9
Dependent Claim
21 words
An electrical alarm system according to claim 1 having a voltage limiting device connected in shunt relationship with said switching circuit.
Claim 10
Dependent Claim
20 words
An electrical alarm system according to claim 1 wherein said switching circuit includes impedance means forming a high input impedance.
Claim 11
Dependent Claim
20 words
An electrical alarm system according to claim 7 wherein said impedance means includes selectively adjustable impedance means for sensitively adjustment.
Claim 12
Dependent Claim
35 words
An electrical alarm system according to claim 1 wherein said alarm apparatus includes a visual device and an aural device, and switch means connected in circuit with said aural device to selectively prevent energization thereof.
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) | 1977-04-01 | 1977-10-01 | 1978-04-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-04-01 | 1981-10-01 | 1982-04-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-04-01 | 1985-10-01 | 1986-04-02 | $7700.00 | Window Closed / Lapsed |