Patent US3792455A successfully refreshed from Google Patents.
US3792455A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Security alarm system with frequency sweeping
Assignee: Individual
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Filing: 1972-09-15
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Granted: 1974-02-12
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Expires: 1992-09-15
Abstract
Abstract A system for providing an alarm upon detection of an alarm condition such as intrusion, fire, etc., having a number of sensors which each produce and transmit an rf signal modulated by an identification frequency audio signal unique to the protected facility and a combination of audio frequency signals defining the sensor function and a central alarm control which receives the rf signal and communicates via telephone lines with a central station. In order to eliminate the need for precisely tuning the rf frequency at each sensor and maintaining the rf frequency constant, the alarm control includes a unijunction oscillator circuit which varies a local oscillator connected to a mixer circuit, which forms part of a superhetrodyne receiver, between preset limits to sweep continuously. When an identification frequency signal of sufficient amplitude is detected, an electronic switch is operated to disable the unijunction oscillator and lock the system at the rf frequency onto which the detected identification frequency is modulated.
Inventors
- 👤 D Phillips
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 15:52
CPC Classifications
G; G08; G08B; G08B25/00; G08B25/01; G08B25/10
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
164 words
Apparatus for receiving and decoding a modulated radio frequency signal comprising: a superhetrodyne receiver with a mixing stage for receiving said radio frequency signal, a local oscillator connected to said mixing stage for causing said mixing stage to produce an intermediate frequency signal from said radio frequency signal and the output from said local oscillator, and means connected to said mixing stage for demodulating said intermediate frequency signal, filter means connected to the output of said demodulating means for providing a given output upon detection of a signal at an identification frequency, sweep means including an oscillator connected to said local oscillator for normally varying the frequency of said output of said local oscillator over a preset range, and elecTronic switch means connected to said filter means and to said sweep means for disabling said oscillator of said sweep means when said filter means provides said given output so as to lock in on the radio frequency of the ratio frequency signal being received.
Claim 2
Dependent Claim
164 words
Apparatus for receiving and decoding a modulated radio frequency signal comprising: a superhetrodyne receiver with a mixing stage for receiving said radio frequency signal, a local oscillator connected to said mixing stage for causing said mixing stage to produce an intermediate frequency signal from said radio frequency signal and the output from said local oscillator, and means connected to said mixing stage for demodulating said intermediate frequency signal, filter means connected to the output of said demodulating means for providing a given output upon detection of a signal at an identification frequency, sweep means including an oscillator connected to said local oscillator for normally varying the frequency of said output of said local oscillator over a preset range, and elecTronic switch means connected to said filter means and to said sweep means for disabling said oscillator of said sweep means when said filter means provides said given output so as to lock in on the radio frequency of the ratio frequency signal being received.
Claim 3
Dependent Claim
126 words
Apparatus as in claim 1 wherein said filter means includes an identification frequency filter, first means connected to the input to said filter for producing a first bucking D.C. voltage having an amplitude proportional to the average of the input signal, a second means connected to the output of said filter for producing a second D.C. signal having an amplitude proportional to the average of the output of said filter means connected to said first and second means for summing said first and second signals, and means connected to said summing means and to said switch means for producing a trigger signal to cause said switch means to disable said switch means when the amplitude of the output of said summing means reaches a predetermined level.
Claim 4
Dependent Claim
29 words
Apparatus as in claim 2 wherein said switching means includes first and second transistors and said sweep means includes a unijunction oscillator connected to said first and second transistors.
Claim 5
Independent Claim
151 words
A system for providing an alarm indication upon detection of an alarm condition comprising: a plurality of sensors for each detecting an alarm condition and each producing and transmitting upon detection thereof at least a first electrical signal at an rf frequency which varies from a nominal rf frequency within predetermined limits, said rf frequency modulated by an identification frequency, and central control means for receiving said first signals from said sensors, detecting said identification frequency and providing said alarm indication upon detection of said identification frequency including means for sweeping to locate an rf frequency signal within said predetermined limits including a variable output oscillator, means for demodulating a received rf signal, means for detecting an identification frequency and means for disabling said sweeping means upon detection of said identification frequency to lock on a received rf signal including an electronic switch connected to said oscillator of said switch means.
Claim 6
Independent Claim
151 words
A system for providing an alarm indication upon detection of an alarm condition comprising: a plurality of sensors for each detecting an alarm condition and each producing and transmitting upon detection thereof at least a first electrical signal at an rf frequency which varies from a nominal rf frequency within predetermined limits, said rf frequency modulated by an identification frequency, and central control means for receiving said first signals from said sensors, detecting said identification frequency and providing said alarm indication upon detection of said identification frequency including means for sweeping to locate an rf frequency signal within said predetermined limits including a variable output oscillator, means for demodulating a received rf signal, means for detecting an identification frequency and means for disabling said sweeping means upon detection of said identification frequency to lock on a received rf signal including an electronic switch connected to said oscillator of said switch means.
Claim 7
Dependent Claim
62 words
A system as in claim 4 wherein said sweeping means includes a mixing stage for receiving said modulated rf frequency signal, a local oscillator connected to said mixing stage for causing said mixing stage to produce an intermediate frequency signal from said ratio frequency signal and the output from said local oscillator and wherein said demodulating means demodulates said intermediate frequency signal.
Claim 8
Dependent Claim
22 words
A system as in claim 4 wherein said oscillator of said sweeping means includes a unijunction oscillator connected to said electronic switch.
Claim 9
Dependent Claim
36 words
A system as in claim 4 wherein said detecting means includes filter means connected to the output of said demodulating means for providing a given output signal upon detection of a signal at an identification frequency.
Claim 10
Dependent Claim
127 words
A system as in claim 7 wherein said filter means includes an identification frequency filter, first means connected to the input to said filter for producing a first bucking D.C. voltage having an amplitude proportional to the average of the input signal, a second means connected to the output of said filter for producing a second D.C. signal having an amplitude proportional to the average of the output of said filter, means connected to said first and second means for summing said first and second signals, and means connected to said summing means and to said switch means for producing a trigger signal to cause said switch means to disable said switch means when the amplitude of the output of said summing means reaches a predetermined level.
Claim 11
Dependent Claim
134 words
A system as in claim 4 wherein each of said sensors further includes means for producing a combination of audio frequency signals denoting the function of that sensor, and means for modulating a rf frequency signal by saiD audio frequency signals and said first signal at said identification frequency and transmitting said rf signal, wherein said central control means further includes means for receiving and amplifying the transmitted rf signal, wherein said sweeping means includes oscillator means for producing an output at a variable frequency, means for varying the output frequency of said oscillator means and means connected to said receiving and amplifying means and to said oscillator means for mixing the amplified rf signal with said variable frequency signal, and wherein said disabling means includes switch means operable to disable said varying means.
Claim 12
Dependent Claim
56 words
A system as in claim 9 wherein said central control means further includes an intermediate frequency amplifier connected to said mixing means for amplifying the mixed signal, a limiter circuit connected to said intermediate frequency amplifier a detector circuit connected to said limiter circuit and an audio bandpass amplifier circuit connected to said pulse width detector.
Claim 13
Dependent Claim
132 words
A system as in claim 10 further including a filter tuned to said identification frequency connected to said audio bandpass amplifier circuit, means connected to the output of said tuned filter for producing a D.C. signal with an amplitude proportional to the average amplitude of the output of said tuned filter, bucking means connected to the input of said tuned filter for producing a further D.C. bucking signal with an amplitude proportional to the amplitude of the input to said tuned circuit, means for summing said D.C. signal and said further D.C. signal to cancel some noise, and a Schmidt trigger circuit connected between said switch means and said summing means for causing said switching means to disable said sweep means when the output of said summing means exceeds a predetermined level.
Claim 14
Dependent Claim
112 words
A system as in claim 9 wherein said varying means includes a unijunction oscillator with a capacitor which is alternately charged and discharged to provide a ramp output and said switch means includes first and second transistors connected to said comparing means so as to shift output conditions when said given signal is produced to maintain the output of said unijunction oscillator at its level when shifting occurs and wherein said oscillator means includes an oscillator circuit connected to said output of said unijunction oscillator for receiving said ramp output and producing a signal at a frequency which varies as a function of the level of the output of said unijunction oscillator.
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) | 1977-02-11 | 1977-08-13 | 1978-02-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-11 | 1981-08-13 | 1982-02-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-11 | 1985-08-13 | 1986-02-12 | $7700.00 | Window Closed / Lapsed |