EP0041781A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Intrusion detection and alarm system
Assignee: Gentex Corp
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Filing: 1981-05-14
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Granted: —
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Expires: 2001-05-14
Abstract
Abstract A self-contained intrusion detection and alarm system for doors and other closures comprising a loop antenna (12), an rf oscillator circuit (14) electrically connected to said antenna, a DC power source (E) electrically connected to said oscillator circuit (14), a detection and processing circuit (16), a memory and inverter circuit (20) connected to said detection and processing circuit, an audio oscillator (22) connected to said memory and inverter circuit, and an audio transducer (28) connected to said audio oscillator. The construction is such that the total electromagnetic field produced at any point a distance of 47,850 / F(kHz) metres (equivalent to λ/2π) from said antenna does not exceed 15 microvolts per metre.
Inventors
- 👤 William E. Wagner
- 👤 Ivan Zachev
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 18:49
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/26
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
71 words
A detection and alarm system comprising an antenna (12), an rf oscillator circuit (14) electrically connected to said antenna, a DC power source (E) electrically connected to said oscillator circuit (14), a detection and processing circuit (16), a memory and inverter circuit (20) connected to said detection and processing circuit, an audio oscillator (22) connected to said memory and inverter circuit, and an audio transducer (28) connected to said audio oscillator.
Claim 2
Dependent Claim
71 words
A detection and alarm system comprising an antenna (12), an rf oscillator circuit (14) electrically connected to said antenna, a DC power source (E) electrically connected to said oscillator circuit (14), a detection and processing circuit (16), a memory and inverter circuit (20) connected to said detection and processing circuit, an audio oscillator (22) connected to said memory and inverter circuit, and an audio transducer (28) connected to said audio oscillator.
Claim 3
Dependent Claim
41 words
A system as claimed in claim 1, characterized in that the total electromagnetic field produced at any point a distance of 47,850 metres (equivalent to A ) F (kHz) 2 π from said antenna does not exceed 15 microvolts per metre.
Claim 4
Dependent Claim
27 words
A system as claimed in claim 1 or 2, characterized in that the detection and processing circuit (16) includes an operational amplifier (IC1) and a comparator (IC2).
Claim 5
Dependent Claim
28 words
A system as claimed in claim 1, 2 or 3, characterized in that said rf oscillator circuit (14) includes part of a tank circuit (12, L, C4, C5)..
Claim 6
Independent Claim
21 words
A system as claimed in any preceding claim, characterized in that said antenna (12) is in the form of a loop.
Claim 7
Independent Claim
20 words
A system as claimed in any preceding claim, characterized in that said rf oscillator circuit (14) includes a transistor (Ql).
Claim 8
Independent Claim
26 words
A system as claimed in any preceding claim, characterized in that said antenna (12) is connected to said rf oscillator circuit (14) through a resistor (Rl).
Claim 9
Independent Claim
31 words
A system as claimed in any preceding claim, characterized in that said rf oscillator produces a sinusoidal wave form with a frequency between 2 megahertz and 3 megahertz, preferably 2.5 megahertz.
Claim 10
Independent Claim
24 words
A system as claimed in any preceding claim, characterized in that said detection and processing circuit includes first and second integrated circuits (IC1, IC2).
Claim 11
Dependent Claim
24 words
1 0 . A system as claimed in claim 9, characterized in that said memory and inverter circuit includes a third integrated circuit (IC3).
Claim 12
Dependent Claim
19 words
A system as claimed in claim 10, characterized in that said audio oscillator includes a fourth integrated circuit (lC4).
Claim 13
Independent Claim
32 words
A system as claimed in any preceding claim, characterized by a battery status indicator circuit (24) electrically connected to said memory and inverter circuit (20) and to said source (E) of'DC power.
Claim 14
Dependent Claim
20 words
A system as claimed in claim 12, characterized in that said indicator circuit (24) includes a light emitting diode (D3).
Claim 15
Dependent Claim
21 words
A system as claimed in claim 12 or 13, characterized in that said indicator circuit (24) includes a zener diode (D2).
Claim 16
Dependent Claim
29 words
A combination as claimed in claim 12, 13 or 14, characterized in that said indicator circuit (24) includes means (210) for reducing the output of the audio transducer (28).
Claim 17
Independent Claim
35 words
A system as claimed in any preceding claim, characterized by means (R14, C12) effective to delay energization of said audio transducer (28) for a predetermined period of time after said system has been electrically energisation.
Claim 18
Independent Claim
35 words
A system as claimed in any preceding claim, characterized by means (R20, C14) effective to delay energization of said audio transducer (28) for a predetermined period of time after a change in antenna-to-ground capacitance occurs.
Claim 19
Independent Claim
30 words
A system as claimed in any preceding claim, characterized by a switch (52) operable to effect energization of said audio transducer (28) immediately after a change in antenna-to-ground capacitance occurs.
Claim 20
Independent Claim
40 words
A system as claimed in any preceding claim, characterized by a decouple circuit (18) effective to reduce noise feedback from said audio oscillator and said audio transducer to the rf oscillator circuit (14) and the detection and processing circuit (16).
Claim 21
Independent Claim
34 words
A system as claimed in any preceding claim, characterized in that said audio transducer (28) has an audio output with a frequency in the range between 2,500 and 3,500 hertz, preferably approximately 3,OOQ hertz.
Claim 22
Dependent Claim
84 words
A detection and alarm system as claimed in claim 1 or 2, characterized in that the antenna (12) is in the form of a loop, the rf oscillator circuit (14) includes a tank circuit (L, C4, C5) electrically connected to said antenna (12), the detection and processing circuit includes an operational amplifier (ICl) and a comparator (IC2), the memory and inverter circuit (20) includes an R S flip-flop connected to said detection and processing circuit, and the audio transducer comprises a piezo horn (28).
References Cited (Backward Citations)
No citation records indexed.
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