US3839709A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Discriminative intruder-detecting system
Assignee: Hitachi Unisia Automotive Ltd
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Filing: 1972-09-18
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Granted: 1974-10-01
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Expires: 1992-09-18
Abstract
Abstract A discriminative intruder-detecting system includes a transceiver unit and a modulator unit both of which are completely separate from and unconnected to each other. The transceiver unit has an oscillator and antenna which cooperate to transmit waves of radio frequency through the space which is to be guarded. The modulator unit has a dipole antenna provided with a pair of feed points to which a low-frequency oscillator is connected for introducing low-frequency components to the dipole antenna, this latter antenna resonating at the frequency of the waves transmitted by the antenna of the transceiver unit. Waves reflected by the dipole antenna back to the antenna of the transceiver unit will thus contain low-frequency components, and the circuitry of the transceiver unit is capable of preventing operation of a warning device when the reflected waves with the low-frequency components are received. Thus, an authorized individual carrying the modulator unit on his person and entering the guarded space will not set off the warning device while an unauthorized individual will reflect waves without low-frequency components back to the antenna of the transceiver unit so as to cause the warning device to operate.
Inventors
- 👤 K Sugiura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 12:08
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2491
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
328 words
In a discriminative intruder-detecting system, a radio transceiver unit adapted to be placed within a space which is to be guarded and to remain stationary in said space, said transceiver unit including a radio-frequency oscillator means for generating an oscillation output of radio frequency and antenna means operatively connected with said oscillator means for transmitting through the space which is to be guarded radio waves at the frequency determined by said oscillator means, warning means for providing a warning signal which indicates the presence of an intruder in said space, electrical circuit means forming part of said transceiver unit and electrically connecting said warning means to said transceiver unit for preventing acutuation of said warning means in response to radio waves reflected from an authorized individual in said space and received by said antenna means, and a modulator unit separate from and having no connection with said transceiver unit, said modulator unit being adapted to be carried on the person of an indiviual who is authorized to enter the guarded space, said modulator unit including a modulating antenna means which resonates at the radio frequency of the wave transmitted by said antenna means of said transceiver unit, and said modulator unit including a means operatively connected to said modulating antenna means for introducing a low frequency component into the wave reflected by said modulating means back to said antenna means of said transceiver unit, so that waves received by the latter anteNna from an authorized individual in said guarded space who carries said modulator unit will include a low-frequency component, and said circuit means which is electrically connected to said warning means including a detecting circuit means for detecting the presence of the waves received from said modulating antenna means with said low-frequency component and switch means for controlling said warning means such that when said waves with said low-frequency component are received by said antenna means of said transceiver unit said warning means will not be actuated.
Claim 2
Dependent Claim
328 words
In a discriminative intruder-detecting system, a radio transceiver unit adapted to be placed within a space which is to be guarded and to remain stationary in said space, said transceiver unit including a radio-frequency oscillator means for generating an oscillation output of radio frequency and antenna means operatively connected with said oscillator means for transmitting through the space which is to be guarded radio waves at the frequency determined by said oscillator means, warning means for providing a warning signal which indicates the presence of an intruder in said space, electrical circuit means forming part of said transceiver unit and electrically connecting said warning means to said transceiver unit for preventing acutuation of said warning means in response to radio waves reflected from an authorized individual in said space and received by said antenna means, and a modulator unit separate from and having no connection with said transceiver unit, said modulator unit being adapted to be carried on the person of an indiviual who is authorized to enter the guarded space, said modulator unit including a modulating antenna means which resonates at the radio frequency of the wave transmitted by said antenna means of said transceiver unit, and said modulator unit including a means operatively connected to said modulating antenna means for introducing a low frequency component into the wave reflected by said modulating means back to said antenna means of said transceiver unit, so that waves received by the latter anteNna from an authorized individual in said guarded space who carries said modulator unit will include a low-frequency component, and said circuit means which is electrically connected to said warning means including a detecting circuit means for detecting the presence of the waves received from said modulating antenna means with said low-frequency component and switch means for controlling said warning means such that when said waves with said low-frequency component are received by said antenna means of said transceiver unit said warning means will not be actuated.
Claim 3
Dependent Claim
122 words
The combination of claim 1 and wherein said modulating antenna means is a half-wave dipole antenna having a pair of feeding points, said means which is operatively connected to said dipole antenna for providing said low-frequency component including a low-frequency oscillator means connected to said points for generating a low-frequency signal across said points, and a directional means connected between said points for electrically disconnecting said dipole antenna intermittently in response to the low-frequency signals from said low-frequency oscillator means, so that a wave transmitted from said antenna of said transceiver unit and reflected by said dipole antenna is modulated with the frequency at which said dipole antenna is intermittently disconnected, to provide the reflected radio wave which contains said low-frequency components.
Claim 4
Dependent Claim
22 words
The combination of claim 2 and wherein said directional means is a semiconductor diode connected between said points of said dipole antenna.
Claim 5
Dependent Claim
27 words
The combination of claim 1 and wherein said circuit means which electrically connects said warning means to said transceiver unit includes a means for eliminating Doppler-frequency signals.
Claim 6
Dependent Claim
66 words
The combination of claim 4 and wherein said means for eliminating said Doppler-frequency signals includes a filter circuit means, and said means for introducing a low-frequency component including a low-frequency oscillator means which is electrically connected with said modulating antenna means and which has an oscillation frequency sufficiently different from the Doppler frequency to permit said filter circuit means to filter one frequency from the other.
Claim 7
Dependent Claim
69 words
The combination of claim 5 and wherein said low-frequency oscillator means of said modulator unit forms said means operatively connected to said modulating antenna means for introducing a low-frequency component into the wave reflected thereby back to said antenna means of said transceiver unit, said modulating antenna means includes a half wave dipole antenna having a pair of feed points to which said low-frequency oscillator means is electrically connected.
Claim 8
Dependent Claim
37 words
The combination of claim 6 and wherein said modulator unit includes a directional means connected between said feed points for electrically disconnecting said dipole antenna intermittently in response to the low-frequency signals from said low-frequency oscillator means.
Claim 9
Dependent Claim
22 words
The combination of claim 7 and wherein said directional means is a semiconductor diode connected between said points of said dipole antenna.
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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) | 1977-09-30 | 1978-04-01 | 1978-10-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-09-30 | 1982-04-01 | 1982-10-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-09-30 | 1986-04-01 | 1986-10-01 | $7700.00 | Window Closed / Lapsed |