Differential delay intrusion detection sensory system

Details Differential delay intrusion detection sensory system Differential delay intrusion detection sensory system

1991-01-31

1992-09-15

Ng, Jin F.

Communications: electrical

Condition responsive indicating system

Specific condition

324658, 331 65, 340539, 340658, G08B 1326

Patent

active

051481499

ABSTRACT:
An electromagnetic intrusion sensor including a sensing element, a first phase shifter circuit for phase shifting an input or oscillation signal in accordance with a capacitance of the sensing element, a second phase shifter circuit for outputting a reference signal having a fixed delay relative to the input or oscillation signal, a phase detector circuit for providing a detector signal having a duty cycle representing the phase differential between the outputs of the first and second phase shifter circuits, and an oscillator circuit for outputting a signal having a frequency which changes according to the duty cycle of the detector signal.

REFERENCES:
patent: 3516063 (1970-06-01), Arkin et al.
patent: 3683351 (1972-08-01), Wilcox
patent: 3697971 (1972-10-01), Domin et al.
patent: 3973208 (1976-08-01), Diamond
patent: 4035798 (1977-07-01), Hackett
patent: 4382291 (1983-05-01), Nakauchi
patent: 4392125 (1983-07-01), Iwata
Boylestad et al., "Electronic Devices and Circuit Theory", 3rd ed., 1982, pp. 57-59.
Allied Security Device Inc. Brochure-ASD-100 Security System, copyrighted 1989.

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