초록 ▼

A single wire antenna placed in proximity to an area to be protected senses the presence of electromagnetic fields including the normal ambient field and modulation thereof resulting from the presence of a moving intruder. The antenna signals are demodulated and filtered to provide the input to circ

A single wire antenna placed in proximity to an area to be protected senses the presence of electromagnetic fields including the normal ambient field and modulation thereof resulting from the presence of a moving intruder. The antenna signals are demodulated and filtered to provide the input to circuitry for inspecting these signals and producing a signal based upon differentiation between normal transient signals and random modulation signals associated with the movement of an intruder. Digital counter circuitry provides the differentiation and various time-out features can be incorporated to control the generation and/or transmission of alarm signals. The system includes various elements to permit easy testing of system operations by the user.

대표청구항 ▼

Apparatus for reliably sensing the presence of a range of modulation signals imposed upon ambient electromagnetic waves within an area requiring surveillance wherein the modulation signals result from movement of an intruder within the area comprising: antenna means for generating an output in respo

Apparatus for reliably sensing the presence of a range of modulation signals imposed upon ambient electromagnetic waves within an area requiring surveillance wherein the modulation signals result from movement of an intruder within the area comprising: antenna means for generating an output in response to the presence of said ambient electromagnetic waves including modulation thereof within the surveillance area, means responsive to the output of said antenna means for demodulating and producing an output therefrom, filter means responsive to said demodulation means output for passing to an output of said filter means signals including only demodulated signals within the intruder originated range, differentiating means responsive to said filter means output for generating an output reflecting the presence of signals originating from randum modulation of the ambient electromagnetic waves, and means responsive to said differentiating means output for establishing an alarm.