Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
135 words
In a perimeter intrusion detection apparatus for providing an indication of the presence of a magnetically permeable object, the combination of, an elongated magnetic core member and coil means wound thereabout, said combination of the core member and coil means being positioned relative to the surface of the earth to respond to changes in the earth''s magnetic field, an AC excitation source operatively connected to said coil means for establishing a current flow in said coil means to saturate said core member, said coil means responding to changes in the earth''s magnetic field caused by the presence of a magnetically permeable object by developing AC output signals, and first circuit means operatively connected to said coil means for responding to the content of said AC output signals indicative of the strength of the magnetic field.
Claim 2
Dependent Claim
135 words
In a perimeter intrusion detection apparatus for providing an indication of the presence of a magnetically permeable object, the combination of, an elongated magnetic core member and coil means wound thereabout, said combination of the core member and coil means being positioned relative to the surface of the earth to respond to changes in the earth''s magnetic field, an AC excitation source operatively connected to said coil means for establishing a current flow in said coil means to saturate said core member, said coil means responding to changes in the earth''s magnetic field caused by the presence of a magnetically permeable object by developing AC output signals, and first circuit means operatively connected to said coil means for responding to the content of said AC output signals indicative of the strength of the magnetic field.
Claim 3
Dependent Claim
89 words
In a perimeter intrusion detection apparatus as claimed in claim 1, wherein said coil means consists of a primary helical winding wound about said core member and a secondary helical winding wound about said core member, said AC excitation source operatively connected to said primary winding and said circuit means operatively connected to said secondary winding, said secondary winding comprised of a plurality of intervals, said circuit means monitoring the AC signals developed by the respective intervals to determine the interval or intervals closest to the magnetically permeable objects.
Claim 4
Dependent Claim
50 words
In a perimeter intrusion detection apparatus as claimed in claim 2 wherein said coil means includes a third helical winding wouNd about said core member and second circuit means operatively connected thereto to apply current of a polarity and magnitude sufficient to cancel the effect of the earth''s magnetic field.
Claim 5
Dependent Claim
60 words
In a perimeter intrusion apparatus as claimed in claim 1 wherein said first circuit means includes a second harmonic detection circuit, the second harmonic content of said AC output signals being a measure of the strength of the DC magnetic field, said first circuit means develping an output signal indicative of the second harmonic content of said AC output signals.
Claim 6
Dependent Claim
74 words
In a perimeter intrusion detection apparatus as claimed in claim 4 further including third circuit means operatively connected to said first circuit means for comparing the output signal of said first circuit means to a reference signal indicative of the strength of a magnetic field representative of a predetermined magnetically permeable object, said third circuit means generating an output signal when the output signal of said first circuit means corresponds to said reference signal.