Surveillance system and method for use above or below ground with direction and location of crossing indidication

Claim 2

A surveillance system for determining the presence of a body on the surface of soil and in the vicinity of said system, the system comprising spaced first and second electrical conductor lines mounted in the soil, said lines each having a resistive coating thereon to effect a voltage drop through the resistive coating during current flow from said lines through said soil, a third lines disposed between said first and second lines, said third line having a layer of dielectric material thereon, means energizing said first and second lines with alternating current, said third line being positioned and of a potential so as to receive electrical signals from said first and second lines respectively, and means for sensing a change in the signal received by said third line to denote the presence of a body that has moved into a proximal relation with said first and third lines or into a proximal relation with said second and third lines.

Claim 3

A surveillance system in accordance with claim 1 in which said energizing means excites said second line with alternating current having a different phase relationship from that with which saId first line is excited, said sensing means being phase sensitive.

Claim 4

A surveillance system in accordance with claim 2 in which there is a 180* phase relationship between said exitation currents.

Claim 5

A surveillance system in accordance with claim 3 in which said sensing means includes an amplifier and a phase-sensitive demodulator.

Claim 6

A surveillance system in accordance with claim 4 including signal means connected to the output of said demodulator for indicating the direction of body movement.

Claim 7

A surveillance system in accordance with claim 5 in which said signal means includes a pair of differently colored lights, the sequential illumination of said lights indicating the direction of body movement.

Claim 8

A surveillance system for determining the presence of a body on the soil surface in the vicinity of said system, the system comprising first, second and third lines buried below the soil surface and subjected to differing soil electrical conductivity, said third line being intermediate said first and second lines, means energizing said first line with alternating current having one electrical characteristic, means energizing said second line with alternating current having a different electrical characteristic, said first and second lines having resistive coatings thereon resulting in voltage drops across the resistive coatings commensurate with soil conductivity, and means associated with said third line for discriminating between said characteristics.

Claim 9

A surveillance system for determining the presence of a body on the soil surface in the vicinity of said system, the system comprising first, second and third lines buried below the soil surface and subjected to differing soil electrical conductivity, said third line being intermediate said first and second lines, means energizing said first line with alternating current having one electrical characteristic, means energizing said second line with alternating current having a different electrical characteristic, said first and second lines having resistive coatings thereon resulting in voltage drops across the resistive coatings commensurate with soil conductivity, and means associated with said third line for discriminating between said characteristics.

Claim 10

A surveillance system in accordance with claim 7 in which said last-mentioned means provides an output signal indicative of said characteristics.

Claim 11

A surveillance system in accordance with claim 7 in which said characteristics provide a different phase relationship.

Claim 12

A surveillance system in accordance with claim 7 in which said characteristics provide a different frequency relationship.

Claim 13

A surveillance system in accordance with claim 10 wherein said lines define the perimeter of an area under surveillance including a plurality of electronic signal converters in said first line for altering the frequency of said alternating current at spaced stations along said first line, said spaced stations defining known locations along the perimeter of said area.

Claim 14

A surveillance system in accordanc with claim 11 including a plurality of electronic signal converters in said second line for altering the frequency of said alternating current at spaced stations, both the spacing of said last-mentioned stations and the frequency thereof corresponding to that of said first-mentioned stations.

Claim 15

A surveillance system in accordance with claim 12 in which the particular frequency at each station in said second line is out-of phase with the frequency for the corresponding station in said first line.

Claim 16

A surveillance system in accordance with claim 13 in which said discriminating means is both frequency and phase sensitive.

Claim 17

A surveillance system embedded below the surface of the soil for determining the presence of a body on the soil surface in the vicinity of said system, said system comprising electrical lines extending below the soil at the perimeter of an area under surveillance by said system and through soil having at times differing electrical conductivity, said system comprising at least one electrical field generating line means having a resistive coating thereon which causes a voltage drop through said coating as a function of soil conductivity, and sensing line means spaced from said field generating line means and in position to receive electrical signals which are a function of the electrical potential difference between said field generating line means and said sensing line means, whereby the presence of a body on the soil surface adjacent to said generating line means and said sensing line menas influences the signal received by said sensing line means from said generating line means.

Claim 18

A surveillance system embedded below the surface of the soil for determining the presence of a body on the soil surface in the vicinity of said system, said system comprising electrical lines extending below the soil at the perimeter of an area under surveillance by said system and through soil having at times differing electrical conductivity, said system comprising at least one electrical field generating line means having a resistive coating thereon which causes a voltage drop through said coating as a function of soil conductivity, and sensing line means spaced from said field generating line means and in position to receive electrical signals which are a function of the electrical potential difference between said field generating line means and said sensing line means, whereby the presence of a body on the soil surface adjacent to said generating line means and said sensing line menas influences the signal received by said sensing line means from said generating line means.

Claim 19

A surveillance system in accordance with claim 15 wherein said resistive coating is selected to provide a current limiting effect on current flow from said field generating line means through soil of differing conductivity.