Network security system for detecting removal of electronic equipment

Claim 2

A security system for detecting disconnection of electronic equipment from a network, said security system comprising: current loop means including separate current loops associated with different pieces of monitored equipment, each of said current loops employing a pair of data communication lines which connect one of the associated pieces of equipment to the network and which are coupled to existing internal circuitry within the associated piece of monitored equipment, and wherein respective pairs of data communication lines are associated with different ones of the associated pieces of equipment; source means for supplying a low DC current signal to each of said current loops; and detector means for monitoring the current signal through each of said current loops and detecting a change in said current signal through one of said current loops which represents disconnection of said associated piece of equipment from the network.

Claim 3

The security system as defined in claim 1 wherein said electronic equipment comprises computer workstations each connected to a network file server and located remote from the network file server.

Claim 4

The security system as defined in claim 1 wherein each of said current loops includes existing pairs of data communication lines used by said network for communicating data between the associated pieces of equipment and a network file server.

Claim 5

The security system as defined in claim 1 wherein said network includes an Ethernet® network and said respective pairs of data communication lines include existing 10BaseT wiring connecting the different ones of the associated pieces of equipment to said network.

Claim 6

The security system as defined in claim 1 wherein said existing internal circuitry includes an isolation transformer having a first winding coupled between said pair of data communication lines so as to allow said current signal to flow therethrough when the associated piece of equipment is connected to the network.

Claim 7

The security system as defined in claim 1 wherein said system further comprises high frequency filter means coupled to each of said current loops for providing isolation to each of said current loops.

Claim 8

The security system as defined in claim 1 further comprising DC blocking capacitors coupled to each of said current loops for preventing said current signal through one of said current loops from interfering with other of said current loops.

Claim 9

The security system as defined in claim 1 further comprising alarm indicator means responsive to said current detection for providing an alarm signal indicative of a disconnected piece of said equipment when said change in the current signal through one of said current loops is detected.

Claim 10

A security system for detecting unauthorized disconnection of electronic equipment that is connected to a network communication link having existing pairs of data communication lines interconnecting said electronic equipment to a network, said system comprising: current loop means including separate current loops associated with different pieces of protected equipment and internally coupled to the associated pieces of protected equipment, each of said current loops using said existing pair of data communication lines which are coupled together via existing internal circuitry within said associated equipment to form a complete circuit path therethrough, and wherein respective pairs of data communication lines are associated with different ones of the associated pieces of equipment; source means for supplying a low DC current signal to each of said current loops; sensing means for sensing current flow through each of said current loops and detecting a change in said current flow through one of said current loops which is indicative of disconnection of one of the associated pieces of equipment; and output means for providing an alarm output signal so as to indicate detection of a disconnected one of said pieces of equipment.

Claim 11

A security system for detecting unauthorized disconnection of electronic equipment that is connected to a network communication link having existing pairs of data communication lines interconnecting said electronic equipment to a network, said system comprising: current loop means including separate current loops associated with different pieces of protected equipment and internally coupled to the associated pieces of protected equipment, each of said current loops using said existing pair of data communication lines which are coupled together via existing internal circuitry within said associated equipment to form a complete circuit path therethrough, and wherein respective pairs of data communication lines are associated with different ones of the associated pieces of equipment; source means for supplying a low DC current signal to each of said current loops; sensing means for sensing current flow through each of said current loops and detecting a change in said current flow through one of said current loops which is indicative of disconnection of one of the associated pieces of equipment; and output means for providing an alarm output signal so as to indicate detection of a disconnected one of said pieces of equipment.

Claim 12

The security system as defined in claim 9 wherein each of said pairs of data communication lines are coupled between one of said associated pieces of equipment and a network file server.

Claim 13

The security system as defined in claim 9 wherein said data communication lines are provided via 10BaseT wiring.

Claim 14

The security system as defined in claim 9 wherein said internal circuitry within said associated equipment comprises a first winding of a transformer which is coupled between each of said respective pairs of data communication lines to form a circuit path through each of said pairs of data communication lines.

Claim 15

The security system as defined in claim 9 wherein said DC current signal has a current of less than 1 milliamp.

Claim 18

The method as defined in claim 14 further comprising the step of providing an alarm signal when said disconnection of one of said pieces of equipment is detected.

Claim 19

The method as defined in claim 14 further comprising the step of: selectively tapping into each of said selected pairs of existing data communication lines at a location which is remote from said associated pieces of equipment.

Claim 20

The method as defined in claim 14 wherein said existing data communication lines comprise 10BaseT wiring.

Claim 21

The method as defined in claim 14 wherein each of said pieces of electronic equipment comprises a computer workstation connected to an Ethernet® network.

Claim 22

The method as defined in claim 14 wherein each of said current loops includes existing circuitry within the associated piece of equipment and coupled between the one of said associated pairs of data communication lines to provide a circuit path therebetween.