Patent Application
20140230553
The present invention relates to the detection of movement of a cable containing conductive elements.
The present invention as described in more detail hereinafter operates by monitoring and analyzing the perturbation of an electric potential difference between two separate conductors in a cable. This detection of movement can be used in many fields but is particularly directed to a method which allows the detection of an intrusion event for purposes of securing the cable against unauthorized tampering.
Gigabit Ethernet copper cables are frequently deployed to provide high-speed networks within buildings. Copper based cables, while bandwidth and distance limited as compared to fiber optic cables, are electrically compatible with the Ethernet ports on most computers. As a result, even when fiber optic cable are used as the backbone of the network, the choice is often made to switch to copper cables for the last few hundred feet to the desk.
To secure the fiber optic portion of these high-speed networks, Fiber Optic Intrusion Detection Systems (FOIDS) have been introduced that turns fibers inside of the cables into “sensors” that monitor the physical security of the cable or cables. Thus, once employed, the FOIDS is constantly looking for any potential tampering or attempts to access the fibers inside of the cable or cables.
That is the detection of movement of fiber optic cables has been carried out by sending optical signals into the fiber for transmission therealong, by extracting from the fiber light signals caused by the transmission and by analyzing those signals to obtain information indicative of changes in the signals caused by the movement.
A product for this purpose is sold by the present Assignees under the trademarks Interceptor and Vanguard, details of which are available from a number of prior issued patents by the Assignees including U.S. Pat. No. 7,333,681 (Murphy) issued Feb. 19, 2008 which describes a system for securing multimode fibers and U.S. Pat. No. 7,142,737 (Murphy) issued Nov. 28, 2006 which describes a system for securing single mode fibers. Reference also is made to the following patents:
U.S. Pat. No. 8,233,755 Jul. 31, 2012
U.S. Pat. No. 8,094,977 Jan. 10, 2012
U.S. Pat. No. 7,693,359 Apr. 6, 2010
U.S. Pat. No. 7,706,641 Apr. 27, 2010
U.S. Pat. No. 7,634,387 Dec. 15, 2009
U.S. Pat. No. 7,403,675 Jul. 22, 2008
U.S. Pat. No. 7,376,293 May 20, 2008
U.S. Pat. No. 7,206,469 Apr. 17, 2007
U.S. Pat. No. 7,120,324 Oct. 10, 2006
This arrangement has provided a signal analysis system which is very effective at analyzing optical signals from the optical fibers to detect intrusion in the optical fibers; but up to now no system has been available for detecting intrusion into conductive cables.
As the fiber optic IDS security ends at the optical cable termination, the remaining conductive cable run to the desk, typically copper, is left unprotected and subject to potential tapping.
It is well known, by those skilled in the technology, that copper data pairs are easily tapped and the data stream monitored. One relatively simple non-interruptive tapping method involves placing a probe type coupler next the pair to be tapped. A small fraction of the data stream is picked up electrically from the pair, which is then amplified and monitored.
Other types of cable intrusion detection methods have been described in patent publications. These include:
U.S. Pat. No. 2,787,784, Meryman issued Apr. 2, 1957 Triboelectric Detecting System, describes a method of using a “noisy” cable to detect, amplify and alarm mechanical disturbances using a physically deformable triboelectric generating cable. The method required that certain insulated conductors within the cable are designed such that the insulation is applied loosely allowing mechanical movement between the conductor and the insulation which results in the triboelectric effect.
U.S. Pat. No. 4,374,299, Kincaid issued Feb. 15, 1983 Triboelectric Transducer Cable, describes a cable system whereby certain conductors and the surrounding loosely applied insulation are further optimized to enhance the triboelectric effect.
U.S. Pat. No. 5,446,446 Harman issued Aug. 29, 1995 Differential, multiple cell reflex cable intrusion detection system and method, discloses a type of coaxial cable intrusion detection system which includes a form of sense wire loosely through the dielectric. Movement, of the transducer cable results in movement of the sense wire relative to the outer conductor, causing corresponding changes in characteristic impedance of the sense wire which causes coupling between a carrier signal traveling the coax to couple to the sense wire. A receiver detects the sense wire signal and reports it as an intrusion. This method requires a coax cable configuration and a sense wire within the dielectric insulation.
Security system transmission line U.S. Pat. No. 4,710,753 Rich, et al issued Dec. 12, 1987 relates to a leaky cable intrusion detection system comprising a pair of spaced, parallel, buried, leaky coaxial cables. A radio frequency signal is applied to one of the cables, whereby an electromagnetic field outside said one cable is established, and a radio frequency signal from the field penetrates and is received from the other of the cables whereby disturbances in said field can be detected. This method involves two parallel RF transmission fines to detect intrusion into the space between them.
All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.
It is one object of the present invention to provide an arrangement for detecting movement of an element having longitudinal conductive elements.
According to the invention there is provided a method for monitoring movement of an element comprising:
providing a pair of conductive elements each extending along an extent of the element to be monitored
applying a DC potential difference between the conductive elements;
arranging the conductive elements with an intervening material therebetween such that the movement causes a change in capacitive coupling between the conductive elements so as to generate a changing voltage therebetween;
and detecting and monitoring the changing voltage for perturbations caused by the movement of the element.
In one embodiment the intervening material is a continuous dielectric material separating the two conductive elements.
In another different embodiment the intervening material separating the two conductive elements is not a continuous dielectric ut has varying capacitance along its length. The intervening material separating the two conductive elements can includes dissimilar materials such as air spaces across its thickness.
In one embodiment the element comprises a cable for monitoring movement of the cable. In this case both conductive elements can be located inside an outer cover of the cable. In this case the cable can form one of a plurality of cables contained inside an outer jacket and both conductive elements are inside the outer jacket. The conductive elements can however be placed in the interstices between the cables.
In another embodiment, the cable forms one of a plurality of associated cables and one of the pair of conductive elements is located within in one cable and one in another.
Typically the changing voltage forms a variable signal which is applied to an amplifier where the amplifier provides adequate gain while suppressing common mode noise on both conductive elements.
In this case preferably the DC potential difference is separated from the amplifier by a capacitor allowing the changing voltage to pass through the capacitor.
In some embodiments, the conductive elements form a conductor pair for transmitting data such as a balanced pair or a coax cable.
The monitoring of the movement provided by this invention can be used for many end uses. In a particularly preferred arrangement, the movement is monitored to detect movement indicative of an unauthorized intrusion. In this case typically the movement is monitored for intrusion signature patterns and an alarm signal is transmitted when an intrusion is suspected.
In order to process the varying voltage the monitoring system preferably acts by filtering a signal generated from the changing voltage by initiating a learning period to learn the environmental background disturbances over a period of time and then applying filtering algorithms to eliminate or reduce the background disturbances. The system may also filter a signal generated from the changing voltage by applying filtering algorithms to identify signals which are then correlated to the signature of an attempted intrusion while ignoring normal background mechanical disturbances.
Where used in communication systems, where dedicated conductive elements are not available, each conductive element can comprises a communication pair of wires of the system. In this case each of the pairs is at a common potential so that the potential difference is applied between both wires of one pair and both wires of the other pair.
In another option, there is provided a remote transfer cable connected at one end to the conductive elements and at the other end to control system for supplying the potential difference and for receiving the varying voltage for monitoring.
In another option the method includes monitoring a multitude of elements simultaneously wherein each element has a respective pair of conductive elements which are connected in parallel for common monitoring.
As another possible end use different from communication systems, the element forms a vibration sensor such as used for seismographic reporting or for monitoring of structural resonances.
The embodiment described herein discloses a novel and simpler method of metallic conductor cable intrusion detection. That does not require special sensing wires, transmission lines or loosely insulated conductors. In particular one embodiment described herein discloses employs standard insulated conductors designed for data and voice communication that are not suitable in the prior are detection schemes and are designed to minimize triboelectric effect.
One embodiment of the invention will now be described in conjunction with the accompanying drawings in which:
In the drawings like characters of reference indicate corresponding parts in the different figures.
Fundamental to the present invention is the application of an electric field between two parallel conductors that traverse the length of the cable and by monitoring changes in the voltage between the conductors as a result of the change in capacitance caused by movement in the cable. The voltage, charge and capacitance between the two conductors are related by:
V=Q/C
where:
V is the applied voltage between the conductors
Q is the charge
C is the capacitance between the conductors
As the charge is essentially constant with the applied voltage and the change in capacitance as a result of movement of the cable is quite small, the change in voltage across the conductors can be approximated by:
V=□C V/C
where:
V is the change in voltage between the two conductors and
C is the change in capacitance between the two conductors caused by movement of the cable
Referring to
The voltage change, which is a varying electrical signal proportional to the mechanical disturbance of the cable, is then coupled to the input of instrument amplifiers 9 through the coupling capacitors 7, 8. The instrument amplifier 9 provides adequate gain while suppressing common mode noise. The resultant amplified signal is then fed to a filter stage 10 where unwanted noise and power line influences are further attenuated. The filtered signal is then feed to a level shift and voltage-to-current stage 11 Which conditions the analog signal and forwards it to the input of an analog to digital convertor (ADC) 12. The output of the ADC stage 12 is passed to the input of a computer processor 13. The computer based processor analyzes the disturbance signal for intrusion signature patterns and sends an alarm signal 14 when an intrusion is suspected.
The signal analysis system including the filters can be of the type used by the present Assignees in the above mentioned optical system and disclosed in one or more of the above patents. Once the signal from the sensing system is converted to a varying electrical signal, its processing to cancel unwanted noise and to extract a meaningful response is common between the conductive cables herein and the optical fibers used in the above documents.
In
It has been found that the change in capacitance is sufficient to generate a change in the voltage which can be measured and the resultant signal can be analyzed to produce meaningful data about movement of the conductors at points along their length. In particular, the data can be analyzed to provide information on movement of the cable indicative of an attempt by an unauthorized person to gain access to the cable and the data in the cable.
In telecommunications systems, the two conductors are typically a balanced pair and are referred to as “tip” and “ring” conductors
In the second embodiment of
In some instances, the cable to be monitored for intrusion is remote from the monitoring system and it may be necessary to extend the monitoring circuit over a conductor pair where monitoring is not needed or not wanted. This can be accomplished as illustrated in
The remote cable 26 to be monitored includes a pair of conductors 27 that is connected to a remote voltage supply 30, 31 through a coupling circuit 28, 29.
These connections energize the monitoring conductors to a voltage of 2V. Capacitors 32, 33 couple the varying component of the monitoring signal to the conductor pair 34, 34A leading to the monitoring system 36 over the connecting cable 35. As the coupling capacitors 32, 33 allow the monitored signal to pass over the conductor pair 34 while blocking the DC energizing current, the conductor pair 34, 34A leading to the monitoring system 36 is not monitored for intrusion. The remote voltage supply 30, 31 could also be provided by a second pair in the connecting cable 35 and supplied from the monitoring system 36.
The above descriptions detail how a cable can be monitored using a conductor pair contained within the cable. In another application, it may be desirable to monitor cables from an external location for any attempted intrusion. This can be done by locating a monitored cable in close proximity to the cable(s) to be monitored. Referring therefore to
In a fifth embodiment, the monitoring conductors may form components of a coaxial pair.
In a sixth embodiment, the intrusion monitoring system can be configured to monitor a multitude of cables simultaneously. As shown schematically in
In some instances, the multitude of cables to be monitored for intrusion will be remote from the monitoring system and it may be necessary to extend the monitoring circuit over a conductor pair where monitoring is not needed or not wanted. This can be accomplished as illustrated schematically in
Additional Information:
This technique can be used as a room/building/campus wide vibration sensor for uses such as local or distributed seismographic reporting.
The seismographic sensor can communicate to a centralized location for data collection and analysis.
This technology can be used for eavesdropping and surveillance within the room/building/campus.
This technique can be used as a room/building/campus as well as infrastructure such as bridge wide vibration sensor for monitoring of structural resonances, alone or concurrent with network distribution.
Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.
