Triboelectric, Ranging, or Dual Use Security Sensor Cable and Method of Manufacturing Same

Abstract

The present invention provides an inexpensive security sensor cable, a method for manufacturing of same and an overall security system for using that sensor cable. The sensor cable consists of a central conductor, an air separator, a polyethylene dielectric tube, an outer conductor and an outer protective jacket. The central conductor is loosely centered in the coaxial cable and thus freely movable relative to the dielectric tube. The sensor cable has application either in a passive sensing system or in an active ranging sensing system to determine the location of an intrusion along the cable. For the passive sensing function, when the center conductor moves, it contacts a suitable dielectric material from the triboelectric series, such as polyethylene, which can be processed to produce a charge transfer by triboelectric effect that is measurable as a terminal voltage. In an active system, the central conductor moves within the dielectric in response to a vibration to provide an impedance change that can be sensed. Conventional radio grade cable may be modified in its construction by removing its dielectric thread to manufacture the sensor cable, thus enabling the center conductor to move freely in the air gap within the dielectric tube. An inexpensive method of manufacturing sensor cable is provided as the cable parts are readily available. Such a sensor cable is advantageous in that the passive triboelectric properties of the cable, in response to a disturbance, can provide a larger voltage response over prior art cables.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to drawings, in which:

FIG. 1 is an end view of a conventional cable for computer and communication applications of the prior art;

FIG. 2 is an end view of a sensor cable constructed and manufactured according to a first embodiment of the present invention;

FIG. 3 is an end view of a sensor cable constructed and manufactured according to a second embodiment of the present invention;

FIG. 4 is an end view of a sensor cable constructed and manufactured according to a third embodiment of the present invention;

FIG. 5 is a side view of the sensor cable in FIG. 2;

FIG. 6 is a block diagram of a sensor cable system including a sensor cable of the present invention for both passive and active intrusion detection along the length of the sensor cable; and

FIG. 7 is a computer display image with a graph showing a voltage response to impact along the sensor cable of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be described for the purposes of illustration only in connection with certain embodiments. However, it is to be understood that other objects and advantages of the present invention will be made apparent by the following description of the drawings according to the present invention. While a preferred embodiment is disclosed, this is not intended to be limiting. Rather, the general principles set forth herein are considered to be merely illustrative of the scope of the present invention and it is to be further understood that numerous changes may be made without straying from the scope of the present invention.

For the purposes of this document, the “active ranging” cable system is one where a signal is injected (transmitted) into the cable, and a response signal, either unmodified or modified by an intruder, is sensed by a receiver and analyzed by a processor to determine presence and location (range) of the intrusion, similar to radar. For example, the injected signal to a loosely disposed conductor cable could be a pulse, and the reflected signal from an intruder altering the impedance of the cable is captured at the same cable end and analyzed; e.g., time relative to the input pulse is used to obtain location, signal amplitude or frequency (spectrum) to classify the intruder as a valid target.

Also for the purposes of this document, in a “passive” cable system, there is no signal injected by a transmitter, rather it is created on the sensor cable itself by the disturbance, such as in triboelectric, piezoelectric and electret cables.

The signal is received and analyzed as a generally continuous time response waveform of some amplitude and frequency—there is no timing data relative to an injected signal to provide location. For example with the Intelli-FLEX™ system the sensor cable is constructed with suitable materials having triboelectric properties, to produce a small voltage between inner and outer conductors in response to local cable flexing, from the presence of the intruder.

It is also understood that the classification of “passive, or passive sensing, or passive disturbance sensing” systems includes those cable systems that require some excitation signal applied to the sensing cable to provide the passive sensing signal to analyze. These systems as such do not generate a voltage signal on their own, being for example magnetic or fiber optic cables.

For example with the IntelliFIBER™ system, a signal input is a continuous optical signal applied at one end of the fiber cable. The system receives a signal at the other end of the fiber cable which has its polarization altered by the intruder's presence. The optical output signal is converted to a voltage response very similar to the passive sensed output of the Intelli-FLEX™ sensor. This system does not provide location data, as there is no timing element nor reflection data provided with sensing at the opposite cable end. Accordingly, the present invention may be incorporated into such a system, as a passive sensing system with a converted voltage output relative to the disturbance.

Referring now to FIG. 1, an end view of a conventional cable 1 well known in the art for computer and communication applications, such as the RG 62U cable is illustrated. This prior art cable 1 is constructed to provide a mixed dielectric of a combination of air and several plastic grades. This dielectric combination is termed semi-solid. The center conductor 2 is typically copper clad steel, around which is wound a polyester thread 3 at a prescribed pitch angle. Around this thread 3 is next extruded a further solid polyethylene dielectric tube 4. Following this an outer conductor 5 or shield of copper strands is braided along the dielectric tube 4. This outer conductor 5 may be impregnated with a water blocking material such as a silicone grease or wax to reduce the risk of moisture propagation internally if the cable 1 is damaged. Finally an outer jacket 6 made of material such as PVC or polyethylene is extruded. Hence, the dielectric elements between the center and outer conductor is a combination of the helical air gap 7, the polyester thread 3 and the polyethylene tube 4. The dimensions of each dielectric 3, 4, 7 are selected to provide a particular velocity of propagation of the cable, and a nominal impedance. The combination of the thread 3 and the tube 4 fix the center conductor 2 in place relative to the outer conductor 5.

FIG. 2 illustrates an end view of a sensor cable 10 constructed and manufactured according to an embodiment of the present invention. This sensor cable 10 consists essentially of a conventional threaded cable modified to include as a minimum two dielectric materials, namely a polyethylene dielectric tube 4 which can be of the same inner and outer dimensions as the RG-62 cable for example, and an inner air gap 7 with the center conductor 2 free to move in the space between. The sensor cable 10 can be relatively easily constructed using the same or similar processes of extrusion, braiding and jacketing as the well known communications cable. As the inner thread is not utilized in the cable construction of the sensor cable 10, the center conductor 2 is free to move in the inner air gap 7 within the polyethylene tube 4. The sensor cable 10 also uses the same materials as in the conventional cable, namely inexpensive polyethylene already used in volume for communication cables.

The dielectric material selected may also be foamed polyethylene, for example, or a triboelectric material close in ranking along the series.

For the passive triboelectric sensing function, the center conductor 2 is free to move in response to a vibration, which causes the center conductor to move into contact with a suitable dielectric material, such as polyethylene from the triboelectric series, to provide a charge transfer. In passive operation, experimental tests have shown that the selection of polyethylene enhances the “sensitivity” of the sensor cable of the present invention, i.e. terminal voltage produced between the conductors is higher relative to other conventional materials, such as FEP. Thus, the selection of dielectric material is based on producing a terminal voltage response that provides an acceptable signal to noise ratio.

It is understood that an “acceptable” signal to noise ratio is an order of magnitude (e.g. 10×) or more than the average noise, and that the minimum ratio would likely be a factor of 2.

For the active ranging function, the same conductor moves within the dielectric in response to a vibration, to provide an impedance change that can be sensed by conventional time domain ranging (TDR) processes, or by alternative processing means.

It is understood that the selection of suitable dielectric material is an important factor in enhancing the “sensitivity” of the sensor cable in response to a disturbance. However, the level of “sensitivity” of the sensor cable may be affected by various processes. Experimental tests were performed to test various combinations of dielectric and conductive materials. For example, a 5′ sensor cable sample, constructed based on a modified RG-62 cable and heated to its dielectric softening temperature of approximately 80° C. for at least 24 hours, substantially diminished its sensitivity. However, other tests performed on similar triboelectric (electret) cable samples for example applying high alternating current (AC) voltages did not affect the stability of the cable samples' detection properties.

While FIG. 2 shows a fitted outer conductor 5, it is readily understood by the skilled artisan that this outer conductor 5 may have one surface in contact with an air separator located between the outer jacket 6 and the dielectric tube 4 as an alternative to a loose center conductor within a dielectric. This alternative construction enables the outer conductor 5 to move freely between the outer jacket 6 and the dielectric tube 4. For example, a conventional PVC tubing dielectric within a loose solid copper pipe as the outer conductor and a loose inner conductor was as effective as the RG-62 modified sensor cable embodiment of FIG. 2. Other standard hook-up wire with either tetrafluoroethylene or PVC coating (solid or stranded wire) within a loose outer conductor were also stable alternatives.

Other variant type cables, rather than a variation of RG 62 cable could be used to create the same function. For example “plenum rated” RG type cables exist with a similar “thread in tube” construction, but employ more costly FEP materials, and as such these materials are typically required and used for indoor applications. Constructing a new sensor cable based on an air gap in place of the thread in contact with the inner conductor would provide a similar dual security use. It is also understood that this variant of the sensor cable of the present invention may be more useful for indoor sensing applications.

Other suitable security cables can be constructed to the equivalent dimensions and using the same or similar materials, “bottom up” from conventional cabling processes, rather than as design variants of existing cables. For example, in cable construction there may be further variations, such as a different air gap about the central conductor to affect detection sensitivity, or a stranded center conductor to enhance cable flexibility.

It is understood by the skilled artisan that, for example, the sensor cable of the present invention could be optimized by modifying the center conductor wire, its size, and type; the dielectric tube; and shield, braided or foil. Based on experimental results, it has also been determined that the present invention could have multiple dielectric layers, for example the center conductor could be a coated wire as discussed further with reference to FIG. 3. The sensor cable might alternatively have a smaller dielectric thread loosely disposed on the tube.

FIG. 3 is an view of a sensor cable 10A constructed and manufactured according to a second embodiment of the present invention. The sensor cable 10A shown has a similar construction to that of FIG. 2 with the exception of a thin dielectric layer 15 coated on the center conductor 2A. As is well understood by the skilled artisan, coated conductors are usually form using a thin dielectric layer with material, such as Teflon™. Other dielectric coatings such as PVC are also possible. With this construction the looseness is between the two plastic dielectric layers 15 and 4.

Another alternative is a twisted pair cable construction, for example, where separate dielectric coated wires are twisted together and possibly shielded. FIG. 4 is an view of a sensor cable 10B constructed and manufactured according to a third embodiment of the present invention. The sensor cable 10B consists of a first conductive member 2B coated with a first dielectric layer 15B and loosely disposed within a dielectric tube 4 to move freely within an inner air gap 7, and a second conductive member 5B coated with a second dielectric layer 15B and twisted with the dielectric tube 4. While the two conductive members 2B and 5B are coated with corresponding dielectric layer 15A and 15B, it is readily understood that the dielectric coating may be omitted from the sensor cable construction. It is further readily understood that other cases such as dielectric 4 could be omitted as long as one of the two or more conductors is dielectric coated or jacketed.

For example, a standard category 5 (CAT5) twisted pair cable with 4 pairs is a possible cable construction, where generally each conductor has a dielectric jacket and then two of these are twisted together to create a pair. The number of pairs is variable based on need, and the overall jacket may have a metallic shield underneath; e.g. shielded twisted pair cable, or each pair may further have its own shield.

FIG. 5 shows a side view of the sensor cable 10 of the present invention, which may be optimized for dual use as a sensor cable 10 for ranging purposes. As shown the outer tube 4 loosely encloses the center conductor 2, the outer tube 4 has an inner diameter larger than the outer diameter of the center conductor 2. The cable jacket 6 may be made of polyester elastomer, or any other suitable material. The coaxial cable outer conductor protective shield 5 may be made of tinned braided copper strands for electrical isolation purposes, or such strands in combination with a metallic foil layer or any other suitable electrical conductor. The centre conductor 2 may be any suitable conductor, such as tin-plated copper strands. For the passive use of the triboelectric sensor cable 10, the dielectric outer tube 4 and inner sense conductor 2 are selected based on their triboelectric properties and processes, i.e. manufacturing or handling. For the active ranging function, the sensor cable 10 is optimized according to the present invention for movement of the center conductor 2 in the tube 4 so that there is an adequate change in the capacitance, and hence impedance at the point where there is a disturbance.

The “processes” that determine the selection of dielectric include controlling the manufacturing process of the dielectric materials, or cable, to provide a consistent desired terminal response to a stimulus, or using specific means for electrically/mechanically optimizing the dielectric properties of the selected material by heating, dc or ac hi-pot charging, discharging, etc. While the sensor cable of the present invention does not require any special processing, any processes involved in manufacturing the dielectric material(s) should be consistently controlled.

An alternative construction is possible where the outer conductive member 5 could be a loose conductive cable member relative to the insulating outer tube 4, whereas the center conductor 2 is not free to move relative to the outer tube 4. Alternatively, it is possible that the tube 4 be “floating”, loosely disposed between both conductive members 2 and 5.

A reflectometer may be coupled to the sensor cable 10, such as the Time Domain Reflectometer (TDR) 100 shown in FIG. 6, which can measure the change in impedance as a function of time as it can be synchronized to be directly proportional to the distance along the sensor cable 10.

In this embodiment, the function of the TDR is to interrogate the cable by propagating a pulse down the cable. When the pulse reaches an impedance change along the cable, a portion or all of the pulse energy is reflected back dependent on the size of the impedance change from the cable's characteristic impedance. The TDR measures the time it takes to travel down the cable to the disturbance where the impedance change occurs, and back along the cable. The TDR then forwards the reflected signal information to a processor or to a display. This implementation of the TDR, coupled to a sensor cable, is in an “active” state to provide an “active ranging” cable system. Alternatively, a cable may be coupled to a processor in a “passive” state to provide a “passive” cable system. In a “passive” state, the processor would measure a voltage change, with appropriate additional circuitry in some cases, as a time response function generated on the cable in response to a disturbance. In an embodiment of the present invention, both the passive cable system and the active cable system may be integrated to provide both the passive and the active states of cable sensing.

In FIG. 6, an intrusion detection system 99 of the present invention utilizes a Time Domain Reflectometer (TDR) 100, or a reflectometry unit, to inject a signal into the sensor cable 10 in order to determine the location of the intrusion based on the timing of the reflection of the injected signal. The system 99 shown in FIG. 6 utilizes an optional switch means 115 for a discrete time switching approach where the TDR 100 inputs a voltage (pulse) down the sensor cable 10 and receives a reflection, whereas a processor 110 is passively sensing a voltage output in a time sequence. The sensor cable 10, comprising a loosely disposed conductor and triboelectric construction, will cause both a triboelectric charge transfer, and an impedance change, when an intrusion occurs. The triboelectric charge change is sensed by a system processor 110 whereas the impedance change is sensed by the TDR 100. The time differential relative to the reflection from the impedance change provides the range to the disturbance along the sensor cable 10.

Further in FIG. 6, the intrusion detection system 99 provides a dual functionality on a single coaxial cable, which forms the sensor cable 10, in that the processor 110 can passively sense a disturbance based on a voltage generated, while the TDR 100 may actively sense the reflected pulse along the sensor cable 10. The triboelectric voltage generated on the sensor cable 10 in response to the disturbance can be measured and processed similar to a conventional passive sensor system. Both the active state and the passive state of cable sensing can also be executed in a chosen alternating time sequence by processor control of the switch means 115.

In this implementation of the present invention, a further consideration is thresholding and zoning for determining the presence and location of an intruder. For example, it may be useful to electronically define zones or range bins, that correspond to features of the perimeter where the cable is deployed, such as corners of buildings or gates, in order to activate video assessment or response forces. These zones, or a subset of these zones, may have respective detection thresholds set by a calibration procedure, for example, setting a low threshold in an area where the intruder detection is low (e.g., a very stiff fence), or high for a fence section that provides a large intrusion response.

As shown in FIG. 6, if processing is based on the time response, the sensor cable 10 may be divided electronically into zones or range bins. For example the sensor cable 10 is divided into four zones A, B, C, and D. Each zone is assigned a particular range such that the reflectometer attributes the location of the disturbance based on the zone in which the disturbance is detected.

Processor 110 can be either a time or frequency domain processor 110 in order to perform the dual functionality of detection and location within one processor having an integrated transmitter/receiver unit (not shown). Thus, the TDR 100, as a separate unit, is not required in the intrusion detection system 99 but instead its function can be integrated into the processor 110. The TDR function generally encompasses a method of creating a pulse, injecting it into the cable, and receiving and processing the time-response reflected signal from a cable to monitor signal changes as a function of distance. Thus, the processor 110 could utilize, for example, a directional coupler for separating the transmitted and reflected signals, or a reflection bridge, dependent on the type of signals injected and the application.

In FIG. 7, the passive triboelectric function of the cable is illustrated from a test plot 500 comparison of the sensor cable 10, and the prior art Intelli-FLEX™ cable (not shown) when installed in a typical security application. The test plot 500 captures a time recording of the terminal voltage output of samples of the two cables which are tie wrapped linearly along a hundred feet of an eight foot chain-link fence when struck by a screwdriver. This disturbance simulates the type of signal received as the effect of an intruder trying to cut the fence.

The upper box 505 in FIG. 7 shows the time response, namely voltage versus time in seconds, the lower box 510 the response over frequency in Hertz. The upper trace in the top box 505 is the Intelli-FLEX™ sensor cable and the lower is the sensor cable 10 of the present invention. A small offset between the traces was introduced only to improve visibility. It should be noted that both measurements have a similar time and frequency response to the impact, however the sensor cable 10 of the present invention has a larger voltage response or “sensitivity”.

The active detection with the sensor cable 10 has also been evaluated through experimentation with various processing means including applying the signal with a TDR, or alternatively from a pulse generator and then receiving the reflection from a directional coupler. The results show that the TDR measured return loss change from the above vibration is of the order of 35 dB compared to 46 dB for the comparable Intelli-FLEX™ cable. Thus, the response is much better over the prior art using the inexpensive sensor cable with a larger impedance change from the conductor looseness. Further experiments varying the centre conductor size in the RG-62 cable has shown a very minimal change in the passive sensitivity for conductor size between 16 and 26 AWG. Hence, the conductor can be optimized for other needs such as for impedance changes in the active role, or cable flexibility.

It should be further mentioned that basic processing means for passive systems using cables that produce a terminal voltage are relatively well known. These include filtering, amplifying and signal processing the signal to identify an intruder and yet be insensitive, i.e., not cause nuisance alarms, to environmental response such as wind and rain.

This, with current practice, can largely be done digitally, with the received signal directly digitized and processed in a microprocessor, digital signal processor (DSP), or similar device. Typically such passive sensing systems have no means to locate the intruder along the cable; however there are benefits to providing location of the intrusion along the sensor cable by active means. Active processing means may be implemented by many known means, as disclosed in a United States co-pending patent application, filed on Jul. 28, 2003, entitled “AN INTEGRATED SENSOR CABLE FOR RANGING” and assigned U.S. Ser. No. 10/627,618.

It should be understood that the preferred embodiments mentioned here are merely illustrative of the present invention. Numerous variations in design and use of the present invention may be contemplated in view of the following claims without straying from the intended scope and field of the invention herein disclosed.

Claims

1-34. (canceled)

35. A flexible sensor cable for use in an intrusion detection system having a processor, the flexible sensor cable having an input and an output, both the input and the output of the sensor cable for coupling to the processor, the flexible sensor cable comprising: a first electrically conductive cable member;a second electrically conductive cable member;an air separator and a plastic electrically insulating member both being disposed between the first conductive cable member and the second conductive cable member;the first electrically conductive cable member having one surface in contact with the air separator and being freely movable within the air separator relative to the plastic electrically insulating member, such that the flexible sensor is capable of providing impedance change in response to a disturbance; andthe plastic electrically insulating member being made of a material selected based on triboelectric series properties and being processed such that the flexible sensor cable is capable of producing a terminal voltage with acceptable signal to noise in response to a disturbance.

36. A sensor cable The flexible sensor cable as in claim 35, wherein the terminal voltage is produced based on triboelectric an effect chosen from the group consisting of: triboelectric effect, electret effect, and triboelectric and electret effects.

37. (canceled)

38. (canceled)

39. The flexible sensor cable as in claim 35, wherein the sensor cable is a coaxial cable, and wherein the first electrically conductive cable member encloses the second electrically conductive cable member.

40. The flexible sensor cable as in claim 35, wherein the flexible sensor cable is a coaxial cable, and wherein the second electrically conductive cable member encloses the first electrically conductive cable member.

41. The flexible sensor cable as in claim 35, wherein the flexible sensor cable is a coaxial cable, wherein the second electrically conductive cable member encloses the first electrically conductive cable member, and wherein the sensor cable further includes an outer jacket and a second air separator, such that the second air separator is disposed between the outer jacket of the sensor cable and the plastic electrically insulating member,

42. The flexible sensor cable as in claim 35, wherein the cable is a coaxial cable, and wherein the surface of the first electrically conductive cable member is coated with a dielectric layer.

43. The flexible sensor cable as in claim 35, wherein the cable is a twisted pair cable, wherein the plastic electrically insulating member is a plastic coating on the first electrically conductive cable member, and wherein the plastic coating is twisted with the second electrically conductive cable member.

44. The flexible sensor cable as in claim 35, wherein the plastic electrically insulating member is selected from the group consisting of: polyvinyl chloride, polyethylene, foamed polyethylene, and polypropylene.

45. The flexible sensor cable as in claim 35, wherein the cable is a threadless radio grade (RG) coaxial type cable.

46. The flexible sensor cable as in claim 35, wherein the cable is capable of producing the terminal voltage with an acceptable signal to noise ratio in response to the disturbance, the acceptable signal to noise is being at least an order of magnitude larger than the noise averaged over a period of time.

47. An integrated flexible sensor cable for use in an intrusion detection system having a processor, the flexible sensor cable having an input and an output, both the input and the output of the sensor cable for coupling to the processor, the integrated sensor cable comprising: a first electrically conductive cable member;a second electrically conductive cable member;an air separator and an plastic electrically insulating member both being disposed between the first conductive cable member and the second conductive cable member;the first electrically conductive cable member having one surface in contact with the air separator and being freely movable within the air separator relative to the plastic electrically insulating member, to provide such that the flexible sensor cable is capable of providing an impedance change in response to a disturbance; andthe plastic electrically insulating member being made of a material selected based on triboelectric series properties and being processed such that the cable is capable of producing a terminal voltage with an acceptable signal to noise in response to the disturbance, the acceptable signal to noise ratio being at least an order of magnitude larger than the noise averaged over a period of time.

48. The integrated flexible sensor cable as in claim 47, wherein the cable is a coaxial cable, and wherein the first electrically conductive cable member encloses the second electrically conductive cable member.

49. The integrated flexible sensor cable as in claim 47, wherein the cable is, a coaxial cable, and wherein the second electrically conductive cable member encloses the first electrically conductive cable member.

50. The integrated flexible sensor cable as in claim 47, wherein the cable is a coaxial cable, and wherein the surface of the first electrically conductive cable member is coated with a dielectric layer.

51. The integrated flexible sensor cable as in claim 47, wherein the cable is a twisted pair cable, and wherein the plastic electrically insulating member is twisted together with the second electrically conductive cable member.

52. (canceled)

53. The integrated flexible sensor cable as in claim 47, wherein the cable is a threadless radio grade (RG) type cable.

54. (canceled)

55. A method of manufacturing an integrated flexible sensor cable for use with an intrusion detection system, comprising steps of: a) selecting materials for construction of a coaxial cable, the coaxial cable having a first electrically conductive cable member, a second electrically conductive cable member, and an air separator, a threaded member, and an plastic electrically insulating member, the air separator, the threaded member, and the plastic electrically insulating member being disposed between the first electrically conductive cable member and the second electrically conductive cable member, and the threaded member being wound around the first electrically conductive cable member to prevent movement of the first electrically conductive cable member within the air separator, relative to the insulating member; andb) altering the construction to omit the threaded member from the manufacturing method to form a threadless coaxial cable, the first electrically conductive cable member having one surface in contact with the air separator and being freely movable within the air separator relative to the plastic electrically insulating member, and the plastic electrically insulating member being made of a material having suitable triboelectric series properties and being processed such that the threadless coaxial cable is capable of producing a terminal voltage with acceptable signal to noise in response to a disturbance.

56. The method of manufacturing as in claim 55, wherein the standard coaxial cable selected in step a) is a threaded radio grade (RG) cable.

57. A method of manufacturing an integrated flexible sensor cable for use with an intrusion detection system, comprising steps of: a) selecting materials for construction of a coaxial cable, the coaxial cable having a first electrically conductive cable member, a second electrically conductive cable member, and an air separator, a threaded member, and an plastic electrically insulating member, the air separator, the threaded member, and the plastic electrically insulating member being disposed between the first electrically conductive cable member and the second electrically conductive cable member, and the threaded member being wound around the first electrically conductive cable member to prevent movement of the first electrically conductive cable member within the air separator, relative to the insulating member; andb) altering the construction to omit the threaded member from the manufacturing method to form a threadless coaxial cable, the first electrically conductive cable member having one surface in contact with the air separator and being freely movable within the air separator relative to the plastic electrically insulating member, to provide such that the flexible sensor cable is capable of providing an impedance change in response to a disturbance, and the plastic electrically insulating member being made of a material having suitable triboelectric series properties and being processed such that the de-threaded coaxial cable is capable of producing a terminal voltage with an acceptable signal to noise in response to the disturbance, the acceptable signal to noise ratio being at least an order of magnitude larger than the noise averaged over a period of time.

58. The method of manufacturing as in claim 57, wherein the coaxial cable selected in step a) is a threaded radio grade (RG) cable, and further including the step of coupling the threadless coaxial cable to the intrusion detection system for use as a sensing element in the intrusion detection system.

59. (canceled)

60. (canceled)

61. (canceled)

62. An intrusion detection system comprising: a flexible cable having a first electrically conductive cable member, a second electrically conductive cable member, and an air separator and an plastic electrically insulating member both being disposed between the first electrically conductive cable member and the second electrically conductive cable member, the first electrically conductive cable member having one surface in contact with the air separator and being freely movable within the air separator relative to the plastic electrically insulating member, to provide such that the flexible cable is capable of providing an impedance change in response to a disturbance, and the plastic electrically insulating member being made of a material selected based on triboelectric series properties and being processed such that the flexible cable is capable of producing a terminal voltage with acceptable signal to noise in response to the disturbance; anda processor, operatively coupled to the flexible cable, for propagating, in an active state, an injected signal into the flexible cable and receiving a reflected signal altered by the impedance change along the flexible cable, and locating the disturbance based on a timing differential, and for generating a signal, in a passive state, in response to the terminal voltage produced from the flexible cable in order to detect the disturbance.

63. (canceled)

64. (canceled)

65. (canceled)

66. The intrusion detection system as in claim 62, further including switching means operatively coupled to the processor for alternating in a time sequence between the passive state and the active state.

67. The intrusion detection system of claim 62, further including switching means operatively coupled between the processor and the flexible cable to form a connection path to the flexible cable, and a time domain reflectometer, operatively coupled to the processor and the switching means, for propagating an injected signal into the cable and receiving a reflected signal altered by the impedance change along the flexible cable, wherein the switching means is capable of opening and closing the connection path to the flexible cable.

68. (canceled)