GB2517093A

GB2517093A - Fence with sensor cable

Info

Publication number: GB2517093A
Application number: GB1417388.4A
Authority: GB
Inventors: David Binks; Shaun Moores; Paul Griffin; Chris Mangham
Original assignee: CRH Fencing and Security Group UK Ltd
Current assignee: CRH Fencing and Security Group UK Ltd
Priority date: 2012-10-11
Filing date: 2013-09-13
Publication date: 2015-02-11
Anticipated expiration: 2033-09-13
Also published as: GB201316345D0; WO2014057278A1; GB2517093B; GB2507864B; GB201218289D0; GB2507864A; GB201417388D0

Abstract

A fence includes a rail (20) having a recess (figure 5B: 30) containing a sensor cable (40), and brackets (10) having a front wall (figure 4A: 14) and upper (15) and lower (16) walls which enclose the ends (21') of the rail so as to prevent access to the cable other than from the rear. Preferably the rail is angularly adjustable with respect to the brackets, so that the fence can be installed on sloping ground without exposing the cable at the ends of the rails. Preferably the brackets are moulded from non ferrous metal with integral tubular extensions (12) providing a smooth cable path through each of the posts (1). The fence preferably includes retaining elements (61) which retain the sensor cable in the recess. The retaining elements ensure that the cable remains in contact with the rail along substantially all of the length of the rail so as to transfer vibrational energy more effectively from the fence to the cable.

Description

Fence with sensor cable This invention relates to fences having a sensor cable for sensing intrusion or attack.

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Tn this specification, a sensor cable means any cable configured to extend along a fence and to provide, either individually or as one of an array of such cables, a signal responsive to unauthorised activity at the fence, for example, when a person attempts to cutt or climb the fence. Usually, by analysing the signal it is also possible to identify the location along the length of the fence of the activity giving risc to the signal.

Some such sensor cables are configured to sense vibrations in the fence. In this specification, a cable for sensing vibration is takcn to include for example a microphonic sensing cable for sensing sound travelling through the fence, and a cable is taken to include an electrically conductive cable and a fibre-optic cable.

By way of example, W0201 1073624 and GB2l7577l disclose microphonic sensor cables having one or more conductors moveably disposed in a magnetic held, so that vibrations induced in the fence cause movement of the conductor which in turn induces a signal in the conductor. Similarly, it is known to detect vibration such as sound waves by measuring the distortion of light travelling through an optical fibre disposed in a fibre optic cable. The signal can be analysed and output in audible form via a transducer, whereby a trained operator listening to the signal can readily identi the sound and hence the nature of the incident giving rise to the signal so as to distinguish between, for example, a person climbing the fence, an animal burrowing under the fence, or a tool cutting the fen cc.

Typically, the fence will comprise a series of panels supported between vertical posts set in the ground. the panels typically being made from a mesh such as a welded, expanded or chainlink mesh and fixed at intervals to rails (also known as stringers) extending between the posts, the rails being attached to the posts either by means of bolts or by means of brackets which arc welded or bolted to the posts.

A long fence will generally be divided into zones with a separate scnsor cable or array of sensor cables extending along each zone, each sensor cable typically being connected at one or both ends to a further cable which also extends along the fence and transmits signals between the sensor cable and the monitoring equipment to which it is connected.

Conventionally the sensor cable has been arranged along the length of the fence and attached at intervals to the mesh. More recently it has been known to arrange the sensor cable between each pair of posts within one ol the rails so that it extends along the rails through holes in the posts betwccn the rails, as illustrated for example in Figs. 1 A -IC. This provides more convenient installation and more effectively couples vibrations induced in the fence panels to the cable, so that sensitivity is improved and false alarms are reduced.

One problem associated with this prior art construction is that the cable remains vulnerable to interference, particularly where (due to its sinuous shape) it protrudes visibly from the rail, and in those portions which are accessible between the end of the rail and the post, for example, where the posts are spaced slightly too far apart so as to leave a gap at that point (Fig. 1A). or where the rail is angled relative to the post so as to leave a gap between its upper or lower extremity and the post (Fig. 1B). By inserting a tool through the mesh it may he possible to pull the exposed cable out of the rail and cut it, which will generate an alarm but also necessitate a repair.

DFl02007002852 Al, D[102006003758 Al, and DL 102005055060 B3 disclose various channel profiles which can be welded, clipped or otherwise mechanically attached to the mesh of a fence panel to support a sensor cable which may be enclosed in the channel or retained by wedges or other bodies inserted into the channel.

Where the channel has a downwardly thcing opening, it is found that the wedges can fall out oithe channel, making it necessary to retain the cable by injecting a mastic into the channel. In practice, even whcrc the wedges remain in position, the cable may also sag visibly from the channel between the wedges, exposing it to damage, while the use of mastic is inconvenient and reduces the sensitivity of the cable.

In each case the usc of additional channel profiles adds significant cost and complexity to the installation. Where a light weight channel profile is clipped or locally bent to attach it to the mesh of the panel, the fixings may render it vulnerable to attack from the front of the fence. Alternatively the profile may be fixed by welding, which however is particularly inconvenient and costly.

A further problem is that the cable may be exposed at the ends of the channel where it crosses the post between adjacent panels. Moreover, in each case, the mechanical connection between thc profile and the individual wires of the panel would seem to constrain each of the profiles to a horizontal orientation corresponding to the rectilinear structure of the mesh.

In consequence, where sloping ground requires a vertical offset between the channel profiles on adjacent panels, still more of the cable may be exposed to damage where it runs between the ends of the adjacent channel profiles in the region of the post. This could be mitigated by running the cable vertically through a portion of the hollow post between the channel profiles, which however would require on-site drilling of each post to provide vertically offset holes corresponding to the positions of the two adjacent channel profiles. The offset holes would significantly increase the frictional pulling resistance of the cable through the post so that it would need to be fed completely through each post, one at at time. This will add considerable time and cost to an installation, especially on a long cable run.

In an alternative approach, DE8808533 lil and DE29503595 UI disclose Fences in which a sensor cable is concealed within a cavity formed between a pair of nested channel profiles which are attached to the bars or mesh of the panels.

Although the cable is concealed and protected in the region where it extends between the posts of the fence, the additional channel profiles and the additional step of flxing them to the panels adds cost and complexity to the assembly of thc fence. Moreover, in each case, the rectilinear structure of the panels would seem to constrain each of the profiles to a horizontal orientation. If the fence is installed on sloping ground then adjacent pairs of channel profiles will he vertically offset from one another, which again gives rise to the problem of how to protect the cable in the region where it crosses the post.

Assembly will he further coniplicatcd where (as some of the above mentioned art would seem to require) the cable must be installed during, rather than after, installation of the panels. with any subsequent work on the cable requiring the panels to be removed and re-installed.

It is the object oithe present invention to provide a more satisfactory fence comprising a sensor cable. In particular, the fence should be cost-effective and easy to assemble while concealing the sensor cable and protecting it from damage.

Preferably these advantages should be realised, also when the fence is installed on sloping ground.

Accordingly in its various aspects the present invention provides a fence as defincd in the claims.

In a particularly preferred embodiment, a fence includes a rail supported by each pair of posts and having a recess which contains the sensor cable, together with a plurahty of retaining elements which retain the sensor cable in the recess of each rail, and brackets having a front wall and upper and lower walls which enclose the ends of the rail so as to prevent access to the cable other than from the rear of the fence. Preferably the rail is angularly adjustable with respect to the brackets, so that the rails can be angled to follow the slope of the pound. with the adjacent ends of the rails arranged in horizontal alignment on either side of the post. This allows the fence to be installed on sloping ground without exposing the cable at the ends of the rails, while a long run of cable can be easily installed by pulling it through the pre-forined (e.g. punched or drilled), horizontally aligned holes in the posts after installation of the panels.

The sensor cable is easy to install after the fence has been erected, and does not I S require any additional special components except for the multiple retaining elements which may be small and low in cost.

It is found that, where the sensor cable is configured to sense vibrations (e.g. sound waves) in the fence, its sensitivity can be optimised by inserting it into a recess in the rail and retaining it in the recess. Since the sensor cable is typically somewhat stiff and will naturally lie along a somewhat sinuous path, it is found that even where it is tucked into a rcccss in the rail during installation, it may not remain within the recess and therefore may not make contact with the rail along the whole of its length. The retaining elements in combination with the rail ensure that the cable remains within the recess and so makes contact with at least one of the walls of the recess along substantially all of the length of the rail, which optimally couples the cable to the rail and (since the rail is attached to the posts) hence also to the posts. This transfers vibrational energy (e.g. sound waves) more effectively from the fence to the cable, irrespective of the locus of the attack (whether at the rail, panel, or post).

At the same time, by retaining the cable in the recess in the rail for the whole length of the rail, the retaining elements make it impossible to withdraw the cable from the rail by means of a tool inserted through the mesh. The orientation of the recess prevents the cable from sagging and protruding visibly from the rail in the gaps between the retaining elements, while the brackets protect the cable at the ends of the rails, even where the rails are angled so as to follow the slope of the ground. The cable is thus concealed and protected along its entire length.

Advantageously, by using the angled rails to house the sensor cable, the posts can be punched or drilled at the factory in a predetermined position to provide a short, horizontally aligned cable path through each post. This makes insertion of the cable easy and minirniscs its frictional pulling resistance, significantly shortening the installation time on long cable runs and avoiding the need for on-site drilling.

Still more advantageously, each bracket includes a tubular extension which is inserted into the hole in the post to protect the cable from damage by the cut edges of the hole. Most preferably, the bracket is inoulded from a non-ferrous metal, so that the integrally moulded tubular extension provides a. very smooth path for the cable. This makes it possible to pull the cable through several posts simultaneously, even where the rails are angled to follow the slope of the ground.

Further features and advantages will be evident from the following illustrative embodiments which will now he described, purely by way of example and without limitation to the scope of the claims, and with reference to the accompanying drawings, in which: Figs. 1A, lB and lC show a prior art fence, rcspectively from the rear where the posts are spaced to form a gap at the rail end; from the rear where the rail is angled with respect to the post; and from the side; Fig. 2 is a plan view of a first fence according to a first embodiment of the invention; Figs. 3A, 3B, 3C and 3D show a first retaining element of the first fence, respectively in oblique, end, rear, and plan view; Figs. 4A, 413, 4C and 4D show one bracket of the first fence, respectively in oblique, end, rear, and plan view; 1 0 Figs. 5A, 5B, 5C and SD show an end portion of one rail of the first fence, respectively in an oblique view, an enlarged end view, a rear view, and a plan view; Figs. 6A, 6B and 6C shows one clamp of the first fence, respectively in front, end, and side view; Fig. 7 is a plan view of a portion of the first fence showing one post in cross-section; Fig. 8 is a rear view of the portion of the first fence shown in Fig. 7; Fig. 9 is a vertical section through the first fence showing one of the posts in side view; Fig. 10 is an end view of a further rail in accordance wiih an alternative embodiment; Fig. 1 1A is an end view of a yet further rail in accordance with a further alternative embodiment;

S

Fig. 1 lB is a longitudinal section at B -B through the rail of Fig. 1 1A; Figs. 12A, 12B and 12C show a second retaining element, respectively in oblique, end, and front view; Fig. 13 is a plan view of a portion of a second fence comprising the second retaining element, showing one post in cross-section; Fig. 14 is a vertical section through a portion of the second fence of Fig. 13 showing the post in side view; Fig. 15 shows the second retaining element installed in the portion of the second fence olFig, 14; and Figs. 16 and 17 are traces of a sound signal obtained in tests from a fence having a sensor cable and mesh panels fixed to rails supported between posts, respectively by striking one of the panels (Fig. 16A, 16B) and one of the posts (Figs. 17A, 17B), with the sensor cable being respectively retained in a recess in the rail (Figs.

16A. 17A) and attached at intervals to the mesh panels (Figs. 16B, 1 7B).

Corresponding reference numerals indicate corresponding features in each of the figures.

Referring to Figs. 2 -9. a first fence comprises a plurality of tubular steel posts 1 arranged in spaced relation, with a plurality of panels 2 being arranged between the posts so that the fence and panels present a front (attack) side 3 and an opposite, rear side 4. In the illustrated embodiment, each panel comprises a welded steel security mesh, although in alternative embodiments. chainlink or expanded metal panels, solid sheet panels, or any other type of panel offering a suitable level of security might be provided.

Each post has a pair of brackets 10. Each bracket includes an end wall 11 which is arranged in use against a respective side of the post, the end wall having an integral tubular extension 12 with a smooth bore 13; a front wall 14 which extends from the end wall and faces the rear side 4 of the respective panel; and upper 15 and lower 16 walls which extend from the front waIl 14 away from the rear side of the panel. 1 0

By forming the upper and lower walls 15. 16 integrally with the front and end walls 14, 11 of the bracket, it is surprisingly found that the bracket can be moulded (e.g. die-cast) from a non-ferrous metal such as an aluminium, zinc, magnesium and/or copper alloy (rather than being pressed or fabricated from steel plate in the conventional way) and yet still have sufficient strength. This advantageously allows the tubular extension 12 to be formed integrally with the rear wall so as to form a smooth path for the cable, which makes it easy to pull a long length of cable through several posts simultaneously, even where the cable run is angled to follow sloping ground. Furthermore, it prevents the upper and lower walls 15, 16 from being levered away from the end or front wall so as to gain access to the sensor cable 40 from the front (attack) side of the fence, which might be possible with a pressed steel bracket.

Each bracket is fixed to the respective post by means of a bolt 17 received in an aperture 18 in the end wall of the bracket, so that the tubular extensions 12 are received in respective prc-formcd holes 5 arranged in horizontal alignment on opposite sides of the post, locking the bracket against rotation and protecting the cable from damage on the sharp edges of the hole.

A steel rail 20 is attached to each pair of posts 1, with each end portion 21 of the rail being attached by means of a bolt 22 in angularly adjustable relation to the front wall of one of the brackets. In this manner each rail is attached (via the bracket) in angularly adjustable relation to the respectivc post so that the rails may 3 he angled to Follow the slope of the ground. [he end 21' of the rail is arranged between the upper and lower walls 15, 16 of the bracket so that even where there is a gap between the end of the rail and the post. and irrespective of the angle of the rail, the waIls 14, 15, 16 of the bracket enclose the end of the rail so as to conceal and protect the sensor cable in that region.

In practice, two or more rails 20 will generally be arranged in spaced relation between each pair of posts, with one or more sensor cables extending along the fence within the respective rail or rails. The or each sensor cable is configured as known in the art to provide a signal responsive to unauthorised activity at the fence, and advantageously may be configured to detect vibrations, particularly sound waves transmitted through the fence, as in the illustrated embodiment wherein the sensor cable 40 comprises two copper conductors 41 which are free to move within tubular conduits 42 arranged in a body 43 of magnetic material.

Suitable microphonie sensor cables sensitive to vibration are available for example from Geoquip Limited of Little Eaton, Derbyshire, United Kingdom; other types of sensor cable may also be used. Vibration sensing cables, particularly microphonic sensor cables, either of electrical or libre-optic type, arc particularly preferred since they provide a signal which enables the operator to identify the nature of the activity so as to avoid false alarms.

The rail 20 includes a front wall 23 which laces a rear side 4 of the respective panel, and upper 24 and lower 25 walls which extend generally in a horizontal plane from the front vail 23 away from the rear side of the panel. The lower wall has a short upturned portion 26 supporting an inner, return wall 27 which extends horizontally (when considered in cross-section) towards the front wall between the upper and lower walls. The inner wall terminates at an edge 28 which lies beneath the upper wall when considered in plan view, so that the interior of the rail is concealed when seen from thc front (attack) side of thc fence. A rcccss extends along the rail between the inner wall and lower wall and has an open side 31 which faces the front wall. At the end portions of the rail, the inner wall 27 is cut back at an angle as shown so as to facilitate the insertion of the cable end into the tubular extensions 12 of the bracket. Each rail is provided with a plurality of retaining elements whereby the sensor cable 40 is retained in the recess 30, as ftirther described below.

Advantageously, the front wall 23 of the rail is solid rather than comprising a series of apertures 101 as in the rail 100 of the prior art fence illustrated in Figs. lA -IC. This makes the sensor cable inaccessible from the front (attack) side of the Fence and also helps to shield it from wind.

Each panel is attachcd to the or each rail by mcans of a plurality olclamp assemblies 50, each assembly 50 comprising a clamp plate 51 with prongs 52 which engage between the wires of the mesh panel 2, and a bolt 53 which is inserted through the clamp plate, panel and rail and secured by means of a shear nut 55 (i.e. a nut having a head which shears oI'f when the nut is tightened so as to prevent subsequent disassembly) so that the threaded rod 54, i.e. the threaded portion of the bolt, cxtcnds through thc shear nut inside the rail. Of course, in alternative embodiments the clamp plate 5 1 could be provided with a threaded stud or the like rather than a separate bolt.

After fixing the panels to the rails, the or each sensor cable 40 is arranged between each respective pair of adjacent posts I in the recess 30 of the rail so that it extends betwccn thc cnds of the adjacent rails through the post via the smoothly curved bore 13 of the tubular extension 12 of each of the pair of brackets, which protects it from damage where it enters the post.

A plurality of retaining elements 60 are operatively engagca.ble (i.e. engageable either directly or indirectly) with the rail, each retaining element being individually positioned during installation to retain the cable in the recess. In the 3 first embodiment each retaining element 60 comprises an insert which is molLlded from plastics material, having a flat plate 61 arranged on a body 62 with outwardly protruding fins 63 and a flat rear surface 64. In use, several inserts are arranged in spaced relation along each rail, each insert being pressed into the rail between the edge 28 ot'the inner wall 27 and the rear surface 23' of the front wall 23 so that the flat rear surface 64 of the bracket extends across the open side 31 of the recess as shown to retain the sensor cable in the recess, and the fins engage in snap-fit relation beneath the edge 28 of the inner wall, retaining the insert securely in place. The sensor cable 40 thus remains in contact for substantially the whole length of the rail with at least one olthe three walls 25. 26,27 of the recess. The snap-fit retaining element is easy to insert but very difficult to remove from the front (attack) side of the fence, particularly where it is concealed behind the front wall of the rail.

Referring to Figs. 16 and 17. it is found that the signal (shown as amplitude A a.gainst time T) produced by a typical percussive attack on the fcnce contains more information and less resonance when the sensor cable is retained in the recess for the full length of the rail (Figs. 1 6A, 1 7A) then when it is secured at intervals to the mesh of the panels (Figs. 1ÔB, PB). this being true where the attack is against the post (Figs 1 7A, I 7B) as well as where the attack is against one of the panels (Figs. bA, lOB). It can be seen that when the cable is arranged in the rail and the rail is attached to the post, an attack against the post is clearly picked up by the cable (Fig. l7A).

By arranging the sensor cable within the rail, it is also shielded from wind which tends to generate spurious signals resulting from resonant movement of the cable; in extreme wind conditions, the additional shielding provided by the novel brackets may also help to reduce spurious signals.

Referring to Fig. 10, in an alternative embodiment, the rail 70 is generally similar to that described above, hut the inner wall 71 is formed with a slightly downturned lip 72 so that the open side 73 of the recess 74 is slightly narrower than the external diameter of the sensor cable 40. The cable is slightly elastically deformed as it is pushed into the recess, so that the lip 72 retains the cable in the recess for the whole length of the rail.

Referring to Figs. 11A and lAB, in a yet further embodiment, rather than being individually attachable in fixed relation to the rail as described above, the retaining elements may be integral with the rail. In this case the retaining elements may comprise a plurality of individual tabs 80 cut from the inner wall 81 of the rail 82, one of which is shown in the illustration, each tab 80 being positioned to obstruct the open side of the recess by bending it dovnward1y after installing the cable in the recess so as to retain the cable in the recess.

Referring now to Figs. 12 -15, a second fence is formed generally like the first, but includes a further cable 45 arranged in parallel with the sensor cable 40 in a position where it obstructs the open side 31 of the recess 30 in the rail 20. The further cable 45 may be used to connect one or both ends of the sensor cable 40 to remote monitoring and interrogation equipment as known in the art, and/or to carry signals between the remote monitoring station (not shown) and further sensor cables, cameras or the like, and so will typically extend along a considerable length of the fence, perhaps through many separate zones. In use, the sensor cable 40 is arranged in the recess 30 before the further cable 45 is installed, so that the tUrther cable 45 lies in the portion of the rail outside the recess 30 as shown.

A plurality of retaining elements 90 are then inserted into the rail, each retaining clement comprising a plastics block having a chamfcrcd front face 9 1 with an intcma.lly ribbed hole 92. Each block is engaged with a respective one of the clamp assemblies 50 by pushing it onto the threaded portion 54 of the bolt 53 in the axial direction of the bolt as indicated by the arrow, so that the threaded rod 54 enters into the hole 92, the internal ribs retaining the retaining element 90 securely on the bolt 53. The chamfered edge of the block engages the further cable 45 to retain it in the rail 20, and the further cable 45 in turn retains the sensor cable 40 in the recess 30.

Of course, although optimal sensitivity and security is obtained by providing both the novel retaining elements and the novel brackets in combination as shown, in alternative embodiments the brackets could be used separately.

Although in the illustrated embodiments the recess is formed between the inner wall 27 and the lower wall 25 of the rail, the rail could of course be inverted so that the recess is formed instead between ihe upper wall and the inner return wall.

Other configurations will be evident to those skilled in the art, including for example hollow, tubular rails which contain the sensor cable between the brackets.

The retaining elements retain the cable in the recess so tha.t it does not move out of the recess unless it is deliberately removed, e.g. by first detaching or deforming the retaining elements. Advantageously, this may be difficult or impossible to accomplish from the front (attack) side of the fence.

The recess may be dimensioned so that the sensor cable is a snug fit in the recess.

The retaining elements may also be arranged to contact the cable so as to engage it positively against a wall or walls of the recess.

In alternative embodiments, each retaining element could be for example a clip made from spring steel which is inserted into the rail in snap-fit relation, or having a hole with inwardly projecting teeth which engage the threaded rod when the clip is pushed over the rod, or could be threaded so as to be screwed onto the rod. The retaining elements could be made from rubber, plastics, metal or any other suitable material. Each retaining element may be removable to facilitate maintenance of the cable, or alternatively may be configured for one-way application so that it is very difficult to remove once fixed. In yet further alternative embodiments the retaining elements could be attached by means of screws or other suitable fixings, or could form an integral part of each clamp assembly, such as a part of the bolt or a suitably shaped threaded component engaged with the bolt. Each retaining element could have a recess or recesses for individually receiving the sensor cable and/or further cable.

In alternative embodiments, the brackets could be made from steel or even, where it meets the requirements of a particular installation, a suitable high strength plastics material. In less preferred embodiments, the brackets may be moulded in non-ferrous with tubular extensions providing a smooth cable path but without upper and/or lower walls. It will be appreciated that the rail is prelerably attached to the posts by means of the brackets, which is to say, the rail is fixed to the brackets and the brackets arc fixed to the posts.

Many further adaptations are possible within the scope of the claims.

Claims

CLAIMSI. A fence comprising: a plurality of posts (1) arranged in spaced relation; a plurality of panels (2) arranged between the posts; each respective panel being attached to a respective rail (20), the rail extending between a respective pair of said posts; each rail having a recess (30) extending along the rail; and a sensor cable (40) configured to provide a signal responsive to unauthorised activity at the fence, the sensor cable extending along the fence, the sensor cable being arranged between each respective pair of adjacent posts in the recess of thc respective rail; eharactcriscd in that each post has a pair of brackets (10). and cach rail has two end portions (21) which are attached respectively to respective ones of the brackets; each bracket including a front wall (14) which faces a rear side (4) of a respective panel, and upper (15) and lower (16) walls which extend from the front wall away from the rear side of the panel; and a respective end (21') of the rail is arranged between the upper and lower walls.
2. A fence according to claim I, wherein each rail is attachable in angularly adjustable relation to the brackets so that the rails may he angled to follow sloping ground.
3. A fence according to claim 1 or claim 2, wherein each bracket includes a tubular extension (12), the bracket being fixed to the respective post so that the tubular extension is received in a hole (5) in the post; and the sensor cable is arranged to extend between adjacent rails through the post via the tubular extensions of the pair of brackets.
4. A fence according to claim 3, wherein each bracket is mouldcd from a non-ferrous metal, and the tubular extension provides a smooth path for the cable.
5. A fence according to claim 3 or claim 4, wherein the tubular extensions of the pair of brackets are arranged in a pair of holes (5) which are horizontally aligned on opposite sides of the post.
6. A fence according to any of claims 1 -5, wherein each rail includes a front wall (23) which faces a rear side (4) of the respective panel, upper (24) and lower (25) walls which extend from the front wall away from the rear side of the panel, and an inner wall (27) arranged between the upper and lower walls; and the recess (30) is defined between the inner wall and a respective one of the upper and lower walls and has an open side (31) which faces the front wall.
7. A fence according to any of claims I 6, wherein the sensor cable is configured to provide a signal responsive to vibration.