GB2185841A - Intrusion detector - Google Patents

Abstract

An intrusion detector comprises a number of spaced apart electrically non-conductive posts 10, 12, 14 to which substantially parallel sensing wires 16, 18,20 are attached by insulating P-clips 22. The lower series 20 of three wires are relatively closely spaced compared to the spacing of the upper series 16 of three wires. For example, the spacing of the lower wires 20 is of the order of 30cm compared to 60cm spacing for the upper wires 16. A reference wire 18 connected to ground is provided between the upper and lower series of wires 16, 20 and all the wires 16, 18, 20 are connected at 24 to suitable energising and detection means (not specifically illustrated). The spacing has the effect that a low profile, e.g. a crawling, intruder adjacent to the lower wires 20 provides substantially the same level of signal disturbance as a high profile e.g. a jumping, intruder to the upper wires 16. <IMAGE>

Description

SPECIFICATION Intrusion detector This invention concerns an intrusion detector and more particularly to an improved configuration of sensing wires used in conjunction with appropriate energising and detection means to form an intrusion detection device of a linear nature suitable for external perimeters intrusion detection.

In accordance with the present invention an intrusion detection as aforesaid comprises an upper series of wires substantially parallel to and above one another and a lower series of wires substantially parallel to and above one another, said upper series of wires being substantially in the same place above the lower series of wires, characterised in that the wires of the lower series are more closely spaced relative to one another than those of the upper series.

With such an arrangement, the arrangement can be such that the lower series of wires will provide substantially the same level of signal disturbance when approached by a low profile intruder (e.g. a crawling person) as will be the case for a high profile intruder (e.g. a person attempting to jump over the wires).

In one practical embodiment, the verticallyspaced parallel wires are erected on their own dedicated support structures, such as a series of insulated posts. Alternatively, the wires may be mounted upon an existing mechanical fence structure or the like, e.g. a metal mesh fence, a wooden or other fence, provided the wires are insulated therefrom.

The invention will be described further, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a schematic elevation illustrating a first practical embodiment of the intrusion detector of the invention; and Figure 2 is a schematic elevation illustrating a second embodiment of the intrusion detector of the invention.

Referring firstly to Fig. 1, a typical embodiment of the intruder detector of the invention comprises a succession of electrically nonconductive posts 10, 12, 14 suitably spaced apart and to which substantially parallel sensing wires 16, 18 and 20 are attached by means of insulating P-clips indicated diagrammatically at 22. The lower series of wires 20 (which in the illustrated case are three in number, but which may comprise any practical number) are relatively closely spaced, for example of the order of 30cm, and above these is located the wire 18 which is a reference wire connected to ground. Above this ground wire 18 is the second or upper series of sensing wires 16, these being arranged at a relatively greater spacing than the spacing of the lower wires 16, for example of the order of 60cm.All of the sensing wires 16, 20 are connected as at 24 to suitable energising and detection means (not specifically illustrated in the drawing).

In the alternative embodiment illustrated in Fig. 2, posts 30 (of which one only is shown) support sensing wires 32 and 36, and reference wire 34, these wires corresponding to the wires 16, 20, 18 of Fig. 1, but being arranged in opposed pairs. In this instance, separate signal processors are required as at 38, 40.

It will be appreciated that these two specific embodiments are not exclusive, and that other configurations are possible. In the illustrated and alternative configurations, the objective is that the lower sensing wires 20, 36 should be more closely spaced than the upper sensing wires 16, 32. This has the effect that a low profile, e.g. crawling, intruder adjacent to the lower wires 20, 36 provides substantially the same level of signal disturbance as would be the case of a high profile, e.g. a jumping, intruder to the upper sensing array 16, 32 as a whole. With this configuration, the signal to noise ratio resulting from an intrusion by either profile remains substantially the same and obviates the necessity of electronic differential enhancement of the signals as is needed with equally spaced wires throughout.

The specific forms of the electronic signal processing means for processing the resulting signals is not important to the invention, and any suitable arrangement which will be activated to provide an alarm upon approach of an intruder may be used. One such arrangement is described in U.K. Patent No.

2040093B which describes a preferred method of energising and intrusion detection by wire configurations, which can be used in the present invention.

Of course, in each of the series of wires in the arrangement of the invention, the spacing between the wires of the series need not be constant and variable pitch spacing (for example quasi-logarithmic with increase of spacing with increase in height) may be employed.

1. An intrusion detector comprising an upper series of wires substantially parallel to and above one another and a lower series of wires substantially parallel to and above one another, said upper series of wires being substantially in the same place above the lower series of wires, characterised in that the wires of the lower series are more closely spaced relative to one another than those of the upper series.

2. An intrusion detector as claimed in claim 1 wherein the vertically spaced parallel wires are erected on a series of support structures.

3. An intrusion detector as claimed in claim 2 wherein the wires are attached to the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Intrusion detector This invention concerns an intrusion detector and more particularly to an improved configuration of sensing wires used in conjunction with appropriate energising and detection means to form an intrusion detection device of a linear nature suitable for external perimeters intrusion detection. In accordance with the present invention an intrusion detection as aforesaid comprises an upper series of wires substantially parallel to and above one another and a lower series of wires substantially parallel to and above one another, said upper series of wires being substantially in the same place above the lower series of wires, characterised in that the wires of the lower series are more closely spaced relative to one another than those of the upper series. With such an arrangement, the arrangement can be such that the lower series of wires will provide substantially the same level of signal disturbance when approached by a low profile intruder (e.g. a crawling person) as will be the case for a high profile intruder (e.g. a person attempting to jump over the wires). In one practical embodiment, the verticallyspaced parallel wires are erected on their own dedicated support structures, such as a series of insulated posts. Alternatively, the wires may be mounted upon an existing mechanical fence structure or the like, e.g. a metal mesh fence, a wooden or other fence, provided the wires are insulated therefrom. The invention will be described further, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a schematic elevation illustrating a first practical embodiment of the intrusion detector of the invention; and Figure 2 is a schematic elevation illustrating a second embodiment of the intrusion detector of the invention. Referring firstly to Fig. 1, a typical embodiment of the intruder detector of the invention comprises a succession of electrically nonconductive posts 10, 12, 14 suitably spaced apart and to which substantially parallel sensing wires 16, 18 and 20 are attached by means of insulating P-clips indicated diagrammatically at 22. The lower series of wires 20 (which in the illustrated case are three in number, but which may comprise any practical number) are relatively closely spaced, for example of the order of 30cm, and above these is located the wire 18 which is a reference wire connected to ground. Above this ground wire 18 is the second or upper series of sensing wires 16, these being arranged at a relatively greater spacing than the spacing of the lower wires 16, for example of the order of 60cm.All of the sensing wires 16, 20 are connected as at 24 to suitable energising and detection means (not specifically illustrated in the drawing). In the alternative embodiment illustrated in Fig. 2, posts 30 (of which one only is shown) support sensing wires 32 and 36, and reference wire 34, these wires corresponding to the wires 16, 20, 18 of Fig. 1, but being arranged in opposed pairs. In this instance, separate signal processors are required as at 38, 40. It will be appreciated that these two specific embodiments are not exclusive, and that other configurations are possible. In the illustrated and alternative configurations, the objective is that the lower sensing wires 20, 36 should be more closely spaced than the upper sensing wires 16, 32. This has the effect that a low profile, e.g. crawling, intruder adjacent to the lower wires 20, 36 provides substantially the same level of signal disturbance as would be the case of a high profile, e.g. a jumping, intruder to the upper sensing array 16, 32 as a whole. With this configuration, the signal to noise ratio resulting from an intrusion by either profile remains substantially the same and obviates the necessity of electronic differential enhancement of the signals as is needed with equally spaced wires throughout. The specific forms of the electronic signal processing means for processing the resulting signals is not important to the invention, and any suitable arrangement which will be activated to provide an alarm upon approach of an intruder may be used. One such arrangement is described in U.K. Patent No. 2040093B which describes a preferred method of energising and intrusion detection by wire configurations, which can be used in the present invention. Of course, in each of the series of wires in the arrangement of the invention, the spacing between the wires of the series need not be constant and variable pitch spacing (for example quasi-logarithmic with increase of spacing with increase in height) may be employed. CLAIMS

1. An intrusion detector comprising an upper series of wires substantially parallel to and above one another and a lower series of wires substantially parallel to and above one another, said upper series of wires being substantially in the same place above the lower series of wires, characterised in that the wires of the lower series are more closely spaced relative to one another than those of the upper series.

2. An intrusion detector as claimed in claim 1 wherein the vertically spaced parallel wires are erected on a series of support structures.

3. An intrusion detector as claimed in claim 2 wherein the wires are attached to the support structures such that the wires are insulated therefrom.

4. An intrusion detector as claimed in claim 1 wherein the vertically spaced parallel wires are mounted upon an existing mechanical fence structure, the wires being mounted so as to be insulated therefrom.

5. An intrusion detector substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.