PRIORITY

|C>0011 The present application claims priority from;

Australian Provisional Patent Application No. 2013901929 titled "Ά

CHONDRICHTHYAN REPELLING SYSTEM", filed on 30 May 2013.

The content of this application is hereby incorporated by reference in its entirety. INCORPORATION BY REFERENCE

[0002] The following publications are referred to in the present application and their contents are hereby incorporated by reference in their entirety:

United States Patent No. 5,566,643 titled "Control of Sharks" (also published as Australian Patent No. 669806) assigned to Natal Sharks Board.

TECHNICAL FIELD

[0003] The present application relates to a chondrkttthyan repelling system using electrical fields generated by an electrical signal generator.

BACKGROUND

[0004] Recorded shark attacks have steadily increased in recent times, while .at the .same time the desire to offer conservation and protection to sharks has also increased as populations dwindle significantly.

[0005] It is known that all chondrichthyans such as predatory sharks have highly sensitive electrical -receptors called the "Ampullae of Lorenzini" located in their snouts. These tiny gel -filled sacs sense electrical current from prey, but only at very close distances, typiealiy less than one meter. 0006} Conventional shark repelling devices are arranged to generate a localised electrical field that causes the ampullae to spasm and consequently the shark to m ve away from the generated Field,

[0007] A typical such conventional device includes a 2.2m trailing antenna provided with two electrical contacts in electrical communication with the surrounding water, and an electric field generator arranged to generate an electric field across the contacts of sufficient intensity to produce the desired effect to the ampullae of a shark that is sufficiently close to the antenna, f 00081 However, this type of shark repelling device tends to generate drag during use of the surfboard, which inhibits performance of the surfboard,.

SUMMARY

[0009] ^' According to a first, aspect, there is provided a fin for use in a e ondrichthyan repelling system, wherein at least a portion of the fin is an electrically conductive electrode for eiectrica! connection to a first terminal of an electric signal generator for generating an electric field about the fin that repels chondrichthyans.

[0010} in one embodiment, the entire Fin is the electrically conductive eiectrode.

[0011] In another embodiment, the entire surface of the fin is the electrically conductive electrode.

[0012] In one embodiment, the fin comprises an electrically conductive core comprising a sheet of electrically conductive material between two outer electrically non-conductive portions, at Ieast one of the outer electrically non-conductive portions having at least one aperture therein to expose a portion of the electrically conductive core to thereby provide the at least one electrically conductive electrode.

[0013] In one embodiment, the at least one of the outer electrically non-conductive portions has three apertures, thereb exposing three regions of the electrically conductive core.

[0014] In one embodiment, the fin further comprises a second electrically conductive eiectrode for electrical connection to a second terminal of the electric signal generator for generating, in use, the electric field about the fin. OOlS] in one embodiment, the fin further comprises at least a first fm electrical connector electricall connected to the at Ieast one electrically conductive electrode and accessible from external to the fin.

[0016] In one embodiment, the fin further comprise a second fin electrical connector connected to a. second electrically conductive electrode,

[0017] In one embodiment, the fin further comprises at least one fin connector for connecting the fin to a watereraft {0018] In one embodiment, the fin further comprises at least one electrically non-conductive base portion suppor ing the at least one electrically conductive electrode.

[O0I9J Its. one embodiment, the fin- further comprises a second electrically conductive electrode supported by the electrically non-conductive base portion.

[0020J According to a second aspect, there is provided a plug for connecting a fin according to the first aspect, to the body of a watercraft, the plug comprising;

a plug connector for engaging with a fin connector to thereby connect the fin to the body of the watercraft;

a fixing element for fixing the connected fin to the body of the watercraft; and at least one plug first electrical connector for providing an. electrical connection between a first terminal of an. electrical signal generator and the at least one electrically conductive electrode of the fin,

[00211 in one embodiment, the at least one plug first electrical connector is provided by the fixing element.

{0022} In one embodiment, the plu further comprises a plug second electrical connecto for providing an eleclTical connection between a second terminal of the electricai signal generator and the second electrically conductive electrode of the fin.

[00233 According to a third aspect, there is provided a chondrichthyan. repelling system comprising:

at least one fin according to the first aspect, for connection to a watercraft; and an electrical signal generator for connection to the at least one electrically conductive electrode of the at le ast one fin.

10024] In one embodiment, the chondrichthyan repelling system further comprises at least one plug according to the second aspect.

|0Q2S] According to a fourth as ect, there is provided a watercraft: comprising:

a watercraft body; and

at least one tin according to the first aspect.

[0026] In one embodiment,- the at least one fin is connected to the watercraft body by at least one plug according to the second aspect. [0027] In one embodiment, the watercraft further comprises an electric signal generator connected to the at least one electrically conductive electrode of the at least one fin via a respective at least one plug member.

[0028] In one embodiment, the watercraft comprises two tins accordin to the first aspect.

[0029] In one embodiment the watercraft comprises three fins according to the first aspect

[0030] In one embodiment, the watercraft is a surfboard and the electrical signal generator is housed within a kicker of the surfboard.

[0031] In one embodiment, the kicker comprises a fold-back flap for allowing access to the electrical signal generator within the kicker.

J0032] In one embodiment, the watercraft further comprises a grip pad and wherein at least one of a first signal generator connector and a second signal generator electrical connector is located beneath the grip pad,

J0033] In one embodiment, the watercraft further comprises a grip pad and at least one of a first signal generator connector and a second signal generator electrical connector is incorporated within the grip pad.

[0034] According to a. fifth aspect, there is provided a. kicker For a surfboard, the kicker comprising a cavity for receiving an electrical signal generator.

[0035] According to a sixth aspect, there is provided a grip pad tor a surfboard, the grip pad comprising one or more electrical conductors,

[0036] According to a seventh aspect, there is provided a ohondrichthyan repelling system for repelling chondrichlhyans from a watercraft having at least one fin, the repelling system comprising an electrical signal generator for connection to at least two electrodes and for generating electrical signals to cause the at least two electrodes to generate an electric field therebetween to, in use, repel the chondrichthyans, wherein at least one of the electrodes is provided by at least a portion of the at least one fin of the watercraft.

BRIEF DESCRIPTION OF DRAWINGS

[0037] Various embodiments will be described with reference to the accompanying drawings wherein: (6038) Figure i - shows one embodiment of a chondrichthyan repelling system according to one aspect;

[0039] Figure 2 - shows another embodiment of a chondrichthyan repelling system:

[0040J Figure 3 - shows another embodiment of a chondrichthyan repelling system;

[0041] Figure 4 - shows another embodiment of a chondrichthyan repelling system;

[0042] Figure 5 - shows another embodiment of a chondrichthyan repelling system;

[0043] Figure 6 - shows another embodiment of a chondrichthy an repelling system ;

[0044] Figure 7 - shows an embodiment of a chondrichthyan repelling system applied to a watercraft;

[0045] Figure SA - shows one embodiment for connecting an electrode to the electrical signal generator;

[0046] Figure SB - shows another embodiment for connecting an electrode to the electrical signal generator;

[0047] Figure 8C - shows another embodiment for connecting an electrode to the electrical signal generator;

[0048] Figure 8D - shows another embodiment for connecting an electrode to the electrical signal generator;

[0049] Figure 9 - shows an embodiment of a repelling system applied to a surfboard with three Fins;

[00501 Figure 1 Θ - shows a representation of an electric field generated about a surfboard with the repelling system;

[0051] Figure 1 1 - shows a cross sectional view of the arrangement of Figure 10; f 0052 J Figure 12 -shows a specific example of a repelling system with two Fins and plugs; [0053 J Figure 13 - shows an embodiment of the e iectrieal connectors between the electrodes and the signal generator;

[0054] Figure 14 - shows another embodiment of the eiectrieal connectors between the electrodes and the signal generator:

[0G55J Figure 1 S - shows an embodiment of a fin according to an aspect described herein;

[0056] Figure 1 6 - shows another embodiment of a fin;

[0OS7J Fi ure 17 - shows another embodiment of a fin;

[00583 Figure .1 SA - shows a left side view another embodiment of a fin;

[0059} Figure 1 SB - shows a right side view of the fin of Figure 1 8 A;

1.0060} Figure 1 - shows a cross sectional view of the fin of Figures 1 8A and Ϊ SB;

[0061] Figure 20 - shows another embodiment of a fin;

[0062] Figure 21 - shows another embodiment of a fin;

J0-063] Figure 22 - shows another embodiment of a fm;

[00643 Figure 2.3 A - shows another embodiment of a fin;

JG065} Figure 23 B ^■ - shows a com leted form of the fin of Figure 23 A;

}Q066| Figure 24 A - shows another embodiment of a. fin;

(0067J Figure 24B - shows a completed form of the Fm of Figure 24Λ;

[0068} Fi gure 25 - shows a schematic view of a fin plug;

[0069] Figure 26 - shows an embodiment of retro-fitting a surfboard to apply the repelling system;

[0079] Figure 27 - shows an embodiment of a surfboard with a housing for the signal generator;

J00711 Figure 28 - shows a flap on the housing for accessing the signal generator; [0072] Figure 29 A - shows an example of voltage pulses generated by the signal generator;

[0073] Figure 298 - shows another example of voltage pulses generated by the signal generator; and

[0074] Figure 29C - shows an example of voltage pulses generated by the signal generator.

DESCRIPTION OF EMBODIMENTS

[0075] Referring now to Figure 1 , there is shown a . chondriehthyan repelling system

according to one aspect described herein. At a broad level, the chondriehthyan repelling system 100 comprises at least one fin 0 for attachnierit to a watercraft (not shown). The fin 10 comprises at least one electrically conductive electrode 1 1 , The repelling system 100 also comprises an electrical signal generator 20 for electrical connection to the electrode 1 1 of the fin 10 and for generating electrical signals that will cause electrode 1 i to radiate a electric field that will in use. repel chondrschihyans as previously described.

[0076] it will he understood that numerous variations of this broad arrangement are possible, hi one embodiment, the repelling system Ϊ 00 comprises a fin 1 0 comprising two electrodes being first electrode \ 1 and second electrode 12. Each electrode 1 i and 1 2 is in use, electrically connected to a respective first terminal 23 and second terminal 24 of electric signal generator 20. In one such embodiment, the electrodes 1 1 and 12 are disposed on opposite sides of the fin 10 as shown in Figure 2 (electrode 12 is not visible in this view, being on the right side of the fm 10). In this embodiment, the repelling electric field is able to be generated using a single fin.

10077) in another embodiment as shown in Figure 3 , repelling system 1 0 comprises two fins 10 and 10', with fin 10 comprising first electrode 1 1 and fin 1 0' comprising second electrode 12. In this embodiment, the first electrode 1 1 of fin 10 is connected to the first output terminal 23 of signal generator 20 and the second electrode i 2 of fm 10' is connected to the second output terminal 24 of signal generator 20. In this view, signal generator 20 is shown to comprise a pulse generator 21 and a battery 22 for powering the pulse generator. The function of the pulse generator 21 wit! be described in more detai l below.

[0078] in another embodiment as shown in Figure 4, repelling system 1 00 comprises the signal gerterator 20 with two fins 0, 10' with each fin comprising two electrodes. Fin 10 has first electrode 1 1 and second electrode 12 and the second fin 10' has first electrode 1 1 ' and second electrode I V . In this arrangement, each of the first -electrodes 1 1 , 1 1 ' is connected to the first output termina 23 of signal S

generator 20 and each of the second electrodes 1 2, 12:' is connected to the second output terminal 24 of the signal generator 20.

[0079] i another embodiment as shown in Figure 5, repelling system 100 comprises three fins

10, 10' and 1 0" , with each fin comprising two electrodes 1 1 , 12: 1 ί \ 1 2' and I i " , 12" respectively. Each of the first electrodes 1 1, 1 1 * and 1 J " is connected to the first output terminal 23 of signal generator 20 and each of the second electrodes 12, 12'· and 12" is connected to the second output terminal 24 of the signal generator 20.

[0080] In yet another embodim nt, repelling system I 00 comprises three fins 10, 1 0' and i 0" but in this embodiment, each fin has only one electrode. In the arrangement shown in Figure 6, two of the fins 10 and i 0' ' has a first electrode 1 1 and ί 1 \ each connected to the first output terminal 23 of signal generator 20, while Fin 1 ' has a second electrode 12, connected to the second output terminal 24 of signal generator 20.

[0081 Any other suitable combinations are also possible, including the use of 4, 5, 6, 7, 8. 9 and

10 or more fins. In some embodiments, one or more of these fins will have one electrode and in ther embodiments, ne or more of these fins will have two electrodes. In other embodiments still, one or more fins will have 3, 4, 5, 6, 7, 8, 9, 1 0 or more electrodes. Any combination of the abo%'e is also possible.

[0082] I another aspect, the repelling system 1 00 is applied to a watercraft, to provide a chondricbthyan repelling field arosnd the watercraft. The repelling system 100 is applicable to any watercraft which has one or more fins, or to which one or more fins may be attached. The various embodiments described herein are described in the context of the watercraft being a surfboard, however any other watercraft such as a canoe, kayak, raft, boat, ship, ski board or other watercraft (even, if they do not ordinarily have a fin) can equally benefit from the various aspects described herein.

[0083] Figure 7 shows a general arrangement of a watercraft, in this embodiment, being a surfboard 30. Repelling system 100 is applied to the surfboard 30 as shown. In this embodiment, fin 10 is attached to the body 31 of surfboard 30 by any suitable means (some examples of which will be described in more detail below). Fin 1 supports at least first conductor 1 1 as previously described, in some embodiments, fin 10 is already incorporated into the surfboard 30 and is not detachable. Electrode 1 1 will then be applied to fin 10 by any suitable means.

[0084] Signal generator 20 is mounted to or in relation to. surfboard 3 by any suitable means, examples of which will be described in. more detail below, [OGSSj Figures 8A to 80 show different embodiments of connecting the electrodes (illustrated using first electrode 1 1.) to signal generator 20. In Figure 8A, signal generator 20 is located above the body 31 of surfboard 30 and fin 10 is located below the body 31 and under signal generator 20. In this arrangement an aperture or hole is provided through the body 31 through which an electrical connector 27 is provided to connect first electrode 1 i to the signal generator. In Figure SB, fin 10 fs attached to body 31 via a fin connecto 14 (described in more detail below), and electrical -connector 27 passes through a different region of the body 3 1. In Figure 8C, electrical connector 27 does not pass through the body 31 of the surfboard 30, but rather runs along its surface to connect first electrode 1 1 to signal generator 20. In Figure 8D, signal generator 20 is located underneath body 3 1 and connected to first electrode 1 1 via electrical connector 27 underneath the body 3 1 , In this arrangement, a suitable cover can be provided over signal generator 20 to reduce any detrimental hydrodynamic effects of having the signal generator 20 located underneath the body 3 1. 0G86J Figure 9 shows an embodiment of watercraft or surfboard 30 with three fins 1 0, 10' and

30", connected to signal generator 20 (housed within a waterproof housing 32), and connected to respective electrodes (not visible in this view) by electrical connectors 27.

[0087] Figure 10 shows another embodiment of surfboard 30 with two fins 10 and 10' and shows a representation of the electric field 200 generated between the two electrodes (not visible in this view) on the fins 10 and i 0 ^s , with the water surrounding the fins 10 and 10 ¹ acting as the conductive medium, when in use, f 0O88J Figure. S 1 shows a cross section of the surfboard 30 of Figure 10 along the lines A-A showing the connection of the fins 10 and. 10' to the body 3 1 of surfboard 30. Also shown is kicker 32 acting as the housing for signal generator 20 and grip pad 33 which can be used to cover or incorporate the electrical connectors 27 to connect signal generator 20 to the electrodes on the fins as described above.

\QQB9] Figure i 2 shows an example embodiment of a specific implementation for connection of fins 10 and J O ^* to respective terminals of the signal generator 20. in this exam pie, fins 10 and 10' are connected via electrical connectors 27 and via a conductive path provided by fin plugs 4 as will be described in more detail farther below,

[0090] Figure 13 shows a more detailed arrangement of an embodiment of connecting the electrodes to the signal generator 20, In this embodiment, electrical connector 27 described previously, is provided, by three different electrical connectors along the path from the signal generator 20 to the electrode 1 1 or 12. [0691] As seen in Figure 13, first electrode 1 1 on fin 10 is connected to signal generator 20 via first signal generator electrical connector 25. connected to first output terminal 23 of the signal generator 20 and. via first plug elecirical connector 44 provided by a conductive element within plug 40, and via first fin electrica! connector 15 associated with or incorporated within fin 10,

[0692] Second electrode 1 2 on fin 10 is connected to signal generator 20 via second signal generator electrical connector 26, connected to second output terminal 24 of the signal generator 20 and via second plug electrica! connector 45 provided by a conductive element within plug 40, and via second fin electrical connector 16 associated with or incorporated with in fin 10.

[0093] Figure 14 shows another embodiment with a similar electrical connection arrangement, in which there are two fins 10 and 10', each with a single electrode 1 1 and 12 respectively. In this arrangement, first electrode i 1 on fin 10 is connected to signal generator 20 via first signal generator electrical connector 25, connected to first output terminal 23 of the signal generator 20 and via first plug electrical connector 44 provided by a conductive element within plug 40, and via first fin electrical connector 15 associated. with or incorporated within fin 10.

[0094] Second electrode 12 on fin 10' is connected to signal generator 20 via second signal generator elecirical connector 26, connected to second output, terminal 24 of the signal generator 20 and via second plug electrical connector 45 provided by a conductive element within plug 40, and via second fin electrica! connector 1 6 associated with or incorporated within fin 10',

[0095] In other embodiments, there may be no, or only one or two parts to electrical connector

27, For example, where there is no plug 40, there will be no plug electrical connector 44,45. In embodiments where fin connector 14 extends to make direct contact with output terminals 23, 24 of signal generator 20, and is itself a pari of the electrode 1 1 or 1 2, there may be no separate signal generator electrical connector 25, 26, no separate plug electrical connector and no separate fin electrical connector 15, 16.

[0096] In the case where the entire fin 1 0 acts as the electrode, and is connected to surfboard 0 via plug 40, there may he no separate fin electrical connector,

[0997] According to another aspect described herein, there is provided a fin for use in a cbondrichtbyan repelling system, wherein at least a portion of the fin is an electrically conductive electrode for electrical connection to a first output terminal of an electrical signal generator for generating an electric field about the fin that repels cbcmdrkhtflyans. Figure 1 5 shows a broad embodiment of this aspect, showing fin 10 with a single electrode 1 1. In Figure 1 6, fm 1 0 is shown made entirely from an electrically conductive material such as stainless steel or aluminium. In this embodiment, the entire fin 10 acts as the electrode 1 1 . lit the embodiment of Figure 17, the fin 10 has a surface coating or sheet applied to an electrically non-conductive substrate or base portion to thereby provide the fra 10 whose entire surface forms electrode 1 1.

{00981 Figures 18A and 1 8B show opposite sides of the same fin 10, showing that the fin 10 can support two electrodes to generate the electric field from a single fin. in this arrangement, first electrode 1 1 and second electrode 12 are supported by an electrically non-conductive substrate or base portion 13.

{0099} Figure 1 shows a cross sectional view of the fin 10 of Figure 1 SB along the line A*A'.

As can be seen in this figure, first electrode 1 1 and second electrode 12 are Supported by non-conductive substrate or base portion 1 3. Substrate or base portion ! 3 can be made of any suitable materia! such as fiberglass or plastic, or any suitable composite that may be used to construct surfboards,

{00100} Another embodiment of fin 10 is shown in Figure 20. In this embodiment, a conductive insert is provided for the leading edge fm tab where the grub screw of a plug (see farther below) will make contact upon attachment of the tin 10 to the body 31 , to thereby provide an electrical connection and provide the electrode 1 1 . in this embodiment, it will be appreciated that the fin connector 1 acts as the first fits electrical connector 15 to provide an electrical connection to the first electrode 1 \ . fOOl ll Fignre ll shows yet another embodiment of fin 10 with electrode Π , in which a stainless steel leading edge is blended into the traditionally molded fin 1 0 to provide electrode 1 1 .

[00102} fn another embodiment of fm 10, as shown in Figure 22, first fin electrical connector 1 5 is provided by a metal insert shaped to conform to the shape of an existing fm design, and to receive the grub screw of plug 40 as described further below. When in place, the metal insert makes electrical contact with first electrode 1 1 at the leading edge of fin 10.

{00103] In another embodiment of fin 10 as shown in Figures 23A and 23 EL sheets of electrically conductive inateriai with bent tabs to receive the fin connectors 1 4, are placed on top of the fin 10 to be in electrical contact with first electrode 1 1 and second electrode 12 to form first fin electrical connector 1 5 and second fin electrical connector 16. As seen in Figure 23B, when in place first fin electrical connector 1 S and second fin electrical connector 16 are received in plugs 40 to provide an electrical path to the signal generator (not shown) through plugs 40. f 00104] In yet another embodiment as shown in Figures 24A and 24B , fm 10 is constructed with first electrode 1 1 provided as a flat sheet of electrically conductive material snch as stainless steel to provide an electrically conductive core 1 7, with tabs to provide fin connectors 14 to connect to a fin plug (not shown). Two outer electrically non-conductive portions 1 8 with at least one aperture 1 cover the core 17. The region of the- core 17 under the aperture 19 is exposed to the surrounding water in use, thereby providing electrode 1 1 , The outer electrically non-conductive portions 18 are affixed to the core 1 7 by any suitable means including gluing or molding.

|00105] In some embodiments, there is only one aperture between both electrically non- conductive portions 18. In other embodiments, each electrically non-conductive portion has an aperture, and in other embodiments, each electrically non-conductive portion has 2, 3, 4, 5, 6. 7, 8, 9, 10 or more apertures, or combinations of the above.

[00106] The finished fin 10 of this embodiment is shown in Figure 24B.

{00107} In a further embodiment, a fin 10 of the form shown in Figures 24A and 24B can be formed in which there are two electrodes 1 1 and 12 provided by respective electrically conductive sheets forming respective cores. These sheets will be separated by a further non-conductive substrate or base portion 13 with non-conductive portions 1 8 with respective apertures covering the electrically conductive cores 17. In this arrangement a single fin 10 will have two electrodes, first electrode 1 1 and second electrode 12.

JOOlOSt ft will be appreciated that the electricall conductive material used to provide the electrodes can be any suitable material, including metal, stainless steel, aluminium, alloys and othe materials such as gra hene and carbon fibre.

{00109] In the case where fin 10 is detachable from waiercraft 30. fin 10 can be attached to water-craft 30 by any suitable means. One common means is to use a plug 40 as previously described. One form of plug 40 is shown schematically in Figure 25. In this embodiment, plug 40 comprises a plug connector 41 (which could be a slot or a protrusion) for engaging with a fin connector 14 (not shown) (which could also be a reciprocal protrusion or slot) to thereby connect the fin 10 to the body 31 of the waiercraft 30; Plug 40 also has a fixing element 42 (not shown) (for example a screw (known as a grub screw) or a pin) for fixing the connected fi to the body 31 of the waiercraft 30, and at least one plug first electrical connector 44 for providing an electrical connection between a first terminal of the electrical signal generator (not shown) and the at least one electrically conductive electrode of the fin 10 (not shown). In some embodiments the first plug connector is provided by the fixing element such as the scre or pin. In other embodiments, the first plug connector is provided by an electrically conductive wire 44 as shown in the cutaway portion 43. fOOllO] In the embodiment shown in Figure 25, fixing element 42 is received in plug fixing aperture 46, {00111] In some embodiments, plug 40 also comprises a second plug electrical connector 45 (not shown in this view) to ailow connection to a second electrode 12.

[00112] Figure 26 shows one embodiment of an arrangement for retro-fitting a surfboard 30 with the repelling system described herein. In one embodiment the fibreglass top deck of the surfboard 30 is pierced above the existing pi«g 40 to expose a plastic scre that is in place to seal the thread made to receive the plug 40 from the resin of the surfboard body 31 , The plastic screw is removed and a conductive screw 34 is inserted into the fin plug thread in which the piastic screw had been screwed. This now forms a conductive pathway from the top of the surfboard to the metal plug 40 and to the grub screw 42 which will itself make electrical contact with the electrode 1 1 of the fin 1.0 (not shown) when in place.

{00113 j An electr ically conductive wire 35 can then be attached to the top of the electrically conductive screw 34 to together, form the first or second signal generator electrical connector 25, 26.

{00114] Figure 27 shows an embodiment of a waterefaft 30 (in tins case a surfboard) comprising a body 1 , at least one fin 10 and a housing 32 for the electrical signal generator {not shown). The housing in this embodiment is a kicker, which is provided on a surfboard to provide a footing for the surfer when riding the surfboard.

[00115] As shown in Figure 2 . a flap 36 is provided to allow access to a cavity within kicker 32 in which the electrical signal generator 20 (not shown) can be housed. The output terminals 23, 24 of electrical signal generator 20 can then be connected to the first, and second electrodes I K 12 on the one or more fins 10 by any suitable means as previously described,

{00116] Any suitable electrical signal generator can be used, such that it will generate electrical signals to a first electrode i 1 and a second electrode ] 2 that will radiate an electric field therebetween that will repel chondrichthyans. An example of one such suitable signal generator is described in detail in US patent No 5.366.643 hereby incorporated by reference in its entirety,

[00117] in an example of suitable signals generated, the voltage pulses generated may have a duration of between about 0.1 ms and 200ms. a frequency between about 1 Hz and 60Hz, a pulse rise time that is less than about 0.001 μδ and a voltage magnitude between about 24V and 72V,

[00118] In some embodiments, the pulses are produced in pulse trains, with each pulse train comprising several pulses and each pulse having a duration of between about 0.1 ms and 2 ms, a spacing between adjacent pulses in a pulse train of between about 1 ms and 30ms, and the pulse trains repeating at a period of between about 100ms and 10:00ms. [00119] Example voltage pulses 50, 52 produced by the electrical signal generator 20 are shown in Figure 29 A. In this example, the pulses are substantially square type with alternating positive and negative pulses 50, 52.

[001201 Since the system is often operated during use in sea water that has a lower electrical resistance than fresh water, the signal generator 20 may be arranged to limit the current produced by the signal generator 20 and thereby protect the circuitry of the signal generator 20.

[00121] Alternative example voltage pulses 54, 56 produced by the signal generator 20 are shown in Figure 29B. In this example, the pulses are substantially saw tooth shaped. With this arrangement, a lower amount of energy is imparted to the electric field generated in the water than the voltage pulses 50, 52 shown in Figure 29A.

[00122] In a particular example shown in Figure 29G, a pulse waveform that includes alternating positive 60 and negative 62 pulse trains is shown. Each pulse train includes 3 substantially square wave pulses 64, 66, each pulse train is repeated every 200ms. Also, each pulse 64, 66 has a duration of about 0.5ms, is repeated every 20ms and has a magnitude of about 48V,

[00123] in a broad sense, the above has described a chondrichthyan repelling system for repelling chondrichthyans from a watercraft having at least one fin, the repelling system comprising an electrical signal generator for connection to at least two electrodes and for generating electrical signals to cause the at least two electrodes to generate an electric field therebetween to, in use, repel the chondrichthyans, wherein at least one of the electrodes is provided by at least a portion of the at least one fin of the watercraft.

[00124] Throughout the specification and the claims that follow, unless the context requires otherwise, the words "comprise" and "include" and variations such as "comprising" and "including" will be understood to imply the inclusion of a stated integer or group of integers, but not tire excl usion of any other integer or group of integers.

[00125] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms pari of the common general knowledge.

[00126] It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the invention ts not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims.