Abstract:
In abstract this invention is a pressure and water sealed unit small enough to be worn by a swimmer. It contains a rechargeable battery, control interface logic, digital signal generation, and amplification circuitry. It uses a ground balanced electrode system to produce electric fields in the very low impedance environment of water. These fields are organized into patterns called words. These words are presented in a hierarchal pseudo random manner to prevent target organisms from learning and adapting to them. The presentation of these words is controlled by upgradable programing stored within memory. The words evoke central nervous system (CNS) responses which result in sharks leaving the area of operation. These words represent stimuli of predators, navigation signals, noxious events, CNS interference patterns, and other sequences found to repel sharks from the protected area. Reprogrammability allows upgrades to newer sequences. The amplifier uses switching stages to multiply the battery voltage up to about one thousand times. An inversion unit provides for positive and negative signals. The switching circuit is logic level and pulse width modulation controlled. The switching typology permits micro miniaturization and efficient power consumption prolonging battery life. The unit has no user adjustable parameters except for go no-go control and shark alarm. Unit and battery status is indicated by flashing light signals. Electrode typology generates a spherical electric wave propagation pattern in water. A recharging cradle projects magnetic energy into the unit providing for automatic battery recharging and conditioning without electrical connections exposed to an aqueous environment.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Provisional Patent Application Ser. No. 61/400,894, filed Aug. 3, 2010 by the present inventor. 
     
    
     FEDERALLY SPONSORED RESEARCH 
       [0002]    Not applicable. 
       SEQUENCE LISTING OR PROGRAM 
       [0003]    Not presented in this application. 
       BACKGROUND 
       [0004]    1. Field of Invention 
         [0005]    The present invention relates to an electronic device that can be worn by a person to safely repel sharks from the area. 
         [0006]    2. Description of Prior Art 
         [0007]    Inventors have received many patents for devices which operate as a shark repellant. These devices use chemicals, electric and magnetic fields, and or acoustic signals. All approaches share some common issues. Most importantly, they almost all generate a repeating signal pattern whether it be an alternating current (AC), a direct current (DC) electric field, a magnetic field, or a pattern of acoustic stimuli applied to an aquatic environment via a transducer. The United States Navy also did research in this area. They even used small air bubbles released into the aquatic environment. When a stimulus was found that was effective, the approach eventually failed anyway, since the sharks learned and adapted to the stimulus pattern. This apparatus takes a new approach by presenting a random sequence of electrical stimuli of sufficient variability to make adaptation unlikely, or impossible. 
       BACKGROUND OF THE INVENTION 
       [0008]    The South African government developed and put on the market a device called Shark Shield. I quote from this companies web page at http://www.sharkshield.com/Content/Technology which is hereby incorporated as reference. “Predatory sharks have small gel filled sacs knows as ‘Ampullae of Lorenzini’ on their snouts. They use these short range sensors when feeding or searching for food. Shark Shield is a three-dimensional electrical wave form which creates an unpleasant sensation impacting the shark&#39;s ‘Ampullae of Lorenzini’. When the shark comes into proximity of the electrical wave form (around 8 meters in diameter) it experiences non-damaging but uncontrollable muscular spasms causing it to flee the area. The field is projected from the unit by two electrodes, which create an elliptical field that surrounds the user. Both electrodes must be immersed in the water for the field to be created. The electrode configuration depends on the model of the Shark Shield unit. From testing, the closer the shark is to the Shark Shield field, the more spasms occur in the sharks&#39; snouts. This becomes intolerable and the shark then veers away, and usually doesn&#39;t return.” 
         [0009]    The above device consists of an electronic signal source to which a bipolar radiator is attached. Controls adjust the operational parameters. The bipolar radiator resembles a triaxial cable about six feet long. Near the unit, the outermost braid is exposed for one to two feet. The next section is insulated. The last section has an inner braid layer exposed. It appears most likely that the electrical signal is applied across these two exposed sections, and that these sections are insulated from each other. Swimmers, divers, surfers using these devices either have an approximately six foot cable extending into the water or two separate approximately three foot long cable radiators. 
         [0010]    Another inventor attempted to develop a “stun gun” like device. His claim was that stimulation of the shark&#39;s Ampullae of Lorenzini would result in irritating muscle spasms like those claimed by Shark Shield. 
         [0011]    After much analysis of research literature and analysis of shark nervous system anatomy, I have concluded that both of these approaches are inappropriate. They may get some response, but I believe these inventions do not adequately address the response characteristics of the shark&#39;s nervous system. 
         [0012]    These inventions follow the approach of causing irritating muscle stimulation as an operational means. Shark Shield implies that the induced muscle contractions are mediated via the Ampullae of Lorenzini and possibly through the central nervous system. They go on to state that these Ampullae are short range sensors used when feeding or searching for food. The second inventor claimed direct transcutaneous muscle stimulation as a mode of operation. Both approaches indicate a lack of understanding of the current literature on the function of these sensors. 
         [0013]    I have studied some of the foundational research articles on this subject. They include: “The Response of the Ampullae of Lorenzini of Elasmobranches to Electrical Stimulation” by R. W. Murray in J. Exp. Biol. (1962), 39, pages 119 to 128. “The Response of the Ampullae of Lorenzini of Elasmobranches to Mechanical Stimulation” by R. W. Murray in J. Exp. Biol. (1960), 37, pages 417 to 424. “Mode of Operation of Ampullae of Lorenzini of the Skate, Raja” by S. Obara and M. V. L. Bennett in The Journal of General Physiology (1972), 60, pages 534 to 557. “Electroreception in Juvenile Scalloped Hammerhead and Sandbar Sharks” by Stephen M. Kajiura and Kim N. Holland” in The Journal of Experimental Biology (2002), 205, pages 3609 to 3621. The above four articles are cited and incorporated herein as reference. 
         [0014]    Review of these above referenced articles and study of others has led me to very important understandings of the physiological response of the shark to electrical stimuli as relevant to developing an electric shark repellant device. One very important conclusion is that the muscle spasms induced in the shark by the above devices are at most minimally relevant artifacts of central nervous system (CNS) responses to these stimuli. A CNS mediated behavioral response is what is most important, relevant, and needed for this application. I emphasize, it is not the muscle spasms which make the shark leave the area, but it is the shark&#39;s CNS interpretation and behavioral response to these various stimuli that really matters. 
         [0015]    On the surface of the shark&#39;s body, primarily in the head region, are hundreds of pores which open to the aquatic environment. These are connected by canals of varying lengths and orientations to spherical sense organs called ampullae. Each ampullae is lined with hundreds of receptor cells. The canals and the central lumen of the ampullae are filled with a conductive mucoprotien gel. The impedance at the canal opening is that of a dead short at about zero ohms. As the canal proceeds to the Ampullae, its internal impedance rises to very high levels. The walls of the canals are of very high resistance. The canals serve as an impedance matching device between the zero impedance of the aquatic environment to that of the high impedance of the lumen of the ampullae. The canals also act as rapid cut off low pass frequency filters. Their conductivity is such that there is negligible decrement of DC potentials. Canals of differing lengths result in differing voltage response characteristics. Multiple receptor cells synapse with a given nerve fiber facilitating asynchronous response to given receptor cell potentials. Only the luminal surface of the receptor cell depolarizes in response to negative potentials within the ampullary lumen. However, the serosal surface can depolarize in response to high positive potentials within the lumen due to direct charge transmission. The result is a very complex and anomalous response of this system. 
         [0016]    The result is that this system allows the shark to have a “three dimensional electrical vision.” At small electric potentials, at times approaching 1-6×10 −9  volts, this system is responsive to negative potentials. In this case negative potentials stimulate nerve firing and positive potentials inhibit the nervous response. Paradoxically, at much higher potentials, the system has an opposite response. At higher potentials, positive voltages become stimulatory with negative potentials becoming inhibitory. The latency and refractory periods also change with these differing voltage levels. 
         [0017]    Sharks have only passive electroreception. Electric fish have both. With active electroreception, the fish generate a high voltage potential which produces an electric field radiating outward from the fish. The fish then “listens” to disturbances in the propagation of this field similar to how sonar works. It allows “vision” in total darkness. These fish can very accurately sense objects around them. Using active electroreception, they can identify other like species and even identify their sex. Study of the nervous system innervation reveals that these systems may have as much, or more information resolution as the fishes vision. 
         [0018]    Sharks have a very well developed innervation of this sensory system. Its resolution may very well exceed the shark&#39;s visual acuity. When a shark closes in on the bite, it actually closes its eyes for several seconds before the bite. It is as if the shark depends on a superior resolving power of electroreception compared with normal vision. Sharks also use the sense for long range navigation. They actually sense minute electric fields generated by the earth&#39;s magnetic field in water. 
         [0019]    This system has obvious near and far field responses. The Shark Shield Company of above obviously does not fully understand this physiology. These are much more than short range sensors. It is obvious they have differing and often paradoxical responses to stimuli from differing ranges. It is obvious to me that the sharks are sensing many different stimuli patterns which I will call words. These words are electrical signals of varying frequencies, voltage patterns, phase shifts, decay times, harmonic relationships, and other characteristics. Sharks are able to discern the three dimensional angular direction and relative distance to the source of some of these signals. They are able to accurately identify the source of the signal emitter for certain word patterns. For example, a dead, decaying fish buried in sand during various stages of decomposition generates DC electric fields which sharks are able to identify. They are able to accurately swim to the location and bite into the sand and retrieve the fish. Battery powered dead fish simulators have also been retrieved by sharks in experiments. 
         [0020]    Struggling, scared, and or injured fish radiate electric fields as a result of numerous muscle contractions. Sharks can sense these very weak fields at long distances and then target and hone in on these fish. The voltages of these fields at significant distances must approach the sharks threshold of voltage sensitivity. These various electric words evoke what I will call images in the shark&#39;s CNS. The sharks identify these images as dead fish, other species, navigation information, and predators. These word images may even be a communication means. These electric field image invoking words are very complex. They are both learned and built in patterned responses of sharks. Research has shown that the sharks can and do learn and adapt to the simple images and words produced by the electric repellant device approaches used to date. 
         [0021]    This invention is a new and innovative approach to electric shark repellant design. It is able to generate many complex voltage waveforms and do so in a random manner. It is controlled by programming, so that these electric word patterns can be improved based on research data. It is able to produce both positive and negative electric fields allowing the use of near and far field words. It allows the words to be multi-factorial. Words can be generated representing many different types of repellant stimuli. They can represent predators such as ocra whales. They can be various noxious stimuli. They can confuse and interfere with navigation sensations. They can cause operational malfunctions within the CNS. For example, upon reception of certain voltage patterns, oscillations are produced within nerve responses. Word patterns harmonically related to such known oscillations may very well affect proper function of the CNS resulting in confusion, disorientation, and flight. Words may cause sensor overload. This would be a near field effect. It would be like flashing a bright flash bulb in someone&#39;s eyes causing temporary loss of sight. Such electric field words could temporary blind the shark to its electroreception sensations. The shark for a few second closes its eyes during attack indicating the importance of the relative value of electroreception sensation compared with visual information. Such a blanking out of this sensation would lead to abortion of attack and most likely result in flight. Other words not yet conceived will be discovered by research and will be able to be produced by this device by program upgrades. 
       SUMMARY 
       [0022]    This invention is a multi-factorial electric field pattern generator. It consists of a programmable digital circuit driving a bipolar switching amplifier. It also includes a battery, power control system, battery recharging system and user interface system. It is designed to be easy and foolproof in operation. It is small, light weight, and hermetically sealed in ways appropriate for a marine environment. It is reprogrammable, allowing for upgrading of the unit. It has the capacity to produce hundreds, or even thousands of electric words as per its programming. Most significantly, this invention will present such words in a pseudo random sequence in order to avert adaptation by the shark to a constant stimulus pattern. It is able to produce electric voltages of both polarities into the low kilovolt range. It includes a ground balance system which allows it to match its output to the approximately zero impedance of the marine environment. Its switching amplifier uses high switching frequencies and paired stages in order to permit micro miniaturization of its components. It has an electrode arrangement which generates an electric field from a point like source. It can be a small device, like a watch which can be worn by swimmers, divers, surfers, and others exposed to sharks. It does not have an extended electrode system like an antenna The driven electrodes are within the sealed unit and are protected from the wearer by their internal location, thus preventing shock. It is designed to be energy efficient. It is designed for foolproof operation. There is a single user control which wakes the unit up from sleep mode. A single optical mechanism then flashes a predetermined sequence of colored lights indicating battery charge. Periodic flashes of light from this system indicate unit operation. A water sense switch puts the unit into active mode when the wearer enters the water. On leaving the water, the unit goes into a non active, but on mode. It restarts this cycle when put back into the water. If it is not put back into the water within a predetermined period of time, it goes into sleep mode. It has a charger cradle which allows recharging of the battery without direct exposure of electrical terminals to a marine environment. It has built in battery management and recharging circuits. It is a sealed unit, water and pressure resistant for use to depths needed by divers. It does have a pressure sealed access hatch whereby the rechargeable battery can be replaced and connections for reprogramming can be accessed. With the exception of this service access, the remaining portions of the unit are totally sealed and not serviceable. Electrodes interfacing with water are of materials with coatings appropriate for a marine environment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1 : Block diagram of the apparatus and its power supply. 
           [0024]      FIG. 2 : Schematic of bipolar switching supply with optional clamp circuit. 
           [0025]      FIG. 3 : Cross sectional representation of a complete apparatus and its power supply. 
       
    
    
     REFERENCE NUMERALS IN DRAWINGS 
       [0000]    
       
           10 : waterproof sealed case. 
           11 : waterproof sealed service access hatch. 
           12 : screw. 
           13 : screw sleeve. 
           14 : screw anchor. 
           15 : gasket. 
           16 : o ring seal. 
           17 : charger cradle. 
           18 : light pipe. 
           19 : water and pressure proof momentary contact switch activator. 
           20 : water sense switch. 
           21 : ground balance electrode pore. 
           22 : output electrode exposure slat. 
           23 : ground balance electrode. 
           24 : output electrode. 
           25 : wall outlet power plug. 
           26 : wire. 
           27 : fuse. 
           28 : metal oxide varistor. 
           29 : line filter capacitor. 
           30 : power transformer primary. 
           31 : magnetic circuit. 
           32 : power transformer secondary. 
           33 : rechargeable battery. 
           34 : contact spring. 
           35 : contact clip. 
           36 : in and out port connection. 
           37 : internal ground reference point. 
           38 : printed circuit board power connection point. 
           39 : momentary contact switch. 
           40 : light emitting diode. 
           41 : middle printed circuit board. 
           42 : input and output controller. 
           43 : programmable memory. 
           44 : read only memory. 
           45 : memory controller. 
           46 : operation control logic and control interface. 
           47 : dock. 
           48 : central processing and control logic unit. 
           49 : output register. 
           50 : output buffer. 
           51 : upper printed circuit board. 
           52 : switching amplifier. 
           53 : ground balance resistor. 
           54 : output bleeder resistor. 
           55 : output filter capacitor. 
           56 : lower printed circuit board. 
           57 : power controller. 
           58 : charging circuit. 
           59 : bridge rectifier. 
           60 : attachment frame. 
           61 : spacer. 
           62 : second injection molded waterproof sealed casing. 
           63 : first multiplication inductor. 
           64 : second multiplication inductor. 
           65 : third multiplication inductor. 
           66 : inversion inductor. 
           67 : inverse third multiplication inductor. 
           68 : negative power connection. 
           69 : positive power connection. 
           70 : first multiplication enhancement mode field effect transistor. 
           71 : second multiplication enhancement mode field effect transistor. 
           72 : third multiplication enhancement mode field effect transistor. 
           73 : inversion enhancement mode field effect transistor. 
           74 : inverse third multiplication enhancement mode field effect transistor. 
           75 : gate enhancement mode field effect transistor. 
           76 : clamp enhancement mode field effect transistor. 
           77 : first multiplication catch diode. 
           78 : second multiplication catch diode. 
           79 : third multiplication catch diode. 
           80 : steering diode. 
           81 : first multiplication bleeder resistor. 
           82 : second multiplication bleeder resistor. 
           83 : inversion bleeder resistor. 
           84 : clamp resistor. 
           85 : and logic gate. 
           86 : logic inverter. 
           87 : first multiplication filter capacitor. 
           88 : second multiplication filter capacitor. 
           89 : inversion filter capacitor. 
           90 : optional clamp circuit. 
           91 : optional wire connection to optional clamp circuit. 
           92 : inversion catch diode. 
           93 : bus connection. 
       
     
       OBJECTS AND ADVANTAGES 
       [0000]    
       
         
           
             Programable. Operation controlled by program stored in re-programmable memory which can be upgraded to adapt unit to newer program sequences. This allows unit to generate newly developed words as they become evident through ongoing research. 
             Sealed. The unit is water and pressure sealed. The battery and programing port are accessible through a removable pressure and water sealed hatch. The remaining portions of the unit, including parts internal to this service hatch are totally encapsulated and sealed against water and sufficient pressure to accommodate most divers. This increases reliability, but makes the remaining part of the unit non serviceable. 
             High efficiency. A bipolar switching amplifier produces various voltage multiplication and inversion ratios with high efficiency within a small space. 
             High switching frequency. This along with paralleled initial voltage multipliers leads to micro miniaturization of components, especially capacitors and inductors. 
             High resolution. The clock frequency of the digital portion is at least twenty times the switching frequency of the amplifier. This imparts high resolution to the electric words produced. 
             Easy, foolproof operation. A single wake up from sleep switch is accessible to the operator. A single optical indicator registers battery condition and operation of the unit. A water sense switch activates the unit upon water entry, and deactivates the unit upon leaving the water. This conserves battery life. 
             Non user adjustable. There are no user adjustable device operational parameters. The user only has control over waking the unit from sleep, monitoring its battery condition, monitoring that the unit is on, and recharging the battery. Other units have controls in which the user can adjust operational parameters. Most users lack sufficient knowledge to make such parameter adjustments to such a device. Such control must be incorporated by design, so that the user may not make such adjustments as to possibly make the unit ineffective. This would result in a hazardous situation for the user. The user must only have go, no-go control over the unit. 
             Randomness. Previous units produced a fixed and or user selectable patterns of stimuli. This invention&#39;s most important development is its ability to produce pseudo random stimuli patterns. This occurs on several levels. The unit is capable of producing differing categories of stimuli. These include representations of predators, noxious stimuli, navigation sense interference, sensor overload, and interference with CNS functioning. The presentation of these categories of stimuli will be done in a pseudo random manner. The various word images within each category of stimulus will also be pseudo randomly presented. Characteristics of each stimuli will also be randomly presented. For example, say the stimulus representing an ocra whale predator to sharks is presented. It will be presented in proximity to the shark in various manners such as its three dimensional and distance relationship from the shark. These variables will then be also presented in a random manner. The result is a hierarchy of pseudo randomness which can lead to CNS confusion, overload, and malfunction. This would interfere with the shark&#39;s ability to accurately sense the location of a target and most likely would result in flight from the area, to an area that is “less confusing.” 
             Adaptability for other uses. This invention will trigger a family of devices for many different usage&#39;s. Such an invention can be adapted to present pseudo random signals using other modalities such as magnetic fields, electromagnetic fields, acoustic fields, and optical fields to act as repellants to other species such as birds, bears, rodents, and insects. Such devices exist, but again usually present repetitive stimuli which the target organisms adapt to and learn. Additionally, a higher powered version could be adapted to a ships hull to present signals which would cause dolphins, whales and other endangered species to get out of harm&#39;s way from water vessels. This would help protect them from injury. Additionally, the navy could use an adaptation of this invention to cause sea creatures to leave an area which is to be subjected to high level sonar signals. 
             Magnetic charging circuit. The unit sits in a charging cradle which plugs into a wall outlet. This cradle includes the primary winding of the power transformer. The magnetic circuit of this transformer is brought close to the surface of where the unit sits within this cradle. The secondary winding of the transformer is encapsulated either in the unit or in the access hatch. The unit is so designed that when placed in this cradle, the magnetic circuit of the secondary winding makes alignment with the magnetic circuit of the primary. The only gaps in this circuit are those presented by the case of the unit or its cap and the coating of the primary magnetic circuit. Flux loss across this gap may be compensated by design of such a system. Inefficiencies of transfer can be tolerated since that this unit is powered by the electric utility. The charging current is quite low, also making inefficiency losses tolerable. What is gained is a unit that has no unnecessary electrical connections exposed to a marine environment. Operation of the battery charger and conditioner is automatically controlled upon the secondary receiving magnetic energy from the primary circuit. 
           
         
       
     
       DETAILED DESCRIPTION OF THE INVENTION 
       [0120]    This invention is enclosed in a waterproof sealed case  10 . This case contains most of the electronics and is totally encapsulated and pressure resistant to permit operation in a marine environment to most depths used by divers. The encapsulated components are non serviceable. The case includes an attachment frame  60  which allows dependable and secure attachment to an attachment means in which mechanical stress is distributed through the casing. This encapsulated case consists of two primary castings. Waterproof sealed case  10  forms the primary casting. Internal parts as shown in the figures are mounted therein. Appropriate spacer(s)  61  are used in this assembly. Once all parts to be encapsulated are mounted, the second injection molded waterproof sealed casing  62  is applied in a manner in which creates a single encapsulated, sealed, and pressure resistant module as consistent with standards of those trained in this art. 
         [0121]    Attaching to this primary case is waterproof sealed service access hatch  11 . It is fastened with screw(s)  12 , screw sleeve(s)  13 , screw anchor(s) 14 , o ring seal (s) 16 , and gasket  15 . 
         [0122]    Openings to this case include ground balance electrode pore(s)  21 , and output electrode exposure slat(s)  22 . Protruding through the case in a sealed manner are light pipe  18 , water and pressure proof momentary contact switch activator  19 , and the opening to water sense switch  20 . Cast integrally in place with this structure are ground balance electrode  23  and output electrode  24 . This casting is so constructed to sit and appropriately align within the charger cradle  17 . An enclosed space within this casting assembly holds rechargeable battery  33 , gasket  15 , and in and out port connection  36 . The remaining operational electronic components of this casting are integrally contained within waterproof sealed case  10 , waterproof sealed service access hatch  11 , and charger cradle  17 . With exception are power wire(s)  26  and wall outlet power plug  25 . These components are assembled as shown in the drawings using standard construction practice of those trained in these arts. 
         [0123]    Electronically, this invention consists of three main parts and related circuits. Middle printed circuit board  41  contains most of the digital circuitry. This comprises the user interface and control logic, clocks, memory units, buffers, input and output devices and the ancillary switches and indicators. Momentary contact switch  39  initiates activation of the unit from sleep mode and water sense switch  20  activates pattern generation upon water entry. On leaving the water the unit then goes into a standby mode in order to conserve battery charge. Operational status is indicated by red and green light emitting diode(s)  40  whose signals are seen via light pipe  18 . Upper printed circuit board  51  has switching amplifier  52  along with the output filter circuit. Lower printed circuit board  56  has the power management circuits power controller  57  and charging circuit  58 . The charging cradle has the remaining charger circuit components. 
         [0124]    These components are assembled as represented in  FIGS. 1 and 3 . Attachment frame  60  is cast integrally with the case and provides a hardened point of attachment which distributes loading throughout the case. The active end of the unit has slats allowing water contact with circular output electrode  24 . Surrounding this within a predetermined alignment is the ground balance electrode  23 . This is a circular ring surrounding the output electrode, and it makes water contact via ground balance electrode pore(s)  21 .  FIG. 3  shows this ring higher up in the casing with respect to the output electrode. This is a schematic representation. The actual spatial relationship between the two will be finalized during testing to produce the optimal point like waveform dispersion. 
         [0125]    The user has access to the activation of the unit from sleep mode via operation of water and pressure proof momentary contact switch activator  19 . Operational parameters are displayed through the external projection of light pipe  18 . The digital circuitry of the middle board receive, store, and process programing to produce the predetermined waveform outputs. This includes the randomization as described elsewhere. It also includes responding to control activation and production of system status indication signals. It also controls power management and battery charging operations. 
         [0126]    The output of this digital control board is a four line buss connected to the switching amplifier. Three lines conduct pulse width modulation (PWM) signals to control the amount of voltage multiplication produced by this amplifier. The fourth line controls output polarity by changing its logic level. 
         [0127]    The switching amplifier is further detailed in  FIG. 2 . Most of the signals presented will comprise voltages of a negative polarity with respect to the output electrode. The battery voltage will be from three to six volts approximately. Combinational logic circuitry is included in this amplifier to reduce the number of control lines needed from the digital logic portion of the device. The amplifier consists of three levels of voltage multiplication. Each has a maximum voltage multiplication of about 10 times. Each level of voltage multiplication or inversion charges a capacitor shunted by a bleeder resistor. This network stores energy to feed the next level of voltage multiplication or inversion. This gives a total possible multiplication of about one thousand times the battery voltage with a polarity of positive or negative. In order to achieve such voltage multiplication, the lower level stages must process more current than the higher level units. However, it is a goal of this design to make the unit as small as possible. Capacitor and inductor size are minimized by this circuit&#39;s typology. Lower voltage switching units are paralleled and also switch on opposite sides of the control waveform in order to maximize current push with minimal inductor size. Though the output often does not exceed over one kilohertz, the switching frequency is about one hundred kilohertz. These combinations minimize circuit size, are constant with high efficiency, and consistent with high resolution. 
         [0128]    The typology is as such. The first stage of voltage multiplication consists of two parallel switching units operating in concert with two more operating on the opposite side of the PWM waveform. Each individual switching unit can supply a maximum amount of energy based on the magnetic characteristics of its inductor. As a result, at lower voltages requiring more current, switching unit numbers are maximized. As the voltage gets higher, the amount of current needed decreases and at successively higher voltage levels, the number of switching units becomes progressively less. The trade off is that the individual components of the higher voltage units must handle higher voltages. Except for transfer losses, the power level remains about the same through the voltage multiplication levels. For positive output, a voltage inversion switching unit is shown. This feeds a separate third stage voltage multiplication switching unit. Gates and diodes control voltage flow for the positive and negative outputs. An optional clamp circuit is shown in figure two. It in essence, when activated, places clamp resistor  84  in parallel with output bleeder resistor  54 . This changes the time constant of the output filter to allow for more rapid shifting between the negative to positive transition. Since most of the time the unit is producing a negative polarity, the speed of the positive to negative transitions is not as important. The normal time constant of the output network should be adequate. This will increase the timing delay required during this transition, but it should not be significant. This eliminates the need for a clamp of opposite polarity to handle the positive to negative transition. In situations where this delay may become significant, an additional clamp can be added. The down side is more complex logic control and the possibility of the need of an additional bus line from the digital output. The individual switching elements are of standard voltage multiplication and voltage inversion typologies. Combinational logic comprised of inverters and “and” gates is provided to reduce the number of control lines needed. Buffering action is accomplished by placing two inverters in series in order to simplify the logic typology. 
       OPERATION OF INVENTION AND IT&#39;S ALTERNATIVE EMBODIMENTS 
       [0129]    The operation of this invention is based on the randomized production of electrical voltage sequences. These will produce electric field patterns in water. These electric field patterns are sensed by the shark&#39;s electroreception system. The CNS interprets these patterns as representing various stimuli. These sensed patterns evoke images within the CNS. These image patterns within the CNS evoke behavioral responses causing the shark to leave the area. Other electric field patterns interfere with: sensor operation, peripheral nervous system function, and CNS function in predetermined manners. Additional patterns will be recognized by future research. This invention can be then upgraded to increasingly more effective patterns through reprogramming. 
         [0130]    The aqueous environment represents basically a very low electrical impedance medium. The pore openings of the sharks electro receptor sensory system match this impedance by presenting a zero ohm impedance across the opening of these pores. The conductive gel canals leading into the ampullae transform this zero impedance to a high level in the range of a hundred thousand ohms or greater. They additionally serve as a rapid cut off low pass filters. The result is sensitivity to electric fields as low as 1-6×10 −9  volts per meter. 
         [0131]    This invention is an electric waveform generator producing voltages into the low kilovolt range. These potentials are at very low power levels. Normally, they would not be able to drive such a low impedance as presented by the ocean environment. This invention uses a driven electrode arrangement that approaches that of being a unipolar electrode. As a result it behaves like a point source radiator. The output of the switching amplifier is coupled to spherical output electrode  24  via a filter network of output bleeder resistor  54  and output filter capacitor  55 . These set the time constant of this network. This time constant affects whether the output pulsations of the switching amplifier differentiate or integrate in production of the resultant electric field wave shape. In certain applications, optional clamp circuit(s)  90  place clamp resistor(s)  84  across output bleeder resistor  54 . This gives control over the decay characteristics of the output filter time constant discharge response. 
         [0132]    The ground balance resistor  53  is of a very high ohmic value, most likely in the megohm range. It limits the current output of the switching amplifier to levels consistent with its power output levels. The output voltage develops across this resistor with relationship to internal ground reference point(s)  37 . Internal ground floats with respect to aquatic ground. The internal ground “dithers” about the average of aquatic ground. As a result output electrode  24  is pushed towards the peak voltage across the output filter, whether it be positive or negative. This permits this electrode to mimic the action of a unipolar point source radiator at high impedance. A resultant electric field radiates in a spherical like manner outward from output electrode  24 . The current between output electrode  24  and ground balance electrode  23  is therefore limited by ground balance resistor  53 . The output impedance seen by switching amplifier  52  becomes essentially the resistance of ground balance resistor  53 . The high impedance of the amplifier output is therefore matched to the approximately zero impedance of the aquatic environment. Previous inventions dissipate significant power between the electrodes while forming an electric field. This system minimizes this power dissipation by reducing unnecessary power losses. In also makes the electric field pattern approach that of an expanding sphere. 
         [0133]    The primary digital portion of this device is located on middle printed circuit board  41 . 
         [0134]    System boot and low level operation memory is located in read only memory  44 . Programing is stored in programmable memory  43 . It is accessed and controlled by memory controller  45 , input and output controller  42 , and in and out port connection  36 . Operation control logic and control interface  46  manages operation of control switches, light emitting diode(s)  40 , power controller  57 , and charging circuit  58 . Clock  47  provides the primary time base for the system. Other timers as needed are implemented in software or hardware as appropriate. Programming in volatile and nonvolatile memory contains instructions to operate the control logic, and to operate the central processing and control logic unit  48 . 
         [0135]    Pattern generation of randomized sequences is generated within the central processing and control logic unit  48 . There is no feedback between the output and the control logic. Patterns generated are tested and calibrated to produce predetermined electric fields during operational testing. Accuracy of small amplitude variations in the electric field are not important. It is the waveform pattern that matters most. As a result, complex feedback is not needed. 
         [0136]    Digital and control logic monitor the rechargeable battery  33 , including its state of charge, charging operations, and battery conditioning (if condition circuitry is included in the charger). Such conditioning would include a pulse generation switching circuit as appropriate for some battery compositions. These circuits also control power controller  57 . 
         [0137]    Switching amplifier is detailed in  FIG. 2 . Starting with a negative input at the first level of voltage multiplication, four units of step up inverters are shown in this first stage. Two circuits are paralleled. The paralleled other two switch on during the opposite polarity of the PWM waveform. This PWM waveform is inverted to drive these opposite polarity switchers. This gives a total of four switching units for this first stage which must be capable of providing the most current. In order to keep inductor size at a minimum, four inductors are used. The individual catch diodes then pass this multiplied voltage to the first filter network of first multiplication bleeder resistor  81  and first multiplication filter capacitor  87 . Here the voltage is up to about ten times the battery voltage. Its amplitude is controlled by the PWM waveform. The time constant of the filter network is sufficient to maintain an adequate voltage level for the second switching stage, which consists of two paralleled switching units. The current requirements decrease with increasing voltage multiplication. The output of its filter network is utilized either by the third stage multiplication switching unit or the inversion switching unit. This is controlled by the logic level on buss line four which controls output polarity. Combinational logic of “and” gates and inverters controls this polarity transition. When inversion is not present, the gate enhancement mode field effect transistor  75  is enabled to let the output of this stage pass to the output filter. With voltage inversion present, third multiplication enhancement mode field effect transistor  72  is not enabled. With voltage inversion enabled, inversion enhancement mode field effect transistor  73 , inverse third multiplication enhancement mode field effect transistor  74 , and gate enhancement mode field effect transistor  75  are enabled. The voltage is inverted then goes through a separate positive third multiplication stage. The output gate is enabled allowing this voltage to charge the output filter. 
         [0138]    Output filter comprising output bleeder resistor  54  and output filter capacitor  55  has a time constant of a predetermined value to relatively differentiate or integrate the pulsing output of the switching amplifier depending upon its waveform characteristics with relation to this output filter network characteristics. Optional clamp circuit  90  is used to modify this time constant as needed during polarity transitions. It may also be used with waveform patterns optimized by such change. If needed, more than one clamp circuit may be utilized, but each additional clamp would require a separate control line from the digital circuit. If more than two clamps are needed, control of the clamps and polarity can be encoded. Decoding can then be done by additional combinational logic within the amplifier in order to minimize the number of additional control lines. Operation of this circuit is standard for switching amplifiers and is known to those experienced in such art. 
         [0139]    Power from the utility line is brought into the charger base comprising a standard circuit composed of wall outlet power plug  25 , wire(s)  26 , fuse  27 , metal oxide varistor  28 , line filter capacitor  29 , and power transformer primary  30 . Magnetic circuit  31  projects magnetic energy into the unit which is picked up by its matching magnetic circuit  31  and transferred into power transformer secondary  32 . This secondary potential is rectified and its presence activates the charging and control logic circuitry. The rate of battery recharge and optional battery conditioning is automatically controlled using means standard to those experienced with such art. 
         [0140]    The embodiment described in the preceding paragraphs is the preferred embodiment of this invention. It involves a bipolar switching amplifier controlled by programmable digital logic. Variations of construction of this device do not alter this embodiment. The principal remains the same. 
         [0141]    An alternate embodiment will be briefly referenced in this application. No drawings are presented at this time. It is a simplified, more inexpensive version of the preferred embodiment. It uses a non re-programmable digital logic circuit. Its programming is fixed during manufacture. In its simplest form, it does not use a bipolar switching amplifier, but a unipolar switching amplifier. Most of the words to be presented by this invention involve a single polarity. A predetermined set of words is programed during manufacture. Either by programing or hardware implementation, multiple pseudo random number generators are implemented. The predetermined words are presented in a pseudo random sequence. Other pseudo random number sequences increase randomization by randomizing word characteristics such as frequency, amplitude, decay characteristics, ring characteristics, harmonic content and relationships, and in ways that becomes apparent through research. This is implemented in a non upgradable, simpler hardware approach. This is an more simpler and economical approach to this technology, and will be appropriate under certain conditions. 
         [0142]    Both of these embodiments are appropriate for further modification and improvement. An obvious improvement would be algorithm control. The programing algorithm implemented determines the basic operational behavior of this unit. The primary algorithm will be presenting a randomized pattern of stimulus words. User and other means of algorithm control could modify this pattern of response. 
         [0143]    A very simple modification to the basic design would be to incorporate a second user operative switch. Such a switch would have a means of making its operation different from that of the switch used to wake the unit from sleep. This could be as simple as a mechanical arrangement making the sliding of the second switch mechanical operator necessary in combination with pressing this second switch for shark alarm status activation. 
         [0144]    Another method would to be to provide a second switch and mechanical operator as shown in  FIG. 1  as items  38  and  39 . This switch could be located on the opposite side of case  10 . To activate shark alarm, the user would press both switches at the same time. These switch arrangements are not shown in the drawings or described in the specifications above. This switch would be activated when the user notices the presence of a shark or sharks within an observable proximity. Activation of shark alarm status would change the operational parameters in manners making the unit more noxious to sharks. Such changes in operational algorithms would result in increased electrical consumption and result in shortened operational time on a given battery charge. It would allow the user to leave the water while in the presence of increased shark deterrence. Multiple activation&#39;s of shark alarm status could, via programing of the logic unit, increase the intensity and aggressiveness of the electric fields produced by the unit. Programed into logic would also be a sequence of switch operations permitting deactivation of shark alarm status, allowing battery charge conservation when such heightened deterrence is no longer deemed necessary by the user. Such mechanisms are known by those trained in such arts. This would allow the user to input shark alarm control messages to the logic circuit. 
         [0145]    Future versions of this invention may someday be able to incorporate an automated sensor of the presence of sharks within proximity of the unit. The design of this present unit allows for the incorporation of shark alarm status either by user input or by future developed shark presence sensors. Activation of this switch or a future sensor would input a second control signal into the control logic circuitry. This would activate the status of shark alarm. 
         [0146]    Input of a shark alarm condition would allow the switching to different programing algorithms. The percentage of near field stimuli will change. The percentage of noxious, CNS interference, and sensor overload stimuli will change. Randomization patterns will be changed. Word selection from various categories will be changed. Such operational changes most likely would increase the temporal power consumption of the unit, thus decreasing the time in which a battery charge would last. As a result of power consumption changes, the operational implementation of the light signal patterns would need to be correspondingly changed. These changes will be able to be made on a graduated scale depending upon the number and timing of shark alarms received by a unit within a given time frame. With a single, non repetitive shark alarm signal, within a given time, the unit will be able to go back to the original programing algorithm. With multiple and frequent shark alarm status indications, the programming algorithms will become progressively skewed toward more intense signal patterns. Such modification of programing control is possible within the digital logic circuitry of this original unit. Such algorithm modification routines may be upgraded by programing, as they are discovered by research and field testing. The original and preferred embodiment of this invention is adaptable to this additional capability by the simple incorporation of a second user operational switch or sensor to activate a shark alarm status. All other changes will be done in programming. 
       CONCLUSION, RAMIFICATIONS, AND SCOPE 
       [0147]    A need exists for an effective means of safely repelling sharks from humans. Many approaches have been attempted by inventors. In some of these cases, an effective stimulus was found, but the sharks were able to learn and adapt to these fixed patterns of stimuli. This invention breaks new ground by taking an approach of presenting multi-factorial stimuli in a highly randomized manner to avoid and prevent adaptation. This becomes possible with programmable digital logic. This logic develops a multi line signal capable of controlling the output of a highly efficient and miniaturized switching amplifier. The unit is capable of being miniaturized to the point of mounting it on the ankle of a user. System control has been designed to make operation as fail safe as possible. Adjustment of operational parameters is not available to the user in order to prevent adjustment of the unit into ineffective operational parameters. 
         [0148]    This invention is applicable to many other end uses besides repelling sharks. I have touched briefly above on some of these. These include: adaptation to provide for having aquatic life safely leave the pathways of ships; to clear areas of ocean environments of life sensitive to navy sonar signals; to bring complex randomization to other organism repellant means which generate stimuli based on electric signal patterns. 
         [0149]    In the descriptions above, the reader has seen several embodiments of my invention. There are differing applications for these electric pattern generators. One example is a shark repellant device which is upgradable via programming. A proposed name is “shark away.” Another example is a simpler and more economical shark repellant device which cannot be upgraded via programming. A proposed name is “shark be gone.” Other applications include simpler devices for repelling other creatures such as rodents and insects where there is not a threat of injury or death to humans. These applications become less critical, and programing upgradability may not be needed for many applications. Further adaptations include: Units with long life battery capacities for life rafts, units rechargeable with solar power; and eventually units that can electrically sense the approach of a shark and thus modify its electrical response with increasingly noxious stimuli. These very different applications will make best use of differing embodiments of my invention. 
         [0150]    In the descriptions above, I have put forth theories of operation that I believe to be correct. While I believe these theories to be correct, I don&#39;t wish to be bound by them. While there have been described above the principals of this invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and is not as a limitation to the scope of the invention.