Abstract:
A system and method for fencelessly controlling the location of an animal comprising a location determining component and a stimulus device adapted to attach to the animal. The location determining component may send the location of the animal to a computing device, which may determine the location relative to the boundary and a warning zone of the boundary. If the location is within the warning zone of the boundary, the computing device may determine if the animal has moved closer to the boundary or farther from the boundary based on its computed current distance from the boundary and its last recorded distance from the boundary. If the animal has moved closer to the boundary, a first stimulus or negative feedback may be provided to the animal. If the animal has moved away from the boundary, a second stimulus or positive feedback may be provided to the animal.

Description:
RELATED APPLICATIONS 
       [0001]    This nonprovisional patent application claims priority benefit, with regard to all common subject matter, of earlier-filed U.S. provisional patent application titled “Multiple Feedback Animal Control Device,” Ser. No. 60/928,874, filed May 11, 2007. The identified earlier-filed application is hereby incorporated by reference in its entirety into the present application. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    Embodiments of the present invention relate to a system and method of fenceless control of animals, and more particularly, to the control of livestock and other domesticated animals utilizing receivers attached to the animals for receiving data identifying the location of the animal and administering appropriate control stimuli to the animal based on the location of the animal relative to a desired location. 
         [0004]    2. Related Art 
         [0005]    Animal owners often desire to remotely and/or automatically control the behavior of an animal to, for example, train or contain the animal. For example, farmers often wish to contain livestock in a particular area and prevent the livestock from approaching and entering other areas. One method of remotely controlling the behavior of an animal is by delivering a stimulus to the animal when the animal&#39;s behavior deviates from a desired pattern of behavior. An exemplary device for delivering a stimulus is an animal collar adapted to deliver an electrical shock or an acoustical stimulus to the animal. 
         [0006]    Containment systems using such devices may perform autonomous location determination using, for example, a Global Positioning System (GPS). In such systems, animal control devices may include a Global Positioning System (GPS) receiver and memory element thereon, wherein the memory element is adapted to store map or location information relating to a boundary or a restricted area. Such devices are adapted to determine a location by using information from the GPS receiver and the map or location information. If the animal wearing the collar approaches or enters a restricted area, the collar delivers a corrective stimulus, such as an electrical shock or an acoustical stimulus, thus motivating the animal to leave the restricted area. 
         [0007]    However, current animal containment or barrier systems having GPS capabilities as discussed above may confuse the animal in various situations. Because there is no visible boundary, for example, there may be situations in which the animal receives a corrective stimulus but does not immediately know which direction to move, or worse, moves a short distance in a desired or appropriate direction but receives another corrective stimulus. These issues are particularly acute where the boundary location has changed since the animal&#39;s last encounter with it. 
         [0008]    Accordingly, there is a need for a system and method for fenceless animal control that does not suffer from the problems and limitations of the prior art. 
       SUMMARY 
       [0009]    Various embodiments of the present invention provide an invisible barrier system to control the location of animals without requiring physical fencing. The invisible barrier system may comprise a location determining component, such as a global positioning system (GPS) receiver, and a stimulus device for providing at least one stimulus to the animal. The location determining component and the stimulus device may both be attached to the animal. The confinement system may further comprise a computing device, memory, a user interface, a display, a transmitter, a receiver, a power source, and I/O ports. The stimulus provided by the stimulus device to the animal may be an audible warning, an electric shock, a vibration, a visual warning, or any other type of stimulus known in the art. Various components of the confinement system  10  may be attached to the animal via a collar, an ear tag, a harness, or any means known in the art for securing an object to an animal. 
         [0010]    The computing device may compare the location information with defined boundary parameters and activate the stimulus when the animal wearing the location determining component crosses the defined boundary. Additionally, if the animal is determined to be within a given warning zone from the boundary, a stimulus may be provided to the animal as a warning that the animal is too close to the boundary. 
         [0011]    In various embodiments of the invention, a first stimulus may be provided when the animal is within the warning zone and moving towards the boundary, and a second stimulus may be provided as the animal begins to move away from the boundary but is still within the warning zone. To determine if the animal is moving towards or away from the boundary, the computing device may obtain the positions of the animal at a given time interval and store at least one previous position reading in memory such that the distance of a current position to the boundary may be compared with the distance of the previously-stored position to the boundary. 
         [0012]    The first stimulus may, for example, be a tone having a first pitch, while the second stimulus may be the tone having a second pitch. Alternatively, the first stimulus may be an audible tone that gradually rises in pitch and/or volume as the animal approaches the boundary within the warning zone and the second stimulus may be an audible tone that gradually decreases in pitch and/or volume as the animal moves away from the boundary within the warning zone. In some embodiments of the invention, a third stimulus, such as an electric shock, may be provided when the animal crosses the boundary. 
         [0013]    These and other important aspects of the present invention are described more fully in the detailed description below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein: 
           [0015]      FIG. 1  is a diagram of an invisible barrier system according to embodiments of the present invention; 
           [0016]      FIG. 2  is a block diagram illustrating certain components of the invisible barrier system of  FIG. 1 ; 
           [0017]      FIG. 3  is a schematic diagram of a Global Positioning System (GPS) that may be used to send GPS signals to the invisible barrier system of  FIG. 1 ; 
           [0018]      FIG. 4  is a map of a geographic boundary and warning zone as defined in and monitored by the invisible barrier system; and 
           [0019]      FIG. 5  is a flow chart illustrating method steps that may be performed by the invisible barrier system. 
       
    
    
       [0020]    The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. 
       DETAILED DESCRIPTION 
       [0021]    The following detailed description of the invention references the accompanying drawing figures that illustrate specific embodiments in which the present invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. 
         [0022]    Embodiments of the present invention, as illustrated in  FIGS. 1 and 2 , provide an invisible barrier system  10  for preventing an animal  12  from crossing a desired geographic boundary  14  without the use of fences or other physical barriers. The invisible barrier system  10  may comprise a location determining component  18 , a stimulus device  20  for providing at least one stimulus to the animal  12  depending on its location, and an attachment apparatus  22  for securing the location determining component  18  and the stimulus device  20  to the animal. The invisible barrier system  10  may further comprise a computing device  24 , memory  26 , a user interface  28 , a display  30 , a transmitter  32 , a receiver  34 , a power source  16 , and I/O ports  36 . 
         [0023]    Exemplary automated animal control systems are disclosed in U.S. Pat. Nos. 5,868,100; 6,155,208; and 6,956,483, all of which are hereby incorporated by reference in their entirety into the present application. 
         [0024]    The animal  12  may be a cow, horse, sheep, swine or other livestock, or may be pet, such as a dog or cat. It will be appreciated that the animal  12  is not limited to those listed and discussed herein, but may be virtually any animal. 
         [0025]    The location determining component  18  determines positions of the animal  12  as it moves from place to place and generates and sends corresponding position data to the computing device  24 . The location determining component  18  may use global positioning system (GPS) data, as taught in U.S. Pat. No. 5,868,100. U.S. Pat. No. 5,868,100 is hereby incorporated by reference in its entirety, and, in particular, the GPS system and components disclosed therein. Alternatively, the location determining component  18  may use RF system data. 
         [0026]      FIG. 3  shows a representative view of a global positioning system denoted generally by reference numeral  38 . A plurality of satellites  40  are in orbit about the Earth  42 . The orbit of each satellite is not necessarily synchronous with the orbits of other satellites and, in fact is likely asynchronous. The location determining component  18  is shown as a GPS receiver, receiving spread spectrum GPS satellite signals from the various satellites  40 . The location determining component  18  may include an antenna to assist in receiving the satellite signals. The antenna may be a removable quad-helix antenna or any other type of antenna that can be used with navigational devices. 
         [0027]    The spread spectrum signals continuously transmitted from each satellite  40  utilize a highly accurate frequency standard accomplished with an extremely accurate atomic clock. Each satellite  40 , as part of its data signal transmission, transmits a data stream indicative of that particular satellite. As a GPS receiver, the location determining component  18  must acquire spread spectrum GPS satellite signals from at least three satellites for the location determining component  18  to calculate its two-dimensional position by triangulation. Acquisition of an additional signal, resulting in signals from a total of four satellites, permits the location determining component  18  to calculate its three-dimensional position. 
         [0028]    Although in one embodiment the location-determining device  18  is a GPS receiver, it is noted that equivalents may be employed and substitutions made without departing from the scope of the invention as recited in the claims. For example, in various embodiments of the invention, the location determining component  18  need not directly determine its current geographic position. For instance, the location determining components  8  may determine the current geographic position by receiving position information directly from the user, through a communications network, or from another electronic device. 
         [0029]    The location determining component  18  may include one or more processors, controllers, and/or other computing devices and memory so that it may calculate position and other geographic information without the computing device  24 . Further, the location determining component  18  may be integral with the computing device  24  such that the location determining component  18  may be operable to specifically perform the various functions described herein. Thus, the computing device  24  and location determining component  18  can be combined or be separate or otherwise discrete elements. 
         [0030]    The stimulus device  20  may be electrically and/or communicably coupled with the location determining components  8  and the computing device  24 . The stimulus device  20  may be physically integrated with the location determining component  18  and the computing device  24 , or alternatively may be attached to the animal  12  independently and may communicate with the location determining component  18  and computing device  24  via wireless transmitters and receivers, such as RF transmitters and other devices for wireless transmission as known in the art as described herein. The stimulus device  20  may be any device that provides a stimulus, such as an audible warning, an electric signal, a vibration, a visual warning, or any other type of stimulus known in the art. Additionally, the stimulus device  20  may provide various types of stimuli individually or in combination with other types of stimuli. For example, the stimulus device may provide both an audible warning and an electric shock simultaneously or in series. The audible warning may include any combination of frequencies, pitches, and volume levels and may sound for any duration of time. For example, the audible warning may be a series of short, loud, high-pitched tones or a continuous, loud, high-pitched tone which only stops when the location determining component  18  is no longer near or no longer past the boundary  14 . 
         [0031]    The attachment apparatus  22  may be a collar, an ear tag, a harness, or any means known in the art for securing an object to an animal. In various embodiments of the invention, the location determining component  18  and the stimulus device  20  may be attached to the animal using two separate attachment apparatuses  22 . For example, the stimulus device  20  may be attached to the animal&#39;s ear using an ear tag, while the location determining component  18  may be attached to the animals neck using a collar. Alternatively, all components of the system  10  may be attached to the animal using the single attachment apparatus  22 . 
         [0032]    In various embodiments of the invention, the attachment apparatus  22  may incorporate means for monitoring desired physiological parameters of the animal, such as body temperature, blood pressure, or heart parameters. Systems for monitoring these parameters are well known, such as the system described in U.S. Pat. No. 4,399,821, incorporated herein by reference and made a part of the disclosure hereof. Signals representing this physiological information may be included with the location information signals transmitted to the computing device  24 . 
         [0033]    The computing device  24  may include any number of processors, controllers, integrated circuits, programmable logic devices, or other computing devices and resident or external memory for storing data and other information accessed and/or generated by the invisible barrier system  10 . The computing device  24  may be coupled with the location determining component  18 , the stimulus device  20 , the memory  26 , the user interface  28 , the display  30 , the transmitter  32 , the receiver  34 , the power source  16 , the I/O ports  36 , and other components through wired or wireless connections, such as a data bus  44 , to enable information to be exchanged between the various components. 
         [0034]    The computing device  24  may implement a computer program and/or code segments to perform the functions described herein. The computer program preferably comprises an ordered listing of executable instructions for implementing logical functions in the computing device  24 . The computer program can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, and execute the instructions. As used herein, a “computer-readable medium” can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-readable medium can be, for example, but not limited to, an electronic, magnetic, optical, electro-magnetic, infrared, or semi-conductor system, apparatus, device or propagation medium. More specific, although not inclusive, examples of the computer-readable medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a random access memory (RAM), a read-only memory (ROM), an erasable, programmable, read-only memory (EPROM or Flash memory), an optical fiber, and a portable compact disk read-only memory (CDROM). 
         [0035]    In some embodiments of the invention, the computing device  24  and other components of the invisible barrier system  10  may be located remotely in relation to the animal  12 , the location determining component  18 , and/or the stimulus device  20 . For example, the stimulus device  20  and the location determining component  18  may be located on the collar of the animal  12 , while the computing device  24  and memory  26  may be located in a fixed station  46  which is not attached to the animal  12 , as illustrated in  FIG. 1 . In various embodiments of the invention, the computing device  24  may be used to determine the location of and activate stimuli for a plurality of animals having location determining components  18  and stimulus devices  20  attached to their bodies. Additionally, a user at the fixed station  46  could be notified if any one of the animals crosses the boundary  14 . 
         [0036]    The memory  26  may be integral with the location determining component  18 , integral with the computing device  24 , stand-alone memory, or a combination of both. The memory may include, for example, removable and non-removable memory elements such as RAM, ROM, flash, magnetic, optical, USB memory devices, and/or other conventional memory elements. In various embodiments of the invention, the memory  26  may be remotely programmable to receive and store parameters for the desired boundary  14 . 
         [0037]    The memory  26  may store various data associated with the operation of the invisible barrier system  10 , such as the computer program and code segments mentioned above, or other data for instructing the computing device  24  and system elements to perform the steps described herein. Further, the memory  26  may store: physiological information about the animal  12 ; data corresponding to geographic positions of the animal  12  or animals; parameters for the boundary  14  including map data and map elements; a sample rate or a determination interval defining the amount of time between each obtaining of the animal&#39;s position; and other information to facilitate the various functions provided by the invisible barrier system  10 . The various data stored within the memory  26  may also be associated with one more databases to facilitate retrieval of the information. Additionally, the memory  26  may store previously calculated or otherwise acquire animal position information for later retrieval by the computing device  24 . For example, the stored position information for a previous location of the animal  12  may be retrieved and compared with a present location of the animal  12  in order to determine if the animal is moving toward or away from the boundary  14 . 
         [0038]    The user interface  28  permits a user to operate the invisible barrier system  10  and enables users, third parties, or other devices to share information with the confinement system  10 . The user interface  28  may comprise one or more functionable inputs such as buttons, switches, scroll wheels, a touch screen associated with the display  30 , voice recognition elements such as a microphone, pointing devices such as mice, touchpads, tracking balls, styluses, a camera such as a digital or film still or video camera, combinations thereof, etc. Further, the user interface  28  may comprise wired or wireless data transfer elements such as a removable memory including the memory  26 , data transceivers, etc., to enable the user and other devices or parties to remotely interface with the confinement system  10 . The device may also include a speaker for providing audible instructions and feedback. 
         [0039]    The user interface  28  may provide various information to the user utilizing the display  30  or other visual or audio elements such as a speaker. Thus, the user interface  28  enables the user and confinement system  10  to exchange information relating to the confinement system  10 , including configuration information, preferences, alerts, stimulus limits (limiting intensity, frequency of occurrence, etc.), boundary parameters, desired physiological parameters of the animal  12 , a sample rate of location information, type of stimulus to apply, etc. 
         [0040]    The display  30  is coupled with the computing device  24  and is operable to display various information corresponding to the animal  12  and the invisible barrier system  10 , such as maps, positions, the boundary  14 , and physiological information regarding the animal  12 . The display  30  may comprise conventional black and white, monochrome, or color display elements including CRT, TFT, LCD, and/or plasma display devices. The display  30  may be integrated with the user interface  28 , such as in embodiments where the display  30  is a touch-screen display to enable the user to interact with it by touching or pointing at display areas to provide information to the invisible barrier system  10 . 
         [0041]    The transmitter  32  and receiver  34  may communicate with each other wirelessly, exchanging data between the location determining component  18 , the stimulus device  20 , and the computing device  24 . In various embodiments of the invention, a plurality of the confinement system  10  components are each coupled with individual transmitters and receivers, so that each of these components may send and receive data signals. 
         [0042]    The transmitter  32  may include antennas, amplifiers, tuners, filters, encoders, and other components for transmitting data signals wirelessly, as known in the art. The transmitter  32  may transmit at a wide range of carrier frequencies and may encode or modulate data using FM, QAM, PSK, etc. The transmitter  32  may include analog electronics, digital electronics, or a combination of both, as well as electrical components such as microprocessors, microcontrollers, or digital signal processors. 
         [0043]    The receiver  34  may include antennas, amplifiers tuners filters, decoders, and other components for receiving wireless data signals, as known in the art. The receiver may receive a wide range of carrier frequencies and may decode or demodulate data using FM, QAM, PSK, etc. The receiver  34  may include analog electronics, digital electronics, or a combination of both, as well as electrical components such as microprocessors, microcontrollers, or digital signal processors. 
         [0044]    The I/O ports  36  permit data and other information to be transferred to and from the computing device  24  and the location determining component  18 . The I/O ports  36  may include a TransFlash card slot for receiving removable TransFlash cards and a USB port for coupling with a USB cable connected to another computing device such as a personal computer. Maps, boundaries, stimulus limits, physiological data, and other data and information may be loaded in the confinement system  10  via the I/O ports  36 . 
         [0045]    The power source  16  provides electrical power to various invisible barrier system  10  elements. For example, the power source  16  may be directly or indirectly coupled with the location determining component  18 , the stimulus device  20 , and the computing device  24 . The power source  16  may comprise conventional power supply elements such as batteries, battery packs, etc. The power source  16  may also comprise power conduits, connectors, and receptacles operable to receive batteries, battery connectors, or power cables. 
         [0046]    As discussed, the boundary  14  may be defined by data stored in the memory  26 , user input of boundary parameters into the computing device  24 , and various other methods. The user may also change the location of the boundary  14  as needed via the user interface  28 , wireless transmission, or the I/O ports  36 . The boundary  14  may form a complete 360-degree enclosure around the animal(s)  12 . Alternatively, the boundary may not surround the animals, but rather forms an invisible barrier between the animals and a danger, such as a power box or a cliff. Known geographic coordinates of various boundary points may be interpolated to form the boundary  14 . 
         [0047]    For example, the user may define a rectangle by entering the latitude and longitude of each of the four corners or a circle by the latitude and longitude of its center and a specified radius. Other standard shapes could be preprogrammed into the memory  26 , or irregular shapes may be defined by the interpolation of a plurality of geographical positions. The design and operation of means for entering boundary parameters are well known in the art and are not repeated here. 
         [0048]    The warning zone  48 , illustrated in  FIG. 4 , may be defined by the user via the user interface  28  or may otherwise be provided to the computing device  24  via the memory  26 , I/O ports  36 , or wireless transmission. The warning zone  48  is on the same side of the boundary  14  as the animal(s) are desired to remain and begins at a pre-defined distance from the boundary  14 , extending all the way to the boundary  14 . For example, the warning zone  48  may be inward of the boundary  14  in the case of a 360-degree boundary surrounding the animals. However, in a situation where the boundary  14  surrounds an area that the animals should not enter, such as an open well, the warning zone may be outward of the 360-degree boundary  14 . In various embodiments of the invention, the warning zone  48  may begin at a distance within the range of 1 m to 500 m away from the boundary  14 . Alternatively, the warning zone  48  may begin at a distance within the range of 10 m to 100 m away from the boundary or within the range of 20 m to 50 m away from the boundary. 
         [0049]    In use, the computing device  24  may compare the location of the animal  12  with the boundary  14  and activate the stimulus device  20  when the animal  12  crosses the defined boundary  14 . Additionally, if the animal  12  is determined to be within the warning zone  48 , a stimulus may be provided to the animal as a warning that the animal is too close to the boundary  14 . For example, if the computing device  24  determines that the animal  12  has moved within the warning zone  48  or within a defined distance, say five meters, of the boundary  14 , the stimulus device  20  may be activated. 
         [0050]    The computing device  24  may define appropriate stimuli to the animal  12  for various circumstances, such as when the animal  12  is within the warning zone  48 , approaches the boundary  14 , crosses the boundary  14 , or moves away from the boundary  14 . The computing device  24  may contain stimuli information and instructions in memory  26  or may receive instructions regarding appropriate types and amounts of stimuli from the user via the user interface  28 , I/O ports  36 , or wireless transmission. 
         [0051]    In various embodiments of the invention, a first stimulus may be provided when the animal wearing the location determining component  18  is within the warning zone  48  and moving towards the boundary  14 , as illustrated by animal  100  in  FIG. 4 , and a second stimulus may be provided as the animal begins to move away from the boundary  14 , but is still within the warning zone  48 , as illustrated by animal  102  in  FIG. 4 . 
         [0052]    To determine if the animal  12  is moving towards or away from the boundary  14 , the computing device  24  may obtain a current position of the animal at a current point in time from the location determining component  18  and obtain at least one previously determined position at a previous point in time from memory  26  such that the distance of the current position to the boundary  14  may be compared with the distance of the previously-determined position to the boundary  14 . If the distance to the boundary  14  has decreased or remained the same, then the first stimulus may be provided. If the distance to the boundary  14  has increased, then the second stimulus may be provided. 
         [0053]    In one embodiment of the invention, as illustrated in the flow chart of  FIG. 5 , the computing device  24  may receive input boundary parameters  200 , an input interval of time  202 , and an input warning zone  204 . Next, based on input from the location determining component  18 , the computing device  24  may determine the animal location X(i), as shown in step  206 . Then, as shown in step  208 , the computing device  24  may compare the animal location X(i) with the boundary parameters  200 . Step  210  illustrates determining if X(i) is within the warning zone  204  of the boundary parameters  200 . If it is not, then step  212  requires that the invisible barrier system  10  wait for the interval of time  202  to pass before obtaining the next location of the animal  12 . If X(i) is within the warning zone  204  of the boundary parameters  200 , then, as shown in step  214 , the computing device  24  may calculate distance D(i), which is the distance between the current animal location X(i) and the boundary parameters BP. 
         [0054]    In step  216 , the computing device  24  may determine if D(i) is greater than D(i−1), or in other words if the animal&#39;s distance from the boundary  14  is greater than its previously-recorded distance from the boundary. If the distance D(i) is greater than D(i−1), then the second stimulus, also referenced as positive feedback  218 , may be applied to the animal  12 . If the distance D(i) is not greater than D(i−1), then the first stimulus, also referenced as negative feedback  220 , may be applied to the animal  12 . 
         [0055]    The first stimulus may, for example, be a tone having a first pitch, while the second stimulus may be the tone having a second pitch. Alternatively, the first stimulus may be an audible tone that gradually rises in pitch, speed, and/or volume as the animal  12  approaches the boundary  14  within the warning zone  48  and the second stimulus may be an audible tone that gradually decreases in pitch, speed, and/or volume as the animal  12  moves away from the boundary  14  within the warning zone  48 . In some embodiments of the invention, a third stimulus, such as an electric shock, may be provided when the boundary  48  is crossed by the animal, as illustrated by animal  104  in  FIG. 4 . In other words, if the current location of the animal  12  is on an undesired side of the boundary and the previously determined location of the animal  12  was on a desired side of the boundary  14 , then a shock may be applied. Or, if the current location of the animal  12  corresponds with the boundary  14 , then a shock may be applied. 
         [0056]    In one embodiment of the invention, a continuous stimulus is activated when the animal  12  enters the warning zone  48 , and the volume, speed, or pitch of the stimulus is gradually adjusted depending on the animal&#39;s proximity to the boundary  14 . Thus, if the animal  12  has moved closer to the boundary  14  between the previous point in time and the current point in time, the volume of the stimulus may be adjusted upward by the computing device  24 . Likewise, if the animal  12  has moved farther from the boundary  14  between the previous point in time and the current point in time, the volume of the stimulus may be adjusted downward by the computing device  24 . 
         [0057]    By using a different stimulus or differing the direction of adjustment of the stimulus when the animal  12  is approaching the boundary  14  than when the animal  12  is moving away from the boundary  14 , the animal  12  may begin to associate these stimuli as negative feedback and positive feedback, and will respond accordingly. This is advantageous, since having only one type of feedback or stimulus provided to the animal while it is still within the warning zone  48  could confuse the animal  12  if it has already turned around and started moving away from the boundary  14  but continues to experience a warning stimulus. Therefore the present invention not only provides a negative or warning stimulus to the animal  12  as it moves closer to the boundary  14 , but also provides positive stimulus or feedback as soon as the computing device  24  determines that the animal  12  is beginning to move away from the boundary  14 . Once the animal moves a sufficient distance from the boundary  14 , the positive stimulus would cease. 
         [0058]    Although the invention has been described with reference to the embodiments illustrated in the attached drawings, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims. For example, if the location determining component  18  is an RF system as discussed in U.S. Pat. No. 6,155,208, incorporated by reference above, differences in signal strength may be used to determine whether the animal  12  is moving toward or away from signal transmitters defining the boundary.