Abstract:
A method of using radio frequency identification (RFID), in particular ultra high frequency (UHF) RFID, is described, which keeps pets from accessing forbidden areas. The pet wears a device which is preferably powered by the animal&#39;s own activity, converted to electrical power by a motion harvesting system to recharge a battery. The device uses an RFID reader to detect and identify RFID tags placed at boundaries of areas to which the pet is forbidden to enter, and sets off an alarm to warn the pet if it is approaching such an area. Because the RFID tags are individually identifiable, the forbidden area alarm can be configured to the pet, allowing use in a multiple-pet household.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims one or more inventions which were disclosed in Provisional Application No. 61/633,629, filed Feb. 15, 2012, entitled “RFID Wireless Pet Barrier”. The benefit under 35 USC §119(e) of the United States provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to the field of animal training. More particularly, the invention pertains to training animals to remain in or avoid a selected area using wireless alarm devices. 
     2. Description of Related Art 
     Over 30 million homes in the United States have house pets such as cats, dogs, rabbits or ferrets which are permitted access to some or all of the house. Worldwide, that number is in the hundreds of millions. A typical problem with having a house pet live in your home is that there are certain areas of the home the owner does not want the animal to enter. The area may be a danger to the pet or the pet may not be fully trained and can soil an expensive rug or couch. A further reason may be that the pet can inadvertently damage a display or piece of furniture. 
     The simplest way to keep a pet out of an area of the house is to close a door or put up physical barricade that will restrain the pet from entering or leaving a certain area. In a conventional house layout with physically divided rooms, this approach could solve some portion of the problem. However, in a house with an “open landscape” interior architecture, where one room flows into another with few dividing walls, this approach does not work well. 
     There are devices on the market that use a motion sensor to detect the presence of the pet and then sound an ultrasonic alarm. This makes the pet uncomfortable and could make it leave the area. A drawback to this approach is the pet needs to come into the vicinity of the device to be detected. Also, differentiating human motion from animal motion is difficult and the ultrasonic alarm can be on for an extended amount of time, so that the pet becomes accustomed to the sound, making the pet think that the sound is part of its environment rather than a warning. This prevents any learning about acceptable areas and unacceptable areas where the pet can venture. 
     Another device on the market to solve this problem is to have the pet wear a transmitter that gets detected by a stationary receiver. Whenever the transmitter gets in the vicinity of the receiver, indicating the pet is approaching a forbidden area, an ultrasonic noise is emitted or the pet gets electric shocks through its collar in differing implementation. A problem with these approaches is that the ultrasonic noise must be loud enough to prevent the pet from entering and the receiver is always a distance away from the pet. Using the shock treatment can be considered cruel to the pet, but if the shock is not strong enough to be a deterrent than it could be totally ineffectual. Another problem is that the transmitter in the pet&#39;s collar must be transmitting at all times and requires power from rechargeable or expendable batteries. If the batteries are not changed or recharged often, the device will not reinforce the pet&#39;s behavior and could become useless. A further problem with all of these devices is that there is no differentiation between pets in a multi-pet household. As an example, an older pet may be allowed in certain areas, but a puppy should be excluded, or the cat is allowed in rooms forbidden to the rabbit and vice-versa. 
     The Invisible Fence® system made by Invisible Fence, Inc., of Knoxville, Tenn., effectively is the reverse of this last system—the area within which a pet is to be confined is surrounded by a wire which continuously transmits a signal, and the pet (usually a dog) wears a receiver which picks up the signal from the wire. The pet is warned, as described above, when the receiver detects that it has approached the wire too closely. This system has the same drawbacks of the systems which have the pet carrying a transmitter, as well as requiring the entire area to be surrounded by the “fence” wire. In the typical outdoor installation, the wire can be buried, but it could be problematic to conceal the wire within a home. 
     SUMMARY OF THE INVENTION 
     A method of using radio frequency identification (RFID), in particular ultra high frequency (UHF) RFID, is described, which keeps pets from accessing forbidden areas. The pet wears a device which is preferably powered by the animal&#39;s own activity, converted to electrical power by a motion harvesting system to recharge a battery. The device uses an RFID reader to detect and identify RFID tags placed at boundaries of areas to which the pet is forbidden to enter, and warns the pet through an alarm if it is approaching such an area. Because the RFID tags are individually identifiable, the forbidden area alarm can be configured to the pet, allowing use in a multiple-pet household. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  shows a block diagram of the wireless pet barrier system as it might be installed in a home. 
         FIG. 2  shows a block diagram of the components of a wireless pet barrier system using the animal-borne device. 
         FIG. 3  shows a passive RFID tag suitable for use with the wireless pet barrier system. 
         FIG. 4  shows a block diagram of the animal-borne device for use with the wireless pet barrier system. 
         FIG. 5  shows an RFID antenna embedded in a collar for use with the animal-borne device. 
         FIG. 6  shows a flowchart of the method of operation of the animal-borne device of the wireless pet barrier system. 
         FIG. 7  shows two examples of an embodiment of the RFID tag. 
         FIG. 8  shows an RFID antenna embedded in a harness for use with the animal-borne device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows how a Pet Barrier system would be deployed in a representative house  1 . While the system is described herein as it would be used in a house, it will be understood that the system can be used both indoors or outdoors. The house has three bedrooms BR 1 -BR 3  along a hall H, a bathroom BT, dining room DR, kitchen K and living room LR. There is a front door  2  opening into the living room LR and a back door  3  leading into the kitchen K. The family in this example has three pets: an adult dog  4 , a puppy  6 , and a cat  8 . 
       FIG. 3  shows an example of a block or schematic diagram of an RFID tag which could be used with the system. It will be understood that the specific design shown is for example purposes only, to explain how passive RFID tags work, and other designs are usable within the teachings of the invention. Passive RFID tags are commercially available from numerous sources, for example, Alien Technologies in Morgan Hills, Calif., or Avery-Dennison in Flowery Branch, Ga. 
     The RFID tag has a base  30 , usually made of several layers of thick paper, stiff cardboard or thin plastic, within which the components are embedded or encapsulated. An antenna  31  and capacitor  32  form a resonant circuit which can be excited by a radio frequency (RF) signal of appropriate frequency and strength. While any of the commonly used frequency bands can be used within the teachings of the invention, operation with RF signals in the UHF band are preferred (865-868 MHz in Europe, 902-928 MHz in the US). 
     The antenna  31 -capacitor  32  circuit is coupled to a rectifier circuit, here shown as a full-wave bridge  34 , so that when an RF signal of appropriate frequency is received by the antenna  31 , it is rectified to direct current (DC) by the bridge  34  and charges a capacitor  35 . This provides DC power  38  to an RFID controller integrated circuit (IC)  36 . 
     The controller IC  36  is internally programmed with an identification number, so that when the IC  36  is powered up by the rectified RF signal, it outputs a digital signal  39  which is encoded with at least the identification number. This signal keys a transistor  33  to transmit the identification number back to the interrogating transmitter by transmitting the signal as an RF signal through antenna  31 . Thus, the signal from a given RFID tag can be identified by its unique identification number or code. 
     The tag body  30  may be provided with adhesive areas  37  which allow the tag to be easily attached to a wall wherever it is desired. The adhesive area  37  is preferably one of the removable non-marring kind which is used for hanging posters or the like. Alternatively, the tag body  30  could be provided with a hole to allow the tag to hang on a hook, or even with a larger hole to allow the tag to be structured as a doorknob hanger. 
     It will be understood that it is preferred that each tag be encoded with a “unique identification number” so that each individual tag can be uniquely identified by an RFID reader, and that a preferred embodiment will be used in the explanation of the system below. However, as the term “unique” is used in this explanation, this is not meant to imply that the tags need to be globally uniquely identifiable. The identification number actually only needs to identify the tag in such a way as to permit the operation of the system, and it is possible to use identification numbers which are assigned according to a rank or class or type and repeated through the system so that, for example, all bedroom tags have one number, all living/dining room tags another, tags placed near doors or stairs have yet another, and so on. 
     Another arrangement, shown in  FIG. 7 , would be for the RFID tags, such as these example tags  70   a  and  70   b , to be imprinted with a machine-readable code such as QR code  71  or bar code  74  containing the identification number of the tag  70   a  or  70   b . The user would read the bar coded tag ID, for example with a smart phone or tablet camera, using a popular bar code reading application such QR Droid for Android phones. Once all of the tags for a particular pet are read, the smart phone would be connected to that pet&#39;s animal-borne device controller via a USB wired connection or Wi-Fi wireless connection and the forbidden tag identification numbers would be downloaded into the animal-borne device. This would be a simple and low cost way to get the tag identifications into each pet&#39;s device. 
     Using this arrangement, it would be possible to have systems of RFID tags that relates to each pet, as shown in  FIG. 7 . Tags may be purchased with the pet&#39;s name  73  and possibly a picture of the pet  72 . These would be the tags that would mark an area where this particular pet cannot go. So, in the example of  FIG. 7 , tag  70   a  would be posted in an area which is forbidden to Bean the cat, while tag  70   b  would be posted in an area which is forbidden to Scone MacBunny the rabbit. 
     Other arrangements are possible within the teachings of the invention. 
     A plurality of passive RFID tags  10   a - 10   h  are located around the house, at least one in each area from which an animal is to be excluded or to which an animal is to be restricted. It will be understood that, depending on the area(s) to be covered and the range of the tags, a single tag might cover more than one room, or several tags might be needed within a single room. If there is a specific item or smaller area to be covered, a tag might be allocated to that—for example, a tag can be inserted into the cushions of a couch or chair to keep a pet off the furniture. 
     Each of the animals is provided with an animal-borne device  20 -device  5  is worn by adult dog  4 , device  7  by puppy  6  and device  9  by cat  8 . An example of an animal-borne device is shown in block form in  FIG. 2 . The animal-borne device  20  is provided with a strap or harness  23  which can securely attach the device  20  to an animal. It will be understood that while  FIG. 2  shows this harness as neck collar comprising a simple strap  23  on the ends of which are provided a male buckle  25  and mating female buckle  24  of conventional design, the invention is not limited to any particular design of attachment. Many kinds of collars and harnesses are known to the art, the applicability of which depend upon the particular kind of animal to which the device  20  is to be attached. For example, while neck collars such as the one shown in  FIG. 2  are commonly used for dogs, especially larger dogs, it is not uncommon to use “H” type harnesses with cats or rabbits. Such harnesses which have one strap around the animal&#39;s neck and another around its body behind the front legs. Other harnesses, such as those which resemble zip-up jackets and which are commonly used with rabbits and small dogs, are also useful within the teachings of the invention. Alternatively, the animal-borne device can be implemented to be used with a pre-existing collar or harness, for example as a hanging pendant, or the animal-borne device can be embedded within a harness or collar. 
     The animal-borne device  20  provides a bi-directional link  21  to interrogate RFID tags  10 . The animal-borne device  20  can communicate with a computer  26  through a wireless link  22  or wired link  27 , so that the user can program the animal-borne device  20  as indicated below. The computer  26  can be a laptop computer as shown in the figure, or a desktop machine or tablet or smart phone, or any other device which would permit such communication. The wireless link  22  can be the common 802.11 WiFi system, BlueTooth Low Energy (BTLE), ZigBee, or any other wireless protocol which may at some point become preferred. The alternative wired link  27  can be USB, FireWire, Lightning, RS-232 serial, parallel, or any other type as desired. 
       FIG. 4  shows a more detailed block diagram of the animal-borne device  20 . The components which make up the animal-borne device  20  comprise a controller circuit  40  with memory  45 , an RFID interrogator/reader  41  with its antenna  43 , a communications link such as a wireless link circuit  48  with its antenna  49  or a wired connector  50  or both, an accelerometer or other motion detector  47 , an energy harvester  42 , a rechargeable battery  44  and an alarm  46 . Other components might be added within the teachings of the invention. 
     Controller circuit  40  is preferably a low-power “computer on a chip” in a single package, such as an ARM micro control unit made by Nuvotron. The controller  40  may include internal programmable read-only memory (PROM) to contain the basic programming. Additional nonvolatile memory  45 , which is preferably “flash” memory, is provided to store user information, for example the RFID identification information, as explained below. This memory  45  can be external to the controller  40  or it could be internal RAM or EPROM if such is provided in the processor chip. The controller  40  has at least one input coupled to the accelerometer  47 , at least one output coupled to the alarm  46 , and bidirectional input-output communications ports coupled to the RFID reader  41  and the wired connection  50  and/or wireless link  48 . 
     The animal-borne device  20  is preferably powered by rechargeable battery  44 , which can be any kind of rechargeable battery such as lithium-ion (LiOn), nickel-cadmium (NiCd), alkaline or other technologies as may become available. The battery  44  is preferably charged by a vibration energy harvester  42  that uses the motion of the pet as it walks or runs to generate electrical power. The energy harvester  42  can be of the same kind as used in “shake to charge” flashlights which operate by a moving magnet passing near a coil, or can be a compact device made by Precision Motors. 
     It will be understood, however, that within the teachings of the invention the animal-borne device  20  can alternatively be powered by expendable batteries, and if a rechargeable battery is used it could be recharged by a conventional battery charger instead of, or in addition to, the energy harvester  42 . 
     The RFID reader  41  generates an RF signal at a frequency appropriate to the RFID tags being used, and listens for replies from such RFID tags. As the pet approaches a restricted area, the RFID reader  41  will detect the presence of the RFID tag. When a reply is detected, the RFID reader  41  provides the identification number of the tag to the controller  40 . The RFID reader can be, for example, a fully integrated UHF reader chip made by Impinj in Seattle, Wash. The RFID reader  41  is preferably operated at a relatively low power level so that tag detection would happen at a relatively close range, preferably about 1 to 2 feet, although longer-range detection could be accomplished by using a higher power on the interrogation signal. 
     The RFID reader  41  preferably uses a dipole antenna  43  embedded in the harness or collar  23  that the pet wears, so long as the harness or collar is made of a non-electrically conductive material such as leather or plastic or webbing. The antenna  43  will preferably be made of flexible metal that retains its shape, such as beryllium copper or stainless steel. 
     The antenna design is shown in detail in  FIG. 5 , which shows an antenna  51  embedded in collar  52 , which would be attached around the pet&#39;s neck by buckles  55 . The collar  52  is made up of two layers of leather or webbing  53  and  54 , with the central portion of upper layer  53  being cut away to show the antenna  51  and the lower layer  54 . Similarly,  FIG. 8  shows an antenna  81  of another design attached to an “H” type harness  82 , which has a central strap  88  which would run along the pet&#39;s back or belly, fastened to the pet by straps  86  and  87  which attach around the pet&#39;s neck and chest, respectively, by buckles  85 . In  FIG. 8  the upper layer  83  of the harness  82  on straps  88  and  87  is cut back to show antenna  81  and lower layer  84 . 
     The antennas  51  or  81  are coupled by a thin coaxial cable to the RFID reader in the animal-borne device. The cable can be embedded in the collar  52  or harness  82 . 
     As discussed in connection with  FIG. 4 , above, the controller  40  can communicate with a user through a wired connector  50  or a wireless link through antenna  49  which is implemented through wireless controller circuit  48 . The wireless controller  48  can be a standard WiFi chip such as those made by Marvell or Realtek. If desired, the wired connector  50  can be configured to take power from the connecting device, for example a standard USB port, to charge the battery  44 . This would be desirable for the initial use of the system before the energy harvester  42  has time to charge the battery  44 , or if the animal-borne device  20  has not been used for a while and the battery  44  has discharged. 
     An accelerometer  47  is provided to detect acceleration and de-acceleration indicating that the pet is motion, as well as detecting orientation changes. Preferably, accelerometer  47  is a microelectromechanical system (MEMS) solid-state sensor, such as those made by Analog Devices which are used in devices such as Apple iPods® or smartphones to detect motion or orientation of the device. Using the data from the accelerometer  47 , the controller  40  can detect that the pet is standing and in motion, and can then turn on the RFID reader  41  to look for signals coming back from RFID tags. Similarly, when the data from the accelerometer  47  indicates that the pet is asleep or resting, lying down or otherwise motionless, the controller  40  can turn off the RFID reader  41 , thus conserving battery power. 
     During the times when the pet is active and walking around, the RFID reader  41  can be programmed to be on for, say, 50 ms and off for, say, 200 ms, knowing that the pet cannot travel very far in 200 ms. This will further conserve battery power and limit the amount of RF emissions generated by the device. When a forbidden tag is detected these times can be adjusted so the reader is on for a longer time period. 
     The alarm  46  is preferably an ultrasonic transducer, such as that made by Ceramic Transducer Design Company. The ultrasonic alarm  46  around the pet&#39;s neck, when activated by the controller  40 , will create an uncomfortable sound heard only by the pet, that will cause the pet to back away from the restricted area until the sound is no longer heard. It will be understood that other forms of alarm are possible, including the electrical shock system as used in prior art dog-training collars, in which an alarm activation would result in giving the pet a mild shock. 
     The operation of the system, with reference to the example of  FIG. 1  and the block diagrams of  FIGS. 2-4 , is as follows, with the number before each paragraph referring to the step numbers in the flowchart of  FIG. 6 :
       68 . Preparation Phase: The system is set up for use with the animal or animals whose access to the area(s) around the house is to be controlled.     51 . In preparation for implementing the system, the areas to which each animal is to be permitted, or from which it is to be excluded are determined. The family in the example is willing to allow the adult dog Snoopy  4  in the living room LR, dining room DR and kitchen K, but does not want him in the hall H leading to bedrooms BR 1 -BR 3 . The cat Fluffy  8  is allowed more or less free run, except she is not permitted in the kitchen K or the second bedroom BR 2  which is used as a computer room. The puppy Rex  6  is to be restricted to the third bedroom BR 3  and hall H, since he is not yet house-trained. Neither of the dogs  4  and  6  are allowed in the bathroom BT, or to leave either door  2  or  3 . The cat  8  has a litter box in the bathroom BT and cat flaps in doors  2  and  3 , so she is permitted access to these areas denied to the dogs  4  and  6 .     52 . RFID tags are placed around the house  1 , at least in the areas to which access is desired to be controlled. In the example shown in  FIG. 1 , tag  10   a  is at the front door  2 , tag  10   b  is in the living room LR, tag  10   c  is at the back door  3 , tag  10   d  is at the entrance to the kitchen K from dining room DR, tag  10   e  is where hall H enters dining room DR, tag  10   f  is in the bathroom, and tags  10   g  and  10   h  are in bedrooms BR 2  and BR 1 , respectively. For the purposes of this example, assume that the identification number of each tag is the same as its number in the  FIG. 10   a - 10   h ), although it will be understood that in practice an actual identification number of some sort would be supplied and marked on each tag. The identification number of each tag is noted by the user.   

     It should be noted that the previous two steps can be executed in either order, although it is preferred to first determine the areas to be controlled, since that can aid in deciding as to where to place the tags. Alternatively, tags can simply be placed at each room or area entrance or exterior doorway.
       53 . The permitted/excluded areas for each animal are associated with the RFID tags posted in each area, which would result in something like the following table:   

     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 programming chart 
               
             
          
           
               
                   
                   
                 Device 
                   
                   
               
               
                   
                 Animal 
                 No. 
                 Permitted tags 
                 Excluded tags 
               
               
                   
                   
               
               
                   
                 Snoopy (dog 4) 
                 5 
                 10b, 10d 
                 10a, 10c, 10e, 
               
               
                   
                   
                   
                   
                 10f, 10g, 10h 
               
               
                   
                 Fluffy (cat 8) 
                 9 
                 10a, 10b, 10c, 
                 10d, 10g 
               
               
                   
                   
                   
                 10e, 10f, 10h 
               
               
                   
                 Rex (puppy 6) 
                 7 
                 none 
                 10a, 10b, 10c, 
               
               
                   
                   
                   
                   
                 10d, 10e, 10f, 
               
               
                   
                   
                   
                   
                 10g, 10h 
               
               
                   
                   
               
             
          
         
       
     
     Alternatively, the user could tabulate the information by checking boxes or entering codes for each tag indicating if it marks an “excluded” area: 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 alternate programming chart 
               
             
          
           
               
                 Animal 
                 Dev. No. 
                 10a 
                 10b 
                 10c 
                 10d 
                 10e 
                 10f 
                 10g 
                 10h 
                 . . . 
                 10n 
               
               
                   
               
               
                 Snoopy 
                 5 
                 X 
                   
                 X 
                   
                 X 
                 X 
                 X 
                 X 
                   
                   
               
               
                 Fluffy 
                 9 
                   
                   
                   
                 X 
                   
                   
                 X 
               
               
                 Rex 
                 7 
                 X 
                 X 
                 X 
                 X 
                 X 
                 X 
                 X 
                 X 
               
               
                   
               
             
          
         
       
     
     In the alternative embodiment which uses machine-readable coded RFID tags, as shown in  FIG. 7  and discussed above, instead of having to manually enter a table of permitted/excluded areas, the step  53  of associating the tags with the animal would be done simply by scanning the code on each tag with a camera connected to the computer, for example by a camera built-in to a laptop, smartphone or tablet.
       54 . Using an application program loaded on their computer  26 , the user programs the animal-borne devices  5 ,  7  and  9 , in turn, by connecting the computer  26  to each of the animal-borne devices  5 ,  7  and  9 , via a wireless link  22  or wire  27 . The application program on the computer  26  uploads at least one of the lists of permitted tags or excluded tags to the controller  40  through the link  22  or  27 —if desired, both the list of permitted tags and excluded tags could be uploaded.     55 . The controller  40  in each device stores the list(s) in memory  45 . It will be understood that the animal-borne device  20  could be programmed to respond with an alarm either to reception of a tag which is on the excluded list or, conversely, a tag which is not on the permitted list, or even to both situations, which would determine which list (or both) would need to be uploaded and stored.   

     If there is more than one animal-borne device to be programmed, steps  54  and  55  are repeated for each device.
       56 . The animal-borne devices  5 ,  7  and  9 , are then affixed to the pets  4 ,  6  and  8 , respectively.     57 . Operation Phase: The system now begins to operate as a pet barrier. The following explanation will take Snoopy (dog  4 ) as the example, assuming that at this point he is in the living room LR as shown in  FIG. 1 , and explains the operation of his animal-borne device  5 .     58 . As Snoopy begins to move around, the accelerometer  47  detects the motion, communicating this to controller  40 .     59 . Controller  40  turns on the RFID reader  41 .     60 . RFID reader  41  sends out an RF signal through antenna  43  to interrogate any RFID tag within range.   

     Snoopy  4  walks toward the entrance to hall H. At some point the RFID reader  41  is close enough to activate tag  10   e , which responds with its identification number.
       61 . Tag  10   e &#39;s signal is in turn detected by the RFID reader  41  and . . . .     62 . . . . it is communicated to controller  40 .     63 . The controller  40  looks up the identification number in the memory  45 , and finds it is on the “excluded” list.     64 . Controller  40  activates the alarm  46 , which makes an ultrasonic sound which startles Snoopy  4 . He backs off from the tag  10   e.        65 . When the tag  10   e  is out of range, the RFID reader  41  stops receiving the identification, and communicates the cessation to controller  40  (or, alternatively, it stops sending the identification number to controller  40 , which is programmed to recognize this stop as meaning that the tag is no longer being received).     66 . The controller  40  turns off alarm  46 , to Snoopy&#39;s relief, and the method repeats from step  58 , checking for continued motion.   

     Snoopy now wanders over toward the kitchen K. At some point the RFID reader  41  is close enough to activate tag  10   d , which responds with its identification number.
       61 . Tag  10   d &#39;s identification number is detected by the RFID reader  41  and . . . .     62 . . . . communicated to controller  40 .     63 . Controller  40  looks up the identification number in the memory  45 , and finds it is on the “permitted” list, if there is one. Alternatively, if there is no “permitted” list, the controller  40  will find that  10   d  is not on the “excluded” list. In either case, this means that Snoopy is not in a “no go” area, and the alarm  46  is not turned on (or turned off, if it is on).   

     As Snoopy wanders around his permitted territory, his activity causes the energy harvester  42  to generate electricity, keeping the battery  44  charged, and the method repeats, with the controller  40  setting off the alarm  46  as he approaches tags  10   a ,  10   c  or  10   e , and doing nothing as he passes tags  10   b  or  10   d.    
     Finally, tired of his wandering, Snoopy lies down to take a nap. 
     
         
           58 . The accelerometer  47  detects the cessation of motion, as well as perhaps a change in orientation, and communicates this to controller  40 . 
           67 . Controller  40  accordingly turns off the RFID reader  41 , and the method repeats from step  58 . 
           58 . Controller  40  continues to monitor accelerometer  47  for data which once again detects motion. When the accelerometer  47  detects that Snoopy has started to move again, the controller  40  once again turns on the RFID reader  41 , and the method progresses to step  59 , etc. 
       
    
     It is possible within the teachings of the invention that the controller  40  can be programmed to recognize different kinds of motion, for example walking as opposed to rolling over in sleep, and to turn on the RFID reader  41  only for the kind of motion which indicates walking around. This would save battery life by preventing drain by the RFID reader  41  if the animal is just sleeping restlessly. Alternatively, the controller  40  could be programmed to turn on the RFID reader  41  on any detection of motion by the accelerometer, but turn off the RFID reader  41  if no further motion is detected after a determined period of time. During the times when the pet is active and walking around, the controller could also be programmed to turn RFID reader on and off in a cycle of, for example, 50 ms on and 200 ms off, knowing that the pet cannot travel very far in 200 ms. This will further conserve battery power and limit the amount of RF emissions generated by the device. When a forbidden tag is detected these cycle times can be adjusted so the reader is on continuously or for a longer time period. 
     Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.