Abstract:
An electronic apparatus ( 1 ) for training an animal is supported against the animal&#39;s skin, and includes stimulus electrodes ( 5 ) for electrically contacting the skin. A controller including output terminals producing aversive stimulus control signals, a first switch (Q 4 ) coupled to a winding to produce therein a burst of first current pulses in response to a first signal produced by the controller ( 33 ) and a second switch (Q 2 ) coupled to the first switch (Q 4 ) operative to synchronously shunt predetermined trailing portions of the first current pulses away from the winding in response to a second signal produced by the controller to reduce the amount of energy delivered to the winding by the switching transistor (Q 4 ) without substantially changing a peak value of a flyback voltage across the winding. The controller sets various values of time intervals during which portions of the first current pulses are shunted away from the winding in order to set various corresponding intensities of aversive stimulus.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates generally to electronic remote training collars and the like and also to collar-mounted electronic “bark limiter” or dog bark training devices, and more particularly to improvements therein which reduce the size, weight and power consumption thereof without reducing the open circuit stimulus voltage, allow convenient manual adjusting of stimulus levels, provide improved sensing of what constitutes valid barking, provide low-power standby operation when the dog is not barking, and allow monitoring of the amount of valid barking that actually occurs. 
   A variety of electronic dog training collars have been utilized for applying electrical shock and/or audible stimulus to a dog when it barks. In many situations it is highly desirable to prevent individual dogs or groups of dogs from barking excessively. For example, one dog&#39;s barking in a kennel is likely to stimulate other dogs to bark. This is undesirable with respect to the welfare of the dogs themselves and nearby people. Similar problems occur in neighborhoods in which there are dogs that are kept outside at night: if one dog starts barking others are likely to join in, causing a general disturbance. 
   The closest prior art is believed to include the present assignee&#39;s Bark Limiter product and commonly assigned U.S. Pat. No. 4,947,795 by G. Farkas entitled “Barking Control Device and Method”, issued Aug. 14, 1990 and incorporated herein by reference. U.S. Pat. No. 4,947,795 discloses a bark training device which allows a dog to control the level of electrical stimulus in response to its own barking behavior. This patent discloses circuitry in a collar-mounted electrical device that detects the onset of barking and initially produces only a single low level electrical stimulus pulse that gets the dog&#39;s attention, but does not initially produce a highly unpleasant level of stimulation. If the dog continues barking, the stimulation levels of the electrical shock pulses are increased at the onset of each barking episode in a stepwise fashion until the stimulus becomes so unpleasant that the dog stops barking for at least a predetermined time, e.g., one minute. After that minute elapses, the circuitry resets itself to its lowest initial stimultion level and remains inactive until barking begins again, and then repeats the process, beginning with the lowest level of stimulation and increasing the stimulus level if barking continues. In one embodiment, a certain duration, e.g., 30 seconds, of “watchdog barking” is permitted before the initial stimulus pulse is applied to get the dog&#39;s attention, after which continued “nuisance barking” results in gradual increasing in the intensity of the aversive stimulus up to a maximum level until the barking stops for at least one minute. However, the assignee&#39;s above mentioned Bark Limiter product does not use the algorithm described in U.S. Pat. No. 4,947,795 for producing increased stimulation in response to increased levels of barking, and instead provides a fixed duration stimulation with detection of an initial onset of barking, and provides a half second duration of stimulation with two seconds of pause, which is easily implemented and has been proven to be very effective. 
   The Tri-Tronics collar-mounted Bark Limiter product has been successfully marketed by the present assignee for many years. It has been very successful in the market because it effectively controls unwanted barking of large and medium-sized dogs. Its large size has allowed use of large batteries to power the circuitry that allows the Bark Limiter product to produce a substantial level of stimulation, which has been a major reason for the product&#39;s success. However, the large size and weight of the assignee&#39;s Bark Limiter product have limited it to use on medium-sized and large-sized dogs. Competitive products that have been smaller in size and weight and therefore have been usable on a small or tiny dogs have been introduced to the market, but their small size evidently has necessitated a substantial reduction in the level of stimulation that such products can produce in response to the dog&#39;s barking. 
   For many years, the present assignee has designed and marketed collar-mounted electronic dog training products which endeavor to keep the open circuit output voltage between the two stimulation electrodes at a high level in order to establish good electrode contact despite less than perfect electrical contact between the electrode contact area of one or both of the electrodes and the skin of the dog. This is explained, for example, in the assignee&#39;s U.S. Pat. No. 4,802,482 entitled “Method and Apparatus for Remote Control of Animal Training Stimulus” by Gonda et al., issued Feb. 7, 1989 and incorporated herein by reference. 
   Some of the assignee&#39;s prior collar-mounted dog training products have varied the intensity of electrical stimulation applied to the dog&#39;s neck by changing the widths of the current pulses driven through the primary winding of the output transformer. This causes the peak open circuit voltage produced between the stimulus electrodes driven by the secondary winding of the output transformer to vary as a function of the selected/desired stimulus intensity, and sometimes results in undesirably low open circuit voltages between the stimulus electrodes transformer. 
   A problem of the prior art has been that the effectiveness of coupling the electro-stimulus energy to the dog is reduced as the amount of RMS energy applied to the primary winding of the output transformer is reduced in order to reduce the stimulus intensity level. This reduces the reliability of the electrical contact between the stimulus electrodes and the skin of the dog&#39;s neck, and thereby reduces the effectiveness of the training or even causes the training to become counterproductive, and leads to over-tightening of collar straps by dog trainers and/or owners, which often causes chronic sores on the dog&#39;s neck. 
   Users of collar-mounted bark training products generally wish to be able to test such products by demonstrating their operability in response to a suitable sound or simulated bark signal. The assignee&#39;s prior Bark Limiter product has utilized test lights and an external tester that actuates its barking sound vibration sensor. Some of the prior art bark limiters have vibration sensors such as electret condenser microphones built into their housings between the stimulus electrodes. External buzzers have been used to stimulate the vibration sensor in order to test it and determine if the bark limiter is operative. 
   A shortcoming of the prior art bark training products is that they detect nearly any sound the dog makes and automatically shock the dog in response to the detected sound. The stimulation intensity can be changed only by removing the stimulation electrodes and replacing them with different stimulation electrodes having different series resistances. The battery life of some prior bark limiters has been undesirably short, especially because dog owners often find it convenient to leave the devices in a “power on” condition for long periods of time, even during times when the dog is not likely to be barking. 
   Another shortcoming of the larger prior art bark control devices is that they are too large to use on a small or tiny dog. 
   Yet another shortcoming of prior bark control devices is that occasionally when the dog scratches with its hind foot, it unintentionally contacts the power switch and turns off the power of the bark control device. The dog may learn that by “scratching” in a certain way it can turn the bark control device off. 
   Thus, there is an unmet need for an improved animal training device that provides a way of conveniently adjusting the level of the stimulation intensity applied to the animal. 
   There also is an unmet need for an improved animal training or bark control device that enables a user to readily determine which of various possible stimulation levels is presently selected. 
   There also is an unmet need for a small, lightweight electro-stimulus animal training device that despite its small size is nevertheless capable of providing a substantially larger open circuit output voltage that the prior small, lightweight electro-stimulus animal training devices. 
   There also is an unmet need for a small, lightweight bark control device that provides high open circuit output voltage over a wide range of low to high applied electrical stimulus levels. 
   There also is an unmet need for way of substantially reducing the power consumption of a animal training device. 
   There also is an unmet need for a small, lightweight, highly effective bark control device that is small and light enough to be readily worn by a small or tiny dog. 
   There also is an unmet need for an improved bark control device that avoids accidental stimulation of the dog in the event that the battery voltage is too low. 
   There also is an unmet need for an improved bark control device that cannot be accidentally or deliberately turned off by a dog&#39;s scratching activity. 
   There also is an unmet need for an improved collar-mounted animal training device that substantially reduces the occurrence and/or severity of neck sores on the animal wearing the device. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the invention to provide an improved animal training device that provides a way of conveniently adjusting the level of the stimulation intensity applied to the animal. 
   It is another object of the invention to provide a small, lightweight animal training device that despite its small size is nevertheless capable of providing large open circuit output voltage. 
   It is another object of the invention to provide a small, lightweight bark control device that provides high open circuit output voltage for a wide range of low to high electrical stimulus levels. 
   It is another object of the invention to provide a way of substantially reducing the power consumption of an animal training device. 
   It is another object of the invention to provide a small, lightweight, highly effective bark control device that can be worn by a small or tiny dog. 
   It is another object of the invention to provide an improved collar-mounted animal training device that substantially reduces the occurrence and/or severity of neck sores on the animal wearing the device. 
   It is another object of invention to provide an improved low power consumption bark control device including a switch and LED indicator arrangement that minimizes the possibility of water leakage into the housing of the bark control device. 
   It is another object of the invention to provide an improved bark control device that cannot be accidentally or deliberately turned off by a dog&#39;s scratching activity. 
   It is another object of the invention to provide an improved bark control device that avoids accidental stimulation of the dog caused by improper operation due to the battery voltage being too low. 
   Briefly described, and in accordance with one embodiment, the present invention provides an electronic apparatus ( 1 ) for training an animal, including a housing ( 2 ) supported against the animal&#39;s skin by a strap, first and second stimulus electrodes ( 5 ) extending from a surface ( 9 ) of the housing, a controller ( 33 ) in the housing having output terminals producing aversive stimulus control signals, first switch (Q 4 ) coupled to a winding to produce a burst of first current pulses in a winding in response to a first signal produced by the controller ( 33 ) and a second switch (Q 2 ) coupled to the first switch (Q 4 ) operative to synchronously shunt predetermined trailing portions of the first current pulses away from the winding in response to a second signal produced by the controller to reduce the amount of energy delivered to the winding by the switching transistor (Q 4 ) without substantially changing a peak value of a flyback voltage across the winding, the second signal including a burst of pulses synchronous with the burst of first current pulses. In the described embodiment, the winding is the primary winding of an output transformer having a secondary winding coupled between the first and second stimulus electrodes. 
   In the described embodiment, the controller executes a program to set various values of time intervals during which predetermined portions of the first current pulses are shunted away from the winding in order to set various corresponding intensities of aversive stimulus applied between the first and second stimulus electrodes. The controller sequentially increments values of the time intervals in response to sequential actuation of a single manual switch ( 17 ). 
   In one embodiment, the invention provides a collar-mounted electronic apparatus ( 1 ) for control of barking by a dog, including a housing ( 2 ) supported by a collar for attachment to the dog&#39;s neck, first and second stimulus electrodes ( 5 ) connected to a top surface ( 9 ) of the housing, a vibration sensor ( 6 ) supported by the housing for detecting vibrations caused by barking by the dog, a controller ( 33 ) in the housing having an input coupled to an output of the vibration sensor, the controller including output terminals producing aversive stimulus control signals in response to barking by the dog wherein a switching transistor (Q 4 ) is coupled to a winding of an output transformer ( 42 ) to produce a burst of first current pulses in the winding in response to a first signal produced by the controller ( 33 ) and a shunt transistor (Q 2 ) is coupled to the switching transistor (Q 4 ) to synchronously shunt predetermined trailing portions of the first current pulses away from the winding in response to a second signal produced by the controller to reduce the amount of energy delivered to the winding by the switching transistor (Q 4 ) without substantially changing a peak value of a flyback voltage across the winding. The second signal includes a burst of pulses synchronous with the burst of first current pulses. The second signal synchronously turns the shunt transistor (Q 2 ) on during a trailing portion of each first current pulse after a peak of the flyback voltage produced in response to the first current pulse, so the open circuit stimulus voltage produced between the first and second stimulus electrodes is relatively independent of the level of the first stimulation selected by means of a manual switch coupled to the controller. The controller sequentially sets desired stimulus intensity levels in response to sequential actuation of the membrane switch, causing the controller to also sequentially turned on, one at a time, selected stimulus intensity indicating light emitting diodes ( 10 ) visible through a sidewall of the housing. The controller operates to produce a delay in a leading edge of each pulse of the second signal in accordance with the selected desired stimulus intensity level in order to control the actual aversive stimulus intensity level. 
   In the described embodiment, the housing includes translucent material, and the collar-mounted electronic apparatus includes a reflector ( 20 ) disposed within the housing behind a plurality of stimulus intensity indicating light emitting diodes ( 10 ) to reflect and thereby intensify light emitted by the stimulus intensity indicating light emitting diodes and impinging on the housing so that light emitted by each stimulus intensity indicating light emitting diode passes through the housing and is easily visible from outside the housing. 
   In the described embodiment, the electronic apparatus includes neck motion sensing means coupled to the controller for enabling the controller to produce the first and second signals in response to a characteristic neck commotion of the dog during barking. 
   In the described embodiment, the electronic apparatus includes valid bark determination means in the controller for producing a frequency spectrum of vocalization by the dog and comparing the frequency spectrum with a predetermined valid bark frequency spectrum to determine if the vocalization constitutes a valid barking episode. The described embodiment of the electronic apparatus also includes means in the controller for establishing a low-power sleep mode during an interval of time during which no characteristic motion of the dog&#39;s neck is detected by the neck motion sensing means. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a collar-mounted bark limiter unit of the present invention with the collar removed. 
       FIG. 2  shows the a partially-exploded view of the bark limiter unit of  FIG. 1 . 
       FIG. 3A  is a perspective exploded view of the bark limiter unit of  FIGS. 1 and 2 . 
       FIG. 3B  is a side exploded view of the bark limiter unit as shown in  FIG. 3A . 
       FIG. 4A  is a perspective view of a LED lens reflector used within the housing of the bark limiter as shown in  FIGS. 3A and 3B  to provide a practical stimulation intensity indicator. 
       FIG. 4B  is an opposite perspective view of the LED lens reflector shown in  FIG. 4A . 
       FIG. 5  shows a section on view of a vibration sensor used in the embodiment as shown in  FIGS. 1A and 1B . 
       FIGS. 6-1  and  6 - 2  are a schematic diagram of the circuitry included in the housing of the bark limiter of  FIG. 1 . 
       FIG. 7A  is a diagram useful in explaining the waveforms of  FIGS. 7B–G . 
       FIG. 7B  is a timing diagram of the signals applied to switches SW 1  and SW 2  of the circuit of  FIG. 7A . 
       FIGS. 7C–G  are diagrams representative of the flyback voltages appearing on conductor  38  and the corresponding output signals applied via stimulus electrodes  5 A and  5 B to the skin of the dog&#39;s neck, represented by the load impedance Z L  in  FIG. 7A  in response to variations of the delay between the times Tb and Ta. 
       FIGS. 8-1  and  8 - 2  are a block diagram of the microcontroller  33  shown in  FIGS. 6-1  and  6 - 2 . 
       FIGS. 9A–E  constitute a flowchart of a group of programs executed by the microcontroller  33  included in  FIGS. 6-1  and  6 - 2 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   To summarize, a preferred embodiment of a dog bark limiter of the present invention provides convenient manual adjustability of the applied stimulus level to be applied to the neck of the dog by means of a switch. The bark limiter also includes low power circuitry that improves the electrical stimulation scheme to provide adequately high open circuit voltage between the stimulus electrodes in a small, lightweight collar-mounted animal training product at both high and low selected stimulus levels. The described bark limiter includes a motion detector that detects characteristic motion of the dog&#39;s neck produced as a result of barking and in response automatically powers up the circuitry from a very low power stand by operating condition. 
   A technique of “valid” bark detection using software wherein a capture and compare routine is executed in software executed by a microcontroller to accomplish the function of, in effect, generating a frequency spectrum of the received sound and comparing it with a predetermined frequency spectrum to determine if the sound constitutes a “valid” bark. A “bark counter” function is provided that counts the number of valid barking episodes by the dog. A self-test mode is provided to self-test or verify operability of the neck motion sensor and the sound vibration sensor. Whenever an electrical stimulus is applied to the dog&#39;s neck, then a 4 second “relaxation” delay is allowed to elapse before any further stimulus can be applied, in order to prevent a stimulus-caused barking cycle from being established. 
   Referring to  FIGS. 1 ,  2 ,  3 A and  3 B, bark limiter  1  includes a housing  2  having a lower section  2 A and an upper section  2 B. The top surface  9  of upper housing section  2 B is slightly concave, to better accommodate the curvature of a dog&#39;s neck. A pair of collar-retaining loops  3  are attached to opposite ends of upper housing section  2 B, as shown. A typical dog collar (not shown) is passed through loops  3  around the bottom surface of housing  2  to fasten bark limiter  1  to the dog&#39;s neck. Two stimulus electrodes  5  are threaded into receiving holes  8  ( FIG. 2 ) in the upper surface  9 , and their conductive tips are pressed against the dog&#39;s neck to make electrical contact therewith when the collar is tightened. As indicated in  FIG. 2 , stimulus electrodes  5  are removable. In accordance with one aspect of the present invention, a preferably non-conductive stabilizing post of the same height as stimulus electrodes  5  is rigidly attached to upper surface  9 , and is offset from a straight line between stimulus electrodes  5  so the stabilizing post  7  and the two stimulus electrodes  5  define a triangle. This prevents the conductive electrode tips of stimulus electrodes  5  from “rocking” against the dog&#39;s neck and avoids or at least reduces the occurrence and severity of sores on the dog&#39;s neck that are sometimes caused by the pressure of the stimulus electrodes against the dog&#39;s skin. The stabilizing post  7  in conjunction with the stimulus electrodes  5 B and  5 C provides stable contact of all three with the dog&#39;s neck and allows the direction of the collar to be reversed so that stabilizing post  7  and stimulus electrodes  5 B and  5 C make contact with different areas on the dog&#39;s neck, which reduces the occurrence and of and severity of neck sores. 
   A dome-shaped membrane  6  that preferably is integrally formed with the upper housing section  2 B is disposed on upper surface  9  and constitutes part of an improved vibration sensor  30 , which is subsequently described in more detail with reference to  FIG. 5 . A membrane switch  17  extends through an opening in upper surface  9 . The dog owner can repetitively depress membrane switch  17  to select one of five stimulus intensity levels. The selected intensity level is indicated by illumination of one of the five indicators identified by reference numeral  10 . Membrane switch  17  also can be depressed for a 4 second interval to set bark limiter  1  to a test mode, subsequently described. The above features, except the stimulus electrodes  5 B and  5 C, on the upper surface  9  of upper housing  2 B are all integrally formed as a single unit. 
   Referring to the exploded views of  FIGS. 3A and 3B , lower housing section  2 A is attached to upper housing section  2 B by means of two screws  12 . A printed circuit board  15 A contained within housing  2  is attached to upper housing section  2 B by means of two screws  16 . A 3 volt lithium battery  13  is attached to the bottom of printed circuit board  15 A by means of a pair of clips  14 . The membrane switch unit  17  is attached to the upper surface of printed circuit board  15 A and extends through a hole in upper surface  9 . A metal trace  17 A is contacted to provide a switch closure when the upper surface of membrane switch unit  17  is depressed. An output transformer  18 , a microcontroller  19 , and five light emitting diodes D 1 – 5  are mounted on the upper surface of printed circuit board  15 . As shown in  FIG. 3B , a piezoelectric transducer  21  is supported on output transformer  18 , and is contacted by a “nipple”  11  ( FIG. 5 ) formed on the underside of dome-shaped membrane  6 . Piezoelectric transducer  21  can be a Model P/N: 7BB-20-6 available from Murata Electronics North America, Inc. 
   The intensity indicators  10 - 1 , 2 , 3 , 4 , 5  become illuminated by light emitting diodes D 1 – 5 , respectively, as membrane switch  17  is successively depressed. An internal LED reflector element  20 , shown in  FIGS. 4A and 4B , is mounted on the upper surface of printed circuit board  15  so that the five recesses  25  thereof cover light emitting diodes D 1 – 5 , respectively. Notches  26  facilitate attachment of LED reflector  20  to printed circuit board  15 . LED reflector  20  allows the intensity indicators  10 , which appear as the numerals  1 – 5 , respectively, in  FIGS. 3A and 3B  on the front of upper housing section  2 B to be clearly illuminated through the thin side wall of upper housing  2 B to appear when the corresponding light emitting diodes D 1 – 5  are turned on. The five LEDs correspond to indicators  10 - 1 , 2 , 3 , 4 , 5  to indicate which stimulation level has been selected by means of the membrane switch  17 , and also indicate whether the bark limiter  1  is in a test mode. Holding switch membrane  17  depressed for 4 seconds sets the bark limiter  1  into its test mode, and the various LEDs D 1 – 5  blink, depending on the neck motion and barking by the dog. The LED corresponding to the intensity level selected by means of membrane switch  17  is the one which blinks. The arrangement of membrane switch  17  and the LED display arrangement including the lens reflector  20  minimizes the possibility of water leakage into the housing of the bark control device. 
   Referring to  FIG. 5 , the dome-shaped structure of acoustic membrane  6  and the location and structure of nipple  11  pressing against the central, most sensitive portion of the surface of piezoelectric transducer  21  are shown. 
   Referring to  FIGS. 6-1  and  6 - 2 , the circuitry of bark limiter  1  is provided on the upper surface of printed circuit board  15 A ( FIG. 3A ), and includes vibration sensor assembly  30  which includes above mentioned dome-shaped membrane  6 , piezoelectric transducer  21 , and the above-mentioned nipple  11  formed on the underside of membrane  6  in order to efficiently transmit vibrations from membrane  6  to piezoelectric transducer  21 . One of the electrodes of piezoelectric transducer  21  is connected to ground and the other is coupled by capacitor C 4  and resistor R 10  to the (−) input of an operational amplifier  31 . The (+) input of operational amplifier  31  is connected to the junction between resistor R 12  and resistor R 13 . The other terminal of resistor R 12  is connected to ground, and the other terminal of resistor R 13  is connected to one terminal of resistor R 4  and to the RA 0  input on lead  19  of microcontroller  33 . The other terminal of resistor R 4  is connected to the battery voltage VBAT. 
   The output of operational amplifier  31  is connected by conductor  32  to the RA 2  input on lead  1  of microcontroller  33  and also is connected to one terminal of capacitor C 2  and one terminal of resistor R 5 . The other terminals of resistors R 5  and capacitor C 2  are connected to the (−) input of operational amplifier  31 . The RA 2  input of microcontroller  33  is connected to one input of an internal comparator, the other input of which is connected to the RA 0  terminal of microcontroller  33 , in order to produce an internal square waveform to be used as an input to the internal microprocessor portion of microcontroller  33 , to allow the frequency of the square waveform to be determined. The capacitor C 2  functions as a low pass filter that sets the upper cutoff frequency of operational amplifier  31 . The resistors R 5  and R 10  to determine the gain of operational amplifier  31 . 
   Voltage monitor circuit  34  in  FIGS. 6-1  and  6 - 2  produces a low output voltage if VBAT is less than approximately 2 volts, and the junction between resistors R 3  and R 22 , which are coupled in series between VBAT and the output of voltage detector  34 , applies a reset signal to the microcontroller reset input MCLR on lead  4  thereof if VBAT is below approximately 2 volts. A resistor R 4 , in combination with resistors R 13  and R 12 , forms a threshold circuit that establish a threshold voltage to be applied to the internal comparator of microcontroller  33  via its RA 0  input. The output of the internal comparator of microcontroller  33  is produced on lead  2  of microcontroller  33 , which is externally connected to the CCP 1  input on lead  2  of microcontroller  33 . The CCP 1  input of microcontroller  33  is used in the subsequently described compare-capture mode of operation, to measure the periods of the square waveforms on the CCP 1  input. This allows the signals produced by vibration transducer  30  and amplified by operational amplifier  31  to be captured within an approximately 120 millisecond interval, and in effect, assembled into a frequency spectrum including sixteen 40 Hz windows in the range from 150 Hz to 800 Hz, which can be used to determine if the present sound is a valid bark. 
   Actuation of the motion sensor  40  in  FIGS. 6-1  and  6 - 2  results in a signal applied to lead  7  of microcontroller  33  to indicate whether the dog&#39;s present neck motion is of the kind characteristically caused by barking. Microprocessor  33  automatically switches from low-power standby operation at 37 kHz to normal operation at 4 MHz if this signal indicates that the dog has begun barking. 
   The RB 2 ,  4 ,  5 ,  6 , and  7  outputs of microcontroller  33  selectively turn on LEDs D 1 – 5 , respectively, in response to the pressing of membrane switch  17 . However, if microcontroller  33  is reset as a result of VBAT being less than 2.2 volts, microcontroller  33  produces high impedance outputs, and in that case, resistors R 23  and R 24  pull the gate voltages of MOSFETs Q 5  and Q 6  to VBAT thereby turn them on and allow the battery to discharge completely through light emitting diodes D 4  and D 5 , turning them both on until the battery is completely dead. If LEDs D 4  and D 5  emit light simultaneously, that indicates that the battery is discharged and needs to be replaced. 
   The RA 6  output on lead  17  of microcontroller  33  is coupled to the base of an NPN transistor Q 1  having its emitter connected to ground and its collector coupled by a resistor R 6  to the base of a PNP transistor Q 2  having its collector connected to VBAT and its emitter connected by conductor  38  to one terminal of the primary winding of output transformer  42 . The base of transistor Q 2  also is coupled by a resistor R 2  to VBAT. The RA 7  output on lead  18  of microcontroller  33  is coupled to the base of an NPN transistor Q 3  which has its collector coupled by resistor R 7  to VBAT and its emitter connected to the base of an NPN transistor Q 4 . The emitter of transistor Q 4  is connected to ground and its collector is connected to conductor  38 . The other terminal of the primary winding of output transformer  42  is connected to VBAT. The secondary winding terminals  5 B and  5 C are connected to the two stimulus electrodes  5 . 
   Transistor Q 4 , when turned on, produces a constant collector current for the entire amount of time that transistor Q 4  is turned on. If all of the collector current of transistor Q 4  flows through the primary winding of transformer  42 , that results in delivery of a maximum amount of energy to the primary winding of transformer  42  and therefore in a maximum amount output energy delivered to the stimulus electrodes  5  by the secondary winding of transformer  42 . However, if transistor Q 2  is turned on after the peak Vp of the flyback spike that occurs in the waveform of the voltage V 38  on conductor  38  immediately after transistor Q 4  is turned off, then some of the decaying current in the primary winding of transformer  42  is shunted, causing V 38  to rapidly fall to zero. This reduces the amount of energy delivered to the primary winding of transformer  42  for each pulse of the waveform V 39  applied to the base of transistor Q 4  by microcontroller  33 , and therefore also reduces the amount of stimulus energy delivered through stimulus electrodes  5  to the dog&#39;s neck. 
   Microcontroller  33  operates to produce a burst of pulses which are applied to the base of transistor Q 4  via the Darlington circuit configuration including transistor Q 3 . Each burst is approximately 0.5 seconds in duration, and each pulse width is approximately 0.9 to 1.0 milliseconds in duration. The intensity of the stimulation applied to the dog&#39;s neck is controlled by synchronously turning on shunt transistor Q 2  to divert a controlled amount of the collector current of transistor Q 4  away from the primary winding of transformer  42 . This approach has the advantage of shunting some of the current in the primary winding of transformer  42  after the peak of the flyback spike of V 38  through shunt transistor Q 2  to the battery supplying VBAT. During each turn-on pulse applied to the gate of MOSFET Q 4 , its drain current is constant, and the magnitude of that drain current is what determines the peak value of the flyback voltage on conductor  38  and consequently also mainly determines the open circuit voltage produced between stimulus electrodes  5  by the secondary winding of output transformer  42 . Since Q 2  is not turned on until after the peak of the flyback pulse of V 38 , the peak value of the flyback voltage pulse is substantially independent of the selected stimulus level, and therefore the desired large open circuit output voltage produced by transformer  42  also is substantially independent of the selected amount of stimulus energy to be applied via output transformer  42  to the animal&#39;s skin. 
   Referring to  FIG. 7A , in this diagram shunt transistor Q 2  is, for convenience, shown as a simple switch controlled by the Q 2  base drive signal V 37  and primary current transistor Q 4  which also is shown as a simple switch controlled by the Q 4  base drive signal V 39 . The impedance between stimulus electrodes  5 B and  5 C, including the impedance of the dog&#39;s neck and the contact resistances associated with the tips of electrodes  5 B and  5 C, is indicated by the impedance ZL. Referring to  FIG. 7B , the signal V 39  includes a burst of constant-width pulses generated by microcontroller  33 , and, for each pulse, turns transistor Q 4  on at a time Ta and turns transistor Q 4  at a time Tb. The signal V 37  includes a burst of variable width pulses, if desired, to control the amount of energy delivered to the primary winding of transformer  42  by operating shunt transistor Q 2  to shunt the primary winding during a selectable part of the decaying portion of the flyback spike of the voltage V 38  on conductor  38 . The pulse of V 37 , if present, turns primary winding switch transistor Q 2  on at a time Tc and turns it off at the following time Ta. 
     FIGS. 7C–G  show the characteristics of the transformer primary winding “flyback” voltage waveform produced on conductor  38  as a result of the combined operation of the shunt path circuitry including transistors Q 1  and Q 2  and the primary winding current circuitry including transistors Q 3  and Q 4  in response to microcontroller  33 . As shown in  FIGS. 7C–G , the peak voltage Vp of each flyback spike  50  of V 38  is relatively independent of whether shunt transistor Q 2  is not turned on in order to allow maximum energy to be delivered to the primary winding, and also is relatively independent of the amount of time that shunt transistor Q 2  is turned on after the peak of each flyback spike  50  in order to reduce the amount of energy delivered to the primary winding of output transformer  42 . The segments  50 D in  FIGS. 7D–G  indicate that turning on the shunt transistor Q 2  causes the subsequent portion of V 38  to rapidly fall to zero, thereby reducing the amount of energy delivered to the primary winding of transformer  42 , and therefore reducing the amount of energy delivered by the secondary winding to the dog&#39;s neck. 
   In  FIG. 7C , the steep leading edge of flyback spike  2  to the occurs when transistor Q 4  is turned off at time Tb. Shunt transistor Q 2  is not turned on, so portion  50 C of flyback spike  50  is allowed to decay all away to zero with no shunting, which corresponds to the maximum stimulus intensity setting. In  FIG. 7D , shunt transistor Q 2  is turned on at a time Tc equal to T1, which rapidly decreases V 38  to zero at time T1, so less energy is to delivered to the primary winding than in  FIG. 7C . In  FIG. 7E , shunt transistor Q 2  is turned on sooner than in  FIG. 7D , at time Tc equal to T2, so less energy is delivered to the primary winding than in  FIG. 7D . In  FIG. 7F , shunt transistor Q 2  is turned on sooner than in  FIG. 7E , at time Tc equal to T3, so less energy is the total delivered to the primary winding than in  FIG. 7E . In  FIG. 7G , shunt transistor Q 2  is turned on sooner than in  FIG. 7F , at time Tc equal to T4, so even less energy is delivered to the primary winding than in  FIG. 7F . 
   Thus, in one embodiment of the invention two control signals are in effect applied by microcontroller  33  to control the energizing of the primary winding of the output transformer, including the constant-width turn-on pulse signal applied to the gate of MOSFET Q 4  to establish the constant open circuit voltage produced between the stimulus electrodes, and also including a shunt control signal which controls the synchronous turn-on of shunt transistor Q 2  after the occurrence of the peak value of the flyback voltage on conductor  38  in order to control the amount of energy delivered to the primary winding of the transformer, and therefore the amount of RMS stimulus energy delivered the dog. This is in contrast to some of the assignee&#39;s prior collar-mounted electronic animal training devices and numerous other prior art animal training devices in which the desired stimulation intensity is varied only by changing the widths of the current pulses driven through the primary winding of the output transformer. 
   The microcontroller  33  used in the improved bark limiter  1  of the present invention preferably is a PIC16F628 available from Microchip Technology Incorporated, which includes several signal conditioning operational amplifiers, and operates so as to perform the same functions of executing the program represented by the flowchart of  FIGS. 9A–E . The details of microcontroller  33  are shown in  FIGS. 8-1  and  8 - 2 . As shown in  FIGS. 8-1  and  8 - 2 , microcontroller includes a flash memory  33 A, a random access memory  33 B for storing file registers, and a non-volatile EEPROM  33 C for storing the operating program and valid bark detection algorithms. Microcontroller  33  also includes the above-mentioned comparator  33 D which generates the signal Data In, and also includes a Vref circuit  33 E that produces 1 of 16 voltage levels provided as inputs to the comparator input if the comparator input is configured so that a Vref input is needed. 
   By way of definition, the terms “controller” and “micro-controller” are used herein is intended to encompass any microcontroller, digital signal processor (DSP), state machine, logic circuitry, and/or programmed logic array (PLA) that performs functions of microcontroller  33  as described above. 
   Motion sensor  40  can be a Model #SQ-SEN-001P Ultra Compact Tilt and Vibration Sensor, available from SignalQuest Inc. Motion sensor  40  is of a mechanical ball-in-tube construction, and includes a conductive ball that makes contact with appropriate electrodes in response to motion of the dog&#39;s neck in order to send the “wake-up” signal microcontroller  33 . Motion patterns that are characteristic of barking can be detected using motion detector  40 , and furthermore, a captured digitized barking or vocalization signal can be utilized to provide a frequency spectrum that represents a “valid” bark in order to provide more accurate bark detection that has previously been achieved. 
   The vibration detection operation, motion detection operation, and valid bark determination based on the frequency spectrum of the dog&#39;s vocalization are combined to determine whether an aversive stimulus signal should be produced between electrodes  5 B and  5 C. The motion detection is used primarily as part of detection of a valid bark, and is used secondarily to accomplish awakening bark limiter  1  from its sleep mode. Either the subsequently described “valid bark” detection based on the frequency spectrum of signals received from vibration sensor  30  or motion signals based on movement of motion detector  40  could be considered the primary bark detection function and the other could be considered to be the secondary bark detection function. The bark limiter could be awakened or powered up in response to barking, and the aversive stimulus could then be triggered by detection of neck motion, or vice versa. 
   Bark limiter  1  has an external power switch function that is performed by membrane switch  17 , and also can be automatically turned on or “awakened” by motion sensor  40  in response to the dog making the kind of characteristic head movement that corresponds to barking by the dog. Motion sensor  40  “wakes up” the bark limiter  1  from a low power stand by condition and stimulates microcontroller  33  to begin looking for a “valid” barking signal/sound. In the low power condition, microcontroller  33  runs at 37 kHz. Once it is awakened, microcontroller  33  runs at 37 kHz, and if any barking signals are detected, microcontroller  33  operates at 4 MHz to process that information, and then returns to a 37 kHz speed. 
   The ON mode includes both the SLEEP mode and the ES LEVEL CHANGE mode. The OFF mode allows the bark limiter  1  to be awakened as a result of a switch trigger signal produced by depressing switch  17 , and if that occurs, the program executed by microprocessor  33  checks to determine if switch  17  is depressed for least 0.1 seconds, and if it is not, automatically goes back into the SLEEP mode. If bark limiter  1  is in both the ON mode and the SLEEP mode, and a signal is received from motion sensor  40 , it immediately checks for a bark signal from vibration sensor  30  while microprocessor  33  is internally operating at 4 MHz, and if there is no bark signal from vibration sensor  30 , and the internal clock signal is reduced to 37 kHz, waits for a period of 2 seconds, and then reenters the SLEEP mode. Thus, a user can determine if bark limiter  1  is in its ON mode by subjecting bark limiter  1  to sufficient motion to cause motion sensor  40  to produce a motion signal and noticing if the light emitting diodes blink several times. 
   The two field effect transistors Q 5  and Q 6  connected in series with LEDs D 4  and D 5 , respectively, are used to indicate that the battery voltage is too low when the voltage monitor circuit produces a voltage below 2.2 volts. When the microcontroller  33  is reset, all of its outputs go to a high impedance state, and LEDs D 4  and D 5  are turned on. They continue drawing current until the battery is completely dead. Since the operation of the microcontroller is not assured for supply voltages below 2.2 volts, it is set to a “nonoperative”, high output impedance condition so to avoid any possibility of unintended stimulation of the dog if the battery voltage is too low. 
   The present invention provides an improved technique of bark detection with software by using the internal “Capture/Compare module” of the PIC16LF627 microcontroller  33  to determine what vocalization by the dog constitute “valid” barks. During a 120 ms (or similar) capture time interval, the periods of the various bark signal frequencies are measured and counted. A window of acceptable frequencies in the range of, for example, 150 Hz–800 Hz, is created by the software. This interval or “window” is divided into 16 “buckets” into which the counts of 16 evenly divided frequency ranges are stored. When a bark/sound signal is received, the periods of the bark frequencies are measured during the 120 ms capture interval. The period of the frequency component of the received bark/sound signal is measured, and if the measured period falls within one of the 16 buckets, i.e. frequency ranges, then a software counter assigned to that bucket is incremented. For each complete bark signal/sound captured, the counter totals are compared to predetermined threshold levels (representing a predetermined “valid bark” frequency spectrum) for each corresponding bucket, respectively in order to determine whether the bark/sound constitutes a “valid” bark. 
   A software “bark counter” is executed by microcontroller  33  to count the number of times the dog is stimulated in response to detection of a valid bark while bark limiter  1  is mounted on the dog. The bark counter contents can be determined by the trainer or dog owner when the collar is removed and turned off. The bark counter content is determined by counting the number of times the middle number three indicator LED  3  blinks after a switch  17  has been held pressed for more than 3 seconds. 
   The present invention also provides a lightweight bark limiter  1  in a small package which is usable on small dogs yet is capable of providing much higher stimulus levels than the small, lightweight bark limiting devices of the prior art. The membrane switch  17  allows convenient manual selection the stimulation level to be applied to dog&#39;s neck. 
   The internal reflector  20  allows the light emitted by the LEDs to effectively pass through the translucent housing material. This is to avoid the need to “light up” the entire housing and focuses the illumination on the windows for the intensity indicator LEDs avoids the need for the expense of placing the LEDs close to the edge of the housing and also avoids the need for the expense of providing thinner walled windows to be molded into the housing for the LED light to shine through. The combination of the translucent housing and the reflector lens  20  provides the substantial benefit of making it easier to make the entire bark limiter leakproof while also providing a convenient means for indicating its operating state or condition. 
   A 30 second interval is established when the desired electrical stimulus level is changed or if the bark limiter  1  is turned on. During the 30 second interval, the only thing that can happen is for the user to select the desired stimulus level or to turn bark limiter  1  off. During that 30 second interval the lights blink every second. If the user selects a particular stimulus level, it the 30 second timer is reset. 
     FIG. 9A  shows how bark limiter  1  is awakened from its “SLEEP” mode in response to a motion-indicating interrupt signal from motion detector  40 . If a motion signal is received by microcontroller  33 , the program goes from decision block  71  to block  75  and checks to determine if any signal is being received on conductor  32  in response to vibration sensor  30 . In decision block  76 , the program executes the subroutine of  FIG. 9C  to determine if the spectrum of sound signals received from vibration sensor  30  is the spectrum of a “valid bark”. If this determination is affirmative, the program goes to the routine of  FIG. 9B  to generate an aversive electrical stimulus (E.S.) signal between stimulation electrodes  5 B and  5 C. 
   Referring to  FIG. 9B , in block  51  the program executed by microcontroller  33  determines the selected stimulation level, i.e., determines the electrical stimulus time delay value that results in one of the waveforms shown in  FIGS. 7C–G  that has been set by means of switch  17  and stores it in the non-volatile memory  33 E ( FIGS. 8-1  and  8 - 2 ). As indicated in block  52 , microcontroller  33  sets V 37  and V 39  to high levels in block  52  in order to switch on the primary winding current in transformer  42 , and then in block  53  starts a software timer “ES (electro-stimulus) Timer” to the value “E.S. Time Delay” determined in block  51 . The program then goes to decision block  54  and continues to “loop” as long as the count of “ES Timer” of block  53  has a value less than “E.S. Time Delay”. After the selected time delay interval has elapsed, the program goes to block  55 B and sets the signal RA 7  on lead  18  of microcontroller  33  to a low level, which causes V 39  to go to a low level and causes the flyback transition  50 B of  FIGS. 7A–G  to occur. After a delay Tc has elapsed, as indicated in decision block  55 A, the program sets the level RA 7  on lead  18  of microcontroller  33  to a high-level, V 37  to a low level, and turns transistor Q 2  on. Every stimulation pulse produced by microcontroller  33  on the base of transistor Q 3  has a duration of 3.2 milliseconds. For every stimulus signal produced by microcontroller  33 , block  56  of the program of  FIG. 9B  causes the stimulus output signal produced by microcontroller  33  on its lead  2  to be at a low level until the 3.2 milliseconds has elapsed. 
   The program then goes to decision block  57  and determines if the number of stimulus pulses produced by microcontroller  33  is less than or equal to 160 (which corresponds to approximately half a second of electrical stimulation applied between electrodes  5 B and  5 C), and if that determination is affirmative, the program goes back to the entry point of block  52  and continues to repeat the foregoing sequence until a negative decision is made in block  57 . The program then increments the software bark counter, as indicated in block  57 A, and then goes to block  58  and then, as indicated in block  58 , starts a 4 second panic guard routine to prevent “panic barking” that can be caused by the electrical stimulus experienced by the dog, and then the program causes microcontroller  33  to go into its sleep mode, as indicated in block  59 . 
   Referring again to  FIG. 9A , if the decision of block  76  is that no valid bark is occurring, the program goes to block  77  and causes the LED corresponding to the selected stimulation level to flash twice, and then goes to decision block  78  and determines if a signal from motion detector  40  indicates that a significant neck motion is occurring. If this determination is affirmative, the program returns to the entry point of block  75  to determine if a bark signal is being received from vibration sensor  30 . If the determination of block  78  is negative, the program goes to blocks  79  and  80  and determines if a 2 second interval elapses without neck motion being detected, and if this happens, the program causes microcontroller  33  to go into its sleep mode, as indicated in block  81 . 
   If the determination of decision block  71  is negative, the program goes to decision block  72  and determines if switch  17  is depressed. If switch  17  is not depressed, the program causes microcontroller  33  to go into its sleep mode. If decision block  72  determines that switch  17  is depressed, the program responds in block  74  by determining and storing the new desired stimulus level established by repetitive depressing of switch  17 . Specifically, in block  74  the program determines if switch  17  is depressed for more than 1 second, and if this is the case, increments the stimulation level setting from the present level setting (1–5) to the next level setting and saves the new stimulus level setting. 
   The routine performed in decision block  76  of  FIG. 9A  is shown in  FIG. 9C . Referring to  FIG. 9C , in block  190  the program switches the internal oscillator clock frequency of microcontroller  33  from 37 kHz to 4 MHz and then goes to block  191  and starts a 120 millisecond timer, to create a 120 millisecond window within which a “valid bark”, if present, is to be “captured”. The program then goes to decision block  192  and tests the output of the 120 millisecond timer, and after the 120 millisecond window elapses, the program goes to block  192 A and runs a subroutine to determine if the vocalization detected is a valid bark. This is accomplished by comparing the number of times the frequency of the detected vocalization is captured in each frequency range or “bucket” within the 120 millisecond window with a predetermined number of times for each bucket of a known “valid bark” frequency spectrum. The program then goes to block  193  and switches the internal oscillator clock frequency of microcontroller  33  back to 37 kHz to provide low power ON mode operation. The program then returns to the entry point of decision block  76  of  FIG. 9A . If block  192  determines that the 120 milliseconds timer is still counting, the program then goes to decision block  195  and determines if there is a change in the level of the signal on leads  2  and  10  of microcontroller  33  to indicate that a pulse is present. If this determination is negative, the program reenters the entry point of decision block  192 , but if the presence of the pulse is detected, the program goes to block  196  and measures the duration of the pulse, and in block  197  increments the frequency spectrum “bucket” or counter which corresponds to the period (i.e., frequency) measured in block  196 . The program then reenters decision block  192  and continues the process until the 120 millisecond timer elapses. The pulse referred to is generated on lead  2  of microcontroller  33  from an internal comparator therein and is provided as an input to lead  10  of microcontroller  33 , which is the “capture and compare” (CCP 1 ) input of microcontroller  33 , and automatically starts a timer at the beginning of the pulse and stops the timer at the end of the pulse, so the frequency of the signal coming from vibration sensor  30  is thereby determined and can be used to select the appropriate frequency spectrum bucket to be incremented in order to acquire the frequency spectrum of the present bark signals received from vibration sensor  30  by one input of the internal comparator referred to. Lead  2  of microcontroller  33  is the output of that comparator. The reference applied to the other input of the internal comparator is established by the voltage on lead  19  by the resistive voltage divider circuitry shown in  FIGS. 6-1  and  6 - 2 . 
   Whenever bark limiter  1  enters the ON mode, it checks for neck motion, and if neck motion is detected, the program executed by microcontroller  33  checks for a valid bark. If there is neck motion but no valid bark, the program checks for incrementing of the selected stimulus level by means of switch  17 . If no incrementing of the stimulus level by means of switch  17  is occurring, the program causes bark limiter  1  to go into the SLEEP mode. 
   Note that the OFF mode of bark limiter  1  is different than the above-mentioned SLEEP mode. In the OFF mode, the program checks only to determine if membrane switch  17  is being depressed to turn bark limiter  1  on. The OFF mode only serves as a mode that will be mostly the same as the SLEEP mode, in order to conserve battery life and also in order to allow bark limiter  1  to be removed from an animal in such a way that the motion sensor does not initiate an ON mode. The OFF mode also can be used as a safety feature, in the sense that bark limiter  1  can be turned off when the collar strap is being adjusted or when the bark limiter  1  is being put on or removed from the dog so that there will be no possibility of electrical stimulus being accidentally applied to the dog. 
   Referring to  FIG. 9D , assuming that bark limiter  1  is in its OFF mode as indicated in block  140 , the program enters decision block  141  and determines if switch  17  has been pressed, and if this determination is negative, the bark limiter remains in its OFF mode. If switch  17  is pressed, decision block  141  causes the program to enter decision block  142  to determine if switch  17  has been depressed for more than 100 milliseconds, and if this determination is negative, bark limiter  1  remains its OFF mode. After switch  17  has been held depressed for more than 100 milliseconds, the program goes to decision block  143  and determines if switch  17  has been depressed for less than four seconds, and if this determination is negative, the program sets bark limiter  1  to its TEST mode and executes blocks  144  through  168 , as subsequently explained. However, if switch  17  has been depressed for less than four seconds, the program goes to block  145  and starts a 30 second delay time with the electro-stimulus capability of bark limiter  1  disabled. The program then goes to decision block  148  and sets bark limiter  1  to its ON mode. 
   In block  144 , the program goes into its “TEST” mode, and that condition is indicated by LEDs  1 – 5  sequentially turning on and off so as to “sweep” in a sequence that indicates initiation of the self-test mode. The program then starts a 15 second timer, as indicated in block  165 , and then goes to decision block  166  which detects whether the 15 second timer has elapsed, in which case bark limiter  1  is put into its ON mode, as indicated in block  148 . If the 15 second timer has not elapsed, then the program goes to decision block  167  and determines if any signal is being produced by vibration sensor  30 , and if this determination is negative, the program reenters decision block  166 . If a signal is being received from vibration sensor  30 , the program goes to block  168  and flashes LED  3  for 100 milliseconds, and then reenters decision block  166 . Self-testing can be accomplished by scratching membrane  6  ( FIG. 1 ) vibration sensor  30  during the 15 second duration of the test mode in order to cause LED  13  to flash in block  168 , proving the operability of vibration sensor  30 . 
   Referring to  FIG. 9E , after a back and forth sweeping pattern of the illumination by light emitting diodes  1 – 5 , different than their sweeping pattern of illumination for initiation of the test mode, to indicate that bark limiter  1  is about to enter its OFF mode, the program then goes to block  161  and causes LED D-3 to flash a number of times equal to the cumulative count in the bark counter to indicate how many stimulation episodes have occurred and resulted in incrementing the stimulation counter referred to in block  57 A in  FIG. 9B . 
   While the invention has been described with reference to several particular embodiments thereof, those skilled in the art will be able to make the various modifications to the described embodiments of the invention without departing from its true spirit and scope. It is intended that all elements or steps which are insubstantially different from those recited in the claims but perform substantially the same functions, respectively, in substantially the same way to achieve the same result as what is claimed are within the scope of the invention. 
   For example, a tapped transformer could be utilized and part of the primary winding current could be shunted through the secondary winding, for example, by providing a tap on the primary winding and shunting the primary winding through that tap instead of through the main terminal of the primary winding. Alternatively, another winding could be provided with a stimulation level control current in the direction opposite to the direction of the main primary winding current so as to effectively cancel part of the primary winding current. Another possibility for controlling current induced into the secondary winding after the peak flyback voltage of the primary winding would be to use a relay instead of transistor Q 2  to shunt current from the primary winding.