Abstract:
An automated or semi-automated defibrillator (AED) automatically turns on when an operator removes it from a storage location. This automatic activation often decreases the time it takes the operator—particularly an inexperienced or anxious operator—to set up and use the AED to resuscitate a patient in cardiac arrest. Furthermore, the AED can be designed to automatically turn off when the operator returns it to the storage location.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates generally to a medical device such as an automated or semi-automated external defibrillator (AED), and more particularly to a defibrillator that can turn on, turn off, or turn both on and off automatically, a case for storing the defibrillator, a system that includes the defibrillator and the case, and related methods.  
         BACKGROUND OF THE INVENTION  
         [0002]    AEDs have saved the lives of many patients who have suffered cardiac arrest in non-hospital settings, and, as a result of advances in AED technology, the number of lives saved per year is rising. An AED is a battery-operated device that analyzes a patient&#39;s heart rhythm, and, if appropriate, administers an electrical shock (automated) or instructs an operator to administer an electrical shock (semi-automated) to the patient via electrode pads. For example, such a shock can often revive a patient who is experiencing ventricular fibrillation (VF).  
           [0003]    Because cardiac arrest can cause permanent damage or death within a short time if left untreated, an AED operator should be able to set up and activate an AED within seconds after the operator arrives at the scene. Statistically, for each minute that the patient is in cardiac arrest and is not receiving cardiopulmonary resuscitation (CPR), his chance of survival decreases by 10%. And in most cases, there is no chance for resuscitation after 10 minutes. Unfortunately, many people do not know how to administer CPR. And, even in the best of circumstances, it can take a few minutes to retrieve the AED and a few additional minutes for the AED to diagnose and shock the patient. Therefore, even if the patient is discovered immediately, the operator often has little time to set up and activate the AED without further decreasing the patient&#39;s chance of survival. Clearly, the faster the operator can activate and set up the AED, the better the chances that the patient will survive.  
           [0004]    Unfortunately, with the continued proliferation of easily accessed AEDs, it is increasingly likely that an operator will have little or no experience using a particular brand of AED and/or may panic during a resuscitation attempt, and thus may waste valuable seconds trying to figure out how to turn on, i.e., activate, an AED. Although an entity such as an airline may provide AEDs in its places of business and train its employees to operate them, an employee typically uses these AEDs so infrequently that his skills may become “rusty” even if the entity offers periodic refresher courses. Furthermore, non-employees such as airline passengers may have no formal training in the use of an AED; consequently, the first time that such a person operates an AED may be during a resuscitation attempt. Now although an AED will often “walk” an operator through the steps of resuscitation once the AED is activated, the operator typically must determine how to activate the AED on his own. Unfortunately, the operator&#39;s “rustiness” or lack of training coupled with the anxiety induced by the resuscitation effort may make it difficult for the operator to determine how to activate the AED. Furthermore, the label of the AED&#39;s on/off switch may be confusing to the operator, and thus may exacerbate his difficulty in determining how to activate the AED. For example, the on/off switch may use a “1” to indicate “on”, and a “0” to indicate “off.” But although “1” and “0” are touted as being “universal” on and off symbols, respectively, they are often unrecognizable to an operator without electronics or computer experience. And although the AED may use the words “on” and “off” or their non-English equivalents to label the switch, these words may be unrecognizable to an operator who speaks another language or may be difficult to see under non-optimal lighting conditions.  
           [0005]    General Overview of an AED  
           [0006]    [0006]FIG. 1 is a perspective view of a conventional AED system  10 , which includes an AED  12  for generating a defibrillation shock and defibrillator electrode pads  14   a  and  14   b  for providing the shock to a patient (not shown). A connector  16  couples the electrode pads  14   a  and  14   b  to a receptacle  18  of the AED  12 . Typically, the electrode pads  14   a  and  14   b  are sealed within a package (not shown) that an operator (hands shown in FIG. 1) tears or peels open to access the electrode pads  14   a  and  14   b . The package acts as a moisture barrier that prevents the electrode-pad contact gel (not shown) from prematurely drying out during storage of the electrode pads  14   a  and  14   b . A battery  19 , which typically is a lithium-based battery, can provide relatively high power so that the AED  12  can quickly generate the defibrillation shock. The battery  19  and AED  12  may be stored separately, with the operator connecting the battery  19  to the AED  12  just prior to use in an emergency. Or preferably, the battery  19  and AED  12  may be stored together, with the battery  19  connected to the AED  12  during storage. For example, the battery  19  is often disposed inside of the AED  12  until it needs to be replaced.  
           [0007]    The AED  12  includes a housing  21 , a main on/off switch  20 , a display  22  for displaying operator instructions, cardiac waveforms, or other information, a speaker  24  for providing audible operator instructions or other information, status light-emitting diodes (LEDs)  26 , a status indicator  28 , and a shock button  30 , which the operator presses to deliver a shock to the patient (not shown). The AED  12  may also include a microphone  32  for recording the operator&#39;s voice and other audible sounds that occur during the rescue, and non-volatile memory such as a data card  34  for storing these sounds along with the patient&#39;s ECG and a record of AED events for later study.  
           [0008]    Still referring to FIG. 1, during an emergency where it is determined that the patient (not shown) may need a shock, the operator retrieves the AED  12 , then presses the on/off switch  22  to activate the AED  12 . Once activated, the AED  12  displays instructions on the display  24  and/or “speaks” instructions via the speaker  26 . Following these instructions, the operator removes the electrode pads  14   a  and  14   b  from the protective package (not shown) and inserts the connector  16  into the receptacle  18 . Then, the operator places the electrode pads  14   a  and  14   b  on the patient in the respective positions shown in the pictures on the pads and on the AED  12 . After the operator places the electrode pads  14   a  and  14   b  on the patient, the AED  12  analyzes the patient&#39;s ECG to determine whether the patient is suffering from a shockable heart rhythm. If the AED  12  determines that the patient is suffering from a shockable heart rhythm, then it instructs the operator to depress the shock button  30  to deliver a shock to the patient.  
           [0009]    Conversely, if the AED  12  determines that the patient is not suffering from a shockable heart rhythm, it informs the operator to seek appropriate non-shock treatment for the patient and disables the shock button  30  so that even if the operator presses the button  30 , the AED  12  does not shock the patient.  
           [0010]    As discussed above, the operator&#39;s inexperience, anxiety, and/or his inability to read the label of the switch  20  may delay the activation, and thus the set up and use, of the AED  12 . Unfortunately, this delay may reduce the patient&#39;s chance of survival by increasing the time that he is in cardiac arrest.  
           [0011]    Consequently, a need exists for an AED that activates automatically when needed to resuscitate a patient.  
         SUMMARY OF THE INVENTION  
         [0012]    In one embodiment of the invention, a defibrillator includes a housing and an activator disposed or attached to the housing. The activator activates the defibrillator when the housing moves from a predetermined location.  
           [0013]    Such a defibrillator can be designed such that it activates automatically when an operator removes it from a storage location. This automatic activation often decreases the time it takes the operator—particularly an inexperienced or anxious operator—to set up and use the AED, and thus often increases a patient&#39;s chance of survival by reducing the time that he is in cardiac arrest.  
           [0014]    In another embodiment of the invention, a defibrillator includes a housing and a deactivator disposed or attached to the housing. The deactivator deactivates the defibrillator when the housing is disposed in a predetermined location.  
           [0015]    Such a defibrillator can be designed such that it deactivates automatically when an operator returns it to a storage location.  
           [0016]    In yet another embodiment of the invention, a defibrillator includes a housing and an activator/deactivator disposed or attached to the housing. The activator/deactivator activates the defibrillator when the housing moves from a predetermined location and deactivates the defibrillator when the housing is disposed in the predetermine location.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a perspective view of a conventional AED system.  
         [0018]    [0018]FIG. 2 is a perspective view of an AED system that includes an automatically activating/deactivating AED according to an embodiment of the invention.  
         [0019]    [0019]FIG. 3 is a perspective view of an alternative embodiment of the AED system of FIG. 2.  
         [0020]    [0020]FIG. 4 is a perspective view of an AED system that includes an automatically activating/deactivating AED according to another embodiment of the invention.  
         [0021]    [0021]FIG. 5 is a diagram of an automatic on/off switch that can be used in the AED of FIG. 4.  
         [0022]    [0022]FIG. 6 is a perspective view of an AED system that includes an automatically activating/deactivating AED according to another embodiment of the invention.  
         [0023]    [0023]FIG. 7 is a perspective view of an AED system that includes an automatically activating/deactivating AED according to an embodiment of the invention.  
         [0024]    [0024]FIG. 8 is a perspective view of an AED system that includes an automatically activating/deactivating AED according to another embodiment of the invention.  
         [0025]    [0025]FIG. 9 is a block diagram of an AED circuit that the AEDs of FIGS.  2 - 4  and  6 - 8  can incorporate according to an embodiment of the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]    The following discussion is presented to enable a person skilled in the art to make and use the invention. Various modifications to the embodiments will be readily apparent to those skilled in the art, and the generic principles herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention as defined by the appended claims. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.  
         [0027]    [0027]FIG. 2 is a perspective view of an AED system  40  that includes an automatically activating/deactivating AED  42  and an AED storage case  44  according to an embodiment of the invention. For clarity, like numerals in FIGS. 1 and 2 refer to like elements in the systems  10  and  40 , and the pads  14   a  and  14   b  are omitted from FIG. 2. The AED  42  and case  44  are constructed such that when the AED is in an automatic mode and an operator (hand shown in FIG. 2) removes the AED  42  from the case  44 , the AED activates without further operator action. That is, when the AED  42  is in the automatic mode, merely removing the AED  42  from the case  44  automatically turns the AED “on”. Conversely, when the AED  42  is in the automatic mode and the operator returns the AED  42  to the case  44 , the AED deactivates without further operator action. That is, when the AED  42  is in the automatic mode, merely returning the AED  42  to the case  44  automatically turns the AED “off”.  
         [0028]    The AED  42  includes a manual three-position power switch  46 . When the switch  46  is in its “on” and “off” positions, the AED  42  is active or inactive, respectively, regardless of its location. But when the switch  46  is in the “auto” position, the AED  42  is active while out of the case  44  and is inactive while in the case as discussed above and below.  
         [0029]    The AED  42  also includes an activator/deactivator  48 , such as a conventional Hall-effect or magnetic-reed switch circuit. When the switch  46  is in its “on” and “off” positions, the activator/deactivator  48  has no affect on the operation of the AED  42 . But when the switch  46  is in its “auto” position, the activator/deactivator  48  deactivates circuitry (FIG. 9) within the AED in the presence of a magnetic field, and activates the circuitry in the absence of a magnetic field. Although the activator/deactivator  48  may be located anywhere within or on the AED  42 , it is typically located near a side of the AED so that it can more easily sense a magnetic field that is generated by the case  44  as discussed below.  
         [0030]    The storage case  44  includes a deactivator element  50 , walls  52  and a back  54  that define an AED-storage compartment  56 , and an opening  58  that allows the operator to grasp and remove the AED  42  from the storage compartment. The element  50 , which may be a conventional magnet, generates a magnetic field that causes the activator/deactivator  48  to deactivate the AED circuitry (FIG. 9) when the AED  42  is disposed within the case  44 . Although the element  50  may be located anywhere within or on the case  44 , it is typically disposed within or on a wall  52  or the back  54  such that it is adjacent to the activator/deactivator  48  when the AED  42  is disposed within the case. This adjacent location allows the activator/deactivator  48  to better sense the magnetic field that the element  50  generates. Furthermore, although the walls  52  and back  54  are shown as being rigid, they may be flexible, such as where the case  44  is a zippered fabric case (not shown). Moreover, the case  44  may include conventional protrusions or other means (not shown) for securing the AED  42  within the case  44 .  
         [0031]    Still referring to FIG. 2, the operation of the system  40  in manual and automatic modes is discussed according to an embodiment of the invention.  
         [0032]    In the manual mode, the AED  42  is stored in the case  44  with the switch  46  in the “off” position, which effectively bypasses the activator/deactivator  48 . During a cardiac emergency, the operator removes the AED  42  from the case  44 . Because the switch  46  is in the “off” position, the AED  42  does not turn on automatically. Therefore, the operator turns the switch  46  to the “on” position to activate the AED  42 , and then sets up the AED and uses the AED to shock a patient (not shown) as discussed above in conjunction with FIG. 1. Alternatively, as discussed below, the operator may turn the switch from “off” to “auto”, and, as long as the AED  42  is out of the case  44 , the AED will operate as if the switch were in the “on” position. At the end of the resuscitation effort, the operator returns the switch  46  to the “off” position to maintain the AED  42  in the manual mode, or turns the switch  46  to the “auto” position (if not already this) to put the AED in the automatic mode, which is discussed below. Because the operator must turn the key from “off” to “on” or “auto” to activate the AED  42 , the manual mode is intended for settings where the operator is likely to be thoroughly trained in the use of the AED system  40 .  
         [0033]    In the automatic mode, the AED  42  is stored in the case  44  with the switch  46  in the “auto” position, which allows the activator/deactivator  48  to control the on/off function of the AED.  
         [0034]    During a cardiac emergency, the operator removes the AED  42  from the case  44 . Because the switch  46  is in the “auto” position, the AED  42  turns on automatically, thus eliminating the need for the operator to manually turn the switch  46  to the “on” or “auto” position. Specifically, as the AED  42 , and thus the activator/deactivator  48 , moves a predetermined distance from the case  44 , and thus from the element  50 , the activator/deactivator senses a weakening magnetic field from the element. When the strength of this magnetic field falls below a predetermined threshold, the activator/deactivator  48  turns on the AED  42 . In one embodiment, the sensitivity of the activator/deactivator  48  and the magnetic-field strength of the element  50  are chosen such that the activator/deactivator activates the AED  42  when the AED is more than an inch or two from the case  44 . Once the AED  42  is activated, the operator sets up the AED and uses it to shock a patient (not shown) as discussed above in conjunction with FIG. 1.  
         [0035]    After the operator finishes treating the patient with the AED  42 , he returns it to the case  44 . Because the switch  46  is in the “auto” position, the AED  42  turns off automatically, thus eliminating the need for the operator to manually turn the switch  46  to the “off” position. Specifically, as the AED  42 , and thus the activator/deactivator  48 , move within a predetermined distance of the case  44 , and thus the element  50 , the activator/deactivator senses a strengthening magnetic field from the element. When the strength of this magnetic field at the activator/deactivator  48  rises above the predetermined threshold, the activator/deactivator turns off the AED  42 .  
         [0036]    Other embodiments of the AED system  40  are contemplated as well. For example, the switch  46  may be omitted such that the AED  42  operates only in the automatic mode. Alternatively, one can program the operating mode of the AED  42  via a personal computer and interface (not shown) or via the screen  22 . In such embodiments, when the AED  42  is in the automatic mode, one can attach a magnet to the AED near the activator/deactivator  48  to turn the AED off when it is out of the case  44 .  
         [0037]    [0037]FIG. 3 is a perspective view of an alternate embodiment of the AED system  40  according to an embodiment of the invention. The AED system  40  of FIG. 3 is the same as the system  40  of FIG. 2 except that the case  44  includes multiple deactivator elements, here four elements  50   a - 50   d . Including multiple elements  50  insures that the activator/deactivator  48  will turn off the AED  42  regardless of how the AED is positioned within the case  44 . For example, the operator may place the AED  42  upside down in the case  44 . But although the activator/deactivator  48  is no longer adjacent to the element  50   a , it is adjacent to the element  50   c . Consequently, the element  50   c  is close enough to cause the activator/deactivator  48  to deactivate the AED  42 .  
         [0038]    In another embodiment, the case  44  includes only one element  50 , for example element  50   a , that generates a magnetic field strong enough to cause the activator/deactivator  48  to deactivate the AED  42  regardless of its position within the case.  
         [0039]    Still referring to FIG. 3, in yet another embodiment, the AED  42  includes multiple activators/deactivators  48  (only one shown in FIG. 3) that each correspond to a respective one of the elements  50 . That is, each of the activators/deactivators  48  is adjacent to a respective element  50  when the AED  42  is within the case  44 . The activators/deactivators  48  do not deactivate the AED  42  unless they each sense a respective magnetic field from the respective adjacent element  50 . One advantage of this embodiment is that the activators/deactivators  48  will not undesirably deactivate the AED  42  in the presence of a non-case magnetic field (such as from a speaker magnet) that is strong enough or close enough for some, but not all, of the activators/deactivators to sense.  
         [0040]    [0040]FIG. 4 is a perspective view of an AED system  60  that includes an automatically activating/deactivating AED  62  and an AED storage case  64  according to another embodiment of the invention, where like numerals refer to like elements in the systems  40  (FIG. 2) and  60 . The AED system  60  of FIG. 4 is the same as the system  40  of FIG. 2 except that the AED  62  includes a non-magnetic activator/deactivator switch  66  instead of the magnetic activator/deactivator  48 , and the case  64  includes a non-magnetic deactivator pin  68  instead of the magnetic deactivator element  50 . When the switch  46  is in the “auto” position, the switch  66  deactivates the AED  62  when the pin  68 , which is tethered to the case  64  with a line  70 , is disposed within a receptacle  72  of the switch. Conversely, the switch  66  activates the AED  62  when the pin  68  is not disposed within the receptacle  72 .  
         [0041]    Still referring to FIG. 4, the operation of the system  60  in the automatic mode is discussed (in the manual mode, the system  60  operates in a manner similar to that discussed above in conjunction with FIG. 2 for the system  40 ).  
         [0042]    In the automatic mode, the AED  62  is stored in the case  64  with the switch  46  in the “auto” position, which allows the activator/deactivator switch  66  to control the on/off function of the AED. During a cardiac emergency, an operator (hands shown in FIG. 4) removes the AED  62  from the case  64 . Because the switch  46  is in the “auto” position, the AED  62  turns on automatically, thus eliminating the need for the operator to manually turn the switch  46  to the “on” or “auto” position. Specifically, as the AED  62  moves away from the case  64 , the slack in the line  70  is taken up until the line is taut. The length of the line  70  can be any suitable value, for example between six inches and one foot. As the operator continues to move the AED  62  beyond the point where the line  70  is taut, the line effectively pulls the pin  68  out of the receptacle  72 . The removal of the pin  68  causes the switch  66  to activate the AED  62 . Once the AED  62  is activated, the operator sets up the AED and uses the AED to shock a patient (not shown) as discussed above in conjunction with FIG. 1.  
         [0043]    After the operator finishes treating the patient with the AED  62 , he inserts the pin  68  back into the receptacle  72  and returns the AED to the case  64 . Because the switch  46  is in the “auto” position, the AED  62  turns off automatically in response to the insertion of the pin  68 , thus eliminating the need for the operator to manually turn the switch  46  to the “off” position.  
         [0044]    Other embodiments of the AED system  60  are contemplated as well. For example, the switch  46  may be omitted such that the AED  62  operates only in the automatic mode. Alternatively, one can program the operating mode of the AED  62  via a personal computer and interface (not shown) or via the screen  22 . In such embodiments, when the AED  62  is in the automatic mode, one can insert a portable pin  68  into the receptacle  72  to turn the AED off when it is out of the case  64 .  
         [0045]    [0045]FIG. 5 is a diagram of the switch  66  of FIG. 4 according to an embodiment of the invention. In addition to the receptacle  72 , the switch  66  includes nodes  74  and  76  and a resilient conductor  78 . When the pin  68  is disposed within the receptacle  72  as shown, the pin pushes the conductor  78  out of contact with the node  76 , thus opening the switch  66 . Conversely, when the pin  68  is not within the receptacle  72 , the conductor  78  contacts the node  76 , thus closing the switch  66 .  
         [0046]    Other embodiments of the switch  66  are contemplated. For example, the switch  66  may be an optical switch that effectively uses a beam of light (not shown) in place of the conductor  78 . When the pin  68  is disposed within the receptacle  72 , it breaks the beam and thus opens or closes the switch  66  depending on the switch&#39;s configuration. Conversely, when the pin  68  is not disposed within the receptacle  72 , the beam is not broken, and thus the switch  66  is closed or opened depending on its configuration.  
         [0047]    [0047]FIG. 6 is a perspective view of an AED system  80  that includes an automatically activating/deactivating AED  82  and an AED storage case  84  according to another embodiment of the invention, where like numerals refer to like elements in the systems  60  (FIG. 4) and  80 . The AED system  80  of FIG. 6 is the same as the system  60  of FIG. 4 except that the AED  82  includes a switch  86  that turns the AED  82  on or off depending upon whether a conductive loop  88  within a line  90  is open or closed. When the switch  46  is in the “auto” position, the switch  86  deactivates the AED  82  when the end  92  of the line  90  is attached to a conductive plate  94  that closes the loop  88 . The end  92  may be conventionally attached to the plate  94  with, for example, Velcro® or adhesive. Conversely, the switch  86  activates the AED  82  when the end  92  of the line  90  is not attached to the plate  94 , and thus the loop  88  is open.  
         [0048]    Still referring to FIG. 6, the operation of the system  80  in the automatic mode is discussed (in the manual mode, the system  80  operates in a manner similar to that discussed above in conjunction with FIG. 2 for the system  40 ).  
         [0049]    In the automatic mode, the AED  82  is stored in the case  84  with the switch  86  in the “auto” position, which allows the activator/deactivator switch  86  to control the on/off function of the AED.  
         [0050]    During a cardiac emergency, an operator (hands shown in FIG. 6) removes the AED  82  from the case  84 . Because the switch  46  is in the “auto” position, the AED  82  turns on automatically, thus eliminating the need for the operator to manually turn the switch  46  to the “on” or “auto” position. Specifically, as the AED  82  moves away from the case  84 , the slack in the line  90  is taken up until the line is taut. The length of the line  90  can be any suitable value, for example between six inches and one foot. As the operator continues to move the AED  82  beyond the point where the line  90  is taut, the end  92  of the line detaches from the plate  94 , thus opening the loop  88 . The opening of the loop  88  causes the switch  86  to activate the AED  82 . Once the AED  82  is activated, the operator sets up the AED and uses the AED to shock a patient (not shown) as discussed above in conjunction with FIG. 1.  
         [0051]    After the operator finishes treating the patient with the AED  82 , he reattaches the end  92  of the line  90  to the plate  94  and returns the AED to the case  84 . Because the switch  46  is in the “auto” position, the AED  82  turns off automatically in response to the closing of the loop  88 , thus eliminating the need for the operator to manually turn the switch  46  to the “off” position.  
         [0052]    Other embodiments of the AED system  80  are contemplated as well. For example, the switch  46  may be omitted such that the AED  82  operates only in the automatic mode. Alternatively, one can program the operating mode of the AED  82  via a personal computer and interface (not shown) or via the screen  22 . In such embodiments, when the AED  82  is in the automatic mode, one can attach a jumper (not shown) to the end  92  of the line  90  to close the loop  88  and turn the AED off when it is out of the case  84 .  
         [0053]    [0053]FIG. 7 is a perspective view of an AED system  100  that includes an automatically activating/deactivating AED  102  and an AED storage case  104  according to another embodiment of the invention, where like numerals refer to like elements in the systems  40  (FIG. 2) and  100 . The AED system  100  of FIG. 7 is the same as the system  40  of FIG. 2 except that the AED  102  includes an activator/deactivator receiver  106  instead of the magnetic activator/deactivator  48 , and the case  104  includes a deactivator transmitter  108  instead of the magnetic deactivator element  50 . When the switch  46  is in the “auto” position, the receiver  106  deactivates the AED  102  when it receives a predetermined signal  110  from the transmitter  108 . Conversely, the receiver  106  activates the AED  102  when it does not receive the predetermined signal  110 . Because they can be conventional, a detailed discussion of the receiver  106  and transmitter  108  is omitted for brevity.  
         [0054]    Still referring to FIG. 7, the operation of the system  100  in the automatic mode is discussed (in the manual mode, the system  100  operates in a manner similar to that discussed above in conjunction with FIG. 2 for the system  40 ).  
         [0055]    In the automatic mode, the AED  102  is stored in the case  104  with the switch  46  in the “auto” position, which allows the receiver  106  to control the on/off function of the AED.  
         [0056]    During a cardiac emergency, an operator (hands shown in FIG. 7) removes the AED  102  from the case  104 . Because the switch  46  is in the “auto” position, the AED  102  turns on automatically, thus eliminating the need for the operator to manually turn the switch  46  to the “on” or “auto” position. Specifically, as the AED  102  moves away from the case  104 , the receiver  106  senses a weakening of the signal  110 . When the strength of the signal  110  falls below a predetermined threshold, the receiver  106  turns on the AED  102 . In one embodiment, the sensitivity of the receiver  106  and/or the strength of the signal  110  are set such that the receiver activates the AED  102  when the AED is more than an inch or two from the case  104 . Once the AED  102  is activated, the operator sets up the AED and uses the AED to shock a patient (not shown) as discussed above in conjunction with FIG. 1. After the operator finishes treating the patient with the AED  102 , he returns it to the case  104 . Because the switch  46  is in the “auto” position, the AED  102  turns off automatically, thus eliminating the need for the operator to manually turn the switch  46  to the “off” position. Specifically, as the AED  102  moves toward the case  104 , the receiver  106  senses a strengthening of the signal  110 . When the strength of the signal  110  rises above the predetermined threshold, the receiver  106  turns off the AED  42 .  
         [0057]    Other embodiments of the AED system  100  are contemplated as well. For example, the switch  46  may be omitted such that the AED  102  operates only in the automatic mode. Alternatively, one can program the operating mode of the AED  102  via a personal computer and interface (not shown) or via the screen  22 . In such embodiments, when the AED  102  is in the automatic mode, one can attach a transmitter like the transmitter  108  to the AED to turn the AED off when it is out of the case  104 . In another example, both the AED  102  and the case  104  include respective transmitter/receivers (not shown) such as those used in highway toll-tag systems. The AED transmitter/receiver polls the case transmitter/receiver, deactivates the AED  102  when it receives a response from the case transmitter/receiver, and activates the AED when it receives no response. In yet another example, the AED  102  includes a transmitter/receiver and the case  104  includes a resonant circuit such as those used in badge-identification systems. The AED transmitter/receiver transmits a range of frequencies that includes the resonant frequency of the case resonant circuit, deactivates the AED if it detects a null at the resonant frequency, and activates the AED if it detects no null. FIG. 8 is a perspective view of an AED system  120  that includes the automatically activating/deactivating AED  42  of FIG. 2 according to another embodiment of the invention, where like numerals refer to like elements in the systems  40  (FIG. 2) and  120 . The AED system  120  of FIG. 8 is the similar to the system  40  of FIG. 2 except that deactivator element  50  is disposed outside of an AED case  124 , such as in a storage peg  126 . One stores the AED  42  by hanging a loop  128  over the peg  126 . In a related embodiment, the case  124  is omitted and the loop  128  is attached directly to the AED  42 .  
         [0058]    [0058]FIG. 9 is a block diagram of an AED circuit  140 , which the AEDs  42  (FIGS. 2, 3, and  8 ),  62  (FIG. 4),  82  (FIG. 6), and  102  (FIG. 7) can incorporate according to an embodiment of the invention. But for clarity and brevity, the circuit  140  is discussed in conjunction with the AED  42  of FIGS. 2, 3, and  8 , it being understood that the discussion also applies to the AEDs  62 ,  82 , and  102 .  
         [0059]    The electrode pads  14   a  and  14   b  are coupled to the circuit  140  via the connectors  16  and  18 , and are operable to sense a patient&#39;s ECG and to apply an electrical shock to the patient (not shown). A shock-delivery-and-ECG front-end circuit  142  samples the patient&#39;s ECG during an analysis mode of operation, and provides a shock to the patient via the connectors  16  and  18  and the electrode pads  14   a  and  14   b  during a shock-delivery mode of operation. A gate array  144  receives the ECG samples from the circuit  142  and provides them to a processor unit (PU)  146 , which stores and analyzes the samples. If analysis of the patient&#39;s ECG indicates that the patient is suffering from a shockable heart rhythm, then the processor unit  146  instructs the circuit  142  via the gate array  144  to enable delivery of a shock to the patient when an operator (not shown in FIG. 9) presses the shock button  30 . Conversely, if analysis of the patient&#39;s ECG indicates that the patient is not suffering from a shockable heart rhythm, then the processor unit  146  effectively disables the shock button  30  by preventing the circuit  142  from delivering a shock to the patient when the operator presses the shock button.  
         [0060]    Still referring to FIG. 9, the circuit  140  includes an on/off circuit  148 , which includes the switch  46 , activator/deactivator  48 , and the deactivator element  50  (e.g., FIG. 2). The circuit  140  also includes a power-management circuit  150  for distributing power from the battery  19  to the subcircuits of the circuit  140 . A status circuit  152  indicates the status of the circuit  140 , and a gate array  154  interfaces the power-management circuit  148 , the on/off circuit  148 , and the status circuit  152  to the circuit  142 , the processor unit  146 , and the gate array  144 . As discussed above in conjunction with FIG. 1, the AED  42  may include the display  22 , which presents information to an operator, a speaker  24 , which may provide audio instructions to the operator, and a microphone  32 , which may record the operator&#39;s voice and other audible sounds. The data card  34  is connected to the gate array  144  via a port  158 . The card  34  may store the operator&#39;s voice and other sounds along with the patient&#39;s ECG and a record of AED events for later study. A status-measurement circuit  160  provides the status of the circuit  140  subcircuits to the processor unit  146  and to the user via the status indicator  28  (FIGS. 2 and 3), and the LEDs  26  provide status information to the operator such as whether the processor unit  146  has enabled the circuit  142  to deliver a shock to the patient. A contrast control  164  allows the operator to control the contrast of the display screen  22  if present, and a memory such as a read only memory (ROM)  166  stores programming information for the processor unit  146  and the gate arrays  144  and  154 .  
         [0061]    The AED circuit  140  and other AED circuits are further discussed in the following references, which are incorporated by reference: U.S. Pat. No. 5,836,993, U.S. Pat. No. 5,735,879 entitled ELECTROTHERAPY METHOD AND APPARATUS, U.S. Pat. No. 5,607,454 entitled ELECTROTHERAPY METHOD AND APPARATUS, and U.S. Pat. No. 5,879,374 entitled DEFIBRILLATOR WITH SELF-TEST FEATURES.