Abstract:
An emergency alert system is disclosed. The invention employs an emergency alert message, which directs end users to take some particular action like evacuating an identified geographic area. The invention further employs a geographic area message, which is based on a particular geographic area within which all persons should receive the emergency alert message. The invention utilizes an emergency alert enabled device that receives both the emergency alert message and the geographic area message. The emergency alert enabled device then determines whether it is located within the geographic area of concern, and if so, presents the emergency alert message to the end user.

Description:
FIELD OF THE INVENTION 
     This invention relates in general to a method and apparatus for communicating emergency alert messages to members of the public. The invention provides an improved emergency alert system that allows for reliable transmission of emergency information to persons within a geographic area of concern. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Emergency alert systems are widely used. One common example of such a system is the emergency broadcast system used on television and radio. This system is often used to transmit information about potentially dangerous weather conditions. Other emergency alert systems rely on land-based telephone systems to send recorded messages to all persons within a particular area. Evacuation orders are another form of an emergency alert message, and these orders may rely on telephone systems, door-to-door communication by law enforcement officers, and other emergency communication methods. 
     As the public has become more concerned about terrorism threats and as communication systems have become more pervasive, a need has arisen for a better emergency alert system. Existing technologies suffer from many problems. A door-to-door communication of emergency information is effective at targeting only persons actually located in the area deemed to be at risk. Though door-to-door communication can be slow—the speed of this method depends on the number of persons to be contacted and the number of persons going door-to-door—it does provide the emergency information to the relevant members of the public. This benefit, however, comes at a very high price. Dedicating many law enforcement officers&#39; time to going door-to-door costs a great deal of money and creates troublesome opportunity costs. If three-fourths of the local police force is going door-to-door to warn persons about an emergency situation, those officers cannot be patrolling for crimes or other problem situations. Though it is one means of geographically disseminating an emergency alert, door-to-door emergency communication is typically seen as a means of last resort. 
     Sirens also have been used to alert persons to emergencies. A siren system is perhaps most effective for a particular purpose. A chemical plant, for example, might use sirens to warn persons near the plant of a problem. Sirens have limited range and require regular upkeep. Sirens typically do not provide situation-specific information. Persons inside houses or in automobiles may not hear sirens even when they are relatively near the siren. The one upside to sirens is their partial geographic selectivity. Only persons within a certain radius of the siren will get the alert. Even this advantage is limited, however, because in most emergencies, the alert area will not be a perfect circle around a particular siren. For these reasons, sirens remain a generally poor means of alerting persons of an emergency. 
     The emergency broadcasting system (EBS) sends emergency alert messages via live television and radio feeds. Though this system can reach many persons quickly, its reach is both too broad and too narrow. It is too broad because an entire television and radio broadcast region will be covered when most emergency alerts are relevant to only some part of that region. It is too narrow because even persons who are using their televisions or stereos may not be receiving a live television or radio transmission. Television viewers may be watching a move on DVD, watching a pre-recorded television program, or viewing a satellite television broadcast. Persons listening to stereos may be listening to satellite radio or a music CD. None of these persons would receive the EBS alert. 
     Automated telephone calling systems are widely used for sending emergency alert messages. This system is geographically specific, because only those phones within a defined alert area will be called. There are, however, several problems with these systems. They are expensive to purchase and use. They do not reach nearly all the relevant public. Many persons miss phone calls, and most of these systems call only landline phones. That excludes all cell phones and VOIP phones. Because some numbers must be called many times to reach a person, this process also can be slow. Finally, when a telephone alert system is used, it can jam the local telephone switching network, thus slowing the system and making it very difficult for local persons to use their own phones. 
     Internet and e-mail also may be used to send emergency alert information. This process can work quickly, but it has limited reach. It is also not geographically limited. 
     Given the heightened concerns with emergency threats and the many flaws in existing emergency alert systems, there exists a need for a better system. Such a system should operate quickly and reach all persons within the appropriate geographic area. It should be affordable to own and operate. A cost-effective geographically targeted emergency alert system is needed. 
     The present invention provides such an emergency alert system (EAS). The invention provides a method of sending geographically-targeted emergency alert messages to emergency alert enabled devices (EAEDs) operated by end users. Only those EAEDs within the geographic area at risk are notified of the emergency. The EAEDs are small devices that may be embedded within host devices such as cell phones, automobile stereos and/or navigation systems, televisions, radios, computers, mp3 players, land-line telephones, and virtually any other host device with the capacity to communicate message content to an end user. By incorporating the EAEDs into a wide variety of hosts, the present invention creates an EAS with the potential to reach virtually all appropriate persons very quickly. It is reliable, easy to operate, fast, and is geographically selective. It also requires only routine upkeep. 
     In a preferred embodiment, the invention includes an emergency operations center that selects an emergency alert message and identifies a geographic area of concern; an emergency alert transmission center that transmits the emergency alert message and a geographic area message that is representative of the geographic area of concern; a satellite that receives the emergency alert message and the geographic area message and retransmits these messages back to earth; and, an emergency alert enabled device that receives the retransmitted emergency alert message and geographic area message and that presents the emergency alert message if and only if the emergency alert enabled device is located within the geographic area of concern. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a graphical representation of the present invention. 
         FIG. 2  is a graphical representation of certain steps of a preferred embodiment of the invention. 
         FIG. 3  is a graphical representation of additional steps of a preferred embodiment of the invention. 
         FIG. 4  is a flow chart showing a preferred embodiment of the present invention. 
         FIG. 5  is a block diagram of another preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Key elements of an EAS  10  are shown generally in  FIG. 1 . An emergency alert transmission center  12  receives an emergency alert message and geographic data from an emergency operations center (EOC)  22 , and transmits one or more signals  16  to an emergency system satellite  14 . The signals  16  correspond to a geographic area message, which is based on a geographic area of concern, and an emergency alert message, which is intended for persons located within the geographic area of concern. The EOC  22  and the emergency alert transmission center  12  could be a single facility or could be separate facilities. In a preferred embodiment, the emergency alert transmission center  12  is a separate facility and serves a number of EOCs  22  from different geographic areas. For example, a single emergency alert transmission center  12  would be capable of serving EOCs  22  from numerous states, cities, or other areas. The emergency alert transmission center has one or more transmitters for sending the required messages to emergency system satellites  14 . 
     Though the invention is shown using a satellite  14  for the retransmission of the emergency alert message and geographic area message to earth, other means of transmitting these messages may be used. The cellular system provides the capability to transmit to nearly all of the geographic area of the United States and many other developed countries of the world. The emergency alert transmission center  12  may send emergency alert messages and geographic area messages via cellular transmissions, either as an alternative, or in addition to, satellite transmissions. The use of satellite transmissions is preferred, but the invention is not limited in this regard. 
     This arrangement is preferred because it allows one emergency alert transmission center  12  to handle all the satellite transmission tasks for several EOCs  22 . There are existing EOCs located throughout the world. Most regional governmental bodies (e.g., state, county or parish, and city governments) operate such EOCs. Some of these EOCs have satellite transmission capabilities and some do not. By routing all the EAS messages through a dedicated emergency alert transmission center  12 , a substantial cost-savings is passed on to the tax-paying public. In addition, using a dedicated emergency alert transmission center  12  should improve the efficacy of the system by ensuring that no conflicting messages are sent by different EOCs  22 . 
     The emergency system satellite  14  retransmits one or more signals  18  back to the earth, where these transmissions are received by emergency alert enabled devices (EAEDs)  20 . As described above, these signals  18  correspond to a geographic area message and an emergency alert message. The EAEDs are not shown in  FIG. 1 , but will be discussed in more detail below. 
       FIGS. 2 and 3  show steps of a preferred embodiment of the invention.  FIG. 2  is an overhead representation of a illustrative geographic region. An emergency situation has occurred at a site  30 , and personnel at an EOC  22  (not shown in  FIG. 2 ) have decided that an emergency alert message should be communicated to all persons within a particular geographic area of concern  32 , which is shown in blocked off form in  FIG. 2 . The geographic area of concern  32  could be circular, semi-circular, rectangular, or take any other shape. Operators at the EOC must make a determination of what geographic area  32  should be notified of the emergency. 
     In the hypothetical illustration shown in  FIG. 2 , a fire has occurred at a chemical facility, posing a risk of hazardous airborne materials in an area nearby and downwind of the fire location. Operators at the EOC are informed of the emergency and the risk. The operators then determine an appropriate geographic area  32  within which all persons must receive the alert message. The system thus creates and transmits geographically targeted emergency alert messages. Only those persons within the relevant geographic area are targeted for message transmission. Using the present invention, an operator might use geographic mapping software to define an alert area. This process could use electronic street maps, satellite images, or combined satellite images overlaid with street map information. 
     Though the invention may use electronic maps, the present invention is not dependent upon maps or the mapping process. The invention may use actual latitude and longitude coordinates to define the area of concern and to establish the exact location of a particular user. This approach provides accurate and reliable position information. Maps may be out dated or otherwise inaccurate. In addition, persons may be in an uninhabited area on a map (e.g. on a lake or in a forest), but the present invention may still be able to reach those persons if they are located within the area of concern for the emergency. Most prior art systems rely, to some extent, on maps, either hard-copy or electronic, and are, therefore, inferior to the present invention in this regard. 
     A computer or equivalent device may be used to generate a geographic area message. This message would include an electronic representation (e.g., in the form of an algorithm) of the geographic area of concern for the particular emergency. The geographic area  32  shown in  FIG. 2  is an illustration of a geographic area of concern. A geographic area message might include a series of mathematical expressions that define the geographic area  32  in such a manner that a processor in an EAED  20  may use the expressions to determine whether the actual geographic location of the EAED  20  is within the area of concern. 
     In this example, an EOC operator defined an alert area south and east of the fire. This is shown by the geographic area  32  in  FIG. 2 . Data representative of this geographic area is prepared for transmission to the emergency alert transmission center  12 . The processing of the geographic area data may be done in various ways that are known to persons skilled in the art. 
     It is desirable to encode the geographic area data in such a manner to limit the size of the message that must be transmitted to and from the emergency system satellite  14 . A larger data volume will require more memory resources on the satellite  14  and in the EAEDs  20 . In addition, the larger the size of the transmission, the longer the transmission will take. The time difference is not likely to result in a noticeable delay in the response time of the system, but a longer satellite transmission is more vulnerable to interference or interruption than a more brief transmission. In addition, the devices ultimately receive the message may not have a great deal of internal memory, and may tend to limit the size of messages that may be used with the invention. For these reasons, it is desirable to limit the size of the geographic area message. 
     The geographic area data may be compressed to reduce the size of the data transmitted. Such data compression may be done in any suitable manner. Numerous types of digital data compression are known to persons with skill in the art, and no particular method is known to be superior to another for the purposes of this invention. For operational consistency, it is highly preferred that a single data compression scheme be adopted and used by all EAS operators. 
     The compressed geographic area message is transmitted to the emergency system satellite  14  and is then retransmitted to EAEDs  20 . In a preferred embodiment, the EAEDs are capable of decompressing the geographic area message. To avoid having to program the EAEDs  20  to recognize and decompress multiple types of data compression, it is, again, highly preferred that a single data compression scheme be adopted and used by all EAS operators. Using a small number of dedicated emergency alert transmission centers  12  would facilitate this objective, because the data compression could be performed by the emergency alert transmission center  12 , rather than by the EOCs  22 . 
     The emergency system satellite  14  may store the received emergency alert message and geographic data message for repeated retransmission to earth for some period of time. This may improve the effectiveness of the system by increasing the chances that EAEDs  20  within the geographic area of concern would actually receive the required messages. 
     In addition, the satellite  14  may alter the format of the messages before retransmission, may modify or remove the data compression, or perform other changes to the digital characteristics of the emergency alert message and/or the geographic area message. These types of changes are all within the scope of the present invention, and would still constitute a retransmission of the messages by the satellite  14 . As long as the same message content (i.e., the same emergency alert message—for example, to evacuate the area—and the same geographic area of concern) is transmitted by the satellite  14  to earth, such transmission is considered a retransmission of the same messages sent to the satellite  14  from the emergency alert transmission center  12 . 
     In another embodiment of the preferred invention, the EOC  22  provides non-digital geographic area information to the emergency alert transmission center  12 , where the geographic area information is then digitized and compressed. For example, the EOC could provide a verbal or written description of the alert area to the emergency alert transmission center  12 . The operator at the emergency alert transmission center  12  may then use mapping software to define the geographic alert area, and the geographic area of concern would thus become an appropriate digital, and compressed, geographic area message signal, ready for transmission to the emergency system satellite  14 . 
     The shape of the geographic area of concern may have a significant impact on the size of the geographic area data packet. A circular shape is easy to define digitally and produces a relatively small file size. A convoluted shape with numerous rectangular segments, on the other hand, can be quite difficult to define digitally, and can result in a very large file size. In some instances, it may be preferable to transmit multiple sets of geographic area and alert messages, with the entire geographic area broken down into more easily defined areas. This type of variation, and others intended to facilitate reliable operation of the EAS are within the scope of the present invention. 
       FIG. 3  represents the next general step of a method of a preferred embodiment of the present invention. This drawing illustrates the emergency alert message selection process  34 . In the example shown in  FIG. 3 , the operator may select from certain standardized alert messages (e.g., evacuate or shelter in place) or may create a custom message. In addition, the present invention contemplates alert messages in text, audio, video, or any combination of these communicative methods. For example, an alert might consist of a text message, an audio version of either the same message or a more detailed message, and a video presentation showing a map of the alert area and safe areas. 
     The emergency alert message may be generated using computer software with a radio control menu  36 , as illustrated in  FIG. 3 . Other means of generating an emergency alert message may include using codes representative of preselected messages and communicating the codes to an emergency alert transmission center  12 , where the actual electronic message could be created. Similarly, an operator at the EOC  22  could call in the emergency alert message to the emergency alert transmission center  12 , or e-mail or other communication means could be used. 
     In a preferred embodiment, the geographic area message and the emergency alert message are linked in some manner. The two messages are related to each other, and will be transmitted and retransmitted as a pair of messages, or in some embodiments, as two parts of a single composite message. These variations do not deviate from the invention. In one preferred embodiment, these messages are linked by cross-reference data that allows the two messages to be positively correlated to each other by any device used in the EAS. For example, the transmitter, the satellite, and the EAED all would be capable of recognizing a pair of linked emergency alert and geographic area messages. 
     Turning now to  FIG. 4 , a flow chart  40  is presented. This chart depicts steps of a preferred embodiment of the present invention. The first step shown is the determination by emergency personnel that some segment of the public should be notified of an emergency  42 . Once this determination has been made, an operator defines an appropriate emergency alert area using computer software  44 . An appropriate emergency alert message then is selected or created by an operator  46 . The geographic alert area is converted into a mathematical algorithm for the geographic area signal  48 . The geographic data may be compressed as part of this step or an additional data compression step—not shown in FIG.  4 —may be used. 
     A computer may be used to digitally encode the geographic area of concern. As there is no current standard format for geographic mapping algorithms, the invention is not limited to any particular format type for the geographic data. Computer software may be used to create a digitized representation of the geographic area of concern. This digital file would be part of, or perhaps all of, the geographic area message transmitted to the satellite and subsequently retransmitted to the EAEDs  20 . 
     Once the appropriate alert message signal and geographic area message signal are prepared, these two sets of information are transmitted to one or more satellites  50 . The satellites then broadcast the emergency message signal and geographic area message signal to a selected region  52 . These broadcasts will cover a much larger geographic region than that selected by the emergency system operator in order to ensure that the entire geographic area of concern is fully covered by the broadcasts. For example, if the emergency alert area includes a part of Houston, Tex., the satellite transmissions might reach users throughout North America. Other satellites broadcasting to other parts of the world would not be used in this example. It is anticipated, however, that use of more than one satellite may be desirable to provide redundancy and thus increase the effectiveness of the invention. 
     An EAED  20  then receives the satellite transmission of the alert message signal and the geographic area message signal  54 . Once these two signals are received, an EAED  20  will evaluate the geographic area message and compare the geographic data contained in that message to the EAED&#39;s current geographic location  56 . The EAED  20  may use a variety of means for fixing its geographic location, but a preferred means is use of the global positioning system or GPS. This is discussed in more detail below. The EAED  20  then performs an decision step. It asks whether the EAED  20  is within the geographic area of concern  58 . 
     If the EAED  20  is outside the area of concern, the process ends  60 . If, however, the EAED  20  is within the geographic area of concern, the EAED presents the emergency alert message  62 . The EAED  20  then saves the message for repeat play upon request by a user  64 . The message is presented even if no user is there to receive the message. The means of presentation will vary depending upon the interface used by the EAED and/or its host device. 
     In the most preferred embodiment, the EAED  20  is embedded within a host device. If the EAED  20  is required to deliver an alert message  62 , the host device may be used to present the message the user. In the event the host device is in use for some other purpose, the EAED  20  would override the current operation of the host device so that the emergency alert message is delivered. In the event the host device is turned off when the EAED  20  determines that an alert message is to be delivered  62 , the EAED  20  would turn on the host device and deliver the message. The host device may be turned back off again after the alert message has been delivered. 
     Whether the alert message is delivered  62  or not delivered  60 , the EAED  20  returns to ready mode  66  following execution of the preceding steps. In fact, the EAED  20  remains ready to receive messages at all times, and in a preferred embodiment, has a buffer or queue to hold incoming messages while other messages are being processed. This is potentially important because it is possible that a particular EAED  20  could receive numerous messages within a very short period of time. The present invention allows for this, and ensures that any alert message that needs to be delivered to a user will be delivered. In practice, an EAED  20  would take just a few seconds to process a number of alert message/geographic message pairs. 
     A block diagram of an EAED  20  is shown in  FIG. 5 . The blocks represent a geographic position module  72 , a satellite message receiver  74 , an emergency alert message interface  76 , and a data processor  78 . The geographic position module  72  in a preferred embodiment is a highly-sensitive GPS receiver. Because the EAED  20  must remain on at all times and must be capable of fixing geographic position even when a user is indoors or under heavy tree cover, there is a need for a GPS receiver with very high sensitivity and very low power consumption. 
     GPS receivers satisfying these requirements may be obtained from a variety of sources. One model that has worked well is made by u-blox, a German company specializing in GPS technology. u-blox makes a variety of GPS receivers, and has developed extraordinarily sensitive receivers. GPS satellites must transmit continuously, and for this reason, these satellites transmit at very low power levels. This has caused reception problems with GPS receivers in the past. Many GPS units lose their signal when the unit is inside a vehicle, under dense tree cover, or indoors. In addition, many GPS units are slow to acquire a position. It is highly desirable to avoid such shortcomings in the present invention. 
     The u-blox GPS receivers combine highly sensitive antennas with sophisticated data processing. Some u-blox receivers include a dead reckoning feature that helps estimate current position of a unit even if GPS satellite data is momentarily lost. In addition, the u-blox GPS receivers are ultra-low power consumption devices, using less than 50 mW of power. The u-blox  5  is the latest generation u-blox GPS chipset, and it is expected that this chipset would work well with the present invention. u-blox claims that this chipset acquires a GPS fix in less than one second. Quick and accurate fix acquisition is highly desirable for the present invention. 
     If a GPS fix may be reliably obtained very quickly, it is possible for the geographic position module  72  to power down during regular operation of the EAED  20 . The geographic position module  72  could obtain a GPS fix on a periodic basis, and could be configured to obtain a fix when a geographic area message and an emergency alert message are received from a satellite. Such operation may reduce the power consumption of the geographic position module  72 , and thus reduce the overall power demands of the EAED  20 . 
     The invention will work with any low-power, high sensitivity GPS receiver. The u-blox receivers are a currently preferred embodiment, but there is a great deal of competition within the GPS receiver market. In addition, a new generation of improved GPS satellites will be put into operation in the future. These new satellites will have higher transmission levels than the existing GPS satellites. When these new satellites become available, the sensitivity concern may be less important than it is today. The power consumption concern, however, may remain important, particularly if the EAED  20  is configured to remain powered up at all times. 
     The satellite message receiver  74  includes components necessary to receive the alert message and geographic area message from the emergency system satellite  14 . Existing technologies used in satellite radio, satellite pagers, or satellite cell phones could be used for this purpose. It is desirable for the satellite receiver to be highly sensitive and consume minimal power. The satellite message receiver  74  may operate in a sleep mode until a signal is received, thus conserving power. 
     The satellite message receiver  74  must have sufficient sensitivity to reliably receive satellite signals even when indoors, inside a car, or in other situations where there is no clear line-of-sight to the transmitting satellite. This concern is less limiting than the GPS sensitivity issue discussed above because the satellites used by the EAS are likely to transmit substantially more powerful signals than do existing GPS satellites. Satellite pagers and satellite phones have good performance even when the receivers are indoors, and these technologies, therefore, are preferred for the present invention. Satellite radio, in its current state of development, tends to suffer from frequent signal loss, and for that reason, is not currently preferred for this invention. As with GPS receiver technology, it is expected that competition will lead to improvements in the satellite radio receiver technology, and this type of technology may well be a good match for the present invention in the future. 
     The geographic position module  72  and the satellite message receiver  74  both require a satellite antenna in the most preferred embodiment. Separate antennas could be used, or a single, dual-use antenna could be used. In either case, the antennas selected should have the highest possible sensitivity. In some applications, the host device (i.e., the device in which the EAED  20  is embedded) may have an existing antenna that would provide superior performance and that could be shared by the EAED  20 . 
     The data processor  78  performs the needed analysis of the incoming geographic data received via the satellite message receiver  74  and the current geographic location information received via the geographic position module  72 . An evaluation is performed to determine whether the current geographic position of the EAED  20  is within the geographic area of concern. If so, the data processor  78  then sends the emergency alert message to the emergency alert message interface  76 . This interface  76  either directly or indirectly presents the emergency message to a user. The data processor  78  also includes sufficient memory to store prior alert messages for replay at a later time. Alternatively, such memory could be provided in a separate module within the EAED  20 . 
     The EAED  20  could be a stand-alone unit or could be embedded within a host device. The latter arrangement is preferred. A wide variety of host devices are contemplated for the present invention. Automobiles, cellular phones, land-line telephones, computers, televisions, radios, mp3 players, and almost any existing or later-developed device that provides text, audio, or video content to an end user. If, however, the EAED  20  is a stand alone unit, the device must also include some means for communicating directly with a user. This could be a visual display screen (e.g., a small LCD display) or an audio system. 
     To more fully appreciate the operation of the present invention, consider its use in an automobile. The EAED  20  could be incorporated into the design of the automobile in a seamless manner. With a small footprint, low power consumption, and the relatively large source of power via the automobile&#39;s large starter battery, the EAED  20  would raise minimal design challenges for an automobile designer. The EAED  20 , for example, could be incorporated into the vehicle&#39;s stereo system or into a navigation system, if the vehicle was so equipped. The EAED  20  might use an existing antenna on the vehicle to improve satellite reception. The EAED  20  could interface with the audio system in the vehicle to present audio alert messages or with the warning light and/or alarm system to warn the user of the emergency. Many vehicles today have visual displays capable of presenting text messages, and such a capability could be used by the EAED  20  to communicate emergency messages. If a relevant emergency message is received while the vehicle is not in use, the EAED  20  could store the message, and present it to the user the next time the vehicle is used. 
     If an EAED  20  is embedding into a cellular phone, the invention could interface with the phone to provide audio, text, and potentially video emergency message content. A unique emergency alarm ring-tone could be used to ensure the user recognizes the urgency of the event. If the phone is in use, the EAED  20  could override the existing use and convey the emergency alert to the user. 
     Embedding an EAED  20  into a television, radio, mp3 player, or other device with some form of audio and/or visual interface is also expected. When an EAED  20  embedded within such a device receives a relevant message, it could turn the device on and convey the alert message. The device could then be turned off again. The message could be stored until a user later turns on the device, at which point the alert message could be provided again. 
     The EAED  20  and its host device could be configured to operate regardless of the mode of operation in use at the time. For example, if an EAED  20  is embedded in a television and a movie is being watched via an alternative input, the EAED  20  would still prompt the television to provide the alert message. This capability shows one important advantage the present invention offers over the existing emergency broadcast system (EBS). The EBS will reach only those persons watching a regular television broadcast. If, for example, a user&#39;s television is on a Video One input receiving a feed from a DVD player, the EBS cannot reach that user. The EAED  20  of the present invention, however, would reach that user. 
     The foregoing examples of applications of the present invention are by no means exhaustive. It is expected that the EAED  20  of the present invention will be embedded in a wide variety of electronic products. The particular manner in which the EAED  20  is integrated with such products is left to the manufacturers and designs of the products. The present invention provides the EAED technology and an EAS method of operation. The manner in which EAEDs  20  are integrated into host systems is expected to vary a great deal.