Abstract:
A personal alarm system can be worn or carried by the user, may be activated at any time by the user and/or may be automatically activated to send a signal to any remote monitoring station on the network. The device identifies the user as well as the user&#39;s location within the monitored area. The alarm-sending unit is designed to fit within a box the size of a small cell phone or pager. The unit includes an ID memory for identifying the user, is programmable and has an on-board processor for generating a signal to a wireless transmitter for sending the signal to a to a local receiver for inputting the signal onto the network. A centralized, networked RF receiver is used with the personal alarm unit and one or more of these RF receivers may be installed in order to provided adequate coverage of the monitored area. The signals generated by the personal alarm are received by the RF receiver(s) and decoded, whereupon the system processor assembles a message, packetizes it as necessary, and sends it to one or more monitoring stations via the intervening network and network interface. The signals may be digitized where desired. A beacon generator may be used to identify location of the portable unit. The system may also employ a GPS generator to identify location.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The subject invention is generally related to personal security alarms or panic button devices and is specifically directed to a personal alarm system having network communication capability whereby the user can generate a signal to a remote location from any monitored area.  
           [0003]    2. Description of the Prior Art  
           [0004]    There are numerous devices that allow an individual to send a panic signal to a remote location in order to seek assistance when certain events occur. For example, many semi-invalid medical patients will wear a panic button as pendant around their neck, with the panic button adapted to be manually pushed in order to signal a medical emergency. The button device then transmits a signal to a remote monitoring station for initiating a ids response. Basically, the device transmits a radio signal to a receiver and identifies the patient. The response is typically a telephone call to the patient&#39;s residence and if no answer is received, emergency personnel are dispatched. This system works relatively well if the patient stays near the identified telephone or remembers to inform the monitoring system personnel of his/her whereabouts if he/she leaves an identified area. A major drawback to this system is the inability to track the location of the patient. Another drawback is the requirement that the panic button be manually activated in all circumstances. In certain situations, it may be impossible for the wearer to manually activate the system, rendering the panic system ineffective.  
           [0005]    There are many applications both in the medical field and in other fields where a personal panic alarm system would be useful, particularly if the alarm identified the location of the personnel and even more so if under certain conditions the system were automatically activated. For example, such a device would be useful in school systems wherein the teaching staff could wear the panic button device and immediately signal security and/or administrative personnel of an incident. This would be particularly useful if the system identified the location of the teacher as well as in many instances identified the type of emergency. To date, no known devices provide such features and capability.  
           [0006]    There are a number of devices available that address location tracking. As an example, U.S. Pat. No. 5,276,496 discloses an optical system for locating a target within a defined area by comparing the received light intensity between the several sensors. U.S. Pat. No. 5,355,222 discloses an optical position sensor, wherein an object with a luminous transmitter is viewed by an array of binary-patterned sensors. U.S. Pat. No. 5,548,637discloses a telephone-forwarding system wherein people are ‘tagged’ with optical transmitters, and stationary receivers located throughout the premises determine the person&#39;s location and nearest telephone extension.  
           [0007]    U.S. Pat. No. 4,275,385 discloses a personnel locator system wherein people carry coded infrared transmitters throughout a facility. Zoned receivers detect the coded signals and determine the person&#39;s location. U.S. Pat. No. 5,062,151 discloses a personnel location system, wherein people carry coded infrared transmitters, which activate infrared receivers in each equipped room.  
           [0008]    While each of the prior art devices address certain location issues, none of the known devices provides an affordable, comprehensive personal signaling and locating device.  
         SUMMARY OF THE INVENTION  
         [0009]    The subject invention is directed to a personal alarm system that is affordable, portable and fully compatible with a comprehensive security system such as that shown and described in my co-pending U.S. patent application, Ser. No. 09/594,041, entitled: Multimedia Surveillance and Monitoring System Including Network Configuration, filed on Jun. 14, 2000. The device can be worn or carried by the user, may be activated at any time by the user and/or may be automatically activated to send a signal to any remote monitoring station on the network. The device also identifies the user as well as the user&#39;s location within the monitored area. In the preferred embodiment, the alarm sending unit is designed to fit within a box the size of a small cell phone or pager. The unit includes an ID memory for identifying the user, and has on-board circuitry for generating a signal to a wireless transmitter for sending the signal to a to a local receiver for inputting the signal onto the network.  
           [0010]    In one embodiment of the invention, the device can be worn on the person of key personnel for activating a signal that is transmitted to a remote location such as security personnel or a guard station processor or the like. As an example, the device of the present invention is particularly useful in aircraft applications where a crew member can send a distress signal directly to ground control in the event of an emergency or catastrophic event. In its simplest form, the device may be a wired “ON-OFF” button placed at a strategic location in the aircraft, such as, by way of example, on the control panel of the cockpit and/or in the galley or other strategic location in the passenger cabin. In an enhanced embodiment, the device is wireless and may be carried directly on the person of a crew member. Preferably, each crew member would be armed with the wireless device.  
           [0011]    In its simplest form, the device simply sends an emergency signal to ground control, thus alerting ground control that an emergency has occurred and that the aircraft requires immediate monitoring and communication. In an enhanced embodiment, the device is linked to a comprehensive on-board security system and in addition to transmitting a signal to ground control, also activates the security system to collect additional data and store the data in the on-board recorders as well as optionally sending the data to the ground control in a live, real-time transmission.  
           [0012]    One of the advantages of this system is that where loop recorders are used, such as, by way of example, thirty minute loop recorders common on many commercial aircraft, an activation signal can download the stored information and begin live transmission of new information. This permits the thirty minutes of data recorded prior to the incident to be received at ground control and minimizes the current dependency of finding the “black box” recorder. This also permits important data relating to the events prior to the incident as well as data after the incident to be collected for investigation and reconstruction of the event.  
           [0013]    The wireless system has numerous advantages in preserving the ability to transmit emergency signals. For example, it is virtually impossible to simultaneously disarm all wireless components, preserving some transmission capability even if certain of the devices are disabled. Also, when used in combination with the comprehensive wireless system, it is possible to initiate and transmit information even after the integrity of the aircraft has begun to disintegrate.  
           [0014]    In additional embodiments of the invention, the device may be more sophisticated to permit the type of emergency to be embedded in the emergency signal. For example, it is useful to distinguish between a fire emergency, a medical emergency and a security emergency since the response to each will be different.  
           [0015]    The device of the subject invention is also well suited for use in facility security applications where roving personnel may have need for a personal alarm device in order to signal response personnel as to the presence of an emergency condition. For example, the device is very useful for teachers in managing classroom or campus emergencies. In this application, the device is location specific, not only sending a signal to the monitoring station, but also identifying the sender and the sender&#39;s location.  
           [0016]    In one embodiment, a centralized, networked RF receiver is used with the personal alarm units. One or more of these RF receivers may be installed in order to provided adequate coverage of the monitored area. The signals generated by the personal alarm are received by the RF receiver(s) and decoded, whereupon the system processor assembles a message, packetizes it as necessary, and sends it to one or more monitoring stations via the intervening network and network interface. The signals may be digitized where desired.  
           [0017]    In an enhanced embodiment, beacon transmitters are installed at various locations around the monitored facility, again connected to a common facility network. The beacon transmitters are designed to transmit a unique beacon ID signal at regular intervals. The beacon signals may also be generated by a control signal from a system processor on the facility network. These signals may be infrared, RF, ultrasonic or other known format. The personal alarm unit will store the beacon signal each time it is received. When a signal is initiated from the personal alarm unit it will identify the location of the sender by transmitting the last stored beacon signal, providing an efficient, inexpensive and accurate method of tracking the user.  
           [0018]    In large enclosed areas such as a gymnasium or auditorium multiple beacons may be employed for further refining the location of a sending unit. It is also an important feature of the invention that GPS technology may be employed in outdoor settings such as a stadium, campus grounds or the like. This is useful independently of the beacon technology, or may be employed in connection with the beacon technology in order to track location of a user both internally and externally while in the monitored area.  
           [0019]    It is, therefore, an object and feature of the subject invention to provide a personal alarm device capable of transmitting a signal to a remote location upon activation.  
           [0020]    It is also an object and feature of the subject invention to provide a personal alarm device capable of activating a security and surveillance system when the device is activated.  
           [0021]    It is an additional object and feature of the subject invention to provide a personal alarm device for initiating the transmission of event data to a remote location when the device is activated.  
           [0022]    It is also an object and feature of the subject invention to provide a personal alarm device capable of sending an alarm signal to a remote station while identifying the identity and/or the location of the user.  
           [0023]    It is another object and feature of the subject invention to provide an efficient method of monitoring and identifying the location of each unit in the system.  
           [0024]    It is an additional object and feature of the subject invention to provide the means and method for supporting a personal wireless alarm system via a local area network (LAN) or wide area network (WAN).  
           [0025]    It is yet another object and feature of the invention to provide a personal alarm system that may be polled by the monitoring stations on demand.  
           [0026]    It is another object and feature of the subject invention to provide a personal alarm that may automatically send a signal upon the occurrence of certain, specified events.  
           [0027]    It is a further object and feature of the subject invention to provide a personal alarm capable of providing voice communication with the monitoring station.  
           [0028]    It is a further object and feature of the subject invention to provide a personal alarm system capable of identifying the type of emergency causing the need to initiate a signal.  
           [0029]    It is a further object and feature of the subject invention to provide an intercom feature, signaling designated stations and transmitting microphone signals to that station.  
           [0030]    It is a further object and feature of the subject invention to signal the location of an intercom call to the called station, such as presenting a room name and/or a signaling icon on a map at the called station.  
           [0031]    It is a further object and feature of the subject invention to provide an “open microphone” after the initiation of an emergency or intercom signal.  
           [0032]    It is a further object and feature of the subject invention to incorporate the panic button receiver in multipurpose network appliances, such as wall clock appliances, video camera appliances, smoke detector appliances, and the like.  
           [0033]    It is a further object and feature of the subject invention to incorporate the beacon transmitter (or receiver depending on the exact method of implementation) in multipurpose appliances, such as wall clock appliances, video camera appliances, smoke detector appliances, and the like.  
           [0034]    Other objects and features of the invention will be readily apparent from the accompanying drawings and detailed description of the preferred embodiments.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0035]    [0035]FIG. 1 is a perspective view of a basic personal alarm device in accordance with the teachings of the subject invention, including a basic block diagram of the circuitry for the device.  
         [0036]    [0036]FIGS. 2A and 2B illustrate a decision flow diagram for one embodiment of the device.  
         [0037]    [0037]FIG. 3 is a diagram of a network system for supporting the device of the subject invention.  
         [0038]    [0038]FIG. 4 illustrates a beacon transmitter, which operates without a supporting facility network.  
         [0039]    [0039]FIG. 5 is a perspective view of an enhanced personal alarm device with additional features, including a basic block diagram of the circuitry for the device.  
         [0040]    [0040]FIGS. 6A and 6B illustrate the decision flow diagram for the device as modified in FIG. 5.  
         [0041]    [0041]FIG. 7 illustrates a comprehensive system incorporating the teachings of the subject invention.  
         [0042]    [0042]FIG. 8 is the timing decision flow diagram for the configuration of FIG. 7.  
         [0043]    [0043]FIGS. 9A and 9B illustrate a beacon signal management system for supporting beacon signal management of a system in accordance with the subject invention.  
         [0044]    [0044]FIG. 10 illustrates a system for housing the beacon transmitter/receiver in a wall appliance.  
         [0045]    [0045]FIG. 11 shows a scheme for providing complete coverage of a target area utilizing strategically placed beacon transmitters/receivers.  
         [0046]    [0046]FIG. 12 depicts an adaptation of the system to support usage in a large outdoor area such as a stadium.  
         [0047]    [0047]FIG. 13 depicts a modification of the system of FIG. 1 incorporating an ultrasonic transducer for transmitting encoded information.  
         [0048]    [0048]FIG. 14 illustrates a system for receiving, processing and disseminating the message received from a handheld device by a local networked appliance.  
         [0049]    [0049]FIG. 15 illustrates a typical application of the system.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0050]    FIGS.  1 - 3  depict a basic embodiment of the system that does not included encoded location information. This application is particularly well suited for confined environments such as aircraft and the like, where the location of the person sending the signal is not as critical as in large installations such as a high school campus. In its simplest form, the alarm unit  5  of FIG. 1 comprises a simple panic button, which is a radiator that transmits a coded signal to the closest receiver via the antenna  40 , with the receivers of FIG. 3 being conveniently located and connected to the network. Receivers can be integrated into other devices, such as wall clock appliances, thermostats, smoke detectors, motion detectors, and the like in the room or facility where the alarm unit is to be used. The transmitter radiator may comprise any of a number of signal generating protocols, such as, by way of example: RF (a potential location problem for certain applications in that it goes through walls so exact room location and identification is more difficult); LIGHT, such as IR, (directional and can be blocked by clothing and other obstructions); and ULTRASONIC (includes the dual advantages of being contained to a room, while not being as directional as IR and not so blocked by clothes. The specific method used will be dictated by the application and by cost/benefit factors and is well within the scope of knowledge of those skilled in the art.  
         [0051]    The device of the subject invention may send the signal directly to a transmitter for sending the signal to a remote station, as shown in FIG. 1, or may be adapted for sending a signal to the installation security system for activating it as well, as shown in FIG. 10. A detailed description of aircraft security systems are shown and described in my issued U.S. Pat. Nos. 5,798,458, 6,009,356, 6,253,064B1, and 6,246,320B1, incorporated by reference herein. A detailed description of a comprehensive multimedia security system is shown and described in my copending application Ser. No.: 09/594,041, filed on Jun. 14, 2000, entitled: “Multimedia Surveillance and Monitoring System Including Network Configuration, also incorporated by reference herein.  
         [0052]    In most cases, the receiver of FIG. 3 will be incorporated in other appliances in the facility. For example, a room monitor in a school may be mounted on a wall and may include various sensors as well as the receiver. A detailed description of such devices is incorporated in my co-pending application entitled: Multimedia Network Appliance for Security and Surveillance Applications, (Docket No. 081829.000026) Ser. No.: ______, filed on Sep. 21, 2001, and incorporated herein by reference. Accordingly, FIG. 1 shows a wireless personal alarm  5 , housed in an enclosure similar to a pager. The alarm has one or more pushbutton switches S 1 -S 3 , to notify a monitoring station of an emergency condition. As depicted in FIG. 2A, upon activation via switches S 1 , S 2 , or S 3 , the internal processor  10  of FIG. 1 encodes and transmits a message containing the personal alarm unit ID number and the emergency ID number. Optionally, the alarm may be arranged to transmit audio from the environment near the pager as depicted in FIGS. 1 and 2B. Microphone audio may be transmitted using conventional analog methods, or may optionally be digitized and compressed via A/D converter  31  and compressor  32  in FIG. 1. For example, either of the following schemes may be utilizes: analog transmission of the microphone from the panic button with A/D and optional compression at the receiver/appliance end, or optional compression and digital transmission at the panic button end, with digital reception and digital relay at the receiver/appliance end.  
         [0053]    It should be understood that the terms encoder and decoder as used throughout the application are intended to mean modules adapted for modifying a transmitted signal so that it is compatible with a receiver. In the simplest form, wherein the signal generator and the signal receiver are fully compatible, the encoder and decoder modules are unnecessary. In other instances, the protocol may have to be modified, or an analog signal may have to be converted to a digital signal and vice versa. In some instances, where it is clear that a signal is generated in an analog format (such as an analog microphone, see microphone  30  in FIG. 1) and is processed by a digital module (see the compressor  32  in FIG. 1) the “encoder” or “decoder” may be illustrated as a simple A/D converter.  
         [0054]    The audio may be transmitted as analog or digital. If analog, it needs to be digitized and optionally compressed before introduction to the LAN or WAN network.  
         [0055]    [0055]FIG. 3 depicts a centralized, networked RF receiver used with the personal alarm units. One or more of these RF receivers may be installed in a facility to provide adequate coverage of the premises. Personal alarm signals received by antenna  50  are demodulated by the wireless receiver  55 . These received messages are decoded via decoder  60 , and passed to system processor  70 . Processor  70  thereupon assembles a message, packetizes it if necessary, and sends it to one or more monitoring stations  85  via the intervening network interface  75  and network  80 . Optionally, audio transmitted by an active personal alarm unit and received by the wireless receiver  55  may be digitized by A/D converter  65 , then packetized by processor  70 , and conveyed to the monitoring station(s) via the network and associated interface. If the microphone audio had been transmitted digitally, then the system processor  70  need only packetize the audio data prior to transmission via network interface  75 .  
         [0056]    As indicated in the drawing the network can be a wireless LAN (WLAN), a wired LAN, a modem/PSTN (public switched telephone network), two-way pager, CDPD, or other suitable network system. One embodiment of a suitable network system is shown and described in my previously mentioned co-pending application Ser. No. 09/257,720, entitled: Network Communication Techniques for Security Surveillance and Safety System.  
         [0057]    FIGS.  4 - 6  illustrate a useful enhancement to the system, wherein numerous beacon transmitters are installed at various locations around the facility. Beacons transmit their unique ID to Personal Alarm Units, which thereby maintain a knowledge of the ID of the nearest beacon. When a Personal Alarm Unit needs to transmit an emergency indication, it can thereby notify one or more facility receivers of its ID, nearest beacon ID, and the type of emergency.  
         [0058]    As shown in the circuit in FIG. 4, the beacon transmitters are not required to be attached to any common network, and transmit a unique Beacon ID number at regular intervals. The beacons may employ infrared, RF, or ultrasonic energy to transmit their ID in to the local area. In the embodiment shown, each beacon transmitter includes a processor  100  with program memory  90  and a beacon ID memory  95  for introducing unique beacon identifying signals to the processor  100 . The processor output is encoded at encoder  105  and sent to the various transmitters such as the IR transmitter  110 , the RF transmitter  115 , or the ultrasonic transmitter  120  and the like. A typical sequence is shown in the flowchart of FIG. 4, showing that once the timer is initialized the beacon identification signal will be blocked from transmission until the expiration of a preselected timer interval,  
         [0059]    In FIG. 5, an enhanced personal alarm is equipped with a beacon receiver, using infrared, RF, or ultrasonic methods as in the case of the beacon. The personal alarm unit receives and stores the ID number of the nearest beacon, as indicated at beacon receiver  135 . The personal alarm unit receives the identifying signal from the beacon via beacon receiver  135 . The beacon ID number is decoded by beacon decoder  145  and introduced into the unit processor at  150 . As in the embodiment of FIG. 1 the program memory  125  and device ID memory  130  provide device specific identify data to the processor. When one of the switches S 1 , S 2 , or S 3  is depressed, processor  150  formulates a message containing the personal alarm ID, the most recent beacon ID, and an indication of which switch was pressed. In this embodiment the encoder  155  encodes the processor output and introduces it to the transmitter  160  for wireless transmission via the antenna  165 . The microphone  140  permits direct audio input to the system from the unit. Audio may be transmitted in analog form, or may be digitized by AID converter  141  and compressed by compressor  142 , thence transmitted digitally. The unit is shown at  170  and includes the activation switches S 1 , S 2 , S 3 , the microphone  140  and the antenna  165 .  
         [0060]    Optionally, the personal alarm may store more than one beacon ID number for those cases where the personal alarm unit is moving through the facility, or may be in an area covered by more than one beacon.  
         [0061]    It will be noted that the receiver is programmed to listen for or sense beacons and to store the last one detected. Then if a panic button is pressed when the panic button unit IS NOT in range of a beacon, the last know beacon ID will be used for transmission of location. This would perhaps not send the exact location, but would be close because it is the last substantiated location. As shown in FIGS. 6A and 6B, the personal alarm units may operate in either a continuous fashion, or in an as-needed fashion. In FIG. 6A, the personal alarm periodically sends it&#39;s unit ID number, last beacon ID number(s), and emergency ID number (if any). In FIG. 6B, the personal alarm transmits only when one of switches S 1  S 3  are activated. The beacon generators do not necessarily need to be networked, which permits that common power be used. Networked beacon generators require network wiring, or wireless network infrastructure. The utility of the system may be greatly enhanced by connecting all the facility&#39;s beacon units to a common network, as depicted in FIG. 7. In this enhancement, the beacon transmitter of FIG. 4 is equipped with a wireless receiver, to receive transmissions from personal alarm units within it&#39;s immediate area. Additionally, the beacon transmitter/receiver is connected to a network or LAN serving the facility, allowing emergency transmissions from personal alarm units to be disseminated throughout the network. As before, the beacon transmits its unique beacon ID number into the local area, again using infrared, RF, or ultrasonic methods, as indicated by the antenna  180  and RF transmitter  185 , the IR transmitter  190  and generator  195 , ultrasonic transducer  205  and generator  200 , respectively. The beacon ID memory is provided by a discrete memory circuit  235 . Additionally, the beacon unit of FIG. 7 has a RF receiver  215  with antenna  210 , capable of receiving the transmissions from the personal alarm units of FIG. 1 or FIG. 5, if any, located within its immediate area. The signal received and demodulated by the wireless receiver  215  is decoded at decoder  225  and introduced into the processor  230 . The processor formulates a message containing the personal alarm ID, alarm type, and beacon number transmitted by the personal alarm unit. This message is introduced to the network  245  via the network interface  240  for transmission to the monitoring station  250 . The antenna  255  provides the means for transmitting and receiving signals from the RF transmitter  265  and the RF receiver  270  via a transmitter/receiver switch  260 , permitting reduction of circuit redundancies. Since each beacon unit has it&#39;s own wireless receiver for receiving emergency transmissions from the personal alarm units, the beacon units may supplement or replace the facility-wide RF receivers depicted in FIG. 3.  
         [0062]    In an alternative embodiment, the dual antennas  180  and  210  in FIG. 7 may be replaced by a single shared antenna. In this embodiment, a transmit/receive switch  260  connects antenna  255  to either transmitter  265  or receiver  270 . As before, the output signal from encoder  220  is passed to the RF transmitter  255 , whilst the output from RF receiver  270  is passed to decoder  225  for decoding.  
         [0063]    As shown in the flowchart of FIG. 8, the beacons transmit their beacon ID at regular intervals, based on an internal timer. The beacon may additionally transmit its beacon ID upon request from the monitoring station(s). The personal alarm units from FIG. 5 may interact with the networked beacon of FIG. 7 according to the flowcharts of FIG. 9A and FIG. 9B. In FIG. 9A, the personal alarm unit receives the beacon signal, decodes the beacon ID number, waits for a unique time interval to pass, then encodes and sends it&#39;s unit ID, received beacon ID, and emergency ID (if any). The unique time interval is derived from the personal alarm unit&#39;s ID number, such that no two personal alarm units will have the same interval. That prevents the case where multiple personal alarm units respond to the beacon at the same instant, and thereby mutually interfere.  
         [0064]    In FIG. 9B, the personal alarm unit responds to a beacon&#39;s transmission, as before. Additionally, the personal alarm contains a timer that determines when an excessive time has elapsed with no beacon signal received. Upon this detection of beacon loss, the personal alarm transmits it&#39;s unit ID number, last-heard beacon ID number, and emergency ID (if any) at periodic intervals. A facility-wide receiver as in FIG. 3 may receive such transmissions.  
         [0065]    [0065]FIG. 10 depicts a beacon transmitter/receiver housed in a wall clock. Suitable network time protocols may be employed to accurately time-stamp received alarms, as well as to set the clock. The time stamped location data thus derived may be useful in reconstructing a person&#39;s movements around the facility. As shown, the beacon signal may be transmitted using RF techniques (transmitter  280  and antenna  275 ), IR techniques (transmitter  290  and diode  285 ) or ultrasonic techniques (transducer  310  and generator  305 ). As previously described, the panic button may transmit an ID signal to the system via the antenna  315  and the wireless receiver  320  (such as the networked appliance as shown and described in my aforementioned U.S. patent application Ser. No. *******). The encoder  295  and decoder  300  are connected to the processor  325 , as previously described, for providing a signal link to the network  340  and monitor  345  via the network interface  335 . The clock configuration is shown at  346  with a digital clock display such as LED, LCD or electrolumenescent  347  and the signal antenna  275 .  
         [0066]    In another embodiment for implementing the geo-location system where there is no beacon, but there are networked receiver appliances available the panic button will send a continuous signal, allowing continuous location determination via the networked appliance for automatic call dispatch and other responses as described. In the alternative, the panic button signal will be generated only when a button is pushed, with the receiving networked appliance providing the location information.  
         [0067]    As illustrated in FIG. 11, large enclosed areas such as auditoriums or gymnasiums (the outer boundaries or walls of which are shown as line  350 ) multiple beacons may be employed. As depicted in FIG. 11, the beacons B 1 , B 2 , B 3 , B 4  are deployed so as to have overlapping areas of coverage, such that a personal alarm unit is always within range of at least one beacon. Activated, the personal alarm unit can transmit the beacon ID number of all beacons it currently receives, or make a decision about the ID that is transmitted based on signal strength, frequency of beacon receptions, or other criteria.  
         [0068]    [0068]FIG. 12 depicts an adaptation of the system to support usage in a large outdoor area such as a stadium. Such an area may be beyond the range of the beacon transmitters, such that the personal alarm unit  400  does not have any beacon location information available to send upon demand. In this instance, the personal alarm unit is supplemented with a GPS receiver  355 . When the alarm is activated by activation of switches S 1 , S 2  or S 3 , or periodically activated by the processor  375  at predetermined intervals, the personal alarm unit sends its unit ID number and other identifying information from memories  365  and  360 , GPS coordinates from receiver  355 , and emergency code as indicated by the selection of switch S 1 , S 2  or S 3  (if any). For improved accuracy, the GPS data may be supplemented with DGPS correction data. The processed signals communicate with the system receiver via encoder  380 , transmitter  390  and antenna  395 .  
         [0069]    An office button  54  may also be included. In the illustrated embodiment this is an intercom activation button permitting audio transmission between the unit and the office either directly through the unit or by remotely activating the networked intercom appliance in the operating range of the unit. This can be used in both emergency and non-emergency situations, using the microphone on the unit to send audio, and the nearest speaker to receive audio. The unit could also have a numeric keypad (not illustrated) so that intercom numbers can be dialed.  
         [0070]    [0070]FIG. 13 depicts an adaptation of the system of FIG. 1 wherein the personal alarm  5  uses an ultrasonic transducer  410  to transmit encoded information to a nearby receiver. The example personal alarm unit  5  has four switches or pushbuttons S 1 -S 4 , which are labeled, by way of example, FIRE, SECURITY, MEDICAL, and OFFICE. Other functions may be included without departing from the intent and spirit of the invention. When a pushbutton is depressed, the processor  10  retrieves the unique device identification number from memory  20 . The processor subsequently composes a short message containing the device ID and data describing which button was pressed by the user. This message is then encoded by the encoder  25  and transmitted by the transmitter  35  and the ultrasonic transducer  410 .  
         [0071]    The transmitted message is received, processed, and disseminated by the room appliance  480  as shown in FIG. 14. The ultrasonic transducer  415  receives the transmitted signal. The signal is decoded by the decoder  420  and interpreted by processor  425 . The processor then composes a short message containing the identification number transmitted by the personal alarm, the location of the receiving appliance, and where applicable, the type of message transmitted. The message may be sent to a number of appropriate monitoring stations anywhere on the network.  
         [0072]    Optionally, the room appliance may contain a variety of related devices and functions as described more fully in my aforementioned co-pending application entitled: Networked Room Appliance For example, the appliance  480  includes a motion detector  435  and a smoke detector  440 . Conditions detected by these detectors, such as a fire or a motion detected after hours, are sent to the processor  425  which then generates a signal for alerting an appropriate monitoring station  490  or  495  via the network interface  430  and the network  485 . A video camera  445  and encoder  450  may be commanded to capture and transmit visual images from the room to the monitoring stations  490  or  495 . The microphone  455  and associated audio encoder  460  may be commanded to capture ambient sounds and likewise transmit them to the monitoring stations  490  and/or  495 . Conversely, the user at monitoring station  490  or  495  may speak to occupants of the room via the intervening network  485 , processor  425 , audio decoder  470  and loudspeaker  465 . The appliance  480  may also contain an information display  475  capable of displaying useful information generated by a device on the network or by a monitoring station  490  or  495 . A common use of the display  475  would be a simple time-of-day clock.  
         [0073]    [0073]FIG. 15 depicts operation of the system. A user  565  presses a pushbutton on the personal alarm unit  510 . The personal alarm composes and transmits the appropriate message, which is received and decoded by appliance  500 .  
         [0074]    The appliance  500  forwards the message in a manner appropriate for the type of condition or emergency, as defined by the specific pushbutton activated on the alarm unit  510 . For example, if the user  5654  pressed the FIRE pushbutton, the appliance will notify the fire department  540  and the signal will identify the location of the of the person reporting the fire as well as the identity of the personal alarm unit sending the message via signals sent over the intervening network  570 . The appliance additionally may enable the microphone and/or video camera housed within the appliance  500 , permitting the fire department to further evaluate the nature and magnitude of the emergency.  
         [0075]    If the user  565  pressed the MEDICAL pushbutton, the appliance  500  alerts the nurse station  520  of the location and identity of the user, again via the intervening network  570 . Similarly, the office  535  may be notified and/or the guard station  545 . In each case, the location and identity of the sender is transmitted to the appropriate monitoring stations. The audio and video capability of the room appliance will also permit further verification of the user and further audio with which to evaluate the extent of the emergency, which is to be handled.  
         [0076]    In the embodiment shown the guard station  545  is equipped with several additional enhancements, including the microphone  555 , the push-to-talk switch  550 , and the speaker  560 . When the guard station  545  receives a personal alert alarm signal, the microphone of appliance  500  may be remotely activated, permitting the guard station to monitor audio signals in the vicinity of the appliance for further evaluation of the events. The guard station personnel may also audibly communicate with personnel in the room using the push-to-talk feature and station microphone  555 . The system would route the push-to-talk audio form the station microphone to one or more appliances such as  500  that are in the immediate area of the personal alert unit. Any of the messages generated by the appliance  500  may also be transmitted to a server  515  for archival and logging functions, as well as audio and commands generated by responding guard stations, fire stations, or other stations.  
         [0077]    The various guard stations and other stations with microphones may also have “voice activated” push to-talk-which would automatically, based on voice level and/or duration criteria, generate the push-to-talk signals which would open up the microphone to be transmitted to the selected speaker(s) on various room appliances. For this invention, “push-to-talk” is defined as being either manual switch pushes such as on a microphone button or a computer mouse switch, or voice activated switching.  
         [0078]    While certain features and embodiments of the invention have been described in detail herein, it will be readily understood that the invention includes all modifications and enhancements within the scope and spirit of the following claims.