Abstract:
An emergency alert system comprising one or more access-controlled wireless transmitters and a plurality of wireless wearable receivers that can be deployed locally to privately warn users of potential danger, by allowing authorized users to use the transmitters to send alert signals to the receivers.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a divisional of U.S. Ser. No. 13/906,409, filed May 31, 2013 and currently pending, entitled WIRELESS SAFETY ALERT SIGNALING SYSTEM, by Patti A. Rapaport, et al., which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates generally to wireless transmitters and receivers. More particularly, the present invention relates to an emergency alert system that can be deployed locally to warn users of potential danger, by employing access-controlled transmitting units that wirelessly transmit alert signals to wearable receiver units. 
         [0004]    2. Description of Prior Art 
         [0005]    In the aftermath of the tragedy at Sandy Hook Elementary School in Newtown, Conn., there has been a dramatic push to improve school safety. School violence is on the rise. A review of the data shows that since 1980, in the United States alone, there have been a total of 137 school shootings, each resulting in the death of least one victim, and these numbers have risen each decade 1 .  1  Kirk, Chris (Dec. 19, 2012), “Since 1980, 297 People Have Been Killed in School Shootings”: Slate. 
         [0006]    In March of 2013, in response to the need for immediate school-level funding support, the United States Department of Homeland Security opened up grant opportunities to allow school districts to purchase and install remotely-controlled entry access systems, panic buttons that are hard-wired to law enforcement agencies, “Knox Boxes” to safely secure keys for first responders, and exterior door numbering to assist first responders in situational awareness 2 . Each of these options has merit because it offers the same thing: time. Either slowing down the attacker or speeding up the external response gains time. Nationally, the focus has been on issues surrounding guns; banning specific types, requiring background checks, limiting magazine capacity and, even, arming teachers. Interestingly, bans on assault weapons and high-capacity ammunition magazines are also time related.  2  Maine Emergency Management Agency (Mar. 18, 2013), “School Security Funding Opportunity For School Administrative Units”: www.Maine.gov. 
         [0007]    While there are many security improvements and additional safety devices that have been developed, improved upon, and employed in the name of school safety, none adequately serve to notify all persons in the building or on the grounds of the safety concern. The signal typically comes from the main office, or main point of entry, through the intercom system. If the ability to use the intercom is compromised, which is often the case, effectively implementing a lockdown becomes unlikely. Furthermore, announcing a lockdown over the intercom could serve to intensify certain situations and diminish opportunities for peaceful resolutions. 
         [0008]    There have been several developments in technology that can help tighten security, but they commonly involve costly equipment and construction, and are often dependent on wireless capabilities that are still not available in many rural areas. Also, the panic buttons that exist in businesses and, more recently, schools only serve to notify police and security personnel of a potential crisis and do not notify those on the premises. Additionally, remote areas without local law enforcement may have exceptionally long response times. While signaling for help can be of critical importance, lives may be lost before its arrival. Ideally, notifying the people inside the building as well as law enforcement should be both silent and simultaneous. 
         [0009]    Most schools have Comprehensive Emergency Plans that are designed to address multiple scenarios, and being capable of immediately notifying the staff of the danger increases the chances for successful implementation of the plan. If the location is also known, the opportunities to save lives are dramatically increased. For example, if the PE teacher knew there was a problem in the main office he/she could make a decision based on the situation. In this example, possible options could be to execute the lockdown procedure, evacuate through rear of gym, or possibly, prepare to confront an attacker. Time needs to be available to those confronting the situation at the school, because they are responsible for the safety of the children. 
         [0010]    There is thus demonstrated the need for a system that can be deployed to provide early warning of potential danger to all persons subject to that danger. While the primary purpose for such a system is to improve school safety, the system is also useful in other settings, such as businesses, health care institutions, and other settings that potentially may be targets of attack. 
         [0011]    It is thus an object of the present invention to present a wireless safety alert signaling system. 
         [0012]    It is a further object of the present invention to present a wireless safety alert signaling system that silently alerts all persons present in the immediate area of danger. 
         [0013]    It is yet a further object of the present invention to present a wireless safety alert signaling system that uses multiple transmitters dispersed about the premises to provide easy access to persons to initiate warnings. 
         [0014]    It is yet a further object of the present invention to present a wireless safety alert signaling system that uses multiple wearable receivers that can simultaneously receive danger warnings. 
         [0015]    It is yet a further object of the present invention to present a wireless safety alert signaling system that employs key devices to provide access control of the transmitters so that only authorized persons can initiate a danger warning signal. 
         [0016]    It is yet a further object of the present invention to present a wireless safety alert signaling system that does not rely upon hard wired communications systems, such as intercoms. 
         [0017]    It is yet a further object of the present invention to present a wireless safety alert signaling system that does not rely upon cellular telephone communications technology. 
         [0018]    It is yet a further object of the present invention to present a wireless safety alert signaling system that is simple to use. 
         [0019]    It is yet a further object of the present invention to present a wireless safety alert signaling system that is inexpensive to manufacture and deploy. 
         [0020]    Other objects of the present invention will be readily apparent from the description that follows. 
       SUMMARY OF THE INVENTION 
       [0021]    The present invention discloses a wireless safety alert signaling system having one or more transmitters, a plurality of wearable receivers, and a key means used to allow only authorized users to access the one or more transmitters to initiate transmission of warning signals. Upon activation, a transmitter sends a wireless radio signal to all receivers simultaneously. The receivers are provided with one or more human perceptible indicators, such as lamps or vibrators, so that a user wearing a receiver can be privately alerted to the potential danger upon receipt of a signal from a transmitter. The meaning of the indicators can be determined by local protocol, so that a flashing lamp might have one meaning in one context but another meaning in another context. Where multiple transmitters are used, they may be deployed in various strategic locations to provide for rapid access by authorized personnel. The key means prevents unauthorized use of the transmitters. An example would be multiple transmitters deployed throughout a school building, much like fire alarm pull boxes. Since only authorized persons such as teachers, administrators, and staff would be provided key means, the risk that the transmitters would be misused to send spurious warnings, for example, by students or visitors, is minimized. 
         [0022]    The key means can be implemented using a variety of technologies, such as a traditional physical key and lock used to unlock a secured unit; a magnetic strip that is read by a magnetic strip reader; a code input using a data entry keypad; or a body part scanned by a biometric reader. Where the key means is a magnetic strip, it can be integrated with the receiver, so that any person authorized to wear a receiver can also activate a transmitter. Alternatively, only certain receivers may have integrated key means, for example, where only trained personnel (and not visitors or substitute teachers) have access to the transmitters. 
         [0023]    In the preferred embodiment, the receivers are integrated with common objects readily associated with users, such as security or identification badges, badge holders, and the like. In a school context, each adult on the premises can be given a small device that will flash and/or vibrate to signal a safety concern or immediate danger. For example, temporary employees/substitutes and visitors/volunteers could easily be given a receiver while on the premises. Most school districts and other large organizations now require employees to wear identification badges, so combining this safety requirement with an additional safety device is a logical and simple expectation. These devices can have many different configurations, but it is essential that they are easily mobile and small enough to be clipped onto clothing, worn as a badge, worn around the neck, or kept in a pocket. 
         [0024]    For purposes of illustration, the system of the present invention may be deployed in a school building by placing the transmitters in offices, classrooms, and hallways. The key means may be integrated with the receivers and configured as security badges to be worn by all adults present on the premises. Upon a threat of danger, a person wearing a badge having an integrated magnetic strip-enabled key goes to a transmitter and swipes the badge in the magnetic strip reader integrated with the transmitter, thereby unlocking the transmitter, and then activates a switch which initiates transmission of a warning signal simultaneously to all of the receivers. Once activated the receivers will flash and/or vibrate. This alert can serve to notify everyone that the premises are under lockdown, or whatever procedure corresponds to the school&#39;s plan. Potentially, different flashing colors or patterns can be activated by selecting the appropriate switch or button on a transmitter to signal different procedures. For example, a flashing and vibrating red signal could signify a lockdown protocol while a blue signal could signify a “shelter in place” protocol, or one color alerts to danger inside the building and another notifies of an outside danger. With this information students inside could be quietly evacuated or secured in their classrooms, and students outside could be kept away or brought inside, depending on the signal and the associated protocol. 
         [0025]    The cost of the system will be relatively inexpensive and affordable for the smallest school districts, and the individual receiver units can easily be replaced. While the systems can be very detailed and elaborate, a simple version of the device is all that is necessary to alert the staff of the presence of danger. This is essential for remote schools having the greatest need to activate their emergency plans, because help may not be available in a reasonable amount of time. 
         [0026]    It is to be understood that the foregoing and following description of the invention is intended to be illustrative and exemplary rather than restrictive of the invention as claimed. These and other aspects, advantages, and features of the invention will become apparent to those skilled in the art after review of the entire specification, accompanying figures, and claims incorporated herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a schematic view of one embodiment of a transmitter of the present invention, with a cutaway portion revealing interior components. 
           [0028]      FIG. 2  is a schematic view of one embodiment of a receiver of the present invention, with a cutaway portion revealing interior components. 
           [0029]      FIG. 3  is a schematic representation of the system of the present invention in use, with one user activating a transmitter and all users receiving warning signals as a result. 
           [0030]      FIG. 4  is a schematic view of another embodiment of a receiver of the present invention, having a magnetic strip key means and a plurality of lamps, the receiver and key means integrated with a security badge. 
           [0031]      FIG. 5  is a schematic view of yet another embodiment of a transmitter of the present invention, having a biometric (thumb print) reader locking means and a data entry keypad activating means, a selectable switch, and an alternative key means of a magnetic strip reader. 
           [0032]      FIG. 6  is a schematic view of yet another embodiment of a receiver of the present invention, being integrated with a security badge (but without a key means). 
           [0033]      FIG. 7  is a schematic view of yet another embodiment of a receiver of the present invention, the receiver and key means integrated with a badge holder. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    The wireless safety alert signaling system  1  of the present invention comprises a transmitter  100 , a receiver  200 , and a key means  300 . The transmitter  100  serves to generate and transmit one or more distinct wireless signals upon a user  10  taking an initiating action. The receiver  200  serves to receive the one or more distinct signals and to provide a human perceptible indication of the receipt of the one or more signals to one or more other users  10 . The key means  300  allows a user  10  to access the transmitter  100 ; only users  10  with the key means  300  will be allowed access to the transmitter  100 . This allows the transmitter  100  to be placed in a public, readily accessible location, while preventing unauthorized use. 
         [0035]    The transmitter  100  further comprises a transmitting means  110 , an activating means  120 , and a locking means  130 . See  FIG. 1 . The transmitter  100  will also have a power supply  70 . This may be a hard-wired connection to an electrical system, or may include an electrical cord configured to be placed into an electrical outlet, or may comprise one or more rechargeable or replaceable batteries, or may comprise a solar panel, or any other suitable power source. The transmitter  100  further may be housed within a casing  80 , with the casing  80  made of any suitable material, such as plastic, composites, metal, alloys, and the like. 
         [0036]    The transmitter casing  80  may be further configured for mounting on a wall, or it may be placed on a surface, such as a shelf, on the floor, on a desk, or even inside a drawer. If the transmitter  100  will be mounted outdoors, the casing  80  should be configured in a watertight manner, as is well known in the art. The transmitting means  110 , the locking means  130 , and the power supply  70  may be contained within the casing  80 . See  FIG. 1 . The activating means  120  should be located on an exterior surface of the casing  80  for ready access. See  FIGS. 1  and  5 . In some configurations the locking means  130  may also be located on an exterior surface of the casing  70 . See  FIG. 5 . 
         [0037]    The transmitting means  110  of the transmitter  100  is configured to generate and wirelessly transmit signals. This may be accomplished by any means known in the art. In the preferred embodiment the transmitting means  110  is a radio transmitter  112 , and the signals wirelessly transmitted by the transmitting means  110  are radio signals  20 . See  FIGS. 1 and 3 . 
         [0038]    The activating means  120  of the transmitter  100  is configured to allow a user  10  to initiate the generation and transmission of signals by the transmitter  100 . In one embodiment, the activating means  110  comprises a push button  122 . When the activating means  110  is operable, a user  10  may initiate the generation and transmission of signals by the transmitter  100  by depressing the push button  122 . In another embodiment, the activating means  110  comprises a data entry keypad  128 . See  FIG. 5 . When the activating means  110  is operable, a user  10  may initiate the generation and transmission of signals by the data entry keypad  128  by entering a correct key stroke or series of keystrokes. In yet other embodiments, the activating means  110  comprises a toggle switch, or a key-in-lock mechanism, or a sliding switch, or any other practical configuration that allows a user  10  to activate the transmitter  100 . 
         [0039]    In some embodiments of the present invention, the activating means  120  of the transmitter  100  is configured to allow the user  10  to initiate the generation and transmission of a plurality of distinct signals by the transmitter  100 . This is useful in that the system  1  can then be used to convey more information, depending on the signal sent. Where, for example, a system  1  having only one type of signal can convey the message “Danger!”, a system  1  having a plurality of distinct signals can convey several types of messages, such as “Danger! Evacuate!” or “Danger! Shelter in place!” or “Warning! Suspicious person outside premises” or “Warning! Suspicious person inside premises”. Transmitters  100  capable of generating and transmitting a plurality of distinct signals are well known in the art. 
         [0040]    In one such embodiment, the activating means  120  of the transmitter  100  comprises a plurality of push buttons  122 , with each push button  122  corresponding to one of the plurality of distinct signals the transmitter  100  is configured to generate and transmit. Upon the user  10  depressing one of the push buttons  122 , the transmitter  100  generates and transmits one of the plurality of distinct signals corresponding to that push button  122 . 
         [0041]    In another embodiment, the activating means  120  comprises a selectable switch  124  and a push button  122 , with the switch  124  configured to select among one of the plurality of distinct signals and the push button  122  configured to initiate the generation and transmission of the particular signal selected by the user  10  via the switch  124 . See  FIG. 5 . Upon the user  10  selecting a distinct signal by use of the switch  124  and then depressing the push button  122  the transmitter  100  generates and transmits the particular signal corresponding to the selection indicated by the switch  124 . The switch  124  may be in the form of a dial, or a slider, or any other well known devices enabling a user  10  to select one item out of a range of choices. The push button  122  may be integrated with the switch  124  (whereby the switch  124  may be both moved and depressed), or a separate component. 
         [0042]    In yet another embodiment, the activating means  120  comprises a data entry keypad  128  configured to select among one of the plurality of distinct signals and to initiate the generation and transmission of the selected signal. See  FIG. 5 . The user  10  selects a distinct signal by keying in, for example, an index number that corresponds to a particular signal. Using the example provided above, the key code “01” could correspond to the message “Danger! Evacuate!”, the key code “02” could correspond to the message “Danger! Shelter in place!”, etc. Upon the user  10  entering the appropriate information into the data entry keypad  128  the transmitter  100  generates and transmits the particular signal corresponding to the selection made. 
         [0043]    In yet another embodiments, the activating means  110  may comprise a number of toggle switches, each corresponding to a particular signal, or a series of sliding switches, or any other practical configuration that allows a user  10  to select from a plurality of distinct signals and to activate the transmitter  100  to generate and transmit the selected signal. 
         [0044]    The locking means  130  of the transmitter  100  is configured to place the transmitter  100  in unlocked mode or in locked mode. When the transmitter  100  is in unlocked mode the activating means  120  of the transmitter  100  is operable by the user  10 . When the transmitter  100  is in locked mode the activating means  120  of the transmitter  100  is inoperable by the user  10 . Inoperability is desired to prevent unauthorized persons from activating the transmitter  100 . The key means  300  is manipulated by the user  10  and is configured to interact with the locking means  130  of the transmitter such that the interaction of the key means  300  with the locking means  130  places the transmitter  100  in unlocked mode. In one embodiment the key means  300  comprises a plurality of key devices  310 . Each key device  310  is configured to interact with the locking means  130  of the transmitter  100 , with any one of the plurality of key devices  310  being capable of being used to place the transmitter  100  in unlocked mode. 
         [0045]    In one embodiment, the locking means  130  of the transmitter  100  comprises a magnetic strip reader  132 , see  FIG. 5 , and the key means  300  comprises a magnetic strip  302 , see  FIG. 4 . The magnetic strip  302  is coded with an access code recognizable to the locking means  130 . When the magnetic strip  302  is brought into contact with the magnetic strip reader  132  and the embedded code is recognized, the locking means  130  places the transmitter  100  in unlocked mode. The key means  300  may comprise a plurality of key devices  310 , where each key device comprises a magnetic strip  302  and all of the magnetic strips  302  of the key devices  310  are coded with the same access code recognizable to the magnetic strip reader  132 . 
         [0046]    In another embodiment, the locking means  130  of the transmitter  100  comprises a biometric reader  136 . See  FIG. 5 . The key means  300  in this embodiment comprises a body part of the user  10  which is coded into the biometric reader  136 . For example, if the biometric reader  136  is a thumbprint scanner, the key means  300  will be the thumbprints of the approved users  10 . Similarly, if the biometric reader  136  is a retina scanner, the key means  300  will be the retinas of the approved users  10 . Any of the biometric readers  136  known in the art may be used, as long as the biometric reader  136  is capable of recognizing the designated body part of the user  10 . When the body part of an authorized user  10  interacts with the biometric reader  136  the locking means  130  places the transmitter  100  in unlocked mode. 
         [0047]    In yet another embodiment, the locking means  130  of the transmitter  100  comprises a data entry keypad and a digital lock. The key means  300  in this embodiment comprises a code provided to the approved users  10  which is coded into the digital lock such that the code is recognized by the digital lock. When the user  10  enters the code into the data entry keypad the locking means  130  places the transmitter  100  in unlocked mode. The code may be any combination of alpha-numeric or special characters, or symbolic characters, or the like. In yet another embodiment a single data entry keypad can be used as a component of both the activating means  110  and the locking means  130 . 
         [0048]    In yet another embodiment, the locking means  130  of the transmitter  100  comprises a traditional lock and the key means  300  comprises a traditional key. When the user  10  inserts the key into the lock and unlocks the transmitter  100  the locking means  130  places the transmitter  100  in unlocked mode. 
         [0049]    The receiver  200  of the present invention further comprises a receiving means  210  and an indicating means  220 . See  FIG. 2 . The receiver  200  may also have a power supply  70 , though this is an optional requirement, depending on the specific configuration of the receiver  200 . If a power supply  70  is present, it may be one or more low profile batteries or a solar panel, or any other suitable power source. The receiver  200  further may be housed within a casing, with the casing made of any suitable material, such as plastic, composites, metal, alloys, and the like. The receiver casing will be configured such that it can be worn by a user  10 . If a power supply  70  is used it may be contained within the receiver casing. 
         [0050]    The receiving means  210  of the receiver  200  is configured to receive wirelessly transmit signals transmitted by the transmitting means  110  of the transmitter  100 . This may be accomplished by any means known in the art. In the preferred embodiment the receiving means  210  is a radio receiver  212 , and the signals wirelessly received by the receiving means  210  are radio signals  20 . See  FIG. 3 . 
         [0051]    The indicating means  220  of the receiver  200  is configured to provide at least one human perceptible indication when the receiving means  210  of the receiver  200  receives a wirelessly transmitted signal. In one embodiment, the human perceptible indication is achieved through the use of a lamp  222 . See  FIGS. 2, 4, 6, and 7 . The lamp  222  is illuminated upon the receiver  200  receiving a signal. The lamp  222  may be any practical configuration known in the art. In the preferred embodiment it is a light emitting diode (LED). The lamp  222  may be colorless or colored. 
         [0052]    In another embodiment, the human perceptible indication is achieved through the use of a vibratory means  224 . See  FIG. 2 . The vibratory means  224  is activated upon the receiver  200  receiving a signal. The vibratory means  224  may be any practical configuration known in the art that causes a vibration that is perceptible to a user  10 . 
         [0053]    In yet another embodiment, the human perceptible indication is achieved through the use of an audio means. The audio means is activated upon the receiver  200  receiving a signal. The audio means may be any practical configuration known in the art that creates a sound that is perceptible to a user  10 . An example may be an electrical tone generator, a buzzer, or the like. 
         [0054]    In the preferred embodiment, the indicating means  220  of the receiver  200  is configured to provide a plurality of human perceptible indications. This may include a plurality of lamps  222 , or a combination of a lamp  222  and a vibratory means  224 , or a lamp  222  and a buzzer, etc. The preferred combination of a plurality of lamps  222  plus a vibratory means  224  allows the user  10  to be alerted to the transmission of a signal whether the user  10  is looking directly at the receiver  200  or not (through the vibratory means  224 ), while still providing the ability to discern from different messages (through the plurality of lamps  222 ). 
         [0055]    Where the indicating means  220  comprises a plurality of lamps  222 , in one embodiment each of the lamps  222  has a different color than each other lamp  222 . Each lamp  222  corresponds to one of the plurality of distinct signals transmitted by the transmitter  100  and is associated with a particular message. Using the example provided above, the red lamp  222  could correspond to the message “Danger! Evacuate!”, the blue lamp  222  could correspond to the message “Danger! Shelter in place!”, etc. In yet another embodiment, the plurality of lamps  222  is configured to be illuminated in a plurality of different patterns. Each pattern corresponds to one of the plurality of distinct signals transmitted by the transmitter  100  and is associated with a particular message. For example, three lamps  222  with all three in constant illumination could correspond to the message “Danger! Evacuate!”, three lamps  222  with only two in constant illumination could correspond to the message “Danger! Shelter in place!”, three lamps  222  blinking in succession could correspond to the message “All Clear”, etc. Where only a single lamp  222  is used, an illumination pattern still could be employed to convey a limited number of messages, such as constant on, fast blink, and slow blink. 
         [0056]    The indicating means  220  of the receiver  200  may remain active after the receipt of a warning signal until affirmatively deactivated, for example, by use of an “off” switch or by removing the battery. Alternatively, the indicating means  220  of the receiver  200  may remain active after the receipt of a warning signal only for a predetermined period of time, and then automatically become deactivated until another warning signal is received. This is preferred as it allows an “All Clear” signal to be sent in appropriate circumstances. 
         [0057]    In preferred embodiments the receiver  200  is wearable by the user  10 . In one embodiment the receiver  200  is integrated with a security badge  30  or an identification badge. See  FIGS. 4 and 6 . This allows a receiver  200  to be provided to every user  10  who is ordinarily provided a badge, and eliminates the need to provide a separate device. In another embodiment the receiver  200  is integrated with a security badge holder  40 . See  FIG. 7 . This has the advantage of providing a larger form factor for the receiver  200 , while still retaining the advantages of each user  10  being provided a receiver  200 . In yet other embodiments the receiver  200  is configured to be worn on a necklace  50  or a lanyard. See  FIG. 3 . This configuration has similar benefits as the configuration integrating the receiver  200  with a badge holder  40 , but also provides receivers  200  to users  10  who might not ordinarily require a badge  30 . In another embodiment the receiver  200  is configured to be clipped to an article of clothing. In yet another embodiment the receiver  200  is configured as a fob suitably adapted to be placed in a pocket of an article of clothing. In this embodiment the indicating means  220  of the receiver  200  comprises at least a vibratory means  224 , so that when a signal is transmitted by a transmitter  100  the vibratory means  224  is activated and the user  10  will perceive the signal. 
         [0058]    In a most preferred embodiment, the system  1  comprises a plurality of transmitters  100 . See  FIG. 3 . This allows transmitters  100  to be placed in many different locations, both public and private, allowing for quicker access to the transmitters  100  in an emergency. Each of the plurality of transmitters  100  may be configured as described above, and generates the same one or more wireless signals that are receivable by the receiver. 
         [0059]    In another most preferred embodiment, the system  1  comprises a plurality of receivers  200 . See  FIG. 3 . This allows receivers  200  to be provided to a plurality of users  10 , increasing the likelihood that a warning message conveyed by a wireless signal transmitted by the transmitter  100  will be perceived as quickly as possible by as large a number of users  10  as possible. Each of the plurality of receivers  200  may be configured as described above. In this embodiment the key means  300  may also comprise a plurality of key devices  310 . These key devices  310  may be distributed to multiple authorized users  10 . An example of a key device  310  would be a plastic card having a magnetic strip  302 . In yet another embodiment, each of the plurality of key devices  310  is integrated with one of the plurality of receivers  200 . This allows multiple key devices  310  to be distributed together with the receivers  200 , so that multiple users  10  are provided with the ability of activating the one or more transmitters  100 . An example of this configuration would be a receiver  200  integrated with a security badge  30 . In one such embodiment every receiver  200  is integrated with a key device  310 . In other embodiments only some of the receivers  200  are integrated with a key device  310 . This might be useful in a situation where only some users  10  are trained in detecting and reporting danger, while all users  10  are intended recipients of warning signals. 
         [0060]    In the most preferred embodiment, the system  1  comprises a plurality of transmitters  100  and a plurality of receivers  200 , allowing any one of a number of transmitters  100  located advantageously to signal multiple users  10  simultaneously. See  FIG. 3 . An example of a system  1  configured in this manner would be a school building with transmitters  100  located in every classroom, administrative office, and hallway, and with all teachers, administrators, and staff wearing receivers  200 . At the first indication of danger, the nearest transmitter  100  would be activated and the appropriate signal would be sent to all users  10  wearing receivers  200 . Where some receivers  200  are integrated with key devices  310 , perhaps only teachers, administrators, and staff are assigned receivers  200  with integrated key devices  310 , while adult visitors to the school might be assigned receivers  200  without integrated key devices  310 , but would be given an explanation of how to interpret the indicating means  220 . Thus, visitors (and students) would not be able to activate the transmitters  100 , but trained school personnel would be able to activate the transmitters  100 , and all adults present would receive the warning signal. 
         [0061]    Modifications and variations can be made to the disclosed embodiments of the present invention without departing from the subject or spirit of the invention as defined in the following claims.