Abstract:
The present invention provides a portable monitoring device ( 1 ) for monitoring at least one physical parameter value of a user and transmitting a distress signal on the basis thereof, comprising at least one measuring means ( 4, 5 ) for measuring said at least physical parameter of a user; positioning means ( 6 ) for satellite based position sensing of said device; processing means ( 8 ) connected to said measuring means ( 4, 5 ) and said positioning means ( 6 ); radio communication means ( 10 ), connected to said processing means ( 8 ), for transmitting data and/or speech; characterized in that said positioning means ( 6 ) is configured to periodically determine a current position of said device ( 1 ), said at least one measuring means ( 4, 5 ) is configured to automatically sense said physical parameter value of said user, said processing means ( 8 ) is connected to said positioning ( 6 ) and said measuring ( 4, 5 ) means, and is further configured to read said at least one physical parameter value from said measuring means ( 4, 5 ) and to compare said at least one measured parameter value to predetermined threshold values; and wherein said processing means ( 8 ) is configured to generate said distress signal when said at least one measured parameter value falls outside said threshold values; said communication means ( 10 ) being configured to transmit said at least one sensed parameter value together with an identifier, along with current position data obtained by said positioning means ( 6 ), and said distress signal, respectively.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to a portable pulse monitoring device, module or mobile terminal device equipped with such a module for constantly measuring or sensing at least one or several physical parameters of a user, particularly pulse or heart rate, and simultaneously determining the position of said user via a satellite based positioning system and for sending out an emergency signal in case of an emergency condition determined by an excessive heart rate and the like, or more generally in case of deviations of measured physical parameter values when compared to predefined threshold values. The measured parameters and positions may be permanently transmitted to a remote server. The present invention further relates to the method of measuring the pulse and/or further physical parameters and determining the position of a user, transmitting those parameters to a remote server for further processing and transmitting an emergency signal when necessary.  
       BACKGROUND OF THE INVENTION AND PRIOR ART  
       [0002]     Users with known health problems such as cardiac dysrhythmia, high blood pressure or the like have an increased risk of life-threatening cardiovascular emergencies like a heart attack or stroke. In such an emergency a user might still be able to call for help, but due to following unconsciousness, partial paralysis or amentia he might not be able to fully and correctly indicate his current location. However, in all cardiovascular emergencies, the time period until life-support measures are undertaken by trained individuals is critical since permanent damage to heart, brains and vital organs occurs within only a few minutes after the cardiovascular incidence. It is therefore necessary to get help as fast as possible, thus requiring prompt notification of emergency medical services along with exact positioning of the patient.  
         [0003]     For diagnosis of the occurrence of a critical medical condition, medical monitors are widely used. Such monitors are capable of measuring one or more physical parameters of a patient and comparing measured parameter values to reference values, which may be defined by the user or medical staff. When the measured values exceed or fall below certain limits, a signal of any kind may be triggered which can lead medical personnel to take appropriate measures. However, most monitors of this kind require constant presence of medical personnel within the signal range of the monitor to ensure that someone will be able to react on a medical emergency. Alternatively, the user himself needs to call for help, such as an ambulance, when the monitor detects abnormal or critical parameter values. As stated above, the user might not be able to indicate his condition or location to rescue services.  
         [0004]     It is therefore desired to provide a device which monitors the medical condition of a user and which is capable of giving an alarm and call for professional help when necessary or more precisely, when physical parameter values measured by the device indicate a deterioration of a user&#39;s condition.  
         [0005]     Devices for measuring pulse and other physical parameters are widely used for medical monitoring purposes. Cuffs for electronically measuring blood pressure and pulse, as an example, are available for both home and professional use. Those usually comprise a inflatable cuff, a manometer unit and a pulse sensor of any kind, such as a microphone. Other medical monitors include e.g. ECG devices to record electrical currents of heartbeats, or non-invasive blood gas monitors to determine oxygen saturation in the blood. The latter may as well be capable of measuring the heartbeat rate. All these monitors are available as portable devices off-the-shelf.  
         [0006]     Similarly, mobile terminals or special emergency transmitters which can be used to call help in case of an emergency are well known. Typically they can be activated by a user by means of a key or button and cause an emergency signal to be sent to a predetermined corresponding receiver. Transmission of the emergency signal may for example be effected via a GSM network as a data signal or a conventional phone call to a number stored in the device, such as the local emergency telephone code or a phone number of a responsible caregiver. However, in general the user needs to activate the device himself and possibly talk to emergency services in order to specify his current condition and location.  
         [0007]     Satellite based positioning devices may presently be found in a multitude of instruments, either as single units or combined with further functionalities. The system currently used is GPS (Global Positioning System); another concurring system will be set up by the EADS/Astrium group and is planned to be operative in 2008. While the precision of GPS is already around 3 m, the future positioning system will supposedly give significantly better resolution. A satellite based positioning means typically comprises a receiver for receiving satellite signals. To determine a current position, signals of at least three positioning satellites need to be received and analysed. The signals received from orbital satellites each include a time signal given by an atomic clock on board of each satellite as well as the orbital elements of each satellite indicating its position. In practice, a fourth satellite signal is needed if the receiver does not include means for determining its exact time. The basic principles of satellite based positioning are well known in the art.  
         [0008]     A combination of measuring means, communication means and positioning means will provide a possibility of monitoring a user&#39;s condition and automatically notifying rescue services when an emergency has been detected with the ability to easily locate the user and thus to initiate life support measures as soon as possible.  
         [0009]     For similar purposes, WO 00/16288 discloses a protection and surveillance system for persons requiring assistance or protection using GPS based positioning, but without physical monitoring of any kind.  
         [0010]     Document DE 198 44 296 is an assembly for patient monitoring consisting of a sensor for physiological parameters and a signal processor, as well as a mobile terminal for communication in a cellular mobile communication network, which is capable of cell-based positioning of the mobile terminal on the basis of the respective base station used.  
         [0011]     WO 03/041290 gives an mobile phone with an alarm function, wherein an emergency light is activated and an alarm sound is generated when an alarm button is pushed. A user&#39;s heart rate may be measured by an included stethoscope unit, but heart rate monitoring or heart rate dependent alarm functionality are not provided.  
         [0012]     In the German patent application DE 196 39 492, an automatic help-activation system is disclosed, comprising a mobile phone and GPS system as well as certain measuring or sensing devices, which determines its position by GPS and activates itself when certain criteria are met.  
       SUMMARY OF THE INVENTION  
       [0013]     The object of the present invention is to provide a device, module and mobile terminal for monitoring vital signs as a pulse and for simultaneously determining the position of a user, particularly of a user with risk factors as mentioned above, said device also being capable of transmitting the measured data to a remote emergency center, so that in case of emergency an operator at said emergency center is able to give detailed stored information on location and medical condition of the user if abnormalities are detected and contact with the user cannot be established. Such a device should also be simple in handling for the user and provide additional functions to adapt to certain situations of daily life.  
         [0014]     The solution according to the invention provides a medical monitoring and alarm device, comprising a measuring means for physical parameters, typically provided in the form of a cuff or strap to apply to extremities or chest of a user, means for communication and data transmission to a remote emergency center, a processing means and a positioning means using satellite based positioning.  
         [0015]     To keep handling simple for the user, the monitoring device is automatically activated when the pulse measuring cuff or strap is applied, and it is deactivated in the same way when said cuff or strap is taken off. Any further steps and functions occur automatically and do not require intervention by the user.  
         [0016]     At predefined periodic intervals, measurements of physical user parameters are conducted automatically. In a preferred embodiment of the invention, the pulse of a user is measured periodically by using a cuff around arm or leg or a chest strap. Simultaneously the position of the user is determined via satellite based positioning. Threshold values are predefined at the monitoring device or at the server, to which measured parameter values are compared. When exceeding or falling below these threshold values, transmission of a distress signal is triggered.  
         [0017]     Three emergency levels may be defined to decide on the appropriate action to take: emergency level  1  indicates a situation in which pulse values are suddenly and/or essentially deviating from those stored as predefined standard or threshold values, but the reason or severity of those deviations is yet unknown; emergency level  2  is entered if a user cannot or does not respond to an emergency level  1  distress signal, i.e. if an attempt to establish contact with the user via a radio communication means is unsuccessful; and emergency level  3  indicates that the user himself has triggered the sending of a distress signal to the emergency center by suitable means present on the monitoring device. Therefore, emergency level  1  does not necessarily provoke the notification of a local rescue center, which would be unnecessary and undesired if the user was not in immediate need for help. When unusual parameter values have been detected, the emergency center is notified by sending a distress signal together with the transmitted physical parameters and positioning data. In response to the distress signal, an operator at the emergency center will attempt to make contact with the user through the transmission means and the included speaker and microphone. Thus the user will be able to give further information about his current condition; if he feels well, he can check, under guidance of the operator of the emergency center, whether a malfunction of the monitoring device caused the distress signal. In that case he can bring his device in for repair or alternatively adjust the fit of the measuring device to ensure accurate results. On the contrary, if the user does not respond to the operator or confirms an emergency situation, the operator may contact local rescue services and/or may through the communication means give instructions to the user till the arrival of rescue services.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     The present invention will hereinafter be described and explained in detail with reference to the enclosed drawings, where  
         [0019]      FIG. 1   a  shows by example a preferred embodiment and the general component setup of the monitoring device according to the invention, where the device is in the form of a cuff to attach to a user&#39;s arm or leg;  
         [0020]      FIG. 1   b  shows an alternative embodiment according to the invention with the monitoring device in the form of a chest strap;  
         [0021]      FIG. 2  shows by way of example an implementation of the device of the invention in two separate units;  
         [0022]      FIG. 3  illustrates the system of the invention comprising a monitoring device and a remote emergency center; and  
         [0023]      FIG. 4  shows in a flow chart the steps of the basic method of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]     The monitoring device according to the invention comprises means for position determination using a satellite based positioning system, means for measuring one or several physical parameters of a user, such as pulse, blood pressure and the like, means for processing measurement data, positioning data and any further data received by or stored in the monitoring device, and means for transmitting data and voice signals to a remote emergency center. Several extensions and enhancements may be added to the basic embodiment of the invention and will also be described in the following.  
         [0025]     As shown in  FIG. 1   a,  a user may wear the monitoring device  1  as a cuff on his arm, like a conventional blood pressure cuff. However, the device may as well be adapted for wearing on a leg or, in the form of a chest strap, around the chest of a user (shown in  FIG. 1   b ). Included in the measuring cuff may be an a on/off-switch  14  that is actuated when fitting the cuff to an extremity of the user and closing it, thereby activating the device; in the same way, the switch is actuated when taking the cuff or strap off and will then deactivate the device. This automatic actuation may be implemented by integrating the switch into the closing mechanism of the cuff. A rechargeable battery  12  is included in the device as a power supply for all components. In the cuff, one or more measuring means  4 ,  5  are included, which are capable of measuring physical parameters. These may be pulse, blood pressure or other parameters of medical interest.  
         [0026]     For positioning purposes, a positioning means  6  is included in the monitoring device. Conventional GPS receivers may be used as positioning means, but in general any suitable satellite based positioning system can be employed in such a device. The positioning means comprises a receiver to receive satellite signals and either processes those signals itself to determine a current position or forwards them to a processing means which will be described below.  
         [0027]     The monitoring device further includes a first processing means  8  such as a central processing unit (CPU), which is adapted to convert, process, store and/or forward data supplied by the positioning means and the measuring means  4 ,  5 . This may include, but is not limited to, the parameter values measured by the measuring means, such as the pulse or heart rate and blood pressure, the positioning data from the positioning system, and data received by the communication means or stored in the monitoring device. Since positioning data is typically given in longitude and latitude, conversion into a more comprehensible form is preferred, usually into a conventional address format obtained using a map or database within the processing means. As will be stated below, this format conversion and/or other tasks performed by the processing means  8  may additionally or optionally be taken on by an additional processing means located at the remote emergency center.  
         [0028]     Connected to the processing means is a communication means  10  to transmit the processed or forwarded data to a remote emergency center and to establish voice communication between the user and an operator. The communication means may in principle be a mobile phone using a mobile communication network such as a GSM or UMTS network. Generally, any mobile terminal or module may serve as said communication means, as long as it is capable of providing the following functionalities: radio transmission of measuring/positioning data, establishing voice communication to a corresponding terminal of an operator, and establishing voice communication to emergency services. Of course, at least a speaker and a microphone need to be included in the communication means to allow voice communication. While only these basic functions are essential for the monitoring device, the communication means may have further functionalities up to the point of a fully equipped mobile terminal for use in e.g. GSM or UMTS communication systems. As such, the monitoring device may also be integrated as a modification in such a mobile terminal or provided as an add-on module for a standard mobile phone, equipped with a suitable interface to connect to the mobile phone.  
         [0029]     With some medical conditions, it may be advisable to not only monitor pulse or heart rhythm but also blood pressure. Thus, in one preferred embodiment, said pulse measuring means  4  may be combined with means for blood pressure measurement. Means of this kind are well known in the art and usually include a cuff that is inflated with air to perform a blood pressure measurement. After both pulse and blood pressure having been determined, again this data is transmitted to a remote server together with positioning data and compared to reference values for pulse and blood pressure, respectively, either at the user device or at the remote server. On activation of the device, preferably a first measurement is initiated immediately. The pulse measurement may be effected by means of the same measuring component as is used for blood pressure measurement, just as in standard available blood pressure meters.  
         [0030]     An additional speaker may be comprised in the device to generate a loud alarm signal. The alarm signal may be stored somewhere in the device and may for instance be an alternating sound or some kind of voice calling for help. An alarm signal output may be triggered by the user himself, automatically by the processing means in response to a certain event, or on a command from the emergency center. The alarm signal or voice will attract the attention of people in the adjacency of the user who may be able to help. Optionally, instructions may be given through the speaker by an operator at the emergency center to people on site to e.g. initiate resuscitation. In an alternative embodiment of the invention, the mandatory speaker of the communication device may fulfil those task if the generated sound level is sufficient, such that an additional speaker is not required.  
         [0031]     To improve handling and operating of the monitoring device, additional displays, light emitting diodes (LEDs) and similar signalling means may be included in the device. Those may give indication of operating modes, system failures and more; by using LEDs of different colours, such as red, yellow and green LEDs, the operativeness of pulse/blood pressure meter, phone and positioning system may be indicated. A LCD display included in the device may show an operating state of the device, last measured pulse and/or blood pressure values with corresponding measuring time, last position with corresponding time, battery level, pulse signal, signal strength of the mobile communication unit, last data transmission time, and so on.  
         [0032]     Situations may arise in which any processes involving sound or noises are undesired, like in a theatre performance or other social events. With this in mind the monitoring device may in a preferred embodiment include an operating mode, further referenced as theatre mode, causing any non-silent processes to stop. To ensure constant and reliable monitoring of the user at that time, responses to certain events may be changed in relation to normal operating mode, which has been described in detail above. Theatre mode may be activated by pressing a muting button included in the device. In detail, switching to theatre mode may cause some or all of the following changes: 
        blood pressure measurements are turned off, unless they are feasible in complete silence;     voice contact in case of emergency level  1  is deactivated, instead a vibration alarm is activated. When abnormal conditions are detected by the monitoring device, the device or part of it starts to vibrate. If the user does not press a specified button, for example said muting button, within a predefined period of time, for instance within 20 seconds, this leads to emergency level  2  and thus to notification of rescue services. If in a preferred embodiment the device additionally comprises a speaker to call for help as set forth above, this speaker does not need to be muted, since the user&#39;s need for immediate help should have first priority over any disturbances caused by a loud alarm signal;     any illuminated parts of the device, such as LEDs or display backlights, are turned off or at least considerably reduced in intensity.        
 
         [0036]     However, the vibration alarm may also be utilized in “normal” operating mode in addition to contact over the phone. In case of two separate units the vibration alarm should preferably be included in the unit that is carried in direct contact with the user&#39;s body, which is usually the measuring cuff/strap.  
         [0037]     In a further preferred embodiment of the invention, the monitoring device may include a vibration sensor. On detection of a strong, sudden vibration or shock, as it might be caused by activation of an airbag in a car or by bursting glass panes, an accident distress signal similar to the regular distress signal will be transmitted, irrespective of other physical parameter values. This signal will be transmitted immediately, such that the emergency center may be informed of any accident before the device might break down due to severe damage. If then contact with the user cannot be established, a serious emergency can be assumed. The vibration sensor may be separate from the remaining of the device, and the user may attach it e.g. somewhere in a car, like on the dashboard or next to the airbag.  
         [0038]     An additional emergency button may be comprised in a preferred embodiment of the invention. This button will be incorporated in the cuff and may be actuated by a strong blow on the cuff performed by the user. This is especially useful when a user himself realizes an deterioration of his condition, such as sudden pain, nausea or dizziness. Actuation of said emergency button will immediately trigger emergency level  3 , which will lead to automatic notification of rescue services while specifying the current whereabouts of the user in form of an address obtained by analysing the last transmitted position data. After this notification or simultaneous to it an emergency center operator will attempt to establish contact with the user in order to check whether he is conscious and to eventually gather further information about his condition for passing the same on to rescue services. As before, the distress signal will be transmitted by a radio communication means of the monitoring device. Notification of rescue services may be carried out by the monitoring device itself, or the distress signal is transmitted to the emergency center and may there trigger an automatic emergency call. Any information stored at the server of said emergency center may be suitably converted, such as GPS positioning data to an address, and then forwarded to rescue services.  
         [0039]     There is also the option of an embodiment with no pulse monitoring, but only the shock sensitive emergency button as described in the preceding paragraph. This would be sufficient for someone who does not suffer from any cardiovascular disease, but some kind of medical condition which is not detectable by pulse monitoring, such as a condition with suddenly occurring faints.  
         [0040]     When travelling on an airplane, use of mobile phones and similar radio communication devices is generally prohibited. Thus an airplane operating mode may be implemented, which may be activated by a button. In airplane mode, the communication means and positioning means is deactivated, while the detection of abnormal parameter values (medical emergency) triggers the output of an alarm signal. Position determination would be possible in an airplane, but does not supply any valuable information, and since the airplane personnel is the only help available and rescue services do not need to be informed, positioning would not make sense in an airplane. As in normal mode, physical parameters such as pulse and/or blood pressure will be monitored and repeatedly compared in the processing means to maximum and minimum threshold values stored in the device. When values beyond these thresholds are detected, the user is notified of this by a vibration alarm as described above or by an audible signal through a speaker included in the device. The audible signal may be some kind of alarm sound or a voice message stored in the device. If the user does not identify the incident as a false alarm by pressing a defined button, loud alarm signals or voice instructions, again stored in a suitable way on the device, may attract the attention of other passengers and inform them about the emergency.  
         [0041]     Since all data about users may be automatically gathered and stored at the remote server, those data may be used for elaboration of medical prognoses and risk calculations. The server may include a computer program for data processing, which is capable of evaluating the trend in pulse and/or blood pressure data measured over a certain period of time and may then give suggestions to the user regarding his further actions, such as taking medication for blood dilution or calling on a hospital for further treatment.  
         [0042]     According to a preferred embodiment of the invention, wearing comfort of the device may be enhanced by implementing the measuring means  4 ,  5  for pulse and/or blood pressure and the remaining components of the monitoring device, such as communication means, processing means and positioning means, in two separate units  60  and  70 , as shown in  FIG. 2 . Only the measuring means needs to be placed directly on the user within a first unit  60 ; any other components may be located, for example, in a second unit  70  in a pocket of the user. The actual measuring unit may in this manner be considerably smaller when some components are enclosed in an extra unit. The two units  60  and  70  need to be interconnected for processing of the data gained from the measurement device; this connection may be wire-based or wireless. To this end, wire-based ( 50 ,  51 ) or wireless interfaces ( 52 ,  53 ) are included in both units.  
         [0043]     In  FIG. 3 , the complete system of the invention can be seen, comprising a monitoring device  1  as described above and a remote emergency center  2 . Data may be transmitted between those two via a communication means  10  of the device and a corresponding communication means  20  at the emergency center  2 . As stated above, these communication means  10  and  20  may be phones of conventional type, specifically a mobile phone in the monitoring device  1  and any kind of phone at the emergency center  2 . The only requirement is that these communication means or phones  10  and  20  are both capable of transmitting and receiving speech and data between each other and to make a call to local rescue services. It should be noted that the emergency center will in general be in charge of a multitude of users or rather their monitoring devices. Each monitoring device  1  will thus repeatedly be transmitting data to the emergency center  2 , where it is processed and stored.  
         [0044]     The positioning means  6  of the monitoring device  1  uses satellite based positioning, which operates on basis of a set of orbital satellites transmitting signals that are picked up by the positioning means and allow determination of its position by triangulation. Thus, the positioning means  6  searches for positioning satellites  25  when turned on and subsequently receives signals from several satellites. From the received signals it is able to determine the current position, giving longitude and latitude down to a precision of angular seconds. The processing tasks described for the first processing means  8  of the monitoring device  1  may alternatively be performed at a second processing means  22  (CPU II) located in the emergency center  2 . A server  24  is connected to the second processing means  22 , where all data received in transmissions may be stored. In addition, databases and programs may be stored at the server  24  which are necessary for operation of the monitoring devices  1 . These are, amongst others, threshold values for all users assigned to the emergency center in question, mapping data to gain addresses from the positioning data given as longitude and latitude, programs to evaluate stored user data and analyse medical risk factors and the like.  
         [0045]      FIG. 4  shows in a flow chart the basic method according to the invention by way of example. The process starts at step  102 , where an initial determination of a user&#39;s pulse and of his current position takes place, using said pulse measuring means ( 4 ) and said positioning means as described above. In step  104  then, it is checked by the processor means whether the measured pulse values are within predefined limits or thresholds stored at the monitoring device. If limits are kept, the position data and measured parameter values will be sent to the emergency center (step  106 ), where they will be received and stored at a server in step  202 . If however measured parameter values are below or above said predefined threshold range, this triggers emergency level  1  as described above. A distress signal will be generated by the processing means, and in step  108  this distress signal will be transmitted to the emergency center together with the current position data and the measured pulse values. Transmission of those data to the emergency center is preferably carried out by means of a radio communication link. To identify the user associated with the parameter values, each transmission additionally includes an identifier, which may include a device identification and/or a user identification (ID) to unambiguously associate any values and distress signals with a certain user. When the data has been received at the emergency center, pulse values and position data are again stored at said server, while the distress signal is indicated to an operator of the emergency center in an appropriate way, such as an audible or visible alarm signal (step  204 ). Thereupon, the operator will attempt to establish contact with the user via any communication device (step  206 ). If contact with the user cannot be established, it seems probable that he is unconscious and immediately needs help. The operator will first determine the last stored position of the user and then initiate the notification of local rescue services (step  210 ). He may provide useful information to them, such as the address where the user is located and his medical data measured by the device and/or stored at the server. If the operator is able to establish contact to the user, he may ask questions about his condition and, if the user feels comfortable (step  208 ), try to find reasons for the false alarm. A false alarm may be caused by faulty attachment of the measuring cuff, low battery power or similar reasons. However, if the user is able to speak to the operator and confirms an emergency situation, the operator shall again notify rescue services as represented by step  210  and may further give instructions to the user till the arrival of help.  
         [0046]     Step  106 , which is the transmitting of pulse and position data when threshold values are met, may optionally be left out in one modification of the method, such that transmission of the data to the emergency center is only effected in case of emergency.  
         [0047]     Upon activation of the device, the search for satellites is initiated. At the same time, possibly before contact with the positioning satellite has been established, a first pulse measurement is performed and the identifier, including a device identification and/or a user identification, is sent to the emergency center together with the measured pulse values (first transmission without position). After satellite contact has been established, a data signal is send via the mobile communication means to the emergency center, including identification numbers, position and measured pulse values (first transmission with position).  
         [0048]     Similarly, on deactivation of the device, a last transmission to the emergency center includes the most recent measured physical parameter value, the most recent determined position, the identifier as described above and a deactivation notification signal, i.e. a signal for notifying the emergency center or rather an operator that the device will now be deactivated by the user.  
         [0049]     As will be understood, various modifications of the features described in here can be made. For instance, switching between operating modes such as normal mode, airplane mode and theatre mode may be effected by different buttons or by pressing one single button a various number of times. Also, many of the embodiments described above can be combined with each other and enhanced in various ways. Though only one or two measuring means are mentioned and shown in most of the examples, additional measuring means for other physical parameters may as well be included in the device and may be operating in a similar way to those described. Further, all embodiments of the system and device of the invention may be included in one single unit, in a system of two separate units or in a module utilizable with a mobile terminal. The radio communication systems mentioned for transmitting data between monitoring device and the emergency center are given by way of example only, and it is obvious that any radio communication system which allows long-range contact would be adequate for this application.