Patent Publication Number: US-2023156444-A1

Title: Mobile communication terminal and control method therefor

Description:
CROSS-REFERENCE OF RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/098,422, filed Nov. 1, 2018, which is the U.S. National Phase under 35 U.S.C. § 371 of International Patent Application No. PCT/JP2016/066060, filed on May 31, 2016, the entire disclosure of which Application is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a technology for preventing loss or theft of a mobile communication terminal. 
     BACKGROUND ART 
     As technology for preventing the loss of mobile communication terminal, there is a technology disclosed in, for example, PTL1. The PTL1 discloses mobile communication terminal including near field communication means for performing near field communication with another mobile communication terminal; locking means for transitioning to a locked state in which authentication is requested from external operation when it is determined that a distance from another mobile communication terminal is equal to or more than a predetermined value based on a communication status with another mobile communication terminal by the near field communication means; receiving means for receiving, from another mobile communication terminal, authentication information for releasing the locked state upon confirming that the communication with another communication terminal is enabled; lock release means for releasing the locked state based on the authentication information received by the receiving means; and condition setting means for setting a permission condition for permitting at least one of the transition to the locked state by the locking means and the release of the locked state by the lock release means. 
     CITATION LIST 
     Patent Literature 
     PTL1: Japanese Patent Application Laid-Open No. 2014-170429 
     SUMMARY OF INVENTION 
     Technical Problem 
     In recent years, with the advancement of high performance and advanced functions of the mobile communication terminals, the mobile communication terminals have become widespread. Examples of the mobile communication terminals diversely include cellular phones typified key smartphones, smart watches which are wristwatch-type mobile communication terminals, eyeglasses head mounted display which is a wearable device, and so on. On the other hand, when the mobile communication terminal is lost or stolen, an influence of caused by the lost or theft such as loss of personal information is large, and a method of effectively preventing the loss and theft is required. PTL1 discloses a technique for preventing the loss and theft by cooperating with multiple mobile information terminals and locking the mobile information terminal by using information a distance between the terminals. 
     However, the method disclosed in PTL1 suffers from such a problem that the terminal is unnecessarily locked without understanding whether a cause of the distance to another terminal being equal to or more than the predetermined value resides in the loss or theft or a temporary event such as a user&#39;s leaving. Further, when near field communication with another terminal cannot be performed, information on another terminal cannot be acquired, which makes it difficult to accurately determine whether the terminal is to be locked, or not. 
     An object of the present invention is to precisely detect an abnormal state such as loss or theft of a mobile information terminal and avoid unnecessarily locking the terminal. 
     Solution to Problem 
     The above object is solved by the invention defined in the claims, for example. 
     Advantageous Effects of Invention 
     According to the present invention, the abnormal state such as the loss or theft of the mobile information terminal can be precisely detected, and the terminal can be prevented from being unnecessarily locked. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a block diagram showing a configuration of a mobile communication terminal according to Example 1. 
         FIG.  2    is a schematic diagram showing near field communication between a mobile communication terminal A and a mobile communication terminal B. 
         FIG.  3    is a diagram schematically illustrating a relationship between a communication distance and communication strength. 
         FIG.  4    is a flowchart showing an abnormality determination process of the mobile communication terminal. 
         FIG.  5    is a diagram showing criteria for determining necessity of locking in  FIG.  4   . 
         FIG.  6    is flowchart showing an abnormality determination process of the mobile communication terminal. 
         FIG.  7    is a diagram showing criteria for determining the necessity of locking in  FIG.  6   . 
         FIG.  8    is a flowchart showing an abnormality determination process of a mobile communication terminal according to Example 2. 
         FIG.  9    is a flowchart showing an abnormality determination process of a mobile communication terminal according to Example 3. 
         FIG.  10    is a flowchart showing an abnormality determination process of a mobile communication terminal according to Example 4. 
         FIG.  11    is a block diagram showing a configuration of a mobile communication terminal according to Example 5. 
         FIG.  12    is a flowchart showing an abnormality determination process of the mobile communication terminal. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Examples of the present invention will be described below with reference to the drawings. In each example, abnormality of a mobile communication terminal is determined by only a communication distance with a cooperating mobile communication terminal but also ode combination of position information on each mobile communication terminal or terminal information with the communication distance. 
     EXAMPLE 1 
     In Example 1, an abnormal state of a mobile communication terminal is determined with the use of position information on each mobile communication terminal. 
       FIG.  1    is a block diagram showing a configuration of a mobile communication terminal according to Example 1. This example shows a case of using two mobile communication terminals in cooperation in which a mobile communication terminal as an operation source is assumed to be a mobile communication terminal A ( 100 A) and a mobile communication terminal as a cooperation destination is assumed to be a mobile communication terminal B ( 100 B). An abnormal state (loss, theft, or the like) of the mobile communication terminal A as the operation source determined in cooperation with the mobile communication terminal B. The mobile communication terminal includes, for example, a smartphone, a smart watch, and the like, but a device is not limited as long as communication between the mobile terminals can be performed, and wearable devices such as a head mount display an activity meter are also applicable. Hereinafter, the mobile communication terminal A as the operation source is referred to simply as “terminal A”, and the mobile communication terminal B as the cooperation destination is referred to simply as “terminal B.” Since the terminal A and the terminal B cooperate with each other, it is assumed that the initial settings such as an authentication process and a pairing process are performed on each other. 
     The mobile communication terminal A includes near field communication unit  101 A, an information acquisition unit  102 A, an abnormality determination unit  103 A, and a lock unit  104 A. Usually, the mobile communication terminal includes many other components. In this example, only components related to the abnormality determination function will be taken up and described. The mobile communication terminal B has the same configuration as the mobile communication terminal A, and the respective components corresponding to is the terminal A are denoted by reference symbols  101 B to  104 B. As a result, the mobile communication terminal B also has the same abnormality determination function as that of the mobile communication terminal A. However, when the abnormality determination operation or lock operation not performed in the mobile communication terminal B, the abnormality determination unit  103 B or the lock unit  104 E is not indispensable. 
     The near field communication unit  101 A performs near field communication  110  with the short-range communication unit  101 B of the terminal B and obtains a communication distance or communication strength to the terminal B. The near field communication system includes, for example, Bluetooth Trademark (registered trademark) and Wi-Fi (registered trademark), but there is no particular limitation of the near field communication system as long as the system can directly communicate with the terminal B. 
     When the communication distance obtained by the near field communication unit  101 A is equal to or more than a threshold value or when the communication strength is equal to less than a threshold value, the information acquisition unit  102 A acquires information necessary for abnormality determination from the terminal A, the terminal B, or both of those terminals and B. In this example, e information acquisition unit  102 A acquires position information on both of the terminal A and the terminal B. 
     The abnormality determination unit  103 A determines whether the terminal A is in the abnormal state (lost or stolen state), or not, based on the information (the position information on the terminal A and the terminal B) acquired by the information acquisition unit  102  A. If it is determined that the terminal A is abnormal, the abnormality determination unit  103 A transmits a command to lock terminal A to the lock unit  104 A. 
     The lock unit  104 A locks the terminal A according to the lock command from the abnormality determination unit  103 A. A locking method includes a method of requesting authentication at the start of operation of the mobile communication terminal, but there is no particular limitation on the method. 
       FIG.  2    is a schematic diagram showing near field communication between the mobile communication terminal A and the mobile communication terminal B. In the figure, the near field communication  110  is performed between the terminal  100 A such as a smartphone and the terminal  100 B such as a smart watch, by using, for example, Bluetooth (registered trademark.). If both of the terminals  100 A and  100 B are carried with the same user, a communication distance X between the terminals is usually close to each other. If the terminal  100 A is lost away from the user, the communication distance X between the terminals becomes larger. 
       FIG.  3    is a diagram schematically describing a relationship between the communication distance and the communication strength. When there is nothing interfering with communication between the mobile communication terminal A and the mobile communication terminal the communication distance X and the communication strength A have a simple inverse proportional relationship. If a relational expression of the above relationship is obtained in advance, the current communication distance X can be calculated according to the communication strength A in the near field communication unit  101 A. 
     In this example, the abnormality determination of the terminal is performed in two stages. In a first stage, it is determined whether or not the communication distance X between the terminals separated by a predetermined distance Xth (threshold) or more. The threshold value Xth should be set according to a usage situation of the terminal, but if the terminal is used in the home or workplace, the threshold value Xth is set to 10 to several tens of meters, for example. Meanwhile, instead of the threshold value Xth of the communication distance, it may be determined whether or not the current communication strength A has fallen below communication strength Ath (threshold value) corresponding to Xth. However, if only the determination in the first stage is insufficient to know whether a cause of the communication distance X exceeding the threshold value Xth is caused by the abnormal state of the terminal or a temporary event such as the user&#39;s leaving. 
     Therefore, in a second stage, position information (movement state) on the terminal A and the terminal B is acquired to determine whether the terminal is in the abnormal state, or not. In order to enable the terminal A to acquire the position information from the terminal B, the threshold value Xth of the communication distance is set to be smaller than a maximum communicable distance Xmax of the near field communication. This is because when the threshold value Xth is set to be equal to Xmax, the near field communication between the terminals cannot be performed when the communication distance exceeds the threshold value Xth, and the terminal A cannot acquire the position information from the terminal B. A method of determining the abnormality of the terminal according to the first and second stages will be described below. 
       FIG.  4    is a flowchart showing an abnormality determination process of the mobile communication terminal. In other words, the terminal A cooperates with the terminal B to determine whether the host terminal A (terminal A) is in the abnormal state, or not. 
     In S 300 , the near field communication unit  101 A of the terminal A communicates with the terminal B and acquires the communication distance X between both of those terminals. 
     In S 301 , the information acquisition unit  102 A determines whether the communication distance X received from the near field communication unit  101 A is equal to or larger than the threshold value Xth, or not (first stage). As a result of the determination, if the communication distance X is equal to or larger than the threshold value Xth, the process proceeds to S  302 . If the communication distance X is smaller than the threshold value Xth, the determination process is terminated. 
     In S 302 , the information acquisition unit  102 A acquires the position information on both of the terminal A and the terminal B. In this example, the method of acquiring the position information may be, for example, a method of tracking the position of the terminal such as a GPS (Global Positioning System), or a method of determining whether the terminal is moving, or not, with the use of an acceleration sensor of the terminal. The position information on the terminal B is acquired by communicating with the terminal B through the near field communication unit  101 A. 
     In S 303 , the abnormality determination unit  103 A determines whether both of the positions of the terminal A and the terminal B are moving, or not, based on the information acquired by the information acquisition unit  102 A (second stage). If the positions of both the terminals are moving, abnormality determination unit  103 A determines that an abnormal condition such as loss or theft occurs, and the process proceeds to S 304 . If the positions of both the terminals are not moving, the determination process is terminated. 
     In S 304 , the abnormality determination unit  103 A transmits a command to the lock unit  104 A, and the lock unit  104 A locks the terminal A. For example, the lock unit  104 A sets the terminal A in a locked state requesting authentication from the external operation. The lock unit  104 A may lock not only the terminal A but also the terminal B. 
     The series of processes S 300  to S 304  described above are periodically repeatedly executed. 
       FIG.  5    is a diagram showing a criterion for determining the necessity of locking in S 303  of  FIG.  4   . In this example, the necessity of locking is determined according to the moving state of both those terminals, and when both of those terminals are moving, it is determined that there is a need for locking. The reason will be described below. 
     When one user possesses multiple mobile communication terminals, the user usually uses all the terminals while wearing those terminals or placing those terminals around. If the user puts one terminal A at a certain place and moves to another place while wearing the terminal B, the communication distance between the terminal A and the terminal B may be equal to or more than a threshold value. In that case, the terminal B is moving together with the user and the terminal A is stationary. Hence, in a normal state, it is difficult for both of the terminals to be in a moving state. 
     On the other hand, in a situation where the user leaves the terminal A in a transportation (vehicle interior or the like) or in a situation where the terminal A is stolen, the terminal A is often moving. Hence, when the communication distance between the terminal A and the terminal B is equal to of more than the threshold value, and both of those terminals are moving, it is determined that the terminal is in the abnormal state such as loss or theft. As described above, with the use of the distance information and the moving state information on the multiple terminals in combination, it is possible to accurately determine and prevent the abnormal state of the mobile communication terminal. 
     Further, in the abnormality determination, a determination with higher accuracy can be performed by adding the position information on where the mobile communication terminal is located. 
       FIG.  6    is a flowchart showing the abnormality determination process of the mobile communication terminal.  FIG.  6    shows a process in which S 311  to S 413  are added to or changed from the flowchart of  FIG.  4   . 
     In S 311 , it is determined whether the terminals A and B are located indoors, or not, based on the position information acquired in S 302 . For example, the determination can be performed based on GPS information. If the terminals A and B are placed indoors, the process proceeds to S 312 , and if the terminals A and B are placed outdoors, the process proceeds to S 313 . 
     In S 312 , as in S 303  of  FIG.  4   , it is determined whether the positions of the terminal A and the terminal B are both moving, or not. If both of those terminals are moving, it is determined that the abnormal state has occurred, and the process proceeds to S 304  in which the terminal A is locked. 
     In S 313 , it is determined whether one of the positions of the terminal A and the terminal B is moving, or not. When one of them is moving, it is determined that the abnormal state has occurred, and the process proceeds to S 304  to lock the terminal A. 
       FIG.  7    is a diagram showing criteria for determining the necessity of locking in S 311  to S 313  of  FIG.  6   . The criterion of the necessity of locking is changed depending on whether the positions of the terminals A and B are indoor or outdoor. In the case where the terminal is outdoors, since the risk of loss or theft is increased, it is determined that there is a necessity of locking if at least any terminal is moving. According to the method of  FIGS.  6  and  7   , the strength of security is changed according to the position situation of the terminal, thereby being capable of performing the abnormality determination with higher accuracy. 
     Incidentally, as a method for releasing the lock of the mobile communication terminal A locked in this example, there are a password input to an approval screen, fingerprint authentication by the user, and so on. However, once the lock is released, the lost theft prevention function according to this example may be stopped until the near field communication with the communication terminal B is again performed. As a result, in the case of a simple misplacement, the subsequent unnecessary lock can be prevented by causing the user to release the lock. As another lock releasing method, when the locked terminal A is moved and the near field communication with the original terminal B is enabled again, the lock may be released at that time point. As a result, even if the terminal A is locked at an unintended timing, the lock can be automatically released, thereby improving the convenience. 
     In this example, the mobile communication terminal as the operation source is defined as the terminal A, the mobile communication terminal as the cooperation destination is defined as the terminal B, and the abnormal state of the terminal A is determined. Alternatively, a relationship between the terminals A and B may be reversed. In other words, the method of this example may be applied to the determination of the abnormal state of the cooperation destination terminal B. Further, the method of this example may be applied to the determination of the abnormal states of both the operation source terminal and the cooperation destination terminal. 
     In relation to the above configuration, in S 304  of  FIG.  4  or  6   , the lock command of the terminal A is transmitted to the terminal B through the near field communication unit  101 A, thereby being capable of locking the terminal B by the lock unit  104 B. Alternatively, both of the terminal A and the terminal B can be locked by the lock units  104 A and  104 B. This makes it possible to reliably lock the mobile communication terminal and improve the strength of security even if one of the terminal A and the terminal B is lost (or stolen). The same is applied to the respective examples to be described later. 
     Although processing between two mobile communication terminals has been described in this example, any number may be used as long as the number of mobile communication terminals is two or more. In that case, the operation described in this example may be performed on all of mobile communication terminals that are in the near field communication. 
     According to Example 1, with the use of the position information and the moving state information on the multiple terminals, it is possible to accurately detect and prevent the abnormal state of the mobile communication terminal. 
     Hereinafter, other methods for determining the abnormal state of the mobile communication terminal will be described in several examples. 
     EXAMPLE 2 
     In Example 2, an abnormality is determined with the use of wearing information on whether a cooperating mobile communication terminal B is being worn by a user. If a single user possesses multiple terminals A and B, a communication distance between the terminals A and B is equal to or more than a threshold value, and the terminal B is worn by the user, it is clear that the terminal A has moved to a position distant from the user, and the possibility of the loss or theft of the terminal A is increased. Therefore, such a situation is determined to be an abnormal state. 
       FIG.  8    is flowchart showing an abnormality determination process of the mobile communication terminal according to Example 2. A difference from Example 1 ( FIG.  4   ) resides in that for purpose of abnormality determination, wearing information on whether or not the cooperating mobile communication terminal B is being worn by the user. Hereinafter, a description duplicated with that of  FIG.  4    will be simplified. 
     In S 400 , a communication distance X between the terminals A and B is acquired. In S 401 , it is determined whether the communication distance X is equal to or more than the threshold Xth, or not. As a result of the determination, if the communication distance X is equal to or more than the threshold Xth, the process proceeds to S 402 . 
     In S 402 , an information acquisition unit  102 A acquires the wearing information from the terminal B. As information for determining whether the terminal B is being worn, or not, information on whether the terminal is operated, or not, may be used. For example, the mobile communication terminal is of a wearing type such as a wristwatch type, it can also be determined whether the terminal is being worn by acquiring physical information, or not. 
     In S 403 , the abnormality determination unit  103 A determines whether the terminal B is being worn, or not, based on the wearing information acquired by the information acquisition unit  102 A. In the case where the terminal B is being worn, the abnormal state occurs in the terminal A, and the process proceeds to S 404 . In S 404 , the abnormality determination unit  103 A transmits a command to the lock unit  104 A, and the lock unit  104 A locks the terminal A. 
     According to Example 2, the abnormal state of the terminal A can be detected with accuracy with the use of the wearing information on the cooperating mobile communication terminal B. Incidentally, when the terminal B is a device of: the wearing type (wearable device), it may be checked whether a wearer matches the user, or not, according to the wearing information. This makes it possible to determine that the terminal B is stolen and worn by other than the user, and to perform theft prevent with more accuracy. 
     EXAMPLE 3 
     In Example 3, an abnormality state of a terminal A is determined with the use of charging information on whether a mobile communication terminal A is being charged, or not. If multiple terminals A and B are possessed by a single user, the terminal A cannot be moved while being charged and may be distant from the terminal B. In that case, the user moves the terminal B while intentionally leaving the terminal A, and the possibility of loss or theft is low, and the terminals A and B are excluded from abnormality determination. 
       FIG.  9    is a flowchart showing an abnormality determination process of the mobile communication terminal according to Example 3. This example is different from Example 1 ( FIG.  4   ) in that for the purpose of the abnormality determination, the charging information on whether the mobile communication terminal A is being charged, or not, is used. Hereinafter, a description duplicated with that of  FIG.  4    will be simplified. 
     In S 500 , a communication distance X between the terminals A and B is acquired. It is determined in S 501  whether or not the communication distance X is equal to or more than the threshold Xth. As a result of the determination, if the communication distance X is equal to or more than the threshold Xth, the process proceeds to Step S 502 . 
     In S 502 , the information acquisition unit  102 A acquires the charging information on the terminal A. In other words, the information acquisition unit  102 A acquires information on whether a charger is connected to the terminal A, or not, or acquires information on whether charging is in progress, or not, from the power management unit. 
     In S 503 , the abnormality determination unit  103 A determines whether the terminal A is being charged, or not, based on the charging information acquired by the information acquisition unit  102 A. If the terminal A is being charged, it is determined that the terminal A is not the abnormal state such as loss or theft, and the process is terminated. If the terminal A is not being charged, the process proceeds to S 504 . In S 504 , the abnormality determination unit  103 A transmits a command to the lock unit  104 A, and the lock unit  104 A locks the terminal A. 
     According to Example 3, since the mobile information terminal A is being charged, the mobile information terminal A is not locked, unnecessary locking operation can be avoided and usability can be improved. 
     EXAMPLE 4 
     In Example 4, abnormality is determined with the use of battery level information held by a mobile communication terminal A. Usually, the mobile communication terminal is charged by a user so that a battery level does not become zero, but the lost mobile communication terminal is not charged and the battery level can be equal to or less than the threshold value, for example, 0. Also, if the battery level is insufficient, the near field communication disconnected and distance information cannot be acquired. Therefore, such a situation is determined as an abnormal state. 
       FIG.  10    is a flowchart showing an abnormality determination process of the mobile communication terminal according to Example 4. A difference from Example 1 ( FIG.  4   ) resides in that for the purpose of determining abnormality, the battery level held by the mobile communication terminal A is leveraged. A description duplicated with that in  FIG.  4    will be simplified below. 
     In S 600 , a communication distance X between the terminals A and B is acquired. In S 601 , it is determined whether or not the communication distance X is equal to or more than a threshold value Xth. As a result of the determination, when the communication distance X is equal to or more than the threshold Xth, or when the communication distance X cannot be acquired by the near field communication, the process proceeds to S 602 . 
     In S 602 , the information acquisition unit  102 A acquires battery level information from the terminal A. The battery level information can be acquired from the power management unit. 
     In S 603 , the abnormality determination unit  103 A determines whether or not the battery level is equal to or less than the threshold value, based on the battery level information acquired by the information acquisition unit  102 A. If the battery level is equal to or less than the threshold value, the abnormality determination unit  103 A detects the abnormal state such as loss or theft has occurred, and the process proceeds to S 604 . When the battery level is not equal to or less than the threshold value, the process returns to S 600  and the abnormality determination unit  103 A determines the communication distance again. 
     In S 604 , the abnormality determination unit  103 A sends a command to the lock unit  104 A, and the lock unit  104 A locks the terminal A. 
     According to Example 4, the lock unit  104 A locks the mobile communication terminal A when the battery level of the mobile communication terminal A becomes equal to or less than the threshold value, thereby being capable of detecting the abnormal state with high accuracy. 
     EXAMPLE 5 
     In Example 5, a mobile communication terminal A has a telecommunication function, switches between near field communication and telecommunication according to a communication status with a mobile communication terminal B, accurately acquires position information and terminal information on the terminal B, and determines an abnormal state such as loss or theft with high precision. In this example, the near field communication enables a direct communication between the terminals as described in Example 1 whereas the telecommunication enables communication with the terminal B with the use of the Internet by connecting the terminal B to the Internet using a 3G line, an LTE (Long Term Evolution) or the like. In Example 1, Wi-Fi is defined as the near field communication, but Wi-Fi may be treated as the telecommunication as far as the terminal B can be connected to the Internet. 
       FIG.  11    is a block diagram showing a configuration of the mobile communication terminal according to Example 5. The mobile communication terminal A ( 200 A) as an operation source adds a telecommunication unit  202 , a communication mode switching unit  203 , and switches  207  and  208  to the configuration of the mobile communication terminal A ( 100 A) in Example 1 ( FIG.  1   ). The other components  201 ,  204 ,  205 , and  206  correspond to the respective components in  FIG.  1   . Meanwhile, the mobile communication terminal B ( 200 B) also has the same configuration as that of the mobile communication terminal A ( 200 A). 
     When the terminal A performs the near field communication with the terminal B, the communication mode switching unit  203  connects the switches  207  and  208  to the near field communication unit  201  side, and when the terminal A performs the telecommunication, the communication mode switching unit  203  switches the switches  207  and  208  to the telecommunication unit  202  side. In the telecommunication, the terminal A communicates with the terminal B through the Internet line  210 . 
       FIG.  12    is a flowchart showing an abnormality determination process of the mobile communication terminal. 
     In S 700 , the communication mode switching unit  203  connects switches  207  and  208  to the near field communication unit  201  side and starts communication with the terminal B by the near field communication unit  201 . 
     In S 701 , the communication mode switching unit  203  receives communication distance information with the terminal B from the near field communication unit  201  and determines whether the near field communication can be performed, not. If the near field communication is enabled, the process proceeds to S 702 , and the communication mode switching unit  203  determines whether or not the communication distance X is equal to or more than a threshold value Xth. As a result of the determination, if the communication distance X is equal to more than the threshold value Xth, the process proceeds to S 705  and the communication mode switching unit  203  acquires information from the terminal B by the near field communication. Next, in S 706 , the communication mode switching unit  203  acquires information from the terminal A. If the communication distance X is less than the threshold value Xth, the process is terminated. 
     When it is determined in S 701  that the near field communication is disabled, the process proceeds to S 703 . 
     In S 703 , the communication mode switching unit  203  connects the switches  207  and  208  to the telecommunication unit  202  side and switches to the telecommunication mode. As a result, the terminal A is connected to the Internet line  210  by the telecommunication unit  202 . In S 704 , the communication mode switching unit  203  determines whether telecommunication is enabled, or not. If the telecommunication is enabled, the process proceeds to S 705 , and the communication mode switching unit  203  acquires information from the terminal B through the Internet line  210 . Subsequently, in S 706 , the communication mode switching unit  203  acquires information from the terminal A. If the telecommunication is disabled in S 704 , the process proceeds to S 706 . 
     In S 705 , the information acquisition unit  204  acquires information from the terminal B by the near field communication unit  201  or the telecommunication unit  202 . At that time, the information acquired from the terminal B includes position information and wearing information on the terminal B, and so on as described in Example 1 and Example 2. 
     In S 706 , the information acquisition unit  204  acquires information from the terminal A. The information acquired from the terminal A includes the position information, the charging information, the battery level information on the terminal A, and so on as described in Example 1, Example, 3, and Example 4. 
     In S 707 , the abnormality determination unit  205  determines whether the terminal A is in an abnormal state, or not, according to the information of the terminal B and/or the terminal acquired by the information acquisition unit  204 . The determination criteria at that time are any determination criteria in Example 1 to Example 4. Alternatively, the respective determination criteria may be appropriately combined together, and it may be determined that the terminal A is in the abnormal state when an abnormality occurs in one of the determination criteria. 
     If the abnormality determination unit  205  determines that the terminal A is in the abnormal state, the process proceeds to S 708 , the abnormality determination unit  205  transmits a command for locking the terminal A to the lock unit  206 , and the lock unit  206  locks the terminal A. 
     The series of processes S 700  to S 708  described above are executed repeatedly at predetermined time intervals. 
     In the above Examples 1 to 4, when the near field communication is disabled, information on the terminal B cannot be acquired, and the abnormal state must be determined with the use of only the information on the terminal A per se. On the other hand, according to Example 5, even when the near field communication is disabled, the information on the terminal B can be acquired by switching the communication mode to telecommunication, and the abnormal state can be determined with high accuracy. If a timing at which to switch from the near field communication to the telecommunication is set to not a timing at which the near field communication becomes disabled but a timing at which the communication distance in the near field communication becomes the threshold value or more, switching from the near field communication to the telecommunication is enabled without disconnecting the communication, and the reliability can be further improved. 
     Although the method of switching between the near field communication and the telecommunication has been described in this example, both communication modes of the near field communication and the telecommunication may be used at the same time. As a result, time and labor for switching the communication mode to the other are not required, the communication mode with higher communication strength can be continuously used, and the accuracy of abnormality determination is improved. 
     The present invention is not limited to the examples described above, but includes various modifications. For example, in order to easily understand the present invention, the above examples have been described in detail, and the present invention is not always limited to the provision of all the configurations described above. Also, a part of a configuration of one example can be replaced with another configuration, and the configuration of one example can be added with the configuration of another example. Also, in a part of the respective configuration examples, another configuration can be added, deleted, or replaced. 
     In addition, each of the above-described configurations, functions, processing units, processing means and the like may be realized in hardware by designing some or all of those components by, for example, an integrated circuit. Furthermore, the above-described configurations, functions and so on may be realized by software by interpreting and executing a program that realizes the respective functions by a processor. Information on programs, tables, files, and the like realizing each function may be stored in a memory, a recording device such as a hard disk, an SSD (Solid State Drive), or a recording medium, or a recording medium such as an IC card, an SD card, or a DVD. 
     Also, the control lines and the information lines necessary for description are illustrated, and all of the control lines and the information lines necessary for products are not illustrated. In fact, it may be conceivable that most of the configurations are connected to each other. 
     REFERENCE SIGNS LIST 
       100 A . . . mobile communication terminal A,  100 B . . . mobile communication terminal B,  101  . . . near field communication unit,  102  . . . information acquisition unit,  103  . . . abnormality determination unit,  104  . . . lock unit,  200 A . . . mobile communication terminal A,  200 B . . . mobile communication terminal B,  201  . . . near field communication unit,  202  . . . telecommunication unit,  203  . . . communication mode switching unit,  204  . . . information acquisition unit,  205  . . . abnormality determination unit,  206  . . . lock unit,  207 ,  208  . . . switch,  210  . . . Internet line.