Drowning alert system

Abstract

To provide a drowning alert system capable of further accurately determining whether or not a user is in a state where there is a risk of drowning and further effectively preventing the user from drowning.SOLUTION: A drowning alert system 1 includes: a mobile terminal 10 with a wireless communication unit 11 functioning as a wireless transmission unit that continuously transmits wireless signals; and a management device 20 having a wireless communication unit 21 functioning as a wireless receiving unit that receives the wireless signals and an alert unit 23 that issues alert. The alert unit 23 issues an alert if the duration for which the wireless communication unit 21 cannot receive the wireless signals exceeds a predetermined threshold value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a drowning alert system for use in swimming pools, bathrooms, etc. [Background technology]

[0002] Conventionally, a pool lifeguard support system has been known that detects near-drowning by taking advantage of the fact that the strength of radio waves emitted from an active IC tag sealed in a wristband worn by a swimmer is different when emitted from underwater and when emitted from the air (see Patent Document 1).

[0003] According to the pool lifeguard support system described in Patent Document 1, whether a swimmer is underwater in the pool is determined by the radio wave strength emitted from an IC tag, and if a swimmer remains in the same zone under the pool water for a certain period of time, it is assumed that there is a possibility that the swimmer is drowning. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-126735 A Summary of the Invention [Problem to be solved by the invention]

[0005] According to the pool lifeguard support system described in Patent Document 1, whether a swimmer is underwater in the pool is determined based on the radio wave strength emitted from the IC tag. However, since radio wave strength is prone to change due to various factors such as the distance between the monitoring device and the IC tag and the presence of obstacles, it is difficult to make an accurate determination.

[0006] An object of the present invention is to provide a drowning alert system that can more accurately determine whether a user is in a state where he or she is at risk of drowning and more effectively prevent the user from drowning. [Means for solving the problem]

[0007] In order to achieve the above object, one aspect of the present invention provides the following drowning alert system.

[0008] [1] A drowning alert system comprising: a mobile terminal having a wireless transmitting unit that continuously transmits a wireless signal; a wireless receiving unit that receives the wireless signal; and a management device having an alert unit that issues an alert, wherein the alert unit issues an alarm when the time during which the wireless receiving unit is unable to receive the wireless signal exceeds a predetermined threshold. [2] The drowning alert system described in [1] above, wherein the mobile terminal is equipped with a water detection sensor, and when the water detection sensor detects water, the wireless signal contains water detection information indicating that the water detection sensor has detected water, and when the time during which the wireless receiving unit is unable to receive the wireless signal exceeds the threshold value and the wireless signal received immediately before contains the water detection information, the alert unit issues the alarm. [3] A drowning alert system as described in [2] above, wherein the baud rate of the wireless signal including the water detection information is higher than the baud rate of the wireless signal not including the water detection information. [4] The drowning alert system described in any one of [1] to [3] above, wherein the portable terminal further includes a water depth sensor, and when the water depth value detected by the water depth sensor is greater than a predetermined threshold value, the wireless transmission unit stops transmitting the wireless signal. [5] A drowning alert system as described in [2] or [3] above, wherein when the management device continuously receives the wireless signal including the water detection information, the water detection sensor corrects the water detection judgment conditions. [6] A drowning alert system described in any one of [1] to [3] above, wherein the management device has a function as a power supply device for microwave wireless power supply, and the mobile terminal has a function as a power receiving device for microwave wireless power supply. Effect of the Invention

[0009] According to the present invention, a drowning alert system can be provided that can more accurately determine whether a user is in a state where he or she is at risk of drowning, and more effectively prevent the user from drowning. [Brief description of the drawings]

[0010] [Figure 1] 1(a) and (b) are schematic diagrams showing the configuration of a drowning alert system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing an example of the functional configuration of a mobile terminal and a management device that constitute a drowning alert system according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a schematic diagram showing an example of the configuration of a mobile terminal that is worn on the wrist of a user. [Figure 4] FIG. 4 is a flowchart showing an example of a process flow of the management device according to the embodiment of the present invention. [Diagram 5] FIG. 5 is a flowchart showing an example of a process flow of the mobile terminal according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (Configuration of drowning alert system) 1(a) and (b) are schematic diagrams showing the configuration of a drowning alert system 1 according to an embodiment of the present invention.

[0012] The drowning alert system 1 is a system for preventing drowning accidents in places where a user may drown, such as in a swimming pool or a bathtub, and includes a mobile terminal 10 that transmits a wireless signal, and a management device 20 that receives the wireless signal transmitted from the mobile terminal 10 and issues an alert (alarm) if it is determined that the user wearing the mobile terminal 10 is in a state where he or she is at risk of drowning.

[0013] The drowning alert system 1 uses interruption of wireless communication between the mobile terminal 10 and the management device 20 when the mobile terminal 10 is underwater to determine the risk of drowning.

[0014] When the mobile terminal 10 is located within a communication range with the management device 20, as shown in FIG. 1(a), if the mobile terminal 10 worn on the user's arm 50 or the like is above the water surface 51, normal communication is performed between the mobile terminal 10 and the management device 20.

[0015] On the other hand, as shown in FIG. 1(b), when the mobile terminal 10 is below the water surface 51, that is, underwater, the communication quality between the mobile terminal 10 and the management device 20 decreases and communication is easily interrupted.

[0016] A specific method for determining the risk of drowning will be described later. The mobile terminal 10 is typically a terminal worn on the arm 50 of the user as shown in Figures 1(a) and (b), but may be a terminal worn on another position such as the head.

[0017] Since the management device 20 can be installed and used outside the water of a pool or bathtub, the alert from the management device 20 makes it easier for outsiders to notice the condition of the user wearing the mobile terminal 10. Also, since the management device 20 has an alert function, the mobile terminal 10 does not need to have a component for the alert function, and can be made smaller than one with an alert function.

[0018] The management device 20 is not limited to a dedicated device, and for example, a smartphone may be used as the management device 20. In this case, for example, wireless communication is performed according to the Bluetooth (registered trademark) standard in the 2.4 GHz band, and an application for functioning as the management device 20 can be installed on the smartphone and used.

[0019] In the drowning alert system 1, multiple mobile terminals 10 can be managed remotely and collectively, thereby reducing management costs. Also, in the drowning alert system 1, the management device 20 can remotely detect when a user wearing a mobile terminal 10 is underwater, thereby effectively preventing drowning accidents in swimming pools and bathtubs by users, particularly elderly people and children.

[0020] FIG. 2 is a block diagram showing an example of the functional configuration of the mobile terminal 10 and the management device 20 that constitute the drowning alert system 1.

[0021] As shown in FIG. 2, the mobile terminal 10 includes, for example, a wireless communication unit 11, an antenna 12, a water detection sensor 13, an attachment detection sensor 14, a battery 15, an operation switch 16, and a control unit 17.

[0022] The wireless communication unit 11 functions as a wireless transmission unit that continuously (typically at regular intervals) transmits wireless signals via the antenna 12. The wireless communication unit 11 is configured, for example, with an RFIC (radio frequency integrated circuit). The frequency bands used for wireless communication are, for example, the 900 MHz band, the 2.4 GHz band, and the 5 GHz band. Wireless communication based on the UWB standard may also be used.

[0023] The water detection sensor 13 can be used to determine whether the mobile terminal 10 is underwater. The water detection sensor 13 is, for example, a capacitance type water detection sensor, a line sensor, a touch sensor, or a floating body sensor that is turned on by buoyancy when submerged in water.

[0024] The water detection sensor 13 may also function as a water depth sensor. In addition to the water detection sensor 13, the mobile terminal 10 may also include a water depth sensor.

[0025] The wearing detection sensor 14 can detect that the mobile terminal 10 is worn by a user (worn on the human body). The wearing detection sensor 14 is, for example, an infrared sensor or a visible light sensor.

[0026] Battery 15 stores power for operating mobile terminal 10. Operation switch 16 is used by the user of mobile terminal 10 to cause mobile terminal 10 to perform a predetermined operation.

[0027] The control unit 17 controls each unit of the mobile terminal 10. The control unit 17 is realized, for example, by a hardware processor such as a CPU (Central Processing Unit) executing a program (software). In addition, some or all of these components may be realized by hardware (including circuitry) such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a GPU (Graphics Processing Unit), or may be realized by a combination of software and hardware. The program may be stored in advance in a storage device that utilizes a non-transitory storage medium such as a flash memory provided in the mobile terminal 10.

[0028] As shown in FIG. 2, the management device 20 includes, for example, a wireless communication unit 21, an antenna 22, an alert unit 23, a storage unit 24, a power conversion unit 25, an operation switch 26, and a control unit 27.

[0029] The wireless communication unit 21 functions as a wireless receiving unit that receives a wireless signal transmitted by the mobile terminal 10 via the antenna 22. The wireless communication unit 21 is configured by, for example, an RFIC (Radio Frequency Integrated Circuit).

[0030] The alert unit 23 issues an alert (warning) when it is determined that the user wearing the mobile terminal 10 is in a state where there is a risk of drowning. The alert unit 23 is, for example, a speaker that emits sound or voice, a light-emitting device that emits light, a display that displays images, or a combination of two or more of these.

[0031] The storage unit 24 is a non-transitory storage medium such as a hard disk drive (HDD), a flash memory, or an EEPROM.

[0032] The power conversion unit 25 converts power supplied from an external source for use in the management device 20. The power conversion unit 25 is, for example, an AC / DC converter or a DC / DC converter. The management device 20 may include a battery and use the power stored in the battery as the power source.

[0033] The operation switch 26 is used by a user of the management device 20 to cause the management device 20 to perform a predetermined operation.

[0034] The control unit 27 controls each unit of the management device 20. The control unit 27 is realized, for example, by a hardware processor such as a CPU executing a program (software). Furthermore, some or all of these components may be realized by hardware (including a circuit unit) such as an LSI, ASIC, FPGA, or GPU, or may be realized by a combination of software and hardware. The program may be stored in advance in a storage device such as the storage unit 24.

[0035] The drowning alert system 1 includes multiple management devices 20, which may communicate bidirectionally directly or indirectly via a repeater to share the location of the mobile terminal 10 and determine whether the mobile terminal 10 is within each of the detection ranges (determine which management device 20 the mobile terminal 10 is within its detection range). In this case, for example, if a wireless signal that one management device 20 (assumed to be management device A) has been receiving is no longer received, and then another management device 20 (assumed to be management device B) begins to receive the wireless signal, it is possible to know with certainty that the user has left management device A.

[0036] The drowning alert system 1 may have a wireless power supply function using microwaves. When the drowning alert system 1 has a wireless power supply function, it is possible to prevent the system from failing to function due to the portable terminal 10 running out of charge during use.

[0037] In this case, the management device 20 and the mobile terminal 10 function as a power supply device and a power receiving device for microwave wireless power supply, respectively, and transmit and receive microwaves for contactless power supply between the antenna 22 of the management device 20 and the antenna 12 of the mobile terminal 10. The mobile terminal 10 can receive the microwaves transmitted from the management device 20 and charge the battery 15.

[0038] In this case, for example, the wireless communication unit 21 of the management device 20 has a function of converting power into microwaves and transmitting them via the antenna 12 when microwave wireless power supply is performed. The wireless communication unit 11 of the mobile terminal 10 has a function of converting microwaves received by the antenna 12 into DC power. Dedicated components for converting between microwaves and power may be provided in the management device 20 and the mobile terminal 10.

[0039] FIG. 3 is a schematic diagram showing an example of the configuration of mobile terminal 10 worn on a user's arm 50. As shown in FIG.

[0040] When mobile terminal 10 is worn on arm 50, for example, as shown in FIG. 3, band 102 fixed to housing 101 is wrapped around arm 50 of the user.

[0041] As shown in FIG. 3, water detection sensor 13 is preferably provided on the front surface of housing 101 of mobile terminal 10 (the surface opposite arm 50) to prevent erroneous detection due to water accumulating between arm 50 and housing 101 (detection of water when mobile terminal 10 is not in water).

[0042] In addition, it is preferable that the structure be such that water is less likely to accumulate on the sensor portion of the water detection sensor 13 when the mobile terminal 10 is in the air, for example, that the water detection sensor 13 protrudes from the surface of the housing 101, or that the area around the sensor portion is hydrophilic.

[0043] Operation switch 16 is preferably provided at a position such as the side of housing 101 where it is unlikely to be operated erroneously.

[0044] Antenna 12 connected to substrate 18 is preferably provided inside housing 101 at a position as far away from arm 50 as possible (upper side in FIG. 3) in order to minimize the influence of human body attenuation.

[0045] (Drowning Alert System Operation) 4 is a flowchart showing an example of the flow of processing performed by the management device 20. Specific processing performed by the management device 20 will be described below with reference to the flowchart in FIG.

[0046] First, when the management device 20 starts its operation and receives a wireless signal from a certain mobile terminal 10 for the first time, processing for that mobile terminal 10 is started.

[0047] The wireless signal transmitted by the mobile terminal 10 includes information regarding an identification number assigned to each of the multiple mobile terminals 10. When the wireless communication unit 21 of the management device 20 receives the wireless signal, it determines whether or not the mobile terminal 10 that transmitted the wireless signal is registered (step A1).

[0048] The determination in step A1 is performed, for example, by the control unit 27 referring to the registration information in which the identification numbers of the registered mobile terminals 10 are recorded and stored in the storage unit 24, and verifying the identification numbers.

[0049] If it is determined in step A1 that the mobile terminal is not registered, a terminal registration process is performed to record the identification number in the registration information (step A2).

[0050] Thereafter, depending on whether the wireless communication unit 21 can receive a wireless signal from the mobile terminal 10, it is determined whether the mobile terminal 10 is within a range in which it can communicate with the management device 20 (step A3).

[0051] If it is determined in step A3 that the mobile terminal 10 is not within a range in which it can communicate with the management device 20, the control unit 27 determines whether or not it has been determined that the mobile terminal 10 is within a range in which it can communicate with the management device 20 in the most recent period (e.g., within the past 6 seconds to 1 minute) (step A4).

[0052] The determination in step A4 is made by, for example, the control unit 27 referring to a record of past determinations of whether or not the mobile terminal 10 is within a range capable of communicating with the management device 20, which is stored in the storage unit 24. The reason for making the determination in step A4 using the record of past determinations is that, when a wireless signal is not received in step A3, the management device 20 cannot determine whether the wireless signal was interrupted while the mobile terminal 10 was underwater or because the user left the pool or bathtub.

[0053] If it is determined in step A4 that the mobile terminal 10 was not currently within a range capable of communicating with the management device 20, it is assumed that the mobile terminal 10 is not within the management range of the management device 20, such as a swimming pool or a bathtub, for example because the user wearing the mobile terminal 10 is outside the swimming pool or a bathtub, and the process is terminated.

[0054] If it is determined in step A3 that the mobile terminal 10 is within a range in which it can communicate with the management device 20, and if it is determined in step A4 that the mobile terminal 10 was previously within a range in which it can communicate with the management device 20, it is determined whether the mobile terminal 10 is currently detecting water or has detected water in the past (for example, in the past on the same day, or a few seconds to a few minutes ago) (step A5).

[0055] The determination in step A5 is made, for example, based on whether or not water detection information was included in the wireless signal received immediately before or in the past from the mobile terminal 10. The water detection information will be described later.

[0056] If it is determined in step A5 that the mobile terminal 10 is not detecting water and has not detected water in the past, it is assumed that the mobile terminal 10 is not in water, and the process ends.

[0057] If it is determined in step A5 that the mobile terminal 10 is detecting water or has previously detected water, it is determined whether the time during which the mobile terminal 10 is assumed to be continuously underwater exceeds a predetermined threshold value t (step A6). The threshold value t may be set by the user of the management device 20. Furthermore, the threshold value t may be recorded in advance in the storage unit 24, for example, and the control unit 27 may refer to this to compare with the time during which the mobile terminal 10 is assumed to be continuously underwater.

[0058] The determination in step A6 is performed by, for example, assuming that the time since the wireless signal from the mobile terminal 10 was no longer received is the time that the mobile terminal 10 has been continuously underwater, and comparing this with a threshold value t.

[0059] If it is determined in step A6 that the time that the mobile terminal 10 is assumed to be continuously underwater does not exceed the threshold value t, it is determined that the user wearing the mobile terminal 10 is not in a state where he or she is at risk of drowning, and processing is resumed from step A3.

[0060] In addition, in step A6, if the management device 20 continuously receives wireless signals including water detection information, it is assumed that the mobile terminal 10 is not in water and the water detection sensor 13 has detected water because the water detection sensor 13 is wet, so the water detection determination conditions may be corrected so that the sensitivity of the water detection sensor 13 is lowered.

[0061] Furthermore, if the management device 20 receives a wireless signal that does not include water detection information (which may include information that water has not been detected) a certain number of times, the time counted in step A6 since the wireless signal from the mobile terminal 10 was no longer received may be cleared (returned to zero) and the counting may be stopped. This is to prevent an alarm from being issued if the counting continues infinitely while steps A3 to A6 are repeated.

[0062] Furthermore, if the management device 20 does not receive a wireless signal for a certain period of time after receiving a wireless signal not including water detection information, the time counted in step A6 since the wireless signal from the mobile terminal 10 was no longer received may be cleared. In such a case, it is assumed that the user left the pool or bathtub immediately after the mobile terminal 10 transmitted a wireless signal not including water detection information, or that the user approached the pool or bathtub and then immediately left, so this is to prevent unnecessary time counting in step A6.

[0063] If it is determined in step A6 that the time that the mobile terminal 10 is assumed to be continuously underwater exceeds threshold value t, it is assumed that the user wearing the mobile terminal 10 is in a state where he or she is at risk of drowning, and therefore the alert unit 23 issues an alert (step A7).

[0064] If the user of the mobile terminal 10 wishes to stop the alert issued by the alert unit 23, the user can, for example, press the operation switch 16 of the mobile terminal 10 to transmit a wireless signal including instruction information to cancel the alert from the wireless communication unit 11 and stop the alert. Also, for example, the transmission of the wireless signal can be stopped for a certain period of time by performing an operation such as a long press on the operation switch 16. If the user of the management device 20 wishes to stop the alert issued by the alert unit 23, the user can, for example, press the operation switch 26 of the management device 20 to stop the alert.

[0065] 5 is a flowchart showing an example of a process flow of the mobile terminal 10. Hereinafter, specific processes of the mobile terminal 10 will be described with reference to the flowchart of FIG.

[0066] First, when the mobile terminal 10 starts operating, it is determined whether or not the mobile terminal 10 is being worn by a user based on the detection result of the wearing detection sensor 14 (step B1).

[0067] If it is determined in step B1 that the mobile terminal 10 is not attached to the user, step B1 is repeated until it is determined that the mobile terminal 10 is attached to the user.

[0068] Although the transmission of wireless signals by the wireless communication unit 11 may be started immediately after the operation of the mobile terminal 10 starts, it is preferable that the transmission be started when it is determined in step B1 that the mobile terminal 10 is attached to the user. In this case, it is possible to suppress consumption of the battery 15, and to prevent the management device 20 from erroneously determining that the user is in a state at risk of drowning when the mobile terminal 10 is not attached to the user.

[0069] If it is determined in step B1 that the mobile terminal 10 is worn by the user, water is detected by the water detection sensor 13 (step B2).

[0070] If water is detected by water detection sensor 13 in step B2, the baud rate of the wireless signal transmitted from wireless communication unit 11 is increased (step B3). This makes wireless communication between mobile terminal 10 and management device 20 more likely to be interrupted, improving the accuracy of determining whether mobile terminal 10 is underwater in step A6 of the processing by management device 20 described above.

[0071] Furthermore, in step B2, if water is detected by the water detection sensor 13, water detection information indicating that water has been detected by the water detection sensor 13 is included in the wireless signal. This water detection information is used in step A5 in the processing of the management device 20 described above.

[0072] For this reason, when the process of step B3 is performed, the baud rate of the wireless signal containing water detection information will be higher than the baud rate of the wireless signal not containing water detection information.

[0073] If it is determined in step B2 that the mobile terminal 10 is not underwater, the baud rate of the wireless signal is left at the initial value (step B4). This is to prevent the wireless communication between the mobile terminal 10 and the management device 20 from being interrupted when the mobile terminal 10 is not underwater by increasing the baud rate of the wireless signal.

[0074] For the same reason, if a certain period of time has elapsed during which the water detection sensor 13 does not detect water after the baud rate of the wireless signal has been increased in step B3, it is preferable to return the baud rate of the wireless signal to its initial value.

[0075] Next, it is determined whether or not the water depth at the position of the mobile terminal 10 is greater than a predetermined threshold value N (step B5).

[0076] The determination in step B5 is made using the water depth value detected by a water depth sensor included in the water detection sensor 13, or a water depth sensor provided in the mobile terminal 10 separately from the water detection sensor 13. The threshold value N may be set by the user of the management device 20. In this case, for example, the threshold value N is set in the mobile terminal 10 by remote communication by operating the management device 20. Furthermore, the threshold value N is recorded in advance, for example, in a flash memory provided in the mobile terminal 10, and the control unit 17 can refer to this and compare it with the water depth value detected by the water depth sensor.

[0077] If it is determined in step B5 that the water depth at the location of mobile terminal 10 is greater than the predetermined threshold N, it is assumed that the user is in a state where he or she is at risk of drowning, and therefore transmission of wireless signals by wireless communication unit 11 is stopped (step B6). This allows management device 20 to reliably determine in step A6 of the process described above that mobile terminal 10 is underwater.

[0078] If it is determined in step B5 that the water depth at the location of the mobile terminal 10 is not greater than the predetermined threshold value N, it is assumed that the user is not in a state where he or she is at risk of drowning at that time, and therefore the transmission of the wireless signal from the wireless communication unit 11 continues (step B7).

[0079] (Effects of the embodiment) In the drowning alert system 1 according to the embodiment of the present invention described above, when the time during which the wireless communication unit 21 serving as a wireless receiving unit of the management device 20 is unable to receive a wireless signal transmitted from the mobile terminal 10 exceeds a predetermined threshold value t, the alert unit 23 of the management device 20 issues an alarm. Therefore, the user's condition (whether or not there is a risk of drowning) can be determined with higher accuracy than in a system that makes a determination based on the strength of radio wave intensity, which varies widely.

[0080] Furthermore, when the mobile terminal 10 is equipped with the water detection sensor 13, the accuracy of determining the user's condition can be improved by using the water detection information as shown in the above embodiment. Furthermore, by increasing the baud rate of the wireless signal when the water detection sensor 13 detects water, the accuracy of determining the user's condition can be further improved.

[0081] Furthermore, if the mobile terminal 10 is equipped with a water depth sensor, as shown in the above embodiment, the detected water depth value can be used to improve the accuracy of determining the user's condition.

[0082] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention. Furthermore, the components of the above embodiment can be combined in any manner without departing from the spirit of the invention.

[0083] In addition, the above-described embodiments do not limit the scope of the invention according to the claims. Also, it should be noted that not all of the combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention. [Explanation of symbols]

[0084] 1. Drowning Alert System 11 Wireless Communication Section 12 Antenna 13 Water detection sensor 14 Wearing detection sensor 20 Management device 21 Wireless Communication Department 22 Antenna 23 Alert Section

Claims

1. A mobile terminal including a wireless transmission unit that continuously transmits wireless signals; A management device including a wireless receiving unit that receives the wireless signal and an alert unit that issues an alert; Including, When the time during which the wireless receiving unit is unable to receive the wireless signal exceeds a predetermined threshold, the alert unit issues an alarm. Drowning alert system.

2. The mobile terminal is equipped with a water detection sensor, When the water detection sensor detects water, water detection information indicating that the water detection sensor has detected water is included in the wireless signal; When the time during which the wireless receiving unit is unable to receive the wireless signal exceeds the threshold value and the wireless signal received immediately before includes the water detection information, the alert unit issues the alarm.

2. A drowning alert system as claimed in claim 1.

3. a baud rate of the wireless signal including the water detection information is higher than a baud rate of the wireless signal not including the water detection information; 3. A drowning alert system as claimed in claim 2.

4. The mobile terminal further includes a water depth sensor. When the water depth value detected by the water depth sensor is greater than a predetermined threshold value, the wireless transmission unit stops transmitting the wireless signal. A drowning alert system according to any one of claims 1 to 3.

5. When the management device continuously receives the wireless signal including the water detection information, the management device corrects the water detection determination condition of the water detection sensor. A drowning alert system according to claim 2 or 3.

6. The management device has a function as a power supply device for microwave wireless power supply, The mobile terminal has a function as a power receiving device for microwave wireless power supply. A drowning alert system according to any one of claims 1 to 3.

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