JP2015102510A - Search device and communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To find a victim with higher possibility than before, and reduce the time required for finding the victim.SOLUTION: In standby state, a device 2 to be searched supplies electric power to each section in a first period 321 (3 ms, for example), at first intervals, to perform receiving processing. A searching device 1 in search state transmits call signals repeatedly in a third period 312 longer than the first interval. On receipt of a call signal in the first period 321, the device 2 transmits a response signal including identification information of the device in a fourth period 322. The searching device 1 estimates a distance and direction of the device 2, by use of the response signal, every time the response signal is received, and displays identification information of the device 2 and information on the distance and direction of the device 2, on a screen.

Description

  The present invention relates to a search device for searching for another communication device (searched device), and a communication system including the search device and the searched device.

  There is a radio beacon system that informs the rescuer who carries a receiver by transmitting a radio wave (a small transmitter) carried by the climber when a climber is lost due to an avalanche. (Patent Document 1, Patent Document 2, Non-Patent Document 1, etc.).

  In this radio beacon system, the transmission device transmits 457 kHz radio waves as a rescue signal, and the reception device can know the direction and approximate distance of the transmission device from the received radio waves.

JP 2003-198389 A JP 2005-229449 A

Report on the study of advanced beacon system for searching for mountain victims (March 2005 Study session on advanced beacon system for searching for mountain victims)

  However, since the radio beacon system uses a medium-frequency band (457 kHz) and the transmission output is limited to a minute power range due to restrictions based on the Radio Law, the radio wave reception distance is about 100 m at the maximum. It cannot be searched if the distance between them is more than that.

  As described in Non-Patent Document 1, this type of communication system is required to have a long communication distance so that a wide range (for example, a radius of several hundred meters or more) can be searched.

  Furthermore, in this type of communication system, it is ensured that the device carried by the climber is small and light, that radio waves can be reliably emitted without a climber's operation in the event of a distress, and power saving Therefore, it is required to operate continuously over a long period (for example, 7 days or more).

  By developing a communication system that satisfies these requirements, it is expected that the possibility of finding a mountain victim or the like is further increased, and that the time until the discovery is further reduced.

  The object of the present invention has been made in view of the above points, and can increase the possibility of finding a mountain victim or the like and shorten the time until the discovery, compared to conventional ones. A search device and a communication system are provided.

  The search device of the present invention includes a portable housing, an antenna housed in the housing, for transmitting and receiving radio waves, a transmission means for transmitting a calling signal to the searched device via the antenna, and the antenna Receiving means for receiving a response signal from the searched device corresponding to the call signal via the distance between the own device and the searched device using the response signal received by the receiving means, and the own device And a control unit that estimates the direction of the searched device and displays identification information of the searched device and information on the estimated distance and direction.

  The communication system of the present invention is a communication system that includes a portable search device and a portable search device that performs wireless communication with the search device, and the search device is connected to the search target device. A first transmission means for transmitting a call signal, a first reception means for receiving a response signal from the predetermined searched device, a call signal generated and output to the first transmission means, and the reception First response means for estimating a distance between the own device and the searched device and a direction of the searched device viewed from the own device using a response signal received by the means, the searched device, A second receiving means for receiving the call signal from the search device; a second control means for generating the response signal upon receiving the call signal; and a response signal generated by the second control means. Second transmission means Take the deposition.

  In the communication system of the present invention, the first transmission unit transmits the call signal at a frequency of 710 MHz to 960 MHz, and the second transmission unit transmits the response signal at a frequency of 710 MHz to 960 MHz. Take.

  According to the present invention, it is not necessary for the searched device to always transmit a periodic signal such as a beacon, and it is only necessary to transmit a response signal when receiving a calling signal from the searching device. Compared to power consumption. Therefore, the search target device can operate continuously for a long period of time (for example, three months or more), so that the possibility of finding a mountain victim or the like can be increased.

  According to the present invention, since the search device and the search target device perform wireless communication using a frequency of 710 MHz or more and 960 MHz or less, the receivable distance of the radio wave from the search device in the search target device becomes long. Therefore, since the search device can search a wide range (for example, 100 m to 5 km), it is possible to increase the possibility of finding a mountain victim or the like and to shorten the time until the discovery.

1 is an external view of a search device according to an embodiment of the present invention. 1 is an external view of a search target device according to an embodiment of the present invention. The block diagram which shows the structure of the search device which concerns on one embodiment of this invention. The block diagram which shows the structure of the to-be-searched apparatus which concerns on one embodiment of this invention. The sequence diagram which shows the mode of communication with the search device and search target device which concern on one embodiment of this invention The sequence diagram which shows the mode of communication with the search device and search target device which concern on one embodiment of this invention Diagram showing the relationship between distance and received signal strength The figure which shows the directivity formed by the search device which concerns on one embodiment of this invention The figure which shows the information table stored in the memory part of the search device which concerns on one embodiment of this invention. The figure which shows the display screen of the search device which concerns on one embodiment of this invention. The flowchart which shows the flow of operation | movement of the search device which concerns on one embodiment of this invention. The flowchart which shows the flow of operation | movement of the search device which concerns on one embodiment of this invention. The flowchart which shows the flow of operation | movement of the to-be-searched apparatus which concerns on one embodiment of this invention.

(Embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The communication system according to the present invention includes a search device 1 (see FIGS. 1 and 3) and one or a plurality of search target devices 2 (see FIGS. 2 and 4). The search device 1 performs wireless communication with each search target device 2. The search device 1 has all the functions of the search target device 2 and can perform wireless communication with other search devices as the search target device.

[Communication mode]
The search device 1 of the present invention executes one of the following communication modes based on a user instruction.
(1) Individual search mode (2) Full search mode (3) Group search mode (4) Searched mode

  (1) In the individual search mode, the search device 1 performs wireless communication with the single searched device 2 instructed by the user, and estimates the relative position (distance and direction) of the single searched device 2. Mode. Note that the search device 1 can register the search target device 2 in advance in association with a registration number (for example, 1 to 10).

  (2) The all search mode is a mode in which the search device 1 requests transmission of response signals for all the search target devices 2 and specifies the search target devices 2 that can receive the response signals and communicate with each other.

  (3) In the group search mode, the search device 1 requests transmission of a response signal to all the search target devices 2 registered in advance, and receives the response signal to identify the searchable device 2 that can communicate. Mode.

  (4) The search mode is a mode in which the search device 1 performs wireless communication with another search device as the search target device.

[Structure of search device 1]
First, the structure of the search device 1 will be described with reference to FIG. FIG. 1 is an external view of a search device 1 according to the present embodiment. 1A is a front view, FIG. 1B is a right side view, FIG. 1C is a rear view, and FIG. 1D is a cross-sectional view along AA.

  The search device 1 has a size (for example, width W: 64 mm, height H: 107 mm, thickness T: 13 mm) and weight (for example, 70 g) that a user (general person) can carry.

  The casing 11 of the search device 1 has a substantially rectangular shape and is formed of a non-conductive member. The front surface 11a of the housing 11 has a flat plate shape. A display unit 12 and an operation unit 13 are provided on the front surface 11 a of the housing 11.

  The display unit 12 is provided on the front surface 11a of the housing 11, and has a screen configured by, for example, an LCD (Liquid Crystal Display). The display screen in each communication mode will be described later.

  The operation unit 13 is provided in the vicinity of the bottom surface 11b side (lower end side) on the front surface 11a of the housing 11 and has a plurality of buttons. The operation unit 13 converts the button operation content based on the user's will into an electric signal and transmits it to a CPU (Central Processing Unit) 131 (see FIG. 3).

  The side surfaces 11c and 11d of the housing 11 are thinner on the flat surface 11e side (upper end side) than the bottom surface 11b (lower end side) with the central portion as a boundary. A power switch 14 is provided on the right side surface 11c.

  A substrate 15 is housed inside the housing 11. The antenna 101 is patterned on the plane 11e side (upper end side) from the center of the substrate 15. Various circuits (see FIG. 3) are placed on the substrate 15.

  The antenna 101 includes a first antenna element 111 serving as a radiator at the center, and a second antenna element 112 and a third antenna element 113 each serving as a director or a reflector on both sides thereof.

  The length of the first antenna element 111 is ¼ (λ / 4) of the wavelength λ. For example, when the search device 1 performs wireless communication using 920 MHz, the length (λ / 4) of the first antenna element 111 is about 81.5 mm. The lengths of the second antenna element 112 and the third antenna element 113 are the same and are slightly shorter than the first antenna element 111.

  Each antenna element 111, 112, 113 is formed in a folded pattern so as to be accommodated in a space of length H1 (for example, 40 mm), and is patterned on both surfaces of the substrate 15 and connected in a through hole.

  A recess 16 is provided at the center of the back surface 11 f of the housing 11. When the user holds the search device 1 so that the user can press the button of the operation unit 13 with the first finger (thumb), the user can stabilize the search device 1 by placing the second finger (index finger) in the recess 16. Can have.

[Structure of searched device 2]
Next, the structure of the search target device 2 will be described with reference to FIG. FIG. 2 is an external view (front view) of the search target device 2 according to the present embodiment.

  The search target device 2 has a size (for example, width W: 40 mm, height H: 63 mm, thickness T: 13 mm) and weight (for example, 20 g) that can be carried by a user (general person).

  The casing 21 of the search device 2 has a substantially square shape and is formed of a non-conductive member. An LED (Light Emitting Diode) 22 and a power switch 23 are provided on the front surface 21 a of the housing 21.

  The LED 22 emits light (flashes) at a predetermined timing, for example, when a radio wave is received from the search device 1 in the individual search mode.

  An antenna (see FIG. 4) and a substrate (not shown) are housed inside the housing 21. Various circuits (see FIG. 4) are placed on the substrate.

  On the plane (upper end) of the housing 21, a convex portion 24 having a hole 24a for passing a string or the like is provided. By tying the string passed through the hole 24a to the user's clothes (such as a belt), the searched device 2 does not leave the user even when the user is in an avalanche or the like.

[Circuit Configuration of Searching Device 1 (Block Diagram)]
Next, the circuit configuration of the search device 1 will be described with reference to FIG. FIG. 3 is a block diagram showing a configuration of search device 1 according to the present embodiment. The search device 1 includes a housing 11 (not shown in FIG. 3), a display unit 12, an operation unit 13, a power switch 14 (not shown in FIG. 3), and a substrate 15 (not shown in FIG. 3). ), The antenna 101, the wireless unit 102, the control unit 103, the ringing unit 104, and the battery 105. The wireless unit 102 and the control unit 103 are placed on the substrate 15.

  The wireless unit 102 processes a wireless signal. The wireless unit 102 includes a transmission unit 121, a reception unit 122, a wireless control unit 123, a first clock 124, a first switch 125, a second switch 126, and a third switch 127.

  The transmission unit 121 performs radio transmission processing such as modulation, amplification, and up-conversion on the baseband digital signal output from the CPU 131 and transmits the radio signal from the first antenna element 111. The frequency of the radio wave (call signal or the like) transmitted from the transmission unit 121 is 710 MHz or more and 960 MHz or less.

  The reception unit 122 performs wireless reception processing such as amplification, down-conversion, and demodulation on the wireless signal received by the first antenna element 111 and outputs a baseband digital signal to the CPU 131. In addition, the reception unit 122 measures a received signal strength indicator (RSSI) of a radio wave received by the first antenna element 111 and outputs a measurement value (analog value) to the radio control unit 123.

  The wireless control unit 123 controls each unit in the wireless unit 102 using the clock signal of the first clock 124. In addition, the wireless control unit 123 converts the measurement value of the received signal strength output from the receiving unit 122 into a digital value and outputs the digital value to the CPU 131. Details of the control performed by the wireless control unit 123 for the switches 125, 126, and 127 will be described later.

  The first clock 124 is a high-speed and high-accuracy clock, and generates a reference clock signal having a predetermined frequency (for example, 36 MHz) for use inside the wireless unit 102.

  The first switch 125 connects either the transmission unit 121 or the reception unit 122 and the first antenna element 111 in accordance with an instruction from the radio control unit 123. The second switch 126 connects / disconnects between the substrate 15 and the second antenna element 112 in accordance with an instruction from the wireless control unit 123. The third switch 127 connects / disconnects between the substrate 15 and the third antenna element 113 in accordance with an instruction from the wireless control unit 123.

  The control unit 103 performs baseband signal processing. The control unit 103 includes a CPU 131, a memory unit 132, a second clock 133, a third clock 134, and a logical operation unit 135.

  The CPU 131 is a central processing unit of the control unit 103 and executes various programs using the memory unit 132 as a work memory. In particular, the CPU 131 generates a signal to be transmitted to the search target device 2, and when the radio wave is received from the search target device 2, the CPU 131 displays the acquired predetermined information on the display unit 12, and the ringing unit 104 notifies the notification sound. Is output.

  The memory unit 132 includes a ROM (Read Only Memory) and a RAM (Random Access Memory), and stores various programs executed by the CPU 131 and various data.

  The second clock 133 is a low-speed clock, and generates a reference clock signal having a predetermined frequency (for example, 32 kHz) for use inside the control unit 103 in a standby state or the like. The third clock 134 is a high-speed and high-accuracy clock, and generates a reference clock signal having a predetermined frequency (for example, 40 MHz) for use inside the control unit 103 in a communication state with the search target device 2 or the like.

  The logical operation unit 135 cooperates with the CPU 131 to determine the difference between the transmission timing of the transmission frame and the reference clock of the third clock 134, the difference between the reception timing of the reception frame and the reference clock of the third clock 134, Based on the difference between the transmission timing of the transmission frame and the reference clock of the third clock 234 (see FIG. 4) and the difference between the reception timing of the reception frame and the reference clock of the third clock 234 in the search device 2 The propagation delay time of the transmission line between 2 is calculated.

  The ringing unit 104 outputs a notification sound from the speaker at a predetermined timing, for example, when receiving an instruction from the user.

  The battery 105 is housed in the housing 11, and supplies power to each part of the search device 1 when a user turns on the power via the power switch 14.

[Function of CPU 131]
Next, functions of the CPU 131 of the search device 1 will be described with reference to FIG. The CPU 131 includes a signal generation unit 131a, a signal acquisition unit 131b, a distance estimation unit 131c, and a direction estimation unit 131d as functions according to the present invention.

  The signal generation unit 131a generates a digital signal sequence (transmission frame) including various types of information based on a user instruction (electrical signal input from the operation unit 13) and outputs the digital signal sequence (transmission frame) to the transmission unit 121. In the individual search mode, the signal generation unit 131a includes the identification information of the single searched device 2 and the identification information of the own device instructed by the user in the digital signal. In the all search mode, the signal generation unit 131a includes, in the digital signal, information indicating that all of the search target devices 2 request transmission of response signals. In the group search mode, the signal generation unit 131a includes identification information of all search target devices 2 belonging to the group instructed by the user in the digital signal. In the search mode, when the signal generation unit 131a inputs information requesting transmission of identification information of its own device from the signal acquisition unit 131b, the signal generation unit 131a receives the identification information of its own device and the identification information of the communication partner searching device 1 as a digital signal. Include in In the individual search mode, the signal generation unit 131a includes, in the digital signal (response confirmation signal), information that instructs the search target device 2 to emit light or output a notification sound based on an instruction from the user. Also good.

  In a communication mode other than the search mode, the signal acquisition unit 131b acquires identification information of the search target device 2 from the digital signal sequence (reception frame) of the received response signal and outputs the identification information to the display unit 12. In the searched mode, the signal acquisition unit 131b acquires information from the digital signal sequence (reception frame) of the received call signal, and when the information requests transmission of identification information of the own device, The fact is output to the signal generator 131a. In the all search mode, the signal acquisition unit 131b is based on the user's instruction, and (1) only the one having the highest received signal strength among the acquired identification information of the search target device 2 is registered (2). Any one of (3) that matches the existing identification information may be output to the display unit 12.

  The distance estimation unit 131c estimates the distance to the search target device 2 based on the received signal strength of the radio wave measured by the reception unit 122 or the propagation delay time calculated by the logic operation unit 135 in the individual search mode. The estimated value is output to the display unit 12. Details of the distance estimation in the present embodiment will be described later.

  The direction estimation unit 131d receives the received signal strength when the second switch 126 is ON and the third switch 127 is OFF and the reception when the second switch 126 is OFF and the third switch 127 is ON in the individual search mode. Based on the signal strength, the direction of the search target device 2 is estimated, and the estimated value is output to the display unit 12. Details of direction estimation in the present embodiment will be described later.

[Circuit Configuration of Searched Device 2 (Block Diagram)]
Next, the circuit configuration of the search target device 2 will be described with reference to FIG. FIG. 4 is a block diagram showing a configuration of searched device 2 according to the present embodiment. The searched device 2 includes a housing 21 (not shown in FIG. 4), an LED 22, a power switch 23 (not shown in FIG. 4), a substrate (not shown), an antenna 201, and a wireless unit 202. And a control unit 203, a ringing unit 204, and a battery 205.

  The radio unit 202 processes radio signals. The wireless unit 202 includes a transmission unit 221, a reception unit 222, a wireless control unit 223, a first clock 224, and a first switch 225.

  The transmission unit 221 performs radio transmission processing such as modulation, amplification, and up-conversion on the baseband digital signal output from the CPU 231, and transmits a radio signal from the antenna 201. The frequency of the radio wave (response signal or the like) transmitted from the transmission unit 221 is 770 MHz or more and 960 MHz or less.

  The reception unit 222 performs wireless reception processing such as amplification, down-conversion, and demodulation on the wireless signal received by the antenna 201 and outputs a baseband digital signal to the CPU 231.

  The wireless control unit 223 controls each unit in the wireless unit 202 using the clock signal of the first clock 224.

  The first clock 224 is a high-speed and high-accuracy clock, and generates a reference clock signal having a predetermined frequency (for example, 36 MHz) for use inside the wireless unit 202.

  The first switch 225 connects either the transmission unit 221 or the reception unit 222 and the antenna 201 in accordance with an instruction from the wireless control unit 223.

  The control unit 203 performs baseband signal processing. The control unit 203 includes a CPU 231, a memory unit 232, a second clock 233, and a third clock 234.

  The CPU 231 is a central processing unit of the control unit 203 and executes various programs using the memory unit 232 as a work memory. In particular, the CPU 231 generates a signal to be transmitted to the search device 1, and causes the LED 22 to emit light when the radio wave is received from the search device 1 or when an instruction is received from the search device 1. Is output.

  The memory unit 232 includes a ROM (Read Only Memory) and a RAM (Random Access Memory), and stores various programs executed by the CPU 231 and various data.

  The second clock 233 is a low-speed clock, and generates a reference clock signal having a predetermined frequency (for example, 32 kHz) to be used inside the control unit 203 in a standby state or the like. The third clock 234 is a high-speed and high-accuracy clock, and generates a reference clock signal having a predetermined frequency (for example, 40 MHz) to be used inside the control unit 203 in a communication state with the search device 1 or the like.

  The ringing unit 204 outputs a notification sound from the speaker at a predetermined timing, for example, when a radio wave is received from the search device 1.

  The battery 205 is housed in the housing 21, and supplies power to each part of the search target device 2 when a user turns on the power via the power switch 23.

[Function of CPU 231]
Next, functions of the CPU 231 of the search target device 2 will be described with reference to FIG. The CPU 231 includes a signal generation unit 231a and a signal acquisition unit 231b as functions according to the present invention.

  When the signal generation unit 231a receives information requesting transmission of its own identification information from the signal acquisition unit 231b, the signal generation unit 231a includes a digital signal sequence (transmission frame) including the identification information of the own device and the identification information of the search device 1 of the communication partner. ) And output to the transmission unit 221.

  The signal acquisition unit 231b acquires information from the digital signal sequence (reception frame) of the received call signal, and if the information requests transmission of identification information of the own device, generates a signal to that effect. To the unit 231a. Further, the signal acquisition unit 231 b causes the LED 22 to emit light and output a notification sound from the ringing unit 204 when receiving radio waves from the search device 1 or receiving an instruction from the search device 1.

[Communication sequence in individual search mode]
Next, communication in the individual search mode between search device 1 and search target device 2 according to the present embodiment will be described using the sequence diagram of FIG.

  After the power is turned on, the search device 1 is in a standby state until an instruction from the user (button operation of the operation unit 13) is received. In the standby state, power is not supplied to each unit of the search device 1 in order to reduce power consumption (sleep state). However, power is supplied from the battery 105 to the operation unit 13 and the second clock 133. The second clock 133 always counts by operating a low-speed clock circuit.

  The searched device 2 enters a standby state after being powered on. In the standby state, power is not supplied to each unit of the searchee device 2 in order to reduce power consumption (sleep state). However, power is supplied from the battery 205 to the second clock 233. The second clock 233 always counts by operating a low-speed clock circuit.

  At every first interval (for example, 3 s) until the count value of the second clock 233 expires, the searchee device 2 supplies power to each unit (activated state). In the activated state, the searchee device 2 performs reception processing in the first period 321 (for example, 3 ms). At this time, the first clock 224 performs a count operation by operating the clock circuit.

  Then, in the first period 321, the searchee device 2 returns to the sleep state when the information requesting transmission of the identification information of the own device cannot be acquired.

  In the standby state, when the user instructs the identification information of the search target device 2 to be searched, the search device 1 supplies power to each unit and starts searching for the search target device 2 (search state). At this time, the first clock 124 and the third clock 134 perform a counting operation by operating a high-speed clock circuit.

  The search device 1 that has entered the search state first performs reception processing in the second period 311 (for example, 5 ms) in order to confirm that the other search devices 1 are not transmitting radio waves. Then, when the search device 1 does not receive the radio wave from the other search device 1 during the second period 311, the search device 1 in the third period 312 (for example, 3.5 s) longer than the first interval. The call signal including the identification information, the identification information of the search target device 2 to be searched, and the timing information indicating the transmission timing of the response signal to the search target device 2 is repeatedly transmitted.

  The searched device 2 starts communication with the search device 1 (communication state) when receiving the calling signal during any of the first periods 321-3. At this time, the third clock 234 performs a count operation by operating a high-speed clock circuit. Then, in the fourth period 322-1 (for example, 2 ms) designated by the timing information included in the call signal, the searched device 2 detects its own identification information, identification information of the communication partner searching device 1, and distance information ( A response signal including the difference between the transmission timing of the transmission frame and the reference clock of the third clock 234 and the difference between the reception timing of the reception frame and the reference clock of the third clock 234 (in the following description, the call signal is received) Then, the first response signal to be transmitted is referred to as “call response signal”).

  The search device 1 performs reception processing in the fifth period 313 (for example, 3 ms). Then, as soon as the search device 1 receives the call response signal, in the sixth period 314-1 (for example, 2 ms), the response confirmation signal including the identification information of the own device and the identification information of the search target device 2 to be searched. Send. The baseband frequency of the response confirmation signal is different from that of the call signal. Therefore, even if the searched device 2 receives the response confirmation signal and the calling signal from the other searching device 1 at the same time, no interference occurs.

  The searched device 2 performs reception processing in a seventh period 323-1 (for example, 3 ms) immediately after the fourth period 322-1. And the to-be-searched apparatus 2 will transmit a response signal again in the 4th period 322-2 after the 2nd space | interval (for example, 100 ms) shorter than a 1st interval will pass, if a response confirmation signal is received.

  Thereafter, the communication system repeats transmission / reception of response signals and transmission / reception of response confirmation signals until a disconnection instruction is received from the user. Each time the search device 1 receives a response signal, the search device 1 estimates the distance and direction of the search target device 2 using the response signal, and obtains identification information of the search target device 2 and information on the distance and direction of the search target device 2. It is displayed on the screen of the display unit 12.

  When there is a disconnection instruction from the user, in the next sixth period 314-7, the search device 1 disconnects its own identification information, identification information of the search target device 2 to be searched, and the search target device 2. A disconnection signal including information for transmitting is transmitted.

  When the searchee device 2 receives the disconnection signal in the corresponding seventh period 323-7, in the next fourth period 322-8, the searchee device 2 receives the identification information of the own device, the identification information of the communication partner search device 1, and the disconnection signal. A disconnection response signal including information indicating that it has been received is transmitted.

  In the next sixth period 314-8, search device 1 transmits a disconnection confirmation signal including its own identification information, identification information of search target device 2 to be searched, and information indicating that a disconnection response signal has been received. Return to the standby state. In addition, when the searchee device 2 receives the disconnection confirmation signal in the next seventh period 323-8, the searchee device 2 returns to the standby state.

[Communication sequence in full search (group search) mode]
Next, the state of communication in the individual search mode between search device 1 and search target device 2 according to the present embodiment will be described using the sequence diagram of FIG. Note that the sequence of the group search mode is the same as that of the full search mode. In addition, since the states of the search device 1 and the search target device 2 in the standby state are the same in all communication modes and have already been described with reference to FIG. 5, description thereof is omitted here.

  In FIG. 6, it is assumed that there are four search target devices 2 (2-1, 2-2, 2-3, 2-4) in a range where radio waves of the search device 1 reach.

  In the all search mode, the search device 1 in the communication state first performs reception processing in the second period 311 (for example, 5 ms) in order to confirm that the other search devices 1 are not transmitting radio waves. Then, when the search device 1 does not receive radio waves from the other search devices 1 during the second period 311, the search device 1 performs all the coverage in the third period 312 (for example, 3.5 s) longer than the first interval. The calling signal including information requesting the search device 2 to transmit identification information is repeatedly transmitted.

  When each search target device 2 receives a call signal during any of the first periods 321-12, 321-22, 321-31, and 321-41, the first interval time from the start of the first period 321 is received. In a fourth period 322 after the elapse, a call response signal including identification information of the own device is transmitted.

  After the expiration of the third period 312, the search device 1 receives the call response signal in a fifth period 313 (for example, 3.5 s) longer than the first interval.

  Thereafter, the communication system repeats transmission / reception of the paging signal and transmission / reception of the paging response signal for a predetermined number N. The search device 1 displays the identification information of the search target device 2 included in the received call response signal on the screen of the display unit 12. Thereafter, the searching device 1 and each searched device 2 return to the standby state.

[Distance estimation]
Next, a method for estimating the distance to the search target device 2 by the search device 1 according to the present embodiment will be described. As a distance estimation method in the field of wireless communication, a first distance estimation method based on received signal strength and a second distance estimation method based on propagation delay time are known.

  FIG. 7 is a diagram illustrating the relationship between distance and received signal strength. In FIG. 7, the horizontal axis represents distance (m), and the vertical axis represents received signal strength (dBm). As shown in FIG. 7, there is a correlation between the distance and the received signal strength, and the longer the distance, the lower the received signal strength. The first distance estimation method is a method of estimating a distance using a correlation between this distance and the received signal strength.

  Here, as shown in FIG. 7, the longer the distance is, the smaller the fluctuation amount of the received signal strength with respect to the unit distance is. Therefore, when the distance to the search target device 2 is short, the search device 1 can estimate the distance with high accuracy by using the first distance estimation method. On the other hand, when the distance to the search target device 2 is long, the radio wave fluctuation becomes gentle. Therefore, when the first distance estimation method is used, the distance cannot be estimated with high accuracy.

  The second distance estimation method is a method for estimating the distance by multiplying the calculated propagation delay time by the speed of the radio wave. The estimation accuracy of the second distance estimation method is substantially constant regardless of the distance. In addition, when the distance to the search target device 2 is long, higher estimation accuracy is not required than when the distance is short.

  In view of the above points, the distance estimation unit 131c of the search device 1 according to the present embodiment receives signals when the measured received signal strength is greater than a predetermined threshold (for example, −50 dBm) (short-distance mode). The distance to the search target device 2 is estimated using the first distance estimation method based on the signal strength, and the search target is searched using the second distance estimation method based on the propagation delay time when it is equal to or less than a predetermined threshold (wide area mode). The distance to the device 2 is estimated.

  In the present embodiment, hysteresis control is used to switch the estimation method, the first threshold for switching from the first distance estimation method to the second distance estimation method, and the second distance estimation method to the first distance estimation method. A second threshold value (> first threshold value) for switching may be set. As a result, it is possible to prevent the estimated distance from greatly changing in a short time due to frequent switching of the estimation method.

  Further, in the present embodiment, switching from the first distance estimation method to the second distance estimation method is performed based on the magnitude relationship between the received signal strength and the third threshold value, and the second distance estimation method to the first distance estimation method. Switching to may be performed based on the magnitude relationship between the propagation delay time and the fourth threshold value.

[Antenna control and direction estimation]
Next, a method for controlling the antenna 101 by the search device 1 and a method for estimating the direction of the search target device 2 according to the present embodiment will be described.

  When receiving the radio wave (response signal), the radio control unit 123 controls the first switch 125 to connect the first antenna element 111 and the receiving unit 122.

  In the individual search mode, the wireless control unit 123 turns on the second switch 126 and connects the substrate 15 and the second antenna element 112 in the first partial period during the reception period of the radio wave (response signal). Then, the third switch 127 is turned OFF to disconnect between the substrate 15 and the third antenna element 113.

  By this control, the connected second antenna element 112 and substrate 15 are longer than the first antenna element 111 (radiator) as a whole, and thus act as a reflector. Moreover, since the 3rd antenna element 113 becomes shorter than the 1st antenna element 111 (radiator), it acts as a waveguide.

  As a result, the first reception directivity 801 in FIG. 8 is formed in the first partial period. At this time, if the user holds the search device 1 substantially horizontally with the plane 11e side (upper end side) in front, the search device 1 can strongly receive radio waves from diagonally forward right.

  In addition, the wireless control unit 123 turns off the second switch 126 and disconnects the substrate 15 from the second antenna element 112 in the second partial period during the reception period of the radio wave (response signal), and the third switch 127 is turned on to connect between the substrate 15 and the third antenna element 113.

  By this control, the connected third antenna element 113 and substrate 15 are longer than the first antenna element 111 (radiator) as a whole, and thus act as a reflector. Moreover, since the 2nd antenna element 112 becomes shorter than the 1st antenna element 111 (radiator), it acts as a waveguide.

  As a result, the second reception directivity 802 in FIG. 8 is formed in the second partial period. At this time, if the user holds the search device 1 substantially horizontally with the plane 11e side (upper end side) in front, the search device 1 can strongly receive radio waves from the diagonally left front.

  When the search target device 2 to be searched exists on the right side of the user, the received signal strength in the first partial period is higher than the received signal strength in the second partial period. Conversely, when the search target device 2 to be searched exists on the left side of the user, the received signal strength in the first partial period is lower than the received signal strength in the second partial period.

  Therefore, according to the present embodiment, the direction of searched device 2 can be estimated from the magnitude and magnitude relationship of the difference in received signal strength between the first partial period and the second partial period.

  Note that the radio control unit 123 turns off the second switch 126 and the third switch 127 during radio wave transmission in the individual search mode, in the full search mode, in the group search mode, and in the searched mode, and the search device 1 is omnidirectional. Sexual transmission / reception may be performed.

  In the present embodiment, as shown in FIG. 9, the memory unit 132 stores an information table indicating an estimated direction based on the magnitude of the difference in received signal strength and its sign (magnitude relationship). The direction estimation unit 131d estimates the direction of the search target device 2 with reference to the information table of FIG. 9 from the received signal strengths measured in the first partial period and the second partial period, and calculates the estimation result. Output to the display unit 12.

  Note that the direction estimation unit 131d may average the received signal strength measured a plurality of times and estimate the direction of the search target device 2 using the average value. Thereby, the influence of the fluctuation | variation of a propagation path can be absorbed.

[Display screen]
Next, information displayed on the screen of the search device according to the present embodiment will be described with reference to FIG.

  FIG. 10A is a screen at the time of starting the individual search mode when starting the search for the already-searched apparatus 2 that has already been registered. On this screen, an identification number (identification information) 1001 of the search target device 2 to be searched is displayed together with the registration number. When the user instructs search execution in this display state, the search apparatus 1 executes the individual search mode for the search target apparatus 2 whose identification number is displayed on the screen.

  FIG. 10B is a screen at the start of the individual search mode when starting the search for the unregistered search target device 2. This screen displays a portion 1002 in which the input of the identification number (identification information) of the search target device 2 to be searched is completed. When the user instructs the search execution in this display state after completing the input of the identification number, the search device 1 executes the individual search mode (see FIG. 5) for the searched device 2 whose identification number is displayed on the screen. .

  FIG. 10C is a screen at the start of the full search mode. On this screen, a character 1003 of “ALL” is displayed. When the user instructs search execution in this display state, the search device 1 executes the all-in-one search mode (see FIG. 6).

  FIG. 10D is a screen at the start of the group search mode. On this screen, a character 1004 of “registration ALL” is displayed. When the user instructs search execution in this display state, the search device 1 executes the group search mode (see FIG. 6) for all the search target devices 2 registered in advance.

  FIG. 10E is a screen when the individual search mode is executed and a response signal is received from the searchee device 2. This screen shows the identification information 1005-1 of the searched device 2 that has responded, the information 1005-2 about the distance to the searched device 2, the information 1005-3 about the direction of the searched device 2, and the received signal strength. Information 1005-4 and the like are displayed on the screen.

  In the present embodiment, the update of the information 1005-3 regarding the direction of the searchee device 2 is limited to one step at a time. For example, when the previous direction estimation result is 75 ° left and the next direction estimation result is 30 ° right, the screen approaches from the left 75 ° to 30 ° right by one step (15 °). Information indicating the left 60 ° is displayed. Thereafter, when the direction estimation result is continuously 30 ° to the right, information indicating 45 ° left, 30 ° left 15 ° left, 0 °, 15 ° right, and 30 ° right is sequentially displayed on the screen. Is done. Thereby, the influence of the temporary and rapid fluctuation | variation of the estimated direction by radio wave interruption etc. can be absorbed. In addition, the directivity of FIG. 8 varies depending on the user's way of holding the search device 1 and the like, and the direction estimated from the received signal strength and the actual direction of the search target device 2 do not necessarily match. The direction estimation of the form can roughly estimate the direction of the search target device 2 and is sufficiently effective.

  FIG. 10F is a screen when the full search mode or the group search mode is executed and a call response signal is received from the searchee device 2. On this screen, identification information 1006 of all searched devices 2 to be searched is displayed on the screen. At this time, the identification information 1006 of the search target device 2 is displayed from the top in descending order of the received signal strength.

[Description of flow]
Next, the flow of the operation of search device 1 according to the present embodiment will be described using FIG. 11A and FIG. 11B.

  Search device 1 enters a sleep state when power is turned on (ST1101), and waits for an instruction from the user in this state (ST1102).

  When the instruction from the user is the individual search mode (ST1102: individual search mode), the search device 1 transmits a call signal to the search target device 2 (ST1103, ST1104). Then, search device 1 performs reception processing at the timing instructed to searched device 2 in the call signal (ST1105).

  If the call response signal cannot be received in ST1105 (ST1106: NO), search device 1 repeats the steps from ST1104 to ST1106 (ST1107: NO, ST1108). If the call response signal is not received even if the call signal is transmitted M times (ST1107: YES), search device 1 displays a message indicating that there is no response on the screen of display unit 12 (ST1109). Then, the flow proceeds to ST1132.

  If the call response signal can be received in ST1105 (ST1106: YES), search device 1 immediately transmits a response confirmation signal to searched device 2 (ST1110). Search device 1 measures the received signal strength of the response signal (ST1111), estimates the distance to search target device 2 (ST1112), and estimates the direction of search target device 2 (ST1113). Then, search device 1 displays the identification information of search target device 2 and the information related to the distance and direction of search target device 2 on the screen of display unit 12 (ST1114).

  After that, if there is no instruction to end the search from the user (ST1115: NO) and the timer does not end after counting a predetermined time (ST1116: NO), the search device 1 performs the receiving process again at a predetermined interval ( ST1117).

  When the response signal cannot be received in ST1117 (ST1118: NO), search device 1 repeats steps ST1115 to ST1117. On the other hand, if a response signal can be received in ST1117 (ST1118: YES), the flow returns to ST1110, and search device 1 repeats the steps from ST1110 to ST1117 (communication state).

  In this communication state, when the user gives an instruction to end the search (ST1115: YES), or when the timer ends by measuring a predetermined time (ST1116: YES), the search device 1 transmits a disconnection signal, A disconnection signal reception and disconnection confirmation signal transmission disconnection process is performed (ST1119). Then, the flow proceeds to ST1132.

  In ST1102, when the instruction from the user is the full search mode or the group search mode (ST1102: full search mode, group search mode), search device 1 is registered for all search target devices 2 or in advance. Call signals are transmitted to all the searched devices 2 all at once (ST1121, ST1122), and reception processing is performed over a predetermined period (ST1123). Searching apparatus 1 repeats steps ST1122 and ST1123 N times (ST1124, ST1125).

  When no response signal has been received in N times of ST1123 (ST1126: NO), search device 1 displays a message indicating that there is no response on screen of display unit 12 (ST1127). ). Then, the flow proceeds to ST1132.

  If even one response signal can be received in N times of ST1123 (ST1126: YES), searching device 1 displays the identification information of searched device 2 on the screen of display unit 12 (ST1128).

  After that, if there is no instruction to shift to the individual search mode or an instruction to end the search from the user (ST1129: NO, ST1130: NO), and the timer does not end after measuring a predetermined time (ST1131: NO), search device 1 Repeats step ST1128.

  If there is an instruction to shift to the individual search mode after ST1128 (ST1129: YES), the flow proceeds to ST1103. If the search is instructed by the user (ST1130: YES), or if the timer expires after measuring a predetermined time (ST1131: YES), the flow proceeds to ST1132.

  If the power is not turned off in ST1132, (ST1132: NO), the flow returns to ST1101. On the other hand, if the power is turned off in ST1132 (ST1132: YES), the flow ends.

  In ST1102, when the instruction from the user is the search mode (ST1102: search mode), the flow proceeds to ST1201 in FIG. 12, and search device 1 operates as the search target device.

  Next, the flow of operation of the searchee device 2 according to the present embodiment will be described using FIG.

  The searchee device 2 enters a sleep state when the power is turned on (ST1201), and performs reception processing periodically (at the first interval) (ST1202).

  If the call signal cannot be received in ST1202 (ST1203: NO), searched device 2 returns to the sleep state of ST1201.

  When a call signal can be received in ST1202 (ST1203: YES), searched device 2 transmits a response signal to search device 1 at a designated timing (ST1204), and immediately performs reception processing (ST1205). .

  If a response confirmation signal can be received in ST1205 (ST1206: YES), searched device 2 transmits a response signal again to searching device 1 after a predetermined time (second interval) has passed (ST1204). Thereafter, when a response confirmation signal can be received (ST1206: YES), steps ST1204 and ST1205 are repeated.

  If no response confirmation signal is received in ST1205 (ST1206: NO) and a disconnection signal is received (ST1207: YES), searched device 2 performs a disconnection process of disconnection response signal transmission and disconnection confirmation signal reception (ST1208). . Then, the flow proceeds to ST1209.

  If neither a response confirmation signal nor a disconnection signal is received in ST1205 (ST1206: NO, ST1207: NO), the flow proceeds to ST1209.

  If the power is not turned off in ST1209 (ST1209: NO), the flow returns to ST1201. On the other hand, if the power is turned off in ST1209 (ST1209: YES), the flow ends.

[effect]
As described above, according to the present embodiment, the searched device 2 does not always need to transmit a periodic signal such as a beacon, and only receives a response signal when receiving a call signal from the searching device 1. Since transmission is sufficient, power consumption is reduced as compared to conventional devices. Therefore, the searched device 2 can continuously operate for a long period (for example, three months or more), and the battery runs out until the user descends even if the user turns on the power in advance such as when entering the mountain. There is no worry. Furthermore, if the search target device 2 is turned on in advance, the search target device 2 can perform wireless communication with the search device 1 without further user operation, so that the user is in an avalanche or the like. Even if the user loses his or her mind, the search device 1 can specify the position of the search target device 2.

  In addition, since the search device 1 and the search target device 2 perform wireless communication using a frequency of 710 MHz or more and 960 MHz or less, the searchable device 2 has a long radio wave receivable distance from the search device 1. A wide range (for example, 100 m to 5 km) can be searched. If a higher frequency is used like 2.4 GHz of WLAN, the antenna becomes shorter and the receivable distance becomes shorter. In addition, when a higher frequency is used, the straightness of radio waves becomes stronger and the wraparound is reduced, so that the possibility of finding a victim in an environment where there is an obstacle is reduced. On the other hand, if a lower frequency is used, the antenna becomes longer and the device becomes larger.

  Further, by using the distance estimation method of the present embodiment, the search device 1 can accurately estimate the relative distance to the search target device 2 when the search target device 2 exists at a short distance. When the searched device 2 does not exist at a short distance, the relative distance to the searched device 2 can be estimated with a predetermined accuracy.

  Further, by using the antenna structure and switching control of the present embodiment, the circuit scale of the antenna portion can be reduced and the entire apparatus can be reduced in size and weight as compared with the case of using an array antenna. In the first antenna element 111 (radiator) that receives radio waves, switching for switching directivity is not performed, so that switching loss is minimized. Further, since the switching timing of the second switch 126 and the third switch 127 is the same, there is only one control system for switching the switch.

  Further, by providing the recess 16 at the center of the back surface 11f of the casing 11 of the search device 1 of the present embodiment, the user can press the button of the operation unit 13 with the first finger (thumb). When the search device 1 is held in the hand, the search device 1 can be stably held by placing the second finger (index finger) in the recess 16. Also, this way of holding can prevent the influence of the antenna directivity and stabilize the direction estimation accuracy because hands and fingers do not come around the antenna elements 111, 112, and 113.

  In addition, when the searched device 2 of the present embodiment receives radio waves from the searching device 1 or receives an instruction from the searching device 1, the LED 22 is caused to emit light and the sounding unit 204 outputs a notification sound. The user of the search device 1 can search the search target device 2 by his / her own visual or auditory sense.

  And according to this Embodiment, it can be anticipated by the above-mentioned effect that the possibility of finding a mountain victim or the like is further increased and the time until the discovery is further reduced.

  In the above embodiment, a case has been described in which the search target device 2 always transmits a call response signal when receiving the call signal from the search device 1 in the full search mode or the group search mode. The search target device 2 stores the identification information of the predetermined search device 1 in advance, and when the call signal from the search device 1 is received, the search target device 2 stores the call information in the stored identification information of the search device 1. The paging response signal may be transmitted only when there is a match with the identification information of the search device 1 included in the signal.

  Thereby, the search device 1 can display only the identification information of the searched device 2 in which the identification information of the own device is registered. In addition, since the number of times of transmitting the call response signal is relatively reduced, the searched device 2 can suppress power consumption.

  Moreover, although the said embodiment demonstrated the case where the information regarding the estimated distance and direction of the to-be-searched apparatus 2 was displayed on screens, such as LCD of the search apparatus 1, this invention is not limited to this, The search apparatus 1 Other display methods may be used such as providing a plurality of LEDs on the front surface of the housing 11 and changing the position of the LED to emit light according to the distance and direction of the search target device 2.

  Moreover, although the said embodiment demonstrated the case where the recessed part 16 was provided in the center part of the back surface 11f of the housing | casing 11 of the search device 1 in order to prevent affecting antenna directivity, this invention is not limited to this. However, it may be possible to prevent hands and fingers from coming around the antenna elements 111, 112, and 113 by other constituent values, such as providing a convex portion on the flat surface 11e side (upper end side) slightly from the center of the back surface 11f. good.

  The present invention is suitable for use in a search device for searching for the position of another communication device, and a communication system including a search device and a searched device.

DESCRIPTION OF SYMBOLS 1 Search apparatus 2 Searched apparatus 11, 21 Case 12 Display part 13 Operation part 14, 23 Power switch 15 Board | substrate 16 Recessed part 22 LED
101, 201 Antenna 102, 202 Radio section 103, 203 Control section 104, 204 Ring section 105, 205 Battery (power supply section)
111 First antenna element 112 Second antenna element 113 Third antenna element 121, 221 Transmitter 122, 222 Receiver 123, 223 Radio controller 124, 224 First clock 125, 225 First switch 126 Second switch 127 Third Switch 131,231 CPU
131a, 231a Signal generation unit 131b, 231b Signal acquisition unit 131c Distance estimation unit 131d Direction estimation unit 132, 232 Memory unit 133, 233 Second clock 134, 234 Third clock 135 Logic operation unit

Claims (19)

A portable housing;
An antenna housed in the housing for transmitting and receiving radio waves;
Transmitting means for transmitting a call signal to the searched device via the antenna;
Receiving means for receiving a response signal from the searched device corresponding to the calling signal via the antenna;
The response signal received by the receiving means is used to estimate the distance between the own device and the searched device and the direction of the searched device viewed from the own device, the identification information of the searched device, and the estimated Control means for displaying information about distance and direction;
A search device comprising: A display unit having a screen;
The control means includes
Display identification information of the searched device and information on the estimated distance and direction on the screen;
The search device according to claim 1. The transmission means wirelessly transmits the calling signal at a frequency of 710 MHz or more and 960 MHz or less,
The search device according to claim 1 or 2. The receiving means measures the received signal strength of the response signal;
The control means calculates a propagation delay time of a transmission path between the search target device and a first distance estimation method based on the received signal strength and the propagation delay time according to the magnitude of the received signal strength. Selecting any one of the second distance estimation methods based on, and estimating the distance between the own device and the searched device,
The search device according to any one of claims 1 to 3. The control means includes
When the received signal strength is greater than a predetermined threshold, the distance is estimated using the first distance estimation method, and when the received signal strength is equal to or less than the threshold, the distance is estimated using the second distance estimation method. ,
The search device according to claim 4. The control means includes
When the first distance estimation method was used last time and the received signal strength is greater than a first threshold value, the first distance estimation method is used to estimate the distance, and the first distance estimation method is less than or equal to the first threshold value. Estimating the distance using the second distance estimation method;
When the received signal strength is greater than a second threshold value that is greater than the first threshold value when the second distance estimation method is used last time, the first distance estimation method is used to estimate the distance. Estimating the distance using the second distance estimation method when the second threshold or less;
The search device according to claim 4. The antenna includes a first element connected to the transmitting means or the receiving means via a first switch, and a second element arranged substantially parallel to the first element and connected to the housing via a second switch. And a third element that is arranged on the opposite side of the second element with respect to the first element substantially parallel to the first element and is connected to the housing via a third switch,
The receiving means receives the response signal in each of a first state in which the second switch is connected and the third switch is cut off, and a second state in which the second switch is cut off and the third switch is connected. Measure the signal strength,
The control means estimates the direction of the searched device based on the magnitude relationship between the measured received signal strength in the first state and the received signal strength in the second state;
The search device according to any one of claims 1 to 3. A table in which a numerical value of a difference between the received signal strength in the first state and the received signal strength in the second state is divided into a plurality of ranges, and a representative value of the estimated direction of the searched device is associated with each range Store it in memory,
The control means includes
Displaying information indicating a representative value corresponding to a range including the measured received signal strength in the first state and the received signal strength in the second state on the screen as information on the estimated direction;
The search device according to claim 7. An operation button is disposed on the first end side of the first surface of the casing from the center of the casing,
The antenna is disposed on the second end side opposite to the first end from the center of the housing;
A concave portion or a convex portion is provided in the central portion or the side portion of the second surface that is the opposite surface of the first surface,
The search device according to any one of claims 1 to 8. A search device capable of communicating with a plurality of search target devices,
Transmitting means for transmitting a calling signal to the searched device;
Receiving means for receiving a response signal from the searched device corresponding to the calling signal;
Control means for generating the call signal, outputting the call signal to the transmission means, and displaying the identification information of the searched device carried on the response signal received by the reception means,
The control means selectively generates a call signal for transmitting a response signal to one searched device or a call signal for transmitting response signals to a plurality of searched devices based on a user instruction. And output to the transmission means,
Search device. When the user instructs one search target device as a search target,
The control means includes
Identification information of own device, identification information of search target device to be searched, information for requesting transmission of identification information to search target device, and timing information for instructing search target device of transmission timing of response signal Generating the paging signal including and outputting to the transmission means,
The receiving means includes
Receiving the response signal at a time including a transmission timing of the timing information;
The search device according to claim 10. When all search target devices are instructed as search targets by the user,
The control means includes
Generating the call signal including the identification information of the own device and information requesting transmission of identification information to all the devices to be searched, and outputting to the transmission means;
The receiving means includes
Receiving the response signal for a predetermined time after the call signal is transmitted;
The search device according to claim 10 or 11. When instructed by a user as a search target for a plurality of search target devices registered in advance,
The control means includes
Generating the call signal including the identification information of the own device and information requesting transmission of identification information to the plurality of devices registered in advance, and outputting the call signal to the transmission unit;
The receiving means includes
Receiving the response signal for a predetermined time after the call signal is transmitted;
The search device according to any one of claims 10 to 12. When instructed by the user to operate as a searched device,
The receiving means includes
Receiving the call signal from another search device;
The control means includes
Generating the response signal including the identification information of the own device and the identification information of the other search device and outputting the response signal to the transmission means;
The transmission means includes
Transmitting the response signal to the calling signal to the other search device;
The search device according to claim 10. A communication system comprising a portable search device and a portable search target device that performs wireless communication with the search device,
The search device includes:
First transmission means for transmitting a calling signal to the searched device;
First receiving means for receiving a response signal from the predetermined searched device;
The call signal is generated and output to the first transmission unit, and the response signal received by the first reception unit is used to determine the distance between the own device and the searched device and the searched device viewed from the own device. First control means for estimating a direction;
Comprising
The searched device is:
Second receiving means for receiving the call signal from the search device;
Second control means for generating the response signal upon receipt of the call signal;
Second transmission means for transmitting the response signal generated by the second control means;
Comprising
Communications system. The first transmission means transmits the call signal at a frequency of 710 MHz to 960 MHz,
The second transmission means transmits the response signal at a frequency of 710 MHz to 960 MHz.
The communication system according to claim 15. The first control means includes
The identification information of the search target device, and information on the estimated distance and direction are displayed on the screen.
The communication system according to claim 15 or claim 16. The second receiving means is activated at every first interval to receive the calling signal,
The second transmission means transmits the response signal every second interval,
The first interval is longer than the second interval;
The communication system according to any one of claims 15 to 17. The first transmission means transmits a response confirmation signal every time the response signal is received,
The second control means causes a light emitting element to emit light each time the response confirmation signal is received, or outputs a notification sound from a ringing unit,
The communication system according to any one of claims 15 to 18.

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