Patent Publication Number: US-2023144784-A1

Title: Operation device and operation system

Description:
TECHNICAL FIELD 
     The present disclosure relates to an operation device and an operation system. 
     BACKGROUND ART 
     There is known a conventional remote controller which has an operation unit including a plurality of buttons, a power generation unit, a power source management unit, a control unit, a storage unit, a switch, a wireless transmission unit, and an antenna (e.g., see PTL 1). 
     According to a remote controller described in PTL 1, a power generation unit has a plurality of power generation elements each generating power by use of energy generated in response to a press of a corresponding button. Note that examples of the power generation elements employed to constitute the power generation unit include power generation elements each generating power by a temporal change in magnetic flux using a spring, a permanent magnet, and an induction coil, and power generation elements each constituted by a piezoelectric element, a magnetostrictive material, a giant magnetostrictive material, or the like, and generating power by elastic deformation in response to a press of a button. 
     Each of the power source management unit, the control unit, and the storage unit operates by use of power generated by the power generation unit. 
     The power source management unit has a power accumulation element which accumulates power supplied from the power generation unit. The power source management unit is capable of outputting, to the control unit, an operation signal of a type associated with contents of a corresponding one of operations performed for the operation unit. 
     The control unit outputs contents of the operation signal received from the power source management unit to the storage unit. The control unit analyzes the operation signal received from the power source management unit and transmits information corresponding to the contents of the operation signal stored in the storage unit, such as a wireless signal containing contents themselves of the operation signal, by controlling the switch and the wireless transmission unit when the operation performed for the operation unit meets a predetermined condition. 
     The wireless transmission unit operates using power supplied from the power accumulation element via the switch turned on by the control unit, generates a wireless signal containing the information received from the control unit, and transmits the generated wireless signal to a receiver via the antenna. Note that the switch is turned off after the wireless transmission unit transmits the operation signal. 
     CITATION LIST 
     Patent Literature 
     
         
         [PTL 1] US/2016/110995 
       
    
     SUMMARY 
     Technical Problem 
     According to the remote controller described in PTL 1, each of the power source management unit, the control unit, the storage unit, and the wireless transmission unit operates using power generated in response to a press of the button. Accordingly, a period from the time of the press of the button to the time of transmission of the operation signal tends to increase. In other words, according to the remote controller described in PTL 1, a transmission delay of the operation signal from the press of the button is likely to be produced, regardless of an intention of the user or the like. From this viewpoint, the controller described above is considered to have a problem of low usability. 
     The present disclosure aims at solution of at least a part of the problems described above. One of objects to be achieved by the present disclosure is to provide an operation device and an operation system capable of improving usability. 
     Solution to Problem 
     An operation device according to a first aspect of the present disclosure includes an operation unit, a power generation element that generates power according to an operation of the operation unit, a battery that supplies power, and a communication unit that transmits an operation signal corresponding to the operation unit that has been operated, and the communication unit transmits the operation signal by use of power supplied from the battery, in a case where a residual quantity of the battery is a predetermined residual quantity or larger, and the communication unit transmits the operation signal by use of power generated by the power generation element, in a case where the residual quantity of the battery is smaller than the predetermined residual quantity. 
     An operation device according to a second aspect of the present disclosure includes an operation unit, a power generation element that generates power according to an operation of the operation unit, a battery that supplies power, a switching unit that switches an operation mode according to an operation performed by a user, and a communication unit that transmits an operation signal corresponding to the operation unit that has been operated. The communication unit transmits the operation signal by use of power accumulated in the battery, in a case where the operation mode is a first mode, and the communication unit transmits the operation signal by use of power generated by the power generation element, in a case where the operation mode is a second mode. 
     An operation device according to a third aspect of the present disclosure includes an operation unit, a power generation element that generates power according to an operation of the operation unit, a battery that supplies power, a power reception unit that receives power externally supplied, and a communication unit that transmits an operation signal corresponding to the operation unit that has been operated. In a case where power received by the power reception unit has a predetermined value or higher, the communication unit transmits the operation signal by use of the power supplied from the battery charged by power received by the power reception unit, and in a case where the power received by the power reception unit has a value lower than the predetermined value, the communication unit transmits the operation signal by use of the power generated by the power generation element. 
     An operation system according to a fourth aspect of the present disclosure includes an operation device that transmits an operation signal, and an electronic device that receives the operation signal and operates. The operation device includes an operation unit, a power generation element that generates power according to an operation of the operation unit, a battery that supplies power, and a transmission unit that transmits the operation signal corresponding to the operation unit that has been operated. The operation device operates in either one of a first mode where the transmission unit transmits the operation signal by use of power supplied from the battery and a second mode where the transmission unit transmits the operation signal by use of power generated by the power generation element. The operation signal contains information indicating an operation mode of the operation device. The electronic device includes a reception unit that receives the operation signal from the operation device, a mode determination unit that determines the operation mode of the operation device on the basis of the operation signal received by the reception unit, and a notification unit that gives a notification indicating the operation mode of the operation device, when the mode determination unit determines that the operation mode of the operation device has been switched from the first mode to the second mode. 
     An operation system according to a fifth aspect of the present disclosure includes an operation device that transmits an operation signal, an information processing device that receives the operation signal, and a server that communicates with the information processing device. The operation device includes an operation unit, a power generation element that generates power according to an operation of the operation unit, a battery that supplies power, and a transmission unit that transmits the operation signal corresponding to the operation unit that has been operated. The operation device operates in either one of a first mode where the transmission unit transmits the operation signal by use of power supplied from the battery and a second mode where the transmission unit transmits the operation signal by use of power generated by the power generation element. The operation signal contains information indicating an operation mode of the operation device. The information processing device transmits the operation signal received from the operation device to the server and receives a processing result obtained by the server from the server. The server includes a mode determination unit that determines the operation mode of the operation device on the basis of the operation signal received from the information processing device, and a notification unit that transmits, to the information processing device, the processing result to be given by the information processing device as a notification indicating the operation mode of the operation device, when the mode determination unit determines that the operation mode of the operation device has been switched from the first mode to the second mode. 
     The operation devices according to the first to third aspects described above, and the operation systems according to the fourth and fifth aspects described above are operation devices and operation systems capable of improving usability. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic diagram depicting a configuration of a game system according to a first embodiment. 
         FIG.  2    is a diagram depicting an external appearance of an operation device according to the first embodiment. 
         FIG.  3    is a block diagram depicting a configuration of a device body of the operation device according to the first embodiment. 
         FIG.  4    is a block diagram depicting a configuration of a game device according to the first embodiment. 
         FIG.  5    is a block diagram depicting function units included in a control unit according to the first embodiment. 
         FIG.  6    is a diagram depicting an example of a screen during execution displayed on a display device according to the first embodiment. 
         FIG.  7    is a diagram depicting an example of a screen during execution displayed on the display device according to the first embodiment. 
         FIG.  8    is a diagram depicting an example of a screen during execution displayed on the display device according to the first embodiment. 
         FIG.  9    is a diagram depicting an example of a screen during execution displayed on the display device according to the first embodiment. 
         FIG.  10    is a diagram depicting a modification of a screen during execution according to the first embodiment. 
         FIG.  11    is a block diagram depicting a configuration of a device body included in an operation device of a game system according to a second embodiment. 
         FIG.  12    is a diagram depicting an example of a screen during execution displayed on a display device according to the second embodiment. 
         FIG.  13    is a block diagram depicting a configuration of a device body included in an operation device of a game system according to a third embodiment. 
         FIG.  14    is a diagram depicting an example of a screen during execution displayed on a display device according to the third embodiment. 
         FIG.  15    is a schematic diagram depicting a configuration of a game system according to a fourth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     [First embodiment] A first embodiment of the present disclosure will hereinafter be described with reference to the drawings. 
       FIG.  1    is a schematic diagram depicting a configuration of a game system  1 A according to the present embodiment. 
     The game system  1 A according to the present embodiment corresponds to an operation system. As depicted in  FIG.  1   , the game system  1 A includes an operation device  2 A, a game device  4 , and a display device  6 . The game system  1 A is configured such that the game device  4  advances a game, and that the display device  6  displays a screen during execution of the game device  4 , such as a game screen, according to operation signals transmitted from the operation device  2 A. 
     Respective configurations of the game system  1 A will hereinafter be described. 
     [Configuration of Operation Device]  FIG.  2    is a diagram depicting an external appearance of the operation device  2 A. Specifically,  FIG.  2    is a front diagram depicting the operation device  2 A. 
     The operation device  2 A transmits an operation signal corresponding to an input operation input by a user to operate the game device  4 . For example, as depicted in  FIG.  2   , the operation device  2 A can constitute a control pad (controller) having an inverted U-shape as viewed from the front. The operation device  2 A depicted in  FIG.  2    by way of example has a housing  21 . 
     [Configuration of Housing] The housing  21  has a left holding portion  21 L, a right holding portion  21 R, a central portion  21 C, and a top portion  21 U. 
     The left holding portion  21 L is located at a left end portion of the housing  21  and held by the left hand of the user. The right holding portion  21 R is located at a right end portion of the housing  21  and held by the right hand of the user. 
     The central portion  21 C is provided between the left holding portion  21 L and the right holding portion  21 R. 
     The top portion  21 U is a surface located on the upper side as viewed from the user facing the central portion  21 C while holding the left holding portion  21 L by the left hand and the right holding portion  21 R by the right hand. 
     [Configuration of Device Body] The operation device  2 A includes a device body  22 A provided on the housing  21 . The device body  22 A has an operation unit  23  exposed to the outside of the housing  21 . 
     [Configuration of Operation Unit] The operation unit  23  includes one direction button  231 , four buttons  232 , two buttons  233 , and four buttons  234  ( 234 L and  234 R), and further a touch pad  235 , and two sticks  236  ( 236 L and  236 R). Each of the buttons  231  to  234  corresponds to an operator. 
     The direction button  231  is a button pressable in the up-down and left-right directions. The direction button  231  is disposed on the left holding portion  21 L. 
     The four buttons  232  are disposed on the right holding portion  21 R. 
     The two buttons  233  are provided on the left and right of the central portion  21 C, respectively. 
     The two buttons  234 L included in the four buttons  234  and provided at the left end of the top portion  21 U (the operation button on the depth side is not depicted in the figure) are disposed in a line in the depth direction. Similarly, the two buttons  234 R included in the four buttons  234  and provided at the right end of the top portion  21 U (the operation button on the depth side is not depicted in the figure) are disposed in a line in the depth direction. 
     The touch pad  235  is a two-point detection type touch pad. The touch pad  235  detects a touch operation performed by the user, and outputs a signal corresponding to the detected touch operation. The touch pad  235  is provided in the central portion  21 C at a position sandwiched between the two buttons  233  in such a manner as to be able to be inserted and protruded into the housing  21 . Accordingly, the touch pad  235  is one operator included in the operators. 
     The stick  236 L included in the two sticks  236  is disposed below and on the left of the touch pad  235 , while the stick  235 R is disposed on the lower side and the right side of the touch pad  235 . While not depicted in detail in the figure, each of the sticks  236 L and  236 R has a tiltable shaft member. Each of the sticks  236 L and  236 R detects a tilt direction of the shaft member tilted by the user, and outputs a signal indicating the detected tilt direction. 
     [Other Configurations of Device Body]  FIG.  3    is a block diagram depicting a configuration of the device body  22 A. 
     As depicted in  FIG.  3   , the device body  22 A includes, in addition to the operation unit  23 , a battery BT, a detection unit  24 , a power generation unit  25 , a charging unit  26 , a notification unit  27 , a vibration unit  28 , a communication unit  29 A, a storage unit  30 , and a control unit  31 A. 
     Note that the operation device  2 A operates in a first mode which uses power supplied from the battery BT, in a case where a residual quantity of the battery BT is a predetermined residual quantity or larger. The first mode can also be referred to as a battery power use mode. Note that the predetermined residual quantity can be defined as such a residual quantity sufficient for transmission of an operation signal from the operation device  2 A, for example. 
     On the other hand, in a case where the residual quantity of the battery BT is smaller than the predetermined residual quantity, the operation device  2 A operates in a second mode which uses power supplied from the power generation unit  25 . The second mode can also be referred to as a generated power use mode. 
     As described above, the operation device  2 A has operation modes including the first mode and the second mode. 
     [Configuration of Battery] The battery BT supplies accumulated power to the device body  22 A. According to the present embodiment, the battery BT is constituted by a secondary battery chargeable by the charging unit  26  described below. However, the battery BT may be constituted by a primary battery instead of this example. In addition, the battery BT may be provided in such a manner as to be attachable to and detachable from the housing  21 . 
     [Configuration of Detection Unit] The detection unit  24  operates using power supplied from the battery BT to detect a press of the corresponding one of the buttons. In other words, the detection unit  24  operates when the operation mode of the operation device  2 A is the first mode. 
     The detection unit  24  includes a plurality of detection elements  241  provided in correspondence with the buttons  231  to  234  and the touch pad  235  which are detection targets constituting the operation unit  23 . Each of the plurality of detection elements  241  detects a press of the corresponding detection target of the buttons  231  to  234  and the touch pad  235 . The detection element  241  having detected the press of the detection target outputs a signal containing identification information indicating the detection element  241  itself to a first control unit  311  included in the control unit  31 A and described below. 
     [Configuration of Power Generation Unit] The power generation unit  25  includes a plurality of power generation elements  251  disposed within the housing  21  in correspondence with the detection targets of the respective detection elements  241 . Specifically, the plurality of power generation elements  251  are provided within the housing  21  in correspondence with the buttons  231  to  234  and the touch pad  235 , which are detection targets provided in such a manner as to be able to be inserted and protruded into the housing  21 . 
     Each of the power generation elements  251  generates power in response to a press of the corresponding detection target and supplies the generated power to the charging unit  26  and a second control unit  312  included in the control unit  31 A and described below. Moreover, in a case where any of the detection targets is pressed, the corresponding power generation element  251  outputs a signal containing identification information indicating the pressed detection target to the second control unit  312 . In other words, supply of power from any one of the power generation elements  251  indicates a press of the detection target associated with the corresponding power generation element  251 . 
     [Configuration of Charging Unit] The charging unit  26  charges the battery BT with power supplied from the power generation elements  251 . 
     Here, at least a part of power generated by the power generation elements  251  is consumed for transmission of operation signals by using the second control unit  312  and a second communication unit  292  included in a communication unit  29 A and described below. Accordingly, the power used for charging the battery BT by the charging unit  26  corresponds to surplus power in the power generated by the power generation elements  251 . 
     Note that the charging unit  26  may be eliminated in a case where no surplus power remains in the generated power, for example. 
     [Configuration of Notification Unit] The notification unit  27  gives a notification of an operation state of the operation device  2 A. In other words, the notification unit  27  is a first notification unit which gives a notification of the operation state of the operation device  2 A by presenting a lighting state. Specifically, the notification unit  27  lights with power supplied from the battery BT when an input operation is performed for the operation unit  23  under control by the first control unit  311 . 
     In more detail, in a case where the residual quantity of the battery BT is the predetermined residual quantity or larger, i.e., in a case where the operation mode of the operation device  2 A is the first mode, the notification unit  27  lights in response to at least an input operation performed for the operation unit  23  under control by the first control unit  311 . 
     On the other hand, in a case where the residual quantity of the battery BT is smaller than the predetermined residual quantity, i.e., in a case where the operation mode of the operation device  2 A is the second mode, no power is supplied to the notification unit  27 . Accordingly, the notification unit  27  does not light even when an input operation is performed for the operation unit  23 . 
     The user can check which of the first mode and the second mode has been selected as the operation mode of the operation device  2 A on the basis of the lighting state of the notification unit  27  configured as above. 
     Note that the notification unit  27  may be configured to light in a first color with use of power supplied from the battery BT, in a case where the residual quantity of the battery BT is the predetermined residual quantity or larger, and light in a second color different from the first color with use of power supplied from the power generation elements  251 , in a case where the residual quantity of the battery BT is smaller than the predetermined residual quantity. In other words, the notification unit  27  may be configured to light in the first color with use of power of the battery BT, in a case where the operation mode of the operation device  2 A is the first mode, and light in the second color with use of power of the power generation elements  251 , in a case where the operation mode of the operation device  2 A is the second mode. 
     Moreover, in a case where the residual quantity of the battery BT is the predetermined residual quantity or larger, the notification unit  27  may constantly light as long as the power source of the operation device  2 A is kept turned on. 
     The notification  27  thus configured may be constituted by an indicator including a solid state light source such as an LED (Light Emitting Diode). However, the notification unit  27  is not limited to the unit of this example, but may be a unit which outputs sound corresponding to an input operation performed for the operation unit  23 , in a case where the residual quantity of the battery BT is the predetermined residual quantity or larger, and does not output sound, in a case where the residual quantity of the battery BT is smaller than the predetermined residual quantity even when an input operation is input to the operation unit  23 . 
     [Configuration of Vibration Unit] The vibration unit  28  is a unit which generates vibration, and may be constituted by a motor, for example. 
     The vibration unit  28  generates vibration in a case where the operation unit  23  is operated. In this manner, the user is notified of the fact that the operation unit  23  has been operated. Accordingly, the vibration unit  28  can be considered as a second notification unit which gives a notification of an operation state of the operation device  2 A. According to the present embodiment, the vibration unit  28  vibrates with use of power supplied from the battery BT under control by the first control unit  311 , in a case where the operation mode of the operation device  2 A is the first mode. However, the vibration unit  28  is not limited to the unit of this example but may be a unit configured to vibrate with use of power supplied from the power generation elements  251  under control by the second control unit  312 , in a case where the operation mode of the operation device  2 A is the second mode. 
     Moreover, in a case where the communication unit  29 A receives a vibration generation signal, which is a signal for generating vibration, from the game device  4 , the vibration unit  28  generates vibration under control by the first control unit  311  or the second control unit  312 . 
     Note that the vibration unit  28  is not an essential constituent element. 
     [Configuration of Communication Unit] The communication unit  29 A corresponds to a transmission unit which transmits an operation signal to the game device  4  under control by the control unit  31 A, as an operation signal corresponding to an input operation performed by the user for the operation unit  23 . The communication unit  29 A includes a first communication unit  291  and the second communication unit  292 . 
     Each of the first communication unit  291  and the second communication unit  292  wirelessly transmits an operation signal in conformity with near field wireless communication standards such as Bluetooth (registered trademark). However, each of the first communication unit  291  and the second communication unit  292  may be configured to wirelessly transmit an operation signal in conformity with other wireless communication standards such as ZigBee (registered trademark). 
     The first communication unit  291  transmits an operation signal input from the first control unit  311  by using power supplied from the battery BT. The operation signal transmitted by the first communication unit  291  contains information indicating that the operation mode of the operation device  2 A is the first mode. For example, the operation signal transmitted by the first communication unit  291  contains information indicating that the operation signal is an operation signal transmitted by the first communication unit  291 . 
     The second communication unit  292  transmits an operation signal input from the second control unit  312  by using power supplied from the power generation elements  251 . The operation signal transmitted by the second communication unit  292  contains information indicating that the operation mode of the operation device  2 A is the second mode. For example, the operation signal transmitted by the second communication unit  292  contains information indicating that the operation signal is an operation signal transmitted by the second communication unit  292 . 
     [Configuration of Storage Unit] The storage unit  30  stores various types of data necessary for performing operations of the operation device  2 A. For example, the storage unit  30  stores a correspondence between the detection targets described above and respective pieces of identification information indicating the detection targets. 
     [Configuration of Control Unit] The control unit  31 A controls operations of the operation device  2 A. For example, the control unit  31 A controls the charging unit  26 , the notification unit  27 , the vibration unit  28 , the communication unit  29 A, and the storage unit  30 . The control unit  31 A includes the first control unit  311 , the second control unit  312 , and a charging control unit  313 . 
     [Configuration of First Control Unit] The first control unit  311  operates with power supplied from the battery BT to control the operation device  2 A, in a case where the residual quantity of the battery BT is the predetermined residual quantity or larger, i.e., in a case where the operation device  2 A operates in the first mode. Specifically, the first control unit  311  controls the notification unit  27 , the vibration unit  28 , and the first communication unit  291 . 
     For example, when the operation unit  23  is operated, the first control unit  311  causes the notification  27  to give a notification that the operation unit  23  has been operated. Specifically, when a signal is input from any one of the detection elements  241 , the touch pad  235 , and the sticks  236 , the first control unit  311  causes the notification unit  27  to give a notification that the operation unit  23  has been operated. 
     Moreover, for example, the first control unit  311  causes the first communication unit  291  to transmit an operation signal corresponding to an input operation performed by the user for the operation unit  23 . Specifically, in a case where a signal is input from any one of the detection elements  241  in response to a press of the corresponding detection target, the first control unit  311  specifies the detection target corresponding to identification information contained in the input signal with reference to the storage unit  30 , and causes the first communication unit  291  to transmit an operation signal indicating that the specified detection target has been operated. 
     Moreover, when a signal is input from any one of the touch pad  235  and the sticks  236 , the first control unit  311  causes the first communication unit  291  to transmit an operation signal corresponding to the input signal. 
     Note that the first control unit  311  regulates transmission of an operation signal from the second control unit  312  to the second communication unit  292  in a case where the first control unit  311  causes the first communication unit  291  to transmit an operation signal. For example, the first control unit  311  causes the first communication unit  291  to transmit an operation signal, and outputs a regulation signal to the second control unit  312  to regulate transmission of an operation signal from the second communication unit  292 . Accordingly, the first control unit  311  has a function of a transmission regulation unit. 
     In addition, the first control unit  311  specifies the residual quantity of the battery BT on the basis of power (particularly voltage) supplied from the battery BT and causes the first communication unit  291  to transmit a residual quantity notification signal for notification of the residual quantity of the battery BT at timing immediately before the residual quantity of the battery BT becomes smaller than the predetermined residual quantity. In this manner, the game device  4  is allowed to recognize a state that the operation mode of the operation device  2 A will be switched from the first mode to the second mode in a short time due to a small residual quantity of the battery BT. 
     Note that the first control unit  311  may periodically causes the first communication unit  291  to transmit the residual quantity notification signal. 
     [Configuration of Second Control Unit] The second control unit  312  is started by power supplied from the power generation elements  251  to control the operation device  2 A, in a case where the residual quantity of the battery BT is smaller than the predetermined residual quantity, i.e., in a case where the operation device  2 A operates in the second mode. The second control unit  312  controls the second communication unit  292 , for example. 
     In a case where a signal is input from the corresponding power generation element  251  in response to a press of at least one of the detection targets, the second control unit  312  specifies the detection target corresponding to identification information contained in the input signal with reference to the storage unit  30 , and causes the second communication unit  292  to transmit an operation signal indicating that the specified detection target has been operated. 
     As described above, in a case where the operation mode of the operation device  2 A is the second mode for performing operation with use of power supplied from the power generation unit  25 , neither the first control unit  311  nor the first communication unit  291  is allowed to function. Accordingly, an operation signal corresponding to a press of the detection target associated with the corresponding power generation element  251  is transmitted only from the second communication unit  292 . On the other hand, in a case where the operation mode of the operation device  2 A is the second mode, no operation signal corresponding to either a touch operation performed for the touch pad  235 , or a tilt operation performed for one of the sticks  236  is transmitted from the operation device  2 A. In this manner, in a case where the operation device  2 A operates in the second mode, a limitation is imposed on an input operation performed for the operation device  2 A, such as a limitation to the operable operators. 
     As described above, the second control unit  312  is started by power supplied from the power generation elements  251 . Accordingly, even in a state where the residual quantity of the battery BT is the predetermined residual quantity or larger and sufficient for transmission of an operation signal from the first communication unit  291 , the second control unit  312  is started by power supplied from the power generation elements  251  and causes the second communication unit  292  to transmit an operation signal. In this case, there is a possibility that an operation signal is transmitted from each of the first communication unit  291  and the second communication unit  292  in response to an input operation performed for an identical detection target. 
     However, when the first control unit  311  causes the first communication unit  291  to transmit an operation signal, the first control unit  311  outputs a regulation signal to the second control unit  312  as described above. In this case, the second control unit  312  regulates transmission of an operation signal from the second communication unit  292  to prevent transmission of an operation signal from each of the first communication unit  291  and the second communication unit  292 . 
     Each of the first control unit  311  and the first communication unit  291  operates with power supplied from the battery BT. On the other hand, in a case where the operation device  2 A operates in the second mode, each of the second control unit  312  and the second communication unit  292  operates with power supplied from the power generation elements  251 . Accordingly, assuming that a period from press timing of the detection target to transmission timing of the operation signal is defined as a transmission completion period, a longer transmission completion period is likely to be required in the second mode than that in the first mode. 
     For coping with this situation, the notification unit  27  gives a notification indicating the operation mode of the operation device  2 A. Moreover, as will be described in detail below, the game device  4  determines the operation mode of the operation device  2 A on the basis of an operation signal received from the operation device  2 A and notifies the user of the determined operation mode of the operation device  2 A. 
     In this manner, the user is allowed to recognize the current operation mode of the operation device  2 A, and switch between the use of the operation device  2 A in the first mode and the use of the operation device  2 A in the second mode according to situations. 
     [Configuration of Charging Control Unit] The charging control unit  313  controls charging by the charging unit  26  for the battery BT. Specifically, the charging control unit  313  specifies the residual quantity of the battery BT on the basis of power (particularly voltage) supplied from the battery BT and regulates charging by the charging unit  26  for the battery BT, in a case where the residual quantity of the battery BT is full. 
     [Configuration of Game Device]  FIG.  4    is a block diagram depicting a configuration of the game device  4 . 
     The game device  4  corresponds to an electronic device. As described above, the game device  4  executes and advances a game according to operation signals received from the operation device  2 A, and also displays a screen during execution of the game on the display device  6 . 
     As depicted in  FIG.  4   , the game device  4  includes a communication unit  41 , a storage unit  42 , a memory  43 , and a control unit  44 . The communication unit  41 , the storage unit  42 , the memory  43 , and the control unit  44  are connected by a bus line BL in such a manner as to be communicable with each other. 
     [Configuration of Communication Unit] Under control by the control unit  44 , the communication unit  41  communicates with the operation device  2 A, and further communicates with a server SVA, which is an external device, via a network N. 
     For example, the communication unit  41  receives an operation signal and a residual quantity notification signal transmitted from the operation device  2 A, and outputs the received operation signal and the received residual quantity notification signal to the control unit  44 . Accordingly, the communication unit  41  corresponds to a reception unit included in the game device  4 . 
     For example, the communication unit  41  transmits a vibration generation signal to the operation device  2 A according to a state of progress of the game. Moreover, for example, the communication unit  41  communicates with the server SVA to acquire necessary information from the server SVA. 
     [Configurations of Storage Unit and Memory] The storage unit  42  stores programs and data necessary for performing operations of the game device  4 . For example, the storage unit  42  stores an OS (operating System) for controlling the game device  4 . Moreover, for example, the storage unit  42  stores pairing information indicating paring with the operation device  2 A. According to the present embodiment, the game device  4  is configured to execute games. Therefore, the storage unit  42  can store game programs. In addition, in a case where the game device  4  has an optical drive, game programs may be recorded in an optical disk readable by the optical drive. 
     The memory  43  is a work memory of the control unit  44 . The memory  43  temporarily stores programs and data read from the storage unit  42  or an optical disk. 
     [Configuration of Control Unit]  FIG.  5    is a block diagram depicting function units included in the control unit  44 . 
     The control unit  44  includes an arithmetic processing device such as a CPU (Central Processing Unit), and controls operations of the game device  4 . 
     As depicted in  FIG.  5   , the control unit  44  has an execution unit  441 , an information acquisition unit  442 , a mode determination unit  443 , a handleability determination unit  444 , and a display control unit  445 . 
     The execution unit  441  reads and executes an OS and a game program from the storage unit  42  and advances a game according to operation signals received from the operation device  2 A. 
     The information acquisition unit  442  communicates with the server SVA via the communication unit  41 , and acquires information associated with the game currently executed. For example, the information acquisition unit  442  acquires, from the server SVA, information indicating a category of the game currently executed, or information indicating whether or not the game executable by the execution unit  441  is handleable in the second mode of the operation device  2 A. The information acquisition unit  442  stores information acquired from the server SVA in the storage unit  42 . 
     The mode determination unit  443  determines which of the first mode and the second mode has been selected as the operation mode of the operation device  2 A on the basis of an operation signal received by the communication unit  41  from the operation device  2 A. Specifically, in a case where the operation signal is determined to be a signal transmitted from the first communication unit  291  on the basis of information contained in the received operation signal, the mode determination unit  443  determines that the operation mode of the operation device  2 A is the first mode. On the other hand, in a case where the operation signal is determined to be a signal transmitted from the second communication unit  292  on the basis of information contained in the received operation signal, the mode determination unit  443  determines that the operation mode of the operation device  2 A is the second mode. 
     In a case where the mode determination unit  443  determines that the operation mode of the operation device  2 A is the second mode, the handleability determination unit  444  determines whether or not the game currently executed is handleable in the second mode of the operation device  2 A. 
     Here, a game requiring only low immediate responsiveness, i.e., a game allowed to be advanced even in a relatively long transmission completion period, is also allowed to be advanced by the operation device  2 A in the second mode of the operation mode. Examples of this game category include an adventure game and a simulation game. 
     On the other hand, a game requiring highly immediate responsiveness, i.e., a game which may cause a problem in progress of the game if a relatively long transmission completion period is needed, the game is not easily advanced by the operation device  2 A in the state where the operation mode is the second mode, i.e., the operation device  2 A which is likely to require a long transmission completion period. Examples of this game category include a shooting game and an action game. 
     Accordingly, in a case where information indicating the category of the game currently executed is acquired from the server SVA, for example, the handleability determination unit  444  determines whether or not the category of the game currently executed is handleable in the second mode of the operation device  2 A on the basis of the acquired information. 
     In a case where the category of the game currently executed is handleable in the second mode of the operation device  2 A, the handleability determination unit  444  determines that the game currently executed is advanceable by the operation device  2 A in the second mode of the operation mode. In a case where the category is not handleable, the handleability determination unit  444  determines that the game currently executed is difficult to advance by the operation device  2 A in the second mode of the operation mode. Accordingly, the category handleable in the second mode is defined as a category of such a game advanceable without causing any particular problem even by the operation device  2 A operating in the second mode. 
     Moreover, in a case where information indicating whether or not the game currently executed is handleable in the second mode of the operation device  2 A is acquired from the server SVA, for example, the handleability determination unit  444  determines whether or not the game currently executed is handleable in the second mode of the operation device  2 A on the basis of this information. In a case where the game currently executed is handleable in the second mode of the operation device  2 A, the handleability determination unit  444  determines that the game currently executed is advanceable by the operation device  2 A in the second mode of the operation mode. In a case where the game is not handleable, the handleability determination unit  444  determines that the game currently executed is difficult to advance by the operation device  2 A in the second mode of the operation mode. Accordingly, the game handleable in the second mode is defined as such a game advanceable without causing any particular problem even by the operation device  2 A operating in the second mode. 
       FIGS.  6  and  7    are diagrams depicting screens during execution P 1  and P 2 , respectively, which are examples of a screen displayed on the display device  6  by the display control unit  445 . 
     The display control unit  445  generates a screen during execution of the game executed by the execution unit  441  and displays the screen during execution on the display device  6 . 
     For example, when the mode determination unit  443  determines that the operation mode of the operation device  2 A has been switched to the second mode, the display control unit  445  displays, on the display device  6 , a message that the operation mode of the operation device  2 A has been switched to the second mode (generated power use mode), as in the screen during execution P 1  depicted in  FIG.  6   . 
     At this time, in a case where the handleability determination unit  444  determines that the game currently executed is not handleable in the second mode of the operation device  2 A, the display control unit  445  displays, on the display device  6 , a message that the operation mode of the operation device  2 A has been switched to the second mode (generated power use mode), and that the game currently executed is not handleable in the second mode of the operation device  2 A, as in the screen P 2  during execution depicted in  FIG.  7   . 
     Accordingly, the display control unit  445  has a function of a notification unit. 
       FIGS.  8  and  9    are diagrams depicting screens during execution P 3  and P 4 , respectively, which are examples of a screen displayed on the display device  6  by the display control unit  445 . 
     Note that the display control unit  445  may display a screen during execution for indicating switching of the operation mode of the operation device  2 A in response to a residual quantity notification signal received from the operation device  2 A. 
     For example, in a case of determination that the residual quantity of the battery BT is a value close to the predetermined residual quantity, i.e., the operation mode of the operation device  2 A is in a state immediately before switching from the first mode to the second mode on the basis of the residual quantity notification signal, the display control unit  445  may display a message that the operation mode of the operation device  2 A is to be switched to the second mode on the display device  6 , as in the screen during execution P 3  depicted in  FIG.  8   . 
     At this time, in a case where the handleability determination unit  444  determines that the game currently executed is not handleable in the second mode of the operation device  2 A, the display control unit  445  may display, on the display device  6 , a message that the operation mode of the operation device  2 A is to be switched to the second mode, and that the game currently executed is not handleable in the second mode of the operation device  2 A, as in the screen P 2  during execution depicted in  FIG.  9   . 
     Note that the message presenting the above contents is displayed while overlapped on the game screen. Accordingly, the game is temporarily interrupted at the time of display of the screens during execution P 1  to P 4 . The game is restarted when a predetermined operation, such as an operation of pressing an “OK” button, is performed for any of the screens P 1  to P 4  during execution. 
       FIG.  10    is a diagram depicting a screen during execution P 1 A which is a modification of the screen during execution P 1 . 
     Meanwhile, the message having the above contents may be displayed in a manner not interrupting the game. 
     For example, the screen during execution P 1 A depicted in  FIG.  10    may be displayed instead of the screen during execution P 1  depicted in  FIG.  6   . The screen during execution P 1 A includes a screen region R 1  where the game screen in the screen during execution P 1  is displayed, and a message region R 2  where a message is displayed. The screen region R 1  in the screen during execution P 1 A is displayed with reduction to a size smaller than the game screen in the screen during execution P 1 . The message region R 2  is disposed at a position not overlapping with the screen region R 1 . In addition, in a case where a message has a relatively large number of characters in the message region R 2  which has a small size, the full sentences of the message may be presented by scrolling the contents of the message, for example. Moreover, the position of the message region R 2  in the screen during execution P 1 A is not limited to the position on the upper side with respect to the screen region R 1  but may be a position on any one of the lower side, the right side, and the left side. 
     Furthermore, a message through which the game screen is transmittable to such a level that the game screen is recognizable may be displayed in each of the screens during execution P 1  to P 4  so as not to interrupt the game currently executed. At this time, a message may be superimposed on the game screen, and displayed by scrolling the contents of the message, for example. 
     Note that the display control unit  445  has a function of a notification unit in the present embodiment described above. However, this example is not required to be adopted. The configuration of the game device  4  may include such a notification unit which gives a notification of various types of information by use of sound or lighting of an indicator or the like. 
     [Advantageous Effects of First Embodiment] The game system  1 A according to the present embodiment described above can offer the following advantageous effects. 
     The operation device  2 A includes the operation unit  23  containing the buttons  231  to  234  and the touch pad  235 , the power generation elements  251  each generating power according to an operation performed for the operation unit  23 , the battery BT supplying power, and the communication unit  29 A transmitting an operation signal corresponding to the operation unit  23  having been operated. By using the first communication unit  291  and the second communication unit  292 , the communication unit  29 A transmits an operation signal with power supplied from the battery BT, in a case where the residual quantity of the battery BT is a predetermined residual quantity or larger, and transmits an operation signal with power generated by the power generation elements  251 , in a case where the residual quantity of the battery BT is smaller than the predetermined residual quantity. 
     This configuration achieves transmission of an operation signal by use of power supplied from the battery BT, in a case where the residual quantity of the battery BT is the predetermined residual quantity or larger. Accordingly, transmission of an operation signal is achievable without delay. On the other hand, in a case where the residual quantity of the battery BT is smaller than the predetermined residual quantity, a transmission delay of an operation signal may be produced. However, the operation device  2 A does not become disabled. Accordingly, usability of the operation device  2 A improves. 
     The operation device  2 A includes the notification unit  27  which gives a notification of an operation state of the operation device  2 A by presenting a lighting state. The notification unit  27  lights to give a notification that the communication unit  29 A transmits an operation signal by use of power supplied from the battery BT. In addition, the notification unit  27  does not light to give a notification that the communication unit  29 A transmits an operation signal by use of power generated by the power generation elements  251 . 
     Alternatively, the notification unit  27  lights in a first color to give a notification that the communication unit  29 A transmits an operation signal by use of power supplied from the battery BT. In addition, the notification unit  27  lights in a second color different from the first color to give a notification that the communication unit  29 A transmits an operation signal by use of power generated by the power generation elements  251 . 
     This configuration allows the user to check whether the operation mode of the operation device  2 A is the first mode which transmits an operation signal by use of power of the battery BT, or the second mode which transmits an operation signal by use of power generated by the power generation elements  251  on the basis of the lighting state of the notification unit  27 . Accordingly, usability of the operation device  2 A further improves. 
     The communication unit  29 A includes the first communication unit  291  which transmits an operation signal by use of power supplied from the battery BT, and the second communication unit  292  which transmits an operation signal by use of power generated by the power generation elements  251 . The operation signal contains information indicating whether the operation signal has been transmitted by power supplied from the battery BT or transmitted by power supplied from the power generation elements  251 . In other words, the operation signal contains information indicating whether the operation signal is an operation signal transmitted from the first communication unit  291 , or an operation signal transmitted from the second communication unit  292 . Accordingly, the operation signal contains information indicating the current operation mode of the operation device  2 A. 
     This configuration allows the game device  4 , which is a reception device for receiving an operation signal from the operation device  2 A, to recognize the state of the operation device  2 A, i.e., the operation mode of the operation device  2 A. 
     According to the operation device  2 A, the first control unit  311  functions as a transmission regulation unit, and outputs a regulation signal to the second control unit  312  to regulate transmission of an operation signal from the second communication unit  292  in a case where the first communication unit  291  transmits an operation signal. 
     This configuration can prevent transmission of an operation signal from each of the first communication unit  291  and the second communication unit  292  in response to an operation performed for the same operator of the operation unit  23 . 
     The operation device  2 A includes the charging unit  26  which charges the battery BT using power generated by the power generation elements  251 . 
     This configuration allows charging of the battery BT while using the operation device  2 A. Accordingly, usability of the operation device  2 A further improves. 
     The operation device  2 A includes the vibration unit  28  which generates vibration at the time of transmission of an operation signal. 
     This configuration can notify the user of the fact that an operation signal has been transmitted in response to an operation. Accordingly, usability of the operation device  2 A further improves. 
     The operation device  2 A includes the housing  21 , and the touch pad  235  provided in such a manner as to be able to be inserted or protruded into the housing  21 . The operation unit  23  includes the touch pad  235 . 
     This configuration achieves transmission of an operation signal by an operation of the touch pad  235  in a manner of a button. Accordingly, general versatility of the operation device  2 A improves. 
     The game system  1 A as an operation system includes the operation device  2 A transmitting an operation signal, and the game device  4  functioning as an electronic device which operates by receiving the operation signal from the operation device  2 A. 
     The operation device  2 A includes the operation unit  23 , the power generation elements  251  generating power according to an operation performed for the operation unit  23 , the battery BT supplying power, and the communication unit  29 A functioning as a transmission unit which transmits an operation signal corresponding to the operation unit  23  having been operated. The operation device  2 A operates in either the first mode where the communication unit  29 A transmits an operation signal by use of power supplied from the battery BT, or the second mode where the communication unit  29 A transmits an operation signal by use of power generated by the power generation elements  251 . The operation signal contains information indicating the operation mode of the operation device  2 A. 
     The game device  4  includes the communication unit  41  functioning as a reception unit, the mode determination unit  443 , and the display control unit  445  functioning as a notification unit. The communication unit  41  receives an operation signal from the operation device  2 A. The mode determination unit  443  determines the operation mode of the operation device  2 A on the basis of an operation signal received by the communication unit  41 . The display control unit  445  gives a notification indicating the operation mode of the operation device  2 A when the mode determination unit  443  determines that the operation mode of the operation device  2 A has been switched from the first mode to the second mode. 
     According to this configuration, the game device  4  gives a notification indicating the operation mode of the operation device  2 A using the display control unit  445  when the operation mode of the operation device  2 A is switched to the second mode which may produce a transmission delay of an operation signal from the time of the operation performed by the user. In other words, the display control unit  445  gives a notification that the operation mode of the operation device  2 A has been switched to the second mode. This configuration can notify the user of switching to the second mode when the operation mode of the operation device  2 A is switched to the second mode to deal with a smaller residual quantity of the battery BT than the predetermined residual quantity. Accordingly, usability of the game system  1 A as an operation system improves. 
     The game device  4  for executing games includes the handleability determination unit  444  which determines whether or not a game is handleable in the second mode when the mode determination unit  443  determines that the operation mode of the operation device  2 A is the second mode. The display control unit  445  functioning as a notification unit gives a notification that the game is not handleable in the second mode, when the handleability determination unit  444  determines that the game is not handleable in the second mode. 
     According to this configuration, the game device  4  can notify the user of the fact that the game currently executed is not handleable in the second mode when the operation mode of the operation device  2 A is switched to the second mode. Accordingly, usability of the game system  1 A further improves. 
     Here, a simulation game or a command selective system role playing game can advance the game even if a period from an operation by a user to transmission of an operation signal is relatively long. Accordingly, games in these categories are allowed to proceed even with long latency. On the other hand, games such as a shooting game and an action game are difficult to advance if transmission of an operation signal is delayed from an operation by a user. Accordingly, games in these categories may cause a problem in progress of the games if latency is long. 
     For coping with this situation, the handleability determination unit  444  determines that the game currently executed is not handleable in the second mode on the basis of information acquired from the server SVA in a case of determination that the category of the game executed is a predetermined category such as an action game. 
     This configuration allows the user to easily carry out operations such as charging of the battery BT. 
     The handleability determination unit  444  determines whether or not the game currently executed is handleable in the second mode, on the basis of information associated with the game. 
     This configuration can determine whether or not the game currently executed is handleable in the second mode. 
     [Second Embodiment] A second embodiment of the present disclosure will subsequently be described. 
     A game system according to the present embodiment has a configuration similar to the configuration of the game system  1 A of the first embodiment. Note herein that the operation device  2 A of the first embodiment automatically switches the operation mode from one of the first mode and the second mode to the other mode according to the residual quantity of the battery BT. Specifically, the operation device  2 A is configured to operate in the first mode when the residual quantity of the battery BT is the predetermined residual quantity or larger. However, the operation device  2 A is configured to stop power supply from the battery BT and automatically switch the operation mode to the second mode when the residual quantity of the battery BT becomes smaller than the predetermined residual quantity. On the other hand, according to the game system of the present embodiment, the user can manually switch the operation mode of the operation device. The game system of the present embodiment is different from the game system  1 A of the first embodiment in this point. 
     Note that parts presented in the following description and identical or substantially identical to the corresponding parts already described are given identical reference signs to omit the same description. 
     [General Configuration of Game System]  FIG.  11    is a block diagram depicting a configuration of an operation device  2 B. 
     The game system according to the present embodiment corresponds to an operation system. The game system according to the present embodiment has configurations and functions similar to those of the game system  1 A of the first embodiment except for a point that the operation device  2 B depicted in  FIG.  11    is provided instead of the operation device  2 A. Specifically, the game system according to the present embodiment includes the operation device  2 B, the game device  4 , and the display device  6 . The game system of the present embodiment operates in manners similar to the manners of the game system  1 A. Specifically, the operation device  2 B transmits an operation signal corresponding to an input operation input by the user. The game device  4  advances a game according to the operation signal. The display device  6  displays a screen during execution of the game. 
     Respective configurations of the game system according to the present embodiment will hereinafter be described. 
     [Configuration of Operation Device] By using the first communication unit  291  or the second communication unit  292 , the operation device  2 B transmits an operation signal corresponding to an input operation input by the user similarly to the operation device  2 A. 
     The operation device  2 B is configured not only to switch the operation mode according to the residual quantity of the battery BT, but also to switch the operation mode according to an operation performed by the user when the residual quantity of the battery BT is the predetermined residual quantity or larger. 
     The operation device  2 B includes the housing  21  and a device body  22 B. 
     As depicted in  FIG.  11   , the device body  22 B has configurations and functions similar to those of the device body  22 A except for points that a control unit  31 B is provided instead of the control unit  31 A, and that a switching unit  32  is further provided. Specifically, the device body  22 B includes the operation unit  23 , the detection unit  24 , the power generation unit  25 , the charging unit  26 , the notification unit  27 , the vibration unit  28 , the communication unit  29 A, the storage unit  30 , the control unit  31 B, and the switching unit  32 . 
     [Configuration of Switching Unit] The switching unit  32  is a unit operated by the user at the time of switching of the operation mode of the operation device  2 B. When the switching unit  32  is operated, the switching unit  32  outputs a switching signal corresponding to the operation to the control unit  31 B by use of power of the battery BT. Accordingly, in a case where the residual quantity of the battery BT is smaller than the predetermined residual quantity, the switching unit  32  is unable to transmit a switching signal even in a case where the user operates the switching unit  32  to switch to the first mode. Accordingly, the operation for switching the operation mode of the operation device  2 B to the first mode is cancelled in a case where the residual quantity of the battery BT is smaller than the predetermined residual quantity. 
     Note that the switching unit  32  presented by way of example may include a button, and an output circuit which outputs a switching signal for switching between the first mode and the second mode to the control unit  31 B every time the button is pressed. Alternatively, the switching unit  32  presented by way of example may include a switch, and an output circuit which outputs a switching signal for switching to the first mode to the control unit  31 B in response to sliding of the switch to one side, and outputs a switching signal for switching to the second mode to the control unit  31 B in response to sliding of the switch to the other side. 
     [Configuration of Control Unit] The control unit  31 B controls operations of the operation device  2 B similarly to the control unit  31 A. The control unit  31 B includes a mode switching unit  314  in addition to the first control unit  311 , the second control unit  312 , and the charging control unit  313 . 
     The mode switching unit  314  switches the operation mode of the operation device  2 B according to a switching signal input from the switching unit  32 . 
     Specifically, in a case where the user operates the switching unit  32  to switch the operation mode of the operation device  2 B to the first mode, the mode switching unit  314  actuates the first control unit  311  and regulates the operation of the second control unit  312  according to a switching signal input from the switching unit  32 . In this manner, the mode switching unit  314  sets the operation mode of the operation device  2 B to the first mode. 
     On the other hand, in a case where the user operates the switching unit  32  to switch the operation mode of the operation device  2 B to the second mode, the mode switching unit  314  regulates the operation of the first control unit  311  and actuates the second control unit  312  according to a switching signal input from the switching unit  32 . In this manner, the mode switching unit  314  sets the operation mode of the operation device  2 B to the second mode. 
     [Configuration of Game Device] Also in the game system of the present embodiment, the game device  4  similarly advances a game according to operation signals received from the operation device  2 B and displays a screen during execution of the game on the display device  6 . 
     Note herein that the operation mode of the operation device  2 B can be switched to the second mode not only in the case where the residual quantity of the battery BT becomes smaller than the predetermined quantity, but also according to an operation performed by the user. 
     According to the game device  4  of the present embodiment, therefore, when the mode determination unit  443  determines that the operation mode of the operation device  2 B is the second mode on the basis of an operation signal received from the operation device  2 B, the display control unit  445  gives a notification that the operation mode of the operation device  2 B has been switched from the first mode (battery power use mode) to the second mode (generated power use mode) by displaying a message on the screen during execution, for example. 
       FIG.  12    is a diagram depicting a screen during execution P 5  as an example of a screen during execution displayed by the game device  4 . 
     When the mode determination unit  443  determines that the operation mode of the operation device  2 B is the second mode, the handleability determination unit  444  determines whether or not the game currently executed is handleable in the second mode of the operation device  2 B on the basis of information acquired from the server SVA. Thereafter, in a case where the handleability determination unit  444  determines that the game currently executed is not handleable in the second mode, the display control unit  445  having a function of a notification unit gives a notification that the game currently executed is not handleable in the second mode (generated power use mode) of the operation device  2 B in addition to the fact that the operation mode of the operation device  2 B has been switched to the second mode by displaying the screen P 5  during execution depicted in  FIG.  12   , for example. 
     Note that the message displayed in the screen during execution P 5  may be displayed in a manner not to interrupt the game currently executed, similarly to the screens during execution P 1  to P 4 . For example, similarly to the screen during execution P 1 A, a message representing that the operation mode of the operation device  2 B has been switched to the second mode, and that the game currently executed is not handleable in the second mode may be displayed in the message region R 2  not overlapping with the screen region R 1 . Moreover, for example, a message transmittable to such a level that the game screen is observable may be superimposed and displayed on the game screen. 
     [Advantageous Effects of Second Embodiment] The game system according to the present embodiment described above can offer the following advantageous effects as well as advantageous effects similar to those of the game system  1 A of the first embodiment. 
     The operation device  2 B includes the operation unit  23 , the power generation elements  251  each generating power according to an operation performed for the operation unit  23 , the battery BT supplying power, the switching unit  32  switching the operation mode according to an operation performed by the user, and the communication unit  29 A transmitting an operation signal corresponding to the operation unit  23  having been operated. The communication unit  29 A transmits the operation signal by use of power accumulated in the battery BT, in a case where the operation mode is the first mode. The communication unit  29 A transmits the operation signal by use of power generated by the power generation elements  251 , in a case where the operation mode is the second mode. 
     According to this configuration, the user is allowed to select the desired operation mode from the first mode which consumes power accumulated in the battery BT but achieves transmission of an operation signal without delay, and the second mode which may produce a delay but preserves power accumulated in the battery BT. In this manner, even in a case where a certain residual quantity remains in the battery BT, for example, this residual quantity can be preserved in the battery BT by switching to the second mode. Accordingly, replacement of the battery BT and the frequency of charging can be both reduced. As a result, usability of the operation device  2 B improves. 
     The operation device  2 B includes the mode switching unit  314  which switches the operation mode to one of the first mode and the second mode according to a switching signal input from the switching unit  32 . The switching unit  32  outputs a switching signal using power supplied from the battery BT. 
     According to this configuration, the switching unit  32  is unable to output a switching signal unless power sufficient for outputting a switching signal from the switching unit  32  remains in the battery BT. Accordingly, in a case where only a small residual quantity remains in the battery BT, the operation mode of the operation device  2 B is unable to switch to the first mode, of the first and second modes, as the mode for transmitting an operation signal by use of power supplied from the battery BT. In this manner, regulation of switching to the first mode is achievable according to the residual quantity of the battery BT. As a result, usability of the operation device  2 B further improves. 
     [Third Embodiment] A third embodiment of the present disclosure will subsequently be described. 
     A game system according to the present embodiment has a configuration similar to the configurations of the game systems of the first and second embodiments, but is different from the game systems of the first and second embodiments in a point that a condition for switching from the first mode to the second mode is further added. 
     Note that parts presented in the following description and identical or substantially identical to the corresponding parts already described are given identical reference signs to omit the same description. 
     [General Configuration of Game System]  FIG.  13    is a block diagram depicting a configuration of an operation device  2 C included in the game system according to the present embodiment. 
     The game system according to the present embodiment corresponds to an operation system. The game system according to the present embodiment has configurations and functions similar to those of the game system of the second embodiment except for a point that the operation device  2 C depicted in  FIG.  12    is provided instead of the operation devices  2 A and  2 B. Specifically, the game system according to the present embodiment includes the operation device  2 C, the game device  4 , and the display device  6 . The game system of the present embodiment operates in manners similar to the manners of the game system of the second embodiment. Specifically, the operation device  2 C transmits an operation signal corresponding to an input operation input by the user. The game device  4  advances a game according to the operation signal. The display device  6  displays a screen during execution of the game. 
     Respective configurations of the game system according to the present embodiment will hereinafter be described. 
     [Configuration of Operation Device] The operation device  2 C transmits an operation signal corresponding to an input operation input by the user similarly to the operation devices  2 A and  2 B. 
     Similarly to the operation devices  2 A and  2 B, the operation device  2 C has a first function which automatically switches the operation mode from the first mode to the second mode when the residual quantity of the battery BT decreases and reaches a quantity smaller than the predetermined residual quantity. Moreover, similarly to the operation device  2 B, the operation device  2 C has a second function which switches the operation mode according to an operation performed by the user when the residual quantity of the battery BT is the predetermined residual quantity or larger. 
     Further, the operation device  2 C has a third function which allows switching from the second mode to the first mode in a case where power supplied from the outside is larger than predetermined power, i.e., in a case where voltage supplied from the outside is higher than predetermined voltage, even when the residual quantity of the battery BT is smaller than the predetermined residual quantity. 
     [Configuration of Device Body] The operation device  2 C includes the housing  21  and a device body  22 C. 
     As depicted in  FIG.  12   , the device body  22 C has configurations and functions similar to those of the device body  22 B except for points that a communication unit  29 C and a control unit  31 C are provided instead of the communication unit  29 A and the control unit  31 A, and that a connection unit  33  and a power reception unit  34  are further provided. Specifically, the device body  22 C includes the operation unit  23 , the detection unit  24 , the power generation unit  25 , the charging unit  26 , the notification unit  27 , the vibration unit  28 , the communication unit  29 C, the storage unit  30 , the control unit  31 C, the switching unit  32 , the connection unit  33 , and the power reception unit  34 . 
     [Configuration of Connection Unit] The connection unit  33  is a terminal capable of receiving supply of power from an electronic device such as the game device  4  via a cable or the like, and communicating with the connected electronic device. In a case where the operation device  2 C and the game device  4  are connected to each other by a wire, a wired communication unit  293  included in the communication unit  29 C and described below communicates with the game device  4  via the connection unit  33 . For example, the connection unit  33  may be constituted by a USB (Universal Serial Bus) terminal. 
     [Configuration of Power Reception Unit] The power reception unit  34  receives power transmitted from the outside, and outputs the received power to the charging unit  26  and the control unit  31 C. The power reception unit  34  includes a wireless power reception unit  341  and a wired power reception unit  342 . 
     The wireless power reception unit  341  receives power wirelessly supplied from the outside, and outputs the received power. The wireless power reception unit  341  may adopt a radio wave reception type configuration which has an antenna, and a rectifying circuit which converts electromagnetic waves received by the antenna into direct currents. Alternatively, the wireless power reception unit  341  may adopt such a configuration which has a resonator magnetically resonating with a resonator on the power transmission side and receives power by a magnetic resonance system. Instead, the wireless power reception unit  341  may adopt an electromagnetic induction type configuration or an electric field coupling system configuration. Note that the device on the transmission side for transmitting power to the wireless power reception unit  341  may be constituted by the game device  4 , or other devices. 
     The wired power reception unit  342  receives power supplied from the outside and outputs the received power via the connection unit  33 . 
     [Configuration of Communication Unit] Similarly to the communication unit  29 A, the communication unit  29 C transmits an operation signal corresponding to an input operation performed by the user for the operation unit  23  under control by the control unit  31 C. The communication unit  29 C includes the first communication unit  291  and the second communication unit  292 , and further includes a wired communication unit  293 . 
     In a case where the connection unit  33  is connected to the game device  4 , the wired communication unit  293  transmits an operation signal to the game device  4  by a wire via the connection unit  33  under control by the first control unit  311 . In addition, in a case where the wired communication unit  293  communicates with the game device  4 , communication with the game device  4  achieved using the first communication unit  291  and the second communication unit  292  is regulated by the control unit  31 C. 
     [Configuration of Control Unit] The control unit  31 C controls operations of the operation device  2 C. The control unit  31 C includes a first control unit  311 C, a second control unit  312 C, a charging control unit  313 C, and a mode switching unit  314 C. 
     [Configuration of Charging Control Unit] The charging control unit  313 C charges the battery BT by controlling the charging unit  26  to charge the battery BT by use of power output from the power generation elements  251  and the power reception unit  34 . Note that the charging control unit  313 C regulates charging of the battery BT by the charging unit  26 , in a case where the residual quantity of the battery BT is full, similarly to the charging control unit  313 . 
     [Configuration of Mode Switching Unit] Similarly to the mode switching unit  314 , the mode switching unit  314 C switches the operation mode of the operation device  2 C to either one of the first mode and the second mode and actuates either one of the first control unit  311 C and the second control unit  312 . 
     Specifically, in a case where the residual quantity of the battery BT is the predetermined residual quantity or larger, the mode switching unit  314 C switches the operation mode of the operation device  2 C to either one of the first mode and the second mode according to a switching signal when the switching signal is input from the switching unit  32 . Specifically, in a case where the residual quantity of the battery BT is the predetermined residual quantity or larger, the operation mode of the operation device  2 C is switchable to both of the first mode and the second mode. 
     Moreover, in a case where the power received by the power reception unit  34  has a predetermined value or higher even when the residual quantity of the battery BT is smaller than the predetermined residual quantity, the mode switching unit  314 C switches the operation mode of the operation device  2 C to either one of the first mode and the second mode according to a switching signal when the switching signal is input from the switching unit  32 . Note that the mode switching unit  314 C may automatically switch the operation mode of the operation device  2 C to the first mode in a case where the power output from the wireless power reception unit  341  or the wired power reception unit  342  has a predetermined value or higher. 
     On the other hand, the mode switching unit  314 C switches the operation mode of the operation device  2 C to the second mode in a case where the power received by the power reception unit  34  has a value lower than the predetermined value and the residual quantity of the battery BT is smaller than the predetermined residual quantity. In this situation, even in a case where a switching signal for switching the operation mode of the operation device  2 C to the first mode is input from the switching unit  32 , the mode switching unit  314 C maintains the second mode while ignoring the switching signal thus input. 
     [Configuration of First Control Unit] The first control unit  311 C has a function similar to the function of the first control unit  311 . Specifically, the first control unit  311 C operates in a case where the operation device  2 C is in the first mode, and controls the notification unit  27 , the vibration unit  28 , and the first communication unit  291  by use of power supplied from the battery BT. 
     Moreover, in a case where the operation device  2 C is connected to the game device  4  by a wire via the connection unit  33 , the first control unit  311 C transmits an operation signal not by the first communication unit  291  but by the wired communication unit  293 . Specifically, the first control unit  311 C determines whether or not communication with the game device  4  by a wire via the connection unit  33  is allowed, and causes the wired communication unit  293  to transmit an operation signal to the game device  4  in a case of determination that this communication is allowed. In addition, in a case where the first control unit  311 C causes the wired communication unit  293  to transmit an operation signal, the first control unit  311 C causes the wired communication unit  293  to transmit such an operation signal containing information indicating the operation mode of the operation device  2 C. 
     On the other hand, in a case where the operation device  2 C does not communicate with the game device  4  by a wire, i.e., in a case where the operation device  2 C wirelessly communicates with the game device  4 , the first control unit  311 C causes the first communication unit  291  to transmit an operation signal. 
     [Configuration of Second Control Unit] The second control unit  312 C has a function similar to the function of the second control unit  312 . Specifically, the second control unit  312 C operates in a case where the operation device  2 C is in the second mode and controls the second communication unit  292  with power supplied from the power generation elements  251 . 
     Moreover, in a case where the operation device  2 C is connected to the game device  4  by a wire via the connection unit  33 , the second control unit  312 C transmits an operation signal not by the second communication unit  292  but by the wired communication unit  293 . Specifically, similarly to the first control unit  311 C, the second control unit  312 C determines whether or not communication with the game device  4  by a wire via the connection unit  33  is allowed and causes the wired communication unit  293  to transmit an operation signal to the game device  4  in a case of determination that this communication is allowed. In addition, in a case where the second control unit  312 C causes the wired communication unit  293  to transmit an operation signal, the second control unit  312 C causes the wired communication unit  293  to transmit such an operation signal containing information which indicates the operation mode of the operation device  2 C. 
     On the other hand, in a case where the operation device  2 C does not communicate with the game device  4  by a wire, i.e., in a case where the operation device  2 C wirelessly communicates with the game device  4 , the second control unit  312 C causes the second communication unit  292  to transmit an operation signal. 
     In this manner, the operation device  2 C gives priority to wired communication over wireless communication at the time of transmission of an operation signal. 
     [Configuration of Game Device] Also in the game system of the present embodiment, the game device  4  similarly advances a game according to operation signals received from the operation device  2 C and displays a screen during execution of the game on the display device  6 . 
     In a case where the game device  4  communicates with the operation device  2 C herein, the mode determination unit  443  determines the operation mode of the operation device  2 C on the basis of information contained in a received operation signal, regardless of whether the communication system is wired communication or wireless communication. In a case where the mode determination unit  443  determines that the operation mode of the operation device  2 C is the second mode, a screen during execution similar to the screen during execution P 1  depicted in  FIG.  6    is displayed. 
     At this time, in a case where the handleability determination unit  444  determines, on the basis of information acquired from the server SVA, that the game currently executed is not handleable in the second mode of the operation device  2 C and where power received by the power reception unit  34  has a value lower than the predetermined value, the display control unit  445  having a function of a notification unit displays a screen during execution similar to the screen of execution P 5  depicted in  FIG.  12   . 
     In this manner, a notification is given to indicate that the operation mode of the operation device  2 C has been switched to the second mode, that the game currently executed is not handleable in the second mode, and that the received power is insufficient. 
       FIG.  14    is a diagram depicting a screen during execution P 6  as an example of a screen during execution displayed on the display device  6  by the information processing device  7 . 
     Meanwhile, in a case where the handleability determination unit  444  determines that the game currently executed is not handleable in the second mode and where power received by the power reception unit  34  has the predetermined value or higher, the display control unit  445  displays the screen during execution P 6  depicted in  FIG.  14   , for example. 
     In this manner, a notification is given to indicate that the operation mode of the operation device  2 C has been switched to the second mode, that the game currently executed is not handleable in the second mode, and that switching to the first mode is allowed. 
     Note that the messages displayed in the respective screens during execution may be displayed in a manner not to interrupt the game currently executed, similarly to the game systems of the first and second embodiments. For example, similarly to the screen during execution P 1 A, each of the messages displayed in the respective screens during execution may be displayed in the message region R 2  not overlapping with the screen region R 1 . Moreover, for example, a message transmittable to such a level that the game screen is observable may be superimposed and displayed on the game screen. 
     [Advantageous Effects of Third Embodiment] The game system according to the present embodiment described above can offer the following advantageous effects as well as advantageous effects similar to those of the game system  1 A of the first embodiment and the game system of the second embodiment. 
     The operation device  2 C includes the operation unit  23 , the power generation elements  251  generating power according to an operation performed for the operation unit  23 , and the battery BT supplying power. In addition, the operation device  2 C includes the power reception unit  34  receiving power supplied from the outside, and the communication unit  29 C transmitting an operation signal corresponding to the operation unit  23  having been operated. In a case where the power received by power reception unit  34  has a predetermined value or higher, the communication unit  29 C transmits an operation signal by use of power supplied from the battery BT charged by power received by the power reception unit  34 . Moreover, in a case where power received by the power reception unit  34  has a value lower than the predetermined value, the communication unit  29 C transmits an operation signal by use of power generated by the power generation elements  251 . 
     This configuration achieves transmission of an operation signal by use of power generated by the power generation elements  251  in a case where received power is not sufficiently high, e.g., in a case where power lower than power sufficient for transmitting an operation signal is received, even when power is supplied from the outside. Therefore, even in the case of supply of power from the outside, the operation signal transmission state is switchable according to the power supplied from the outside. Accordingly, usability of the operation device  2 C improves. 
     [Fourth Embodiment] A fourth embodiment of the present disclosure will subsequently be described. 
     A game system according to the present embodiment has a configuration similar to the configurations of the game systems of the first to third embodiments but is different from the game systems of the first to third embodiments in points that an information processing device is provided in place of the game device  4 , and that a server has a configuration of the game device  4 . Note that parts presented in the following description and identical or substantially identical to the corresponding parts already described are given identical reference signs to omit the same description. 
     [General Configuration of Game System]  FIG.  15    is a schematic diagram depicting a configuration of a game system  1 B according to the present embodiment. 
     The game system  1 B according to the present embodiment corresponds to an operation system. As depicted in  FIG.  15   , the game system  1 B includes the operation device  2 A, the information processing device  7 , the display device  6 , and a server SVB. The game system  1 B is capable of achieving cloud gaming where the information processing device  7  transmits operation signals received from the operation device  2 A to the server SVB via the network N. The server SVB executes a game according to the received operation signals and transmits an image of a screen during execution obtained as a processing result to the information processing device  7 . The information processing device  7  receives the image obtained by the server SVB as the processing result and displays the received image on the display device  6 . In this manner, the game is allowed to be advanced. 
     Specifically, the information processing device  7  functions as a relay device providing a relay between the operation device  2 A and the server SVB, and displays the image received from the server SVB on the display device  6 . 
     Note that the information processing device  7  in the example of  FIG.  15    is a notebook PC (Personal Computer), and is connected to the network N via an access point AP. However, the information processing device  7  is not limited to a PC but may be other types of information processing device such as a game device and a smartphone. Moreover, in a case where the information processing device  7  is a notebook PC, the display device  6  may be a display device built in the notebook PC. 
     [Configuration of Server] As described above, the server SVB has a function of the game device  4 . Specifically, while not depicted in the figure, the server SVB includes the communication unit  41 , the storage unit  42 , the memory  43 , and the control unit  44  connected to each other via a bus line. 
     According to the present embodiment, the communication unit  41  communicates with the information processing device  7  via the network N. 
     The storage unit  42  stores an OS for controlling the server SVB, and game programs. Moreover, the storage unit  42  stores at least either information indicating categories of games executable by the server SVB and categories handleable in the second mode, or information indicating games handleable in the second mode. 
     The control unit  44  has the execution unit  441 , the information acquisition unit  442 , the mode determination unit  443 , the handleability determination unit  444 , and the display control unit  445 . 
     The execution unit  441  executes a game selected by the user according to operation signals received from the operation device  2 A via the information processing device  7 . 
     The information acquisition unit  442  acquires information associated with the game currently executed from the storage unit  42 . 
     The mode determination unit  443  and the handleability determination unit  444  operate in manners similar to the corresponding manners described above. 
     The display control unit  445  corresponds to a notification unit. The display control unit  445  generates a screen during execution of the game and transmits an image of the generated screen during execution to the information processing device  7 . In this manner, the information processing device  7  displays the received image on the display device  6  to present a screen during execution such as the screens during execution P 1  to P 4 . 
     As described above, the information processing device  7  is capable of advancing a game by transmitting operation signals received from the operation device  2 A to the server SVB, and displaying a screen during execution received from the server SVB on the display device  6 , and also capable of giving a notification of the operation mode of the operation device  2 A using a message indicating the operation mode of the operation device  2 A. 
     [Advantageous Effects of Fourth Embodiment] The game system  1 B according to the present embodiment described above can offer the following advantageous effects as well as advantageous effects similar to those of the game systems of the first to third embodiments. 
     For example, the game system  1 B equivalent to an operation system includes the operation device  2 A transmitting an operation signal, the information processing device  7  receiving the operation signal, and the server SVB communicating with the information processing device. The operation device  2 A includes the operation unit  23 , the power generation elements  251  each generating power according to an operation performed for the operation unit  23 , the battery BT supplying power, and the communication unit  29 A functioning as a transmission unit which transmits an operation signal corresponding to the operation unit  23  having been operated. The operation device  2 A operates in either one of the first mode where the communication unit  29 A transmits an operation signal by use of power supplied from the battery BT, and the second mode where the communication unit  29 A transmits an operation signal by use of power generated by the power generation elements  251 . The operation signal contains information indicating the operation mode of the operation device  2 A. 
     The information processing device  7  transmits the operation signal received from the operation device  2 A to the server SVB. The information processing device  7  receives, from the server SVB, a screen during execution obtained by the server SVB as a processing result. The information processing device  7  displays the screen during execution on the display device  6 , for example. 
     The server SVB includes the mode determination unit  443 , and the display control unit  445  functioning as a notification unit. The mode determination unit  443  determines the operation mode of the operation device  2 A on the basis of an operation signal received from the information processing device  7 . When the mode determination unit  443  determines that the operation mode of the operation device  2 A has been switched from the first mode to the second mode, the display control unit  445  transmits a screen during execution obtained as a processing result which is to be given by the information processing device  7  as a notification of the operation mode of the operation device  2 A. 
     According to this configuration, similarly to the game system  1 A, the information processing device  7  gives a notification indicating the operation mode of the operation device  2 A on the basis of a processing result received from the server SVB when the operation mode of the operation device  2 A is switched to the second mode which may produce a transmission delay of an operation signal from an operation performed by the user. Specifically, the display control unit  445  of the server SVB causes the information processing device  7  to give a notification that the operation mode of the operation device  2 A has been switched to the second mode. This configuration can notify the user of the fact of switching to the second mode when the operation mode of the operation device  2 A is switched to the second mode. Accordingly, usability of the game system  1 B as an operation system improves. 
     The server SVB further includes the execution unit  441  and the handleability determination unit  444 . The execution unit  441  executes a game according to operation signals transmitted from the operation device  2 A and received by the information processing device  7 . When the mode determination unit  443  determines that the operation mode of the operation device  2 A is the second mode, the handleability determination unit  444  determines whether or not the game currently executed is handleable in the second mode. When the handleability determination unit  444  determines that the game currently executed is not handleable in the second mode, the display control unit  445  functioning as a notification unit transmits, to the information processing device  7 , a screen during execution obtained as a processing result which is to be given by the information processing device  7  as a notification that the game is not handleable in the second mode. 
     According to this configuration, the game device  4  can notify the user of the fact that the game currently executed is not handleable in the second mode when the operation mode of the operation device  2 A is switched to the second mode. Accordingly, usability of the game system  1 B further improves. 
     Note that the game system  1 B includes the operation device  2 A as an operation device, and that the server SVB has a function similar to the function of the game device  4  presented in the first embodiment. However, the game system  1 B is not limited to this. The game system  1 B may include the operation device  2 B or the operation device  2 C as an operation device, while the server SVB may have a configuration similar to the configuration of the game device  4  presented in the second or third embodiment. In this case, the operation device  2 B or  2 C is only required to be connected to the information processing device  7  by wired or wireless connection. 
     [Modifications of Embodiments] The present disclosure includes not only the respective embodiments described above, but also modifications, improvements, and the like made within a range where the object of the present disclosure is achievable. 
     According to the present embodiments described above, each of the operations  2 A,  2 B, and  2 C automatically switches the operation mode to the second mode when the residual quantity of the battery BT becomes smaller than the predetermined residual quantity. However, this example is not required to be adopted. For example, each of the operations  2 B and  2 C may be configured to switch the operation mode only by using the switching unit  32  and the mode switching unit  314 . 
     According to the third and fourth embodiments described above, the operation device  2 C can switch the operation mode according to an operation by the user using the switching unit  32  and the mode switching unit  314 . However, this example is not required to be adopted. The operation device  2 C may achieve switching of the operation mode only on the basis of a level of power received by the power reception unit  34 . In other words, the operation device  2 C may be a device having only the third function of the first to third functions described above. 
     According to the first, second, and fourth embodiments described above, each of the operation devices  2 A and  2 B includes the charging unit  26 , the notification unit  27 , and the vibration unit  28 . However, this example is not required to be adopted. Each of the operation devices  2 A and  2 B may eliminate at least any one of the charging unit  26 , the notification unit  27 , and the vibration unit  28 . 
     According to the third and fourth embodiments described above, the operation device  2 C includes the notification unit  27  and the vibration unit  28 . However, this example is not required to be adopted. The operation device  2 C may eliminate at least either one of the notification unit  27  and the vibration unit  28 . 
     According to the respective embodiments described above, an operation signal contains information indicating that this operation signal is an operation signal transmitted from the first communication unit  291  by use of power supplied from the battery BT, or information indicating that this operation signal is an operation signal transmitted from the second communication unit  292  by use of power supplied from the power generation elements  251 . Accordingly, the operation signal contains information indicating the communication unit corresponding to a transmission source of the operation signal. In other words, the operation signal contains information indicating the operation mode of the operation device  2 A,  2 B, or  2 C. However, this example is not required to be adopted. The operation signal need not contain information indicating the transmission source of the operation signal, and information indicating the operation mode. 
     According to the respective embodiments described above, in a case where an operation signal is transmitted from the first communication unit  291 , the first control units  311  and  311 C each having a function of a transmission regulation unit transmit regulation signals to the second control units  312  and  312 C, respectively, to regulate transmission of an operation signal from the second communication unit  292 . However, this example is not required to be adopted. The game device  4 , the information processing device  7 , or the server SVB each receiving an operation signal from the operation device  2 A,  2 B, or  2 C may ignore an operation signal received from the second communication unit  292 . 
     According to the second to fourth embodiments described above, the switching unit  32  outputs a switching signal to the control unit  31 B by use of power supplied from the battery BT. However, this example is not required to be adopted. The switching unit  32  may have a power generation element and output a switching signal by use of power generated by this power generation element according to an operation performed by the user for the switching unit  32 . 
     According to the respective embodiments described above, each of the plurality of detection elements  241 , and each of the plurality of power generation elements  251  output identification information associated with a corresponding detection target. However, this example is not required to be adopted. For example, in a case where the detection elements  241  and the power generation elements  251  corresponding to the respective operators constituting the operation unit  23  are individually connected to the control unit  31 A,  31 B, or  31 C, each of the detection elements  241  and the power generation elements  251  need not output identification information associated with the corresponding detection target. 
     According to the respective embodiments described above, the operation unit  23 , the detection unit  24 , and the power generation unit  25  have different configurations. However, this example is not required to be adopted. Such a configuration which unifies one of the operators of the operation unit  23 , the detection elements  241 , and the power generation elements  251  may be adopted. 
     According to the third and fourth embodiment described above, the power reception unit  34  includes the wireless power reception unit  341  and the wired power reception unit  342 . However, this example is not required to be adopted. The power reception unit  34  is only required to have at least either one of the wireless power reception unit  341  and the wired power reception unit  342 . 
     According to the first to third embodiments described above, the electronic device corresponding to the operation target of the operation device  2 A,  2 B, or  2 C is the game device  4 . According to the fourth embodiment described above, the electronic device corresponding to the operation target of the operation device  2 A,  2 B, or  2 C is the server SVB communicable with the information processing device  7 . However, this example is not required to be adopted. The electronic device corresponding to the operation target operated by the operation device of the present disclosure may be an electronic device other than a game device, such as a television and AV (audiovisual) equipment. 
     Moreover, according to the fourth embodiment, the information processing device  7  is not necessarily required to display a screen during execution, which is a processing result obtained by the server SVB, on the display device  6 . The information processing device  7  is only required to give a notification of the operation mode of the operation device  2 A,  2 B, or  2 C. 
     According to the first to third embodiments described above, the handleability determination unit  444  of the game device  4  determines whether or not the game currently executed is handleable in the second mode of the operation device  2 A,  2 B, or  2 C on the basis of information acquired from the server SVA. Moreover, according to the fourth embodiment described above, the handleability determination unit  444  of the server SVB determines whether or not the game currently executed is handleable in the second mode of the operation device  2 A,  2 B, or  2 C on the basis of information acquired from the storage unit  42 . However, this example is not required to be adopted. The handleability determination unit  444  may determine whether or not the game currently executed is handleable in the second mode on the basis of other information. 
     Moreover, this information associated with the game may be stored in the storage unit  42  of the game device  4  beforehand or may be acquired from an external device other than the servers SVA and SVB. Further, the information associated with the game may be contained in a game program. 
     According to the respective embodiments described above, the operation unit  23  includes the touch pad  235  and the sticks  236 . However, this example is not required to be adopted. At least either one of the touch pad  235  and the sticks  236  may be eliminated from the operation unit  23 . 
     Moreover, the operation unit  23  includes the one direction button  231 , the four buttons  232 , the two buttons  233 , and the four buttons  234 . However, this example is not required to be adopted. The operation unit  23  is only required to have at least one operator. 
     Further, the operation devices  2 A,  2 B, and  2 C each having the layout depicted in  FIG.  2    by way of example have been presented as the operation device of the present disclosure. However, this example is not required to be adopted. The operation device of the present disclosure is not limited to the operation devices  2 A,  2 B, and  2 C each having the layout described above, but may be an operation device having a layout adoptable as a remote controller of a television or the like, for example. Accordingly, the operation device of the present disclosure is not limited to a game controller. 
     According to the respective embodiments described above, the handleability determination unit  444  determines whether or not the game currently executed is handleable in the second mode. However, this example is not required to be adopted. For example, in a case where the user selects a game to be executed on a game selection screen or the like, a notification unit may give a notification indicating a determination result obtained by determining whether or not the selected game is handleable in the second mode. 
     In addition, the handleability determination unit  444  may be eliminated. In this case, when the mode determination unit  443  determines that the operation mode of the operation device has been switched from the first mode to the second mode, the notification unit such as the display control unit  445  may give a notification indicating the operation mode of the operation device by use of the display device  6 , the information processing device  7 , or the like. 
     [Summary of Present Disclosure] A summary of the present disclosure will hereinafter be additionally noted. 
     An operation device according to a first aspect of the present disclosure includes an operation unit, a power generation element that generates power according to an operation of the operation unit, a battery that supplies power, and a communication unit that transmits an operation signal corresponding to the operation unit that has been operated, in which the communication unit transmits the operation signal by use of power supplied from the battery, in a case where a residual quantity of the battery is a predetermined residual quantity or larger, and the communication unit transmits the operation signal by use of power generated by the power generation element, in a case where the residual quantity of the battery is smaller than the predetermined residual quantity. 
     This configuration achieves transmission of an operation signal by use of power supplied from the battery, in a case where the residual quantity of the battery is the predetermined residual quantity or larger. Accordingly, transmission of an operation signal is achievable without delay. On the other hand, in a case where the residual quantity of the battery is smaller than the predetermined residual quantity, a transmission delay of an operation signal may be produced. However, the operation device does not become disabled. Accordingly, usability of the operation device improves. 
     An operation device according to a second aspect of the present disclosure includes an operation unit, a power generation element that generates power according to an operation of the operation unit, a battery that supplies power, a switching unit that switches an operation mode according to an operation performed by a user, and a communication unit that transmits an operation signal corresponding to the operation unit that has been operated, in which the communication unit transmits the operation signal by use of power accumulated in the battery, in a case where the operation mode is a first mode, and the communication unit transmits the operation signal by use of power generated by the power generation element, in a case where the operation mode is a second mode. 
     According to this configuration, the user is allowed to select the desired operation mode from the first mode which consumes power accumulated in the battery but achieves transmission of an operation signal without delay, and the second mode which may produce a delay but preserves power accumulated in the battery. In this manner, even in a case where a certain residual quantity remains in the battery, for example, this residual quantity can be preserved in the battery by switching to the second mode. Accordingly, replacement of the battery and the frequency of charging can be both reduced. As a result, usability of the operation device improves. 
     In the second aspect described above, there may be further provided a mode switching unit that switches the operation mode to either one of the first mode and the second mode according to a switching signal input from the switching unit, and the switching unit may output the switching signal by use of power supplied from the battery. 
     According to this configuration, the switching unit is unable to output a switching signal unless power sufficient for outputting a switching signal from the switching unit remains in the battery. Accordingly, in a case where only a small residual quantity remains in the battery, the operation mode of the operation device cannot switch to the first mode of the first and second modes, as the mode for transmitting an operation signal by use of power supplied from the battery. In this manner, regulation of switching to the first mode is achievable according to the residual quantity of the battery. As a result, usability of the operation device further improves. 
     An operation device according to a third aspect of the present disclosure include an operation unit, a power generation element that generates power according to an operation of the operation unit, a battery that supplies power, a power reception unit that receives power externally supplied, and a communication unit that transmits an operation signal corresponding to the operation unit that has been operated. In a case where power received by the power reception unit has a predetermined value or higher, the communication unit transmits the operation signal by use of the power supplied from the battery charged by power received by the power reception unit, and in a case where the power received by the power reception unit has a value lower than the predetermined value, the communication unit transmits the operation signal by use of the power generated by the power generation element. 
     This configuration achieves transmission of an operation signal by use of power generated by the power generation element in a case where received power is not sufficiently high, e.g., in a case where power lower than power sufficient for transmitting an operation signal is received, even when power is supplied from the outside. Therefore, even in the case of supply of power from the outside, the operation signal transmission state is switchable according to the power supplied from the outside. Accordingly, usability of the operation device improves. 
     In the first to third aspects described above, there may be further provided a notification unit that gives a notification of an operation state of the operation device by presenting a lighting state. The notification unit may light to give a notification that the communication unit transmits the operation signal by use of the power supplied from the battery, and the notification unit may not light to give a notification that the communication unit transmits the operation signal by use of the power generated by the power generation element. 
     This configuration allows the user to check whether the operation signal has been transmitted by use of power of the battery, or the operation signal has been transmitted by use of power generated by the power generation element on the basis of the lighting state of the notification unit. Accordingly, usability of the operation device further improves. 
     In the first to third aspects described above, there may be further provided a notification unit that gives a notification of an operation state of the operation device by presenting a lighting state, and the notification unit may light in a first color to give a notification that the communication unit transmits the operation signal by use of the power supplied from the battery, and the notification unit may light in a second color different from the first color to give a notification that the communication unit transmits the operation signal by use of the power generated by the power generation element. 
     This configuration can offer advantageous effects similar to those of the configuration including the notification unit which gives the notification of the operation state of the operation device by lighting or not lighting. 
     In the first to third aspects described above, the communication unit may include a first communication unit that transmits the operation signal by use of the power supplied from the battery, and a second communication unit that transmits the operation signal by use of the power generated by the power generation element, and the operation signal may contain information indicating whether the operation signal has been transmitted by use of the power supplied from the battery, or the operation signal has been transmitted by use of the power supplied from the power generation element. 
     Note that the operation signal may contain information indicating whether the operation signal has been transmitted from the first communication unit, or transmitted from the second communication unit, as the information indicating whether the operation signal has been transmitted by use of the power supplied from the battery, or the operation signal has been transmitted by use of the power supplied from the power generation element. 
     According to this configuration, the state of the operation device is recognizable on the basis of the operation signal received by a reception device which receives the operation signal from the operation device. 
     In the first to third aspects described above, there may be further provided a transmission regulation unit that regulates transmission of the operation signal from the second communication unit in a case where the first communication unit transmits the operation signal. 
     This configuration can prevent transmission of an operation signal from each of the first communication unit and the second communication unit in response to an operation performed for the same operation unit. 
     In the first to third aspects described above, there may be further provided a charging unit that charges the battery by use of the power generated by the power generation element. 
     This configuration allows charging of the battery while using the operation device. Accordingly, usability of the operation device further improves. 
     In the first to third aspects described above, there may be further provided a vibration unit that generates vibration at a time of transmission of the operation signal. 
     This configuration can notify the user of the fact that an operation signal has been transmitted in response to an operation. Accordingly, usability of the operation device further improves. 
     In the first to third aspects described above, there may be further provided a housing, and a touch pad provided in such a manner as to be able to be inserted and protruded into the housing, and the operation unit may include the touch pad. 
     This configuration achieves transmission of the operation signal by an operation of the touch pad in a manner of a button. Accordingly, general versatility of the operation device improves. 
     An operation system according to a fourth aspect of the present disclosure includes an operation device that transmits an operation signal, and an electronic device that receives the operation signal and operates, and the operation device includes an operation unit, a power generation element that generates power according to an operation of the operation unit, a battery that supplies power, and a transmission unit that transmits the operation signal corresponding to the operation unit that has been operated. The operation device operates in either one of a first mode where the transmission unit transmits the operation signal by use of power supplied from the battery and a second mode where the transmission unit transmits the operation signal by use of power generated by the power generation element. The operation signal contains information indicating an operation mode of the operation device, and the electronic device includes a reception unit that receives the operation signal from the operation device, a mode determination unit that determines the operation mode of the operation device on the basis of the operation signal received by the reception unit, and a notification unit that gives a notification indicating the operation mode of the operation device, when the mode determination unit determines that the operation mode of the operation device has been switched from the first mode to the second mode. 
     According to this configuration, the electronic device gives a notification indicating the operation mode of the operation device using the notification unit when the operation mode of the operation device is switched to the second mode which may produce a transmission delay of an operation signal from the time of the operation performed by the user. In other words, the notification unit gives a notification that the operation mode of the operation device has been switched to the second mode. This configuration can notify the user of switching to the second mode when the operation mode of the operation device is switched to the second mode without intention of the user, for example. Accordingly, usability of the operation system improves. 
     In the fourth aspect described above, the electronic device may be a game device that executes a game. The game device may include a handleability determination unit that determines whether or not the game is handleable in the second mode, when the mode determination unit determines that the operation mode is the second mode, and the notification unit may give a notification that the game is not handleable in the second mode, when the handleability determination unit determines that the game is not handleable in the second mode. 
     According to this configuration, the game device as the electronic device can notify the user of the fact that the game currently executed is not handleable in the second mode when the operation mode of the operation device is switched to the second mode. Accordingly, usability of the operation system constituted by the game system further improves. 
     An operation system according to a fifth aspect of the present disclosure includes an operation device that transmits an operation signal, an information processing device that receives the operation signal, and a server that communicates with the information processing device. The operation device includes an operation unit, a power generation element that generates power according to an operation of the operation unit, a battery that supplies power, and a transmission unit that transmits the operation signal corresponding to the operation unit that has been operated. The operation device operates in either one of a first mode where the transmission unit transmits the operation signal by use of power supplied from the battery and a second mode where the transmission unit transmits the operation signal by use of power generated by the power generation element. The operation signal contains information indicating an operation mode of the operation device. The information processing device transmits the operation signal received from the operation device to the server, and receives a processing result obtained by the server from the server. The server includes a mode determination unit that determines the operation mode of the operation device on the basis of the operation signal received from the information processing device, and a notification unit that transmits, to the information processing device, the processing result to be given by the information processing device as a notification indicating the operation mode of the operation device, when the mode determination unit determines that the operation mode of the operation device has been switched from the first mode to the second mode. 
     According to this configuration, similarly to the operation system of the fourth aspect, the information processing device gives a notification indicating the operation mode of the operation device on the basis of a processing result received from the server when the operation mode of the operation device is switched to the second mode which may produce a transmission delay of an operation signal from an operation performed by the user. Specifically, the notification unit of the server causes the information processing device to give a notification that the operation mode of the operation device has been switched to the second mode. This configuration can notify the user of the fact of switching to the second mode when the operation mode of the operation device is switched to the second mode without intention of the user, for example. Accordingly, usability of the operation system improves. 
     In the fifth aspect described above, the server may include an execution unit that executes a game according to the operation signal received from the information processing device, and a handleability determination unit that determines whether or not the game is handleable in the second mode, when the mode determination unit determines that the operation mode is the second mode. The notification unit may transmit, to the information processing device, the processing result to be given by the information processing device as a notification that the game is not handleable in the second mode, when the handleability determination unit determines that the game is not handleable in the second mode. 
     According to this configuration, the information processing device can notify the user of the fact that the game currently executed is not handleable in the second mode when the operation mode of the operation device is switched to the second mode. Accordingly, usability of the operation system further improves. 
     In the fourth and fifth aspects described above, the handleability determination unit may determine that the game is not handleable in the second mode, in a case where a category of the game to be executed is a predetermined category. 
     Note herein that a simulation game or a command selective system role playing game can advance a game even if a period from an operation by a user to transmission of an operation signal is relatively long. Accordingly, games in these categories are allowed to proceed even with long latency. On the other hand, games such as a shooting game and an action game are difficult to advance if transmission of an operation signal is delayed from an operation by a user. Accordingly, games in these categories may cause a problem in progress of the games if latency is long. 
     However, in a case where the game currently executed is not handleable in the second mode and the operation mode of the operation device is switched to the second mode, the configuration described above gives a notification of this fact. Accordingly, the user is easily urged to carry out operations such as charging of the battery. 
     In the fourth and fifth aspects described above, the handleability determination unit may determine whether or not the game is handleable in the second mode, on the basis of information associated with the game. 
     The configuration described above can determine whether or not the game currently executed is handleable in the second mode on the basis of the information associated with the game. 
     REFERENCE SIGNS LIST 
     
         
           1 A,  1 B: Game system (operation system) 
           2 A,  2 B,  2 C: Operation device 
           23 : Operation unit 
           231  to  234 : Button 
           235 : Touch pad 
           236 : Stick 
           24 : Detection unit 
           241 : Detection element 
           25 : Power generation unit 
           251 : Power generation element 
           26 : Charging unit 
           27 : Notification unit 
           28 : Vibration unit 
           29 ,  29 C: Communication unit (transmission unit) 
           291 : First communication unit 
           292 : Second communication unit 
           293 : Wired communication unit 
           30 : Storage unit 
           31 A,  31 B,  31 C: Control unit 
           311 ,  311 C: First control unit 
           312 ,  312 C: Second control unit 
           313 ,  313 C: Charging control unit 
           314 ,  314 C: Mode switching unit 
           32 : Switching unit 
           33 : Connection unit 
           33 : Power reception unit 
           341 : Wireless power reception unit 
           342 : Wired power reception unit 
           4 : Game device (electronic device) 
           41 : Communication unit (reception unit) 
           42 : Storage unit 
           43 : Memory 
           44 : Control unit 
           441 : Execution unit 
           442 : Information acquisition unit 
           443 : Mode determination unit 
           444 : Handleability determination unit 
           445 : Display control unit (notification unit) 
           6 : Display device 
           7 : Information processing device 
         BT: Battery 
         SVA: Server (external device) 
         SVB: Server