Abstract:
A vehicle call device, a call system, a center, and a calling method capable of detecting a problem while controlling the cost increase are disclosed. The vehicle call device includes a speaker mounted in a vehicle, the speaker outputting a received voice of an opposite communication party; a microphone mounted in the vehicle; an echo canceller unit removing the received voice that has been output from the speaker and input into the microphone; a detecting unit detecting an emergency situation of the vehicle; and a remove preventing unit preventing the eco canceller unit from removing the received voice when the detecting unit detects the emergency situation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C §119 to Japanese Patent Application Publication No. 2007-278834 filed Oct. 26, 2007, the entire contents of which are hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a vehicle call device and the like, and more particularly to a vehicle call device, a call system, a center, and a calling method capable of detecting a problem of the vehicle call device in emergency situations. 
     2. Description of the Related Art 
     Recently, an emergency call system has been mounted in vehicles, the system being capable of providing hands-free communications with an emergency service center (hereinafter may be referred to as a “center”), the police, a fire station, and the like for reporting a problem with the vehicle and calling for help. However, such an emergency call system may break down in an emergency situation when, for example, the vehicle is involved in an accident. Further, such an emergency situation may not come by so often, therefore a back-up battery may be almost discharged. As a result, a function of the emergency call system may not operate as expected in such an emergency situation. For example, when such an emergency call system is provided in a vehicle, an occupant of the vehicle and an operator of a center may talk with each other. However, when, for example, the microphone of the vehicle has a problem, the occupant becomes unable to talk with the operator. 
     On the other hand, the occupant may also be unable to talk to the operator even when the emergency call system works properly because the occupant is injured. Because of this possibility, when the operator of the center requests the occupant of the vehicle to respond to the operator&#39;s call through the emergency call system and no response from the occupant is detected, the operator may not be able to determine the reason for the not-detected response such as whether the microphone of the emergency call system has a problem or the occupant of the vehicle is unable to respond to the operator because of his/her injury. 
     To overcome the problem, there has been provided a vehicle emergency call system capable of detecting whether the speaker or the microphone in a vehicle is broken by playing a fixed voice message in the vehicle, collecting the played voice message using the microphone, and determining whether the collected fixed voice message corresponds to the played fixed voice message (see, for example, Japanese Patent Application Publication Nos. 2002-288772 and 2002-127858). 
     However, when the above method is employed where a problem is detected by determining whether the voice signal from the speaker corresponds to the voice signal collected by the microphone, there may arise a problem that when the voice or the noise level in the vicinity of the vehicle is high, the voice or the noise may be colleted by the microphone, which may result in its being determined that the emergency call system has a problem even though the emergency call system does not have any problem. Further, it may require a certain period of time to perform this type of decision process. Therefore, preferably, this type of decision process should not be performed in any emergency situation where there is no time to waste. Further, when this type of decision process is performed even in a situation other than an emergency situation, the occupant of the vehicle may feel uncomfortable because conversation between the occupants in the vehicle and playing an audio device are not allowed during the period of making the decision. Further, disadvantageously, it is necessary to mount additional elements the elements being for handling the fixed voice message and comparing the fixed voice messages onto the vehicle, thereby increasing the cost. 
     SUMMARY OF THE INVENTION 
     The present invention is made in light of these circumstances and may provide a vehicle call device, a call system, a center, and a calling method capable of detecting a problem with the vehicle call device while controlling the cost increase of the vehicle call device. 
     According to an aspect of the preset invention, a vehicle call device includes a speaker mounted in a vehicle, the speaker outputting a received voice of an opposite communication party; a microphone mounted in the vehicle; an echo canceller unit removing the received voice that has been output from the speaker and input into the microphone; a detecting unit detecting an emergency situation of the vehicle; and a remove preventing unit preventing the eco canceller unit from removing the received voice when the detecting unit detects the emergency situation. 
     With this configuration, by turning OFF the echo cancelling function of the echo canceller section, it becomes possible for the opposite communication party to easily determine whether the device mounted in the vehicle has a problem. Further, the element serving as the echo canceller unit is generally mounted in vehicles as standard equipment. Therefore, the cost increase may be minimized. 
     Further, the vehicle call device may further include a receiving unit receiving a preventing signal for preventing the removal of the received voice so that the remove preventing unit can prevent the eco canceller unit from removing the received voice when the receiving unit receives the preventing signal. 
     By doing this, for example, the opposite communication party may transmit the preventing signal. Therefore, it becomes possible to turn OFF the echo cancelling function of the echo canceller section based on the will of the opposite communication party and to determine whether the device mounted on the vehicle has a problem. 
     According to another aspect of the preset invention, the vehicle call device further includes a voice level detecting unit detecting a voice level collected by the microphone so that, when a voice level detected by the voice level detection unit is less than a prescribed value, the remove preventing unit prevents the eco canceller unit from removing the received voice. 
     By doing this, it becomes possible to automatically detect that the occupant of the vehicle is unable to respond by monitoring the voice signal level and to turn OFF the echo cancelling function of the echo canceller section. As a result, it becomes possible to determine whether the device mounted on the vehicle has a problem even when the opposite communication party does not do anything. 
     According to still another aspect of the preset invention, the vehicle call device includes a speaker mounted in a vehicle, the speaker outputting a received voice of an opposite communication party; a microphone mounted in the vehicle; an echo canceller unit removing the received voice that has been output from the speaker and input into the microphone; a detecting unit detecting an emergency situation of the vehicle; and a sound outputting unit outputting a prescribed sound when the detecting unit detects the emergency situation. 
     By doing this, it becomes possible to determine whether the device mounted on the vehicle has a problem based on whether the opposite communication party can hear the sound like a BGM. Further, the echo cancelling function of the echo canceller section is not turned OFF. Therefore, when the occupant of the vehicle responds, the voice of the occupant of the vehicle may be easily heard. 
     According to an embodiment of the present invention, a vehicle call device, a call system, a center, and a calling method capable of detecting a problem of the vehicle call device may be provided while controlling the cost increase of the vehicle call device. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Other objects, features, and advantages of the present invention will become more apparent from the following description when read in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic drawing showing an exemplary configuration of an emergency call system; 
         FIG. 2  is a block diagram showing an exemplary configuration of the emergency call device according to a first embodiment of the present invention; 
         FIG. 3  is a schematic sequence diagram showing a procedure by which an emergency service center (herein after simplified as a “center”) determines whether the emergency call device in communication with the center has a problem according to the first embodiment of the present invention; 
         FIG. 4  is a block diagram showing an exemplary configuration of the emergency call system according to a second embodiment of the present invention; 
         FIG. 5  is a schematic sequence diagram showing a procedure by which the center determines whether the emergency call device in communication with the center has a problem according to the second embodiment of the present invention; 
         FIG. 6  is a block diagram showing an exemplary configuration of the emergency call device according to a third embodiment of the present invention; and 
         FIG. 7  is a schematic sequence diagram showing a procedure by which the center determines whether the emergency call device in communication with the center has a problem according to the third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Exemplary embodiments of the present invention are described below with reference to the accompanying drawings. 
     Embodiment 1 
     In this embodiment, an emergency call system  100  turns OFF an echo canceller in an emergency call device  50  mounted in a vehicle so that an operator of an emergency service center (hereinafter may be referred to as just a “center”) can determine whether the emergency call device  50  has a problem or an occupant of the vehicle is unable to respond to the operator&#39;s call because of the injury. 
       FIG. 1  schematically shows an exemplary configuration of the emergency call system  100 . As shown in  FIG. 1 , the emergency call system  100  generally includes a vehicle  11 , a base station  12 , and a network  13  forming a cell phone network or a public telephone line network, and an emergency service center (or simplified as a “center”)  14 . In an emergency situation, the vehicle  11  and the center  14  start communications with each other through the base station  12  and the network  13 , so that an occupant of the vehicle  11  and an operator of the center  14  can talk with each other. Further, when it becomes necessary, the operator of the center  14  makes contact with the fire department  15 , the police  16 , or an emergency road service provider  17  (herein after referred to as the “fire department and the like”) to ask then to immediately go to the site of the vehicle  11 . It should be noted that a voice recognition system may be used in the center  14  so that the center  14  can recognize the voice of the occupant of the vehicle  11  and determine whether the emergency call device  50  has a problem. However, in the embodiments, it is assumed that the operator of the center  14  is in communication with the occupant of the vehicle  11  and the fire department and the like. 
       FIG. 2  is a block diagram showing an exemplary configuration of the emergency call device  50  according to a first embodiment of the present invention. As shown in  FIG. 2 , the emergency call device  50  includes a voice processing section  24  which controls the emergency call device  50 . The emergency call device  50  further includes a GPS (Global Positioning System) receiver  21 , an airbag switch  22 , a communication start switch  23 , a communication device  25 , a speaker  26 , and a microphone  27 , each being connected to the voice processing section  24 . The GPS receiver  21  receives radio waves from GPS satellites for calculating the position of the vehicle  11 . The airbag switch  22  detects an operation of the airbags housed in the driver&#39;s seat, a front passenger&#39;s seat, and the like. The communication start switch  23  is turned ON by an occupant of the vehicle  11  to start communications with the center  14 . The communication device  25  is used to communicate with the center  14 . The speaker  26  outputs voice sounds, and the microphone  27  converts the voice sound into an electrical signal. 
     The voice processing section  24  is configured as a computer system that includes a CPU, a ROM, a RAM, and input/output interfaces, and includes an echo canceller controlling section  31  realized by executing a program by the CPU. The voice processing section  24  further includes an interface section  32 , an echo canceller section  29 , and a voice signal level detecting section  30 . The interface section  32  inputs and outputs a received voice signal and a transmitted voice signal. The echo canceller section  29  cancels an echo. The voice signal level detecting section  30  detects a voice signal level of the transmitted voice signal. 
     The communication device  25  may be a data communication unit having a voice communication function or may be a cell phone of the occupant of the vehicle  11 . When the communication device  25  performs data communications, the communication device  25  establishes a data link connection in accordance with the PPP (Point-To-Point) protocol or the like and can transmit and receive data through the network  13 , using an upper layer protocol such as TCP/IP (Transmission Control Protocol/Internet Protocol). Through the communication device  25 , the positional information of the vehicle  11  and the like may be transmitted to the center  14 . 
     The interface section  32  establishes a connection with the communication device  25  based on a wired connection removably attached to the communication device  25  or a wireless connection with the communication device  25  so that the interface section  32  receives the received voice signal transmitted from the communication device  25  and transmits the transmitted voice signal to the communication device  25 , the transmitted voice signal being generated by the voice processing section  24 . In the wireless communications, the Bluetooth (registered trademark) communication standards may be used for receiving the received voice signals and transmitting the transmitted voice signals. 
     Further, the interface section  32  is equipped with an input device such as a switch so that a user can operate the input device to transmit an On-hook/Off-hook instruction to the communication device  25  for the communication device  25  to perform an On-hook/Off-hook operation. 
     Further, in an emergency situation, when the airbag switch  22  detects an operation of the airbag, or when the communication start switch  23  is turned ON, the interface section  32  sets a telephone number previously registered as the destination telephone number to be in communication with the center  14 . In addition, an emergency situation may be detected by using an acceleration sensor or the like. 
     The communication device  25  transmits the received voice signal to the interface section  32 , the received voice signal being received from the operator through the network  13 . Further, the communication device  25  transmits the transmitted voice signal to the operator through the network  13 , the transmitted voice signal being received from the interface section  32 . 
     The voice processing section  24  further includes a received voice amplifier  33  and a transmitted voice amplifier  34 . The received voice amplifier  33  amplifies the received voice signal transmitted from the interface section  32  and drives the speaker  26  to output the received voice in the vehicle  11 . As the speaker  26 , a speaker for an audio system or a navigation system mounted in the vehicle  11  may be used. Preferably, for example, the speaker  26  is disposed in the driver&#39;s door and directed inward. 
     The transmitted voice amplifier  34  transmits a voice sound in the vehicle  11  collected by the microphone  27  to the echo canceller section  29  as the transmitted voice signal. The echo canceller section  29  cancels an echo component of the received voice included in the transmitted voice signal, and transmits the signal after the cancellation to the communication device  25  through the interface section  32 . The microphone  27  may be installed in the middle part of a handle, an instrument panel, the A-pillar on the driver&#39;s side, or the like, and has directional characteristics so as to collect a driver&#39;s voice with higher sensitivity. 
     The echo canceller section  29  includes a filter  35  and a mixer  36 . The filter  35  calculates a pseudo echo signal. The pseudo echo signal may be generated using a known technique in which, for example, the phase of the received voice signal is inverted by 180 degrees and the inverted signal is modified in accordance with the expected changes based on the ambient acoustic characteristics of the vehicle  11 . The mixer  36  subtracts the pseudo echo signal calculated by the filter  35  from the transmitted voice signal from the transmitted voice amplifier  34 , and transmits the output of the mixer  36  to the interface section  32 . 
     The echo canceller controlling section  31  can turn OFF an echo cancelling function of the echo canceller section  29 . Usually, the echo canceller section  29  is turned ON so that the echo cancelling function is activated. Therefore, when the echo canceller section  29  is turned OFF, the operator of the center  14  will be able to hear his/her own voice with little delay because the voice of the operator output from the speaker  26  is directly input into the microphone  27  and returned to the center  14  without being echo-cancelled by the mixer  36 . 
     In the emergency call device  50  in  FIG. 2 , an operator of the center  14  may easily determine whether the emergency call device  50  has a problem or the occupant of the vehicle  11  is unable to talk to the operator due to his/her injury. This is because when the operator of the center  14  can hear his/her echo-back voice but cannot hear any voice of the occupant of the vehicle  11 , the operator can easily notice that the occupant of the vehicle  11  is unable to talk to the operator due to the injury. On the other hand, when the operator cannot hear his/her own echo-back voice, it may be obvious that the emergency call device  50  has a problem. However, it is still uncertain whether the occupant of the vehicle  11  is in an emergency situation such as being injured in that the occupant has not responded to the operator. Therefore, another method (such as taking a picture inside the vehicle  11  and taking the occupant&#39;s pulse) should be used. Further, the echo canceller section  29  is usually included as standard equipment in the environment where a hands-free call can be performed and in cell phones. Therefore, it becomes possible to determine whether the emergency call device  50  has a problem with minimum additional functions. 
     In this embodiment, the emergency call device  50  capable of automatically turning OFF the echo cancelling function of the echo canceller section  29  is described. In the initial setting, the echo cancelling function of the echo canceller section  29  is turned ON (activated). Therefore, when the occupant of the vehicle  11  is able to talk to the operator, it is preferable to keep the echo cancelling function of the echo canceller section  29  turned ON because the operator can hear what the occupant says more clearly. However, when the occupant of the vehicle  11  is unable to talk to the operator, it is preferable that the emergency call device  50  be able to automatically turn OFF (deactivate) the echo cancelling function of the echo canceller section  29 . 
     For example, when the occupant of the vehicle  11  is unable to talk to the operator, the voice signal level should become lower than a prescribed signal level. In this embodiment, therefore, the echo canceller controlling section  31  turns OFF the echo cancelling function of the echo canceller section  29  based on the voice signal level of the transmitted voice signal. 
       FIG. 3  is a schematic sequence diagram showing a procedure by which the operator of the center  14  determines whether the emergency call device  50  in communication with the center  14  has a problem. In the procedure shown in  FIG. 3 , the emergency call device  50  of the vehicle  11  starts the communications with the emergency service center (center)  14  when the airbag switch  22  detects an operation of the airbag or when the communication start switch  23  is turned ON (step S 10 ). The operator of the center  14  responds to the connection from the vehicle  11  and calls out to an occupant of the vehicle  11  (step S 20 ). 
     After the connection with the center  14  is established, the voice signal level detecting section  30  determines whether the voice signal level of the transmitted voice signal is equal to or greater than a prescribed signal level. In this case, the transmitted voice signal includes an echo component of the received voice from the operator. Therefore, the voice signal level detecting section  30  detects the voice signal level of the transmitted voice signal that is transmitted from the mixer  36  where the pseudo echo signal is subtracted from the transmitted voice signal from the transmitted voice amplifier  34 , and then determines whether the voice signal level of the transmitted voice signal is equal to or greater than a prescribed signal level (step S 30 ). It should be noted that the voice signal level may be monitored by detecting the voltage value of the voice signal level. 
     When it is determined that the voice signal level of the transmitted voice signal is equal to or greater than a prescribed signal level (YES in step S 30 ), it is assumed that the occupant of the vehicle  11  is responding to the operator of the center  14 . Therefore, the echo canceller controlling section  31  keeps the echo cancelling function of the echo canceller section  29  turned ON (step S 40 ). On the other hand, when it is determined that the voice signal level of the transmitted voice signal is less than a prescribed signal level (NO in step S 30 ), the echo canceller controlling section  31  turns OFF the echo cancelling function of the echo canceller section  29  (step S 50 ). 
     The operator of the center  14  may repeatedly call out to the occupant of the vehicle  11  as long as necessary to determine whether a voice of the occupant of the vehicle  11  can be heard (step S 60 ). When it is determined that the occupant of the vehicle  11  responds to the operator of the center  14  and the voice of the occupant of the vehicle  11  can be heard (YES in step S 60 ), the operator of the center  14  performs a general process of calling for an ambulance and the like in accordance with the information of the damage level of the vehicle  11  and/or the injury level of the occupant of the vehicle  11  heard from the occupant of the vehicle  11  (step S 90 ). 
     On the other hand, when it is determined that the occupant of the vehicle  11  does not respond to the operator of the center  14  and the voice of the occupant of the vehicle  11  cannot be heard (NO in step S 60 ), the echo cancelling function of the echo canceller section  29  is turned OFF (deactivated) because the voice signal level of the transmitted voice signal is less than the prescribed signal level. Therefore, if the microphone  27  of the emergency call device  50  does not have a problem, the voice of the operator of the center  14  included in the transmitted voice signal is returned to the center  14 . 
     The operator of the center  14  determines whether his/her own returned voice can be heard (step S 70 ). When it is determined that the his/her own returned voice can be heard (YES in step S 70 ), it is assumed that the occupant of the vehicle  11  is injured because of no response from the occupant of the vehicle  11  even in the situation where neither the speaker  26  nor the microphone  27  has a problem, and the operator of the center  14  may call for an ambulance (step S 80 ). 
     On the other hand, when it is determined that the his/her own returned voice cannot be heard (NO in step S 70 ), it is assumed that at least either the speaker  26  or the microphone  27  has a problem (step S 110 ). Therefore, a method other than the method of communicating with the occupant of the vehicle  11  is to be used for confirming the situation of the occupant of the vehicle  11  (step S 120 ). It should be noted that when the echo canceller controlling section  31  turns OFF the echo cancelling function of the echo canceller section  29 , the information item indicating that the echo canceller section  29  is being turned OFF may be transmitted to the center  14 . 
     According to this embodiment of the present invention, by turning OFF the echo cancelling function of the echo canceller section  29 , it becomes possible to determine whether the emergency call device  50  has a problem. Further, the element serving as the echo canceller section  29  is generally included in a vehicle as standard equipment, and monitoring the voice signal level of the transmitted voice signal can be easily performed. Therefore, it is possible to determine whether the emergency call device  50  has a problem with minimum additional cost. 
     Embodiment 2 
     In this embodiment, the emergency call system  100  in which the echo canceller controlling section  31  can turn OFF the echo cancelling function of the echo canceller section  29  based on a signal from the center  14  is described. For example, when the occupant of the vehicle  11  is unable to talk due to his/her injury, it is possible to assume that the occupant of the vehicle  11  is unable to respond to an operator&#39;s call. However, when the echo cancelling function of the echo canceller section  29  is automatically turned OFF as described in the first embodiment, the operator of the center  14  may have to wait for a certain period of time until the echo cancelling function of the echo canceller section  29  is turned OFF, which may cause a delay in determining whether, for example, the emergency call device  50  has a problem. In addition, in a case of the first embodiment, when the level of the noise generated from the vehicle  11  or the ambient noise is greater than the prescribed level, the echo cancelling function of the echo canceller section  29  is not turned OFF. 
     Further, when it is possible for the operator of the center  14  to remotely turn OFF the echo cancelling function of the echo canceller section  29  of the emergency call device  50 , the operator of the center  14  is able to grasp when the echo cancelling function of the echo canceller section  29  is turned OFF. As a result, the operator of the center  14  may determine whether the emergency call device  50  has a problem more easily compared with the case where the operator of the center  14  has to wait until the echo cancelling function of the echo canceller section  29  is automatically turned OFF. 
       FIG. 4  is a block diagram showing an exemplary configuration of the emergency call system  100  according to a second embodiment of the present invention. It should be noted that the same reference numerals are used in  FIG. 4  for denoting the same elements in  FIG. 2 , and the descriptions of the same elements are omitted. As shown in  FIG. 4 , the emergency service center (“center”)  14  includes an input device  141  and an echo canceller operation signal transmitting section  142 . The input device  141  may be a mouse, a keyboard, or the like for operating a computer of the center  14 , and the operator of the center  14  uses the input device  141  to operate application software executed by the computer. When operating the computer of the center  14  to transmit an echo canceller operation signal to the vehicle  11 , the operator of the center  14  uses a prescribed operations menu of the application software so that the echo canceller operation signal transmitting section  142  transmits the echo canceller operation signal to the vehicle  11  to turn OFF the echo cancelling function of the echo canceller section  29 . In this case, more specifically, the echo canceller operation signal transmitting section  142  transmits the echo canceller operation signal to the communication device  25  specified by the telephone number or the like using an NIC (Network Interface Card) or the like. The echo canceller controlling section  31  in the emergency call device  50  turns OFF the echo cancelling function of the echo canceller section  29  based on the echo canceller operation signal received by the communication device  25 . 
       FIG. 5  is a schematic sequence diagram showing a procedure by which the operator of the center  14  determines whether the emergency call device  50  in communication with the center  14  has a problem. In the procedure shown in  FIG. 5 , the emergency call device  50  of the vehicle  11  starts the communication with the emergency service center (center)  14  when the airbag switch  22  detects an operation of the airbag or when the communication start switch  23  is turned ON (step S 10 ). The operator of the center  14  responds to the connection from the vehicle  11  and calls out to the occupant of the vehicle  11  (step S 20 ). 
     The operator of the center  14  determines whether a voice of the occupant of the vehicle  11  as a response to the operator&#39;s call can be heard (step S 210 ). When it is determined that the voice of the occupant of the vehicle  11  can be heard (YES in step S 210 ), the operator of the center  14  performs a general process of calling for an ambulance and the like in accordance with the information of the damage level of the vehicle  11  and/or the injury level of the occupant of the vehicle  11  heard from the occupant of the vehicle  11  (step S 270 ). 
     On the other hand, when it is determined that the occupant of the vehicle  11  does not respond to the operator&#39;s call and the voice of the occupant of the vehicle  11  cannot be heard (NO in step S 210 ), the operator of the center  14  operates the input device  141  to cause the echo canceller operation signal transmitting section  142  to transmit the echo canceller operation signal (step S 220 ). 
     When the communication device  25  of the emergency call device  50  receives the echo canceller operation signal, the echo canceller controlling section  31  in the emergency call device  50  turns OFF the echo cancelling function of the echo canceller section  29  (step S 280 ). By doing this, the operator&#39;s voice signal included in the voice signal from the center  14  is returned to the center  14 , unless the microphone  27  in the emergency call device  50  has a problem. 
     Next, the operator of the center  14  determines whether the operator&#39;s own voice can be heard (step S 230 ). When it is determined that the operator&#39;s own voice can be heard (YES in step S 230 ), it is possible that the occupant of the vehicle  11  is injured because of no response from the occupant of the vehicle  11  even in the situation where neither the speaker  26  nor the microphone  27  has a problem, and the operator of the center  14  may call for an ambulance (step S 240 ). 
     On the other hand, when it is determined that the own returned voice cannot be heard (NO in step S 230 ), it is possible that at least either the speaker  26  or the microphone  27  has a problem (step S 250 ). Therefore, a method other than the method of communicating with the occupant of the vehicle  11  is to be used for confirming the situation of the occupant of the vehicle  11  (step S 260 ). 
     According to this embodiment of the present invention, by turning OFF the echo cancelling function of the echo canceller section  29 , it becomes possible to determine whether the emergency call device  50  has a problem. 
     Further, by turning OFF the echo canceller section  29  from the center  14 , the operator may independently determine whether the emergency call device  50  has a problem. It should be noted that after adding the configuration according to this second embodiment to the configuration according to the first embodiment, the echo cancelling function of the echo canceller section  29  may be turned OFF based on the voice signal level of the transmitted voice signal and the echo canceller operation signal. 
     Embodiment 3 
     In first and second embodiments described above, it is determined whether the emergency call device  50  has a problem based on whether the operator of the center  14  can hear the operator&#39;s own voice when the echo cancelling function of the echo canceller section  29  is turned OFF. On the other hand, in this embodiment, the emergency call system  100  is described in which whether the emergency call device  50  has a problem may be determined without turning OFF the echo cancelling function of the echo canceller section  29 . 
     When the operator of the center  14  can hear any sound from vehicle  11 , the operator can determine that at least the microphone  27  of the emergency call device  50  does not have a problem. In this embodiment, as the sound, a prescribed music sound (hereinafter referred to as “BGM”) output from the speaker  26  to the vehicle  11  is used. Any music may be used as the “BGM”. However, it is preferable that the BGM include a range different from the voice range of the occupant of the vehicle  11  so that the operator can easily distinguish the BGM from the voice of the occupant of the vehicle  11 . 
       FIG. 6  is a block diagram showing an exemplary configuration of the emergency call device  50  according to a third embodiment of the present invention. It should be noted that the same reference numerals are used in  FIG. 6  for denoting the same elements in  FIG. 2 , and the descriptions of the same elements are omitted. As shown in  FIG. 6 , the emergency call device  50  includes a BGM synthesis processing section  37  and does not include the echo canceller controlling section  31  because, in this embodiment, it is not necessary to control the echo canceller section  29  to turn OFF the echo cancelling function of the echo canceller section  29 . 
     The BGM synthesis processing section  37  combines the voice signal received by the interface section  32  with a BMG signal, and outputs the combined (synthesized) signal to the speaker  26  so that the sound of the synthesized signal is output from the speaker  26 . As the BGM synthesis processing section  37 , the audio device generally mounted in a vehicle as standard equipment may be used. By doing this, the cost increase may be minimized. 
     In this embodiment, the received voice from the operator of the center  14  and the BGM are output to the vehicle  11 . However, the received voice signal is cancelled by the echo canceller section  29 . Therefore, when the occupant of the vehicle  11  does not respond to the operator&#39;s call, the interface section  32  transmits only BGM to the communication device  25 . 
     As a result, when the operator of the center  14  hears the BGM, the operator of the center  14  may determine that the microphone  27  of the emergency call device  50  does not have a problem. Further, when the occupant of the vehicle  11  responds to the operator&#39;s call, the operator of the center  14  may easily hear the voice of the occupant of the vehicle  11  which can be distinguished from the BGM because the echo cancelling function of the echo canceller section  29  is kept turned ON. 
       FIG. 7  is a schematic sequence diagram showing a procedure by which the operator of the center  14  determines whether the emergency call device  50  in communication with the center  14  has a problem. It should be noted that the same step numbers are used in  FIG. 7  for denoting the same step numbers in  FIG. 3 . 
     In the procedure shown in  FIG. 7 , the emergency call device  50  of the vehicle  11  starts the communications with the emergency service center (center)  14  when the airbag switch  22  detects an operation of the airbag or when the communication start switch  23  is turned ON (step S 10 ). The operator of the center  14  responds to the connection from the vehicle  11  and calls out to the occupant of the vehicle  11  (step S 20 ). Then, the BGM synthesis processing section  37  in the emergency call device  50  starts a synthesis process by combining the received voice signal and the BGM signal (step S 31 ). In this case, it should be noted that even if no voice signal is received, the synthesis process is performed by the BGM synthesis processing section  37 . 
     The operator of the center  14  may repeatedly call out to the occupant of the vehicle  11  to determine whether a voice from the occupant of the vehicle  11  can be heard (step S 60 ). When it is determined that the voice of the occupant of the vehicle  11  can be heard (YES in step S 60 ), the operator of the center  14  performs a general process of calling for an ambulance and the like in accordance with the information of the damage level of the vehicle  11  and/or the injury level of the occupant of the vehicle  11  heard from the occupant of the vehicle  11  (step S 90 ). 
     On the other hand, when it is determined that the occupant of the vehicle  11  does not respond to the operator of the center  14  and the voice of the occupant of the vehicle  11  cannot be heard (NO in step S 60 ), the operator of the center  14  determines whether the BGM can be heard (step S 71 ). When it is determined that the BGM can be heard (YES in step S 71 ), it is possible to assume that the occupant of the vehicle  11  is injured because of no response from the occupant of the vehicle  11  even in the situation where neither the speaker  26  nor the microphone  27  has a problem, and the operator of the center  14  may call for an ambulance (step S 80 ). 
     On the other hand, when it is determined that the BGM cannot be heard (NO in step S 71 ), it is possible that at least either speaker  26  or the microphone  27  has a problem (step S 110 ). Therefore, a method other than the method of communicating with the occupant of the vehicle  11  is to be used for confirming the situation of the occupant of the vehicle  11  (step S 120 ). 
     According to this embodiment of the present invention, simply by outputting the BGM to the vehicle  11 , it becomes possible to determine whether the emergency call device  50  has a problem. Therefore, the cost increase may be minimized. Further, in this embodiment, the echo cancelling function of the echo canceller section  29  is not turned OFF. Therefore, it becomes possible to hear the voice of the occupant of the vehicle  11  clearly when the occupant of the vehicle  11  responds to the operator&#39;s call. 
     Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teachings herein set forth.