Abstract:
Acoustic input and output devices are made to operate properly according to communication processing. A portable communication terminal includes an acoustic input-output unit including a plurality of acoustic input elements to conduct acoustic inputting and acoustic output elements to conduct acoustic outputting, a communication processing unit which selectively executes mutually different communication processes using at least one of the elements included in the acoustic input-output unit, and an acoustic processing unit which determines an order of operation of the acoustic input-output unit to be conducted by the elements according to a communication process executed by the communication processing unit and gives the determined operation order to the acoustic input-output unit.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a portable communication terminal such as a portable telephone or a schedule management terminal. In particular, the present invention relates to a portable communication terminal having a plurality of acoustic input-output devices.  
         [0002]     There is a conventional technique of attempting to increase the output sound quality by providing a plurality of speakers in a portable communication terminal. As a technique of this kind, for example, there is a technique described in Japanese Patent Application Laid-Open Publication No. 2002-111817. According to this technique, at least two speakers are provided in a portable terminal, and these speakers are made to operate simultaneously so that sounds reproduced by the speakers assist each other.  
         [0003]     In recent portable telephones, portable telephones having a plurality of communication functions, such as dynamic image recording, reproducing, transmitting and receiving functions, or the so-called TV telephone function which makes it possible to talk while reproducing a dynamic image, besides a typical talking function are spread. When using such a portable telephone, the use form of the user differs according to the communication function. For example, the terminal is brought into contact with an ear at the time of ordinary talk, whereas the user faces the terminal at the time of use of video phone.  
         [0004]     At the time of ordinary talk when the terminal is held to an ear, however, a smaller acoustic output can cope with it as compared with the time of use of video phone. When using the above-described conventional technique in which all of a plurality of speakers are brought into operation, therefore, there is rather a fear that wasteful power will be dissipated. Furthermore, when using video phone and when recording a dynamic image, it is desired to catch more sounds in order to conduct clear acoustic reproduction.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention has been achieved to solve the problems. An object of the present invention is to provide portable communication terminals capable of smoothly executing acoustic processing respectively suitable for various communication functions.  
         [0006]     A portable communication terminal according to the present invention includes an acoustic input-output unit including a plurality of acoustic input means to conduct acoustic inputting and acoustic output means to conduct acoustic outputting, a communication processing unit which selectively executes mutually different communication processes using at least one of the means included in the acoustic input-output unit, and an acoustic processing unit which determines an order of operation of the acoustic input-output unit to be conducted by the means according to a communication process executed by the communication processing unit and gives the determined operation order to the acoustic input-output unit.  
         [0007]     Another portable communication terminal according to the present invention includes an acoustic input-output unit including acoustic input means to conduct acoustic inputting and a plurality of acoustic output means to conduct acoustic outputting, a communication processing unit which selectively executes mutually different communication processes using at least one of the means included in the acoustic input-output unit, and an acoustic processing unit which determines an order of operation of the acoustic input-output unit to be conducted by the means according to a communication process executed by the communication processing unit, and gives the determined operation order to the acoustic input-output unit.  
         [0008]     According to the portable communication terminal according to the present invention, the acoustic input and output devices are controlled in operation based on communication processing executed in the terminal. Therefore, an acoustic system suitable for the communication processing can be provided. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a block diagram showing a configuration of a portable telephone in first and second embodiments according to the present invention;  
         [0010]      FIGS. 2A and 2B  are exterior views of a portable telephone in first and second embodiments;  
         [0011]      FIG. 3  is a flow chart showing an operation procedure in a first embodiment;  
         [0012]      FIG. 4  is a flow chart showing an operation procedure in a second embodiment;  
         [0013]      FIG. 5  is a block diagram showing a configuration of a portable telephone in a third embodiment according to the present invention;  FIGS. 6A and 6B  are exterior views of a portable telephone in a third embodiment;  
         [0014]      FIG. 7  is a flow chart showing an operation procedure in a third embodiment;  
         [0015]      FIG. 8  is a block diagram showing a configuration of a portable telephone in fourth and fifth embodiments according to the present invention;  
         [0016]      FIG. 9  is an exterior view of a portable telephone in a fourth embodiment;  
         [0017]      FIG. 10  is a flow chart showing an operation procedure in a fourth embodiment;  
         [0018]      FIGS. 11A and 11B  are exterior views of a portable telephone in a fifth embodiment; and  
         [0019]      FIG. 12  is a flow chart showing an operation procedure in a fifth embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     First Embodiment  
       [0020]     Hereafter, an embodiment of the present invention will be described in detail with reference to the drawings.  FIG. 1  is a block diagram showing a configuration of an embodiment of a portable communication terminal according to the present invention. As shown in  FIG. 1   i  a portable telephone  101  which is a portable communication terminal in the embodiment includes an acoustic input-output unit  10  having a plurality of acoustic input means and a plurality of acoustic output means, a communication processing unit  20  which selectively executes communication processing such as ordinary talking using only voice, talking using video phone, dynamic image recording and reproduction, and voice-music reproduction, and an acoustic processing unit  50  which gives an operation order to the acoustic input-output unit  10  according to communication processing in the communication processing unit  20 .  
         [0021]     The acoustic input-output unit  10  includes an SPK  11 , which is a speaker, and a SPK drive unit  12  serving as acoustic output means, a REC  13 , which is a receiver fulfilling a talking receiver function, and a REC drive unit  14  serving as the acoustic output means in the same way, microphones MIC  15   a  and MIC  15   b  each serving as acoustic input means, input-output switches  16   a  and  16   b  which conduct input-output switching described later on the MIC  15   a  and MIC  15   b , and an MIC input detecting unit  17  which detects sounds input via the MIC  15   a  and MIC  15   b.    
         [0022]     The communication processing unit  20  includes a transmitting and receiving ANT (antenna)  21  which transmits and receives a radio signal of the portable telephone  101 , a portable telephone radio unit  22  which conducts modulation and demodulation of a radio signal, a system processing unit  23  which conducts portable telephone signal processing, a CPU  24 , keys  25  serving as an operation input unit, a key detecting unit  26  which detects input conducted by using the keys  25 , an LCD  27  and an LCD driving unit  28  which fulfill a display function, a ROM  29  which stores a program, and a RAM  30  which stores data.  
         [0023]     The MIC  16   a  and MIC  15   b  in the present embodiment fulfill the function of serving as the acoustic output means such as the SPK  11 , besides the function of serving as the acoustic input means. Specifically, the MIC  15 A and MIC  15 B are made to operate as microphones or speakers according to the communication processing such as talking or image recording. This control is implemented by the acoustic processing unit  50  giving an operation order to the SPK drive unit  12  and the MICA input detecting unit  17 , and the input-output switches  16   a  and  16   b  conducting acoustic signal connection switching. By thus making the MIC  15   a  and the MIC  15   b , which originally serve as the acoustic input means, function as the acoustic output means as well, additional disposition of speaker devices becomes unnecessary and effective use of the design space in the portable telephone  101  becomes possible.  
         [0024]     As each of devices which can fulfill the acoustic input and output functions like the above-described MICs  15   a  and  15   b , for example, a dynamic microphone which is a kind of microphone can be used. As conventionally known, the dynamic microphone has a coil connected to an acoustic plate disposed in a magnetic field of a magnet. Vibration of the acoustic plate is transmitted to the coil to vary the magnetic field. As a result, a current of the input signal flows through the coil.  
         [0025]     On the other hand, in conventional speakers, there is a speaker having a configuration similar to that of the above-described dynamic microphone. In the case of this speaker, the acoustic plate connected to the coil is vibrated by a magnetic field generated by the current flowing through the coil, and a sound is output to the outside. By controlling an operation order given to the dynamic microphone, therefore, this microphone implements selective acoustic input and output. By the way, it is generally known that such a technique is applied to, for example, a speaker microphone of a radio machine. In the present embodiment, this technique is used in the MIC  15   a  and MIC  15   b  in the portable telephone  101 .  
         [0026]      FIGS. 2A and 2B  schematically show exterior views of the portable telephone  101  in the embodiment. As shown in  FIG. 2A , the portable telephone  101  is a folding telephone in which a casing upper part  101   a  including the REC  13  and the LCD  27  is connected to a casing lower part  101   b  including keys  25  by a hinge mechanism  101   c . The MIC  15   a  and MIC  15   b  described above are provided on the casing lower part  101   b . As shown in  FIG. 2B , the SPK  11  is provided on a surface of the casing upper part  101   a , i.e., a surface facing in opposite directions a face of the LCD  27 .  
         [0027]     An operation procedure of the portable telephone  101  in the embodiment will now be described with reference to a flow chart shown in  FIG. 3 . When the portable telephone  101  is started (step S 1 ), the acoustic processing unit  50  sets the MICs  16   a  and  15   b  to a microphone operation mode and the SPK  11  to a monaural speaker (left+right) operation mode in the SPK drive unit  12 , the MIC input detecting unit  17 , and the input-output switches  16   a  and  16   b  as initialization processing for the acoustic input-output unit  10  (step S 2 ). Although not illustrated in  FIG. 3 , the REC  13  is in a receiver operation mode.  
         [0028]     When the MICs  15   a  and  15   b  are operated in the microphone operation mode, operation parameters for conducting acoustic inputting are set in them. At the time of operation in the receiver operation mode, operation parameters for conducting voice output with a volume suitable for receiving operation, in which the user brings the REC  13  into contact with an ear, are set. At the time of operation in a speaker operation mode, parameters for outputting voice with a volume suitable for the user facing the portable telephone  101  as in video phones are set. In this speaker operation mode, a greater clearer voice output as compared with the above-described receiver operation mode is demanded. Accordingly, a greater output gain is set, and a low frequency band in frequency characteristics is set to become high.  
         [0029]     When the above-described initialization processing is completed, the CPU  24  in the communication processing unit  20  monitors the operation state of the portable telephone  101 . According to the state, the CPU  24  specifies an operation mode of the acoustic input-output unit  10  to the acoustic processing unit  50  (step S 3 ).  
         [0030]     For example, when the user starts typical talking, i.e., talking using only voice by using the portable telephone  101  (step S 3   a ), the CPU  24  orders the acoustic processing unit  50  to bring one of the MIC  15   a  and the MIC  15   b  operate into the microphone operation mode and bring the other of the microphones and the SPK  11  into an OFF mode, i.e., stop their operation (step S 4 ). At the time of ordinary talking, the MICs  15   a  and  15   b  are close to the mouth of the user so as to capture an uttered sound easily, and consequently one of the microphones is brought into operation whereas the other is stopped. As a result, power consumption can be suppressed.  
         [0031]     When starting talking on video phone (step S 3   b ), the MIC  15   a  is made to operate in a stereo (left) microphone operation mode and the MIC  15   b  is made to operate in a stereo (right) microphone operation mode, whereas the SPK  11  is made to operate in the speaker operation mode (step S 5 ). At this time, operation parameters for stereo acoustic input are set with respect to the MICs  15   a  and  15   b . As a result, it becomes possible for the portable telephone  101  to capture more voices by using the MICs  15   a  and  15   b  and capture voice data providing feeling of presence.  
         [0032]     When recording a moving image is started (step S 3   c ), the MIC  15   a  is set to the stereo (left) microphone operation mode and the MIC  15   b  is set to the stereo (right) microphone operation mode. Thereby, stereo acoustic inputting similar to that described above is conducted. Since the external acoustic outputting is unnecessary at the time of image recording, the SPK  11  is set to the OFF mode (step S 6 ).  
         [0033]     When reproducing a moving image or reproducing already recorded voice and delivered music (steps S 3   d  and S 3   e ), the MIC  15   a  is set to the stereo (left) speaker operation mode and the MIC  15   b  is set to the stereo (right) speaker operation mode whereas the SPK  11  is set to the monaural (left+right) speaker operation mode (step S 7 ). According to the setting, the MICs  15   a  and  15   b  operate as means that outputs the sound to the outside together with the SPK  11  instead of operating as the original acoustic input means.  
         [0034]     Operation switching of the MICs  15   a  and  15   b  is executed by switching the connection of the MICs  15   a  and  15   b  from the MIC input detecting unit  17  to the SPK drive unit  12  with the input-output switches  16   a  and  16   b  as described above. According to the above-described setting, stereo acoustic outputting using the MICs  15   a  and  15   b  is executed besides the acoustic outputting using the SPK  11 . As a result, voice and music can be provided for the user with feeling of presence. The so-called multi-speaker system can be constructed by thus utilizing the MICs  15   a  and  15   b.    
         [0035]     Each time any communication processing described above is finished (yes at step S 8 ), the CPU  24  returns to the step S 3  in order to monitor the state again.  
       Second Embodiment  
       [0036]     In the first embodiment described above, any one of the MICs  15   a  and  15   b  is set to the OFF mode (step S 4 ) at the time of ordinary talking (step S 3   a ). Alternatively, the microphone to be set to the OFF mode may be determined on the basis of a predetermined condition. Its procedure will now be described with reference to a flow chart shown in  FIG. 4 . In  FIG. 4 , steps denoted by the same symbols as those in  FIG. 3  according to the first embodiment are like those in the first embodiment, and description of them will be omitted here.  
         [0037]     As the initialization processing at the time of start-up (step S 21 ), the portable telephone  101  brings the MICs  15   a  and  15   b  into the OFF mode as shown in  FIG. 4  (step S 22 ). Then, the MICs  15   a  and  15   b  is set to the microphone operation mode at the time of ordinary talking (step S 3   a ).  
         [0038]     When talking is started (step S 3   a ), the acoustic processing unit  50  compares input levels of the MICs  15   a  and  15   b  detected by the MIC input detecting unit  17  with each other. If the input level of the MIC  15   a  is higher than that of the MIC  15   b  (yes at step S 24 ), the MIC  15   b  is set to the OFF mode to stop its operation and the MIC  15   a  is made to operate in the microphone operation mode (step S 25 ). If the input level of the MIC  15   a  is lower than that of the MIC  15   b  (no at the step S 24 ), the MIC  15   a  is set to the OFF mode and the MIC  15   b  is made to operate in the microphone operation mode (step S 26 ). At the time of video phone (step S 3   b ) as well, one of the microphones can be adapted to be stopped in the same way as the above-described procedure (steps S 27  to S 30 ).  
         [0039]     According to the procedure in the second embodiment, the power dissipation of the portable telephone  101  can be suppressed and a microphone that implements a more favorable voice input can be automatically selected.  
       Third Embodiment  
       [0040]      FIG. 5  is a block diagram showing a configuration of a portable telephone  103  in a third embodiment. The portable telephone  103  is a folding terminal in the same way as the portable telephone  101  described with reference to  FIG. 1 . Besides the configuration of the portable telephone  101 , the portable telephone  103  includes a MIC  15   c  which is a microphone serving as the acoustic input means, and an opening and closing detecting unit  31  which detects the open/close state of the casing. As the opening and closing detecting unit  31 , for example, a pressure sensor provided on the inside of folding near a hinge mechanism in a typical folding portable telephone can be used.  
         [0041]      FIGS. 6A and 6B  schematically show exterior views of the portable telephone  103 . As shown in  FIG. 6A , the portable telephone  103  includes the MIC  15   a , MIC  15   b  and SPK  11  on a surface of a casing upper part  103   a , and a MIC  15   c  on a face of a casing lower part  103   b  coplanar with the keys  25 .  FIG. 6B  shows the state in which the casing of the portable telephone  103  is closed, i.e., the casing upper part  103   a  is laid on the face of the keys  25  in the casing upper part  103   a.    
         [0042]     An operation procedure of the portable telephone  103  will now be described with reference to a flow chart shown in  FIG. 7 . In  FIG. 7 , steps denoted by the same symbols as those in  FIG. 3  according to the first embodiment are like those in the first embodiment, and description of them will be omitted here. In the initialization processing at the time of start (step S 31 ), the portable telephone  103  brings the MICs  15   a  and  15   b  into the OFF mode and sets the MIC  15   c  to the MIC operation mode (step S 32 ).  
         [0043]     When talking is started (step S 3   a ), the CPU  24  checks the opening and closing state of the casing of the portable telephone  103  by using the opening and closing detecting unit  31 . If as a result the casing is in the opened state, i.e., the casing is in the state shown in  FIG. 6A  (no at step S 33 ), the CPU  24  notifies the acoustic processing unit  50  to that effect. The acoustic processing unit  50  sets the MICs  15   a  and  15   b , which become unnecessary for talking in the state shown in  FIG. 6A , and the SPK  11  to the OFF mode. In addition, the acoustic processing unit  50  sets the MIC  15   c  serving as transmitting means at the time of talking in the illustrated state to the MIC operation mode (step S 34 ).  
         [0044]     If at the time of talking the casing is in the folded state, i.e., the casing is in the state shown in  FIG. 6B  (yes at step S 33 ), the acoustic processing unit  50  makes the MICs  15   a  and  15   b  disposed on the surface of the casing upper part  103   a  operate in the MIC operation mode as transmitting means and makes the SPK  11  operate in a receiver operation mode as receiving means in order to make talking possible in the illustrated state. And the acoustic processing unit  50  sets the MIC  15   c , which cannot be used in the illustrated state, to the OFF mode (step S 35 ).  
         [0045]     If the portable telephone  103  is in the folded state as shown in  FIG. 6B  (yes at step S 36 ) when the video phone is started (step S 3   b ), the MICs  15   a  and  15   b  are made to operate in the MIC operation mode and the SPK  11  is made to operate in the monaural (left+right) speaker operation mode, whereas the MIC  15   c  is set to the OFF mode. If the casing of the portable telephone  103  is in the open state when it is used as video phone (no at the step S 36 ), the MICs  15   a  and  15   b  are set to the OFF mode and the MIC  15   c  is made to operate in the MIC operation mode whereas the SPK  11  is made to operate in the monaural (left+right) speaker operation mode.  
         [0046]     According to the portable telephone  103 , therefore, it is possible to provide an acoustic input-output function suitable for ordinary talking or talking using the video phone according to the opening and closing state of the casing.  
         [0047]     At the time of each of moving image recording (step S 3   c ), moving image reproduction (step S 3   d ) and voice and music reproduction (step S 3   e ), the MIC  15   c  is set to the OFF mode and setting similar to the steps S 6  and S 7  in the first embodiment shown in  FIG. 3  is conducted (steps S 39  and S 40 ).  
       Fourth Embodiment  
       [0048]      FIG. 8  is a block diagram showing a configuration of a portable telephone  104  in a fourth embodiment. The acoustic input-output unit  10  in the portable telephone  104  includes the SPK  11 , REC  13   a  and REC  13   b  as the acoustic output means. The acoustic input-output unit  10  further includes a signal source switch  18   a  and a signal source switch  18   b  for switching and setting the above-described receiver operation mode or speaker operation mode in the RECs  13   a  and  13   b.    
         [0049]     For example, when the REC  13   a  operates in the receiver operation mode, the signal source switch  18   a  connects the REC  13   a  to the REC drive unit  14 . When the REC  13   a  is set to the speaker operation mode in predetermined communication processing described later, the signal source switch  18   a  connects the REC  13   a  to the SPK drive unit  12 .  
         [0050]      FIG. 9  schematically shows an exterior view of the portable telephone  104 . The portable telephone  104  is a portable telephone of rotary type having a casing upper part  104   a  and a casing lower part  104   b  coupled by a pivot mechanism  104   c . As shown in  FIG. 9 , the REC  13   a  and REC  13   b  are disposed near an LCD  27  on the casing upper part  104   a , and an MIC  15  is disposed near the keys  25  on the casing lower part  104   b . The SPK  11  is disposed on a tip face of the casing lower part  104   b.    
         [0051]     An operation procedure of the portable telephone  104  will now be described with reference to a flow chart shown in  FIG. 10 . As the initialization processing at the time of start (step s 41 ), the portable telephone  104  sets the REC  13   a  and REC  13   b  to the receiver operation mode, and sets the SPK  11  to the monaural (left+right) speaker operation mode (step S 42 ).  
         [0052]     At the time of ordinary talking on the portable telephone  104  (step S 3   a ), the user uses it while keeping it in contact with an ear, and consequently one of the REC  13   a  and REC  13   b  is made to operate in the receiver operation mode and the other of the receivers and the SPK  11  are turned off (step S 43 ). In the illustrated example, the REC  13   a  is made to operate and the REC  13   b  is turned off.  
         [0053]     At the time of talking using video phone (step S 3   b ), the REC  13   a  is made to operate in the stereo (left) speaker operation mode and the REC  13   b  is made to operate in the stereo (right) speaker operation mode, whereas the SPK  11  is made to operate in the monaural (left+right) speaker operation mode (step S 44 ). As a result, it is possible to provide voice with the feeling of presence by using three acoustic output means at the time of video phone operation.  
         [0054]     At the time of moving image recording (step S 3   c ), the acoustic external output becomes unnecessary, and consequently all of the REC  13   a , REC  13   b  and SPK  11  serving as the acoustic output means are set to the OFF mode (step S 45 ). At the time of moving image reproduction (step S 3   d ) and at the time of voice and music reproduction (step S 3   e ), stereo acoustic outputting using the REC  13   a  and  13   b  and monaural outputting using the SPK  11  are conducted in the same way as the step S 44  at the time of video phone (step S 46 ).  
         [0055]     In the description of the fourth embodiment, the terminal of the rotary type as shown in  FIG. 9  is used as the portable telephone  104 . However, the above-described procedure can be applied to a terminal of folded type if it has the configuration shown in  FIG. 8 .  
       Fifth Embodiment  
       [0056]     In the present invention, the acoustic output of the terminal of the rotary type such as the portable telephone  104  at the time of talking and at the time of video phone use can be controlled according to the opening and closing state of the casing. Hereafter, its technique will be described as a fifth embodiment.  
         [0057]      FIG. 11  schematically shows an exterior view of a portable telephone  105  in the fifth embodiment. In the portable telephone  105  which is a terminal of rotary type, a REC  13   a  is disposed near a tip of the casing upper part  105   a  as shown in  FIG. 11A . A REC  13   b  is disposed near a pivot mechanism  105   c  and across an LCD  27  from the REC  13   a . By the way, the SPK  11  serving as another acoustic output means is disposed in the same way as the portable telephone  104  shown in  FIG. 9 .  
         [0058]     A state in which the portable telephone  105  is closed, i.e., the casing upper part  105   a  is rotated by the pivot mechanism  105   c  and laid on top of the casing lower part  105   b  is shown in  FIG. 11B . As appreciated from  FIG. 11B , the portable telephone  105  is formed so as to expose a MIC  15  on the casing lower part  105   b  even when the casing is closed. In both the state in which the portable telephone  105  is open as shown in  FIG. 11A  and the state in which the portable telephone  105  is closed as shown in  FIG. 11B , therefore, the MIC  15  can be used as the acoustic input means.  
         [0059]     The portable telephone  105  detects the opening and closing state of the casing by using the opening and closing detecting unit  31  shown in  FIG. 8 . As the opening and closing detecting unit  31 , for example, the pressure sensor described with reference to the third embodiment is used, and it is disposed near the tip on the surface of the casing upper part  105   a , i.e., near the tip on a face facing the face of the LCD  27  in opposite directions. As a result, the state of the  FIG. 11B  can be detected as the closed state of the casing.  
         [0060]     An operation procedure of the portable telephone  105  will now be described with reference to a flow chart shown in  FIG. 12 . By the way, a procedure at the time of moving image recording (step S 3   c ), at the time of moving image reproduction (step S 3   d ), and at the time of voice and music reproduction (step S 3   e ) is the same as that in the fourth embodiment described with reference to  FIG. 10 , and its description will be omitted.  
         [0061]     In initialization processing at the time of start (step S 51 ), the portable telephone  105  turns off the REC  13   a  and REC  13   b  and sets the SPK  11  to the monaural (left+right) speaker operation mode (step S 52 ).  
         [0062]     At the time of ordinary talking (step S 3   a ), the CPU  24  checks the opening and closing state of the casing by using the opening and closing detecting unit  31 , and notifies the acoustic processing unit of its result. Specifically, if the casing is in the rotated and housed state as shown in  FIG. 11B , i.e., in the closed state (yes at step S 53 ), the REC  13   b  disposed near the pivot mechanism  105   c  is made to operate in the receiver operation mode in order to use it as transmitting means, and the REC  13   a  and SPK  11  are turned off (step S 54 ).  
         [0063]     If the casing is in the opened state as shown in  FIG. 11A  (no at step S 53 ), the REC  13   a  is made to operate in the receiver operation mode in order to use it as transmitting means, and the REC  13   b  and SPK  11  are turned off (step S 55 ).  
         [0064]     At the time of talking using video phone (step S 3   b ), the REC  13   a , REC  13   b  and SPK  11  are made to operate respectively in the stereo (left) speaker operation mode, the stereo (right) speaker operation mode and the monaural (left+right) speaker operation mode, in the state in which the casing is open (yes at step S 56 ) or in the state in which the casing is closed (no at the step S 56 ). By the way, the (left) and (right) of the stereo outputs of the REC  13   a  and REC  13   b  may be interchanged according to the opening and closing state of the casing.