Abstract:
A telephone apparatus having a howling preventing function is connected to a communication partner via a telephone exchange and is constructed by a communication unit, including a microphone and a speaker, for communicating with the communication partner, and a preventing unit for preventing howling by the communication unit based on a mode of the communication unit and a signal according to the communication partner received from the telephone exchange.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a telephone apparatus with a howling preventing function. 
     2. Related Background Art 
     In case of performing a hand-free talking, when a 2-line/4-line converting circuit exists between a calling side and a communication partner, howling occurs due to a reflection of a talking signal in the 2-line/4-line converting circuit. 
     There is a drawback such that an apparatus is expensive when an echo canceller is used to prevent the howling. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to improve a method of preventing a howling. 
     It is another object of the invention to simplify a construction or control to prevent a howling. 
     Further another object of the invention is to provide a telephone apparatus which is connected to a communication partner via a telephone exchange and which doesn&#39;t turn on a microphone when it is judged that a howling will occur if a speaker and the microphone are turned on. 
     The above and other objects and features of the present invention will become apparent from the following detailed description and the appended claims with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a system diagram of a button telephone apparatus of an embodiment; 
     FIG. 2 is a flowchart showing the operation of a main device of the button telephone apparatus of the embodiment; 
     FIG. 3 is a flowchart showing the operation of an exclusive telephone of the button telephone apparatus of the embodiment; 
     FIG. 4 is a flowchart showing a continuation of the operation of the exclusive telephone of the button telephone apparatus of the embodiment; 
     FIG. 5 is a sequence diagram in the case where an area for storing a microphone standby state is “ON” and a parameter of a voice call command is “possible”; 
     FIG. 6 is a sequence diagram in the case where the area for storing the microphone standby state is “ON” and the parameter of the voice call command is “impossible”; and 
     FIG. 7 is a sequence diagram in the case where the area for storing the microphone standby state is “OFF”. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a system diagram of a button telephone apparatus. 
     Reference numeral  101  denotes a main device of the button telephone apparatus;  101 A a control unit of the main device  101 ;  100  outside lines;  102  a connection device of a wireless telephone;  103  a wireless-exclusive telephone;  104  a control unit for controlling all of the operations of the wireless-exclusive telephone  103 ;  105  an RAM;  106  an antenna;  107  a wireless interface unit;  108  a switch for switching (a speaker  114  and a microphone  115 ), and a handset  111 ;  109  a switch for switching ON/OFF of the speaker  114 ;  110  a switch for switching ON/OFF of the microphone  115 ;  111  the handset main body;  112  a receiver;  113  a transmitter;  114  the speaker;  115  the microphone;  116  a speaker button;  117  a speaker LED which is turned on or off by a depression of the speaker button or the like;  118  a microphone button;  119  a microphone LED which is turned on or off by a depression of the microphone button or the like;  120  a dialling button;  121  an area in the RAM for storing a standby state of the microphone  115 ;  122  an analog telephone; and  123  a digital telephone. 
     Kinds (analog, digital, exclusive wireless, and the like) of terminals connected to extensions of the main device  101  are stored in a memory  101 M in the control unit  101 A. The analog telephone  122  is connected to the main device  101  via a 2-line/4-line converting circuit. 
     FIG. 2 is a flowchart for explaining a portion regarding the operation of the main device  101  when there is a voice call (talk back) from an extension. 
     FIGS. 3 and 4 are flowcharts for explaining a portion regarding the operation of the wireless-exclusive telephone  103  of the invention. In FIGS. 2 to  4 , description of the other operations is omitted. 
     The operation of the main device  101  of the embodiment will be first described with reference to the flowchart of FIG.  2 . 
     When the voice calling or the voice call (talk back) is received from an arbitrary extension connected to the main device  101  (step S 101 ), the control unit  101 A of the main device  101  judges whether the extension on the calling side is an analog telephone which is connected via the 2-line/4-line converting circuit or not (S 102 ). If YES, a value of a parameter which is added to a voice call (talk back) command for transmitting to the wireless-exclusive telephone as a partner to be voice called is set to “impossible” (S 103 ). When the extension is not the analog telephone, the value of the parameter is set to “possible” (S 104 ) and the voice call command added with the parameter is transmitted to the called party, for example, the connection device  102  of the wireless-exclusive telephone  103  (S 105 ). 
     The operation of the wire-exclusive telephone  103  of the embodiment will now be described with reference to the flowcharts of FIGS. 3 and 4. 
     When the microphone button  118  is depressed (S 201 ), the control unit  104  checks the area  121  for storing the microphone standby state. When the area for storing the microphone standby state is “ON” (S 202 ), the area for storing the microphone standby state is set to “OFF” (S 203 ) and the microphone LED  119  is turned off (S 204 ). 
     When the area  121  for storing the microphone standby state is “OFF” (S 202 ), the area for storing the microphone standby state is set to “ON” (S 205 ) and the microphone LED  119  is turned on (S 206 ). 
     When the voice call command transmitted from the main device  101  in step S 105  in FIG. 2 is received through the connection device  102  (S 207 ), the control unit  104  turns on the speaker  114  in the wire-exclusive telephone (the switch  109  is changed to SW 2 A) (S 208 ) and checks the area  121  for storing the microphone standby state in the RAM  105 . 
     When the area  121  for storing the microphone standby state is “OFF” (S 209 ), the microphone  115  is held in the “OFF” state irrespective of the parameter value of the voice call command (refer to FIG.  7 ). 
     When the area  121  for storing the microphone standby state is “ON” (S 209 ), the parameter of the voice call command received from the main device  101  is checked. When the value of the parameter is set to “possible” (S 210 ), the microphone  115  of the wireless-exclusive telephone is turned “ON” (the switch  110  is changed to SW 3 A) (S 212 ), thereby performing a hand-free talking (S 213 ) (refer to FIG.  5 ). 
     When the area  121  for storing the microphone standby state is “ON” and the value of the parameter is set to “impossible”, the microphone LED  119  is turned off (S 211 ) thereby notifying that a microphone talking cannot be performed to a person on the wireless-exclusive telephone  103  side (refer to FIG.  6 ). 
     In the case where the microphone button  118  is depressed when the microphone standby state is “OFF” in step S 209  and a speaker receiving state (the speaker  114  is “ON” and the microphone  115  is “OFF”) is set, the control unit  104  turns on the microphone  115  and microphone LED  119  if the parameter of the voice call command is set to “possible” in a manner similar to steps S 210  to S 213  (S 218 ). When the parameter of the voice call command is set to “impossible”, the microphone  115  and microphone LED  119  is held in the “OFF” state. 
     When the handset  111  is off-hooked (S 214 ), the microphone  115  and speaker  114  are turned off and the microphone LED  119  is turned off in the case where it is “ON”, thereby changing the mode to a handset talking mode (the switch  109  for speaker is switched to SW 2 B, the switch  110  for microphone is switched to SW 3 B, and the switch  108  is switched to SW 1 A) (S 215 ). When the handset is on-hooked (S 216 ), the microphone LED  119  is turned on when the area  121  for storing the microphone standby state is “ON” (S 217 ). 
     Although the area for storing the microphone standby state is switched by the button in the embodiment, it can be also set by a software switch by a specific operation. In order to display ON/OFF of the area for storing the present standby state, an LCD can be also provided and characters or codes can be displayed on the LCD instead of turning on or off the microphone LED  119 . 
     Although the operation of the voice call has been described above in the embodiment, an operation similar to the above can be also performed when the speaker button  116  is depressed so as to respond to an ordinary call. 
     That is, when the wireless-exclusive telephone  103  is called by a transmission from an extension or a reception from an outside line in step S 110  in FIG. 2, the control unit  101 A of the main device  101  transmits a call command including the parameter which is set to “impossible” when the transmitting extension or reception outside line is an analog line and is set to “possible” in the other cases to the wireless-exclusive telephone  103  via the connection device  102 . 
     On the other hand, when the call command is received in step S 220 , the control unit  104  in the wireless-exclusive telephone  103  makes a ringing. When the speaker button  116  is depressed, the control unit  104  turns on the speaker  114  in a manner similar to steps S 208  to S 213 . When the microphone standby state is “ON” and the parameter included in the call command received from the main device  101  is set to “possible”, the control unit  104  turns on the microphone  115 , thereby performing the hand-free talking. In the case where the parameter included in the call command is set to “impossible”, the control unit  104  turns off the microphone LED  119  even when the microphone standby state is “ON”. When the microphone standby state is “OFF”, the microphone  115  and microphone LED  119  are held in the “OFF” state irrespective of the value of the parameter included in the call command. 
     When the speaker button  116  is depressed during the reception ringing, if the microphone standby state is “OFF” and the microphone button  118  is depressed during the speaker reception, the control unit  104  turns on the microphone  115  and microphone LED  119  so long as the parameter included in the call command is set to “possible” in a manner similar to step S 218 . When the parameter is set to “impossible”, the microphone  115  and microphone LED  119  are held in the “OFF” state. 
     When the speaker button  116  is depressed after a reception call was responded by using the handset  111 , an operation similar to the above can be also performed. 
     When the speaker button  116  is depressed during the handset talking after the reception call was responded by using the handset  111 , the control unit  104  changes the switch  108  from SW 1 A to SW 1 B in step S 220  and turns on the speaker  114  in a manner similar to steps S 208  to S 213 . When the microphone standby state is “ON” and the call command including the parameter of “possible” is received from the main device  101 , the control unit  104  turns on the microphone  115 , thereby performing the hand-free talking. When the call command including the parameter of “impossible” is received from the main device  101 , even if the microphone standby state is “ON”, the control unit  104  turns off the microphone LED  119 . When the microphone standby state is “OFF”, the microphone  115  is held in “OFF”. When the microphone button  118  is depressed in such an “OFF” state, if the parameter included in the call command is set to “possible”, the control unit  104  turns on the microphone  115  and turns off the microphone LED  119 . On the other hand, when the parameter included in the call command is set to “impossible”, the microphone  115  and microphone LED  119  are held in the “OFF” state. 
     Although the invention has been described above with respect to the wireless telephone, the invention can be also applied to a wire telephone for determining the ON/OFF of the microphone in accordance with the notification of “possible” or “impossible” of the hand-free talking from the main device and the operation of the microphone button. The invention is not limited to the construction of the foregoing embodiments but many modifications and variations are possible within the spirit and scope of the appended claims of the invention.