Voice communication system and voice communication method

What is claimed is:

1. A voice communication system including a line switching network to which telephones are connected, a packet switching network to which communication terminals are connected and which has a communication address scheme different from a telephone number scheme of said line switching network, and a communication server connected to said line switching network and said packet switching network and assigned a communication terminal address on said packet switching network, wherein:

each of said communication terminals comprises:

means for transmitting a voice communication request when an apparatus with which a communication is desired is a telephone connected to said line switching network, and performing communication control between said communication server and said communication terminal to establish a connection between said communication terminal and said communication server, and said voice communication request including the telephone number of the telephone, and

said communication server comprises:

means for receiving the voice communication request transmitted from said communication terminal to the communication terminal address of said communication server, and performing communication control between said communication server and said communication terminal which has transmitted said voice communication request to establish a connection between said communication server and said communication terminal;

means for performing communication control between said communication server and a telephone having a telephone number included in the received voice communication request to set said communication server and said telephone in a communication available state; and

means for receiving voice information transmitted from the telephone having said telephone number, editing said voice information into packets, and transmitting the packets to said communication terminal, while receiving packets transmitted from said communication terminal, and transmitting the voice information in the packets to the telephone having said telephone number.

2. A voice communication system according to claim 1, wherein said communication terminal further includes:

voice inputting means for inputting voice information;

voice encoding means for encoding the inputted voice information;

voice decoding means for decoding the encoded voice information in received packets; and

voice outputting means for outputting the decoded voice information.

3. A voice communication system according to claim 1, wherein said communication server further includes:

voice encoding means for encoding voice information from said telephone received through said line switching network;

means for editing said encoded voice information into packets and transmitting the packets to said communication terminal through said packet switching network;

voice decoding means for decoding the voice information in the packets from said communication terminal received through said packet switching network; and

means for transmitting said decoded voice information to said telephone through said line switching network.

4. A voice communication system according to claim 1, wherein said communication terminal further comprises:

means for allowing a user to select transmission of a mail to another communication terminal on said packet switching network with which a communication is desired, when a voice communication negating response is returned from the communication terminal as a result of transmitting a voice communication request to the communication terminal, and transmitting the mail to said communication terminal without inputting a communication address of said communication terminal when the user selects the transmission of the mail.

5. A voice communication system including a line switching network to which telephones are connected, a packet switching network to which communication terminals are connected and which has a communication address scheme different from a telephone number scheme of said line switching network, and a communication server connected to said line switching network and said packet switching network and assigned a communication terminal address on said packet switching network and a telephone number on said line switching network, wherein:

said communication terminals connected to said packet switching network are assigned unique extension numbers, respectively,

each of said telephones comprises:

means for controlling a communication between said telephone and said communication server, when a user inputs the telephone number of said communication server, to set said telephone and said communication server in a communication available state and transmitting an extension number inputted by the user to said communication server, and

said communication server comprises:

means for finding a communication terminal address of a communication terminal to which said extension number is assigned, based on the extension number transmitted from said telephone, to determine the communication terminal to be connected;

means for transmitting a voice communication request to the determined communication terminal to establish a connection between said communication server and said communication terminal; and

means for receiving voice information transmitted from the telephone having said telephone number, editing the voice information into packets, and transmitting the packets to said communication terminal, while receiving packets transmitted from said communication terminal, and transmitting voice information in the packets to said telephone having the telephone number.

6. A voice communication system according to claim 5, wherein said communication terminal further includes:

voice inputting means for inputting voice information;

voice encoding means for encoding the inputted voice information;

voice decoding means for decoding the encoded voice information in received packets; and

voice outputting means for outputting the decoded voice information.

7. A voice communication system according to claim 5, wherein said communication server further includes:

voice encoding means for encoding voice information from said telephone received through said line switching network;

means for editing said encoded voice information into packets and transmitting the packets to said communication terminal through said packet switching network;

voice decoding means for decoding the voice information in the packets from said communication terminal received through said packet switching network; and

means for transmitting said decoded voice information to said telephone through said line switching network.

8. A voice communication system according to claim 5, wherein said communication terminal further comprises:

means for allowing a user to select transmission of a mail to another communication terminal on said packet switching network with which a communication is desired, when a voice communication negating response is returned from the communication terminal as a result of transmitting a voice communication request to the communication terminal, and transmitting a mail to said communication terminal without inputting a communication address of said communication terminal when the user selects the transmission of a mail.

9. A voice communication system according to claim 5, wherein said communication server further comprises:

means for transmitting the mail to said communication terminal when a voice communication negating response is returned from said communication terminal as a result of transmitting said voice communication request to said communication terminal.

10. A voice communication system including a line switching network to which telephones are connected, a packet switching network to which communication terminals are connected and which has a communication address scheme different from a telephone number scheme of said line switching network, and a communication server connected to said line switching network and said packet switching network and assigned a communication terminal address on said packet switching network, wherein:

said communication terminals connected to said packet switching network are assigned unique telephone numbers, respectively,

each of said telephones comprises:

means for controlling a communication between said telephone and said communication server when a user inputs a telephone number assigned to one of said communication terminals, and

said communication server comprises:

means for finding, based on the telephone number inputted from said telephone, a communication terminal address of a communication terminal to which the telephone number is assigned to determine the communication terminal to be connected;

means for transmitting a voice communication request to the determined communication terminal to establish a connection between said communication server and said communication terminal; and

means for receiving voice information transmitted from said telephone, editing the voice information into packets, and transmitting the packets to said communication terminal, while receiving packets transmitted from said communication terminal, and transmitting voice information in the packets to said telephone.

11. A voice communication system according to claim 10, wherein said communication terminal further includes:

voice inputting means for inputting voice information;

voice encoding means for encoding the inputted voice information;

voice decoding means for decoding the encoded voice information in received packets; and

voice outputting means for outputting the decoded voice information.

12. A voice communication system according to claim 10, wherein said communication server further includes:

voice encoding means for encoding voice information from said telephone received through said line switching network;

means for editing said encoded voice information into packets and transmitting the packets to said communication terminal through said packet switching network;

voice decoding means for decoding the voice information in the packets from said communication terminal received through said packet switching network; and

means for transmitting said decoded voice information to said telephone through said line switching network.

13. A voice communication system according to claim 10, wherein said communication terminal further comprises:

means for allowing a user to select transmission of a mail to another communication terminal on said packet switching network with which a communication is desired, when a voice communication negating response is returned from the communication terminal as a result of transmitting a voice communication request to the communication terminal, and transmitting the mail to said communication terminal without inputting a communication address of said communication terminal when the user selects the transmission of the mail.

14. A voice communication system according to claim 10, wherein said communication server further comprises:

means for transmitting a mail to said communication terminal when a voice communication negating response is returned from said communication terminal as a result of transmitting said voice communication request to said communication terminal.

15. A voice communication system according to claim 11, wherein said communication server further includes:

voice encoding means for encoding voice information from said telephone received through said line switching network;

means for editing said encoded voice information into packets and transmitting the packets to said communication terminal through said packet switching network;

voice decoding means for decoding the voice information in the packets from said communication terminal received through said packet switching network; and

means for transmitting said decoded voice information to said telephone through said line switching network.

16. A voice communication system according to claim 5, wherein said communication server comprises a table for holding extension numbers of said communication terminals and communication terminal addresses corresponding to the extension numbers.

17. A voice communication system according to claim 10, wherein said communication server comprises a table for holding telephone numbers of said communication terminals and communication terminal addresses corresponding to the telephone numbers.

18. A voice communication system according to claim 5, wherein:

said line switching network is ISDN, and

each of said telephones transmits a voice communication request including an extension number for specifying said communication terminal as a parameter to said communication server, and said communication server finds a communication terminal address of a communication terminal to be connected from the extension number included in the voice communication request.

19. A voice communication system including a line switching network to which telephones are connected, a packet switching network to which communication terminals are connected and which has a communication address scheme different from a telephone number scheme of said line switching network, and a communication server connected to said line switching network and said packet switching network and assigned a communication terminal address on said packet switching network and a telephone number on said line switching network, wherein:

one of the communication terminals connected to said packet switching network is used as a switcher terminal,

each of said telephones comprises:

means for controlling a communication between said telephone and said communication server, when a user inputs the telephone number of said communication server, to set said telephone and said communication server in a communication available state,

said switcher terminal comprises:

means for connecting said switcher terminal with said communication server in response to a voice communication request from said communication server to set said switcher terminal and said telephone in a communication available state, wherein a switcher can speak with the user of said telephone;

means for finding a communication terminal address in response to an input of information for specifying a person to which the user desires to call, said information being obtained by a conversation between the switcher and the user; and

means for transmitting a connected terminal determination result including the found communication terminal address to said communication server, and

said communication server comprises:

means for transmitting the voice communication request to said switcher terminal, when said switcher terminal and said telephone are set in the communication available state, to establish a connection between said communication server and said switcher terminal;

means for receiving the connected terminal determination result from said switcher terminal, and transmitting the voice communication request to a communication terminal having the communication terminal address included in the connected terminal determination result to establish a connection between said communication server and said communication terminal; and

means for receiving voice information transmitted from said telephone, editing the voice information into packets, and transmitting the packets to said communication terminal, while receiving packets transmitted from said communication terminal, and transmitting the voice information in the packets to said telephone.

20. A voice communication method in a voice communication system including a line switching network to which telephones are connected, a packet switching network to which communication terminals are connected and which has a communication address scheme different from a telephone number scheme of said line switching network, and a communication server connected to said line switching network and said packet switching network and assigned a communication terminal address on said packet switching network, said method comprising the steps of:

transmitting a voice communication request including a telephone number of one of said telephones from one of said communication terminals to said communication server through said packet switching network;

transmitting a call setting request from said communication server which has received said voice communication request to a telephone having the telephone number included in said voice communication request through said line switching network;

returning a call setting accepting response from said one telephone which has received said call setting request to said communication server through said line switching network;

returning a voice communication accepting response from said communication server which has received said call setting accepting response to said communication terminal through said packet switching network; and

in said communication server, receiving voice information transmitted from said one telephone through said line switching network, editing said voice information into packets, and transmitting the packets to said communication terminal through said packet switching network, while receiving packets transmitted from said communication terminal through said packet switching network, and transmitting said voice information in the packets to said one telephone through said line switching network to carry out a communication between said telephone and said communication terminal through said communication server.

21. A voice communication method in a voice communication system including a line switching network to which telephones are connected, a packet switching network to which communication terminals are connected and which has a communication address scheme different from a telephone number scheme of said line switching network, and a communication server connected to said line switching network and said packet switching network and assigned a communication terminal address on said packet switching network and a telephone number on said line switching network, said method comprising the steps of:

transmitting a call setting request from one of said telephones to said communication server through said line switching network;

returning a call setting accepting response from said communication server which has received said call setting request to said one telephone through said line switching network;

determining a communication terminal address of a communication terminal to be connected to said one telephone by said communication server;

transmitting a voice communication request from said communication server to a communication terminal having said determined communication terminal address through said packet switching network;

returning a voice communication accepting response from said communication terminal which has received said voice communication request to said communication server through said packet switching network; and

in said communication server, receiving voice information transmitted from said one telephone through said line switching network, editing said voice information into packets, and transmitting the packets to said communication terminal through said packet switching network, while receiving the packets transmitted from said communication terminal through said packet switching network, and transmitting said voice information in the packets to said one telephone through said line switching network to carry out a communication between said telephone and said communication terminal through said communication server.

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

The present invention relates to a voice communication system and method in communication terminals connected through a communication network.

As a conventional voice communication system, there is known a system which uses a line switching procedure through a line switching network such as a telephone network. For example, the standard thereof is indicated in CCITT (International Telegraph and Telephone Consullative Committee) Recommendation, ISDN, Q. 937. In this system, a communication terminal (telephone) connected to the line switching network transmits a voice communication request to a switching center dedicated to line switching processing, and the switching center receiving the request performs voice communication control for communication with a communication terminal (telephone) of the other party. Voice information sent at a constant speed is continuously transmitted and received through the switching center even during the voice communication.

In a packet switching network such as LAN (Local Area Network), in turn, the communication control is directly performed between communication terminals for transmitting and receiving packets. For example, Etherphone using Ethernet is well known.

However, due to the difference in schemes between the packet switching network and the line switching network, conventional voice communication systems such as that using the telephone network and so on cannot be utilized for realizing voice communication between communication terminals connected to the packet switching network.

To cope with this problem, a system for editing voice information into packets for transmission and reception between communication terminals has been proposed for adapting the voice communication scheme for communications between communication terminals connected to the packet switching network to the line switching network. However, even if the line switching network is connected with the packet switching network, a direct voice communication is not permitted between a communication terminal supporting voice communications between communication terminals connected to the packet switching network and a telephone connected to the line switching network and supporting the conventional voice communication functions. This is due to the difference between the voice communication protocol of the packet switching network and the conventional voice communication protocol.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a voice communication system and a voice communication method which enable voice communication to be performed between a communication terminal connected to the packet switching network and a communication terminal connected to the line switching network.

It is another object of the present invention to provide a voice communication system and a voice communication method which enable voice communication, even initiated by a communication terminal connected to the packet switching network to a telephone connected to the line switching network and supporting the conventional voice communication functions, to proceed in the same manner as a voice communication between communication terminals connected to the packet switching network.

It is a further object of the present invention to provide a voice communication system and a voice communication method which can transmit a message in the form of an electronic mail instead of the voice communication in case a voice communication to a communication terminal connected to the packet switching network is prevented for some reason, without requiring a user to start another program or input a communication address.

It is a further object of the present invention to provide a voice communication system and a voice communication method which allows a telephone connected to the line switching network and supporting conventional voice communication functions to request a voice communication to a communication terminal connected to the packet switching network.

To achieve the above objects, according to one feature of the present invention, when a voice communication request is issued from a communication terminal connected to a packet switching network, if the address of the other party to which a user desires to have a voice communication, inputted by the user, is a communication terminal address (telephone number) of a telephone connected to a line switching network, communication control is performed between the communication terminal and a communication server to establish a connection between the communication terminal and the communication server. The communication server performs the communication control for a telephone connected to the line switching network to set a communication available state between the communication server and the telephone. This control enables a communication between the communication terminal and the telephone through the communication server. Thereafter, the communication server receives voice information transmitted from the telephone, edits the voice information into packets, and transmits the packets to the communication terminal. The communication server also receives packets transmitted from the communication terminal, and transmits voice information in the packets to the telephone. In this way, communication is carried out.

When a voice communication request is issued from a communication terminal connected to the packet switching network, if the address of the other party to which a user desires to have a voice communication, inputted by the user, is the address of another communication terminal connected to the packet switching network, the communication control is performed for a communication terminal having the communication terminal address, conventionally, to carry out the communication.

When a communication request is issued from a telephone connected to the line switching network to a communication terminal connected to the packet switching network, each of communication terminals connected to the packet switching network has previously been assigned a unique extension number, such that when the telephone number of the communication server is inputted from a telephone, the communication control is performed between the telephone and the communication server to create a communication available state between the telephone and the communication server, and an inputted extension number is transmitted from the telephone to the communication server. The communication server finds a communication terminal address from the extension number transmitted from the telephone, determines a communication terminal to be connected, and transmits a voice communication request to the communication terminal to establish a connection with the telephone. This enables communication between the telephone and the communication terminal through the communication server. Thereafter, the communication server receives voice information transmitted from the telephone, edits the voice information into packets, and transmits the packets to the communication terminal. The communication server also receives packets transmitted from the communication terminal, and transmits voice information in the packet to the telephone, thus carrying out the communication.

The communication server may comprise a table for finding a communication terminal address from an extension number. If a push-type telephone having ten-key and function buttons is used, the extension number may be inputted through the push buttons. For inputting an extension number, an oral guidance may be outputted from the communication server to the telephone, such that the user responsively inputs an extension number corresponding to a communication terminal with which the user desires to communicate.

When the line switching network is ISDN (Integrated Services Digital Network), a telephone may transmit a voice communication request including as a parameter an extension number for specifying a communication terminal to the communication server, such that the communication server finds the communication terminal address of a communication terminal to be connected from the extension number included in the voice communication request.

Instead of assigning an extension number, a unique telephone number may be assigned to each of communication terminals connected to the packet switching network. In this case, although these telephone numbers are actually assigned to the communication server, they are regarded as telephone numbers of communication terminals from the user. Then, when a telephone number of a communication terminal is inputted from a telephone, the communication control is performed between the telephone and the communication server, wherein the communication server finds a communication terminal address from the telephone number inputted from the telephone, determines a communication terminal to be connected, and transmits a voice communication request to the communication terminal. This control enables a communication between the telephone and the communication terminal through the communication server. Thereafter, the communication server receives voice information transmitted from the telephone, edits the voice information into packets, and transmits the packets to the communication terminal. The communication server also receives packets transmitted from the communication terminal, and transmits voice information in the packets to the telephone. In this way, communication is carried out.

Additionally, the communication server may include a table for finding a communication terminal address from a telephone number. Since a telephone number of each communication terminal is actually the telephone number of the communication server on the line switching network, the communication server is called when one of these telephone numbers is inputted from a telephone on the line switching network.

According to one aspect of the present invention, a communication terminal connected to the packet switching network may be one that encodes voice inputted through a voice input means, transmits the encoded voice information, and outputs received encoded voice information after decoding the same. In this case, the communication server decodes encoded voice information in the form of packets received from a communication terminal connected to the packet switching network, outputs the decoded voice information to the line switching network, encodes voice information received from the line switching network at a constant speed, edits the encoded voice information into packets, and transmits the packets to the communication terminal.

For issuing a communication request from a communication terminal connected to the packet switching network to another communication terminal, a voice communication request is first issued from the communication terminal. In this event, a voice communication negating response may be transmitted from the communication terminal of the other party. This could be because nobody responds although the communication terminal of the other party is called. In this case, it is convenient if a mail can be transmitted to the communication terminal of the other party without requiring the inputting of the address of the other party. The mail may be unconditionally transmitted, or a guidance may be provided to the user of the communication terminal so as to allow the user to determine whether or not a mail is transmitted. The contents of the mail may be a fixed voice mail created by the system or an arbitrary mail inputted by the user.

For issuing a communication request from a telephone connected to the line switching network to a communication terminal connected to the packet switching network, a voice communication request is first issued from the telephone to the communication server. In this event, a guidance of a voice communication negating response may be returned from the communication server. This could be because nobody responded although the communication server called the communication terminal of the other party. In this case, it is convenient that a mail can be transmitted to the communication terminal of the other party without requiring the user to input the address of the other party. The mail may be unconditionally transmitted, or a guidance may be provided to the user of the telephone so as to allow the user to determine whether a mail should be transmitted. The mail may include a fixed contents created by the system or arbitrary contents inputted by the user.

Further, a communication terminal on the packet switching network may be used as a switcher terminal for managing the relationships between communication terminals connected to the packet switching network and communication terminal users. In this case, when the telephone number of the communication server is inputted from a telephone connected to the line switching network and supporting conventional voice communication functions, the communication server first creates a communication available state between the switcher terminal and the telephone. The user speaks with a switcher at the switcher terminal to specify a person with whom the user desires to communicate. Since the switcher terminal manages the relationships between respective communication terminals and users of these communication terminals, a corresponding communication terminal can be found from information which specifies the person with whom the user of the telephone desires to communicate. The address of the communication terminal is transmitted from the switcher terminal to the communication server. The communication server performs the communication control between the telephone and a communication terminal having the communication terminal address transmitted from the switcher terminal to establish a connection with the communication terminal. This control enables a communication between the communication terminal and the telephone through the communication server. Thereafter, the communication server receives voice information transmitted from the telephone, edits the voice information into packets, transmits the packets to the communication terminal. The communication server also receives packets transmitted from the communication terminal, and transmits voice information in the packets to the telephone.

It should be noted that the transmission and reception of control commands such as a voice communication start command, voice communication end command, and so on and the transmission and reception of voice packets between communication terminals on the packet switching network and between a communication terminal and the communication server, may be carried out through separate communication functions having different characteristics such as reliability, communication delay, and so on.

According to the voice communication system and voice communication method of the present invention, the other party to which the user requests a voice communication is determined to be a communication terminal connected to the packet switching network or a telephone connected to the line switching network in accordance with the address of the other party inputted by the user of a communication terminal connected to the packet switching network. If the user issues the request to a telephone connected to the line switching network, the communication server absorbs the difference between a voice communication protocol of the packet switching network and a conventional voice communication protocol of the line switching network. Stated another way, the communication server realizes the compatibility between different kinds of protocols. For this reason, even a voice communication initiated by a communication terminal connected to the packet switching network to a telephone connected to the line switching network and supporting the conventional voice communication function can be carried out in the same manner as a voice communication between communication terminals connected to the packet switching network.

Also, since an extension number or a telephone number of a communication terminal connected to the packet switching network is inputted from a telephone connected to the line switching network such that the communication server finds a communication terminal address corresponding to the extension number or the telephone number and connects the telephone to the communication terminal, a voice communication may be requested to a communication terminal connected to the packet switching network from a telephone connected to the line switching network and supporting the conventional voice communication functions.

In case a voice communication to a communication terminal was prevented for some reason, a mail may be used instead of the voice communication to send a message without requiring the user to start another program or input a communication address.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the whole configuration of a voice communication system according to an embodiment of the present invention;

FIG. 2 is a block diagram showing the configuration of a communication terminal in FIG. 1;

FIG. 3 is a block diagram showing the allocation of programs in a memory of the communication terminal;

FIG. 4 is a flow chart showing the processing of a voice communication program on the communication terminal for starting a voice communication, upon receiving a voice communication request from another communication terminal;

FIG. 5 is a flow chart showing the processing of the voice communication program on the communication terminal for starting a voice communication by a request of the user;

FIG. 6 is a block diagram showing the configuration of a communication server;

FIG. 7 is a block diagram showing the allocation of programs in a memory of the communication server;

FIG. 8 is a flow chart showing the processing of a voice communication program on the communication server for starting a voice communication between a communication network on LAN and the telephone, upon receiving a call setting request from a telephone connected to a public network;

FIG. 9 is a flow chart showing the processing of the voice communication program on the communication server for starting voice communication between the communication terminal on LAN and a telephone, upon receiving a voice communication request from a communication terminal on LAN;

FIG. 10 is a flow chart showing the processing performed during a communication;

FIG. 11 is a sequence diagram showing a procedure followed by a communication terminal connected to the LAN for making a call to a telephone through the communication server by a request from a communication terminal on the LAN;

FIG. 12 is a sequence diagram showing a procedure followed by a communication terminal connected to LAN for making a call to a telephone connected to the public network through the communication server by a request from the telephone;

FIG. 13 shows the structure of a voice communication request command;

FIG. 14 shows the structure of a voice communication response command;

FIG. 15 shows the structure of a voice communication command;

FIG. 16 shows the structure of a voice communication end notice command;

FIG. 17 is a flow chart showing the processing for determining a communication terminal with which a telephone user desires to communicate when using push buttons;

FIG. 18 shows the structure of an extension number management table;

FIG. 19 is a flow chart showing the processing for determining a communication terminal with which a telephone user desires to communicate when a communication terminal on the LAN is utilized as a switcher terminal;

FIG. 20 is a flow chart showing the processing performed by the switcher terminal;

FIG. 21 shows the structure of a connected terminal determination notice command;

FIG. 22 shows the structure of a communication terminal address management table; and

FIG. 23 is a flow chart showing the processing for determining a communication terminal with which a telephone user desires to communicate when the public network is ISDN.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will hereinafter be described with reference to the accompanying drawings.

FIG. 1 shows the whole configuration of a voice communication system according to an embodiment of the present invention, including communication terminals 10-1, 10-2 for performing communications; LAN (Local Area Network) 1 to which the communication terminals 10-1, 10-2 are connected; a telephone 2; a public network 3; and a communication server 20 which is connected simultaneously to the public network 3 and the LAN 1.

It will be of course understood that while one telephone 2 and two communication terminals 10-1, 10-2 (hereinafter, an arbitrary communication terminal will be denoted by reference numeral 10) only are shown in FIG. 1, more telephones and communication terminals may be connected.

FIG. 2 shows in a block diagram form the configuration of the communication terminal 10 in FIG. 1. The communication terminal 10 comprises a voice input unit 11; a voice encoder 12; a memory 13; a LAN communication controller 14; a voice decoder 15; a voice output unit 16; a processor 17; and a storage unit 18. The LAN communication controller 14 is connected to the LAN 1. The voice encoder 12, voice decoder 15, LAN communication controller 14, memory 13, storage unit 18, and processor 17 are mutually connected through an internal bus 19.

The voice input unit 11 is provided for inputting voice information. Inputted voice information is encoded by the voice encoder 12. Coded voice information outputted from the voice encoder 12 is read