JP2942178B2 - Conference call system using wireless terminals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a conference call system using a wireless terminal device in a telephone exchange.

[0002]

2. Description of the Related Art Conventionally, when making a conference call using a normal wired connection communication terminal device, a caller (meeting convenor) is
The information of the communication terminal device used by the conference call participant and the conference start time are registered in the main device (telephone exchange device) in advance, and when the main device recognizes that the conference start time has come, The communication terminal device used by the caller and the communication terminal device used by the conference call participant are called, and when these respond, they are connected to the conference call device to set up a conference call.

On the other hand, there has been an increasing demand for a system for conducting a conference call using a wireless terminal device. In the case of such a conference call system using a wireless terminal device, when the position of the wireless terminal device is not registered, for example, immediately after the system starts operating, the above-described wired connection communication terminal The same connection control as the conference call connection using the device cannot be performed, and it is necessary to request the conference call connection under the initiative of the wireless terminal device.

When the wireless terminal device moves out of the area where radio signals can be transmitted and received, the call is disconnected.
When the wireless terminal device returns to the area where the radio signal can be transmitted / received, the wireless terminal device needs to request the conference call connection again.

[0005] As techniques related to this, JP-A-4-49796, JP-A-4-357148, JP-A-6-30137 and the like can be mentioned.

[0006]

In the above prior art, in a conference call system using a wireless terminal device,
When the location registration of the wireless terminal device is not performed, there is a problem that the main device cannot simultaneously call the wireless terminal devices used by the conference call participants.

Further, after the radio terminal device moves out of the area in which the radio signal can be transmitted and received and then returns to the area in which the radio signal can be transmitted and received, the radio terminal device establishes a call connection. Without the required operation, the conference call could not be started again.

Further, a conference call is a setting of only one group, and a function of integrating conference calls of a plurality of groups into one group and conversely, separating a conference call of one group into a plurality of groups is provided. No consideration was given, and there was a problem with usability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a first object of the present invention is to allow a caller (conference convener) to perform any operation when the main apparatus is operated (on-line). Another object of the present invention is to provide a conference call system using a wireless terminal device that automatically calls a plurality of wireless terminal devices and makes a call connection in a conference call state.

[0010] A second object of the present invention is to provide a wireless terminal device in which a caller does not perform any operation when the wireless terminal device moves from outside an area where radio signals can be transmitted and received. Is to provide a conference call system using a wireless terminal device that makes the terminal participate again in a conference call.

A third object of the present invention is to integrate a plurality of groups of conference calls into one group, and conversely, to provide a function of separating a group of conference calls into a plurality of groups. It is to provide a conference call system using a terminal device.

[0012]

SUMMARY OF THE INVENTION A first object of the present invention is to:
In a conference call system using a wireless terminal device including a plurality of wireless terminal devices and a switching device that accommodates a plurality of wireless base stations and a conference call device, the switching device,
A table that stores a connection state between the plurality of wireless terminal devices and the conference call device, a unit that recognizes a wireless terminal device that is not connected to the conference call device based on the table, and a state in which the conference call device is not connected. Means for continuously transmitting a call request of the wireless terminal device in the above, to all of the plurality of wireless base stations, and when a response signal is detected from any of the plurality of wireless base stations, the response signal is transmitted. Means for connecting a wireless terminal device to an empty port of the conference call device, and automatically making a call for setting up a conference call with the plurality of wireless terminal devices when the exchange device is in an operating state. You.

[0013] A second object of the present invention is to provide the plurality of radio base stations with means for sending a disconnection signal to the switching device when a radio terminal device moves out of the area of the plurality of radio base stations. The exchange device, further comprising, when detecting the disconnection signal, means for identifying a wireless terminal device that has transitioned to a disconnected state, and an area corresponding to the wireless terminal device that has transitioned to the disconnected state in the table. This is achieved by providing a conference call device and means for setting information indicating that the connection is not established.

Further, a third object of the present invention is that the switching device further comprises a wireless terminal device group for one conference group and a wireless terminal device group for each conference group for a plurality of conference groups. This is achieved by providing a conference call connection table to be registered and control means for separating and integrating conference groups by referring to the conference call connection table when recognizing a conference group switching request.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system configuration diagram showing a conference call system of the present invention. In FIG. 1, the conference call system includes an exchange device 1, a control terminal device 2, a wireless base station 3, and a wireless terminal device 4.

The switching device 1 includes a time switch 10
, Line interface device 11, digital wireless interface device 12, and line interface device 1
3, a dedicated line interface device 14, a conference communication device 15, a central control device 16, and a main storage device 17.

The time switch 10 includes a line interface device 11, a digital wireless interface device 12,
It contains a central office line interface device 13, a dedicated line interface device 14, and a conference communication device 15, and freely connects a call between them. The line interface device 11 is connected to the control terminal device 2 and controls the control terminal device 2. The digital wireless interface device 12 is connected to the wireless base station 3, controls the wireless base station 3 regarding a call, and interfaces the wireless base station 3 and the time switch 10.

Further, the line interface device 13 comprises:
The interface for connection to the public network is provided, and the dedicated line interface device 14 provides an interface for connection to another system. The conference call device 15 pulls in calls from a plurality of terminal devices,
A conference call connection is made between the plurality of terminal devices.

Further, the central control device 16 controls the exchange device 1
Is a control device that controls the whole of the
0, line interface device 11, digital wireless interface device 12, office line interface device 13,
Dedicated line interface device 14 and conference call device 1
5 are all operating under the control of the central controller 16. The main storage device 17 stores programs, station data, and tables necessary for the central control device 16 to perform control operations.

The radio base station 3 controls communication with the radio terminal 4 based on a predetermined operation sequence (for example, according to the second generation cordless telephone system standard "RCR STD-28"). Under the control of the central controller 16, a processing operation for establishing a wireless communication path is performed.

Although not shown, the switching device 1 is provided with a power switch for turning on and off the power of the switching device 1, and the switching device 1 is turned on (powered on) to operate (on-line).

FIG. 2 is an external view of the wireless terminal device. In FIG. 2, the wireless terminal device 4 includes a power switch 41,
Answer button 42, dial button 43, display device 4
4 is provided. The power switch 41 is a switch for turning on and off the power of the wireless terminal device 1, and the answer button 42 is a button for answering an incoming call. The dial button 43 is a button for inputting a telephone number, and the display device 44 displays various information related to communication.

FIG. 3 shows station data stored in the main storage device 17. In FIG. 3, (a) is a conference call connection table that stores the conference call belonging state of the wireless terminal device, and indicates which conference group each wireless terminal device belongs to. Conference call connection table 300
Has a conference group number 302 corresponding to the wireless terminal device number 301, and a conference group number 3
02 has an information area 303 with grouping and an information area 304 without grouping.

In FIG. 3A, when there is a grouping, the radio terminals PS1 to PS6 belong to the conference group 1, the radio terminals PS7 to PS12 belong to the conference group 2, and , Wireless terminal device PS
13 to PS16 indicate that they do not belong to the conference group. If no grouping is performed, the wireless terminal device P
S1 to PS12 belong to the conference group 1, and the wireless terminal devices PS13 to PS16 do not belong to the conference group.

FIG. 3B is a conference call device allocation table showing the allocation of the use ports of the conference call device when there is a conference group, and the use port allocation of the conference call device when there is no conference group. It is.
In the conference call device allocation table 350, the conference grouping area 351 is the conference group 1 area 35.
4 and a conference group 2 area 355, and further has a non-conference grouping area 352, and a use port number 353 of a conference call device that can be used is set according to these cases. .

In FIG. 3B, when there is a grouping, the ports used in the conference group 1 are P0 to P
7, indicating that the ports used by the conference group 2 are P8 to P15, and that no grouping is used indicates that the ports used by the conference group 1 are P0 to P15.

FIG. 4 shows a table stored in the main storage device 17, which is connected to the conference call device 15, and which port of the conference call device 15 is connected to the wireless terminal device that is in a conference call. It is a conference call device use state table which stores whether it is in use. The conference call device use state table 400 is provided with a port number area 402 in which a port number of the conference call device 15 in use is stored for the wireless terminal device number 401. In addition,
Based on this table, the use state of the conference call device 15 is recognized, and the connection of the conference call is restricted.

FIG. 5 is a table stored in the main storage device 17 and is a terminal status table indicating the status of the wireless terminal device. The terminal status table 500 is provided with a connection status area 502 for storing status information indicating the connection status for the wireless terminal device number 501.
The connection status area 502 stores information indicating any one of “during a conference call”, “not connected”, or “no conference setting”.

Next, the operation of the present invention will be described.

FIGS. 6 and 7 are connection sequence diagrams showing an outline of the operation of the conference call system according to the present invention, and FIGS. 8 to 11 are flowcharts showing conference call processing of the central control unit of the exchange. This is done to implement the connection sequence diagrams shown in FIGS.

Hereinafter, the conference call connection operation will be described. FIG.
, When the power switch of the exchange device 1 is turned on (S
601), the processing shown in FIG. 8 is performed. That is, first, an initial process is performed (S801). Specifically, the conference call device use state table 400 shown in FIG. 4 is cleared, and the terminal state table 500 shown in FIG. 5 is cleared. In the clearing of FIG. 5, the connection state area 502 corresponding to the wireless terminal device numbers PS1 to PS12 is set to “not connected”, and the wireless terminal device numbers PS13 to PS12 are set.
The connection state area 502 corresponding to No. 16 is set to “no conference setting”
Set as The wireless terminal device to be set to “no conference setting” is extracted from preset station data (conference call connection table 300) shown in FIG.

As described above, after executing the initial processing, online processing is performed (S802). This online processing includes a calling routine shown in FIG. 9, a conference connection routine shown in FIG. 10, a disconnection processing routine, and the like. These routines are periodically (for example, 100 to 2000 ms).
(Period).

Returning to FIG. 6, next, the central control unit 16
Sends a call request to the wireless base station 3 so as to send a call signal to all wireless terminal devices 4 to be conferenced (S602). This processing is performed by executing a periodically invoked calling routine shown in FIG.

In FIG. 9, first, the terminal status table 500 shown in FIG. 5 is accessed, and a wireless terminal device whose connection status area 502 is “unconnected” is extracted (S 90).
1). Next, it is determined whether there is a wireless terminal device whose connection state is “unconnected” (S902). If there is no wireless terminal device that is “unconnected”, the process ends.

By the way, since the state of step S602 in FIG. 6 is a state where online has been started, all of the wireless terminals to be conferenced are "unconnected" and all wireless terminals (for example, wireless terminals) PS1 to PS12) are called wireless terminal devices. Next, in order to call all the wireless terminal devices to be called, the central control device 16 sends all the wireless base stations 3 via the digital wireless interface device 12 to the wireless terminal devices to be called (when the connection state area 502 is changed). A request is made to call up all wireless terminals set to “not connected” (S90)
3), this process ends. FIG. 13 shows the state at this time.

Returning to FIG. 6, on the other hand, when the power is turned on, each of the wireless terminal devices 4 establishes a link (including position registration) with the wireless base station 3 in the currently located area according to a predetermined sequence ( S603). Here, all the wireless base stations 3 are connected to all the wireless terminal devices 4 in step S602.
Immediately after the link is established (if the link has already been established, immediately after receiving the call request from the central control device), the wireless terminal device 4 with which the link has been established Send a ringing signal.

Then, the wireless terminal device 4 with which the link has been established detects the incoming call that has received the calling signal and sends out a ringing tone (S604). Next, a response signal is sent to the wireless base station 3 to which a link has been established by a manual response in which the owner of the wireless terminal device 4 presses the response button 42 or an automatic response of the wireless terminal device 4 (S605). Is transmitted (S606). On the other hand, the central control device 16 detects the response signal via the wireless base station 3 and the digital wireless interface device 12 (S607), and places the wireless terminal device 4 which has sent the response signal to an empty port of the conference communication device 15. The connection is established, and a call is set between the wireless terminal device 4 and the conference call device 15 (S608). This step S6
07 and step S608 are performed by executing a periodically activated conference connection routine shown in FIG.

In FIG. 10, first, a response state to a call of the wireless terminal device 4 is recognized (S1001), and it is determined whether or not there is a response (S1002). If the result of this determination is that there is no response, the process ends. On the other hand, if there is a response, after recognizing the responding wireless terminal device, FIG.
The conference call connection table 300 shown in FIG.
The conference group to which the wireless terminal device belongs and the port of the connectable conference call device 15 are recognized based on the conference call device assignment table 350 shown in FIG. After this,
It is determined whether there is an empty port connectable to the conference call device 15 based on the conference call device use state table 400 shown in FIG. 4 (S1003).

If the result of determination in step S1003 is that there is no empty port, invalidation processing for invalidating the response is executed (S100).
1004), the process ends. On the other hand, if there is an empty port, the time switch 10 and the digital wireless interface device 1 capture one of the empty ports and set up a call between the captured empty port and the wireless terminal device 4 that has responded.
2 and the wireless base station 3 (S1005). Thereafter, the port number of the connected conference call device 15 is stored in the port number area 402 corresponding to the wireless terminal device that responded in the conference call device use state table 400 shown in FIG. The connection state area 502 corresponding to the wireless terminal device number 501 that has responded to the request is set to “conference call in progress” (S1006), and the process ends.

Returning to FIG. 6, these processes are performed for all the wireless terminal devices, and the wireless terminal device that has returned a response signal to the calling signal from the wireless base station 3 is
Connect to an empty port of the conference call device 15. As a result, the plurality of wireless terminal devices to be connected to the conference call enter a conference call state (S609).

When there is a wireless terminal device that does not return a response signal even after performing the above-described calling process,
That is, when the wireless terminal device is located in a place that does not belong to the area of all the wireless base stations 3 and cannot establish a link with the wireless base station and cannot recognize the call of the switching device 1, Is processed.

When no response is made to the call from the switching device 1, the connection status area 502 for the wireless terminal device number 501 that does not respond to the call in the terminal status table 500 shown in FIG. 5 is set to "not connected". In such a state, when the calling routine (FIG. 9) started periodically as described above is executed, in step S901, a wireless terminal device that does not respond to the call set to “not connected” is extracted. Then, in step S902, it is determined that there is no connection, and in step S903, a request is made to all the wireless base stations 3 via the digital wireless interface device 12 to call the wireless terminal device in the “unconnected” state.

This state will be described with reference to FIGS. 13 to 15. As shown in FIG. 13, the system is in an operation (on-line) state, and the switching device 1 transmits to all the radio base stations 3 radios for conference calls. Request to call the terminal. On the other hand, a wireless terminal device belonging to the area of one of the wireless base stations 3 establishes a link with the wireless base station, responds to the call, and enters a conference call state. At this time, a wireless terminal device that does not belong to the area of the wireless base station 3 (the wireless terminal device PS3 in FIG. 13) cannot recognize the call. Then, as shown in FIG. 14, a continuous request is made to call the wireless terminal device (PS3).

Thereafter, as shown in FIG. 15, when the wireless terminal device (PS3) enters the area of one of the wireless base stations 3 and establishes a link with the wireless base station 3, the conference connection started periodically. The conference call is connected by the routine (FIG. 10).

That is, steps S1001 and S1002
When a response is detected in step S1003 and it is determined in step S1003 that there is an empty port of the conference communication device 15, step S1
According to 005, a call is set between the empty port of the conference communication device 15 and the responding wireless terminal device (PS3). Next, in step S1006, the wireless terminal device (PS3) responding to the conference call device use state table 400 shown in FIG.
, The port number of the connected conference call device 15 is stored in the port number area 402, and the responded wireless terminal device (PS3) in the terminal status table 500 shown in FIG.
Is set to "during conference call".

As described above, when a wireless terminal device located in a place that does not belong to the area of the wireless base station 3 belongs to the area of the wireless base station 3, a conference call connection is established.

Next, the operation when the wireless terminal device during a conference call moves to a place that does not belong to the area of all the wireless base stations 3 will be described.

As shown in FIG. 16, when the wireless terminal device (PS4) during a conference call moves to a place that does not belong to the area of the wireless base station 3, the link with the wireless base station 3 is released,
Accordingly, the wireless base station 3 sends the disconnection signal to the central control unit 1.
Send to 6. On the other hand, the central controller 16 detects the disconnection signal and executes a call disconnection process by executing a periodically activated disconnection process routine shown in FIG.

In FIG. 11, it is determined whether or not a disconnection signal has been transmitted from the radio base station 3 (S1101). If no disconnection signal has been transmitted, the process ends. On the other hand, when the presence of the disconnection signal is recognized, the disconnection signal is decoded, and the wireless terminal device (the wireless terminal device PS4 in FIG. 16) that disconnects the call is specified. Next, the port number area 402 for the disconnected wireless terminal device (PS4) in the conference call device use state table 400 shown in FIG. 4 is cleared, and between the conference call device 15 and the wireless terminal device (PS4). The time switch 10, the digital wireless interface device 12, and the wireless base station 3 are controlled so as to disconnect the call, and the connection status area for the disconnected wireless terminal device (PS4) in the terminal status table 500 shown in FIG. 502 is set to "not connected" (S1102), and the process ends.

As described above, when the call related to the conference call is disconnected and the connection status area 502 for the disconnected wireless terminal device (PS4) in the terminal status table 500 shown in FIG. 5 is set to “not connected”, As described above, when the calling routine shown in FIG. 9 is activated, the wireless terminal device (PS4) set to “not connected” is extracted, and the wireless terminal device (PS4) is extracted as shown in FIG. A request is made to all radio base stations 3 via the digital radio interface device 12 to call.

Next, the operation when the radio terminal device (PS4) moves to a place belonging to the area of the radio base station 3 as shown in FIG. 18 will be described with reference to the connection sequence diagram of FIG.

When the wireless terminal device (PS4) moves to a place belonging to the area of the wireless base station 3 (S702), a link is established with the wireless base station 3 in the area where the wireless terminal is located by a predetermined sequence. Here, all the wireless base stations 3 are requested to continuously call the wireless terminal device (PS4) in step S703 (the calling routine in FIG. 9). A call signal is transmitted to the device (PS4).

Then, the wireless terminal device (PS4) detects the incoming call that has received the calling signal and sends out a ringing tone (S704). Next, a response signal is transmitted to the wireless base station 3 to which a link has been established by a manual response in which the owner of the wireless terminal device 4 presses the response button 42 or by an automatic response of the wireless terminal device 4 (S705). (S706).
On the other hand, the central control device 16 detects the response signal via the wireless base station 3 and the digital wireless interface device 12 (S707), and sets the wireless terminal device (PS4) that has transmitted the response signal to the idle state of the conference communication device 15. It connects to the port and sets up a call between the wireless terminal device (PS4) and the conference call device 15 (S708). This step S607
The process of step S608 is performed by executing a periodically activated conference connection routine shown in FIG.

As described above, when a wireless terminal device located outside the area of the wireless base station 3 moves to a place belonging to the area of the wireless base station 3, a conference call connection is immediately established.

Next, the integration and separation of conference groups will be described.

FIG. 19 is a diagram for explaining the outline of the integration / separation of conference groups, and FIG. 12 is a processing flowchart of the central control unit when the integration / separation of conference groups is performed.

First, upon recognizing a conference group switching request ((1) in FIG. 19) from the control terminal device 2 via the line interface device 11 (S1201), it is determined whether a conference call is currently being made in one conference group. It is determined (S1202), and if a conference call is being made in one conference group, a request to separate into a plurality of conference groups is made as predetermined in the conference call device allocation table of FIG. 3B. (S120)
3) Separating the conference call into a plurality of conference groups (S1)
204). That is, by referring to the conference call device allocation table of FIG. 3B (FIG. 19B), the port group of the conference group 1 and the port group of the conference group 2 are recognized, and the settings are made as in these settings. The conference communication device 15 is controlled so as to separate the conference groups ((3) in FIG. 19).

On the other hand, in step S1202, when it is recognized that a conference call is being made in a plurality of conference groups,
As determined in advance in the conference call device allocation table of FIG. 3B, it is recognized that a request to integrate into one conference group has been made, and the conference call is integrated into one conference group (S1203). That is, similarly, FIG.
(2) in FIG. 19, and recognizes the port group of the conference group, and controls the conference phone 15 to integrate the conference group according to these settings (FIG. 19 (2)). ((3) of FIG. 19).

As described above, the conference group integration / separation processing is performed based on the request from the control terminal device.

[0061]

As described above, according to the present invention, when the switching device is operated (on-line), a plurality of wireless terminals can be operated without any operation by a caller (conference convener). The device can be automatically called and a communication connection in a conference call state can be made.

Further, when the wireless terminal device moves into the area from outside the area where the radio signal can be transmitted and received, the caller does not perform any operation, and the mobile terminal device that has moved does not participate in the conference call again. Can be done.

Further, it is possible to provide a function of integrating conference calls of a plurality of groups into one group, and conversely, separating a conference call of one group into a plurality of groups.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing a conference call system of the present invention.

FIG. 2 is an external view of a wireless terminal device of the present invention.

FIG. 3A illustrates a configuration of a conference call connection table. (B) is a diagram showing a configuration of a conference call device allocation table.

FIG. 4 is a diagram showing a configuration of a conference call device use state table;

FIG. 5 is a diagram showing a configuration of a terminal status table indicating the status of the wireless terminal device.

FIG. 6 is a connection sequence diagram showing an outline of the operation of the conference call system according to the present invention.

FIG. 7 is a connection sequence diagram illustrating an outline of an operation of the conference call system according to the present invention.

FIG. 8 is a flowchart showing a conference call process of the central control device.

FIG. 9 is a flowchart showing a calling routine.

FIG. 10 is a flowchart showing a conference connection routine.

FIG. 11 is a flowchart illustrating a disconnection processing routine.

FIG. 12 is a flowchart illustrating a conference group setting processing routine.

FIG. 13 is a state diagram illustrating the operation of the present invention.

FIG. 14 is a state diagram illustrating the operation of the present invention.

FIG. 15 is a state diagram illustrating the operation of the present invention.

FIG. 16 is a state diagram illustrating the operation of the present invention.

FIG. 17 is a state diagram illustrating the operation of the present invention.

FIG. 18 is a state diagram illustrating the operation of the present invention.

FIG. 19 is a diagram illustrating an overview of integration / separation of conference groups.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Switching device 2 Control terminal device 3 Radio base station 4 Radio terminal device 10 Time switch 11 Line interface device 12 Digital radio interface device 13 Office line interface device 14 Dedicated line interface device 15 Conference call device 16 Central control device 17 Main Storage device

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shoji Makita 3-14-14 Kandanishikicho, Chiyoda-ku, Tokyo NS Building Matsuda Tsusho Co., Ltd. (72) Inventor Tetsuya Nishikawa 94-Fujiba, Koriyama-shi, Fukushima JP-A-62-48134 (JP, A) JP-A-2-252325 (JP, A) JP-A-7-154488 (JP, A) JP-A-6-505838 (JP) , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H04B 7/24-7/26 H04M 3/42-3/62 H04Q 7/00-7/38

Claims (3)

(57) [Claims] 1. A conference call system using a wireless terminal device including a plurality of wireless terminal devices and a switching device accommodating a plurality of wireless base stations and a conference call device, wherein the switching device includes: A table for storing a connection state between the plurality of wireless terminal devices and the conference call device; a unit for recognizing a wireless terminal device that is not connected to the conference call device by the table; Means for continuously transmitting a call request of a certain wireless terminal device to all of the plurality of wireless base stations; and detecting a response signal from any of the plurality of wireless terminal devices, the wireless device transmitting the response signal. Means for connecting a terminal device to an empty port of the conference call device, wherein when the switching device is in an operating state, a call for setting up a conference call between the plurality of wireless terminal devices is automatically performed. Conference call system using the radio terminal apparatus characterized and. 2. The plurality of wireless base stations further comprising means for sending a disconnection signal to the switching device when a wireless terminal device moves out of the area of the plurality of wireless base stations, wherein the switching device includes Means for identifying the wireless terminal device that has transitioned to the disconnected state when a signal has been detected, and indicating in the area of the table corresponding to the wireless terminal device that has transitioned to the disconnected state that the conference call device has not been connected. 2. A conference call system using a wireless terminal device according to claim 1, further comprising means for setting information. 3. A conference call connection table for registering, in the switching device, a wireless terminal device group for one conference group and a wireless terminal device group for each conference group for a plurality of conference groups; 2. A conference call using a wireless terminal device according to claim 1, further comprising control means for referring to the conference call connection table when recognizing a group switching request and separating and integrating conference groups. system.