Communication conference system

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a multimedia communication conferencing system that includes video and audio.

【0002】

[Conventional technology]

Conventional communication conferencing systems are mainly those that connect conference rooms between two points via a wide area network. This system configuration is as shown in FIG. 14, for example, and captures and reproduces the remarks of a plurality of participants and a video system consisting of a camera 903 and a television 902 capable of capturing images of a plurality of participants and displaying the images. A communication terminal device 90 having a voice system consisting of a microphone 906 and a speaker 904 is basically configured by connecting a wide area network 960. Participants can be captured by the camera 903, the other participants can be projected by the TV 902, and opinions can be exchanged and discussed using the microphone 906 and the speaker 904. This allows you to hold immersive meetings even when you are far away, saving you money and time attending meetings. Here, the connection control device 901 is a device that controls these elements. And such a system is connected via a communication network (wide area network) 960 such as an INS network, so that a conference can be held even if they are separated from each other.

【0003】

One of the problems with such a conventional teleconferencing system is that it is necessary to gather in a conference room at the time of a conference. Normally, there is only one such conference room in one office, and the living room and the conference room are separated, and it is troublesome to manage the conference room and give and receive keys, so you can talk far from your seat using the telephone. It is inconvenient compared to that. In addition, it is difficult for participants from three or more business establishments to participate in the conference at the same time. In addition, the number of people who can participate in the conference room is at most 10 people. Figure 15 shows an example of the configuration of a conference room in a conventional remote conference system.

【0004】

In order to solve this inconvenience, a distributed conference system as shown in FIG. 16 in which one conference terminal is assigned to each conference participant has been devised. In this system, multimedia conference terminals 910-1 to 910-3 that handle voice, video, text data, etc. are housed in connection control devices 920-1 to 920-3 and connected to the communication network 960. The multipoint communication control device 930 is connected to the connection control devices 920-1 to 920-3 in a star shape using a communication network such as an optical fiber cable. Multimedia data such as audio, video, and text data is efficiently transmitted by B-ISDN (Broadband Integrated Services Digital Network) technology using ATM (Asynchronous Transfer Mode) technology. FIG. 17 shows an example of the display on the display 911 of the conference terminal in the distributed conference system shown in FIG.

【0005】

By the way, at the meeting, there are members who speak frequently and members who speak only occasionally and listen incessantly. Therefore, the transmission line can be used efficiently if the distribution and processing of the transmission line are grouped and used so that the transmission line can be provided to the members who frequently speak. However, in the distributed conference system shown in FIG. 16, the multimedia conference terminals 910-1 to 910-3 are connected one-to-one to the connection control devices 920-1 to 920-3. Therefore, if you want to increase the number of conference participants, you need to add more connection control devices, which naturally limits the number of conference participants, and you can connect to only 10 terminals and 10 conference participants at most. Cannot provide service. In addition, since it is necessary to connect optical fiber cables between the connection control devices 920-1 to 920-3 and the multipoint communication control device 930, the number of optical fiber cables increases as the number of conference participants increases. Then, even if the conference participants are not so far apart, for example, even if they are in the same room or on the same floor, in order to provide services to the terminals, the connection control devices 920-1 to 920-3 are connected from the multipoint communication control device 930. You have to pull the fiber optic cable. Therefore, in order to hold a communication conference with a large number of people, it is necessary to add an optical fiber cable and a connection control device, which increases the cost required for the equipment.

【0006】

[Problems to be Solved by the Invention]

As mentioned above, in the conventional conference room type remote conference system, it is necessary for the conference participants to gather in the conference room, and in the distributed conference system using the conference terminal, it is necessary to install equipment for laying optical fiber cables. Due to the cost involved, the number of conference participants was limited, and the line usage efficiency was poor.

【0007】

An object of the present invention is to solve these points and to realize a distributed conference system with high line usage efficiency in which a large number of users can participate by using a relatively short line with a small number of lines.

【0008】

[Means for solving problems]

In a communication conference system in which a conference terminal that handles multimedia information consisting of video signals, audio signals, and data is connected via a communication network and multiple conference participants hold a communication conference at multiple points, the video and audio signals are transmitted by radio waves or. A spatial propagation device that converts to an optical signal and sends and receives, a concentrator that selectively synthesizes video signals from the spatial propagation device and selectively adds audio signals, and sends video and audio signals from the concentrator to a communication network. It is provided with a connection control device for performing communication and a multipoint communication control device for controlling a communication conference by selectively synthesizing video signals from a large number of connection control devices and selectively adding audio signals.

【0009】

Furthermore, the video signal selectively synthesized by the multipoint communication control device and the audio signal subjected to the selective addition processing are transmitted to the connection control device via the communication network, and the video signal and the audio signal are distributed to a large number of spatial propagation devices. , Provide means to provide communication conference services to a large number of conference terminals.

【0010】

Further, a plurality of connection control devices are divided into several groups, communication lines required for each group are connected to the multipoint communication control device, and video signal and audio signal processing is performed for each of the divided groups. To do.

【0011】

[Action]

According to the present invention, it is possible to realize a distributed conference system with efficient use of transmission lines in which a large number of users can participate by using a relatively short line with a relatively small number of lines, and the equipment cost is economical. Can be achieved. Further, by dividing the conference participants into groups, the transmission line can be used more efficiently.

【0012】

[Example]

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

【0013】

FIG. 1 is a diagram showing a configuration of a distributed conference system according to an embodiment of the present invention.

【0014】

This system is connected to or from the multipoint communication control device 30 and the connection control devices 20-2 and 20-3 that can directly accommodate the conference terminals 10-1 and 10-2, and the terminals 10-3 to 10-5. Video / audio text data transmitter / receiver 50-, which is a spatial propagation device that converts signals such as audio / video / text data from control device 20-1 to terminals 10-3 to 10-5 into wireless signals on radio waves and transmits / receives them. 1 to 50-4, a large number of spatial propagation devices, a concentrator 40 for selectively compositing media such as video, audio, and text data sent to the shell, and a concentrator 40 for selective compositing and output. The connection control device 20-1 that outputs signals such as voice and text data to the communication network 60, and the communication network 60 are configured as elements. As the communication network 60 to which the multipoint communication control device 30 and the connection control devices 20-1, 20-2, 20-3 are connected, an ATM wide area network such as B-ISDN or an ATM-LAN as a premises network ( ATM-Local Area Network) and STM (Synchronous Transfer Mode) multimedia LAN can be used.

【0015】

FIG. 2 shows an example of the installation state of the conference terminal in this embodiment. The conference terminal 10 is composed of a video system composed of a camera 103 and a terminal body 101, an audio system composed of a microphone and a speaker 104 or headphones, a spatial propagation device (video / audio text data transmitter / receiver 50 in the figure), and the like. To.

【0016】

The video from the camera 103 and the sound from the microphone are once collected by the line concentrator 40 via the spatial propagation device 50, and then the multipoint communication control device 30 located far away via the connection control device 20-1 and the communication network 60. Will be sent to. The video and audio are selectively combined and distributed to the conference terminals 10-1 to 10-5 connected to each connection control device 20-1 to 20-3, whereby each conference participant can participate in other conferences. You can listen to people's voices and watch videos. The conference terminal 10 is composed of a connecting device, a workstation connected to the connecting device, or a personal computer. Workstations and personal computers have a built-in video board and are sent directly from connection control devices 20-1 to 20-3 to terminals 10-1 and 10-2, or from spatial propagation device 50 to terminal 10-3. The video sent to ~ 10-5 can be displayed in the window of the screen.

【0017】

As a result, terminals 10-1 and 10-2 can perform communication conferences through the connection control devices 20-2 and 20-3 and the multipoint communication control device 30, and terminals 10-3 to 10- with a concentrator 40 or less. 5 can also receive conference services.

【0018】

Furthermore, in the case of terminals 10-1 and 10-2, the multipoint communication control device 30 divides the conference participants into two groups according to the degree of participation in the conference, and the conference terminals 10-1 and 10-2 are referred to as panela terminals. Divide into floor terminals. Then, as a device that sets the communication line for each group according to the attributes of the group to which it belongs and processes the video and audio for each group, it has a function to support the requests from the panela group and the floor group. ing. For the processing of the panela group, the multipoint communication control device 30 has the call control unit 303 connecting bidirectional lines to the connection control devices 20-2 and 20-3 at each terminal 10-1 and 10 -Set every 2. On the other hand, for floor group processing, a one-way distribution downlink line is set between the connection control devices 20-2 and 20-3, and a broadcast distribution line for multiple destinations is set on the floor terminal. Then, if a question or the like is uttered from the floor terminal, an uplink is set from one of the terminals.

【0019】

Figure 3 shows the configuration of the multipoint communication control device 30.

【0020】

The line I / F section 304 has a main function of interfacing the device with the communication network 60, and further has a function of converting each medium into an ATM. The video processing unit 301 performs reduction processing by thinning out pixels, composition processing of a plurality of video signals, video selection processing, and the like. The voice processing unit 302 performs N-1 addition processing for adding only its own voice from the voice signals from each terminal 10, loss insertion processing corresponding to the number of added signals, speaker detection processing, and overload processing. Then, the added signal is distributed to the terminals 10 connected to each connection control device 20. Further, the data processing unit 310 includes a data transmission / reception function, performs speech processing for a speech request from each terminal 10, and performs control communication. Control unit 311 manages the conference.

【0021】

At the start of the conference, the call control unit 303 sets a one-way downlink for video and audio for the floor group, and the multipoint communication control device 30 and each terminal 10 use the copy function in the communication network 60. Set up a tree-shaped distribution line. On the other hand, when the floor group terminal wants to ask a question during a meeting, the terminal sets a data line from the data processing unit 310 and makes a speech request, and in response to this, the multipoint communication control device 30 of the terminal that requested the speech. Speak control is performed to select a remark from any one of them. Then, an ascending video / audio line is set between the terminal and the multipoint communication control device 30, and the video signal from the selected terminal is transmitted to the video processing unit 301 and the audio signal is transmitted to the audio processing unit 302. Video composition, switching, or audio addition processing is performed, respectively. After that, these signals are transmitted from the video processing unit 301 and the audio processing unit 302 to each terminal and distributed. Normally, only one-way downlink line to the terminal 10 side is set between the multipoint communication control device 30 and the floor group connection control device 20, but if necessary, the terminal 10 can be asked a question or the terminal 10 can ask a question. To participate in the discussion, go up from the terminal 10 to the multipoint communication control device 30 side via the connection control device 20, set the lines individually, or to collect the opinions from the terminal 10 all the terminals 10. Therefore, it is possible to set a one-way simultaneous line that goes up to the multipoint communication control device 30 side and collect information all at once. As a result, the participants of the floor group terminal usually listen to and hear the situation of the conference terminal, and only communicate with each other between the floor group terminals, but they get the right to speak if necessary. You can ask questions, or all terminal participants can participate in the vote.

【0022】

In this explanation, the conference terminal 10 is divided into two groups in advance, but it is possible to transfer the group to which the terminal belongs while the conference is in progress. It is also possible to change the group affiliation of each terminal by controlling the multipoint communication control device 30 side based on the frequency of remarks during the conference and replace the members.

【0023】

Figure 4 shows the configuration of the connection control device 20.

【0024】

The line I / F unit 206 receives the video signal from the video transmission / reception unit 201, the audio signal from the audio transmission / reception unit 202, the call control data from the call control unit 203, and the data from the data transmission / reception unit 204 and multiplexes them in the ATM cell. Then, it is transmitted to the multipoint communication control device 30 via the communication network 60. On the contrary, the signal from the multipoint communication control device 30 is received via the communication network 60, and each signal is separated to form a video transmission / reception unit 201, an audio transmission / reception unit 202, a call control unit 203, and a data transmission / reception unit 204. Send to.

【0025】

When the connection control device 20 is connected like the terminal 10-1 of group B or the terminal 10-2 of group C in FIG. 1, the video transmission / reception unit 201 is the video board and camera built in the terminal 10. It is connected to 103 and digitizes the NTSC signal from camera 103 and sends it to line I / F section 206. In addition, the signal from the line I / F section 206 is converted to analog and sent to the video board built into the terminal 10. The audio transmission / reception unit 202 performs coding / decryption processing of the audio signal connected to the microphone and the speaker 104, and performs transmission / reception processing with the line I / F unit 206. The data transmission / reception unit 204 is connected to the terminal 10 and can send data from the terminal 10 to the multipoint communication control device 30 or send data stored in the multipoint communication control device 30 to the terminal 10. it can.

【0026】

On the other hand, in the connection control device 20-1 connected to the concentrator 40 belonging to group A, the video transmission / reception unit 201, the audio transmission / reception unit 202, and the data transmission / reception unit 203 are connected to the concentrator 40, and the video, audio, and data signals are video. / Voice / Text Data is distributed to each terminal 10-3 to 10-5 via the data transmitter / receiver 50. Further, the video, audio, and data signals from the terminals 10-3 to 10-5 are collected in the line concentrator 40 by the video / audio / text data transmitter / receiver 50, and the audio and video are subjected to selective composition processing. It is sent to the multipoint communication control device 30.

【0027】

Call control unit 203 supports control / monitoring of line I / F unit 206 and connection control to lines such as video, audio, and data. The control unit 205 is connected to the video transmission / reception unit 201, the audio transmission / reception unit 202, the call control unit 203, and the data transmission / reception unit 204 via the control highway 208, and manages each of them.

【0028】

5 to 8 show the functions of the video / audio / text data transmitter / receiver 50 shown in FIG. 1 divided into a transmitter and a receiver.

【0029】

FIG. 5 shows the configuration of the video / audio / text data transmitter used on the terminals 10-3 to 10-5. The video / audio / text data transmitter amplifies the video signal (video signal of the conference participants themselves) input from the camera 103 with the video amplifier 501, and then determines the frequencies f4, f5, and f6 used in each device. Modulate by the video carrier generator 504 and AM modulator 503. Further, the sound from the microphone 106 is amplified by the voice amplifier 506 and modulated by the voice carrier generator 508 and the FM modulator 507. Further, the text data from the terminal body 101 is modulated by the data carrier generator 510 and the FM modulator 509. Then, the AM-modulated video signal and the FM-modulated audio signal and text data are mixed and synthesized by the mixing synthesizer 505, and the video / audio / is connected to the concentrator side by the antenna 511 as a radio wave radiator. Send to the text data receiver.

【0030】

Figure 6 shows the configuration of the video / audio / text data receiver used on the terminals 10-3 to 10-5. The video / audio / text data receiver receives video, audio, and text data from the video / audio / text data transmitter connected to the line concentrator 40. The received video, audio, and text data are those of the downlink processed by the multipoint communication control device 30. That is, the video signal is obtained by synthesizing the video signal sent from another terminal and the video signal from the terminals 10-3 to 10-5 connected to the line concentrator 40 or less, and the multipoint communication control device 30 again. The audio signal is a combination of the audio signal sent from another terminal and the audio / video signal from terminals 10-3 to 10-5 connected to the concentrator and below. This is the result of selective addition processing again by the point-to-point communication control device 30. In the receiver, after high-frequency amplification and frequency conversion with the tuner 512, in order to extract video, audio, and text data, video intermediate frequency amplification 513, audio intermediate frequency amplification 515, and text data intermediate frequency amplification 518 are performed, and then detection is performed. The video signal is AM-detected and the audio and text data are FM-detected by the circuits 514, 516 and 519, and the video signal, audio signal and text data are extracted. After the video signal is extracted, it is input to the video controller board built in the terminal body 101 and displayed on the display. The audio signal is output from the speaker 104 or headphones. Further, the text data is converted to a level corresponding to the terminal interface such as RS-232C and output to the terminal main body 101.

【0031】

Figure 7 shows the configuration of the video / audio / text data receiver installed on the concentrator 40 side. This video / audio / text data receiver receives video, audio, and text data that have passed through the video / audio / text data transmitter from terminals 10-3 to 10-5.

【0032】

The received video, audio, and text data are combined and added by the line concentrator 40, and then sent to the communication network 60 by the connection control device 20-1 as a line to control multipoint communication. Processed by device 30. That is, in the case of video, the video signal transmitted from another terminal and the video signal from terminals 10-3 to 10-5 connected to the concentrator 40 or less are transmitted from the other terminal in the case of audio. It receives the received audio signal and the audio signal from terminals 10-3 to 10-5 connected to the line concentrator 40 or less. These signals are high-frequency amplified and frequency-converted by the tuner 512, and then subjected to video intermediate frequency amplification 513, audio intermediate frequency amplification 515, and text data intermediate frequency amplification 518 in order to extract video, audio, and text data. After that, the video signal is AM-detected, the audio, and the text data are FM-detected, and the video signal, audio signal, and text data are extracted.

【0033】

FIG. 8 shows the configuration of the video / audio / text data transmitter installed on the concentrator 40 side. Video, audio, and text data are transmitted from the multipoint communication control device 30 to terminals 10-3 to 10-5 via a communication network. The transmitter uses the video amplifier 501 to amplify the video signal that represents the conference participants themselves, which is output from the connection control device 20-1 to the concentrator 40, and then uses the video carrier generator 504 according to the frequency used by each device. Modulation is performed by the AM modulator 503. The audio output from the connection control device 20-1 to the concentrator 40 is amplified by the audio amplifier 506 and modulated by the audio carrier generator 508 and the FM modulator 507. Further, the text data from the terminal body 101 is modulated by the data carrier generator 510 and the FM modulator 509. Then, the AM-modulated video signal and the FM-modulated audio signal and text data are mixed and synthesized by the mixing synthesizer 505, and the video / audio / text connected to the terminal side by the antenna 511 as a radio wave radiator. Send to the data receiver.

【0034】

FIG. 9 shows the configuration of the image unit 401 of the concentrator 40. The video unit 401 is composed of an AD conversion unit 4011, a video selection / synthesis unit 4012, a frame synchronization unit 4013, and a DA conversion unit 4014, and is transmitted on radio waves or light from terminals 10-3 to 10-5 and propagates in space. The video signal output from the video / audio / text data transmitter / receiver 50-1 as a device is input, synchronized as an NTSC or RBG video signal, and the video signal is synthesized. At the time of compositing, select the video and decide which terminal to display the video signal on one compositing screen. For example, control such as displaying only the image from the terminal 10-3 or synthesizing the images from the terminals 10-3 to 10-5 and displaying them on one screen is performed.

【0035】

FIG. 10 shows the configuration of the image selection / compositing unit 4012 in the image unit 401 of the concentrator 40.

【0036】

The video signal digitized by the AD conversion unit 4011 and output from the frame synchronization unit 4013 is determined by the video selection control signal which video is to be combined by the video selection unit 40121, and the size of the screen for composition is determined. It is converted in size via a size conversion filter (consisting of both vertical and horizontal filters) 40122, stored in the size conversion memory 40123, and then output as a synthesized video signal. The synthesized video signal is DA-converted and returned to the NTSC signal, then input from the concentrator 40 to the connection control device 20-1, further interfaced with the communication network 60, and transmitted to the multipoint communication control device 30. Will be done.

【0037】

FIG. 11 shows the configuration of the frame synchronization unit 4013 in the image unit 401 of the line concentrator 40.

【0038】

The video signals received from terminals 10-3 to 10-5 by the video / audio / text data transmitter / receiver 50-1 have independent phases of the horizontal synchronization signal and the frame synchronization signal, so after synchronization is performed once. Need to be processed. Therefore, when writing to the size conversion memory 40123, the received clock and the frame pulse F2V are used to control the address and write. When reading, the internal clock and internal F2V synchronized with the communication network 60 in the concentrator 40 are used for reading. At this time, it is necessary that the F2V pulse received for the address control of the synchronous memories 40132-1 to 40132-3 and the internal F2V pulse have the same value and do not collide. Therefore, in case of collision, the memory address jump control is performed so as to avoid it.

【0039】

FIG. 12 shows the configuration of the audio addition unit 402 of the line concentrator 40.

【0040】

The audio addition unit 402 is composed of an A / D conversion unit 4021 and a reception buffer 4022. As in the case of video, the audio signals from each terminal 10-3 to 10-5 are AD-converted, then delayed and adjusted, and then STM. It is transmitted to the connection control device 20-1 as a multiplexed audio signal.

【0041】

The multimedia conference terminal 10 realized by the present invention displays conference screens and text data on a large number of windows. Moving images and still images can be displayed on this screen.

【0042】

FIG. 13 shows a display example on the display of the terminal of the multimedia conferencing system realized by the present invention.

【0043】

In FIG. 13, the images from terminals 1 and 2 (10-1, 10-2) are selectively synthesized by the multipoint communication control device 30, and terminals 3, 4 and 5 (10-3 to 10). The images of Group A from -5) are those that have been selectively synthesized by the line concentrator 40 in advance and then again selected and combined by the multipoint communication control device 30. In the video compositing process, if the cutout position and the display position are fixed, the process can be easily executed only by the size change process.

【0044】

In this way, when providing services to conference participant terminals 10 that are in the same room or on the same floor and are only a few meters or a dozen meters apart from each other, video, audio, etc. are converted into radio waves or optical signals for transmission and reception. A space propagation device is provided, and signals from this space propagation device are collected by the line concentrator 40. At this time, the signals from each terminal 10 use radio waves of different frequencies, and the radio wave strength is selected according to the distance. Further, if the line concentrator 40 reproduces, selects, and synthesizes signals and sends them to the connection control device 20, the multipoint communication control device 30 can process these as one group.

【0045】

[Effect of the invention]

As described above, video signals are used in a communication conference system in which conference terminals that handle multimedia information consisting of video signals, audio signals, and data are connected via a communication network and multiple conference participants hold communication conferences at multiple points. A spatial propagation device that converts audio signals into radio or optical signals and transmits / receives them, a concentrator that selectively synthesizes video signals from the spatial propagation device and selectively adds audio signals, and video signals and audio from the concentrator. A connection control device that sends signals to the communication network and a multipoint communication control device that selectively synthesizes video signals from a large number of connection control devices and selectively adds audio signals to control communication conferences are provided. The video signal selectively synthesized by the multipoint communication control device and the audio signal subjected to the selective addition processing are transmitted to the connection control device via the communication network, and the video signal and the audio signal are distributed to a large number of spatial propagation devices. Since the communication conference service is provided to a large number of conference terminals, it is possible to realize a distributed conference system with efficient use of transmission lines in which a large number of users can participate by using a relatively small number of relatively short lines. It is possible to reduce the equipment cost.

【0046】

Further, by dividing the conference participants into several groups and connecting the communication lines required for each group to the multipoint communication control device, the transmission line can be used more efficiently.

[Simple explanation of drawings]

[Figure 1]

Configuration of an embodiment of the communication conferencing system of the present invention.

[Figure 2]

An installation example of the terminal of the communication conference system shown in Fig. 1.

[Fig. 3]

The configuration of the multipoint communication control device of the communication conference system shown in Fig. 1.

[Fig. 4]

The configuration of the connection control device of the communication conference system shown in Fig. 1.

[Fig. 5]

The configuration of the terminal side transmitter of the video / audio / text data transmitter / receiver of the communication conference system shown in Fig. 1.

[Fig. 6]

The configuration of the terminal side receiver of the video / audio / text data transmitter / receiver of the communication conference system shown in Fig. 1.

[Fig. 7]

The configuration of the receiver on the concentrator side of the video / audio / text data transmitter / receiver of the communication conference system shown in Fig. 1.

[Fig. 8]

The configuration of the transmitter on the concentrator side of the video / audio / text data transmitter / receiver of the communication conference system shown in Fig. 1.

[Fig. 9]

The configuration of the video unit of the conferencing device of the communication conference system shown in Fig. 1.

[Fig. 10]

The configuration of the video selection / compositing unit of the video unit shown in FIG.

[Fig. 11]

The configuration of the frame synchronization unit of the video unit shown in FIG.

[Fig. 12]

The configuration of the voice addition unit of the conferencing device of the communication conference system shown in Fig. 1.

[Fig. 13]

A display example on the display of the terminal of the communication conferencing system shown in Fig. 1.

[Fig. 14]

Basic configuration of a conventional teleconferencing system.

[Fig. 15]

The configuration of the conference room of the conventional teleconferencing system.

[Fig. 16]

Basic configuration of a conventional distributed conference system.

[Fig. 17]

A display example on the terminal display of a conventional distributed conferencing system.

[Explanation of symbols]

10,910 conference terminal 20, 920 connection controller 30, 930 Multipoint communication controller 40 Concentrator 50 Video / audio / text data transmitter / receiver 60, 960 communication network 101 Terminal body 102 keyboard 103, 903 camera 104, 904 speakers 106, 906 microphone 201 Connection controller Video transmitter / receiver 202 Connection controller Voice transmitter / receiver 203 Connection control device Call control unit 204 Connection controller data transmitter / receiver 205 Connection controller control unit 206 Connection controller line I / F section 208 Connection controller control highway 301 Multi-point communication controller Video processing unit 302 Multipoint communication controller Voice processing unit 303 Multipoint communication controller Call control unit 304 Multipoint communication controller Line I / F section 310 Multipoint communication controller Data processing unit 311 Multipoint communication controller control unit 401 Concentrator image section 402 Concentrator voice adder 501 Video Audio Text Data Transmitter Video Amplifier 502 Video Audio Text Data Transmitter Sync Signal Generator 503 Video / audio text data transmitter / receiver AM modulator 504 Video Audio Text Data Transmitter Video Carrier Generator 505 Video Audio Text Data Transmitter Mixer Synthesizer 506 Video Audio Text Data Transmitter Audio Amplifier 507 Video Audio Text Data Transmitter Audio FM Modulator 508 Video Audio Text Data Transmitter Audio Carrier Generator 509 Video Audio Text Data Transmitter Text Data FM Modulator 510 Video Audio Text Data Transmitter Text Data Carrier Generator 511 Video / audio / text data transmitter / receiver antenna 512 Video Audio Text Data Transmitter Tuner 513 Video Audio Text Data Transmitter Video Intermediate Frequency Amplifier 514 Video Audio Text Data Transmitter Video Detector 515 Video Audio Text Data Transmitter Audio Intermediate Frequency Amplifier 516 Video Audio Text Data Transmitter Audio FM Detector 517 Video Audio Text Data Transmitter Low Frequency Amplifier 518 Video Audio Text Data Transmitter Text Data Intermediate Frequency Amplifier 519 Video / audio text data transmitter / receiver text data FM detector 520 RS232C level converter 901 Connection controller 902 TV 905 Facsimile 907 Electronic blackboard