JPH06103877B2 - Image communication system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a drawing image communication system, and more particularly to a communication system in a conference mode using an in-home device for drawing image communication equipped with a high-speed modem.

(Prior Art) For example, Japanese Unexamined Patent Publication (Kokai) No. 62-18164 proposes a home device equipped with, for example, a high speed modem of 6400 bps in addition to a low speed modem of 300 bps.

In the image drawing communication system using this kind of home device, as shown in FIG. 5, after transmitting the high speed modem use command on the transmitting side, the receiving side sends the high speed modem use authorization command or the refusal command.

(Problems to be Solved by the Invention) A conventional communication method in which a high-speed modem use authorization command or a rejection command is transmitted from a receiving side to a high-speed modem use command from a transmitting side as in the conventional case is particularly effective in one-to-one communication. Although no problem occurs, in the conference mode, a plurality of in-home devices send the above-mentioned use authorization command or reject command to the high-speed modem use command sent from one in-home device.

If any one of the home devices cannot use the high speed modem at that transmission rate at that time, a lower transmission rate must be adopted as long as it is a conference mode in which communication is common to all the home devices. I won't.

However, since the use authorization command and the reject command as described above are sent from the plurality of home devices, a plurality of response signals collide with each other, and as a result, such a response signal cannot be normally detected at the transmitting side, and the response signal remains unchanged. Communication may occur at the transmission rate. In such a case, there arises an inconvenience that only the specific home device cannot participate in the conference mode.

Therefore, a main object of the present invention is to provide a drawing image communication system capable of eliminating detection error of a response signal.

(Means for Solving the Problems) The present invention relates to a communication mode in a conference mode using a drawing image communication home device equipped with a high-speed modem, in which a line check signal is issued at the transmitting side following a high-speed modem use command. Is sent, the receiving side determines whether or not the line check signal is normally received, and when normally received, the response from another device is monitored for a certain period of time, and the line control is performed according to the monitoring result. It is a picture communication system.

(Function) A signal for line check following a high-speed modem use command from the transmitting side, for example, data "0" that continues for a certain period of time
To send a signal like. The receiving side receives the line check signal and detects whether or not the signal was normally received without error. If there is no error in receiving the line check signal, that is, if transmission / reception of a signal at the transmission rate at that time, for example, 6400 bps is possible, the receiving side does not output a response signal to the high speed modem use command from the transmitting side.

The in-home device, which has determined that the line state is abnormal, sends out a request signal for lowering the transmission rate, for example, in the form of a specific tone signal for a certain period of time.

Therefore, if there is no error, the receiving side only monitors the specific tone signal from the other home device during the fixed time.

When the specific tone signal from any of the home devices is detected, the transmitting side performs fallback of the modem and sets the transmission rate to, for example, 2400 bps. If there is no specific signal from any of the home devices, communication is performed at the current transmission rate, for example, 4800 bps.

(Effect of the Invention) According to the present invention, no response signal is output when normal reception can be performed at the transmission rate at that time, so that a plurality of response signals collide with each other as in the conventional communication method. The problem that is not normally detected is solved.

Furthermore, according to the present invention, since the line status can be checked by the line check signal following the high-speed modem use command, even the home device with the worst line status can communicate at the transmission rate that can be received normally at that time. Therefore, the information can be transmitted to all the home devices participating in the conference mode without error.

Further, if the tone signal is used as the response signal output when the line condition is poor as in the embodiment, even if such tone signals are returned from a plurality of home devices, the signals are overlapped at the transmitting side and normal. There is no problem that can not be detected in. That is, since it is sufficient for the transmitting side to monitor whether or not there is a tone signal, a response signal detection error hardly occurs.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

(Embodiment) FIG. 2 is a block diagram showing an example of a home device to which the present invention can be applied.

This in-home device includes a drawing tablet 10, and a pressure sensitive pad 12 is formed on the drawing tablet 10. The switch 14 provided on the drawing tablet 10 is for instructing simultaneous communication between a drawn image and sound, or for instructing only drawn image communication.

When the paper loaded on the pressure-sensitive pad 12 is hand-painted, the coordinate information is taken into the control unit 16 at a constant sampling cycle. The control unit 16 typically has a built-in microcomputer and supplies the stroke information of the drawn image input from the drawing tablet to the first modem, that is, the low-speed modem 20, via the switch 18. The stroke information of the drawn image given to the low-speed modem 20 is FSK-modulated and input to the demultiplexing circuit 22 together with the voice signal from the telephone 28.
In the demultiplexing circuit 22, for example, 1900 to 2300 Hz of the audio signal
The signal component of the band is removed, and the drawn image information is inserted into the removed band and multiplexed. The multiplexed signal is sent to the telephone line via the switch 26.

The drawn image information is also written in the video memory 32 by the control unit 16 and displayed on the monitor 30.

The received signal input from the telephone line is input to the demultiplexing circuit 22 via the switch 26, where it is separated into a voice signal and a drawn image information signal. The voice signal is given to the telephone 28, and the drawn image signal is demodulated by the first modem, that is, the low speed modem 20, and input to the control unit 16 via the switch 18. The drawn image signal is written in the video memory 32,
Thereby, the drawn image received by the monitor 30 is displayed.

The second or high speed modem 24 is, for example, up to 4800
It can operate at a bps transmission rate and is used for exchanging only drawn image signals. That is, switch 14
When the drawing-only communication is instructed by the control section 16, the switches 18 and 26 are switched by the control section 16 as shown by the dotted line in FIG. 2, and the second modem or high speed modem 24 is connected to the telephone line.

The present invention can be applied to a communication system using a home device equipped with such a high speed modem.

Referring to FIG. 3, on the transmitting side, it is necessary to perform drawing image communication using a high speed modem.
As in the conventional case, the control unit 16 switches the switches 18 and 26 to the low speed modem 20 and sends the high speed modem use command. This high speed modem usage command is therefore
It is transmitted according to the telewriting command format at a transmission rate of 300 bps.

Then, after detecting elapse of 80 milliseconds in step S3, the transmitter side switches the switches 18 and 26 to the high-speed modem 24 by the control unit 16 and activates the high-speed modem 24 in step S5. And through the high speed modem 24,
For example, at 4800 bps, it sends out a line check signal in which data "0" continues for 1.5 seconds.

Then, the transmission side is controlled by the control unit 16 by the switch 18 and
26 is switched to the low speed modem 20, and in step S7,
Monitor the response from other in-home devices participating in the conference mode for a period of time, for example 2.3 seconds. If the response signal is not detected within 2.3 seconds, it goes through step S9 and step S1.
In 1, the necessary drawing image signal is transmitted at the transmission rate at that time, that is, 4800 bps.

If a response signal from another in-home device is detected, the transmission side causes the high-speed modem 26 to fall back to, for example, 2400 bps in step S13, and then proceeds to step S11.
Therefore, the transmission rate of the signal output from the transmitting side at this time is, for example, 2400 bps.

Next, the operation on the receiving side will be described with reference to FIG. As described above, the sending side sends the high speed modem use command, but the receiving side determines in step S101 whether or not there is a high speed modem use command. If there is no high-speed modem use command, the low-speed modem 20 is kept valid and the normal decoding routine is proceeded to.

If the high-speed command is detected, the receiving side switches the switch 18 and the switch 18 in step S103 on the receiving side.
Switch 26 to enable high speed modem 24. Then, after that, in step S105, it is determined whether or not there is a high-speed carrier from the transmitting side. If no high-speed carrier is detected, that is, if a high-speed modem use command is sent from the transmitting side but no high-speed carrier is subsequently received, the state is monitored for a certain period of time, and in step S107, When the time-out is detected, it returns to the main routine.

When the high speed carrier from the transmitting side is detected in step S105, the receiving side checks the received data in step S109. Then, in step S111, it is determined whether data "0" is detected continuously for at least 1 second. That is, as described above, the transmission side outputs a signal in which data "0" continues for 1.5 seconds as the line check signal, so if the line condition is normal, data " 0 "should be detected, and this step S111 determines whether the line state is normal or abnormal based on that.

If the line status is normal, that is, if “Yes” is determined in step S111, the receiving side proceeds to the next step S113.
At 115 and 115, it is determined whether or not there is a response signal from another in-home device for 2.3 seconds.

If there is no response signal, the process proceeds to step S117 to detect again whether or not there is a high speed carrier from the transmitting side. If there is a high-speed carrier, in step S119, the drawn image signal transmitted from the transmission side is transmitted through the high-speed modem 24 at the transmission rate set at that time, that is, 4800 bp.
Receive with s.

If no high-speed carrier is transmitted from the transmitting side for a certain period of time even if there is no response signal from any of the home devices, in the home device, the process proceeds to step S121.
And returns to the main routine.

When it is detected in the previous step S111 that the line condition is bad, the receiving side activates the low-speed modem 20 by the control unit 16 in step S125, and the mark composed of the tone signal of the specific frequency is transmitted at the transmission rate of 300 bps. The signal is transmitted, and in step S123, the control unit 16
Activate the high speed modem 24 again by
Set 24 to a transmission rate of 2400 bps, for example. That is, the receiving side, which has determined that the line condition is bad, sends a mark signal to that effect and then switches on the high-speed modem, for example.
The high-speed carrier from the transmission side is monitored by setting it to the 2400 bps reception state.

As described above with reference to FIG. 3, the transmitter detects such a mark signal in step S7. Therefore, when any device on the receiving side outputs the response signal, the transmitting side uses the high-speed modem 24 to transmit the drawn image signal at a transmission rate of, for example, 2400 bps.

This will be briefly described according to the transmission procedure shown in FIG. When the transmitting side needs to communicate using the high speed modem, the transmitting side sends out a high speed modem use command. On the receiving side, if a high-speed modem is installed in the device, a high-speed modem use authorization command is sent, and if not, a reject command is sent at 300 bps.

The sending side sends a continuous data “0” for 1.5 seconds after sending the high speed modem use command, and executes the line check sequence. In this line check sequence, the receiving side judges whether the line state is normal or abnormal, and if there is a line error, the mark signal is transmitted as described above. The transmitter monitors the response by the mark signal from the receiver during that time, for example, 2.3 seconds. After that, when there is no response signal from any of the receiving side devices, the transmitting side uses a high speed modem to transmit the signal at 4800 bps. When it detects that the mark signal is transmitted from any of the receiving side devices, it starts transmission at a transmission rate of 2400 bps using a high speed modem.

[Brief description of drawings]

FIG. 1 is an illustrative view for explaining a high speed transmission procedure of an embodiment of the present invention. FIG. 2 is a block diagram showing an example of a drawing image communication home apparatus to which the present invention can be applied. FIG. 3 is a flow chart showing the operation of the home device on the transmitting side. FIG. 4 is a flowchart showing the operation of the receiving-side home device. FIG. 5 is an illustrative view showing a conventional high-speed transmission sequence. In the figure, 10 is a drawing tablet, 16 is a control unit, 18, 26
Is a changeover switch, 20 is a low speed modem, and 24 is a high speed modem.

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Claims (3)

[Claims] 1. A communication system in a conference mode using an in-home device for image communication equipped with a high-speed modem, wherein a transmission side sends a line check signal following a high-speed modem use command, and a receiving side transmits the line. A drawing image communication method that determines whether or not a check signal is received normally, and when received normally, monitors the response from other devices for a certain period of time and performs line control according to the monitoring result. 2. The drawing image communication system according to claim 1, wherein, when the reception side is not normally received, a specific signal indicating the fact is transmitted to request a decrease in transmission rate. 3. The drawing image communication system according to claim 2, wherein the receiving side outputs a tone signal as the specific signal.