JPH0292152A - Image communication device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image communication system that executes a processing procedure for determining a transmission speed prior to transmitting image information.

[Conventional technology]

2. Description of the Related Art Conventionally, facsimile apparatuses have been known that are configured to transmit a line status check signal in advance to check whether a channel can be used at a predetermined transmission speed prior to image transmission.

That is, this facsimile device is a G3 standard facsimile device defined by the CCITT-T4 recommendation.

In this type of facsimile machine, prior to high-speed image transmission, the automatic equalizer on the receiver side is adjusted using a training signal and a training check signal to suit the line characteristics, and the result of the adjustment is Determine,
A signal indicating successful training, or
A signal indicating whether or not training has failed and retraining is requested is transmitted from the receiving side to the transmitting side.

The procedure of the G3 image communication system will be explained with reference to FIGS. 8(1) to 8(3).

FIG. 8 (11 to 3) shows an example of the procedure of the conventionally known G3 image communication system. In each of these figures, the signals to the left of the center line are the signals transmitted by the transmitter, and the signals to the right are the signals transmitted by the receiver.

NSF (non-standard equipment) signal, C5I (called station identification) signal, Dis shown above in Figure 8 (1) and (2)
The (digital identification) signal is an initial identification signal, and is a signal for conveying the function of the own machine as a facsimile machine to the other party's machine.

Next, the NSS transmitted from the sender (non-standard device settings)
The TSI (transmitting station identification) signal and the DC5 (digital command) signal are reception command signals and specify the mode in which transmission will be performed. Then, if a TCP (training check) signal is transmitted after that, and a CFR (reception readiness confirmation) signal is transmitted from the receiver in response to that signal,
The transmission speed of the image signal to be subsequently transmitted is determined (see FIG. 8(1)).

The TCF (Training Check) signal is a signal sent through the Group 3 modulation system that verifies training and is the first to indicate whether a channel is available for use at that speed. Its format is a continuous signal of "0" for 1.5 seconds.

The training signal sent just before the TGF signal is a synchronization signal to properly adjust the receiving modem. This synchronization signal is used for carrier detection and, if necessary, for convergence of the 8GC, timing synchronization equalizer, and synchronization of the descrambler.

The CFR (reception readiness confirmation) signal and the FTT (train failure) signal shown in FIG. 7(2) are pre-message response signals. That is, the CFR (reception readiness confirmation) signal is a digital response signal that confirms that all pre-message procedures have been completed and that message sending can be started.

In contrast, the FTT (failure to train) signal is an optional digital response signal for removing all or part of the pre-message procedure and requesting retraining of the Group 3 modulation system.

When a TCP signal is received in this way, a CFR signal is sent if the channel can be used at the relevant speed, and an FTT signal is sent if the channel cannot be used (in other words, two times one (Only one judgment can be made.)

PIX shown in FIG. 8(1) is an image signal. That is,
A training signal is sent out immediately before the image signal is sent.

The EOP transmitted from the transmitting side is a procedure end signal. The MCF subsequently transmitted by the receiver is a message confirmation signal.

Referring again to FIGS. 8(1) to 8(3), this will be explained in more detail. In FIG. 8(1) to FIG. 8(3), the transmitter/receiver is 2400b/s, 4800b/s, 2
00b/59600b/c transmission speed.

In the procedure shown in Figure 8 (11), an attempt was made to transmit at 9500b/s, and since the receiver was able to correctly receive the TCP signal, it sent a CFR signal and transmitted at 9600b/s.
This is an example in which image transmission was performed. Receive TCP signal, C
The criteria for determining whether to send an FR signal or an FTT signal is left to each manufacturer. - For example, if the demodulated TCP signal is checked and "0" data is received continuously for more than 1.0 seconds, the
It is designed to send out FR signals and otherwise send out FTT signals.

FIGS. 8(2) and (3) show the procedure when the line condition is poor. As shown in FIG. 8 (2), first, 960
Attempts to transmit at 0b/s. However, since the receiver cannot correctly receive the TCP signal, it sends out the FTT signal. The transmitter then attempts to transmit at 7200 b/s. In this case as well, the receiver cannot correctly receive the TCP signal, so it sends out the FTT signal. The transmitter then attempts to transmit at 4800 b/s. However, since the receiver cannot correctly receive TCP signals, it sends out FTT signals.

The transmitter is T of 9600b/s or 7200b/s
When an FTT signal is received in response to a CP signal, the 7
It is pre-designed to migrate to TCP signals at 200b/s and 4800b/s. On the other hand, 480
For TCF signals of 0 b/s or 2400 b/s, it is designed in advance to send 8 lines to transmit a TCP signal at 2400 b/s or disconnect the line when an FTT signal is received twice. The reason for this is that at 4800 b/s or 2400 b/s, it is desirable to attempt transmission at that speed as much as possible.

The transmitter then continues to try again to transmit at 4800 b/s. However, since the receiver cannot correctly receive the TCP signal, it sends out the FTT signal. In this way, the transmitter responds to the TCP signal at 4800 b/s by
Since the TT signal has been received twice, the next attempt is to transmit at 2400 b/s. In response, the receiver was able to correctly receive the TCP signal, so it sent out a CFR signal and 240
Image transmission is performed at 0 b/s.

(Problem to be Solved by the Invention) In this way, in the above conventional example, in response to a line status check signal that checks whether or not transmission is coming at a specific speed, it is possible to transmit at the specific speed. Alternatively, there was a drawback that the decision could only be made between two options: ``Transmission at that particular speed is not possible.''

Specifically, as shown in Figure 8 (2), if the line condition is poor, 7200b/54800b/s will be sent in order starting from 9600b/s.
/s and falling back to 2400b/s, the major drawback was that it took a lot of time as a pre-procedure.

Furthermore, looking ahead to future facsimile machines, 1200
It is conceivable that transmission will be performed at high speeds such as 0 b/s, 14400 b/s, and 19200 b/s. For example, even though both the transmitter and receiver have the ability to transmit at a transmission speed of 19200b/s, if the connected line happens to be in poor condition and transmission can only be performed at a transmission speed of 2400b/s. Since the transmission speed is reduced by one step each time an FTT signal is received, approximately 42 seconds will have elapsed by the time the pre-procedure is completed (until the receiver transmits the CFlt signal). .

Therefore, in view of the above points, an object of the present invention is to provide an image communication system that can quickly determine the transmission speed.

[Means to solve the problem]

In order to achieve such an object, in the present invention, in an image communication method in which communication is performed at one of a plurality of transmission speeds, a line condition check signal for determining the transmission speed is transmitted in advance before transmitting image information, The receiving side determines the optimum transmission speed based on the reception state of the check signal, and notifies the transmitting side of the transmission speed.

(Function) According to the present invention, in an image communication system capable of communicating at a plurality of transmission speeds, a line condition check signal for determining the transmission speed is transmitted once before image transmission, and on the receiver side, Based on the reception result of the check signal, it becomes possible to determine the optimum transmission speed and notify the transmitter side of the transmission speed. Therefore, the transmitter side can immediately proceed to image transmission at the transmission speed notified from the receiver side.

As a result, for example, both the transmitter and receiver are 2400b/548
00b/s, 7200b/s, 9600b/s
If the receiver has a function to perform transmission at a transmission speed of The optimum transmission speed can be determined depending on the signal reception condition. This is, for example, 12000b/S or 14400b/S.

Even if the device has a function of transmitting at a transmission speed of 19200b/S, it is possible to deal with it in the same way.

In this way, even if you have the ability to transmit at multiple transmission speeds and the line condition is poor, you can proceed to image transmission at that transmission speed by transmitting only one line status check signal. As a result, the time required to determine the optimum transmission speed can be significantly reduced compared to the conventional method.

〔Example〕

FIG. 1 shows the overall configuration of an image communication system according to the present invention. As shown in this figure, in an image communication system that communicates at one of multiple transmission speeds, a line status check signal is sent in advance to determine the transmission speed before transmitting image information, and the receiving side The optimum transmission speed is determined based on the reception state of the check signal, and the transmitting side is notified of the transmission speed.

A concrete example of this is shown in FIG. In this figure, the transmitter and receiver are: 2400b/s, 4800b/57
It is assumed that it has a function of transmitting at transmission speeds of 200 b/s and 9600 b/s.

Initially, the training/TCF signal is transmitted using 9600b/S as shown in Figure 2, but the line condition is poor, so
The receiver transmits 5PD24, that is, a signal instructing transmission of an image signal at 2400 b/s. When compared with the procedure for fall-packing a conventional facsimile machine to 2400 b/s (see FIG. 8(2)), the superiority of this embodiment becomes clear.

In one embodiment of the present invention, which will be described in detail below, it is assumed that both the transmitter and receiver are G3 facsimile machines that comply with the CCITT recommendations V27ter and V2O transmission systems. Also, when receiving a line status check signal (specifically, a training/TCF signal), the instruction based on the reception result is V
27ter・2. Instructions to transmit images at a transmission speed of +00b/s, or V27ter/4800b
An instruction to perform image transmission at a transmission speed of /s, or an instruction to perform image transmission at a transmission speed of V2O/7200b/s, or an instruction to perform image transmission at a transmission speed of V299600b/s, as well as an instruction to transmit an image at a transmission speed of V299600b/s. There are instructions to discontinue. In addition, each of the above signals is CCI
The HDLC format specified in TT Recommendation T30 shall be used. In addition, signal names include line disconnection instructions,
2400b/s instruction, 4800b/s instruction,
7200b/s instruction 9600b/s (in order of D instructions: 5PDsTP, 5PD24, 5PD48.

Named 5PD72 and 5PD96. Kokote, (FC
It may be set on the F7 axis control fee day.

Of course, this signal is V21 modulated at 3oob/s.

Figure 3 is a block diagram showing an embodiment of a facsimile machine to which the present invention is applied.

In Figure 1, 2 uses the telephone network for data communication, etc., so it connects to the terminal of the line and controls the connection of the telephone exchange network, switches to the data communication path, and maintains the loop. Network control unit NCU (Network
Control Unit). The signal line 2a is a telephone line. The MC 112 inputs the signal on the signal line 30a, and if the signal level is "o", connects the telephone line to the telephone side, that is, connects the signal line 2a to the signal line 2b. Also, the signal on the signal line 30a is manually input, and the signal level is [1
'', connect the telephone line to the image communication method side, that is, connect the signal line 2a to the signal line 2c. Under normal conditions, the telephone line is connected to the telephone set.

4 is a telephone.

6 is a hybrid circuit that separates the transmission system signal and the reception system signal. That is, the transmission signal on the signal line 18a passes through the signal line 2c and is sent out to the telephone line via the NCu2. Further, a signal sent from the other party passes through the NCu 2, passes through the signal line 2c, and is output to the signal line 6a.

Reference numeral 8 denotes a reading circuit which sequentially reads image signals for one line in the main scanning direction from the transmitted original and creates a signal string representing binary values of white and black. This is composed of an image sensor such as a CCD (charge-coupled device) and an optical system.

The white/black binary signal string is output to the signal line 8a.

Reference numeral 10 denotes an encoding circuit, which inputs the data output to the signal line 8a and outputs the encoded data (MW (Modified Huffman) encoding or MR (Modified Read) encoding) to the signal line 10a. .

Reference numeral 12 denotes a TCF signal generation circuit that sends a TCP signal, that is, a 1.5 second "0" signal to the signal line 12a when a TCF signal sending pulse is generated on the signal line 30b.

14 is a modulator that performs modulation based on the well-known CCITT recommendation V27ter (differential phase modulation) or v29 (quadrature modulation). This modulator 14 inputs the signal on the signal line 30d and determines the transmission speed based on this signal. Specifically, the signal lines 30d are 'OJ,'IJ.

Compatible with '2J, r3', SotL Soh 2400
b/s.

4800b/S, 7200b/S, 9500b
/s. Further, the modulator 14 receives the signal on the signal line 30c manually, inputs the signal on the signal line 10a when the signal level is "0", and inputs the signal on the signal line 12a when the signal level is "1". Then, modulation is performed and the modulated data is output to the signal line 14a.

Reference numeral 16 denotes a modulator that performs modulation based on the well-known C(:ITT recommendation V21).The modulator 16 inputs the procedure signal on the signal line 30e, performs modulation, and outputs the modulated data to the signal line 16a.

18 is an adder circuit, which has a signal line 14a and a signal line 16a.
The signals are input manually and the added result is output to the signal line 18a.

20 is a demodulator that performs demodulation based on the known CCITT recommendation V21. The demodulator 20 manually performs V21 demodulation on the signal on the signal line 6a, and outputs demodulated data to the signal line 20a.

22 is a demodulator that performs demodulation based on the well-known CCITT recommendation V27ter (differential phase modulation) or V29 (quadrature modulation). The demodulator 22 inputs the signal on the signal line 6a, performs demodulation, and outputs the demodulated data to the signal line 22a. The demodulator 22 receives the signal from the signal line 30g and determines the transmission speed based on this signal. Specifically, signal line 3
0g is the signal rO'', rIJ, r7''.

Corresponding to "3", 2400b/s and 480b/s respectively
Set to 0b/57200b/s, 9600b/s.

24 is a decoding circuit that manually inputs the demodulated data outputted to the signal line 22a and outputs the decoded (Modified Huffman decoding or MR (Modified Read) decoding) data to the signal line 24a. .

26 is a recording circuit that manually records the decoded data output to the signal line 24a and sequentially records each line.

28 is a TCP signal determination circuit, and when a signal of signal level "r1" is output to the signal line 3Of, that is, the TC
When receiving the P signal, the demodulated data output to the signal line 22a is input, and the time of the actually received TCF signal is input to the signal line 22a.
At 8a, the maximum time during which "0" data has been continuously received is output to the signal line 28b.

30 is a control circuit that performs the following control.

First, the NSF determines whether the receiver has a function to determine the optimal transmission speed based on the reception result of the line status check signal (specifically, the TCP signal) and notify the transmitter of the transmission speed. Notify the transmitter side with a signal. This is, for example, a specific bit (for example, 50 bits) of the FIF (Facsimile Information Field) of the NSF signal.
This is done by assigning . In other words, if the 50th bit of PIF in the NSF signal is "0", the receiver determines the optimal transmission speed based on the reception result of the line status check signal, specifically the TCP signal, and sends the transmitter the transmission speed. It does not have the function to notify, and on the contrary, NSF
If the 50th bit of PIF in the signal is "1",
The receiver has a function of determining the optimum transmission speed based on the reception result of the line status check signal, specifically, the TCP signal, and notifying the transmitter of the transmission speed.

The transmitter then transmits the image signal at the optimal transmission speed specified by the receiver.

On the transmitter side, if the 50th bit of PIF in the NSF signal sent from the receiver on the other side is "1", the 50th bit of PIF in the NSS signal is "1".
Set.・In other words, the transmitter communicates with the receiver,
Declares that it operates with functionality according to the invention. On the other hand,
PIF in the NSF signal sent from the other party's receiver
If the 50th bit of the NSS signal is "0", the transmitter sets the 50th bit of the PIF of the NSS signal to "0".

That is, the transmitter declares to the receiver that it will not operate with the functionality according to the invention. In other words, conventional CGI
Facsimile communication is performed in accordance with TT Recommendation 730.

The following is an explanation of the operation when the transceiver has functions according to the present invention.

The transmitter transmits the training signal/TCF following the NSS/TSL/DC5 signal. Here, the TCF signal is
15 seconds of "OJ signal.

A receiver receives this training signal/TCF signal. The reception result of the TCF signal is sent to the TCP signal determination circuit 28.
The time of the actually received TCP signal and the maximum time of continuous reception of "O" data are recognized. Since the duration of a TCP signal is fixed at 1.5 seconds, the optimum transmission speed is determined here based on the maximum time during which "0" data is continuously received. In addition, T
If the time of the line status check signal corresponding to the CP signal changes, it is necessary to measure the time of the actually received TCF signal.

Below is an example of how to instruct transmission or disconnect the line based on the transmission speed at which the training/TCF signal is being received and the maximum continuous "0" signal time received at that time. explain.

First, the transmission speed of the training/TCF signal is 96
The case of 00b/s will be explained. In this case, if the maximum time that "0" data is continuously received on the receiver side is, for example, 1.0 seconds or more, 9600 b/s
If the transmission instruction is 0.8 seconds or more and less than 1.0 seconds, it is 7.
200b/s transmission instruction, 4800b/s transmission instruction if 0.6 seconds or more and less than 0.8 seconds, 2400b/s transmission instruction if 0.4 seconds or more and less than 0.6 seconds. If the time is less than 0.4 seconds, an instruction is given to the transmitter to disconnect the line.

Next, the transmission speed of the training/TCF signal is 72
The case of 00b/S will be explained. In this case, if the maximum time that the receiver side has continuously received "0" data is, for example, 1.4 seconds or more, the transmission instruction at 9600 b/s is transmitted for 1.0 seconds or more. 72 if less than seconds
00b/s transmission instruction, 4800b/s transmission instruction if 0.8 seconds or more and less than 1.0 seconds, 2400b/s transmission instruction if 0.6 seconds or more and less than 0.8 seconds. instructions,
If it is less than 0.6 seconds, an instruction to disconnect the line is given to the transmitter.

Next, the training/TCF signal transmission speed is 48
The case of 00b/s will be explained. In this case, if the maximum time that the receiver side has continuously received "0" data is, for example, 1.4 seconds or more, the transmission instruction at 7200 b/s is sent for 1.0 seconds or more and 1.4 seconds. 48 if less than
If the time is 0.8 seconds or more and less than 1.0, a transmission instruction is given to the transmitter at 2400 b/s, and if it is 0.8 seconds or more, a line disconnection instruction is given to the transmitter.

Next, the transmission speed of the training/TCF signal is 24
The case of 00b/s will be explained. In this case, if the maximum time during which "0" data is continuously received on the receiver side is, for example, 1.4 seconds or more, the transmission instruction at 4800 b/s is transmitted for 1.0 seconds or more and 1.4 seconds. If less than 24
If the transmission instruction is less than 1.0 b/s, an instruction to disconnect the line is given to the transmitter.

After transmitting the NSS/TSI/DC5 signal and the training/TCF signal, the transmitter transmits the 5P096 signal, i.e. 9
960 when receiving a transmission instruction signal at 600 b/s
Proceed to training/image signal transmission at 0b/s, 5P
When receiving the D72 signal, that is, the transmission instruction signal at 7200b/s, the training/training at 7200b/s is performed.
Proceed to transmit the image signal, and the signal of 5P048, that is, 48
4800 when receiving a transmission instruction signal at 00b/s
Proceed to b/s training/image signal transmission, 5PD
When it receives the 24 signal, that is, the transmission instruction signal at 2400 b/s, it proceeds to transmit the training/image signal at 2400 b/s, and when it receives the 5 PDSTP signal, that is, the line disconnection instruction signal, it starts the DCN (disconnection command) signal. and open the line.

Thereafter, a facsimile transmission procedure based on the conventional CGITT@notification T30 is performed.

FIGS. 4(1) to (3) show the control circuit 3 shown in FIG.
The control procedure that 0 should execute is shown.

First, step 540 represents the "beginning".

In step S42, a signal with a signal level "0" is output to the signal line 30a, and the CML (Connect Mo
demto Line) off.

In step S44, it is determined whether facsimile transmission has been selected. If facsimile transmission is selected, the process advances to step 34B. If facsimile transmission is not selected, the process advances to step 546.

In step 546, it is determined whether facsimile reception has been selected. If facsimile reception is selected, the process advances to step 59B. Further, if facsimile reception is not selected, the process advances to step 544.

In step 548, a signal of signal level "1" is output to the signal line 30a to turn on the CML.

In step 550, a pre-procedure is executed.

In step 552, the PIF
Is the 50th hit "1"? In other words, the other receiver determines the optimal transmission speed based on the reception result of the line status check signal, specifically the TCP signal, and notifies the transmitter of the transmission speed. It is determined whether the function is present or not. If the 50th bit of PIF in the NSF signal is "1", that is, it has the above function, the process advances to step 560. Further, if the 50th bit in the FIF of the NSF signal is "0", that is, if it does not have the above function, the process advances to step S54.

In step S54, a pre-procedure is executed. Here, NSS
When transmitting a signal, the 50th bit of PIF in the NSS signal is set to "0".

In step 556, image transmission is performed.

Step 558 performs post-procedures.

From step S54 to step 558, the conventional CCI
Facsimile communication is performed using a protocol in accordance with TTliil notification T30.

In step 560, NSS/TSI/DC5
Transmits signals. Here, FIF in NSS signal
The 50th bit of is set to "1".

In step 562, a training/TCF signal is transmitted to check the line status.

In steps S64 to S572, a determination is made as to the result of receiving the signal from the receiver. 5 from receiver
When the PD96, that is, the 9600 b/s training/image signal transmission instruction signal is received, the signal line 3
Outputs signal "3" to 0d and connects high-speed modem 14 to 9600
b/s (step 584).

Also, from the receiver 5PD72, i.e. 7200b/
When the training/image signal transmission instruction signal at s is received, the signal "2" is output to the signal line 30d, and the high-speed modem 14 is set to 7200 b/s (step 578).
).

Also, from the receiver 5PD48, i.e. 4800b/
When the training/image signal transmission instruction signal in S is received, a signal "1" is output to the signal line 30d, and the high-speed modem 14 is set to 4800 b/s (step 580
).

Also, from the receiver 5PD24, i.e. 2400b/
When receiving the training/image signal transmission instruction signal at s, outputs a signal "0" to the signal line 30d and sets the high-speed modem 14 to 2400 b/s (step 582
).

Furthermore, when receiving 5PDSTP, that is, a transition instruction signal to line disconnection, from the receiver, the DCN signal (step 5
75), the line is released.

In step S74, the NSS/TSI/DC5 signal.

It is determined whether or not there is no response even after three attempts to transmit the training/image signal signal. If there is no response three times in a row, a DCN signal is sent (step 576) and the line is released. If there is no response three times in a row, the process advances to step 560.

In step 586, training/image signals are transmitted.

In step 588, it is determined whether there is a next document. If there is a next manuscript, proceed to step 592;
If there is no next document, the process advances to step 590.

In step S90, a post-procedure is executed.

In step S92, it is determined whether there is a mode change. If there is a mode change, the process advances to step 560. If there is no mote change, the process advances to step S94.

In step 594, it is determined whether there is a request to transmit a TCP signal from the receiver, specifically, whether or not, for example, an RTP (retrain positive) signal or RTN (retrain negative) signal has been received. If there is a request to transmit a TCP signal from the receiver, the process proceeds to step 550.

If there is no request from the receiver to transmit a TCP signal, the process proceeds to step 586.

In step 596, a signal of signal level "1" is output to the signal line 30a to turn on the CML.

In step 59B, a pre-procedure is executed. Here, it has the function of determining the optimal transmission speed based on the reception result of the line status check signal, specifically the TCP signal, and notifying the transmitter of the transmission speed. The th bit is set to "1".

In step 5100, the FI in the NSS signal is
It is determined whether the 50th hit of F is "1", that is, whether the transmitter has the function according to the present invention. The 50th bit of PIF in the NS5 signal is “1”
That is, if the transmitter has the functionality according to the present invention, the process proceeds to step 5108. If the 50th bit of PIF in the NSS signal is "0", that is, the transmitter does not have the function according to the present invention, step 5
Proceed to step 102.

In step 5102, a pre-procedure is executed.

In step 5104, an image signal is received.

In step 5106, a post-procedure is executed.

In steps 5102 to 5106, facsimile communication is performed using a protocol based on the conventional CCITT Recommendation T30, rather than based on the functions according to the present invention.

In step 5108, a TCP signal is received.

After receiving the TCP signal, the signal on the signal line 28b is input, and the maximum time for consecutively receiving "0" data is recognized.

In step 5ilo, the transmission speed is 9500
It is determined whether or not it is b/S. Transmission speed is 96
When it is 00b/S, the process advances to step 511 and 9600b
/s, the process advances to step 5150.

In steps 5112 to 5118, the maximum time of continuous "0" is checked. When this time is 1 second or more, 5PD96 is transmitted and 960 is sent to the transmitter.
In order to instruct transmission of a 0b/s training/image signal (step 5120), the receiver sends a signal "3" to the signal line 30g.
is output, and the high-speed modem 22 is set to 9600 b/s (step 5122).

When this time is 0°8 seconds or more and less than 10 seconds, 5PD72
and instructs the transmitter to transmit a 7200b/s training/image signal (step 5124), and the receiver outputs a signal "2" to the signal line 30g, causing the high-speed modem 22 to transmit a 7200b/s training/image signal.
200 b/s (step 512B).

If this time is 0.6 seconds or more and less than 0.8 seconds, 5PD4
8 to instruct the transmitter to transmit a training image signal of 4800 b/s (Step 5128), the receiver outputs a signal "1" to the signal line 30g and sets the high-speed modem 22 to 4800 b/s. (Step 5130).

If this time is 0.4 seconds or more and less than 0.6 seconds, 5PD24
and instructs the transmitter to transmit a 2400 b/s training/image signal (step 5132), and the receiver outputs a signal "0" to the signal line 30g and connects the high-speed modem 22 to 2.
400 b/s (step 5134).

When this time is less than 0.4 seconds, 5PDSTP is transmitted to instruct the transmitter to open the line.

In step 5138, training/image signals are received.

In step 5140, it is determined whether there is a next document. If there is a next document, the process advances to step 5144. If there is no next document, the process advances to step 5142.

In step 5142, a post-procedure is executed.

In step 5144, it is determined whether there is a load change. If there is a mode change, the process advances to step 5148; if there is no mode change, the process advances to step 51116.

In step 5148, the receiver performs training/
A determination is made as to whether the TCF is desired to be received again.

When the receiver wants to receive the training/TCF signal again, it transmits the request signal and then proceeds to step 51118. If the receiver does not want to receive training/TCF again, it sends a signal to that effect and then proceeds to step 5138.

In step 5148, intermediate procedures are performed.

In step 5150, the transmission speed is 7200.
It is determined whether or not the speed is b/s. Transmission speed is 72
00b/s, the process advances to step 5152 and 7200
If it is not b/s, the process advances to step 3160.

In steps 5152 to 5158, the maximum time of continuous "0" is checked. If this time is 1.4 seconds or more, the process advances to step 5120, and step 960
Set the high speed modem 22 to 0b/s. Further, if this time is 10 seconds or more and less than 1.4 seconds, step 5124
Go to and set the high-speed modem 22 to 7200b/s. If this time is greater than or equal to 08 seconds and less than 1.0 seconds, the process proceeds to step 5128, where the high-speed modem 22 is set to <aoob,'s. Further, if this time is 06 seconds or more and less than 08 seconds, the process advances to step 5132, and the 2400b/S
Set the high-speed modem 22 to . Also, this time 06
If it is less than a second, the process advances to step 5136 and the line is disconnected.

In step 5160, the transmission speed is 4800.
It is determined whether or not the speed is b/s. Transmission speed is 48
When it is 00b/s, the process advances to step 5162 and 2400b/s.
If b/s, the process advances to step 5168.

In steps 5162 to 5166, the maximum time of continuous "0" is checked. If this time is 14 seconds or more, the process advances to step 5124 and step 7200
Set the high speed modem 22 to b/s. If this time is greater than or equal to 1 second and less than 1.4 seconds, the process advances to step 5128;
Set the high speed modem 22 to 800b/S. If this time is 0.8 seconds or more and less than 1.0 seconds, step 513
Proceed to step 2 and set the high speed modem 22 to 2400 b/s. Also, if this time is less than 08 seconds, step 51
Proceed to step 36 and disconnect the line.

In steps 5168 to 5170, the maximum time of continuous "0" is checked. If this time is 1.4 seconds or more, the process advances to step 5128, and 48θ
Set the high speed modem 22 to Ob/s. This time is 1
．． When the time is 0 seconds or more and less than 1.4 seconds, the process advances to step 5132, and the high-speed modem 22 is set to 2400b/S. If this time is less than 1.0, the process advances to step 5136 and the line is disconnected.

In the above embodiment, the image transmission speed is determined based on the maximum time of consecutive "0"s while receiving a TCP signal. This transmission speed may be determined by other methods, such as considering the total "0" time.

In the above embodiment, the transmission speed is 2400 b/s.
, 4800b/s , 7200b/s , 960
0b/s (i.e. CCITT Recommendation V27ter
, V29).

However, in addition to 12000 b/s and 14400 b/s, which are provisional recommendations in CCITT Recommendation V33, the present invention may also be applied to transmission speeds of 19200 b/s, which are expected to be recommended in the future.

Currently (7) CCITT Recommendation T30, 12
000b/s, 14400b/s, +9200b
The transmission speed bit in /s is not assigned to the Dis (Digital Identification) /DTC (Digital Transmit Command) 7'ocs (Digital Command) signal, so it is not assigned to the Dis (Digital Identification) /DTC (Digital Transmit Command) 7'ocs (Digital Command) signal, so it is non-standard equipment)
It is necessary to make bit assignments for the /NSC (non-standard device command) /NSS (non-standard device setting) signal.

Direction ■1 In the embodiment described above, negotiation as to whether or not the function according to the present invention is included is performed by assigning bits to the signal representing the non-standard function, specifically, the NSF/NSC/NSS signal. Ta. However, this function
If recommended at the TT meeting, Dis/DTC
Of course, bit assignment may be made to the /DC5 signal.

In the above embodiment, after receiving the line status check signal, the transmission speed instruction is sent to the demodulated TCP.
It received a signal and made a decision based on the data. That is,
The judgment was made based on the data of "0" and "1" as a result of the modem demodulating the data. However, without following this determination procedure, for example, the magnitude of the error signal may be checked on the modem side, and the above instruction may be determined based on this magnitude.

An example of the operation when the modem makes a decision will be described below.

FIG. 5 shows a P with a squared error accumulator for implementing the present invention.
An example of the LL automatic equalization amount is shown.

FIG. 6 shows a detailed configuration of the equalization amount 300 shown in FIG.

Figure 7 shows the 10 filters (Integr) shown in Figure 5.
313 shows the detailed configuration of the Dump Filter (at and Dump Filter) 313.

In FIG. 5, Ri is a demodulated complex signal, which is supplied from the demodulator of the receiving system. 300 is a line equalization amount, which normalizes data that has been distorted on the line to its original transmission state. Yi=Aieje' represents the i-th output of the equalization amount 300 in polar coordinates.

303 is a multiplier, and the output e- of the complex number generator 305 is
Jθ1 and the equalization amount output Yi=AieJe' are multiplied together and outputted as Zi=Yie-je'=Aie"θl-?ll.

A determiner 310 determines the code point closest to the received signal point, which is the output of the multiplier 303.

A subtracter 311 subtracts the decision point from the received signal point and outputs an error signal Ei=Zi-At.

Subsequently, the error signal Ei is output from the complex number generator 302, φ
1 output e and the multiplication are combined to obtain Eie'φ1, which is fed back to the equalization amount 300. Here eJ'/'1
is the phase correction amount.

On the other hand, the output Ei = Zi - Ai of the subtracter 311 is 2 in absolute value.
1 through the multiplication circuit 312. Proceed to D, F, 313. That is, the squaring circuit 312 calculates the square of the distance between the received signal point and the determination point.

Continuing on from 1. At D, F, and 313, the output of the square circuit 312 is accumulated a number of times (N baud periods) set by the designer and output as QL. This Qt approaches zero if the line equalization rate is good and the amount of line noise is small; conversely, if the line equalization rate is poor and the amount of line noise is large, the value of Qt increases.

Next, the operation of the phase control section surrounded by dotted lines in FIG. 5 will be explained. 309 is a divider, and as a result of dividing zi and the layer, eJfel-ψth is approximately found.

308 is an imaginary part extractor, which outputs 5in(θi−φi). sin (θi−φl) is when θiαφ1,
Approximately equal to θi−φi. Reference numerals 306 and 307 denote a vCO and a low-pass filter, which are components of a normal PLL, and output a phase value -φi to cancel an input phase error. Subsequently, a complex number generator 305 and. 2. Complex conjugate generator,. 4, Yo, e-・φ・e
+Jul is outputted and becomes the manual power of multipliers 303 and 301, respectively, canceling out the phase error of the entire system.

FIG. 6 shows a block diagram of the equalization amount. Generally, the equalization amount is a transversal filter, 400 is a delay element that delays the old received data for a certain period of time, and 401 is a tap gain [C□~cNl] multiplied by the delayed received data immediately above. Further, 403 is an adder that takes the sum of the multiplication results of the delayed reception data and the tap gain, and as a result, the equalizer output signal Y1 becomes the following equation.

Yi=Σ c,, R, -j l=-s ------(1) The equalization amount is based on the received data, and each tap gain is set to M.
By sequentially calculating the following equation using the SE (Mean 5-square Error) method, it adapts to the reverse characteristics of the line.

IJJ! "=C1'-aR+-L"Eie""
----(2) Equation Cz"': Tap gain value Eiejφ1 calculated for the 11th time = feedback signal α from the multiplier 301 in FIG. 5: Convergence coefficient (generally α<<1) FIG. , 500 is an adder, 501 is a delay device, 5
02 is a sampler.

First, the output of the absolute value squaring circuit 312 in FIG. 5 is added to the output of the delay device 501 in the adder 500. This operation is repeated every output period of the squaring circuit 312, that is, every baud period. The sampler 502 samples the output of the adder for each value N determined by the designer, and subsequently initializes the value of the delay device 501. That is, in this circuit, N outputs of the squaring circuit 312 are cumulatively added.

Finally, the PLL with squared error accumulator that has been explained so far
Three methods of determining the equalization rate based on the automatic equalization amount and determining the transmission rate based on the determination result will be described below.

(1) How to carry out during training CCTTT Recommendation V27ter segment 5 (continuous ° ° 1
scrambled signal 8S1) as well as V29 segment 4 (scrambled data 8S1)
I), and the cumulative number N in FIG. 7 is set to 8.48. Here, we will take the case of using V29 as an example.

First, an error rate vs. SN ratio curve of the V29 modem is drawn to determine the SN ratio with respect to the user's allowable error rate. requested S
The squared error cumulative value QL for the N ratio is determined by simulation. This value is T. shall be. In actual facsimile communication, if the value of QL is smaller than T, 9600 b/s is selected as the transmission rate, and if it is larger than TH, 7200 b/s is selected as the transmission rate. Therefore,
Using the above method, the transmission rate can be determined with one training session.

Also, if you calculate the value when the equalization amount diverges by simulation and set that value as Tdlv, it is also possible to save the tap coefficient of the equalization amount and use it for training when the QL value is larger than Tdlv. It is.

The above method is also applicable to V27ter,
Furthermore, although there are many transmission speeds for ultra-high-speed modems such as 14400 b/s and 19200 b/s, by using this method, the optimum transmission speed can be determined in principle with one training session.

(2) Method using TCF In facsimile communication, scrambled °0'' is sent as a TCP signal, but it is also possible to obtain the squared error cumulative value QL during this period. In this case, the above-mentioned (1)
Since the number of times of accumulation can be longer than that of the above method, the equalization rate can be determined more accurately. When using this method as well, the threshold value T is determined by simulation in the same way as method (1).

〔Effect of the invention〕

As explained above, according to the present invention, when transmission is performed between devices having the function of transmitting at multiple transmission speeds, the optimum transmission speed is determined by transmitting a line status check signal only once. It becomes possible to do so. As a result, the time required to determine the optimum transmission speed can be significantly reduced compared to the conventional method.

In particular, transmission speeds will increase significantly in the future (for example, G3 facsimile transmission speeds will increase from the current 4 types to 7 types).
Although it is expected that the number will increase, an even greater effect will be obtained in this case as well.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the entire image communication system according to the present invention, FIG. 2 is a diagram showing the specific procedure in FIG. 1, and FIG. 3 is a block diagram showing an embodiment of a facsimile device to which the present invention is applied. 4(1) to 4(3) are flowcharts showing the control procedure to be executed by the control circuit 30 shown in FIG. 3, and FIG. FIG. 6 is a diagram showing the configuration of the equalization amount 300 shown in FIG. 5; FIG. 7 is a diagram showing the configuration of the ID filter 313 shown in FIG. 5; FIG. ) to FIG. 8(3) are diagrams showing an example of the procedure of a conventionally known facsimile machine.
CP signal generation circuit, 14-...V27ter or V2916...V2
1 modulator, 20...V21 demodulator, 22...V27ter or V29300...equalization amount, 313...ID filter. modulator, demodulator,

Claims (1)

[Claims] 1) In an image communication system that performs communication at one of a plurality of transmission speeds, a line condition check signal is transmitted in advance to determine the transmission speed prior to transmitting image information, and the receiving side An image communication method characterized by determining an optimal transmission speed based on the reception state of the check signal and notifying the transmitting side of the transmission speed.