JPH0292153A - Picture communicating system - Google Patents

Abstract

PURPOSE:To shorten the time to determine an optimum transmission speed by instructing a transmitting side to fall up or fall back the transmission speed based on the receiving condition of the checking signal at a receiving side. CONSTITUTION:A line condition checking signal to determine the transmission speed prior to the picture transmission is transmitted beforehand, and based on the receiving condition of a checking signal at a receiver, the instruction is executed so as to fall up or fall back the transmission speed, from a receiving side to a transmitting side at one or plural steps. Consequently, even when the function to transmit at plural transmission speeds is held and even when the line condition is bad, the falling-back (or falling-up) can be executed rapidly to a suitable transmission speed. Thus, the time to determine the optimum transmission speed is shortened.

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-74 recommendation.

In this type of facsimile machine, prior to high-speed image transmission, the amount of automatic equalization on the receiver side is adjusted using a training signal and a training check signal to suit the line characteristics, and the adjustment result 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 63-image communication method will be explained with reference to FIGS. 8(1) to 8(3).

FIGS. 8(1) to 8(3) show 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, C3l (called station identification) signal, DISC 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 DO3 (digital command) signal are reception command signals and specify the mode in which transmission will be performed. Then, if a TCF (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 the 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 15 seconds.

Training No. 13, which is sent just before the TCP signal, is
This is a synchronization signal to properly adjust the receiving modem. This synchronization signal is used for carrier detection and, if necessary, for AGC, timing synchronization 9, convergence of equalization amount, and descrambler synchronization.

The CFR (reception readiness confirmation) signal and the FTT (1-lane 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 (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 and receiver are both 2400b/s, 4800b/s, 2
00b/s.

It is assumed that the device has a function of transmitting at a transmission speed of 9600b/C.

In the procedure shown in Figure 8 (1), an attempt was made to transmit at 9600b/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, check the demodulated TCP signal, and if "o" 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 Figure 8 (2), first, 98
Attempt to transmit at 00b/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
2 [10 b/s, <aoob/s. On the other hand, 48
For TCP signals of 00b/s or 2400b/s, when FTT signals are received twice, 2400b/s
It is designed in advance to transmit TCP signals or disconnect the line. 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 TCF 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 transmission is possible at a specific speed, it is said that ``Transmission is possible at that specific speed'' or ``°Transmission at that specific speed is possible.'' The drawback was that it was only possible to make an alternative decision.

Specifically, as shown in FIG. 8 (2), when the line condition is poor, the speed is increased from 9600b/s to 7200b/s.

4800b/s, 2400b/s hair t-le back and back tie had a major drawback in that it required 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 elapse by the time the pre-procedure is completed (until the receiver transmits the CFR 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, the present invention transmits in advance a line condition check signal to determine the transmission speed before transmitting image information in an image communication system that performs communication at one of a plurality of transmission speeds. Based on the receiving state of the check signal on the receiving side, the receiving side instructs the transmitting side to fall up or fall back the transmission speed in one or more stages.

[For production]

According to the present invention, in an image communication system capable of communicating at a plurality of transmission speeds, a line status check signal for determining the transmission speed is transmitted in advance prior to image transmission, and the reception status of the check signal at the receiver is checked. Based on this, it becomes possible for the receiving side to instruct the transmitting side to fall up or fall back the transmission speed in one or more stages.

With this, for example, both the transmitter and receiver can achieve 2400 b/s.

4800 b/s, 7200 b/s, 9600
If the device has a function to perform transmission at a transmission speed of 9600 b/s, it first transmits a line status check signal at a transmission speed of 9600 b/s, and depending on how well the receiver receives this line status check signal, Instructing that the image signal may be transmitted at that transmission speed (9600 b/s), ■ Decreasing the transmission speed by one step (specifically, 7
(at a transmission speed of 200 b/s), and then try again to transmit the line status check signal; ■ Decrease the transmission speed by two steps (specifically, at 4800 b/s).
(at a transmission speed of 2400 b/s), and then try again to transmit the line status check signal.■ Decrease the transmission speed by three steps (specifically, at a transmission speed of 2400 b/s) and try again to transmit the line status check signal. Instructions to try transmission, ■ Lower the transmission speed by 4 steps (specifically,
It is now possible to give an instruction to the sending side (line disconnection).

This is +2000 b/s, 14400 b/s
, 19200 b/s can be considered in the same way.

In this way, even if you have the ability to transmit at multiple transmission speeds and the line conditions are bad, you can quickly fall back (or fall up) to the appropriate transmission speed. Therefore, the time required to determine the optimal transmission speed is 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 a plurality of transmission speeds, A line condition check signal for determining the transmission speed is transmitted in advance, and the receiving side is instructed to fall up or fall back the transmission speed in one or more stages based on the receiving condition of the check signal on the receiving side. Give instructions to the sender.

A concrete example of this is shown in FIG. In this figure, both the transmitter and receiver are 2400b/s and 4800b/s.

It is assumed that it has a function of transmitting at transmission speeds of 7200 b/s and 9600 b/s.

Initially, the training/TCF signal is transmitted at 9600b/s as shown in Figure 2, but due to poor line conditions,
A three-step fallback instruction signal is sent. After that, the signal with 3-step fallback, i.e. 2400
A b/s training/TCF signal is transmitted and image communication is started. This is because the conventional facsimile machine has two
When compared with FIG. 8 (2) which falls back to 400 b/s, 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 transmission and reception are G3 facsimile machines based on the CCITT Recommendation V27ter and V29 transmission systems. Then, based on the reception result when the line status check signal (specifically, the TCP signal) is received, ■ an instruction that image transmission is possible at the transmission speed of the line status check signal;
An instruction to perform fallback by one or more stages shall be given. When a line status check signal (specifically, a TCP signal) is received here, the signal indicating that image transmission is possible at that transmission speed has the same meaning as the conventional CFR (reception readiness confirmation) signal. However, it is named CFRO. The signal instructing the n-stage fallback is named FTT n (n is a positive integer). For example, a signal indicating a two-step fallback is FTT 2.

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

In Figure 3, 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. The network controller NCII (Network
k Control 1lnit). Signal line 2a
is a telephone line. The NCL 12 inputs the signal on the signal line 30a, and if the signal level is "0", connects the telephone line to the telephone side, that is, the signal line 2a to the signal line 2b. Further, a signal on the signal line 30a is input, and if the signal level is "1", the telephone line is connected to the image communication method side, that is, the signal line 2a is connected to the signal line 2C. Under normal conditions, the telephone line is connected to the telephone side.

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 NCU 2. 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.

10 is an encoding circuit which inputs the data output to the signal line 8a and performs encoding (Ml+ (Modified Huffman) encoding or MR (Modified Read)
The encoded data is output 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 line 30d is rQ'', rl.

Corresponding to "2" and "3", respectively 2400b/54
800b/s, 7200b/s, 9600b/
Set to s. Further, the modulator 14 inputs the signal on the signal line 30c, when the signal level is "0", it inputs the signal on the signal line 10a, and when the signal level is "1", it inputs the signal on the signal line 12a. Then, modulation is performed and the modulated data is output to the signal line 14a.

16 is a modulator that performs modulation based on the known CI:ITT recommendation V21. The modulator 16 inputs the procedure signal on the signal line 30e, performs modulation, and outputs the modulated data on the signal line 16a.

18 is an adder circuit, signal line 14a, signal) J9+
The signal 6a is 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 inputs the signal on the signal line 6a, performs V21 demodulation, 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 inputs the signal on the signal line 30g and determines the transmission speed based on this signal. Specifically, signal line 3
0g corresponds to the signals "0", "1", "2" and "3",
2400b/s, 4800b/s, 7 respectively
Set to 200b/s and 9600b/s.

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

26 is a recording circuit which inputs the decoded data outputted to the signal line 24a and sequentially records each line.

28 is a TCP signal determination circuit, and when a signal of signal level "1" is output to the signal line 3Of, that is, TC
When receiving the P signal, the demodulated data output to the signal line 22a is input manually, and the time of the actually received TCF signal is input to the signal line 2.
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, on the receiver side, °゛ line status check signal (
Specifically, based on the reception result of the TCP signal, the transmitter side is informed whether or not it has a function that can instruct the transmission speed to fall back in multiple stages. ) PIF in the signal
This is done by assigning a specific bit (for example, the 50th bit) of the (facsimile information field). NSF
If the 50th bit of PIF in the signal is “0”,
The receiver does not have a function that can instruct the transmission speed to fall back in multiple stages based on the reception result of the line status check signal, specifically the TCP signal.
If the 50th bit of PIF in the SF signal is “1”, the receiver receives a line status check signal, specifically TCP
This means that it has a function that can instruct the transmission speed to fall back in multiple stages depending on the signal reception result.

On the transmitter side, if the 50th hit of the FIF in the NSF signal of the other party's receiver is "1", the NSS
(Non-standard device setting) The 50th bit of the PIF of the signal is “1”.
”. That is, the transmitter declares to the receiver that it operates with the functionality according to the invention. On the other hand, if the 50th bit of FI'F in the NSF signal of the other party's receiver is "0", the transmitter
Set "0" to the bit. That is, the transmitter instructs the receiver not to operate with the functionality according to the invention. As a result, facsimile communication is performed in accordance with the conventional CCITT recommendation T30.

The following description is a description of the operation when both the transceiver and the transceiver have functions according to the present invention.

The transmitter is NSS (non-standard equipment setting) /TSI (
Following the /DC5 (digital command signal) signal, the training signal and TcF signal are transmitted. Here, the TCP signal is a "0" signal that continues for 15 seconds.

The receiver receives this training signal, the TCP signal. The reception result of the TCF signal is sent to the TCP signal determination circuit 28.
The time of the actually received TCF signal and the maximum time of continuous reception of "0" data are recognized. The TCP signal time is fixed at 15 seconds, so depending on the maximum time that "0" data is received consecutively, we will either: ■ Perform image transmission at that speed, or ■ Instruct multi-stage fallback. Decide whether to do so. Note that if the time of the line status check signal corresponding to the TCP signal changes, it is necessary to measure the time of the actually received TCP signal.

If the maximum time for continuously receiving "0" data is, for example, 1.0 seconds or more, the receiver instructs the transmitter to perform image transmission at that speed. Zunawachi, CF
Send RO signal. Also, if the time when "0" data is continuously received is 0.8 seconds or more but less than 1.0 seconds, try transmitting the training/TCF signal by falling back one step from the current speed. A signal instructing the transmitter to perform the FTT 1 signal is transmitted. Also, the time when "0" data is continuously received is 0.6
If the time is greater than or equal to 0.8 seconds, the transmitter transmits a signal instructing the transmitter to fallback by two steps from the current speed and transmit the training/TCF signal, that is, an FTT 2 signal. In addition, continuously
A signal that instructs the transmitter to try transmitting the training/TCF signal with a three-step fallback from the current speed if the time it received the "O" data was less than 0.6 seconds, i.e. Send FTT 3 signal.

When the transmitter receives a CFRO signal, it proceeds to train/transmit images at that speed. Also, the transmitter is F
When a TT 1 signal is received, the speed will be reduced by 1 from the current speed.
NSS/TSI declared staged fallback
The /DC5 signal and the training /TCF signal with one-step fallback are transmitted. Also, the transmitter is FT
When the T2 signal is received, the NSS/TSI/
A DC5 signal and a two-step fallback training/TCF signal are transmitted. Furthermore, the transmitter is FT
When the T3 signal is received, the NSS/TSI/
Transmit the DCS signal and the training/TCF signal with three-stage fallback. Here, the transmitter transmits a DCN (line disconnection) signal when fallback of the specified number of stages is not possible.

The subsequent steps are based on the conventional CCITT recommendation T30.
A facsimile transmission takes place.

4(1) and (2) show the control procedure to be executed by the control circuit 30 shown in FIG. 3. FIG.

First, step S40 represents the "beginning".

In step 542, the signal level "
CML (Connect Mod
em t.

Turn off Line).

In step S44, it is determined whether facsimile transmission has been selected. If facsimile transmission is selected, the process proceeds to step 548. If facsimile transmission is not selected, the process advances to step 546.

In step 54B, it is determined whether facsimile reception has been selected. If facsimile reception is selected, the process advances to step 588. If facsimile reception is not selected, the process advances to step 544.

In step 548, the signal level "
1" signal and turn on CML.

In step S50, a pre-procedure is executed.

In step S52, the PIF in the NSF signal is
Is the 50th bit of ``1''? That is, ``The receiver at the other end can be instructed to fallback the transmission speed in multiple stages based on the reception result of the line status check signal (specifically, the TCF fB signal). It is determined whether it has the function or not. If the 50th bit of PIF in the NSF signal is "1", that is, if it has the above function, the process proceeds to step 560. Further, if the 50th bit of PIF in the NSF signal is "0", that is, if it does not have the above function, step 5E14
Proceed to.

In step 554, a pre-procedure is performed. Kokote 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.

In step 558, post-procedures are performed.

In steps S54 to 558, the conventional CCITT Recommendation T3 is used without performing the functions according to the present invention.
Facsimile communication is performed using a protocol that follows 0.

In step SBO, DC5 (digital command) is set to the highest speed that the receiver and transmitter have.

Further, a signal specifying the speed is outputted to the signal line 30d, and the transmission speed of the high-speed modem is set to the maximum speed.

In step 562, the NSS/TSI/DC5 signal is transmitted. Here, the 50th bit of PIF in the NSS signal is set to "1".

In step Se4, a training TCP signal is transmitted to check the line status.

In step 566, it is determined whether a CFRO has been received. When the CFRO is received, the process proceeds to step 568, and the training/image signal is transmitted at the same speed as the training/image signal.

If no CFRO has been received, proceed to step 578.

In step 570, it is determined whether there is a next document. If there is a next original, the process advances to step S74, and if there is no next original, the process advances to step S72.

In step S72, a post-procedure is executed.

In step S74, it is determined whether there is a mode change. If there is a mode change, the process advances to step S62. If there is no mode change, the process advances to step 576.

In step S76, 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. From the receiver, TCP
If there is a request to send a signal, the process advances to step 582. If there is no request to send a TCP signal from the receiver,
Proceed to step 568.

In step S78, it is determined whether FTTn (n is 1, 2, or 3 degrees in this embodiment; n is not limited to this number) is received. F
If TT n is received, the process proceeds to step 580. Further, if FTT n has not been received, step 58
Proceed to step 4.

In step 580, from the current transmission speed,
It is determined whether an n-step fallback is possible. If possible, the process advances to step S82; if not, the process advances to step 586.

In step 582, n is calculated from the current transmission speed.
Set the DC5 (digital command) signal for the speed with stage fallback. Further, a signal specifying this speed is output to the signal line 3Qd, and the transmission speed of the high-speed modem is set to a speed that is n-step fallback from the current transmission speed.

In step S84, the NSS/TSI/DC5 signal.

It is determined whether or not there is no response even after three attempts to transmit the training/TCF signal. If there is no response three times in a row, a DCN (disconnection command) signal is sent (step 586) and the line is released. If there is no response three times in a row, the process advances to step 562.

In step 588, the signal level "
1" signal and turn on CML.

In step 590, a pre-procedure is performed. Here, since it has a function that can instruct fallback of the transmission speed in multiple stages based on the reception result of the line status check signal (specifically, TCP signal), the 50th bit of PIF in the NSF signal is set to "1".

In step 592, the PI 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 NSS signal is “1”
, that is, if the transmitter has the functionality according to the present invention, the process proceeds to step 5100.

If the 50th bit of PIF in the NSS signal is "0", that is, if the transmitter does not have the function according to the present invention, the process advances to step S94.

In step S94, a pre-procedure is executed.

In step 596, the image signal is received.

In step 598, post-procedures are performed.

Steps 594 to 598 are similar to conventional CCITT Recommendation T30 without performing the functions according to the present invention.
Facsimile communication is performed using a protocol that follows.

In step 5100, a TcF signal is received.

After receiving the TCP signal, manually input the signal on the signal line 28b, recognize the maximum time that "0" data has been received continuously,
This time is checked in steps 5102 and 5104S106, and the next transmission mode is determined based on the result. This is the most important feature of the embodiments of the present invention. That is, even when line conditions are poor, it is possible to fall back to an appropriate transmission speed in a short time.

In steps 5102, 5104, and 5106, the maximum time during which [0] data is continuously received is determined, and based on the results, ■ If the time is 1 second or more, step 5
Proceed to step 116 to receive the image signal at that transmission speed, and if it is longer than 0.8 seconds but less than 10 seconds, proceed to step 5108.
Proceed to receive the TCP signal with one-step fallback, and if the time is greater than or equal to 0.6 seconds and less than 0.8 seconds, proceed to step 5.
Proceed to step 112 and proceed to receive the TCF signal with two-step fallback, ■If it is less than 0.6 seconds, proceed to step 5114
The process proceeds to 3-step fallback and proceeds to receive the TCP signal.

In step 5108, the training/TCF signal with one-step fallback is sent to the transmitter as NSS/TS.
FTT to instruct transmission following I/DC5 signal
1 signal is sent.

In step 5110, a pre-procedure is executed.

In step 5112, the training/TCF signal with two-step fallback is sent to the transmitter as NSS/TS.
FT-2 instructs to transmit following I/DC5 signal
Send a signal.

In step 5114, the training 7tcF<s signal with three-step fallback to the transmitter is sent to the NSS/TS.
FTT to instruct transmission following I/DC5 signal
Send 3 signals.

In step 5116, a CFRO signal is sent to the transmitter instructing it to shift to image transmission at that speed.

In step 5118, the image signal is received.

In step 5120, it is determined whether there is a next page. Step 5124 if there is a next page
If there is no next page, the process advances to step 5122.

In step 5122, a post-procedure is executed.

In step 5124, it is determined whether there is a mote change. If there is a mote change, the process advances to step 5128. If there is no mode change, the process advances to step 5126.

In step 5125, the receiver performs training/
It is determined whether the TCF signal is desired to be received again. When the receiver wants to receive the training/TCF signal again,
After transmitting the request signal, the process proceeds to step 5128. If the receiver does not want to receive the training/TCF signal again, it sends a signal to that effect and then proceeds to step 5118.

In step 5128, intermediate procedures are performed.

Although the above embodiments only described fallback in multiple stages, it is possible to transmit the line status check signal at a higher transmission speed than the currently transmitted line status check signal (specifically, TCP signal). If the transmitter/receiver has a function to perform
When the reception status of the CP signal is very good, an arbitrary multiple-step fallup may be instructed depending on the degree of reception.

For example, if the receiver sends an RTN signal or RTP signal, or if the transmitter sends an EOM (end of message) signal, a line status check signal (specific It can be considered to be used when transmitting TCP signals).

When a line status check signal (specifically, a TCP signal) is received, a signal instructing an n-stage fallup is named CFRn (n is a positive integer). for example,
The signal instructing one-stage fallup is CFR1. After transmitting the TCP signal, when the transmitter receives the n-stage fall-up instruction signal, the transmitter transmits the NSS/TSI signal again.
Following the /DC5 signal, the training/TCF signal is transmitted at the fallen-up speed.

In the above embodiment, when the receiver receives the TCP signal, ■ the time during which "0" data is continuously received is 1.0;
When the time is longer than 1 second, the CFRO signal indicates that image transmission is to be performed at that transmission speed. ■When the time when continuous "O" data is received is 0.8 seconds or more and less than 1.0 seconds, there is a 1-step fall. NSS/TSI/DC5 declared backing up
FTT without instructing the transmitter to transmit the training/TCF signal and one-step fallback training/TCF signal.
1 signal, ■The time when “0” data is received continuously is 0
When the time is 6 seconds or more and less than 08 seconds, the NSS/TSI/DC5 signal declares a two-step fallback, and
FTT 2 signal that instructs the transmitter to transmit the training/TCF signal with 2-step fallback.■If the time when continuous "0" data is received is less than 0.6 seconds, 3-step fallback is performed. NSS declared that
Transmit an FTT 3 signal instructing the transmitter to transmit the TSI/DC5 signal and the training/TCF signal with three-step fallback. Also, when fallback of the specified number of stages is not possible, the transmitter
(Line disconnection signal) Sends a signal.

Next, a specific example of a fall-up instruction will be described in the case where the receiver continuously receives "0" data for 1.0 seconds or more.

For example, if the receiver receives ``o'' data continuously for a period of 1.0 seconds or more but less than 1.2 seconds, the receiver transmits the image at that transmission speed. When the time when "0" data is received is 1.2 seconds or more and less than 1.4 seconds, a one-step fall-up is declared.
SS/TSI/DC5 signal and CFR1 signal that instructs the transmitter to transmit the training/TCF signal with one-step fall-up. ■The time during which "0" data is continuously received is 1.4 seconds or more. At that time, the NSS/TSI/DC5 signal declared a two-step fall-up, and the training/T signal had a two-step fall-up.
Send a CFR2 signal instructing the transmitter to transmit a CF signal. Here, if fallup is not possible for the specified number of stages, transmission at the highest speed is attempted.

Also, if the current transmission speed is the highest, C
FRn (n is 0.1.2.) may be interpreted as having the same meaning as CFRO for both the transmitter and receiver.

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 12000b/s and +4400b/s, which are provisional recommendations in CGITT Recommendation V33, the present invention may also be applied to transmission speeds of 19200b/s, which are expected to be recommended in the future.

Current Cf: 12000 according to ITT recommendation T30
Transmission speed bits in b/s, 14400b/s, 19200b/s are Dis (digital identification)
/DTC (digital transmission command) / DC5 (digital command) signal is not assigned, so signals representing non-standard functions, specifically NSF (non-standard equipment) / N5C (
It is necessary to make a bit assignment to the non-standard device command)/N5S (non-standard device setting) signal.

[Actual] 1) In the above embodiment, the negotiation as to whether or not the function according to the present invention is included is a signal representing a non-standard function, specifically, a bit assignment signal to the NSF/NSC/NSS function. This was done by However, this function
If it is recommended at the TT meeting, ors10rc
Of course, bit assignment may be made to the 10cs signal.

1. In the above embodiment, after receiving the line status check signal, an instruction to transmit an image at the transmission speed, an instruction to fall up at a plurality of arbitrary stages, and a plurality of arbitrary steps are given. For step-by-step fallback instructions, see
The demodulated TCP signal was received and judgment was made based on the data. In other words, the result of the modem demodulating the data is “0”.
” and “1” data. However, without using this determination method, for example, the magnitude of the error signal may be checked on the modem side, and the above instruction may be determined based on the 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 an LL automatic equalizer is shown.

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

Figure 7 shows the ID filter (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. I/ i =A i e j e l represents the first output of the equalization amount 300 in polar coordinates.

303 is a multiplier, and the output e- of the complex number generator 305 is
J91 and the equalization amount output Yi=Aie"' are multiplied together, and Zi=Yie"jsul=AH8J! θl-? I)
is output as

A determiner 310 determines the code point layer closest to the received signal point, which is the output of the multiplier 3θ3.

A subtracter 311 subtracts the decision point from the received signal point and outputs an error signal Ei=Zi-8i.

Subsequently, the error signal Ei is the output eJ? of the complex number generator 302? l and the multiplication are combined to obtain Eie "l'", which is fed back to the equalization amount 300. Here, ejφ is the phase correction amount.

On the other hand, the output Ei=Zi-Ai of the subtracter 311 passes through the absolute value square circuit 312 and becomes 1. 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 the number of times (N baud periods) set by the designer and is output as QL. If the line equalization rate is good and the amount of line noise is small, this QL approaches a flat value, and conversely, if the line equalization rate is poor and the amount of line noise is large, the value of QL 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 shoulder, eJ fol-')11 is approximately found.

308 is an imaginary part extractor, which outputs sin (θi−φi). 5in(θj-Pi) is approximately equal to θl-φl when θj eMφi. 306,307
are a vCO and a low-pass filter which are the constituent elements of a normal PLL, and output a phase value -φi to cancel a human phase error. Subsequently, the complex number generator 305
and 302. e-1φ1 by the complex conjugate generator 304
eJ'l'l are output, and multipliers 303 and 3
01 human power, and cancels 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-8 to CNI] 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 Yi is expressed by the following equation.

Yi=ΣCzRr −t −−−
(1) The equalization amount in the formula is based on the received data, and calculates each tap gain by MSE (Mean 5quare Erro
By successively calculating the following formula using the rJ method, it adapts to the reverse characteristics of the line.

Cz"'=C2'-aRl-z"Eie'l"--
--(2) Formula CLI+1. Tap gain value Eie'φ1 sub-winged at the i+1st time: Feedback signal α from the multiplier 301 in FIG. 5: Convergence coefficient (generally α〈〈1) In FIG. 7, 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 I'L with squared error accumulator that has been explained so far
Three methods of determining the equalization rate using the L automatic equalizer and determining the transmission rate based on the determination result will be described below.

(1) Methods to be implemented during training CI, ITT t[118V27ter segment 5 (
Signal 851) scrambled with continuous “1” and V
29 Segment 4 (Scrambled Delada °1”
4851), 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, the V29 modem error rate v, s, and SN ratio curves are drawn to determine the SN ratio with respect to the user's allowable error rate. A squared error cumulative value QL for the determined SN ratio is determined by simulation. Let this value be T.

In actual facsimile communication, if the value of Q is smaller than T, 9600 b/s is selected as the transmission speed, and T
If it is larger than 11, 7200b/S is selected as the transmission rate. Therefore, by using the above method, the transmission rate can be determined with one training.

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

The above method can also be applied 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.

(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 Q5 during this period. In this case, the above (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).

[Effects of the Invention] As explained above, according to the present invention, when transmission is performed between devices having the function of transmitting at a plurality of transmission speeds, it is possible to quickly fall-up or change the speed to suit the line conditions. It is possible to fallback. 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, even greater effects can be obtained at this time.

[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 diagram showing an embodiment of a facsimile device to which the present invention is applied. Block diagram, FIG. 4(1) and FIG. 4(2) are flowcharts showing the control procedure to be executed by the control circuit 30 shown in FIG. 3, and FIG. 5 is a PLL automatic equalization amount with square error accumulator. 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. 1) to FIG. 8(3) are diagrams showing an example of the procedure of a conventionally known facsimile machine. 12...TCP signal generation circuit, 14...V27ter or V29 modulator, 16...
...V21 modulator, 20...V21 demodulator, 22...V27ter or V29 demodulator, 300
... Equalization amount, 313 ... ID filter. R 3# branch floor fall + y-tsuku female show

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 before image information is transmitted, and the receiving side Based on the reception status of the check signal, the transmission speed is set to 1.
Or an image communication method characterized by giving an instruction from the receiving side to the transmitting side to fall up or fall back in multiple stages.