JP3511432B2 - Facsimile machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ITU-T Recommendation V.34. Facsimile apparatus for image information communication based on H.34, especially modem data rate (data signal rate)
The present invention relates to a technique related to automatic selection permission control.

[0002]

2. Description of the Related Art ITU-T Recommendation V.34. 34 is a recommendation for "a modem operating at a data signal rate of up to 28800 bit / s used in a general switched telephone network and a two-wire point-to-point telephone type leased line". According to this Recommendation, there is a modem rate re-determination protocol between pages, but its application is arbitrary.

[0003] Conventionally, V. When performing image information communication in H.34 communication, it is essential to use ECM (Error Correction Mode) of ITU-T, and an error frame retransmission method is used. By using this ECM method, an error frame (error frame) of image information can be automatically retransmitted. In this ECM method, the transmitting side facsimile device retransmits the corresponding frame by notifying the transmitting side of the error frame position of the image information received by the receiving side facsimile device.

In general, when the error does not disappear even after repeating the retransmission, the transmission side executes a shift-down protocol for reducing the data rate to reduce the data rate and continue the retransmission.

However, V. 34, the protocol does not determine the data rate, and 34 is determined by the modem sequence at the start of communication. Also, the shift down is configured so that the procedure for changing the data rate is performed before the protocol starts on the control channel between pages, so that the shift down is performed based on the retransmission request information from the receiving side as in the past. Can't judge.

FIG. 9 shows an example of a protocol sequence for retransmitting and downshifting an error frame in the conventional ECM system. If the received image information frame has an error, the receiving side RX notifies the transmitting side TX of the error frame position by a PPR (partial page request) signal, and the transmitting side TX automatically retransmits the corresponding frame based on this. This PPR signal is 4
When the transmission side TX is received, a CTC (continuation of correction) signal for downshifting is transmitted according to the judgment of the transmitting side TX.

On the other hand, in FIG. 10, FIG. 11 and FIG. 34 shows an example of a protocol sequence of a retransmission request in 34 communication.

In FIG. 10, a retransmission request is made from the receiving side RX by the PPR signal, but no shift down is performed in the control channel start-up sequence following the transmission of the image information PIX on the primary channel.

In FIG. 11, a shift-down (a shift-up is also possible) activation is performed from the receiving side RX. In this case, the speed (data rate) of the image information part is re-determined by the modulation parameter (MPh) sequence, and then the PP
The point that the S-EOP signal and the PPR signal are communicated is a point greatly different from the conventional protocol sequence.

In FIG. 12, shift-down (shift-up is also possible) activation is performed from the transmission side TX.

Regarding the MPh signal communicated in the above FIG. 11 and FIG. 12, the V. As described in the Recommendation No. 34, by using a predetermined bit of the MPh signal,
The data rate of image information can be redetermined. Modulation parameter (MPh) sequences are exchanged between modems during startup and control channel resynchronization. It contains the modulation parameters used in data mode transmission.

[0012]

As described above, the IT
UT Recommendation V.5. 34, the protocol does not determine the data rate, and 34 is determined by the modem sequence at the start of communication. Also, the shift down is configured to execute the data rate changing procedure before the protocol is started on the control channel between pages, so that the shift is performed based on the retransmission request information from the receiving side as in the past. Since it is not possible to determine whether the communication is down, there has been a problem in improving communication efficiency and reducing communication cost.

Further, the shift down request can be made not only from the transmitting side but also from the receiving side, but the parameter for requesting the down shift is unclear (determine when to perform the down down. However, there is a problem that it can be done arbitrarily.

Therefore, the present invention has been made in order to solve such a problem, and based on the retransmission status confirmed at the transmitting side or the receiving side, whether or not to perform downshift and continue retransmission It is an object of the present invention to provide a facsimile apparatus that can determine whether or not to improve communication efficiency.

It is another object of the present invention to provide a facsimile apparatus capable of improving communication efficiency by accurately performing downshifting and suppressing the occurrence of errors.

[0016]

The invention according to claim 1 of the present application is based on 34 modem, the modem has the function of determining the data rate of image information communication according to the transmission quality of the communication line, and the control signal including the error frame retransmission function after the primary channel in which image information communication is performed. Before starting the interacting control channel,
In a facsimile apparatus using a protocol capable of executing a downshift procedure for reducing the data rate from both the transmitting side and the receiving side, data rate detecting means for detecting the data rate at the time of retransmission of an error frame and retransmission at the same data rate Retransmission number counting means for counting the number of times, determination means for determining whether or not a predetermined number of retransmissions have been performed at the same data rate, and downshifting procedure when a predetermined number of retransmissions have been performed at the same data rate And a control means for executing.

Further, the invention according to claim 2 is the facsimile apparatus according to claim 1, further comprising a retransmission frame number detecting means for detecting the number of retransmission frames at each error frame retransmission time, and the control means are the same. The shift-down procedure is executed based on the number of retransmissions and the number of retransmission frames reduced depending on the data rate.

On the other hand, the invention described in claim 3 similarly,
V. 34 modem, the modem has the function of determining the data rate of image information communication according to the transmission quality of the communication line, and the control signal including the error frame retransmission function after the primary channel in which image information communication is performed. In a facsimile apparatus using a protocol capable of executing the above-mentioned shift-down procedure for reducing the data rate from both the transmitting side and the receiving side before the control channel for communication is started, Line quality information reading means for reading out information about the transmission quality from the modem, line quality judging means for judging the transmission quality of the communication line based on the read line quality information, and the transmission quality of the communication line is lower than a predetermined value. In this case, a control means for executing a downshift procedure is provided.

Further, the invention according to claim 4 is the facsimile apparatus according to claim 3, further comprising error frame number detection means for detecting the error frame number of the image information, and the control means is for the communication line. The shift-down procedure is executed based on the transmission quality and the error frame occurrence rate.

[0020]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system configuration diagram of a facsimile apparatus according to the first embodiment (corresponding to claim 1).
The facsimile apparatus according to the present exemplary embodiment includes a scanner 1 that scans a document to read image information, a plotter 2 that records and outputs the received image information or the image information read by the scanner 1, and a scanner 1 that reads the image information. An encoding / decoding unit 3 that encodes and compresses the received image information, decodes and expands the received encoded image information to reproduce the original image information, and communication that performs protocol control as described in the present application. Control unit 4
And ITU-T Recommendation V. A modem 5 having a communication function satisfying 34 to modulate / demodulate communication data, a network control unit 6 connected to a line (general switched telephone network) to control incoming and outgoing calls, and an operation display unit 7 serving as an interface with an operator. When,
A system control unit 8 that performs predetermined facsimile control and performs processing and control for realizing each invention of the present application described later.
And a data rate storage unit 9 for storing the data rate automatically determined by the modem 5 together with the number of transmissions. Here, in order to determine the shift down from the data rate at the time of retransmission stored in the data rate storage unit 9 and the number of times, for example, when the third retransmission is performed at the same data rate, the shift down is performed. Can be controlled.

Next, the operation of the first embodiment will be described.

FIG. 2 shows a processing flow on the transmitting side in this embodiment. First, Recommendation V. When the image information transmission based on 34 is started (Y in judgment 101), the data rate of the transmitted image information is detected from the modem 5 and stored in the data rate storage unit 9 together with the number of transmissions (process 102). When the transmission of the image information of the page is completed (Y in determination 103), the number of retransmissions at the same data rate is counted from the data stored in the data rate storage unit 9 (process 104), and the number of retransmissions at the same data rate is predetermined. Number of times (eg 3 times)
It is checked whether or not has reached (decision 105). Here, since the retransmission has not been performed yet, the number of retransmissions at the same data rate has not reached the predetermined number (N in decision 105), and the process proceeds to the next decision 106. In this judgment 106, it is checked whether or not there is a shift-down request from the receiving side. If not, the control channel protocol is started at the same data rate (same speed) as before (N in judgment 106). → Process 107). On the other hand, if there is a shift-down request from the receiving side, a predetermined shift-down procedure is executed to start the control channel protocol (Y in decision 106 → process 108).

When the control channel protocol is started in the processing 107 or 108, next, it is checked whether or not there is a response from the receiving side whether or not the page is correctly received (decision 109). If there is a response indicating that the page was correctly received, the transmission of the page is terminated (decision 1
09 Y), when the PPR signal for notifying the retransmission request frame of the image information sent from the transmitting side that cannot be correctly received to the transmitting side is received, the V.
The 34-image information retransmission processing is started (N in judgment 109 → Y in judgment 110). Here, the data rate of the retransmitted image information is detected by the modem 5, stored in the data rate storage unit 9, and returned to the page transmission end determination 103 again, and the subsequent processing is repeated.

During this repetition, when the number of retransmissions at the same data rate reaches a predetermined number (for example, 3 times), the process shifts from the determination 105 to the process 108 and is similar to the case where the receiving side requests a downshift. Then, a predetermined shift-down procedure is executed to start the control channel protocol.

As described above, according to this embodiment, it is possible to determine whether or not to continue the retransmission by downshifting according to the retransmission status of the transmitting side. Also, it becomes possible to determine whether to perform the shift down and the retransmission, the communication efficiency is improved, and the communication cost can be reduced.

FIG. 3 is a system configuration diagram of a facsimile apparatus according to the second embodiment (corresponding to claim 2).
In the first embodiment, whether downshifting is necessary is determined based on the number of times an error frame is retransmitted at the same data rate. Therefore, retransmission can be performed according to the line condition, so communication efficiency is improved. However, even if the number of error frames does not decrease even if the frame is retransmitted without a shift-down request from the receiving side, down-shifting is performed after repeating a predetermined number of times of retransmission, so improvement in communication efficiency cannot be expected in such a case. It is possible.

In consideration of such a point, in the present embodiment, a transmission frame number storage unit 10 for storing the number of transmission frames is added to the system configuration of FIG. Then, when one of the predetermined conditions is satisfied among the number of times of retransmission at the same data rate stored in the data rate recording unit 9 and the decrease status of the number of retransmission frames stored in the transmission frame number storage unit 10 Be sure to perform a downshift procedure. The condition of the number of retransmissions at the same data rate is the same as that of the first embodiment, and the condition of using the number of transmission frames is that the number of frames transmitted last time is compared with the number of frames transmitted this time, and the reduction status is predetermined. If the threshold is not satisfied, the downshift procedure is performed. For example, if 100 frames are transmitted first and 10 frames are transmitted at the time of retransmission, the shift down procedure is performed.

Next, the operation of the second embodiment will be described.

FIG. 4 shows a processing flow on the transmitting side in this embodiment. In the processing flow of FIG. 4, the number of frames to be transmitted is stored at the start of transmission and compared at the end of transmission. At this time, if either condition of the number of retransmissions at the same data rate or the reduction condition of the number of frames is satisfied, the downshift procedure is executed.

That is, as in the case of the first embodiment described above, first, the recommended V. When the image information transmission based on 34 is started (Y in determination 201), the data rate of the transmitted image information is set to the modem 5
It is stored in the data rate storage unit 9 together with the number of transmissions (process 202). Further, the number of frames to be transmitted is stored in the transmission frame number storage unit 10 (process 203).
Then, when the image information transmission of the page is completed (determination 2
04), the number of retransmissions at the same data rate is counted from the data stored in the data rate storage unit 9 (processing 205), and whether the number of retransmissions at the same data rate has reached a predetermined number (for example, 3 times). It is checked whether or not (decision 206). Here, since the retransmission has not been performed yet, the number of retransmissions at the same data rate has not reached the predetermined number (N in decision 206), and the process proceeds to the next decision 207. In this judgment 207, it is checked whether or not there is a shift-down request from the receiving side.
Go to 8. In this judgment 208, it is checked whether or not the number of retransmission frames has decreased by a predetermined amount. However, since the retransmission has not been performed yet, the control channel protocol is started with the same data rate (same speed) as before. (Y in determination 208 → process 209). On the other hand, if there is a shift-down request from the receiving side in the judgment 207, a predetermined shift-down procedure is executed to start the control channel protocol (Y in judgment 207 → process 210).

When the control channel protocol is started in the processing 209 or 210, next, it is checked whether or not there is a response from the receiving side whether or not the page is correctly received (decision 211). If there is a response indicating that the page has been correctly received, the transmission of the page is terminated (decision 2
11Y), when the PPR signal for notifying the retransmission request frame of the image information sent from the transmitting side that cannot be correctly received to the transmitting side is received, the V.
The 34-image information retransmission processing is started (N in judgment 211 → Y in judgment 212). Here, the data rate of the retransmitted image information is detected by the modem 5, stored in the data rate storage unit 9, and returned to the processing 203 of storing the number of transmission frames, and the subsequent processing is repeated.

During this repetition, when the number of retransmissions at the same data rate reaches a predetermined number (for example, 3 times), the process shifts from the determination 206 to the process 210 and is the same as when the receiving side requests a downshift. Then, a predetermined shift-down procedure is executed to start the control channel protocol. Further, even if the number of retransmissions does not reach the predetermined number and there is no shift-down request from the receiving side, if the number of retransmission frames does not decrease by the predetermined amount, the determination 20
From 8 to 210, the predetermined shift-down procedure is executed and the control channel protocol is started in the same manner as above.

As described above, according to the present embodiment, even if there is no shift-down request from the receiving side, the down-shifting can be performed at the sending-side's discretion if the retransmission continues with the error frames not significantly reduced. Further, the communication efficiency is improved and the communication cost can be reduced.

FIG. 5 is a system configuration diagram of a facsimile apparatus according to the third embodiment (corresponding to claim 3).
Here, the control for making a downshift request from the receiving side facsimile apparatus is described. Conventionally, it is general that some kind of line quality information can be read as a guide for displaying the reception state during image information reception. In the present embodiment, this value is read out and compared with a threshold value that can be set arbitrarily to start the downshift procedure from the receiving side. The read value is stored in the line quality information storage unit 11 in the figure, and the shift down judgment can be made at the end of receiving the image information. The other components shown in the figure are the same as those in the above embodiment.

Next, the operation of the third embodiment will be described.

FIG. 6 shows a processing flow on the receiving side in this embodiment. First, Recommendation V. When the image information reception based on 34 is started (Y in determination 301), the line quality information is read from the modem 5 and stored in the line quality information storage unit 11 (process 302). Here, it is necessary to continue reading at a fixed timing and continue updating the value of the worst quality in the storage unit 11 (N of judgment 303 → loop of processing 302). 1
When the page receiving process is completed (Y in decision 303),
The minimum value of the quality information stored in the line quality information storage unit 11 is read to determine the line quality and compare it with a predetermined threshold to determine whether to execute the downshift procedure (decision 3).
04). If the line quality value is equal to or higher than the predetermined threshold value, the control channel protocol is started with the same data rate (same speed) as before (N in decision 304 → process 305). On the other hand, if the line quality value does not reach the predetermined threshold value, the predetermined shift-down procedure is executed to start the control channel protocol (Y in judgment 304 →
Process 306).

When the control channel protocol is started in the process 305 or the process 306, it is then checked whether or not the received page has been correctly received, and if it is correctly received, the reception of the page is terminated ( (Y of judgment 307) If not correctly received, it is checked whether or not re-transmission / reception is possible by transmitting the PPR signal which notifies the transmitting side of the retransmission request frame of the image information (decision 30).
N of 7 → judgment 308). If re-transmission / reception cannot be performed, the process ends (N in decision 308), but if re-transmission / reception is possible, the process returns to the process 302 and the subsequent image information reception phase is repeated.

As described above, according to the present embodiment, since it is possible to judge the line quality from the line quality information on the receiving side and accurately request the downshift, the reception at the data rate suitable for the line situation is possible. It is possible to suppress the occurrence of errors, improve the communication efficiency, and reduce the communication cost.

FIG. 7 is a system configuration diagram of a facsimile apparatus according to the fourth embodiment (corresponding to claim 4).
According to the third embodiment, it is possible to control the necessity of downshifting based on the line quality information obtained from the receiving modem, so that the communication efficiency is improved. However, even if the line quality information is degraded, the image information may be normally received depending on its content. On the contrary, even if the line quality information is good, the image information may be in error.

In consideration of such a point, in this embodiment, an error frame number storage unit 12 is added to the system configuration of FIG. Number of frames received during image information reception and number of frames for which retransmission is requested (number of error frames)
Remember. When the ratio of the number of error frames (error frame rate) is greater than or equal to the arbitrarily set threshold, downshift is performed even if the line quality information is good, and the error frame rate is less than or equal to the arbitrarily set threshold. In this case, the downshift is not performed even if the line quality information is degraded. For example, if a request to retransmit 10 frames is made and error frames are 5 frames or more, downshift is performed even if the channel quality information is good, and if 2 frames or less, shift down is performed even if the channel quality information is deteriorated. Do not do it.

Next, the operation of the fourth embodiment will be described.

FIG. 8 shows a processing flow on the receiving side in this embodiment. The number of error frames of the frames received during the image information reception is stored, and at the end of the reception, it is determined whether or not the shift down is performed based on the line quality information and the frame error rate.

That is, as in the case of the third embodiment, first, the recommendation V.34. When the image information reception based on 34 is started (Y in judgment 401), the line quality information is read from the modem 5 and stored in the line quality information storage unit 11 (process 402).
In addition, the number of error frames received during image information reception is stored in the error frame number storage unit 12 (process 403). Then, the above processing 402 and processing 403 are repeated until one page reception processing is completed (N loop of determination 404). When one page reception process ends (determination 404
Y), the minimum value of the line quality information stored in the line quality information storage unit 11 is read to determine the line quality and compare it with a predetermined threshold to determine whether to perform downshift based on the line quality information. (Judgment 405). Here, if the line quality is not equal to or lower than the predetermined value, it is further determined whether or not the error frame rate exceeds a predetermined threshold value E2 (for example, 50%) (N of the determination 405 → determination 406), and
If the line quality is equal to or lower than the predetermined value, it is further determined whether or not the error frame rate is less than a predetermined threshold value E1 (for example, 20%) (Y in determination 405 → determination 407).

If the line quality is not lower than the predetermined value and the error frame rate does not exceed the threshold value E2, the protocol of the control channel is started with the same data rate (same speed) as before (N of judgment 405 → N of judgment 406
→ Processing 408), if the error frame rate exceeds the threshold value E2, a predetermined shift-down procedure is executed to start the control channel protocol (N in judgment 405).
→ Y of judgment 406 → process 409). On the other hand, if the line quality is equal to or lower than the predetermined value and the error frame rate is equal to or higher than the threshold value E1,
A predetermined shift-down procedure is executed to start the protocol of the control channel (Y in judgment 405 → decision 4).
07 N → process 409), the error frame rate is the threshold value E1
If not satisfied, the control channel protocol is started with the same data rate (same speed) as before (Y in judgment 405 → Y in judgment 407 → Process 408).

When the control channel protocol is started in the above processing 406 or processing 409, it is then checked whether or not the received page has been correctly received, and if it has been correctly received, the reception of the page is terminated ( (Y of judgment 410) If not correctly received, it is checked whether or not re-transmission / reception is possible by transmitting the PPR signal which notifies the transmitting side of the retransmission request frame of the image information (decision 41).
N of 0 → judgment 411). If re-transmission / reception cannot be performed, the process ends (N in decision 411). If re-transmission / reception is possible, the process returns to the process 402 and the subsequent image information reception phase is repeated.

As described above, according to the present embodiment, since it is possible to request downshift by judging from both the line quality information on the receiving side and the error frame rate, the data rate more suitable for the line condition can be obtained. Can be received, communication efficiency can be further improved, and communication cost can be reduced.

Although the processing flow on the transmission side is shown in the first and second embodiments and the processing flow on the reception side is shown in the third and fourth embodiments, the transmission processing and the reception processing are described. By exchanging them, they can be implemented on the receiving side and the transmitting side, respectively.

Further, in each of the above-described embodiments, each storage section is described as being provided independently for the sake of easy understanding, but in general, the system control section 8 is provided.
Is a ROM area for storing programs executed by the CPU, and a RAM used as a work area for executing the programs.
Since it has an area, it is possible to allocate the above-mentioned respective storage units to this RAM area.

[0050]

As described above, according to the invention of claim 1 of the present application, V.I. 34 modem, the modem has the function of determining the data rate of image information communication according to the transmission quality of the communication line, and the control signal including the error frame retransmission function after the primary channel in which image information communication is performed. Data for detecting the data rate at the time of retransmitting an error frame in a facsimile apparatus using a protocol capable of executing the above-mentioned shift-down procedure for reducing the data rate from both the transmitting side and the receiving side before the control channel for communication is started. A rate detecting means, a retransmission number counting means for counting the number of retransmissions at the same data rate, a determining means for determining whether or not a predetermined number of retransmissions at the same data rate have been performed, and a predetermined number of retransmissions at the same data rate. Control means for executing the downshift procedure when Since, it shifted down so that it is retransmitted to continue determining whether or not in response to a retransmission situation. Therefore, it is possible to determine whether to retransmit the data at the same data rate or downshift and retransmit the data, thereby improving the communication efficiency and reducing the communication cost.

Further, according to the invention described in claim 2, in the facsimile apparatus according to claim 1, there is provided a retransmission frame number detecting means for detecting the number of retransmission frames at each error frame retransmission time, and the control means comprises: Since the downshift procedure is executed based on the number of retransmissions and the number of retransmission frames with the same data rate, even if there is no downshift request from the other side, if the number of error frames does not decrease much Since the shift down can be performed by the side's judgment, there is an effect that communication efficiency is further improved and communication cost can be reduced.

On the other hand, according to the third aspect of the invention, the V. 34 modem, the modem has the function of determining the data rate of image information communication according to the transmission quality of the communication line, and the control signal including the error frame retransmission function after the primary channel in which image information communication is performed. In a facsimile apparatus using a protocol capable of executing the above-mentioned shift-down procedure for reducing the data rate from both the transmitting side and the receiving side before the control channel for communication is started, Line quality information reading means for reading out information about the transmission quality from the modem, line quality judging means for judging the transmission quality of the communication line based on the read line quality information, and the transmission quality of the communication line is lower than a predetermined value. In this case, since the control means for executing the downshift procedure is provided, the line quality information of the modem You may request accurately downshifting to determine the quality. Therefore, there is an effect that communication can be performed at a data rate suitable for the line condition, the occurrence of errors is suppressed, the communication efficiency is improved, and the communication cost is reduced.

Further, according to the invention described in claim 4, in the facsimile apparatus according to claim 3, an error frame number detection means for detecting the error frame number of image information is provided, and the control means is the communication line. Since the downshift procedure is executed based on the transmission quality of the frame and the error frame occurrence rate, the downshift can be requested by judging from both the line quality information of the modem and the error frame rate. It is possible to perform communication at a data rate suitable for the line condition, further improve communication efficiency, and reduce communication cost.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a facsimile apparatus according to a first embodiment of the present application.

FIG. 2 is a diagram showing a processing flow of the embodiment.

FIG. 3 is a system configuration diagram of a facsimile apparatus according to a second embodiment.

FIG. 4 is a diagram showing a processing flow of the embodiment.

FIG. 5 is a system configuration diagram of a facsimile apparatus according to a third embodiment.

FIG. 6 is a diagram showing a processing flow of the embodiment.

FIG. 7 is a system configuration diagram of a facsimile apparatus according to a fourth embodiment.

FIG. 8 is a diagram showing a processing flow of the embodiment.

FIG. 9 is a diagram showing a protocol sequence example of a retransmission request and a shift-down procedure in conventional ECM communication.

FIG. 34 is a diagram showing a protocol sequence example of retransmission request control (without downshifting) in H.34 communication.

FIG. 11: V. 34 is a diagram showing a protocol sequence example of retransmission request control (shift down request from the receiving side) in 34 communication. FIG.

FIG. 12: V. 34 is a diagram showing a protocol sequence example of retransmission request control (shift down request from the transmission side) in 34 communication. FIG.

[Explanation of symbols]

1 scanner 2 plotters 3 Encoding / decoding section 4 Communication control unit 5 modem 6 Network control unit 7 Operation display section 8 System control unit 9 Data rate storage 10 Transmission frame number storage unit 11 Line quality information storage 12 Error frame number storage

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Claims (4)

(57) [Claims] 1. V. 34 modem, the modem has the function of determining the data rate of image information communication according to the transmission quality of the communication line, and the control signal including the error frame retransmission function after the primary channel in which image information communication is performed. Data that detects the data rate at the time of error frame resending in a facsimile machine that uses a protocol that allows the transmission side and the receiving side to execute the shift-down procedure to reduce the above data rate before starting the control channel for communication. Rate detecting means, retransmission number counting means for counting the number of retransmissions at the same data rate, determining means for determining whether or not the number of retransmissions at the same data rate has been performed a predetermined number of times, and number of retransmissions at the same data rate is predetermined Control means to execute the downshift procedure when A facsimile machine characterized by the above. 2. A retransmission frame number detecting means for detecting the number of retransmission frames for each error frame retransmission, wherein the control means executes a shift-down procedure based on the number of retransmissions at the same data rate and the reduction status of the number of retransmission frames. The facsimile apparatus according to claim 1, wherein the facsimile apparatus comprises: 3. V. 34 modem, the modem has the function of determining the data rate of image information communication according to the transmission quality of the communication line, and the control signal including the error frame retransmission function after the primary channel in which image information communication is performed. Before starting the control channel for exchanging data, in a facsimile machine using a protocol capable of executing a shift-down procedure for lowering the above data rate from both the transmitting side and the receiving side, Line quality information reading means for reading information about transmission quality from the modem, line quality judging means for judging the transmission quality of the communication line based on the read line quality information, and transmission quality of the communication line has fallen below a predetermined value. And a control means for executing a down-shifting procedure. . 4. An error frame number detecting means for detecting an error frame number of image information, wherein the control means executes a downshift procedure based on a transmission quality of the communication line and an error frame occurrence rate. The facsimile apparatus according to claim 3, which is characterized in that.