JPH04211568A - Facsimile equipment - Google Patents

Abstract

PURPOSE:To improve the transmission speed of the facsimile device and to prevent the generation of communication errors by controlling a cable equalizer or (and) delay equalizer according to a circuit condition. CONSTITUTION:Facsimile communication or the transmission of image data is executed by properly selecting and setting the value of the cable equalizer built in a MODEM 32 or mounted externally thereon or (and) the value of the delay equalizer according to the circuit condition at the time of setting the transmission speed of the MODEM 32 or retransmission of the image data.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a facsimile machine, and more particularly to a facsimile machine that performs communication by setting cable equalizer and delay equalizer values according to transmission quality.

0002

2. Description of the Related Art In facsimile communication, when a call is set up and a predetermined control procedure is completed, the transmission speed of the modem is determined prior to communication of image data. Conventionally, the modem transmission speed is determined by sending out a TCF (training check) signal (usually a continuous signal of "0") from the sending facsimile machine at a predetermined transmission speed, and the receiving side detects the number of error bits in this TCF signal. The success of communication is determined by detecting whether the number of error bits is below a predetermined reference value.
This is done by determining failure and transmitting a CFR signal (reception preparation confirmation signal) or FTT signal (training failure signal). That is, the sending facsimile device usually first selects the fastest transmission speed (for example, 9600
The receiving facsimile machine detects the number of error bits in the TCF signal. When the number of error bits is less than a predetermined reference value, the facsimile machine on the receiving side sends out a CFR signal, and the transmission speed at that time is adopted. Additionally, if the number of error bits is greater than or equal to a predetermined reference value, the facsimile machine on the receiving side will
The facsimile machine on the sending side sends the FTT signal.
When a signal is received, the transmission speed is lowered by one step and the TCF is started again.
Send a signal. The above process is repeated until a CFR signal is sent from the receiving facsimile machine.

On the other hand, facsimile apparatuses conventionally use a cable equalizer function so that the transmission speed can be set as high as possible, thereby suppressing the influence of passband characteristics as low as possible. That is, when data communication is performed using an analog line, data is distorted due to deterioration factors such as amplitude distortion and delay distortion of the line, causing errors. In particular, amplitude distortion degrades the level in the high frequency band, and as shown in FIG. 5, degrades the high frequency band of the signal received by the receiving facsimile machine.

[0004] Therefore, the present applicant has proposed a data communication device that automatically sets a cable equalizer value for each transmission destination based on transmission history information for each transmission destination (Patent Application No. 1999). -172704). This data communication device sets a cable equalizer value in advance based on transmission history information when performing modem training.

[0005] Conventionally, in facsimile communication, in order to accurately send and receive image data, HDLC (
Using the high-level data link) method, image data is divided into blocks, and each block is sent and received while error checking is performed using ECM (error correction method), and the image data of the block where the error occurred is retransmitted. There are ways to respond to the occurrence of errors. That is, image data is divided into blocks and transmitted/received, and the presence or absence of an error is checked for each block. If an error has occurred in a block, the image data of the book is retransmitted. Therefore, it is highly effective against transient disturbances (line interruption, impulse noise, etc.).

[0006]

[Problems to be Solved by the Invention] However, in facsimile machines that do not have such a conventional cable equalizer function, in order to determine the transmission speed of the modem, the TCF signal is simply calculated from the highest transmission speed. The number of error bits was detected each time the transmission started, and the transmission speed was determined by lowering the transmission speed one step at a time until the number of error bits fell below a predetermined reference value, so it took a long time to determine the transmission speed. This not only takes time and increases communication costs, but also causes problems in that slow transmission speeds are set when line conditions are poor.

[0007] Furthermore, in the data communication device previously filed by the present applicant, the cable equalizer value was set prior to modem training;
If you sequentially lower the transmission speed to determine the modem's transmission speed, you may not be able to set the appropriate cable equalizer value for each transmission speed, and the transmission speed may end up being set to a slow one. There was room for improvement.

Furthermore, in the data communication device previously filed by the present applicant, only the cable equalizer was adjusted, so for lines where group delay distortion cannot be ignored, the transmission conditions sufficiently correspond to the line conditions. It was not possible to make adjustments, and there was room for further improvement. In addition, when image data is sent and received using HDLC and error checking is performed using the ECM communication method, if the data communication device that the applicant previously applied for is applied as is, the image data is transferred using the ECM communication method. Even if an error occurs and the data is retransmitted, the cable equalizer and delay equalizer are not adjusted, and there is a risk that the error will occur again even if the image data is retransmitted. This is because errors may occur in the transmission of image data due to changes in the deterioration state of the transmission path during communication, even if there is no transient failure. In such a case, there is a problem in that image data is retransmitted many times, increasing communication costs.

[0009]

[Means to solve the problem]

The invention according to claim 1 provides the following: At the start of transmission, a TCF signal is sent, the success or failure of the communication is determined based on the CFR signal and FTT signal sent from the receiving side, and when the FTT signal is received, the TCF signal is sent. In a facsimile machine that sets a communication speed by shifting down the communication speed, a set value of a cable equalizer corrects the passband characteristic of a transmission path in accordance with the set value of the communication speed each time the communication speed is shifted down. The invention according to claim 2 is characterized in that, in a facsimile device that performs facsimile communication by executing a facsimile control procedure with a communication terminal connected via a public line, the communication status between at least two or more cable equalizers with different setting values for correcting the passband characteristics of the transmission line, at least two or more delay equalizers with different setting values for correcting the group delay distortion of the transmission path, and the other communication terminal; The invention according to claim 3 is characterized in that it is provided with a selection means for appropriately selecting the cable equalizer and the delay equalizer according to the transmission. At the start, a TCF signal is sent, and the success or failure of communication is determined based on the CFR signal and FTT signal sent from the receiving side. When the FTT signal is received, the communication speed is sequentially shifted down and the communication speed is increased. In the facsimile machine, at least two or more cable equalizers have different setting values for correcting the passband characteristics of the transmission line, at least two or more delay equalizers have different setting values for correcting the group delay distortion of the transmission line, and the above-mentioned The invention according to claim 4 is characterized in that a selection means is provided for appropriately selecting the cable equalizer and the delay equalizer each time a downshift is performed, and the invention as claimed in claim 4 provides the following: Then, the facsimile control signal is executed, and the image data is transmitted and received by dividing the image data into predetermined block units and transmitting and receiving each block by HDLC.
In a facsimile machine that performs an error check using an ECM communication method and retransmits image data of a block in which an error has occurred, at least two or more cable equalizers with different setting values for correcting the passband characteristics of the transmission path and a group of transmission paths are provided. at least two delay equalizers with different setting values for correcting delay distortion, and the cable equalizer and the delay equalizer each time image data of a block in which an error occurs is retransmitted during the transmission/reception of image data in units of blocks. The present invention is characterized in that it is provided with a selection means for appropriately selecting.

0010

[Operation] The invention as set forth in claim 1 provides that when the transmission speed is set by sequentially downshifting the communication speed, the passband of the transmission path is changed in accordance with the setting position of the communication speed each time the communication speed is shifted down. The settings of the cable equalizer that corrects the characteristics have been changed.

[0011] Therefore, it is possible to set the optimum cable equalizer for the communication speed, and to quickly set the communication speed, as well as to set the communication speed as high as possible. As a result, the running cost and communication cost of the facsimile machine can be reduced. The invention according to claim 2 provides a setting for correcting the passband characteristics of a transmission path in a facsimile device that performs facsimile communication by executing a facsimile control procedure with a communication terminal connected via a public line. At least two or more cable equalizers with different values, at least two or more delay equalizers with different set values for correcting group delay distortion of the transmission path, and the cable equalizer and the delay equalizer depending on the communication state between the other communication terminal. A selection means for appropriately selecting the cable equalizer and delay equalizer suitable for the communication condition is provided.

Therefore, even during communication, it is possible to always set the optimum cable equalizer and delay equalizer according to the passband characteristics and group delay distortion of the transmission path, thereby suppressing the occurrence of errors. At the same time, you can set the communication speed to be as fast as possible. As a result, communication can be performed appropriately and communication costs can be reduced.

[0013] The invention according to claim 3 transmits a TCF signal at the start of transmission between the other party's facsimile machine connected via a public line, and responds to the CFR signal and FTT signal sent from the receiving side. In a facsimile machine that determines the success or failure of communication based on the FTT signal and sets the communication speed by sequentially downshifting the communication speed when an FTT signal is received, at least two different setting values for correcting the passband characteristics of the transmission path are used. The above cable equalizer, at least two or more delay equalizers having different set values for correcting group delay distortion of the transmission path, and selection means for appropriately selecting the cable equalizer and the delay equalizer each time the downshift is performed are provided. When setting the communication speed, the cable equalizer and delay equalizer that are most suitable for the communication condition are selected as appropriate.

[0014] Therefore, it is possible to set the optimum cable equalizer and delay equalizer for the transmission line according to the passband characteristics and group delay distortion of the transmission line at the initial stage of communication.
It is possible to set the communication speed to be as fast as possible while suppressing the occurrence of errors. As a result, communication can be performed appropriately and communication costs can be reduced.

[0015] The invention according to claim 4 executes a facsimile control signal between the other party's facsimile device connected via a public line, and transmits and receives image data in units of predetermined blocks. Divide the data into blocks and transmit and receive each block using HDLC.
In a facsimile machine that performs an error check using an ECM communication method and retransmits image data of a block in which an error has occurred, at least two or more cable equalizers with different setting values for correcting the passband characteristics of the transmission path and a group of transmission paths are provided. at least two delay equalizers with different setting values for correcting delay distortion, and the cable equalizer and the delay equalizer each time image data of a block in which an error occurs is retransmitted during the transmission/reception of image data in units of blocks. and selecting means for appropriately selecting between the cable equalizer and the delay equalizer when retransmitting the image data.

Therefore, when an error occurs during transmission/reception of image data and the image data is retransmitted, the cable equalizer and delay equalizer can be set to those optimal for the transmission path, and the image data is It is possible to prevent errors from occurring during retransmission, and while setting the communication speed to be as fast as possible, it is possible to suppress the occurrence of errors and perform communication appropriately, and to reduce communication costs. .

[0017]

[Example] The following is a detailed explanation based on an example. 1 to 4 are diagrams showing an embodiment of a facsimile apparatus according to the invention as claimed in claim 1. FIG. 1 is a block diagram of the facsimile device 1. The facsimile device 1 includes a system control section 2, a communication control section 3, a modem 4, a network control section 5,
It includes an encoding/decoding section 6, a line buffer memory 7, a display section 8, an operation section 9, a scanner 10, a plotter 11, and the like.

[0018] The system control unit 2 includes a CPU (Central
al Processing Unit), ROM (
Read Only Memory) and RAM (R
andom Access Memory), etc.
The ROM stores a basic program for the facsimile device 1, a cable equalizer value setting processing program of the present invention, and the like. The system control unit 2 controls each part of the facsimile machine 1 according to the program in the ROM,
In addition to executing the sequence as the facsimile machine 1, the cable equalizer value setting process according to the invention described in claim 1 is executed.

A line L, for example, a telephone line, is connected to the network control unit 5, and the network control unit 5 is generally connected to an AA-NC
It is called U. The network control unit 5 performs call setup, call cancellation, and the like. The modem 4 modulates the transmission signal into a form suitable for transmission on the line L when transmitting, and demodulates the modulated signal sent from the line L when receiving. Modem 4 is
It has a built-in cable equalizer, which attenuates the low frequency range of the signal more than the high frequency range according to the setting value, and improves the passband characteristics of the transmission line (line L) (see Figure 5). This is a correction. The cable equalizer has several types of values corresponding to, for example, the length of the line, and the values are switched by the system control unit 2 according to the communication speed.

[0020] The cable equalizer is not limited to one that is included in the modem itself as described above, but may be one that is installed externally apart from the modem, as shown in FIG. In the case of FIG. 2, the cable equalizer 20a,
Three types are available as 20b and 20c.
The cable equalizers 20a, 20b, and 20c are used by being switched by switches SW1, SW2, SW3, and SW4. Each of these switches SW1, SW2, SW3, SW4
is controlled by the system control section 2. In Figure 2,
21 is a 2-wire to 4-wire converter, and 22 is a modem without a built-in cable equalizer.

During facsimile communication, the communication control section 3 exchanges facsimile control signals with the other party's facsimile device and executes facsimile control procedures. The encoding/decoding unit 6 aims to shorten and improve the efficiency of transmitting image information, and compresses (encodes) image information when transmitting, and converts encoded image information into the original when receiving. Regenerate (decode) information.

The line buffer 7 is a buffer memory used when image information is internally processed by the facsimile machine 1.
It has the capacity to store image information for several lines. For example, a liquid crystal display is used as the display section 8, and the display section 8 displays the contents of commands input from the operation section 9 and various information transmitted from the facsimile machine 1 to the operator.

The operation unit 9 is provided with various operation keys such as a numeric keypad and a start key, and various commands such as a transmission command are inputted to the operation unit 9 by operating the operation keys. As the scanner 10, for example, a CCD (Charg
A line image sensor using an e-coupled device is used, and the scanner 10 has one
It reads the original line by line and outputs it as image information.

As the plotter 11, for example, a thermal recording device using a thermal element is used, and the plotter 11 records directly on thermal recording paper or indirectly on ordinary recording paper via an ink sheet. Next, the effect will be explained. The invention according to claim 1 is characterized in that when setting the communication speed of the modem, the value of the cable equalizer is changed for each rate of the modem to perform modem training. The cable equalizer value changing process in this modem training will be described below.

In facsimile communication, the sending facsimile device 1 exchanges facsimile control signals with the receiving facsimile device and sets a modem rate, as shown in FIG. 3, after establishing a line connection. That is, the sending facsimile machine 1 receives the C from the receiving facsimile machine.
When receiving an ED signal (called terminal identification signal) or a DIS signal (digital identification signal), it sends out a DCS signal (digital command signal) and then sends out a TCF signal (training check) to perform modem training.

The communication speed (transmission speed) of modem training at this time is determined by the capabilities of the facsimile machine 1 on the sending side and the facsimile machine on the receiving side.
9600bps (ccitt.v29) → 7200bp
s (ccitt.v29) → 4800bps (v27t
It is assumed that the communication speed is shifted down in the order of er) → 2400 bps (v27ter).

In this modem training, the facsimile machine 1 on the sending side first transmits the 9
The TCF signal is transmitted at a communication speed of 600 bps (step S1), and upon receiving the TCF signal, the receiving facsimile machine determines whether modem training is successful or unsuccessful based on the number of error bits of the TCF signal. That is, the receiving facsimile machine receives consecutive "0"s of the TCF signal.
The number of bits that change to "1" (error bits) is counted, and if the number of error bits is greater than a preset value, it is determined that modem training has failed, and the number of error bits is set to a predetermined value. If it is less than the value, it is determined that modem training was successful. When the receiving facsimile machine determines that modem training has failed, it transmits an FTT signal, and when it determines that modem training has succeeded, it transmits a CFR signal.

After transmitting the TCF signal, the transmitting facsimile machine 1 checks whether or not it receives an FTT signal from the receiving facsimile machine (step S2), and transmits the FTT signal.
When the T signal is received, it is determined that the modem training has failed, and the value of the communication speed at which the modem training was currently performed is checked (steps S3, S4, and S5). When the communication speed is 9600 bps, the value of the cable equalizer is set to a preset cable equalizer value E1 (step S6), the communication speed (modem rate) is lowered by one step, and a TCF signal is transmitted (step S7).

After changing the cable equalizer value and modem rate and transmitting the TCF signal, the sending facsimile device 1 determines the result by checking whether or not an FTT signal is received from the receiving side (step S8). , FTT signal is received, it is determined that modem training has failed, and it is checked whether the communication speed (modem rate) is the lowest communication speed of 2400 bps (step S9).

[0030] If the communication speed is not 2400 bps, return to step S3 and check the current communication speed (steps S3, S4, S5), and if the communication speed is 72 bps.
00 bps, the value of the cable equalizer is set to a preset cable equalizer value E2 (step S10), the communication speed is lowered by one step, and the TCF signal is sent out (step S7).

[0031] 480, one step lower than 7200bps
FT from the receiving facsimile machine even at 0bps
When the T signal is returned (step S8), the same process is repeated, the cable equalizer value is set to the preset cable equalizer value E3 (step S11), the communication speed is lowered by one step, and the TCF
A signal is sent out (step S7). This 2400bps
Also, when the FTT signal is returned, it is determined that communication cannot be performed because there is no slower communication speed, and the line is disconnected (step S1).
2). As a result of modem training by shifting down the communication speed (modem rate), when a CFR signal is returned from the receiving side (step S13), it is determined that modem training has been successful, and normal facsimile communication is resumed. The process moves on to processing (step S14).

[0032] In this way, in modem training,
When sequentially downshifting the modem rate, the cable equalizer value can be changed appropriately according to each modem rate, so it is possible to set the cable equalizer value according to the line condition, resulting in faster communication speed than before. modem training can be done successfully. Therefore, it is possible to perform facsimile communication at a faster communication speed than before, and modem training can be completed in a shorter time than before, reducing communication costs and running costs for facsimile machines. can be reduced.

FIGS. 6 to 10 represent claims 2 and 3.
1 is a diagram showing an embodiment of a facsimile device of the described invention. FIG. FIG. 6 is a block diagram of the facsimile device 30, and the facsimile device 30 of this embodiment is applied to a facsimile device similar to the facsimile device 1 shown in FIG. Therefore, in explaining this example, Fig. 1
Components similar to those of the facsimile machine 1 shown in FIG.

In FIG. 6, the facsimile machine 30 is
System control section 31, communication control section 3, modem 32, network control section 5, encoding/decoding section 6, line buffer memory 7
, display section 8, operation section 9, scanner 10 and plotter 1
It is equipped with 1st class. The system control unit 31 includes a CPU (C
internalProcessing Unit), R
OM (Read Only Memory) and RA
M (Random Access Memory), etc., and the basic program as the facsimile device 30, the cable equalizer selection processing program and the delay equalizer selection processing program of the invention recited in claims 2 and 3 are stored in the ROM. ing. The system control unit 31 controls each part of the facsimile machine 30 according to the program in the ROM, executes the sequence as the facsimile machine 30, and also performs the cable equalizer selection process and the delay equalizer selection process of the invention according to claims 2 and 3. Execute.

When transmitting, the modem 32 transmits the transmission signal to the line L.
It modulates the signal into a form suitable for transmission, and demodulates the modulated signal sent from line L when receiving. The modem 32 incorporates a plurality of cable equalizers and a plurality of delay equalizers, and each cable equalizer and delay equalizer have different setting values. As mentioned above, the cable equalizer corrects the passband characteristics of the transmission line (public line L) by attenuating the low frequency range of the signal more than the high frequency range according to its setting value.
The value of the cable equalizer to be used is selected by the system control unit 30 depending on the state of the transmission path.

[0036] The delay equalizer eliminates the group delay distortion of the line (transmission path), that is, the distortion in which the low frequency range and high frequency range of the signal are delayed when the signal is transmitted, by adjusting the low frequency in advance. The delay equalizer is corrected by outputting the high frequency range and the high frequency range earlier, and the value of the delay equalizer to be used is selected by the system control unit 31 according to the state of the transmission path.

Note that the cable equalizer and delay equalizer are not limited to those that are included in the modem itself as described above, but may also be those that are installed externally apart from the modem 32, as shown in FIG. Good too. Note that FIG. 8 shows the cable equalizers 20a, 20b, 2 shown in FIG.
A delay equalizer is connected in series to 0c, and the same components as those in FIG.

In FIG. 8, cable equalizer 20a
, 20b, and 20c are prepared for transmission and reception, and each cable equalizer 20a,
A delay equalizer 40a is connected in series to 20b and 20c.
, 40b, and 40c are connected to each other. These cable equalizers 20a are connected in series to form a pair,
20b, 20c and delay equalizers 40a, 40b
, 40c are switches SW1, SW2, SW3, SW4
are connected to switches SW1, SW2, SW3,
It is switched and selected by SW4. Each of the switches SW1, SW2, SW3, and SW4 is controlled by the system control section 31. Therefore, the system control unit 3
1 has a function as a selection means for appropriately selecting the cable equalizer and the delay equalizer according to the communication state with the other communication terminal.

Note that in FIG. 8, as in FIG.
is a 2-wire to 4-wire converter, and 22 is a modem without a built-in cable equalizer. Next, the effect will be explained. The invention described in claims 2 and 3 is characterized in that the cable equalizer and the delay equalizer are appropriately selected depending on the communication state with the other communication terminal at the appropriate time or when setting the communication speed of the modem. The process of selecting a cable equalizer and a delay equalizer when setting a modem rate will be described below.

In facsimile communication, as described above, after a line is connected, facsimile control signals are exchanged with the other party's facsimile machine, and the modem rate is set. Now, it is assumed that facsimile device 30 performs facsimile communication as a sending facsimile device. Furthermore, the facsimile machine 30 on the sending side performs modem training at 9600 bps (ccitt.v2) as described above.
9) → 7200bps (ccitt.v29) → 480
0bps (v27ter) → 2400bps (v27ter)
It is assumed that this is done by shifting down the communication speed in the order of ter).

In this modem training, the facsimile machine 30 on the sending side first performs the following steps as shown in FIG.
Transmits TCF signals at a communication speed of 9600 bps (
In step T1), upon receiving the TCF signal, the receiving facsimile device determines whether modem training is successful or unsuccessful based on the number of error bits in the TCF signal. That is,
The receiving facsimile machine receives consecutive “0’s” of the TCF signal.
” that changed to “1” (error bits), and if the number of error bits is greater than a preset value, it is determined that modem training has failed, and the number of error bits is If the number is less than a predetermined value, it is determined that the modem training was successful.When the receiving facsimile machine determines that the modem training has failed, it transmits an FTT signal, and when it determines that the modem training has been successful, it transmits a CFR signal. Send out.

After sending out the TCF signal, the sending facsimile device 30 checks whether or not it receives an FTT signal from the receiving facsimile device (step T2), and
When the TT signal is received, it is determined that the modem training has failed, and the value of the communication speed at which the modem training was currently performed is checked (steps T3, T4, and T5). When the communication speed is 9600 bps, the values of the cable equalizer and delay equalizer are set to preset cable equalizer value KE1 and delay equalizer value DE1 (step T6), and the communication speed (
Modem rate) is lowered by one step and the TCF signal is sent (
Step T7).

After changing the cable equalizer value, delay equalizer value, and modem rate and transmitting the TCF signal, the sending facsimile device 30 returns to step T2 and uses the results to determine whether or not to receive an FTT signal from the receiving side. Judgment is made by checking (step T2)
), when the FTT signal is received, it is determined that modem training has failed, and the value of the communication speed (modem rate) is similarly checked (steps T3, T4, T5). If the communication speed is 4800 bps or less, the line is disconnected and the process ends (step T8).

In steps T3, T4, and T5, when the communication speed is 7200 bps, the values of the cable equalizer and delay equalizer are set to the preset cable equalizer value EK2 and delay equalizer value DE2.
(step T9), lowers the communication speed by one step, and transmits the TCF signal (step T7). Even at 4800 bps, which is one step lower than 7200 bps, when an FTT signal is returned from the receiving facsimile machine (step T5), the same process is repeated and the cable equalizer and delay equalizer values are changed to the preset cable equalizer value KE3 and delay The equalizer value DE3 is set (step T10), the communication speed is lowered by one step, and the TCF signal is transmitted (step T7). Even at this 2400 bps, when the FTT signal is returned, it is determined that communication cannot be performed because there is no slower communication speed, and the line is disconnected (step T8).

As a result of modem training by shifting down the communication speed (modem rate) in this way, when a CFR signal is returned from the receiving side (step T11).
, it is determined that the modem training has been successful, and the process proceeds to normal facsimile communication processing (step T12). In this way, in modem training, when downshifting the modem rate sequentially, the cable equalizer value and delay equalizer value can be changed appropriately according to each modem rate, so the line condition (line attenuation distortion and group delay The cable equalizer value and delay equalizer value can be set according to the distortion (distortion), and modem training can be successfully performed at a communication speed faster than before. Therefore, it is possible to perform facsimile communication at a faster communication speed than before, and modem training can be completed in a shorter time than before, reducing communication costs. Running costs can be reduced.

FIG. 10 is a diagram showing an embodiment of a facsimile device according to the invention as claimed in claim 4, and this embodiment is applied to a facsimile device similar to the facsimile device shown in FIG. 6 above. . The facsimile machine of this embodiment uses HDLC (High-Level Data Lithium
It is possible to perform facsimile communication using the ECM (error correction method), and when an error occurs in the image data, it is possible to perform facsimile communication using the ECM (error correction method). Resend the block's image data.

The facsimile machine of this embodiment functions as a sending side, and the facsimile machine of this embodiment is shown in FIG.
0, when image data is transmitted (step P1), it is checked whether a partial page request signal (PPR) is transmitted from the receiving facsimile machine (step P2). When the PPR signal is not transmitted, it is determined that the image data of the block has been transmitted normally, and facsimile communication using the normal HDLC method is continued, and the image data of the next block is transmitted (step P3). ). When no PPR signal is received during the transmission of image data of all blocks, it is determined that no error has occurred during the transmission of all image data, and the process is terminated.

[0048] Upon receiving the PPR signal in step P2,
It is determined that an error has occurred in the transmission of the image data of the block, and a predetermined cable equalizer value KEn and delay equalizer value DEn are selected and set as the cable equalizer and delay equalizer values. The cable equalizer value KEn and delay equalizer value DEn can be set in advance according to the modem transmission speed, or the PPR
It is also possible to sequentially select the signals according to how many times the signals are received for the same image data.

When the setting of cable equalizer value KEn and delay equalizer value DEn is completed, step P
1 and transmits the image data for which the PPR signal has been received again. When the image data transmission is completed, the PP
Check whether R signal is received (step P2)
, when the PPR signal is received again, the cable equalizer values KEn and T are selected again. Cable equalizer value KEn and delay equalizer value D in this case
As described above, En is selected by appropriately selecting the cable equalizer value KEn and the delay equalizer value DEn depending on the number of times the PPR signal is received, for example.

In step P2, when no PPR signal is received, it is determined that no error occurred in the transmission of all image data, and the process is terminated. In this way, the cable equalizer and delay equalizer can be selected as appropriate when retransmitting image data, so if an error occurs during image data transmission/reception and when image data is retransmitted, the cable equalizer and delay equalizer can be selected as appropriate. The equalizer can be set optimally for the transmission path. As a result, it is possible to prevent errors from occurring when retransmitting image data, and while setting the communication speed to the highest possible speed, it is possible to suppress the occurrence of errors, and to perform communication appropriately. Costs can be reduced.

[0051]

According to the invention as claimed in claim 1, when setting the communication speed by sequentially downshifting the communication speed, each time the communication speed is shifted down, the transmission Since you can change the setting values of the cable equalizer that corrects the passband characteristics of the transmission, you can set the cable equalizer that is optimal for the communication speed, and you can quickly set the communication speed and improve the transmission speed. It is possible to set the fastest possible communication speed on the network. As a result, it is possible to reduce the running cost of the facsimile machine, and also to reduce communication costs.

According to the second aspect of the invention, it is possible to always appropriately select the cable equalizer and delay equalizer that are optimal for the communication condition, so that the passband characteristics of the transmission path can be adjusted even during communication. The optimum cable equalizer and delay equalizer can always be set according to the group delay distortion and group delay distortion. Therefore, the communication speed can be set as high as possible while suppressing the occurrence of errors, making it possible to perform communication more appropriately and reducing communication costs.

According to the third aspect of the present invention, when setting the communication speed of facsimile communication, it is possible to appropriately select the cable equalizer and delay equalizer that are most suitable for the communication condition according to the communication condition. The optimum cable equalizer and delay equalizer for the transmission path can be set according to the passband characteristics and group delay distortion of the initial transmission path. As a result, it is possible to set the communication speed as high as possible while further suppressing the occurrence of errors, and it is possible to perform communication more appropriately.
Communication costs can be further reduced.

According to the invention described in claim 4, image data is sent and received block by block by HDLC, and EC
In a facsimile machine that performs an error check using the M communication method and retransmits image data of a block in which an error has occurred, a cable equalizer and a delay equalizer are appropriately selected when retransmitting image data in which an error has occurred. , image data can be retransmitted, so if an error occurs during image data transmission/reception and the image data is retransmitted, the cable equalizer and delay equalizer can be set to the optimal one for the transmission path. can do. Therefore, it is possible to prevent the occurrence of errors when retransmitting image data, and while setting the communication speed to the highest possible speed, it is possible to further suppress the occurrence of errors and perform communication more appropriately. At the same time, communication costs can be further reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a facsimile apparatus according to the invention.

FIG. 2 is a block diagram of main parts of another embodiment of a cable equalizer for a facsimile machine according to the invention as set forth in claim 1;

FIG. 3 is a sequence diagram when setting a modem rate in a facsimile machine according to the invention as claimed in claim 1;

FIG. 4 is a flowchart showing cable equalizer value changing processing when setting a modem rate in a facsimile machine according to the invention as set forth in claim 1;

FIG. 5 is a diagram for explaining amplitude distortion of a line and correction of the amplitude distortion by a cable equalizer.

FIG. 6 is a block diagram of an embodiment of a facsimile apparatus according to the invention according to claims 2 and 3;

FIG. 7 is a diagram for explaining group delay distortion of a line in facsimile communication and correction of the group delay distortion by a delay equalizer.

FIG. 8 is a block diagram of main parts of another embodiment of a cable equalizer and a delay equalizer for a facsimile machine according to the invention as set forth in claims 2 and 3;

FIG. 9 is a flowchart showing cable equalizer value and delay equalizer value selection processing when setting a modem rate in a facsimile apparatus according to the invention according to claims 2 and 3;

FIG. 10 is a flowchart showing a process for selecting a cable equalizer value and a delay equalizer value when retransmitting image data in a facsimile apparatus according to the fourth aspect of the invention;

[Explanation of symbols]

1, 30 facsimile device 2, 31 system control unit 3 communication control unit 4, 32 modem 5 network control unit 6 encoding/decoding unit, 7 line buffer memory, 8 display unit, 9 operation unit, 10 scanner, 11 plotter, 20a, 20b, 20c cable equalizer,
21 2-wire to 4-wire converter, 22 modem, L line,

Claims (4)

[Claims] Claim 1: At the start of transmission, a TCF signal is sent, the success or failure of communication is determined based on the CFR signal and FTT signal sent from the receiving side, and when the FTT signal is received, the communication speed is sequentially adjusted. In a facsimile machine that sets a communication speed by shifting down, a setting value of a cable equalizer that corrects a passband characteristic of a transmission path is changed in accordance with the setting value of the communication speed each time the communication speed is shifted down. A facsimile device characterized by: Claim 2: In a facsimile device that executes facsimile control procedures and performs facsimile communication with a communication terminal connected via a public line, setting values for correcting passband characteristics of a transmission path are different. At least two or more cable equalizers, at least two or more delay equalizers with different setting values for correcting group delay distortion of the transmission path, and the cable equalizers and delay equalizers are adjusted appropriately according to the communication state between the other communication terminal and the other communication terminal. A facsimile device comprising a selection means for making a selection. Claim 3: Sending a TCF signal at the start of transmission between the facsimile device and the other party's facsimile device connected via a public line;
In a facsimile machine, the transmission path at least two or more cable equalizers with different set values for correcting the passband characteristics of the transmission line; at least two or more delay equalizers with different set values for correcting the group delay distortion of the transmission path; A facsimile apparatus comprising: a selection means for appropriately selecting a delay equalizer. [Claim 4] A facsimile control signal is executed between the facsimile device of the other party connected via a public line, and the image data is divided into predetermined blocks, and each block is transmitted and received. In a facsimile machine that performs transmission and reception using HDLC, performs error checking using the ECM communication method, and retransmits the image data of the block in which the error occurred, the setting values for correcting the passband characteristics of the transmission path are different. Two or more cable equalizers, at least two or more delay equalizers with different setting values for correcting group delay distortion of the transmission path, and image data of a block in which an error has occurred during transmission and reception of image data in units of blocks. 1. A facsimile apparatus comprising: selection means for appropriately selecting the cable equalizer and the delay equalizer each time a retransmission is made.