JPH05244378A - Facsimile communication method - Google Patents

Abstract

PURPOSE:To improve transmission speed at the time of using a transmission method having an error restoring function by lowering a reference level for judging line conditions to be normal when an error correction mode(ECM) is used. CONSTITUTION:A signal processing part 18 at a transmission side set time Q required for time up in a timer to 0.8 second when the ECM mode is used and to 1.0 second unless the ECM mode is used. At the time of the ECM mode, picture data is divided into units having a prescribed size, transmitted and re-transmitted when a transmission error occurs in the respective units. The transmission side transmits a training signal to a reception side. By receiving this, the reception side resets the timer inside the signal processing part 18. When the reception side continuously receives '0' signal till the timer measures Q second line conditions are judged to be normal so that copy data reception starts. When training is completed before the time measures Q second, the signal processing part 18 at the transmission side decreases communication speed and executes training communication again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a facsimile communication method, and more particularly to improving the transmission speed thereof.

[0002]

2. Description of the Related Art FIG. 2 shows a block diagram of a general facsimile apparatus. The signal from the line 4 is taken into the signal processing unit 18 via the modem 14. This signal is decoded by the encoding / decoding circuit unit 12, and the print output unit 2
It is printed at 6. On the other hand, when transmitting, a document is read from the image reading unit 28 and is encoded by the encoding / decoding circuit unit 12. The coded data is processed by the signal processing unit 18 into the modem 14 and the line control unit 6.
Is sent to the line 4 via. The facsimile communication is performed as described above.

In facsimile communication, a method is employed in which training communication is performed before transmission of image data to determine the line status (referred to as TCF check) and the transmission speed is determined. Hereafter, regarding this TCF check,
The operation will be described with reference to the operation flowchart on the receiving side (FIG. 3).

First, the transmission speed is set to 96 on both the transmitting side and the receiving side.
Set to 00 bps (step S1). The transmitting side sends a training start signal to the receiving side. In response to this, the receiving side resets the timer in the signal processing unit 18 (step S2). The transmitting side continues to transmit "0" for 1.5 seconds after the start signal. If the receiving side continues to receive "0" until the timer measures 1 second (step S5), the line status is good and the CFR signal is sent (step S5).
9), and move to image data reception (step S10).

However, when "1" is received on the way, the timer is reset (step S4). Therefore, if "0" is not continuously received for 1 second, the process does not shift to image data reception. When the training is finished before the timer measures 1 second (step S6), the FTT signal is sent (step S7) and the communication speed is reduced to 7200bps (step S8). And again, at this baud rate, step
Execute S2 and below. By reducing the communication speed, the number of errors decreases, and if the timer measures 1 second, the process proceeds to image data reception (step S10). Even if the communication speed is reduced, if "0" cannot be continuously received for 1 second (step S6), the FTT signal is transmitted (step S7),
Furthermore, the communication speed is reduced to 4800 bps (step S8). The same process is repeated thereafter, and if the line condition is bad, the minimum communication speed is reduced to 2400bps.

As described above, the TCF check is performed, and when the line condition is bad, the communication speed is reduced to perform the transmission. As a result, reliable communication can be performed even if the line condition is poor.

[0007]

However, the conventional facsimile communication method as described above has the following problems.

Recently, in facsimile communication, an error correction mode (ECM) is often used to transmit data accurately. This ECM is
One frame consists of 256-bit data and 25
Transmission is performed by using 6 frames as one block. After transmission, a frame in which an error has occurred is transmitted from the receiving side to the transmitting side by parity check and the like, and only the frame in error is retransmitted. As a result, data can be transmitted accurately.

By the way, in the conventional communication method, E
Regardless of whether or not the CM is used, the criterion for the TCF check is constant. Since there is an error recovery function when using the ECM, some transmission errors are allowed. However, there is a problem that the communication speed becomes slower because the judgment is performed more than necessary.

It is an object of the present invention to solve the above problems and to provide a facsimile communication method capable of improving the transmission speed when a transmission method having an error recovery function is used.

[0011]

In the facsimile communication method according to the present invention, image data is divided into units having a predetermined size and transmitted, and when a transmission error occurs in each unit, it is retransmitted. In the case of transmission, it is characterized by lowering the criterion for judging the line condition in training communication as good.

[0012]

When the method of dividing the image data into units having a predetermined size and transmitting them and retransmitting when a transmission error occurs in each unit is used, the criterion for judging that the line condition is good is lowered. ing. This can prevent a decrease in communication speed.

[0013]

1 is a flow chart of a facsimile communication method according to an embodiment of the present invention. The hardware configuration is the same as in FIG.

First, the signal processor 18 sets the transmission mode to E.
It is determined whether the CM mode is set (step S1). E
In the CM mode, the timer time-up time Q is set to 0.
8 seconds (step S2), and if not in ECM mode, the timer time-up time Q is 1.0 second (step S2).
3).

Next, the transmission speed is set to 96 on both the transmitting side and the receiving side.
Set to 00 bps (step S4). The transmitting side sends the training signal to the receiving side. In response to this, the receiving side resets the timer in the signal processing unit 18 (step S
Five). The transmitting side continues to transmit "0" for 1.5 seconds after the alignment signal. If the receiving side continues to receive "0" until the timer measures Q seconds (step S8), the line status is good and the CFR is transmitted (step S12).
The process moves to image data reception (step S13). In the ECM mode, in step S8, the timer times out at 0.8 seconds. If it is not in ECM mode, the time is up in 1.0 seconds. That is, in the case of the ECM mode, the criterion for judging the line status as good is low.

If "1" is received on the way,
Reset the timer (step S7). Therefore, if "0" is not continuously received for Q seconds, the process does not shift to image data reception. If the training ends while the timer does not measure Q seconds (step S9), the signal processing unit 18
TT is transmitted (step S10), and the communication speed is reduced to 7200 bps (step S11). Then, step S5 and thereafter are executed again at this communication speed. By reducing the communication speed, the number of errors decreases, and if the timer measures Q seconds, the process proceeds to image data reception (step S13). Even if the communication speed is reduced, if "0" cannot be continuously received for Q seconds (step S9), FTT is transmitted (step S1).
0), and further reduce the communication speed to 4800bps (step S1
1). The same process is repeated thereafter, and if the line condition is bad, the minimum communication speed is reduced to 2400bps. As described above, in the case of ECM, the criterion for judging the line status to be good is lowered by shortening the time-up time of the timer. Since the ECM has an automatic error recovery function, accurate communication can be performed even if the line condition is slightly poor. Therefore, according to this embodiment, the EC
In M, there is no risk of unnecessarily decreasing the speed.

In the above embodiment, the ECM time-up time is set to 0.8 seconds, but it can be set to an appropriate time depending on the case.

[0018]

According to the facsimile communication method of the present invention, when a method is used in which image data is divided into units having a predetermined size and transmitted, and when a transmission error occurs in each unit, retransmission is performed, The standard for judging the line status as good is set low. As a result, in the communication method having the error correction function, it is possible to prevent a decrease in communication speed due to line conditions.

[Brief description of drawings]

FIG. 1 is a diagram showing a flowchart of a facsimile communication method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a block diagram of a general facsimile apparatus.

FIG. 3 is a diagram showing a flowchart of a conventional facsimile communication method.

[Explanation of symbols]

 2 ... Facsimile device 4 ... Line 18 ... Signal processing unit

Claims (1)

[Claims] 1. A communication method in which training communication is performed before image data is transmitted to check whether the line condition is good, and when the line condition is poor, the image data is transmitted in a predetermined size at a transmission speed. When transmitting by dividing into units with a certain length and transmitting by a method in which a transmission error occurs in each unit, lower the criterion for judging the line condition in training communication as good Facsimile communication method.