JPH01194652A - Facsimile communicating system - Google Patents

Abstract

PURPOSE:To suitably communicate according to the quality of a line by selecting one of a standard transmission control procedure or an original transmission control procedure based on the result of the exchanging test of a control signal with the use of a backward channel. CONSTITUTION:A CPU 1 controls an NCU 8, and calls desired opposite facsimile equipment. When the opposite facsimile equipment responds, and returns control signals NFS and DIS by means of the transmission control procedure of a CCITT advice G3, whether or not the signal is normally received is checked, when the signal is normally received, whether or not the opposite facsimile equipment has the original procedure is detected based on the received control signals NFS and DIS, and when it does not have the original procedure, a process shifts to the transmission procedure of G3. When the opposite side facsimile equipment has the original procedure, the CPU 1 transmits a control signal NSS, notifies the function of the self equipment, and successively controls the equipment so as to send a training checking signal TCF.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) This invention relates to a facsimile communication system used by a facsimile machine.

(Prior art) In facsimile communication, CCITT recommendations, T2O
G3 facsimile transmission control procedure (half-duplex communication)
is often used. On the other hand, due to unique procedures such as error retransmission procedures for image signals, facsimiles are capable of transmitting and receiving low-speed digital signals and single tones by frequency-dividing the low or high frequency band of the line and using it as a backward channel. Devices are also known. If a facsimile machine capable of executing such unique procedures is connected to a line with poor line quality, CCITT Recommendation V29. V27ter, V2
1(7) A situation arises in which G3 control signals such as modem signals pass through, but backward channel control signals do not pass through.

In such a case, as shown in FIG. 4, in conventional facsimile communication, communication is attempted at the same communication speed up to a specified number of times (for example, three times) using a backward channel (as indicated by BW-CFR). ), if communication was impossible, it was determined that it was a communication error and the line was disconnected. According to this method, when communicating with a facsimile device that is connected to a line with poor line quality (such as not being able to receive data on the backward channel), a communication error is always assumed, and communication itself becomes permanently impossible. There was a problem with it getting stuck.

Therefore, it is conceivable to set the functions of the facsimile machine so as not to use the proprietary procedure, but this poses the problem that the proprietary procedure cannot be used even if the line quality is good.

(Problem to be solved by the invention) As mentioned above, according to the conventional facsimile communication system,
Using a backward channel, communication is attempted at the same communication speed up to a specified number of times, and if communication is not possible, the line is disconnected, so if a line with poor line quality is used, communication may be permanently disabled. There was a drawback. The only way to deal with this problem is to disable the use of the proprietary procedure by setting the function, but this has resulted in the problem that the proprietary procedure cannot be used even if the line quality is good.

The present invention was made in view of the shortcomings of the conventional facsimile communication system, and its purpose is to prevent communication from being impossible when using a line with poor line quality, and to improve the quality of the line. It is an object of the present invention to provide a facsimile communication method that can use an original procedure in good cases.

``Configuration of the Invention (Means for Solving the Problems) In the present invention, control signals are transmitted and received using half-duplex communication according to a standard transmission control procedure, and control signals according to a unique transmission control procedure are transmitted and received using a backward channel. In a facsimile system capable of performing a transmission/reception test using the backward channel, the test means performs a transmission/reception test of control signals using the backward channel, and the standard transmission control procedure or the original transmission control is performed based on the result of the transmission/reception test performed by the testing means. The facsimile communication system is provided with a selection means for selecting one of the two procedures, and the facsimile communication system is configured to execute the standard transmission control procedure when the unique transmission control procedure is impossible.

(Operation) According to the above configuration, either the standard transmission control procedure or the original transmission control procedure is always selected based on the result of the transmission/reception test, and appropriate communication can be performed according to the quality of the line.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a facsimile machine that employs the method of the present invention. In the figure, 1 is a CP that controls the entire device.
U,2 indicates a main memory in which programs used by the CPU are stored and data may also be stored. A bus 3 extends from the cpui, and includes a reading unit 4 that obtains an image signal from the original, a recording unit 5 that performs recording and output based on the image signal, and an encoding/decoding unit that performs encoding compression or decoding expansion of the image signal. 6,
Connected to the bus 3 are a backward channel modem 7 that can send and receive control signals using low-speed digital signals using the backward channel, and an NCU 3 that starts and restores the network. The backward channel above is the NCU
The line 9 connected to 3 is a telephone line and the used band is 0.
3 to 3.4 Kl-(If Z, it is created by frequency-dividing the low-frequency side or the high-frequency side.

The CPU 1 of the facsimile machine described above operates based on the program shown in the flowchart of FIG. Here, it functions as a transmitter for outgoing calls and image signals, but it can also function as a receiver for incoming calls and image signals as described below.

The operation will be explained below. The CPU 1 controls the NCU 3 to send a dial signal in order to call a desired destination facsimile machine (101). In response, the other party's facsimile machine responds by sending back control signals (commands) NSF and DIS based on the transmission control procedure of CCITT recommendation G3, which are received via NCUB and modem 7 (102).

Here, check whether this control signal was received normally (103), and if an error occurs three or more times (104)
The process ends as the line is disconnected (114). On the other hand, if the facsimile device is normally received, it is detected based on the received control signals NSF and DIS whether or not the other party's facsimile device has a unique procedure (105), and if it does not have a unique procedure, it shifts to the G3 transmission procedure (105). 113). If it is detected in step 105 that the other party's facsimile machine has its own procedure, the CPLll sends a control signal NSS to notify its own functions (106), and then sends a training check signal TCP. (107). On the other hand, the other party's facsimile machine receives the control signal @NSS training check signal TCP and, if it determines that communication is possible, transmits the test signal BW-0FR using the backward channel. This test signal BW-CFR is
LI8, CPU1 imports via modem 7 (108)
, determine whether or not the reception was successful (109) CPL
If ll can be received normally, test signal BW-C
To detect whether it is FR or not 110), test signal @8W
- If it detects that it is not a CFR, it returns to step 108 and performs the detection again. If it detects that it is a test signal BW-CFR, it transmits the picture signal @ (PIX) according to its own procedure (111), and then disconnects the line. Do (120). In addition, in step 109, if the CPLJ 1 is unable to receive normally, the CPLJ 1 proceeds to step 112 and detects whether the error has occurred three or more times, and if it is less than three, returns to step 106; If so, execute the transmission control procedure using G3 (113).

In the above, the main memory 1 stores an operation program for the unique procedure used in step 111 and an operation program for the G3 transmission control procedure used in step 113, and the CPU 1 operates based on these programs.

FIG. 3 shows an example of an operation procedure when a facsimile machine FAX-A having such a configuration communicates with a facsimile machine FAX-8 having a similar configuration. The facsimile machine FAX-8 becomes the calling sender. In this example, the test signal @ B W -CFR was sent three times (indicated by ■ to ■), but could not be received normally, and the transition to the transmission control procedure of 03 occurred at time IV.

As described above, in this embodiment, when the number of times that the test signal BW-CFR is not properly received in half-duplex communication using the backward channel is three or more times, the process shifts to the G3 transmission control procedure. It is convenient because communication is possible even when the line quality is poor, and when the line quality is good, it is possible to request retransmission of an erroneous image signal using a unique procedure using a backward channel.

In this embodiment, the modem 7 is used for the backward channel, but the modem 7 is equipped with, for example, a tone generator/receiver capable of transmitting and receiving a single tone, and the test signal is transmitted to the backward channel. It is also possible to send and receive the information using . Also, if the backward channel test signal cannot be detected within a predetermined time, the G
3 transmission control procedure. Furthermore, the unique procedure may be executed only when both the backward channel test signal and the 300 bps modem signal can be received.

[Effects of the Invention] As explained above, according to the present invention, a transmission/reception test is performed using a backward channel, and based on the result, either the standard facsimile transmission control procedure or the original procedure is always selected. Appropriate communication depending on line quality can always be performed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a facsimile machine that employs an embodiment of the present invention, Fig. 2 is a flow chart for explaining the operation of the facsimile machine of Fig. 1, and Fig. 3 is an operational procedure according to the communication method of the present invention. FIG. 4 is a diagram showing an example of an operation procedure according to a conventional facsimile communication system. 1...CPLJ 2...Main memory 3...
Bus 4...Reading section 5...Recording section
6... Encoding/decoding unit 7... Modem 8...
・NCU9...Line agent Patent attorney Nori Chika Ken Yudo Sanno - Figure 1 Figure 3

Claims (1)

[Claims] In a facsimile system capable of transmitting and receiving control signals using half-duplex communication according to a standard transmission control procedure, and also transmitting and receiving control signals according to a unique transmission control procedure using a backward channel, a control signal using the backward channel is provided. and a selection procedure for selecting either the standard transmission control procedure or the original transmission control procedure based on the result of the transmission and reception test conducted by the test means, and the original transmission control procedure A facsimile communication system characterized in that the standard transmission control procedure is executed when the standard transmission control procedure is impossible.