JPH0681236B2 - Facsimile communication method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a data communication system for communicating images, character codes, and the like.

<Prior Art> Conventionally, in the case of a facsimile apparatus using this type of data communication method, the echo suppressor function is stopped by transmitting the called station identification signal (CED) in order to use the telephone line in full duplex. Was there. However, even if the echo suppressor function is stopped once, if the signal is interrupted for a certain time or longer, the stop is canceled.

For example, if it takes a long time for the transmitting operator to press the transmission start button after opening the CED, the response signal from the transmitting side to the initial initial identification signal (NSF / CSI / DIS) from the receiving side Cannot send NSS / TSI / DCS signals. Therefore, the receiving side retransmits the initial identification signal again, but at this time, there is a signal break for a long time between the first and second initial identification signals, and the suspension of the echo suppressor function is released.

Further, even when the receiving side cannot receive the DCS group signal or the inter-page signal such as the EOP signal, the MPS signal and the EOM signal, the suspension of the echo suppressor function is canceled.

When the suspension of the echo suppressor function is released in this way, full-duplex communication becomes impossible. Therefore, continuous error retransmission using the line in full duplex is impossible.

<Purpose> In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a data signal system that can necessarily stop the echo suppressor function during actual data communication.

<Example> An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the output timing of the output signals of the transmission side and the reception side in the facsimile transmission system of this embodiment.

First, when receiving the calling signal CI from the transmitting side, the receiving side outputs the called station identification signal CED. Then, after that, the initial identification signal NSF indicating the non-standard function is used to notify the transmitter side of whether or not there is a function of performing continuous error retransmission. This has the error resending function when one of the bit strings of the facsimile information field FIF of NSF, for example, the 50th bit is set to 1, and does not have it when it is 0. The receiving side also sends a called station identification binary signal CSI and a digital identification signal DIS.

On the other hand, the transmitter side determines whether the operator has selected the error retransmission function and whether the receiver side has the function. Here, if the operator selects the function and the receiving side has the function, the F of the non-standard device setting signal NSS is selected.
The 50th bit of IF is transmitted as 1. In addition, the transmitting station identification signal TSI and the digital command signal DCS are transmitted. Receiver is NS
Whether or not the function is used can be determined by S.

When the transmitter receives the reception preparation confirmation signal CFR from the receiver, it sends a 2100Hz tonal signal as the echo suppressor stop tone EST for 1 second when performing the error resending function, and then the signal disconnection of 100mS or less. Alternatively, the training signal and the message signal (image signal) are transmitted without disconnecting the signal. Therefore, it becomes possible to use the line in full-duplex mode while sending a message, continuous error resending is performed, and if some image signals cannot be received at the receiving side during message communication, the error part Can be transmitted to the sender.

When the communication for one page is completed and the next page is reached,
The NSS signal is transmitted, and in this case also, the EST is transmitted immediately before the training transmission leading to the transmission of the message. When the transmission of all pages is completed, the transmission side sends the line open signal DC.
Send N and terminate communication.

FIG. 2 shows, as a block diagram, an embodiment of the transmitter side of the facsimile apparatus which executes the procedure as shown in FIG.

In FIG. 2, numeral 2 denotes a telephone network used for data communication, so that the terminal of the line is connected to control connection of the telephone switching network, switch to a data communication path, and maintain a loop. Network control unit NCU (Network Control Uni
t). The signal line 2a is a telephone line. The NCU 2 inputs the signal of the signal line 28a, and if the signal level is "φ", connects the telephone line to the telephone side, that is, the signal line 2a to the signal line 2b. When the signal on the signal line 28a is input and the signal level is "1", the telephone line is connected to the facsimile machine side, that is, the signal line 2a is connected to the signal line 2c.
In a normal state, the telephone line is connected to the telephone side.

Reference numeral 4 is a telephone.

Reference numeral 6 is a hybrid circuit for separating a transmission system signal and a reception system signal. That is, the transmission signal of the signal line 18a,
It is sent to the telephone line through the signal line 2c and the NCU2. Further, the signal sent from the other party is output to the signal line 6a after passing through the NCU2, the signal line 2c.

Reference numeral 8 denotes a reading circuit, which sequentially reads image signals for one line in the main scanning direction from a transmission document and creates a signal string representing binary values of white and black. It is composed of an imaging device such as CCD (charge coupled device) and an optical system. The binarized signal sequence of white and black is
It is output to the signal line 8a.

Reference numeral 10 is a circuit that inputs the binarized data output to the signal line 8a and performs encoding. The encoding circuit 10 has a memory that only performs retransmission. When the signal line 28d is at the signal level "φ", normal transmission encoding is performed. When the signal line 28d is at the signal level "1", coding is performed by continuous error retransmission. When the Count error error retransmission mode is selected, the following control is performed. When the signal level of the signal line 28b becomes "1", the image transmission is interrupted. And
When the signal line 28d reaches the signal level “φ”, the retransmission start line output to the signal line 28c is input and the retransmission from this line is performed. Data that has been encoded (MH (Modified Huffman) encoding or MR (Modified Read) encoding) is output to the signal line 10a.

Reference numeral 12 is a modulator that performs modulation based on the well-known CCITT recommendation V27ter (differential phase modulation) or V29 (quadrature modulation). The modulator 12 receives the signal on the signal line 10a, modulates the signal, and outputs the modulated data to the signal line 12a.

Reference numeral 14 is a modulator that performs modulation based on the well-known CCITT recommendation V21. The modulator 14 inputs the procedure signal of the signal line 28e,
It modulates and outputs the modulated data to the signal line 14a. In addition, the 50th bit information of the FIF of the NSS signal is output to the signal line 28f.

Reference numeral 16 is a circuit for generating an echo suppressor function stop tone on the signal line 16a when a pulse is generated on the signal line 28g. In the present embodiment, a signal of 2100 Hz for 1 second is considered as the tone for stopping the echo suppressor function. Reference numeral 16 generates a pulse on the signal line 16b when the transmission of the echo suppressor function stop tone is completed.

Reference numeral 18 is an adder circuit that inputs signals from the signal lines 12a, 14a, 16a and outputs the addition result to the signal line 18a.

Reference numeral 20 is a demodulator that performs demodulation based on the well-known CCITT recommendation V21. The demodulator 20 receives the signal on the signal line 6a, performs V21 demodulation, and outputs the demodulated data to the signal line 20b. Also,
The demodulator 20 sends the information of the 50th bit of FIF of the NSF signal to the signal line.
Output to 20a.

When a receiving error is detected on the other side during data communication, the other side facsimile machine sends a NACK signal. Reference numeral 22 is a circuit for generating a pulse on the signal line 22a when detecting the NACK signal.

Reference numeral 24 is a circuit that detects the retransmission start line number that is sent after the NACK signal and outputs the line number to the signal line 24a.

Reference numeral 26 is a circuit for detecting whether or not the operator has selected the continuous error retransmission mode. 26 indicates that when the operator does not select the continuous error retransmission mode,
A signal having a signal level “φ” is output to the signal line 26a. Further, 26 outputs a signal of signal level "1" to the signal line 26a when the operator selects the continuous error retransmission mode.

28 is a control circuit that performs the control described below. When the operator on the transmitter side does not select continuous error retransmission, or when the receiver does not have the function of performing continuous error retransmission, normal transmission is performed. At this time, the echo suppressor function stop tone is not sent immediately before sending the image signal. If the receiver has the function to perform continuous error retransmission and the operator on the transmitter side selects continuous error retransmission,
us Transmit in error resend mode. At this time, the echo suppressor function stop tone is transmitted immediately before the image signal is transmitted. This tone is sent immediately before the image signal even when retransmitting. This allows full-duplex operation even on international lines.

A control flow chart of the control circuit 28 of FIG. 2 is shown in FIG.

In FIG. 3, a step S50 connects the telephone line to the telephone side and sends out a calling signal CI. Then, CED is detected in S52, and when the start button is pressed, the telephone line is connected to the hybrid circuit side in S54.

Then, in S56, the other side NSF is received, and it is determined in S58 whether the receiving side has a continuous error retransmission function.
If there is a function, it is determined in S60 whether the operator has selected the error retransmission function. If either S58 or S60 is "none", the normal mode is selected in S61 and the signal lines 28b, 28d, 28f
The signal level "0" is output to.

On the other hand, when both are present, the error retransmission mode is selected in S62, and the signal level "1" is output to the signal lines 28d and 28f.

Therefore, in the pre-procedure of S64, the NSS signal with the 50th bit of FIF set to "1" is transmitted. If a CFR is detected during the pre-procedure of S64, the echo suppressor stop tone E is detected in S66.
ST is sent, and then a training signal message (image signal) is sent without signal loss of 100 mS or less (S68, S70).

Therefore, the line is always used in full duplex during message transmission in error resend mode. When the NACK signal is received from the receiving side during message transmission, the line NO signal of the retransmission start following the NACK signal is detected in S74, and when the preparation for retransmission is completed in S76, the process returns to S66 again, and the EST, training, and message are transmitted. Send in order.

When the end of the message of one page is detected in S78, S80
The presence / absence of the next page is judged with. If the next page is present, the process returns to S58 to repeat the above operation. If there is no next page, DCN is sent and the operation ends.

On the other hand, if the normal mode is selected in step S61, S
In the pre-procedure of step 82, the NSS signal in which the 50th bit of the FIF is set to "0" is transmitted, and thereafter, transmission in the normal mode is performed without transmitting EST.

As described above, in the facsimile apparatus of this embodiment, when performing continuous error retransmission, the tone for stopping the echo suppressor function is always transmitted immediately before the transmission of the image signal data, so that the signal of 100 mS or more is transmitted during the procedure. Even if a disconnection occurs, the line can be used twice during actual data communication.

This is particularly advantageous for international communication, which requires a long time for transmission and has poor line quality, or remote communication.

In this embodiment, the stop tone is sent immediately before the training signal before the image signal, but it may be sent before the image signal in which a signal interruption of 100 mS or more cannot occur.

<Effect> As described above, according to the present invention, even if the signal is interrupted during the procedure,
The line can be used in full duplex without exception during the actual data communication period, and continuous error retransmission can be reliably executed. It is particularly advantageous for international communication or remote communication where signal disconnection during the procedure is likely to occur.

[Brief description of drawings]

FIG. 1 is a signal output timing diagram of a transmitting side and a receiving side in the communication system of this embodiment, FIG. 2 is a circuit block diagram of a facsimile transmitting apparatus of this embodiment, and FIG. 3 is control of the control circuit of FIG. It is a flow chart. In the figure, 2 is an NCU, 4 is a telephone, 6 is a hybrid circuit, 8 is a reading circuit, 10 is an encoding circuit, 12 is a V27ter or V29 modulator, 14 is a V21 modulator, and 16 is an echo suppressor-stop tone generation. Reference numeral 18 is an adder circuit, 20 is a V21 demodulator, 22 is a NACK signal detection circuit, 24 is a retransmission start line detection circuit, 26 is a continuous error retransmission selection detection circuit, and 28 is a control circuit.

Claims (1)

[Claims] 1. A facsimile communication method for a facsimile apparatus, comprising: a modem capable of full-duplex communication; and a stop signal transmitting means for transmitting a stop signal for stopping an echo suppressor installed on a public line. When shifting from half-duplex communication to full-duplex communication in which half-duplex communication and full-duplex communication are mixed in one communication,
A facsimile communication method, characterized in that the echo suppressor is stopped by transmitting the stop signal immediately before a signal required for processing of the modem itself.