JPH0666869B2 - Fax machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a facsimile apparatus that performs error retransmission.

[Prior Art] In an existing facsimile apparatus, if an error occurs during communication of image data, the facsimile apparatus on the receiving side detects an error in the image data, and the facsimile apparatus on the receiving side transmits based on the detection result. An error resend request signal was sent to the facsimile machine on the side. Then, the image data is retransmitted from the facsimile apparatus on the transmitting side which has received the error resending request signal.

However, an error during communication occurs not only during communication of image data but also during communication of a procedure signal or the like. Normal,
When the communication of the procedure signal or the like fails, the procedure signal is communicated again, so that the communication itself does not end in error. However, if an error occurs in the training signal transmitted immediately before the image data, the conventional facsimile apparatus ends the communication with an error.

This situation will be described with reference to FIG. The signal names used in Fig. 1 are defined in CCITT Recommendation T.30.

In FIG. 1, the transmitting side transmits the training / TCF signal after the NSS / TSI / DCS signal, and the receiving side transmits the CFR signal. Next, the transmitting side transmits the training signal after receiving the CFR signal. However, communication of this training signal has failed. Here, for convenience, a training signal transmitted after the CFR signal (a training signal transmitted immediately before the image data) is defined as a "retraining signal".

As shown in FIG. 1, conventionally, if the communication of the retraining signal fails, the receiver side ends the communication in error after 10 seconds, while the transmitter side ends the transmission of the image data of one page. After that, since there is no response from the receiver side, the communication ends in error.

As described above, conventionally, if retraining fails, as shown in FIG. 1, useless image data is transmitted on the transmitting side, and during that time, the transmitting side cannot perform other communication. .

[Object] In view of the above points, it is an object of the present invention to provide a facsimile apparatus capable of error retransmission, and capable of preventing the communication from ending in error when communication of a retraining signal fails. .

[Embodiment] FIG. 2 shows an outline of the operation of this embodiment.

In FIG. 2, as in FIG. 1, communication of the retraining signal has failed. In the present embodiment, when the receiving side detects that the retraining signal has not been received correctly, the receiving side suspends the transmission of the image data of the transmitting side by the full duplex operation procedure signal PIS. Then, the receiving side requests the transmitting side to retransmit the image data from the beginning of one page using NSF. Upon receiving this, the transmitting side transmits the retraining signal and then retransmits the image data from the beginning of one page.

The above operation is the outline of the operation of this embodiment.

FIG. 3 is a block diagram showing the configuration of the facsimile apparatus of this embodiment.

40 is a network control unit (NCU). 40a indicates a telephone line.

42 is a hybrid circuit. The signal transmitted to the signal line 54a passes through the signal line 40b and the network control device 40,
It is sent to the telephone line 40a. The signal sent from the facsimile machine on the other side is output to the signal line 42a after passing through the network control signal 40.

Reference numeral 44 is a circuit that inputs the signal of the signal line 42a and detects whether or not there is a signal. The circuit 44 outputs a signal of signal level "1" to the signal line 44a when receiving a signal of -43dbm or more, and when receiving a signal of less than -43dbm,
A signal having a signal level "0" is output to the signal line 44a.

46 is a demodulator. The demodulator 46 receives the signal on the signal line 42a, demodulates it, and outputs the demodulated data to the signal line 46a.

50 is NS on signal line 50a when a pulse occurs on signal line 66b.
This is the circuit that sends out the F signal. The signal line 66a includes a signal line 58
A value obtained by adding 1 to the value of the line number output to a is output. The NSF signal contains the line number. The value output to the signal line 66a is set to this line number. The NSF signal transmission circuit 50 generates a pulse on the signal line 50b when the transmission of the NSF signal is completed.

Reference numeral 52 is a circuit for transmitting a retransmission request signal (a PIS signal is used in this embodiment). The circuit 52 is a circuit that sends out a PIS signal (a 462 Hz signal for 3 seconds) to the signal line 52a when a pulse occurs in the signal line 66c. The circuit 52 generates a pulse on the signal line 52b when the transmission of the PIS signal is completed.

Reference numeral 54 is an adder circuit that inputs the signal of the signal line 50a and the signal of the signal line 52a and outputs the addition result to the signal line 54a.

Reference numeral 56 is a FIFO memory used to store the demodulated data obtained by demodulating the data sent from the facsimile machine on the other side by the demodulator 46. FIFO memory 56 uses signal line 66e
The stored demodulated data is stored in the signal line 56a and is output to the signal line 56a.

Reference numeral 58 is a line number storage memory for storing the latest line number of correctly received data. The line number storage memory 58 stores the latest line number input via the signal line 58a by the write control of the control circuit 66, and outputs the stored latest line number to the signal line 58a by the read control of the control circuit 66. To do.

Reference numeral 60 is a decoder for decoding the demodulated data stored in the FIFO memory. The decoder 60 decodes the demodulated data input from the signal line 60a and outputs the decoded data obtained by decoding the demodulated data to the signal line 60a.

64 is a recording device. The recording device 64 inputs the decoded data decoded by the demodulator 60 from the signal line 66n and records it on the recording paper.

Reference numeral 66 denotes a control circuit, which performs control described later.

FIG. 4 is an explanation of the training signal detection used in this embodiment.

FIG. 4 (1) shows a signal on the line. FIG. 2B is a waveform of a signal indicating whether or not there is a signal on the line. This signal is called SED (Signal Energy Detect). This signal is an output signal of the signal presence / absence detection circuit 44 shown in FIG. 3, and becomes high level when it is detected that there is a signal on the line. (3) of FIG. 4 is a waveform of the carrier detect (CD) signal indicating whether or not the valid data transmitted at the transmission speed for transmitting the image data is detected. This signal is a signal that becomes high level when valid data is detected as a result of decoding the demodulated data demodulated by the demodulator 46 in FIG. 3 by the control circuit 66, and is generated inside the control circuit 66. Signal to do.

By looking at (1) to (3) in FIG. 4, it can be seen that the period (Tr) in which the SED is at the high level and the CD is in the low level is the period during which the training signal is being received (2400bi
Tr = 1158ms at t / s, Tr = 923m at 4800bit / s
s).

FIG. 5 is a flowchart of the training signal detection operation of the control circuit 66 shown in FIG.

Step S1000 in FIG. 5 represents the start of detection of the training signal.

In step S1002, the timer T2 for determining the failure to receive the training signal is set to 10 seconds.

In step S1004, it is determined whether SED = 1 continuously for 20 milliseconds while determining whether the timer T2 times out. At this time, if the timer T2 times out, the process proceeds to step S1012. If SED = 1 continuously for 20 milliseconds (if the head portion of the training signal is received), the process proceeds to step S1006.

In step S1006, while judging whether or not the timer T2 times out, for a millisecond (a = 700 ms at 2400 bit / s, a = 500 ms at 4800 bit / s) continuously C
It is determined whether D = 0. At this time, if the timer T2 times out, the process proceeds to step S1012. If CD = 0 continuously for a millisecond (if a training signal is received), the process proceeds to step S1008.

In step S1008, it is determined whether CD = 1 for 20 milliseconds continuously while determining whether the timer T2 times out. At this time, if the timer T2 times out, the process proceeds to step S1012. If CD = 1 continuously for 20 milliseconds (if the TCF following the training signal or the head portion of the image data is received), step S101.
Go to 0.

In step S1010, it is determined that the training signal has been successfully received. Then, following step S1010, the control circuit 66 transmits a CFR signal if the received signal is a training / TCF signal, and transmits a CFR signal if the received signal is a training (retraining) / image data signal. Receive.

Step S1012 represents a training signal reception error. Then, following step S1012, the control circuit 66
Sends an FTT signal if the received error signal is a training / TCF signal, and sends an error resend request signal if the received signal is training (retraining) / image data.

FIG. 6 is a flow chart of the receiving operation of this embodiment, and shows the operation of the control circuit 66 of FIG. FIG. 6 is the same as the conventional operation, except for the image receiving process of step S5010 (details will be described later).

In FIG. 6, after the call is received, NSF / CSI / DIS is transmitted in step S5000 while waiting for NSS / TSI / DCS reception in step S5002.

If NSS / TSI / DCS is received in step S5002, step
Receive training / TCF on S5004. The details of receiving this training signal are as described above.

If the training / TCF is received in step S5004, it is determined in step S5006 whether the training / TCF was successfully received. If the training / TCF is successfully received, CFR is received in step S5008.
Is sent and if it is not received properly, F is returned in step S5018.
Send TT.

After sending the FTT in step S5018, NSS in step S5020.
Wait for / TSI / DCS reception, and if received, step S5004
Go to.

After transmitting the CFR in step S5008, image reception processing is performed in step S5010. The image receiving process in step S5010 will be described later with reference to FIG.

After the image receiving process in step S5010, the post-procedure is performed in step S5012.

In step S5014, EOM is performed in the post-procedure of step S5012.
Determine which signal of / MPS / EOP is received. EO
If M is received, the process proceeds to step S5000, and if MPS is received, the process proceeds to step S5010. If the EOP is received, the remaining post-procedure is performed in step S5016, and the reception ends.

FIG. 7 shows a flowchart of the image receiving process which is a feature of this embodiment.

This flowchart is executed by the control circuit 66 shown in FIG.

Step S1036 represents the start of image reception.

In step S1038, it is determined whether the retraining signal has been successfully received. As described above, the success of the retraining signal is determined by the confirmation of SED = 1, the confirmation of CD = 0 (about half the retraining time), and the confirmation of CD = 1 correctly. If the retraining signal is successfully received within 3.5 seconds in step S1038, step
If the reception of the retraining signal is not successful within 3.5 seconds in S1040, it is determined that the reception of the retraining signal has failed, and the process proceeds to step S1078.

Normally, the reception of the retraining signal is completed within 3.5 seconds, so the time from the start of the reception of the retraining signal to the determination that the reception of the retraining signal has failed is set to 3.5 seconds.

In step S1040, the counter that counts the number of NSF transmissions is cleared. This counter is a counter that counts the number of times of requesting the error retransmission again to the transmitting side when the error retransmission using NSF is not successful.

After clearing the counter in step S1040, image reception is performed.

Then, in step S1041, it is detected whether or not the image data has an error, and in step S1046, image reception is performed until RTC is detected.

If RTC is detected in step S1046, post-procedure is executed in step S1048. This step S1048 is step S5012 in FIG.

If it is detected in step S1041 that the received image data has an error, in step S1056 the PIS signal is sent in full-duplex operation to suspend the transmission of image data to the transmitting side.

In step S1060, the transmission side interrupts the transmission of image data,
Make sure there is no signal on the line. If the sender has stopped transmitting image data, there is no signal on the line.
SED = 1 because D = 0 and there is a signal on the line unless the transmitting side has interrupted the transmission of image data.

If SED = 1 in step S1060 and it is determined that the transmission side has not interrupted the transmission of image data, step S1
In 062, in order to interrupt the sending of image data to the sending side,
The PIS signal is transmitted again, the DCN signal is transmitted in step S1068, and the communication ends in error in step S1070.

If SED = 0 in step S1060, the transmission side interrupts the transmission of image data and it is determined that there is no signal on the line, the NSF signal in which the retransmission start line number is set is transmitted in step S1074. This retransmission start line member is obtained from the line number stored in the line number storage memory shown in FIG.
If the reception of the retraining signal at the start of receiving the image data of one page fails, the first retransmission start line is set.
Set as a line. That is, when the retraining fails, the transmitter is requested to retransmit all the image data. In response to the error retransmission request, the transmitting side transmits the retraining signal again, and then transmits the image data from the line number for which the retransmission request is made. As a result, the communication itself does not end in error even if the reception of the retraining signal fails, as compared with the conventional one in which the reception side fails to receive the retraining signal and thus cannot receive the image data.

In step S1076, the counter 1 for counting the number of NSF transmissions is incremented, and then the retraining signal is received, so the flow proceeds to step S1038.

Step S1078 is a step of branching when reception of the retraining signal fails. Step S500 in FIG.
If the reception of the retraining signal immediately after transmitting the CFR signal in 8 fails, the transmitter is requested to retransmit the error. However, if it fails to receive the retraining signal again after making an error resending request once, it controls whether to send the NSF signal or the DCN signal according to the count value of the NSF signal sending count counter. To do.

If it is determined in step S1078 that SED = 1 has been detected during the above-described retraining signal detection period of 3.5 seconds, it is determined that the retraining signal has arrived, and step S105
Proceed to step 6 to interrupt the sending of image data to the sending side.
Send an IS signal.

If it is determined in step S1078 that SED = 1 could not be detected, it is determined in step S1080 whether NSF has been transmitted for a retransmission request. Here, if the NSF signal is transmitted once, no signal arrives from the transmitting side even though the NSF signal is transmitted. That is, it means that the NSF signal was transmitted after the PIS signal was transmitted once before, and it can be said that the transmission side interrupts the transmission of the image data by the PIS signal. Therefore, once NS
If there is no response from the transmitting side after transmitting the F signal, the NSF signal is transmitted without transmitting the PIS signal for interrupting the transmission of the image data to the transmitting side.

Therefore, if it is determined in step S1080 that the NSF signal has been transmitted for the retransmission request, the count value of the NSF transmission number counter is checked in step S1082, and it is determined whether the count value is 3 or more again. , NSF signal (step S1074) or DCN signal (step S1084)
Select whether to terminate communication in error (step S1086).

On the other hand, if it is determined in step S1080 that the NSF signal is not transmitted due to the retransmission request, C in step S5008 in FIG.
Since the PIS signal has never been transmitted after FR transmission, in order to suspend the transmission of image data on the transmission side.
Need to send PIS signal. Therefore, step S1080
If it is determined that the NSF signal is not transmitted due to the retransmission request, the process proceeds to step S1056, and the PIS signal is transmitted.

[Effects] According to the present invention, in a facsimile apparatus capable of requesting error retransmission, a training signal can be normally received, and after sending a confirmation signal notifying the sending side that image data is ready to be received, If the retraining signal, which is the training signal transmitted immediately before the data, fails to be received, an error resend request signal is transmitted, so when the retraining signal communication fails, it is possible to prevent the communication from ending in error. .

[Brief description of drawings]

 FIG. 1 is a diagram showing a conventional signal procedure, FIG. 2 is a diagram showing a signal procedure of this embodiment, FIG. 3 is a block diagram of this embodiment, and FIG. 4 is a description of training signal detection. FIG. 5, FIG. 5 is a flowchart of training signal detection, FIG. 6 is a flowchart of this embodiment, and FIG. 7 is a flowchart of this embodiment. 40, NCU 42, hybrid circuit 44, signal presence / absence detection circuit 46, demodulator 50, NSF signal transmission circuit 52, retransmission request signal transmission circuit 54, addition circuit 56, FIFO memory 58, line The number storage memory 60, the decoder 64, and the recording device 66 are control circuits.

Claims (1)

[Claims] 1. A receiving means for receiving image data transmitted from a transmitting side and a training signal transmitted prior to the image data, and a transmitting side indicating that the training signal can be normally received and the image data is ready to be received. Confirmation signal transmitting means for transmitting a confirmation signal for notifying to, detection means for detecting an error in the received image data, and an error retransmission request signal for requesting retransmission of the image data based on the detection result of the detection means. In a facsimile apparatus having an error resending requesting means, if the receiving means fails to receive a retraining signal which is a training signal transmitted after the confirmation signal transmitting means transmits the confirmation signal and immediately before the image data. ,
A facsimile apparatus comprising: control means for causing the retransmission request means to transmit an error retransmission request signal.