JPH0787521B2 - Fax machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a facsimile apparatus that performs error retransmission, and more particularly to a receiver side of a facsimile apparatus that performs error retransmission.

[Prior Art] In a conventional facsimile apparatus that performs error resending, when an error resending request signal is transmitted from a receiving side but the sending side cannot receive the error resending request signal, the error resending fails and the communication ends in error. Was.

Further, when the receiving side cannot receive the image data retransmitted from the transmitting side in response to the error resending request, the resending has failed and the communication is ended in error.

In view of the above points, the present invention provides a facsimile device having an error correction function by full-duplex communication, which can prevent the communication from ending in error when the resending process of image data fails. The purpose is to provide.

[Embodiment] The outline of the operation of this embodiment is shown in FIGS.

Here, in the present embodiment, for convenience of description, the training signal immediately before the TCF signal and the training signal immediately before the image data PIX (CFR
The training signal immediately before (after CFR) the image data PIX is referred to as a retraining signal in order to distinguish it from the (after) training signal.

The signals used in this embodiment are those specified in CCITT Recommendation T.30.

FIG. 1 is a diagram showing exchange of signals when error retransmission is successful.

In FIG. 1, first, a pre-procedure is performed to start transmission of image data. Then, a line failure occurs during the communication of the image data, and an error occurs in the image data received by the receiving side. Due to this error occurrence, the reception side transmits an error retransmission request signal (in this embodiment, the PIS signal is used) to the transmission side. The transmission side receives the PIS signal and interrupts the transmission of the image data. Then, when the transmission side interrupts the transmission of the image data, the reception side transmits the NSF signal and indicates the retransmission start line number. The transmission side that receives this NSF signal retransmits the image data from the line number designated by the NSF signal. If the image data is successfully retransmitted, the post-procedure is performed and the communication is ended.

FIG. 2 is a diagram showing exchange of signals when error retransmission fails. FIG. 2 shows the exchange of signals when the transmitting side fails to receive the error retransmission request signal.

In FIG. 2, as in FIG. 1, an error occurs in the image data received by the receiving side, and the receiving side transmits an error retransmission request signal to the transmitting side. The transmission side receives the PIS signal and interrupts the transmission of the image data. Then, when the transmission side interrupts the transmission of the image data, the reception side transmits the NSF signal and indicates the retransmission start line number. However, if a line failure occurs during NSF signal communication, the transmitting side may not be able to receive the NSF signal. At this time, the transmission side waits for the NSF signal from the reception side until the NSF signal is normally received from the reception side. On the other hand, the receiving side determines that the error resending has failed because the retraining signal and the image data for error resending have not been sent from the sending side even though the NSF signal has been sent. Therefore, the receiving side transmits the NSF signal again. The sender that received this retransmitted NSF signal sends N
Resend image data from the line number specified by the SF signal. If the image data is successfully retransmitted, the post-procedure is performed and the communication is ended. As a result, even though the NSF signal indicating the retransmission start line number is transmitted, that NSF signal is transmitted.
It is possible to prevent the communication from ending in error due to the error of the signal and the failure of the error retransmission.

FIG. 3 is also a diagram showing exchange of signals when error retransmission fails. FIG. 3 shows the exchange of signals when the receiving side fails to receive the retraining signal after the start of error retransmission.

In FIG. 3, as in FIG. 1, an error occurs in the image data received by the receiving side, and the receiving side transmits an error resend request signal to the transmitting side. The transmission side receives the PIS signal and interrupts the transmission of the image data. Then, when the transmission side interrupts the transmission of the image data, the reception side transmits the NSF signal and indicates the retransmission start line number. The transmission side that receives this NSF signal retransmits the image data from the line number designated by the NSF signal. Here, since the retraining signal is always transmitted immediately before the image data, the retraining signal is transmitted from the transmitting side to the receiving side prior to error retransmission of the image data. However, prior to the error retransmission of the image data, a line failure may occur during communication of the retraining signal, and the receiving side may fail to receive the retraining signal. At this time, the receiving side cannot receive the image data following the retraining signal, and thus determines that the error retransmission has failed. Then, the PIS signal is transmitted again. The transmission side receives the PIS signal and interrupts the transmission of the image data. When the transmission side suspends the transmission of the image data, the reception side transmits the NSF signal again. This retransmitted NSF
The transmission side that has received the signal retransmits the image data from the line number designated by the NSF signal. If the image data is successfully retransmitted, the post-procedure is performed and the communication is ended. As a result, even if the receiving side requests error retransmission, it is possible to prevent the communication from ending in error due to an error in the retraining signal transmitted prior to the error-retransmitted image data and error retransmission. .

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

FIG. 4 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 device 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.

Reference numeral 50 is a circuit for transmitting an NSF signal. NSF signal transmission circuit
50 is NS on signal line 50a when a pulse occurs on signal line 66b.
Send the F signal. The NSF signal contains the line number. The value output to the signal line 66a is set to this line number. The signal line 66a includes the signal line 58a.
A value obtained by adding 1 to the value of the line number output to is output. The NSF signal transmission circuit 50 generates a pulse on the signal line 50b when the transmission of the NSF signal is completed.

52 is a circuit for transmitting a PIS signal as an error resend request signal. The PIS signal transmission circuit 52 is a circuit for transmitting a PIS signal (a 462 Hz signal for 3 seconds) to the signal line 52a when a pulse occurs on the signal line 66c. The PIS signal transmission circuit 52 is
When the signal transmission is completed, a pulse is generated on the signal line 52b.

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 demodulated data demodulated by the demodulator 60 from the signal line 66n and records it on the recording paper.

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

FIG. 5 is an explanation of the training signal detection operation used in this embodiment.

FIG. 5 (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. 4, and becomes high level when it is detected that there is a signal on the line. (3) of FIG. 5 is a waveform of a carrier detect (CD) signal indicating whether or not effective data transmitted at a transmission speed for transmitting 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. 4 by the control circuit 66, and is generated inside the control circuit 66. Signal to do.

From (1) to (3) in FIG. 5, 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 received (2400bi
Tr = 1158ms at t / s, Tr = 923ms at 4800bit / s).

FIG. 6 is a flowchart of the training signal detection operation of the control circuit 66 of FIG.

Step S1000 in FIG. 6 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, CD = continuous for a millisecond (a = 700 ms at 2400 bit / s, a = 500 ms at 4800 bit / s) while judging whether or not the timer T2 times out.
It is determined whether it is 0 or not. 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 S10101, the control circuit 66 transmits the CFR signal if the received signal is the training / TCF signal, and receives the image data if the received signal is the training (retraining) / image data. To do.

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. 7 is a flow chart of the receiving operation of this embodiment, showing the operation of the control circuit 66 of FIG. FIG. 7 is the same as the conventional operation, except for the image receiving process of step S5010 (details will be described later).

In FIG. 7, after receiving a call, while waiting for the reception of NSS / TSI / DCS in step S5002 while transmitting NSF / CSI / DIS in step S5000.

If NSS / TSI / DCS is received in step S5002, step S5
Receive Training / TCF at 004. 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, the 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 the reception of / TSI / DCS, and if received, proceed to step S5004.

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 /
Determine which signal of MPS / EOP is received. If EOM is received, proceed to step S5000. If MPS is received,
Proceeds to step S5010. If the EOP is received, the remaining post-procedure is performed in step S5016, and the reception ends.

FIG. 8 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. If the retraining signal is successfully received within 3.5 seconds in step S1038, step S1
If the reception of the retraining signal is not successful within 3.5 seconds, 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 to request 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, it is detected in step S1041 whether or not the image data received has an error, and image reception is performed until RTC is detected in step S1046.

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 image data has an error, in step S1056, the PIS signal is transmitted in full-duplex operation in order to suspend the transmission of the 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, the receiving side is PIS.
This means that the transmission side has not interrupted the transmission of image data even though the signal has been transmitted. Since the PIS signal used in this embodiment is a tonal signal for 3 seconds, it is a signal that can be transmitted / received even if the line condition is bad. The fact that the sending side cannot receive this PIS signal means that the sending side facsimile device is out of order, or the PIS signal sending circuit 52 in FIG. 4 is out of order, or the line state has suddenly changed and the line state has changed. Can be judged to have become significantly worse, and in any case, it can be said that further communication cannot be continued. Therefore, in step S1060, SED =
If it is determined to be 1, in step S1062, the PIS signal for interrupting the transmission of the image data is transmitted to the transmission side,
A DCN signal is transmitted in step S1068, and 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 number 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 retraining fails, the transmitter is requested to retransmit all image data. In response to this 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 was made. As a result, the receiving side does not have to terminate the communication itself due to an error even if the reception of the retraining signal fails, as compared to the conventional case in which the reception of the retraining signal fails to receive the image data. .

In step S1076, the counter that counts the number of NSF transmissions is incremented by 1, and the process proceeds to step S1038 to receive the retraining signal.

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, an error retransmission request is issued to the transmitting side. But,
If the reception of the retraining signal fails again after the error retransmission request is made once, which of the NSF signal and the DCN signal is transmitted is controlled according to the count value of the NSF signal transmission number counter.

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. It is selected whether the NSF signal is transmitted (step S1074) or the DCN signal is transmitted (step S1084) and the communication is ended 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 S
If it is determined in 1080 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 having an error correction function by full-duplex communication, an interruption signal for interrupting transmission of image data and a request for resending image data in which an error has been detected are issued to the transmitting side. Resending request of image data to the transmitting side using a resending request signal, if there is no response from the sending side to the resending request signal, resending the resending request signal without resending the interruption signal, On the other hand, when the image data is retransmitted from the transmitting side in response to the retransmission request signal but the reception start of the retransmitted image data fails, the interruption signal and the retransmission request signal are transmitted. When is failed, an appropriate signal according to the situation can be transmitted, and it is possible to prevent the communication from ending in error.

[Brief description of drawings]

 FIG. 1 is a diagram showing a signal procedure of this embodiment, FIG. 2 is a diagram showing a signal procedure of this embodiment, FIG. 3 is a diagram showing a signal procedure of this embodiment, and FIG. FIG. 5 is a block diagram of the present embodiment, FIG. 5 is an explanatory diagram of training signal detection, FIG. 6 is a flowchart of training signal detection, FIG. 7 is a flowchart of this embodiment, and FIG. 8 is a flowchart of this embodiment. It is a flowchart. 40, NCU 42, hybrid circuit 44, signal presence / absence detection circuit 46, demodulator 50, NSF signal transmission circuit 52, PIS signal transmission circuit 54, addition circuit 56, FIFO memory 58, line number The storage memory 60, the decoder 64, and the recording device 66 are control circuits.

Claims (1)

[Claims] 1. A facsimile apparatus having an error correction function by full-duplex communication, detecting means for detecting an error in received image data, and transmitting image data to a transmitting side based on a detection result of the detecting means. First transmitting means for transmitting an interruption signal for interruption to the transmitting side in full-duplex operation while receiving image data; first determining means for determining whether or not the transmitting side is transmitting image data; (1) If the determination unit determines that the transmission side is not transmitting image data after the transmission unit transmits the interruption signal, the detection unit retransmits the image data in which the detection unit detects an error. Second retransmission means for transmitting a retransmission request signal for requesting the retransmission request, second determination means for determining whether or not the retransmission of the image data is started by the transmission side according to the retransmission request signal, and retransmission start by the transmission side Third determining means for determining whether or not the reception start of the received image data has failed, and after the second transmitting means transmits the retransmission request signal, the transmitting side retransmits the image data by the second determining means. When it is determined that the transmission is started and when it is detected by the third determination means that reception of the retransmitted image data has failed, the first transmission means is caused to retransmit the interruption signal and the second transmission means is transmitted. To retransmit the retransmission request signal,
On the other hand, after the second transmission means transmits the retransmission request signal, if the second determination means does not determine that the transmission side has started to retransmit the image data, the interruption signal is sent to the first transmission means again. A facsimile apparatus comprising: a means for causing the second transmitting means to retransmit the retransmission request signal without transmitting the retransmission request signal.