JPS63214047A - Picture receiver - Google Patents

Abstract

PURPOSE:To attain proper picture communication independently of the state of lines by providing a means for sending a prescribed response signal in response to a training check signal received prior to picture data and sending a prescribed response signal and a means for setting a maximum waiting time till the picture data is received after the transmission of the response signal. CONSTITUTION:In the picture receiver, a control signal of 300bps sent from a reception side via a transmission line 9 is branched by a 2/4-wire conversion circuit 8 and given to a backward signal detection section 10 and a demodulation section 11 respectively. In this case, since the input signal speed is 300bps, only the output of the demodulation section 11 is effective and the output signal of the demodulation section 11 is analyzed by a control signal analysis section 12. A transmission control section 5 allows a control signal generating section 2 to generate a control signal corresponding to the analyzed control signal and gives the result to a modulation section 4 via a switch circuit 3. The modulation output 4a outputted from the section 4 is led to the circuit 8 via a changeover circuit 7 and sent to the transmission line 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image receiving device that receives image data through full-duplex communication.

[Prior Art] Image communication devices having an image transmission function according to an error control procedure have been known. For example, "Facility J (VOL, 38 No. 51986, No. 59, published by NTT)
As described in page 1, there is a known device that performs half-duplex communication for pre-procedures and post-procedures, and performs full-duplex communication only when transmitting images.

On the receiving side of such a communication device, first, the initial identification signal NS
F (non-standard device)/DIS (digital identification signal) notifies the transmitting side that it has an error control function. In response, the transmitting side transmits a reception command signal NSS (non-standard device setting) and DC5 (digital command signal).

This instructs the receiving side to perform the error control procedure, and subsequently transmits the training check signal TCP.

This training check signal TCF is all “°O”
The image signal transmission speed is 9600bps.
, 7200bps, 4800bps.

It is transmitted for 1.5 seconds at the actual transmission rate of 2400 bps.

In response to this training check signal TCP, the transmitting side confirms that the reception preparation confirmation signal CFR has been returned from the receiving side, and starts transmitting the image signal.

On the other hand, the receiving side decodes the received image signal and also monitors for errors. When an error is detected, an error notification signal NAC is transmitted at that time.

On the transmitting side, the error notification signal NAC is sent even while transmitting the image signal.
The arrival of the error notification signal NAC is monitored, and the transmission of the image signal is interrupted when the error notification signal NAC is detected. Then, following the error notification signal NACK, a control signal sent from the receiving side is received, and the image signal is retransmitted from the point specified by this control signal.

Thus, error-free, high-quality facsimile transmissions are achieved.

[Problems to be Solved by the Invention] However, such conventional image communication systems have the following drawbacks.

■ In a communication line, the line status may differ between the direction from the transmitting side to the receiving side and the direction from the receiving side to the transmitting side. For this reason, even if the image signal is transmitted normally from the transmitting side to the receiving side, the error notification signal that is sent when a reception error is detected is not detected correctly on the transmitting side, and the Normal error control procedures may not occur. As a result, there was a drawback (the first drawback) of causing a state of communication failure.

(2) In addition, an AC 1H failure may occur due to propagation delay in the communication line. In other words, even if the receiving side detects an error in the image signal and transmits the error notification signal NACK, a delay time of about 1 second is required for the error notification signal NACK to arrive at the sending side. There is. Therefore, in such a case, it is necessary for the transmitting side to constantly store about 2 seconds worth of data in order to resend the image data. For example, when the image data transmission speed is 9600 bps, 2.4 bytes (9600 bps)
x 2 ÷ 8 = 2400 bytes) memory capacity is required. Furthermore, when considering the detection time of the error notification signal NACK, the influence of an echo suppressor in international communication, etc., a larger memory capacity is required.

Therefore, if a facsimile device with a small memory capacity is used to communicate over a line with a large propagation delay, image retransmission will not be possible, resulting in poor communication (second drawback).

■ In order to avoid the second disadvantage mentioned above, it would be sufficient to incorporate a large capacity memory, but this would lead to an increase in the size and cost of the device (third disadvantage).
can be seen.

SUMMARY OF THE INVENTION In view of the above-mentioned points, an object of the present invention is to provide an image receiving apparatus configured to perform proper image communication regardless of the line state.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an image receiving apparatus that receives image data through full-duplex communication, in which a training check signal received prior to the image data is The apparatus includes a response means for transmitting a predetermined response signal in response, and a timer means for setting a maximum waiting time from the time the response signal is transmitted until the image data is received.

[Function] In the image receiving device according to the present invention, a training check signal sent from the transmitting side is received, a predetermined response signal is sent out, and an image is output within a certain waiting time after receiving the response signal. When data is sent and received, images are received by full-duplex communication.

[Example] Hereinafter, the present invention will be described in detail based on Examples.

FIG. 1 is a schematic explanatory diagram of an image receiving device according to the present invention. That is, in an image receiving apparatus that receives image data through full-duplex communication, a response means for transmitting a predetermined response signal in response to a training check signal received prior to the image data; and a timer means for setting the maximum waiting time until the image data is received after transmission, and if the image data is not sent even after the waiting time, half-duplex communication is performed after a predetermined procedure. (i.e., image reception without using an error control procedure).

A more detailed explanation of such an image receiving device is as follows.

First, prior to transmitting an image signal, a training check signal (TCF) is transmitted from the transmitting side to the receiving side. During this, the receiving side checks this training check signal, and only if the signal is good, the receiving side transmits a predetermined response signal (for example, an error notification signal used in the error control procedure) to the transmitting side. do. The transmitting side monitors the reception state of this response signal while transmitting the training check signal, and determines whether or not the response signal can be received normally. As a result, if it is determined that the line condition is such that it is not possible to receive a response signal, the
Transmission of image signals is performed by multiplex communication (ie, without error control procedure).

Further, if the training check signal (TCP) cannot be received well on the receiving side, the receiving side does not transmit a response signal (error notification signal) to the transmitting side and performs communication according to the conventional procedure.

FIG. 2 is a block diagram showing an embodiment of a G III type facsimile machine to which the present invention is applied. In this figure, 1 is an image reading unit that reads image data and converts it into an electrical signal, 2 is a control signal generator for controlling communication, and 3 is a reading unit 1.
4 is a switching circuit that selects either the image signal obtained from the control signal generation section 2 or the control signal generated from the control signal generation section 2; 4 is a modulation section that modulates the output signal of the switching circuit 3 (the control signal is based on CCITT recommendation V21 modulation); 5 is a transmission control unit that controls the transmission procedure, and 6 is a backward signal generation unit (for the backward signal of the V27ter or V29 modulator, a single signal outside the required modulation band is used). Tone (2900Hx or higher/400Hz or lower) or 75
7 is a switching circuit that switches between the modulation signal 4a and the backward signal 6a, 8 is a 2-wire and 4-wire conversion circuit, 9 is a 2-wire transmission line, and 10 is a transmission line that is connected via the transmission line 9. A backward signal detection section that detects a backward signal sent from the receiving side; 11 a demodulation section that demodulates a modulated signal sent via the transmission path 9; 12 a backward signal detection section 10 and a demodulation section 11 is a control signal analysis unit that analyzes a communication control signal based on the output signal; 13 is a received image recording unit; 14 is a ROM that stores the control procedure shown in FIGS. 6 and 7 (described in detail later); .

15 is a RAM that stores various data.

Next, the operation for transmitting image data will be explained with reference to the block diagram shown in FIG.

300 bps sent from the receiving side via transmission path 9
The control signal is divided by the two-line and four-line conversion circuit 8 and inputted to the backward signal detection section 10 and the demodulation section 11, respectively. In this case, since the input signal is a 300 bpS control signal, the output of the backward signal detection section 10 is meaningless, and only the output of the demodulation section 11 is valid. Demodulator 1
The output signal of 1 is analyzed by the control signal analysis section 12.

The transmission control section 5 causes the control signal generation section 2 to generate a control signal corresponding to the analyzed control signal, and inputs it to the modulation section 4 via the switching circuit 3. A modulated output 4a outputted from the modulation section 4 is introduced into a two-line/four-line conversion circuit 8 via a switching circuit 7, and is sent out to a transmission line 9.

FIG. 3 is a diagram showing a process when the facsimile apparatus shown in FIG. 2 performs full-duplex communication, and FIG. 4 is a diagram showing a process when the facsimile apparatus shown in FIG. 2 performs half-duplex communication.

FIG. 5 is a timing diagram showing control signals sent from the transmitting side and the receiving side, including propagation delay times.

FIG. 6 is a flowchart showing the control procedure to be executed by the sending facsimile machine, and FIG. 7 is a flowchart showing the control procedure to be executed by the receiving facsimile machine.

First, with reference to Figure 3, Figure 6, and Figure 7, all 21
The process of transmitting images using i-communication will be explained.

As shown in FIG. 3, the transmitting side receives the pre-procedure signal 16 sent from the receiving side, and determines whether the receiving side has a full-duplex communication function (step 56-1).
). As a result, if it is determined that full-duplex communication is possible, the sending side pre-procedure signal 17 is sent to the receiving side to transmit full-duplex communication.
A command is given to perform heavy communication (step 58-2. step S7-1), and following this, the sending side connects the line (
A training check signal 18 (T(:F)) is sent out by the high-speed modem in order to check the state of the transmission line (step S8-3).

On the other hand, on the receiving side, while receiving the training check signal 18 (step S7-2), the receiving state is monitored (step 57-3). Normally, the training check signal 18 is in a continuous state of "0", so the receiving side
When a predetermined number of consecutive °0''s are detected (while the training check signal 18 is still on the transmission path)
, The ACK signal 19 is sent to the transmitting side via the backward channel as a signal confirming that full-duplex communication is possible (step 57-4). In this embodiment, the error notification is sent to this 8C as a signal. A signal of the same format as the signal NAC is used.

On the transmitting side, while transmitting the training check signal 18, the signal 19 is sent to the AC by the backward signal detection unit 1.
If it is detected as 0 (step 5R-4), it is determined that full-duplex communication is possible and the transmission of the training check signal 18 is stopped.Step S8-5), image communication 20 using full-duplex communication is started (step S8-5). Step 58-8).

Next, with reference to FIG. 4, FIG. 6, and FIG. 7, the process of transmitting images by half-duplex communication will be described.

As shown in FIG. 4, the CK signal 19 from the receiving side
is not detected by the sender for some reason (
Step S6-4), the transmitting side waits for a certain period of time (Steps 56-3→56-4→5B-7), and then stops sending out the training check signal 18 (Step 5S-8).

On the other hand, the receiving side waits to receive the image signal 20 (see Figure 3) through full-duplex communication (steps 57-4→57-5).
→S7-6) Since the image signal 20 does not arrive, a timeout occurs (step 57-8), and the reception preparation confirmation signal 21 is sent to the transmitting side via the 300 bps modem (step S7-9). By doing this, preparations are made to perform image communication using half-duplex communication (step S7-12).
.

On the transmitting side, when the reception preparation confirmation signal 21 is detected by the 30Qbps model (step S8-9), it is determined that full-duplex communication is impossible, and image communication 22 using half-duplex communication is started (step S8-9). 56-12).

The 3 "T1 time over" shown in step 56-7 in FIG. 6 will be explained in more detail.

The above "T1" is the setting value of the timer provided on the transmitting side, and the specific length is shown in Figure 5. This shows the timing of the message procedure. Td shown in FIG. 5 represents the required propagation time from when the signal is transmitted until it reaches the other party. ) is controlled so that its duration matches the set value of the TI timer.

As is clear from FIG. 5, T1 is determined as follows.

TI = TdX 2 + (TCF signal verification time on the receiving side = Tr) + (AC signal verification time on the transmitting side = Tt) In addition, the above T1 is also related to the storage capacity of the memory provided on the transmitting side. shall be determined based on the For example, when Td=1 second, TI=2 seconds even if Tr=Tt=0 seconds. Therefore, the amount of data sent in 2 seconds is 9600 x 2 x when the transmission speed is 9600 bps
1/8 = 2400 bytes.

Therefore, if the storage capacity on the sending side is small, it is necessary to set the timer setting value T1 small. As a result, if the time required for a signal to arrive at the AC sent from the receiving side during the training check sequence exceeds the set time T1, it is determined that the propagation delay time of the line is too large. Even if the error notification signal NA (:K is detected, it is determined that normal retransmission processing is impossible), and the image signal is transmitted (image transmission using half-duplex communication) without an error control procedure. be.

In this case, the quality of the received image signal will deteriorate due to not performing error control, but generally speaking, if the condition of the line from the transmitting side to the receiving side is determined to be good at the training check stage, then The probability that an error will occur is very low, and there is no problem in practice.

FIG. 8 is a block diagram showing another embodiment of the present invention. In this figure, the same elements as those shown in FIG. 2 are given the same reference numerals. In the embodiment shown in FIG. 2, in order to perform full-duplex communication, the backward signal generator 6
However, in this embodiment, an echo canceller 30 is used and the backward signal generating section 6 and the backward signal detecting section 7 are omitted. Therefore,
The demodulating section 11 of the transmitting modem is used as a backward signal detector, and the modulating section 4 of the receiving modem is used as a backward signal generator.

Note that the present invention is not limited to the embodiments described so far, and for example, the circuit configuration of the facsimile machine, the configuration of the error notification signal, etc. can be modified in various ways without departing from the gist of the present invention. be.

[Effects of the Invention] As explained above, according to the image receiving device according to the present invention, the line is checked in both the transmitting and receiving directions during the training check sequence, and the image data is transmitted within a predetermined waiting time after transmitting the response signal. Since full-duplex communication is performed only when reception is possible, it is possible to select full-duplex communication or half-duplex communication within a short period of time without the need for extra control signals. Become.

In one embodiment of the present invention, in addition to the effects of the invention described above, the following effects can be obtained.

In one embodiment of the present invention, the error notification signal NAC already used in the error control procedure is used as a response signal (ACK signal), and this NACK signal is used during the transmission period of the training check signal TCP (i.e. Since the image signals are transmitted in parallel with image signal training, there is no need to prepare any new control signals. Since the NAC transmits a signal to the transmitting side only when the training check signal TCP is successfully received, there is no need to use the reception confirmation signal CFR signal. This results in
It becomes possible to shorten the control time and perform appropriate image communication without significantly changing the existing communication control procedure.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of the present invention, FIG. 2 is a block diagram showing an embodiment of a facsimile apparatus to which the present invention is applied, FIG. 3 is a diagram showing the process of performing full-duplex communication, and FIG. The figure is half 2
5 is a diagram showing the propagation delay state of control signals, FIG. 6 is a flowchart showing the control procedure on the transmitting side, FIG. 7 is a flowchart showing the control procedure on the receiving side, FIG. 8 is a block diagram showing another embodiment. 2... Control signal generation section, 3... Switching circuit, 4... Modulation section, 5... Transmission control section, 6... Packed word signal generation section, 7... Switching circuit, 8. ... 2-wire 4-wire conversion circuit, 9... Transmission line, IO... Packed word signal detection section, 11... Demodulation section, 12... Control signal analysis section. Su Rainbow Ikichi 4de 1
Figure 4

Claims (1)

[Scope of Claims] An image receiving device that receives image data through full-duplex communication, comprising: response means for transmitting a predetermined response signal in response to a training check signal received prior to the image data; An image receiving device comprising: timer means for setting a maximum waiting time from when the response signal is sent until the image data is received.