JP2810064B2 - Image communication device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image communication apparatus having demodulation means for demodulating a received signal and performing communication at any one of a plurality of transmission speeds.

[Conventional technology]

2. Description of the Related Art Conventionally, there has been known a facsimile apparatus configured to transmit a line status check signal in advance to check whether a channel can be used at a predetermined transmission speed prior to image transmission. That is, this facsimile apparatus is a G3 standard facsimile apparatus specified by the CCITT-T4 recommendation.

In this type of facsimile apparatus, prior to high-speed image transmission, an automatic equalizer on the receiver side is adjusted using a training signal and a training check signal so as to conform to line characteristics, and the result of the adjustment is adjusted. Is determined, and a signal indicating that the training is successful or a signal indicating whether the training has failed and the retraining is requested is transmitted from the receiving side to the transmitting side.

The procedure of the G3 image communication system will be described with reference to FIGS. 8 (1) to 8 (3).

FIGS. 8 (1) to 8 (3) show an example of a procedure of a conventionally known G3 image communication system. In each of these figures, a signal on the left side of the center line is a signal transmitted by the transmitter, and a signal on the right side is a signal transmitted by the receiver.

The NSF (non-standard equipment) signal, CSI (called station identification) signal, and DIS (digital identification) signal shown at the top of FIGS. 8 (1) and (2) are initial identification signals, and are used as facsimile machines of the own machine. Is a signal for transmitting the function of (1) to the other device.

Next, an NSS (non-standard device setting) signal, a TSI (transmitting station identification) signal, and a DCS (digital command) signal transmitted from the transmitting side are reception command signals, and designate a mode in which transmission is to be performed. And then TCF (Training Check)
When a signal is transmitted and a CFR (reception preparation confirmation) signal is transmitted from the receiver in response to the signal, the transmission speed of the image signal to be transmitted continuously is determined. (Fig. 8 (1)
reference).

The TCF (training check) signal is a signal transmitted through a group 3 modulation system, and is a signal that confirms training and first indicates whether a channel can be used at that speed. The format is a continuous signal of "0" for 1.5 seconds.

The training signal transmitted immediately before the TCF signal is a synchronization signal for appropriately adjusting the receiving modem. This synchronization signal is used for carrier detection and, if necessary, for AG
C, timing synchronization, equalizer convergence, and descrambler synchronization.

The CFR (reception preparation confirmation) signal and the FTT (train failure) signal shown in FIG. 7 (2) are pre-message response signals. That is, the CFR (reception standard acknowledgment) signal is a digital response signal for confirming that all message pre-procedures have been completed and that message transmission can be started. In contrast, the FTT (Train Failure) signal is an optional digital response signal to remove all or part of the message pre-procedure and request retraining of the group 3 modulation system.

When the TCF signal is received in this manner, a CFR signal is transmitted if the channel can be used at the speed, and an FTT signal is transmitted if the channel cannot be used at the speed.
(In other words, only one decision can be made for every two).

PIX shown in FIG. 8 (1) is an image signal. That is,
Immediately before the transmission of the image signal, the training signal is transmitted.

EOP transmitted from the transmitting side is a procedure end signal. The MCF subsequently transmitted from the receiving side is a message confirmation signal.

This will be described more specifically with reference to FIGS. 8 (1) to 8 (3) again. 8 (1) to 8 (3), it is assumed that both the transmitter and the receiver have a function of transmitting at a transmission speed of 2400b / s, 4800b / s, 200b / s, and 9600b / c.

In the procedure shown in Fig. 8 (1), transmission was attempted at 9600 b / s. On the other hand, the receiver side received the TCF signal correctly, so the CFR signal was sent out, and image transmission was performed at 9600 b / s. This is an example. The criteria for determining whether to receive the TCF signal and transmit the CFR signal or to transmit the FTT signal are left to each manufacturer. As an example, it is designed to check the demodulated TCF signal, transmit a CFR signal when data "0" can be received continuously for 1.0 second or more, and transmit an FTT signal otherwise.

FIGS. 8 (2) and 8 (3) show the procedure when the line condition is bad. First, as shown in FIG.
Attempt to transmit at b / s. However, since the receiver cannot correctly receive the TCF signal, the receiver transmits the FTT signal. The transmitter then attempts to transmit at 7200 b / s.
Also in this case, the receiver transmits the FTT signal because the receiver cannot correctly receive the TCF signal. Then the transmitter then goes to 4800b / s
Attempt to transmit on. However, since the receiver cannot receive the TCF signal correctly, it transmits the FTT signal.

The transmitter sends a FCF to a 9600b / s or 7200b / s TCF signal.
When the TT signal is received, the T at 7200b / s and 4800b / s
It is set in advance to shift to the CF signal. In contrast, for 4800b / s or 2400b / s TCF signals, 2
It is designed in advance to shift to transmission of a TCF signal at 2400 b / s or line disconnection when receiving the FTT signal twice. The reason is that at 4800 b / s or 2400 b / s, we want to try transmission at that speed as much as possible.

Therefore, the transmitter continues trying to transmit again at 4800 b / s. However, since the receiver cannot correctly receive the TCF signal, the receiver transmits the FTT signal. Thus, the transmitter has received the FTT signal twice for the TCF signal at 4800 b / s, and then attempts to transmit at 2400 b / s. On the other hand, since the receiver has correctly received the TCF signal, the receiver transmits the CFR signal, and image transmission is performed at 2400 b / s.

[Problems to be solved by the invention]

As described above, in the above-described conventional example, the transmission at the specific speed is performed in response to the line status check signal for checking whether or not the transmission at the specific speed is possible. There is a drawback that you can only make an alternative decision, "I can't."

Specifically, as shown in Fig. 8 (2), when the line condition is poor, fallback from 9600b / s to 7200b / s, 4800b / s, and 2400b / s is started. There was a major drawback that it took a lot of time.

Looking at facsimile machines in the future, 12000b
Transmission at high speeds such as / s, 14400b / s, and 19200b / s is considered. For example, 19
Despite having the function of transmitting at a transmission speed of 200b / s, the line conditions that happened to be connected were poor, and 2400b / s
If transmission can only be performed at the transmission speed of
Since the transmission speed is reduced by one step each time a signal is received, until the pre-procedure is completed (the receiver is
About 42 seconds elapse before the signal is transmitted).

Accordingly, it is an object of the present invention to provide an image communication apparatus that simplifies a configuration for quickly and accurately determining a transmission speed and further enhances versatility in view of the above points.

[Means for solving the problem]

In order to achieve the above object, the present invention has a demodulation means for demodulating a received signal, and in an image communication apparatus performing communication at any one of a plurality of transmission speeds, a communication partner transmits predetermined data. In this case, the communication is performed in the first communication mode depending on the function of the transmitting side that is the communication partner with the measurement unit that measures the time when the predetermined data is demodulated and output from the demodulation unit, or Control means for determining whether to communicate in the second communication mode, wherein the control means (a) receives image information in accordance with the recommendation of T30 in the first communication mode; In the communication mode, when the predetermined data transmitted from the communication partner to determine the transmission speed prior to the transmission of the image information is received, the time measured by the measurement unit is used. Then, a desired transmission speed is selected from among the plurality of transmission speeds, or a line is selected to be released, the transmission side is notified of the result of the selection, and further reception of image information is performed at the desired transmission speed. After performing, when there is a next document, when the predetermined data transmitted again prior to the next document is received,
Based on the time measured by the measuring means, to select a desired transmission speed among the plurality of transmission speeds, or to select a line release, when notifying the transmission side of the selected result, When the predetermined data is transmitted at the first transmission speed, based on the time measured by the measuring means, when selecting a desired transmission speed or selecting a line release, If the time measured by the measuring means is equal to or longer than a first time, select the first transmission speed;
On the other hand, when the predetermined data is transmitted at a second transmission speed lower than the first transmission speed, a desired transmission speed is selected based on the time measured by the measuring unit. Alternatively, in selecting the line release, the first transmission speed is selected if the time measured by the measuring means is equal to or longer than a second time longer than the first time.

[Action]

In the present invention having the above configuration, (a) the first
In the communication mode of (1), image information is received in accordance with the recommendation of T30. (B) In the second communication mode, the communication information transmitted from the communication partner to determine the transmission speed prior to the transmission of the image information is transmitted. When predetermined data is received, based on the time measured by the measuring means, select a desired transmission speed among the plurality of transmission speeds, or select a line release, and After notifying the selected result and further receiving image information at the desired transmission speed, if there is a next original,
When the predetermined data transmitted again prior to the next original is received, a desired transmission speed among the plurality of transmission speeds is selected based on the time measured by the measurement unit. Or, when the release of the line is selected and the transmitting side is notified of the result of the selection, if the predetermined data is transmitted at the first transmission speed, the time measured by the measuring unit is used. In selecting a desired transmission speed or selecting a line release based on the above, if the time measured by the measuring means is equal to or longer than a first time, the first transmission speed is selected. On the other hand, when the predetermined data is transmitted at a second transmission speed lower than the first transmission speed, the predetermined time is measured at the time measured by the measuring unit. Then, in selecting a desired transmission speed or selecting a line release, if the time measured by the measuring means is equal to or longer than a second time longer than the first time, the first time Select the transmission speed of

[Embodiment] In an embodiment of the present invention described in detail below, in an image communication method capable of communicating at a plurality of transmission speeds, a line state check signal for determining a transmission speed is transmitted once prior to image transmission. On the receiver side, the optimum transmission speed is determined based on the reception result of the check signal, and the transmission side can be notified of the transmission speed. Accordingly, the transmitter can immediately proceed to image transmission at the transmission speed notified from the receiver.

Thereby, for example, both the transmitter and the receiver are 2400b / s, 4800b / s,
If it has a function to transmit at a transmission speed of 7200b / s or 9600b / s, a 9600b / s line status check signal (specifically, training / TCF signal, etc.) is transmitted first, and the receiver On the side, the optimum transmission speed can be determined based on the reception state of the line state check signal. This can be dealt with in the same manner even when a transmission function having a transmission speed of, for example, 12000 b / s, 14400 b / s, or 19200 b / s is provided.

As described above, even if the transmission function has a function of transmitting at a plurality of transmission speeds and the line condition is poor, the image transmission at the transmission speed proceeds with only one transmission of the line state check signal. Therefore, the time required to determine the optimum transmission speed can be significantly reduced as compared with the related art.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the overall configuration of an image communication system according to the present invention. As shown in the figure, in an image communication method in which communication is performed at any one of a plurality of transmission speeds, a line status check signal for determining a transmission speed is transmitted in advance prior to transmission of image information. The optimum transmission speed is determined based on the reception state of the check signal, and the transmission side is notified of the transmission speed.

A specific example is shown in FIG. In this drawing, it is assumed that both the transmitter and the receiver have a function of transmitting at transmission speeds of 2400 b / s, 4800 b / s, 7200 b / s, and 9600 b / s.

First, training / TC at 9600b / s as shown in Fig. 2
F signal is transmitted, but the receiver is S
The PD 24, that is, a signal instructing transmission of an image signal at 2400 b / s is transmitted. Compared with the procedure for the conventional facsimile machine to fall back to 2400 b / s (see FIG. 8 (2)), the advantages of this embodiment become clear.

In one embodiment of the present invention described in detail below, both the transmitter and the receiver conform to the CCITT recommendations V27ter and V3
It is assumed that the device is a facsimile machine. The instruction based on the reception result when the line status check signal (specifically, the training / TCF signal) is received is an instruction to perform image transmission at a transmission speed of V27ter / 2400b / s or V27ter.
・ Instruction to perform image transmission at a transmission speed of 4800b / s,
Alternatively, there is an instruction to transmit an image at a transmission speed of V29 / 7200 b / s, an instruction to transmit an image at a transmission speed of V29-9600 b / s, and an instruction to interrupt the transmission. Note that each of the above signals is in the HDLC format determined by CCITT recommendation T30. Also, as the signal name, SPDSTP, SPD24, S in the order of line disconnection instruction, 2400b / s instruction, 4800b / s instruction, 7200b / s instruction, 9200b / s instruction
Named PD48, SPD72, SPD96. Here, (FCF facsimile control field) may be set arbitrarily. Of course, this signal is 300b / s V21 modulated.

Embodiment 1 FIG. 3 is a block diagram showing an embodiment of a facsimile apparatus to which the present invention is applied.

In FIG. 1, reference numeral 2 denotes a telephone network used for data communication and the like, which is connected to a terminal of the line to control connection of a telephone switching network, switch to a data communication path,
Network control unit NCU (Network Control U
nit). The signal line 2a is a telephone line. The NCU 2 inputs the signal on the signal line 30a, and if the signal level is "0", the telephone line is connected to the telephone, that is, the signal line 2a is connected to the signal line 2b.
Connect to If the signal level of the signal line 30a is "1", the telephone line is connected to the image communication system 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.

 4 is a telephone.

Reference numeral 6 denotes a hybrid circuit for separating a transmission system signal and a reception system signal. That is, the transmission signal on the signal line 18a is transmitted to the telephone line via the NCU 2 via the signal line 2c. Further, the signal sent from the other side passes through the NCU 2, passes through the signal line 2c, and is output to the signal line 6a.

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

Reference numeral 10 denotes an encoding circuit which inputs data output to the signal line 8a and encodes the encoded data (MH (Modified Huffman)).
Encoding or MR (Modified Read) encoding)
The data thus output is output to the signal line 10a.

12, when a TCF signal transmission pulse is generated on the signal line 30b,
This is a TCF signal generation circuit for transmitting a TCF signal to the signal line 12a, that is, a "0" signal for 1.5 seconds.

Reference numeral 14 denotes a modulator that performs modulation based on the known CCITT recommendation V27ter (differential phase modulation) or V29 (quadrature modulation). The modulator 14 receives a signal on the signal line 30d, and determines a transmission speed based on the signal. Specifically, signal line 30
d is set to 2400b / s, 4800b / s, 7200b / s, 9600b / s corresponding to "0", "1", "2", "3",
The modulator 14 receives the signal on the signal line 30c, and when the signal level is “0”, receives the signal on the signal line 10a,
When the signal level is “1”, the signal of the signal line 12a is input, modulated, and the modulated data is output to the signal line 14a.

Reference numeral 16 denotes a modulator that performs modulation based on the known CCITT recommendation V21. The modulator 16 receives the procedural signal on the signal line 30e, modulates the signal, and outputs modulated data to the signal line 16a.

Reference numeral 18 denotes an adder circuit, which inputs signals on the signal lines 14a and 16a and outputs the result of addition on the signal line 18a.

Reference numeral 20 denotes a demodulator that performs demodulation based on the known CCITT recommendation V21. The demodulator 20 receives the signal on the signal line 6a, performs V21 demodulation, and outputs demodulated data to the signal line 20a.

A demodulator 22 performs demodulation based on the known CCITT recommendation V27ter (differential phase modulation) or V29 (quadrature modulation). The demodulator 22 receives the signal on the signal line 6a, performs demodulation,
The demodulated data is output to a signal line 22a. Demodulator 22 is signal line 3
A signal of 0g is input, and the transmission speed is determined by this signal. Specifically, the signal line 30g outputs signals "0", "1",
2400b / s, 4800b / s, 4800b / s,
Set to 7200b / s, 9600b / s.

A decoding circuit 24 receives demodulated data output to the signal line 22a and outputs the decoded (MH (Modified Huffman) decoding or MR (Modified Read) decoded) data to the signal line 24a. is there.

Reference numeral 26 denotes a recording circuit which inputs the decoded data output to the signal line 24a and sequentially performs recording for each line.

Reference numeral 28 denotes a TCF signal determination circuit, which inputs demodulated data output to the signal line 22a when a signal having a signal level "1" is output to the signal line 30f, that is, when a TCF signal is received,
The time of the actually received TCF signal is output to a signal line 28a, and the maximum time during which “0” data is continuously received is output to a signal line 28b.

 Reference numeral 30 denotes a control circuit that performs the following control.

First, the receiver has a function (hereinafter, referred to as a second mode) that determines an optimum transmission speed based on a reception result of a line state check signal (specifically, a TCF signal) and notifies the transmitter of the transmission speed. Whether you have
Notify the transmitter by NSF signal. This is, for example, NSF
This is performed by allocating specific bits (for example, 50 bits) of the FIF (facsimile information field) of the signal. That is, if the 50th bit of the FIF in the NSF signal is “0”, the receiver determines the optimal transmission speed based on the reception result of the line state check signal, specifically, the reception result of the TCF signal, and gives the transmission speed to the transmitter. Notification function (second mode)
If the 50th bit of the FIF in the NSF signal is “1”, the receiver determines the optimal transmission speed based on the line status check signal, specifically, the reception result of the TCF signal. To notify the transmitter of the transmission speed.

Then, the transmitter transmits the image signal at the optimum transmission speed specified by the receiver.

On the transmitter side, if the 50th bit of the FIF in the NSF signal sent from the receiver on the other side is "1", NS
"1" is set to the 50th bit of the FIF in the S signal.
That is, the transmitter declares to the receiver that it operates with the function according to the second mode. On the other hand, if the 50th bit of the FIF in the NSF signal sent from the partner receiver is “0”, the transmitter determines the 50th bit in the FIF of the NSS signal.
The bit is set to “0”. That is, the transmitter declares to the receiver that it does not operate with the function according to the second mode. That is, facsimile communication is performed in a procedure (first mode) according to the conventional CCITT recommendation T30.

The following is an explanation of the operation when the transceiver has a function according to the second mode.

The transmitter transmits the training signal / TCF following the NSS / TSL / DCS signal. Here, the TCF signal is "0" for 1.5 seconds.
Signal.

The receiver receives the training signal / TCF signal. The reception result of the TCF signal is determined by the TCF signal determination circuit 28, and the time of the actually received TCF signal and the maximum time of continuously receiving “0” data are recognized. Since the time is determined to be 1.5 seconds, the optimum transmission speed is determined here based on the maximum time during which “0” data is continuously received. When the time of the line status check signal corresponding to the TCF signal changes, it is necessary to measure the time of the actually received TCF signal.

The following is an example of the transmission speed at which the training / TCF signal is being received and the transmission speed at which transmission is instructed or the line is disconnected according to the maximum continuous "0" signal time received at that time. explain.

First, the training / TCF signal transmission speed is 9600b /
The case of s will be described. In this case, the maximum time for continuously receiving “0” data on the receiver side is, for example,
If it is 0.1 seconds or more, the transmission instruction at 9600 b / s
If it is longer than 1.0 second and less than 1.0 second, the transmission instruction at 7200 b / s
If it is longer than 0.8 seconds and less than 0.8 seconds, the transmission instruction at 4800 b / s
If it is longer than 0.6 seconds and shorter than 0.6 seconds, the transmission instruction at 2400 b / s
If it is less than seconds, an instruction to disconnect the line is issued to the transmitter.

Next, the training / TCF signal transmission speed was 7200b /
The case of s will be described. In this case, the maximum time for continuously receiving “0” data on the receiver side is, for example,
If it is longer than 1.4 seconds, the transmission instruction at 9600 b / s
If it is longer than 1.4 seconds and less than 1.4 seconds, the transmission instruction at 7200 b / s
If it is longer than 1.0 second and less than 1.0 second, the transmission instruction at 4800 b / s
If it is longer than 0.8 seconds and less than 0.8 seconds, the transmission instruction at 2400 b / s
If it is less than seconds, an instruction to disconnect the line is issued to the transmitter.

Next, the transmission speed of the training / TCF signal is 4800b /
The case of s will be described. In this case, the maximum time for continuously receiving “0” data on the receiver side is, for example,
If it is longer than 1.4 seconds, the transmission instruction at 7200 b / s
If the time is less than 1.4 seconds and less than 1.4 seconds, a transmission instruction at 4800 b / s is given to the transmitter if it is 0.8 seconds or more and less than 1.0, and a transmission instruction at 2400 b / s is given to the transmitter if it is 0.8 seconds or more. .

Next, the training / TCF signal transmission speed is 2400b /
The case of s will be described. In this case, the maximum time for continuously receiving “0” data on the receiver side is, for example,
If it is longer than 1.4 seconds, the transmission instruction at 4800 b / s
If it is longer than 1.4 seconds and less than 1.4 seconds, the transmission instruction at 2400 b / s
If it is less than this, an instruction to disconnect the line is issued to the transmitter.

After transmitting the NSS / TSI / DCS signal and the training / TCF signal, the transmitter proceeds to the transmission of the training / image signal at 9600b / s when receiving the SPD96 signal, that is, the transmission instruction signal at 9600b / s, When receiving the SPD72 signal, that is, the transmission instruction signal at 7200 b / s, the process proceeds to the transmission of the training / image signal at 7200 b / s, and the SPD48 signal, that is, 4800 b / s.
When the transmission instruction signal is received at 4800b / s, the process proceeds to the transmission of the training / image signal at 4800b / s, and the SPD24 signal, that is, 2
When the transmission instruction signal at 400 b / s is received, the process proceeds to the transmission of the training / image signal at 2400 b / s. When the SPDSTP signal, that is, the instruction signal of the line disconnection is received, the DCN (disconnect command) signal is transmitted. To release.

Thereafter, a facsimile transmission procedure based on the conventional CCITT recommendation T30 is performed.

4 (1) to 4 (3) show the control circuit shown in FIG.
The control procedure to be performed by 30 is shown.

 First, step S40 represents “beginning”.

In step S42, a signal of signal level “0” is output to the signal line 30a, and a CML (Connect Modemto Line) is output.
Turn off.

In step s44, it is determined whether facsimile transmission has been selected. When facsimile transmission is selected, the process proceeds to step S48. If facsimile transmission has not been selected, the process proceeds to step S46.

In step S46, it is determined whether facsimile reception has been selected. When facsimile reception is selected, the process proceeds to step S96. If facsimile reception has not been selected, the process proceeds to step S44.

In step S48, a signal of the signal level "1" is output to the signal line 30a, and the CML is turned on.

 In step S50, the pre-procedure is executed.

In step S52, the 50th bit of the FIF in the NSF signal is “1”, that is, the partner receiver determines the optimal transmission speed based on the reception result of the line state check signal, specifically, the TCF signal, It is determined whether the communication device has a function (second mode) of notifying the transmission speed. If the 50th bit of the FIF in the NSF signal is “1”, that is, if the above function is provided, the process proceeds to step S60. If the 50th bit in the FIF of the NSF signal is “0”, that is, if the above function is not provided, the process proceeds to step S54.

In step S54, a pre-procedure is executed. Here, when transmitting the NSS signal, the 50th bit of the FIF in the NSS signal is set to “0”.

 In step S56, image transmission is performed.

 Step S58 executes a post procedure.

In steps S54 to S58, the conventional CCITT recommendation T
Facsimile communication is performed according to a protocol according to 30.

In step S60, an NSS / TSI / DCS signal is transmitted. Here, the 50th bit of the FIF in the NSS signal is “1”.
Set to.

In step S62, a training / TCF signal for checking the line state is transmitted.

In steps S64 to S72, the result of receiving the signal from the receiver is determined. SPD9 from receiver
6, that is, when the transmission instruction signal of the training / image signal at 9600 b / s is received, the signal "3" is output to the signal line 30d, and the high-speed modem 14 is set to 9600 b / s (step S).
84).

When the SPD 72, that is, the training / image signal transmission instruction signal at 7200 b / s, is received from the receiver, a signal "2" is output to the signal line 30d, and the high-speed modem 14 is set to 7200 b / s (step S78) Also, when receiving the SPD48 from the receiver, that is, a training / image signal transmission instruction signal at 4800 b / s, a signal “1” is input to the signal line 30 d and the high-speed modem 14 is set to 4800 b / s. (Step S80).

When receiving the SPD 24 from the receiver, that is, the transmission instruction signal of the training / image signal at 2400 b / s, the signal “0” is output to the signal line 30 d and the high-speed modem 14 is set to 2400 b / s (step S82).

When receiving SPDSTP from the receiver, that is, a transition instruction signal for line disconnection, the line is released after transmitting the DCN signal (step S76).

In step S74, it is determined whether or not the transmission of the NSS / TSI / DCS signal and the training / TCF signal does not result in three attempts. If there is no response three consecutive times, a DCN signal is transmitted (step S76), and the line is released. If there is no non-response three consecutive times, the process proceeds to step S60.

In step S86, training / image signals are transmitted.

In step S88, it is determined whether there is a next original. If there is a next original, the process proceeds to step S92. If there is no next original, the process proceeds to step S90.

 In step S90, a post procedure is executed.

In step S92, it is determined whether there is a mode change. If there is a mode change, the process proceeds to step S60. Step S if no mode change
Continue to 94.

In step S94, it is determined whether there is a TCF signal transmission request from the receiver, specifically, for example, whether an RTP (retrain positive) signal or an RTN (retrain negative) signal has been received. If there is a TCF signal transmission request from the receiver, the process proceeds to step S60. If there is no TCF signal transmission request from the receiver, the process proceeds to step S86.

In step S96, a signal of the signal level "1" is output to the signal line 30a, and the CML is turned on.

In step S98, a pre-procedure is executed. Here, since it has a function of determining an optimal transmission speed based on the reception result of the line status check signal, specifically, the TCF signal, and notifying the transmitter of the transmission speed, the FIF of the NSF signal is "1" is set in the bit position.

In step S100, it is determined whether the 50th bit of the FIF in the NSS signal is “1”, that is, whether the transmitter has a function according to the second mode. NSS
If the 50th bit of the FIF in the signal is “1”, that is, if the transmitter has a function according to the second mode, the process proceeds to step S108. If the 50th bit of the FIF in the NSS signal is “0”, that is, if the transmitter does not have a function according to the second mode, the process proceeds to step S102.

 In step S102, a pre-procedure is executed.

 In step S104, an image signal is received.

 In step S106, a post procedure is executed.

In steps S102 to S106, facsimile communication is performed using a protocol according to the conventional CCITT recommendation T30.

In step S108, a TCF signal is received. After the reception of the TCF signal is completed, the signal on the signal line 28b is input, and the maximum time during which “0” data is continuously received is recognized.

In step S110, it is determined whether the transmission speed is 9600 b / s. When the transmission speed is 9600 b / s, the process proceeds to step S11. When the transmission speed is not 9600 b / s, the process proceeds to step S11.
Proceed to S150.

In steps S112 to S118, a check is made for the maximum time of continuous “0”. If this time is 1 second or longer, the SPD96 is transmitted, and the transmission of the training image signal of 9600 b / s is instructed to the transmitter (step S120), and the receiver outputs the signal "3" to the signal line 30g, and the high-speed modem 22 to 9600b
/ s is set (step s122).

If this time is 0.8 seconds or more and less than 1.0 second, it transmits spd72, instructs the transmitter to transmit a training / image signal of 7200 b / s (step S124), and the receiver outputs signal "2" to signal line 30g. Then, the high-speed modem 22 is set to 7200 b / s (step S126).

When this time is 0.6 seconds or more and less than 0.8 seconds, SPD48 is transmitted, and the transmitter is instructed to transmit a 4800 b / s training / image signal (step S128), and the receiver outputs a signal “1” to the signal line 30g. Then, the high-speed modem 22 is set to 4800 b / s (step S130).

When this time is 0.4 seconds or more and less than 0.6 seconds, SPD24 is transmitted, and the transmitter is instructed to transmit a 2400 b / s training / image signal (step S132), and the receiver outputs a signal “0” to the signal line 30g. Then, the high-speed modem 22 is set to 2400 b / s (step S134).

If this time is less than 0.4 seconds, it sends SPDSTP and instructs the receiver to open the line.

In step S138, a training / image signal is received.

In step S140, it is determined whether there is a next original. If there is a next original, the process proceeds to step S144.
If there is no next original, the process proceeds to step S142.

 In step S142, a post-procedure is executed.

In step S144, it is determined whether there is a mode change. If there is a mode change, proceed to step S148; otherwise, go to step S148.
Proceed to S146.

In step S146, the receiver sets the training / TCF
Is determined again. When the receiver wants to receive the training / TCF signal again, after transmitting the request signal, the process proceeds to step S148. Receiver is training / T
If you do not want to receive CF again, after sending a signal to that effect,
Proceed to step S138.

 In step S148, an intermediate procedure is executed.

In step S150, it is determined whether the transmission speed is 7200b / s. When the transmission speed is 7200 b / s, the process proceeds to step S152, and when the transmission speed is not 7200 b / s, the process proceeds to step S160.

In steps S152 to S158, a check is made for the maximum time of continuous “0”. If this time is equal to or longer than 1.4 seconds, the process proceeds to step S120, and the high-speed modem 22 is set to 9600 b / s. When this time is 1.0 second or more and less than 1.4 seconds, the process proceeds to step S124, and the high-speed modem 2 is set to 7200 b / s.
Set 2. When this time is 0.8 seconds or more and less than 1.0 second, the process proceeds to step S128, and the high-speed modem 22 reaches 4800 b / s.
If the time is 0.6 seconds or more and less than 0.8 seconds, the process proceeds to step S132, and the high-speed modem 22 is set to 2400 b / s. If this time is less than 0.6 seconds, the process proceeds to step S136, and the line is disconnected.

In step S160, it is determined whether the transmission speed is 4800b / s. When the transmission speed is 4800 b / s, the process proceeds to step S162, and when the transmission speed is 2400 b / s, the process proceeds to step S16.
Proceed to 8.

In steps S162 to S166, a check is made for the maximum time of continuous “0”. When this time is equal to or longer than 1.4 seconds, the process proceeds to step S124, and the high-speed modem 22 is set to 7200 b / s. If this time is equal to or longer than 1 second and shorter than 1.4 seconds, the process proceeds to step S128, and the high-speed modem is set to 4800 b / s. If this time is not less than 0.8 seconds and less than 1.0 second, the process proceeds to step S132, and the high-speed modem 22 is set to 2400 b / s.
If this time is less than 0.8 seconds, the process proceeds to step S136 to disconnect the line.

In steps S168 to S170, a check is made for the maximum time of continuous “0”. If this time is equal to or longer than 1.4 seconds, the process proceeds to step S128, and the high-speed modem 22 is set to 4800 b / s. If this time is equal to or longer than 1.0 second and shorter than 1.4 seconds, the process proceeds to step S132, and the high-speed modem 22 is set to 2400 b / s. If this time is less than 1.0, step S
Proceed to 136 to disconnect the line.

Embodiment 2 In the above embodiment, when a TCF signal is being received, the image transmission speed is determined based on the maximum continuous time of “0”. The transmission speed may be determined in another direction, for example, by considering the total “0” time.

Embodiment 3 In the above embodiment, the transmission speed was 2400b / s, 4800b / s.
s, 7200b / s, 9600b / s (that is, those defined in CCITT Recommendations V27ter and V29) have been described.

However, 12000b, which is a provisional recommendation in CCITT Recommendation V33
The present invention may also be applied to a transmission speed of 19200 b / s, which is expected to be recommended in the future, in addition to / s and 14400 b / s.

In current CCITT Recommendation T30, 12000b / s, 14400b / s,
The bit of the transmission speed at 19200b / s is DIS (Digital Identification) / DTC (Digital Transmission Command) / DCS (Digital Command)
Since it is not assigned to a signal, it is necessary to assign a bit to a signal representing a non-standard function, specifically, a NSF (non-standard device) / NSC (non-standard device command) / NSS (non-standard device setting) signal. .

Embodiment 4 In the above embodiment, the negotiation as to whether or not the terminal has the function according to the present invention was performed by bit assignment to a signal representing a non-standard function, specifically, an NSF / NSC / NSS signal. . However, if this function is recommended at the meeting of the CCITT, it is of course possible to assign a bit to the DIS / DTC / DCS signal.

In the above embodiment, after receiving the line state check signal, the instruction of the transmission speed is set to the demodulated TCF.
The signal was received and the judgment was made based on the data. That is,
The determination was made based on the data "0" and "1" resulting from the demodulation of the data by the modem. However, it is also possible to check the magnitude of the error signal on the modem side, for example, without relying on this determination procedure, and to determine the above instruction based on this magnitude.

 The following is an example of the operation when the determination is made on the modem side.

FIG. 5 shows an example of a PLL automatic equalizer with a square error accumulator.

FIG. 6 shows a detailed configuration of the equalizer 300 shown in FIG.

FIG. 7 shows the ID filter (Integrat and
3 shows a detailed configuration of the Dump Fiter 313.

In FIG. 5, Ri is a demodulated complex signal, which is supplied from the demodulation unit of the receiving system. Reference numeral 300 denotes a line equalizer, which restores the data distorted on the line to the original transmission state. Yi = Aie ^jθi represents the i-th output of the equalizer 300 in polar coordinates.

303 is a multiplier, which is an output e of the complex number generator 305.
^-Jeishitaai an equalizer output ^Yi = Aie jθi are multiplied, is output as ^{Zi = Yie -jθi = Aie j (} θi-φi).

Reference numeral 310 denotes a determiner, which is determined as a code point i which is closest to the received signal point output from the multiplier 303.

Numeral 311 denotes a subtracter, which subtracts a decision point from a received signal point, and outputs an error signal Ei = Zi-i.

Subsequently, the error signal Ei is the output e of the complex number generator 302.
^Multiplied by ^jφi to obtain ^{Eie jφi, which} is fed back to the equalizer 300. Here, ^ejφi is a phase correction amount.

On the other hand, the output Ei = Zi-i of the subtractor 311 goes to the IDF 313 via the square circuit 312 of the absolute value. That is, the squaring circuit 31
In step 2, the square of the distance between the received signal point and the determination point is obtained.

The output of IDF313 the squaring circuit 312 is output as the accumulated number of times set is designed vehicles (N baud periods) Q _L subsequently. The Q _L approaches zero the less well circuit noise amount line equalization rate, the value of the more inferior circuit noise amount line equalization rate reversed Q _L increase.

Next, the operation of the phase control unit surrounded by a dotted line in FIG. 5 will be described. Reference numeral 309 denotes a divider, and as a result of the division between Zi and i, ej ^(θi−φi) is approximately obtained. An imaginary part extractor 308 outputs sin (θi−φi). sin
(Θi−φi) is approximately θi−φi when θiφi
Is equal to 306 and 307 are VCs that are components of a normal PLL
O and a low-pass filter that output a phase value −φi to cancel the input phase error. Subsequently, e is generated by the complex number generators 305 and 302 and the complex conjugate generator 304.
^−jφi , e ^{+ jφi} are output, and multipliers 303 and 3 are output, respectively.
01 is input, canceling the phase error of the whole system.

FIG. 6 shows a configuration diagram of the equalizer. Generally, the equalizer is a transversal filter, 400 is a delay element for delaying the reception data Ri for a certain time, and 401 is a tap gain [C _{-N to} C _N ] to be multiplied by the delay reception data immediately above.
An adder 403 calculates the sum of the multiplication result of the delay reception data and the tap gain, and as a result, the equalizer output signal
Yi is given by the following equation.

This equalizer calculates each tap gain based on the received data.
By successively calculating the following formula using the MES (Mean Square Error) method, it adapts to the inverse characteristics of the line.

Cl ^{i + 1} = Cl ⁱ -αR _il ^{* Eie jφi Expression} (2) Cl ^{i + 1} : Tap gain value calculated at the ( ^{i + 1} ) th time ^{Eie jφi} : Feedback signal α from multiplier 301 in FIG. 5: Convergence Coefficient (Generally α << 1) In FIG. 7, reference numeral 500 denotes an adder, 501 denotes a delay unit, and 502 denotes a sampler.

First, the output of the absolute value squaring circuit 312 in FIG. This operation is repeated every output cycle of the squaring circuit 312, that is, every baud cycle. In the sampler 502, the output of the adder is sampled for each value N determined by the designer, and subsequently the delay unit 50 is sampled.
The value of 1 is initialized. In other words, in this circuit, the squaring circuit 312
Are added N times.

Finally, the PLL with squared error accumulator described so far
Three or less methods for determining an equalization rate by an automatic equalizer and determining a transmission rate based on the determination result will be described below.

(1) Method used during training Using CCITT recommendation V27ter segment 5 (signal 8SI with scrambled continuous "1") and V29 segment 4 (scrambled data "1" 48SI), respectively, the cumulative number in FIG. N is set to 8,48 each. Here, the case where V29 is used will be described as an example.

First, an error rate vs. SN ratio curve of the V29 modem is drawn, and an SN ratio with respect to a user allowable error rate is obtained. Determined by simulation square error cumulative value Q _L for the obtained SN ratio. This value and T _H. If the value of Q _L in actual facsimile communication is smaller than T _H 9600 b as the transmission rate / s
Select, 7200 b / s as the transmission rate is greater than T _H
Select Therefore, if the above method is used, the transmission rate can be determined by one training.

Also, advance obtained by simulation the value when the equalizer diverges, the value T _div of Q _L if put its value as T _div
When it is larger, it is also possible to save the tap coefficients of the equalizer and shift to retraining.

The above method is also applicable to V27ter,
There are many transmission speeds in ultra-high-speed modems such as 14400b / s and 19200b / s.
The optimal transmission rate can be determined by training once.

(2) Method of using TCF In facsimile communication, scrambled "0" is transmitted as a TCF signal.
Q _L can also be determined. In this case, the number of times of accumulation can be longer than that of the above-mentioned method (1), so that the equalization ratio can be determined more accurately. If you use this method,
(1) Similar to the method of determining by simulation-threshold value T _H.

〔The invention's effect〕

As described above, in the present invention, when predetermined data transmitted from a communication partner is received to determine a transmission speed prior to transmission of image information, the predetermined data is transmitted from demodulation means. Based on the demodulated output time, select a desired transmission speed among a plurality of transmission speeds, or select to open the line '', so that the transmission speed according to the line state is selected, or It can be determined in a short time that the line is released if the line state is poor.

Further, according to the present invention, `` when the predetermined data transmitted from the communication partner to determine the transmission speed prior to the transmission of the image information is received, the time measured by the measurement unit is Based on the selected transmission speed, select a desired transmission speed among the plurality of transmission speeds, or select a line release, notify the transmission side of the selected result, and further receive image information at the desired transmission speed. After performing, when there is a next original, when the predetermined data transmitted again prior to the next original is received, the plurality of transmissions are performed based on the time measured by the measuring unit. Select the desired transmission speed among the speeds, or select the release of the line, and notify the transmitting side of the selected result. It can be determined in a short time over de.

Further, in the present invention, "when the predetermined data is transmitted at a first transmission speed", "if the time measured by the measuring means is equal to or longer than a first time, the first "Select the transmission speed", and "if the predetermined data is transmitted at a second transmission speed lower than the first transmission speed", "the time measured by the measuring means is the If the time is equal to or longer than a second time longer than the first time, the first transmission speed is selected. "Therefore, the second transmission speed at which the predetermined data transmission speed is lower than the first transmission speed is selected. Even if it is the speed, the first transmission speed can be appropriately selected for transmitting the image information depending on the line condition.

In particular, the transmission speed will be greatly increased in the future (for example, the transmission speed of G3 facsimile is reduced from the current 4 types to 7 types)
It is expected that the number will increase, but a greater effect can be obtained at this time.

[Brief description of the drawings]

FIG. 1 is a diagram showing the entire image communication system according to the present invention, FIG. 2 is a diagram showing a specific procedure in FIG. 1, and FIG. FIG. 4 (1) to FIG. 4 (3) are block diagrams, and the control circuit shown in FIG.
FIG. 5 is a flowchart showing a control procedure to be executed by 30; FIG. 5 is a block diagram showing an example of a PLL automatic equalizer with a square error accumulator; FIG. FIG. 7 is a diagram showing a configuration of the ID filter 313 shown in FIG. 5, and FIGS. 8 (1) to 8 (3) are diagrams showing an example of a procedure of a conventionally known facsimile apparatus. It is. 12 TCF signal generation circuit, 14 V27ter or V29 modulator, 16 V21 modulator, 20 V21 demodulator 22 V27ter or V29 demodulator, 300 equalizer 313 ID filter .

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 1/32-1/36 H04L 1 / 00,1 / 08-1/24

Claims (1)

(57) [Claims] An image communication apparatus having demodulation means for demodulating a received signal and performing communication at any one of a plurality of transmission speeds, wherein when a communication partner transmits predetermined data,
A measuring unit for measuring a time when the predetermined data is demodulated and output from the demodulating unit, in a first communication mode according to a function of a transmitting side as a communication partner, or a second communication Control means for determining whether to perform communication in a mode, wherein the control means: (a) in the first communication mode, receives image information in accordance with a recommendation of T30; (b) in the second communication mode In receiving the predetermined data transmitted from the communication partner to determine the transmission speed prior to the transmission of the image information, based on the time measured by the measuring means, Select a desired transmission speed among certain transmission speeds or select a line release, notify the transmitting side of the selected result, and further receive image information at the desired transmission speed. Later, when there is a next original, when the predetermined data transmitted again prior to the next original is received, based on the time measured by the measuring unit, the plurality of transmission speeds are determined. Select a desired transmission speed among them, or select release of the line, and when notifying the transmitting side of the result of the selection, when the predetermined data is transmitted at the first transmission speed, Based on the time measured by the measuring means, to select a desired transmission speed, or to select the release of the line, if the time measured by the measuring means is a first time or more, The first
On the other hand, when the predetermined data is transmitted at a second transmission speed lower than the first transmission speed, based on the time measured by the measuring means, In selecting a desired transmission speed or selecting to release a line, if the time measured by the measuring means is equal to or longer than a second time longer than the first time, the first transmission speed is determined. An image communication device characterized by selecting: