JPS6331366A - Method for controlling echo protection tone in facsimile equipment - Google Patents

Abstract

PURPOSE:To shorten the communication time by adding an echo protection tone to prevent the convergence uncertainty of MODEM if the acquired line is a satellite communication line and preventing the echo protection tone from being added if it is a land line. CONSTITUTION:A timer is started just after the completion of transmission of a training check signal TCF. A threshold T is set between several tens ms and 520ms, and a measured time TD of the timer is compared with the threshold T when a reception preparation confirming signal CFR is received. If the time TD is equal to or longer than the threshold T, the acquired line is discriminated as a satellite line, and the echo protection tone is so added that the head of a message MESS in a phase C may be dropped out by the release time of an echo suppressor. If the time TD is shorter than the threshold T it is discriminated as a land line, and the head of the signal of the message MESS is not dropped out because the echo suppressor is not provided, and the echo protection tone is not added.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an echo protection tone control method for a facsimile machine.

[Conventional technology]

Conventionally, the echo protection I--on control method for facsimile machines is based on V29 mode (9600 bps, 7200 bps) at the start of Phase C specified in CCITT Recommendation T30.
Since the recommendation does not specify whether or not to add echo protection tones (bps), the presence or absence of echo protection tones varies depending on the manufacturer or model of facsimile equipment, and which Also, unambiguous,
It is fixedly divided into those that add an echo protection tone and those that do not.

Next, the role of the echo protection tone will be explained with reference to the drawings.

FIG. 3 is a block diagram of an example of a facsimile communication system including a conventional satellite line.

In Figure 3, FS is a facsimile transmitting terminal, FR is a facsimile receiving terminal, and H5 and HR are 4-wire-2, respectively.
Herans (hybrid for line conversion), XS, and XR are echo suppressors installed at international exchange offices, and L5. LR is a forward transmission path and a reverse transmission path of the satellite link, respectively.

The operation of the echo suppressor XR is such that when the signal level on the forward transmission line Ls is higher than the signal level on the reverse transmission line LR, the echo suppressor control unit CNTa operates and the changeover switch SWR inserts the attenuator AVR. set in the direction.

This prevents the signal on the forward transmission path Ls from going around to the reverse transmission path LR and becoming an echo due to leakage from the pipe red transformer HR.

On the other hand, the operation of the echo suppressor X5 on the transmitting side is exactly the same.

FIG. 2 is a diagram showing a communication procedure according to CCITT Recommendation T3 Recommendation A30.

In FIG. 2, TCP is a training check signal that instructs the facsimile transmitting terminal Fs to enter the training check field to the facsimile receiving terminal PR. This is a reception readiness confirmation signal requesting to move on to the message MESS.

Message MESS from sending reception preparation confirmation signal CFR
The time diagram in the timing section of sending out is shown in Figure 4 (a'
) and (b). FIG. 4(a) shows the case where an echo protection tone is added to the echo protection tone transmission period TEP, and FIG. 4(b) shows the case where it is not added.

In FIGS. 4(a) and 4(b), TTR is a high-speed modem training signal transmission period, and TPIX is a picture information transmission period.

In the facsimile communication system shown in FIG.
When the reception preparation confirmation signal CFR shown in the figure is returned, the echo suppressor Xs operates and the attenuator AV of the forward direction transmission path L3
The changeover switch SWS is set in the direction in which s is set.

In this state, if we pay attention to the timing at which the message MESS starts to be transmitted in the forward direction, as shown in FIGS. 4(a) and <b>, we can see that the time for the echo suppressor The message M
This results in the head of the ESS being missing.

In this case, as shown in FIG. 4(a), if an echo protection tone (section indicated by the echo protection tone transmission section TεP) is added, even if the beginning of the echo protection tone is missing, there will be no echo protection tone. Although this does not cause any problems, there is a case where a high-speed modem training signal (section indicated by the high-speed modem training signal transmission section TTR) suddenly arrives without an echo protection tone being added, as shown in FIG. 4(b). In this case, the modem of the receiving terminal may not be able to converge due to the loss of the beginning of the high-speed modem training signal.

[Problem that the invention seeks to solve]

In the conventional echo protection tone control method for facsimile machines described above, it is fixed that the echo protection tone is either uniformly added or not added.
When not adding an echo protection tone, such as on a satellite line,
The first drawback is that the modem of the receiving terminal may not be able to converge due to the influence of the echo suppressor.

On the other hand, in a system without echo suppressor equipment, such as a land line, if the transmitting terminal uniformly adds echo protection tones, the echo protection tones do not serve any original function and become mere redundant signals. A second drawback is that communication time is wasted by the time it takes to send the echo protection tone (approximately 200 seconds).

SUMMARY OF THE INVENTION An object of the present invention is to provide an echo protection tone control method for a facsimile machine that prevents modem convergence uncertainty on a line that is equipped with an echo suppressor and that does not waste communication time on a line that is not equipped with an echo suppressor. It's about doing.

[Means for solving problems]

The echo protection tone control method for a facsimile machine of the present invention measures the time from sending out a training check signal of a facsimile machine to receiving a reception readiness confirmation signal from the other party's terminal in compliance with CCITT Recommendations T4 and T30. When the time is longer than or equal to the preset time, the above C
It is configured to add an echo protection tone immediately before the training signal at the start of Phase C as defined in CITT Recommendation T30.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a flowchart for explaining the operation of a facsimile machine according to an embodiment of the present invention.

The operation of the facsimile machine will be described below with reference to FIGS. 1 and 2. In FIG. 1, the portion surrounded by broken lines is an additional block according to the present invention.

As shown in FIGS. 1 and 2, the timer TM is started immediately after the sending of the training check signal TCF is completed. By counting the time of the timer TM after receiving the reception preparation confirmation signal CFR, it is determined whether the line between the transmitting and receiving terminals is a land line or a satellite line.

Immediately after sending the training check signal TCP,
The time it takes for the reception preparation confirmation signal CFR to arrive corresponds to the time the signal travels back and forth on the Habo line. This time is greater than 520-s for satellite links, while for land links it is typically less than a few tens of meters. Therefore, as a criterion for determining whether the timer TM is a land line or a satellite line, a threshold T is set between several 10-s and 520-s, and when the reception preparation confirmation signal CFR is received, the timer TM
By comparing To and T at the time of measurement, lines can be distinguished.

That is, if To≧T, it is determined that the line is a satellite line, so an echo protection tone is added so that the beginning of the message MESS in phase C may be lost depending on the recovery time of the echo suppressor.

On the other hand, in the case of T o < T, it is determined that the line is a land line, so there is no echo suppressor equipment, and therefore, no echo protection tone is added because the beginning of the signal in the message MESS will not be lost.

Incidentally, the timer TM can be easily realized by software using a microprocessor, and the control of whether or not to add an echo protection tone is usually performed by the communication sub-book section that controls the communication procedure as shown in Fig. 2 described above. This can be achieved by giving commands to the modem from

〔Effect of the invention〕

As explained above, in the echo protection tone control method for a facsimile machine of the present invention, the facsimile transmitting terminal measures the time from the completion of transmission of the training check signal to the reception of the reception preparation confirmation signal, so that the acquired line is connected to satellite communication. Determines whether the line is a land line or a land line, adds an echo protection tone in the case of a satellite communication line to prevent modem convergence uncertainties due to missing heads in the high speed modem training signal, and, in the case of a land line, By not adding an echo protection tone, there is an effect that the communication time can be shortened by the echo protection tone transmission time (approximately 200 seconds).

[Brief explanation of the drawing]

FIG. 1 is a flow chart for explaining the operation of a facsimile machine according to an embodiment of the present invention, and FIG.
Figure 3 is a diagram showing an example of a facsimile communication system including a conventional satellite line, and Figures 4(a) and <b> are facsimile communications in Figure 3. FIG. 3 is a time diagram for explaining the operation of the system. AVs, AV,...attenuator, CFR...reception preparation confirmation signal, CNTs, CNTR...echo suppressor control unit, Fs...facsimile transmission terminal, F5...
Facsimile receiving terminal, H5, HR...Hybrid transformer, L5...Forward transmission line, LR...Reverse transmission line, MESS...Message, SWS, SWR
...Selector switch, T...Threshold value, TCP...
・Training check signal, TM...timer, TD
...At the time of measurement, TCP...Echo protection tone sending section, TTR...High speed modem training signal sending section,
T PIX...Manga 1 Figure Fs7:F. ' Figure 2-Figure 4

Claims (1)

[Claims] The time from the transmission of the training check signal of the facsimile machine conforming to CCITT Recommendations T4 and T30 to the reception of the reception readiness confirmation signal from the other party's terminal is measured, and when the measurement result is longer than or equal to the preset time, the CCI
An echo protection tone control method for a facsimile machine, characterized in that an echo protection tone is added immediately before a training signal at the start of phase C specified in TT Recommendation T30.