JPH0478221B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an echo protection tone control method for facsimile equipment.

[Conventional technology]

Conventionally, the echo protection tone control method for facsimile equipment is based on Phase C specified in CCITT Recommendation T30.
V29 mode at the start (9600bps,
The recommendation does not specify whether or not to add an echo protection tone (7200bPS), so whether or not an echo protection tone is added varies depending on the manufacturer or model of facsimile equipment. The cases are also uniquely and fixedly classified into those with an echo protection tone added and those without.

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, F _S is a facsimile sending terminal;
F _R is a facsimile receiving terminal, H _S and H _R are respectively hybrid transformers for 4-wire → 2-wire conversion, X _S ,
X _R is an echo suppressor installed at an international exchange office.
L _S and L _R are the forward transmission path and reverse transmission path of the satellite link, respectively.

The operation of the echo suppressor X _R is based on the forward transmission path.
When the signal level of L _S is higher than the signal level of reverse direction transmission path L _R , the echo suppressor control unit
CNT _R operates and the changeover switch SW _R changes to the attenuator AV _R.
is set in the direction of insertion.

This prevents the signal on the forward transmission line L _S from going around to the reverse transmission line L _R and becoming an echo due to leakage from the pie-bred transformer _HR .

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

FIG. 2 is a diagram showing a communication procedure based on CCITT recommendation T30.

In Fig. 2, TCF is a training check signal that instructs the facsimile transmitting terminal F _S to the facsimile receiving terminal F _R to enter the training check field, and CFR is a training check signal sent from the receiving side to the transmitting side because reception preparations have been completed. C
This is a reception readiness confirmation signal requesting that the message be transferred to MESS.

Message from sending reception readiness confirmation signal CFR
The time diagram in the timing section of MESS transmission is as shown in FIGS. 4a and 4b. Figure 4a shows the echo protection tone in the echo protection tone transmission section T _EP
Figure 4b shows the case where it is not added.

In FIGS. 4a and 4b, T _TR is a high-speed modem training signal transmission section, and T _PIX is an image information transmission section.

In the facsimile communication system shown in Fig. 3, when _the reception readiness confirmation signal _CFR shown in Fig. 4 is returned, the echo _suppressor SW _S is set.

In this state, paying attention to the timing at which the message MESS starts to be transmitted in the forward direction shown in FIGS. _4a and 4b, we can see that the time for the _{echo suppressor} The head of the message MESS will be missing until the setting is restored to not insert the message.

In this case, as shown in Figure 4a, if an echo protection tone (section indicated by the echo protection tone transmission section _TEP ) is added, there will be no problem even if the beginning of the echo protection tone is missing. Although it does not occur,
As shown in Figure 4b, if the high-speed modem training signal (the section indicated by the high-speed modem training signal transmission section T _TR ) suddenly arrives without adding an echo protection tone, the high-speed modem training signal If the head is missing, the receiving terminal's modem may not be able to converge.

[Problem that the invention seeks to solve]

The conventional echo protection tone control method for facsimile equipment described above is fixed to either add echo protection tones uniformly or not add them, so echo protection tones are not added on satellite lines etc. 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 where there is no echo suppressor equipment, such as a land line, if the transmitting terminal uniformly adds an echo protection tone, the echo protection tone does not serve any original function and becomes a mere redundant signal, causing the echo Protection tone transmission time (approx.
The second drawback is that communication time is wasted by 200 ms).

An object of the present invention is to prevent modem convergence uncertainties on a line equipped with an echo suppressor, and
To provide an echo protection tone control method for a facsimile device that does not waste communication time on a line without echo suppressor equipment.

[Means for solving problems]

The echo protection tone control method for a facsimile device of the present invention measures the time from the transmission of a training check signal of the facsimile device to the reception of a reception readiness confirmation signal from the other party's terminal in accordance with CCITT Recommendations T4 and T30. When the time is longer than or equal to the set time, an echo protection tone is added immediately before the training signal at the start of Phase C specified in CCITT 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 apparatus according to an embodiment of the present invention.

The operation of the facsimile device 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 measuring 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.

The time from immediately after sending the training check signal TCF until the receiving preparation confirmation signal CFR arrives corresponds to approximately the time for the signal to travel back and forth on the line. This time is greater than 520ms for satellite links, while for land links it is typically several tens of ms
It is as follows. Therefore, the criterion for determining whether it is a land line or a satellite line using the timer TM is several tens of milliseconds.
When the threshold value T is set for 520ms and the reception preparation confirmation signal CFR is received, the timer TM measures
By comparing T _D and T, lines can be distinguished.

That is, if T _D ≧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, if T _D <T, it is determined that it is a land line, so there is no echo suppressor equipment, and therefore,
Echo protection tones are not added because the beginning of the signal in the message MESS is not lost.

Note that the timer TM can be easily implemented using software using a microprocessor, and control of whether or not to add an echo protection tone is usually performed using communication control that controls communication procedures as shown in Figure 2 above. This can be achieved by giving commands to the modem from the computer.

〔Effect of the invention〕

As explained above, in the echo protection tone control method for a facsimile device of the present invention, the facsimile transmitting terminal measures the time from the completion of transmitting the training check signal to the reception of the reception preparation confirmation signal, so that the acquired line can be used for 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 the echo protection tone, there is an effect that the communication time can be shortened by the echo protection tone transmission time (approximately 200 ms).

[Brief explanation of the drawing]

Fig. 1 is a flowchart for explaining the operation of a facsimile device according to an embodiment of the present invention, Fig. 2 is a diagram showing a communication procedure based on general CCITT recommendation T30, and Fig. 3 is a flowchart for explaining the operation of a facsimile device according to an embodiment of the present invention. FIGS. 4a and 4b are time charts for explaining the operation of the facsimile communication system of FIG. 3. FIGS. AV _S , AVR _... Attenuator, CFR ... Reception preparation confirmation signal, CNT _S , CNT _R ... Echo suppressor control unit, F _S ... Facsimile transmitting terminal, F _R ... Facsimile receiving terminal, H _S , H _R ...Hybrid transformer, L _S ... Forward transmission line, L _R ... Reverse transmission line, MESS ... Message, SW _S , SW _R ...
Changeover switch, T...Threshold value, TCF...Training check signal, TM...Timer, T _D
...At the time of measurement, T _EP ...Echo protection tone transmission section, T _TR ...High speed modem training signal transmission section, T _PIX ...Picture information transmission section, X _S , X _R ...Echo suppressor.

Claims (1)

[Claims] 1 Measure the time from the transmission of the training check signal of a facsimile device that complies with CCITT Recommendations T4 and T30 to the reception of the reception readiness confirmation signal from the other party's terminal, and if the measurement result is longer than or equal to the preset time, the above CCITT Recommendation T30 An echo protection tone control method for a facsimile apparatus, characterized in that an echo protection tone is added immediately before a training signal at the start of phase C defined in .