JPS6249778A - Facsimile equipment - Google Patents

Abstract

PURPOSE:To decrease transmission errors even when the line noise increases during the transmission of a modulated picture signal by so constituting the titled system that the transmission level of a training check signal is made lower than that of the modulated picture signal. CONSTITUTION:The output signal from a picture signal reading part 1 is encoded by an encoding part 2, modulated by a modulating part 3, and transmitted via a level adjusting circuit 4 to a line control part 5 which provides an interface with a telephone line. The level adjusting circuit 4 has a constitution of voltage divider consisting of a resistor 8, a switching element 10 and a resistor 9. During the transmission of the training check signal, a control part 6 controls to turn the element 10 on, to lower the output level of a modulating part 3, and thereafter transmits the signal to a line through the part 5. When transmitting a modulated picture signal, the part 6 lets the element 10 turn off, so that the signal is transmitted to the line being of a prescribed level. In such a way, even when the line noise increases during the transmission of the modulated picture signal B, the errors that may occur on the reception-side are decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a facsimile device that sends an image signal to a communication line. In particular, the present invention relates to a facsimile transmitter that transmits a training check signal prior to transmitting an image signal and changes the modulation speed and other factors of subsequent image signals depending on the situation on the receiving side of the training check signal.

〔overview〕

The present invention is a facsimile device in which a training check signal is transmitted at a lower level than an image signal, and subsequent image signals are transmitted at a predetermined level, thereby reducing transmission errors in image signals. .

[Conventional technology]

Conventionally, Group 3 facsimile devices specified by CCITT Recommendation To have an image signal reading section, an encoding section that encodes the output signal of the image signal reading section, and a modulation section that modulates the output of this encoding section. As shown in FIG. is demodulated on the receiving side and checked for transmission errors to check the level of noise on the telephone line.If there are no transmission errors, the receiving side returns an acknowledgment CFR, and if there are transmission errors, A negative response FTT is sent back.

On the transmitting side, if a positive response CFR is received, it is determined that there is little noise on the telephone line, and the modulated image signal B is sent out at the same modulation rate as the training check signal A, and if a negative response FTT is received, the telephone line is It is determined that there is a lot of noise on the line, and the modulated image signal B is sent out at a lower modulation speed than the training check signal A. Since a modulated image signal with a slow modulation speed is less susceptible to noise, transmission errors can be reduced.

[Problem that the invention seeks to solve]

The above-mentioned conventional facsimile device obtains a positive response CFR for the training check signal A, and while transmitting the modulated image signal B at the same speed, the stationary noise level of the line increases or random noise occurs. The disadvantage is that transmission errors are likely to occur if

SUMMARY OF THE INVENTION It is an object of the present invention to provide a facsimile apparatus which solves the above-mentioned conventional drawbacks and can prevent transmission errors from occurring even if noise on a line during image signal transmission increases.

[Means for solving problems]

The present invention includes an image signal reading section, an encoding section that encodes the output of the image signal reading section, a modulation section that modulates the output of the encoding section, and a telephone line connected to the output of the modulation section. A level for adjusting the level of a signal passing between the output of the modulation section and the line control section in a facsimile machine equipped with a line control section that interfaces with the above, and a control section that controls the operation of each of the above sections. An adjustment circuit is provided, and the control section controls the level adjustment circuit so that the output of the modulation section is attenuated and sent to the line while the training check signal is being sent out, and is sent out to the line at a predetermined level when the image signal is sent out. It is characterized in that it includes means for.

[For production]

While the training check signal is being sent out, the level adjustment circuit attenuates the output of the modulation section and sends the signal to the line, and when sending out the image signal, it is sent out at a predetermined level, thereby preventing line noise from increasing while the image signal is being sent out. transmission errors are reduced.

〔Example〕

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

FIG. 1 is a block diagram showing one embodiment of the present invention.

That is, an image signal reading section 1, an encoding section 2 that encodes the output signal of the image signal reading section 1, a modulation section 3 that modulates the output of the encoding section 2, and a control section that is connected to the output of the modulation section 3 and controlled. a level adjustment circuit 4 that attenuates the output of the modulation section 3 under the control of the section 6 and outputs it to the line control section 5;
It is comprised of a line control section 5 that is connected to the output of the telephone line and interfaces with the telephone line, and a control section 6 that controls the operations of the above-mentioned sections. The level adjustment circuit 4 configures a voltage divider with a resistor 8, a switching element 10, and a resistor 9.
When the switching element 10 is on, the level of the output signal 100 of the modulation section 3 is lowered by the voltage division ratio of the resistors 8 and 9, and is inputted to the line control section 5.

While the training check signal A is being sent out, the switching element 10 is turned on under the control of the control section 6 to lower the output level of the modulation section 3, and then the line control section 5
When transmitting the modulated image signal B to the line, the switching element 10 is turned off so that the modulated image signal B is sent to the line at a predetermined level.

The facsimile receiver 7 receives the training check signal A.
If it demodulates and detects an error, it returns a negative response FTT,
If there is no error, a positive response CFR is returned, and when the transmitting side receives a positive response CFR, it sends out a modulated image signal B at the same modulation rate as the training check signal A, and a negative response F.
When receiving TT, the modulated image signal B is sent out at a slow modulation speed, as in the conventional case.

However, in this embodiment, since the sending level of the modulated image signal B is higher than the sending level of the training check signal A, even if line noise increases during the transmission of the modulated image signal B, the noise will be generated on the receiving side. This has the effect of reducing the number of errors that occur.

If there is a large amount of noise when transmitting the training check signal A, an error will be detected on the receiving side, and a negative response FTT will be sent back, making it possible to prevent errors by transmitting the modulated image signal B at a slow modulation speed. In this case as well, since the transmission level of the modulated image signal B is set to the training check (t) and the transmission level of the signal A is also high, it is possible to reduce the occurrence of reception errors when noise increases, etc.

FIG. 2 is a circuit diagram showing the configuration of the level adjustment circuit 4 in another embodiment of the present invention. In this case, the differential amplifier 23 and the resistors 21 and 22 constitute an inverting amplifier, and the resistor 2
0 is connected in parallel to the resistor 21 through the analog gate 24, and the amplifier gain is controlled by turning the analog gate 24 on and off.

〔Effect of the invention〕

As explained above, in the present invention, the sending level of the training check signal is configured to be lower than the sending level of the modulated image signal, so that when line noise increases during transmission of the modulated image signal, This also has the effect of reducing transmission errors.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a circuit diagram showing a configuration example of a level adjustment circuit in another embodiment of the present invention. FIG. 3 is a diagram showing the flow of signals sent and received by a facsimile machine. 1... Image signal reading section, 2... Encoding section, 3...
Modulation section, 4... Level adjustment circuit, 5... Line control section, 6... Control section, 7... Facsimile receiver, 8.
9...Resistor, 10...Switching element, 11...
・Facsimile transmitter, 20-22...Resistor, 23・
...Differential amplifier, 24...Analog gate, A...
Modulated training check signal, B...modulated image signal. Patent applicant: NEC Corporation.

Claims (1)

[Claims] (1) Image signal reading section (1) and encoding section (2) that encodes the output of this image signal reading section
a modulation section (3) that modulates the output of this encoding section; a line control section (5) that is connected to the output of this modulation section and interfaces with the telephone line; and a control section that controls the operation of each of the above sections. The facsimile apparatus includes a level adjustment circuit (4) that adjusts the level of a signal passing between the output of the modulation section and the line control section, and the control section is configured to perform a training check. A facsimile apparatus comprising means for controlling the level adjustment circuit so that the output of the modulation section is attenuated and sent to the line while the signal is being sent out, and the output is sent out to the line at a predetermined level when the image signal is sent out.