JPH0431617B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a facsimile procedure interruption signal detection device, and particularly to one that prevents deterioration in the image quality of a facsimile image during detection.

[Conventional technology]

The CCITT recommendation stipulates that the carrier frequency of the facsimile image signal be 2100Hz.
Therefore, according to this rule, if a frequency component around 1638Hz is included in the transmission baseband signal of a facsimile image signal, the modulated facsimile image signal will have a facsimile image signal component of 2100Hz - 1638Hz = 462Hz, that is, a facsimile image signal component of 462Hz. Occur. this frequency
The 462Hz facsimile image signal component has the same frequency as the procedure interrupt signal issued from the receiver side in the case of a half-duplex system or Yonifax system. This may cause the facsimile on the transmitting side to ask if it is a frequency component in the facsimile image signal being sent from its own machine when it detects 462Hz, or to interrupt the procedure to stop the facsimile transmission operation from the receiver side. I can't tell if it's a signal or not.

Therefore, when a conventional facsimile machine detects a 462Hz signal, it forcibly changes the transmission signal to 2100Hz, the same as the carrier frequency, and temporarily transmits a signal indicating that it is completely white. It was assumed that there was a signal to interrupt the procedure.

By the way, if a signal indicating that the image is completely white is transmitted even temporarily, a part of the received facsimile image will contain all white, so there is a problem in that the image quality of the facsimile image as a whole will be significantly degraded. It was hot.

[Problem that the invention seeks to solve]

The facsimile image received as described above is
When determining the presence or absence of a procedure interruption signal, a portion of the image includes all white, resulting in a significant deterioration in image quality.

Therefore, the purpose of the present invention is to solve the above problems and
To provide a facsimile procedure interruption signal detection device that does not impair the image quality of a facsimile image even when determining a procedure interruption signal.

[Means for solving problems]

As shown in the diagram corresponding to the embodiment, the facsimile procedure interruption signal detection device of the present invention has a means for switching the sampling frequency of the transmitted image signal between the frequency reduced by the frequency divider 7 and the original sampling frequency. A sampling pulse reducing means 20 is provided which switches the sampling pulse at 6 and sends it to the sampling section 1. Further, the detection unit 4 detects a frequency component that can be regarded as the same as the procedure interruption signal from the receiving side from the modulated image signal obtained from the network control unit 3 to which the sampling unit is connected via the modulation unit 2, When the switching means is switched to the frequency dividing section 7 side, and the timer section 5 measures a certain period of time from the time when the detection signal is output to the detection section, and the detection signal is still present after the certain period of time. is equipped with procedure interrupt signal detection means 20 for outputting a signal indicating that it is a true procedure interrupt signal.

[Effect]

If the modulated image signal from the transmitting side contains a frequency component that is considered to be the same as the procedure interruption signal from the receiving side, that frequency component is detected by the detection section of the procedure interruption signal detection means, and the sampling pulse is detected by the detection section of the procedure interruption signal detection means. The switching means in the reduction means is switched to the frequency dividing section side. As a result, the reduced frequency after frequency division is sent to the sampling section instead of the original sampling frequency, and the upper limit of the image signal frequency that can be transmitted is suppressed. Therefore, from the frequency components in the modulated facsimile signal transmitted by the own machine, the frequency component that is considered to be the same as the above-mentioned procedure interruption signal that appears in the high frequency range of the image signal is removed.

The timer section in the procedure interruption signal detection means measures a certain period of time from the time when the detection signal is output to the detection section. After this certain period of time has elapsed, the modulated image signal returned for self-monitoring via the network control section excludes the frequency component that is considered to be the same as the procedure interruption signal. If the detection signal is still present after the predetermined period of time has elapsed, the timer section determines that it is a true procedure interruption signal from the receiving side, and outputs a signal to that effect. Therefore, the presence or absence of a procedure interruption signal can be determined without error, and since the above-mentioned frequency component detection and removal operation is also performed in the image signal section, the procedure can be immediately interrupted after the predetermined time set by the timer section has elapsed. .

On the other hand, the received image of the image signal that is sampled at the reduced sampling frequency, modulated, and transmitted is only degraded in image quality by the amount of the reduction.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

The figure shows an example of a facsimile procedure interruption signal detection device according to the present invention. The binary image signal sampled by the sampling pulse in the sampling section 1 is guided to the modulation section 2 and then sent out to the telephone line via the network control section 3.
The own image signal is supplied to the procedure interruption signal detection means 10 together with the signal from the receiver side sent from the telephone line. The detection output of this procedure interruption signal detection means 10 is led to the sampling pulse reduction means 20, which converts the sampling pulse corresponding to the detection output into the sampling section 1.
Add to CLK terminal.

Here, the procedure interruption signal detecting means 10 outputs a detection signal when it detects a 462Hz frequency component that can be regarded as the same as the procedure interruption signal that the other party's receiver issues when it wants to interrupt communication for some reason.
It consists of a 462Hz detection section 4 and a timer section 5 which counts a certain period of time from when the detection signal is output and outputs "1" when the detection signal is still present after counting.

Further, the sampling pulse reduction means 20 includes a frequency dividing section 7 that divides and reduces the original sampling frequency of 10368 Hz.
It is switched by the 462Hz detection part signal of the procedure interruption signal detection means 10, and when there is no detection signal, the original sampling frequency is output as a sampling pulse, and when there is a detection signal, the divided frequency is sampled. Changeover switch (switching means) 6 that outputs as a pulse
It is composed of. The frequency dividing unit 7 is configured to output 5184Hz as a 1/2 frequency, but the high frequency part of the binary image signal sampled by the sampling unit 1, especially 1638Hz, which causes misjudgment. This frequency division is not limited to 1/2 frequency division because the above frequency division is performed in order to remove the frequency component of from the sampled output. For example, 1/3 frequency division or 2/3 frequency division may be used.In short, the frequency component around 1638Hz is removed from the transmission baseband signal of the facsimile image signal, and the received image does not become completely white. It is only necessary to reduce the frequency to an extent that does not cause deterioration in image quality.

Now, in the above configuration, when a frequency component that can be regarded as the same as a 462Hz procedure interruption signal is added to the procedure interruption signal detection means 10, the 462Hz detection section 4 outputs a detection signal, which is applied to the sampling pulse reduction means 20. . The sampling pulse reduction means 20 to which the detection signal has been applied has its changeover switch 6 switched to the frequency dividing unit 7 side, and instead of the 10368 Hz sampling pulse that had been outputted so far, it has been reduced to a frequency divided by 1/2. 5184Hz
Outputs sampling pulses. Therefore, 2 sampled by the sampling unit 1 by this sampling pulse
The high frequency part of the value image signal is removed, and 1638
If a high frequency component of Hz is included, that component is excluded. Therefore, the frequency of 462 Hz, which can be considered to be the same as the procedure interruption signal, is also removed from the facsimile image signal modulated by the modulator 2. This modulated image signal is returned via the network control unit 3 for self-monitoring.

During the self-image signal returned for self-monitoring,
Since the 462Hz frequency component is removed, the 462Hz detection unit 4 detects only the 462Hz procedure interruption signal issued from the receiver. Therefore, when the 462Hz detection section 4 continues to output a detection signal even after the changeover switch 6 is switched, it means that a true procedure interruption signal has been sent. Conversely, if the 462Hz detector 4 no longer outputs a detection signal, it means that the own device was outputting that frequency component. Such a determination is made by the timer section 5. That is, after the 462Hz detection unit 4 outputs the first detection signal, the 462Hz
If the detection signal still exists after a certain period of time sufficient to eliminate the Hz frequency component, the timer section 5 outputs "1". As a result, a component in a self-transmitted image signal is no longer erroneously determined to be a procedure interruption signal from the receiver side.

On the other hand, the facsimile image signal, which has been sampled at 5184 Hz, which is half the original sampling frequency, and which has been modulated, is similarly sent to the telephone line via the network control section 3. As a result, the density of the received image is temporarily reduced to 1/2, but unlike the case where the transmitted signal is forced to 2100Hz, which is the same as the carrier frequency, and an all-white signal is transmitted, this causes a significant deterioration in image quality. can be avoided.

〔Effect of the invention〕

As described above, according to the present invention, if the modulated image signal on the transmitting side contains a frequency component that is considered to be the same as the procedure interruption signal from the receiving side,
This is detected and removed, and after a certain period of time has elapsed, it is determined whether or not there is a procedure interruption signal from the receiving side, which is the other party, so that identification can be made without error. Moreover, since the above-mentioned detection and removal action is performed also in the image signal section, the procedure can be immediately interrupted after the predetermined time set by the timer section has elapsed.

In addition, when a frequency component that is considered to be the same as the procedure interrupt signal is detected, instead of changing the transmitted signal to the carrier frequency, the sampling frequency is reduced from its original value by the frequency divider, so that the received signal is not detected. The resulting image will not be completely white, and the image density will drop by the amount of reduction, but overall the deterioration in image quality can be suppressed as much as possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a facsimile procedure interruption signal detection device according to the present invention. In the figure, 10 is a procedure interruption signal detection means, and 20 is a sampling pulse reduction means.

Claims (1)

[Claims] 1. Sampling pulse reduction means for switching the sampling frequency of the transmitted image signal by the frequency dividing section and the original sampling frequency and sending the same to the sampling section; A detection unit detects a frequency component that can be considered to be the same as a procedure interruption signal from the receiving side from among the modulated image signal obtained from the network control unit connected through the network control unit, and switches the switching means to the frequency division unit side, A timer section measures a certain period of time from when the detection signal is output to the detection section,
A procedure interrupt signal detection device for a facsimile machine, comprising procedure interrupt signal detection means for outputting a signal indicating that the detection signal is a true procedure interrupt signal when the detection signal remains even after a certain period of time.