JPS593061B2 - Phase synchronization return method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phase regeneration method in a facsimile employing an analog transmission method, and particularly to a method for recovering phase synchronization when phase regeneration is erroneous.

In recent analog transmission facsimiles, if basic phase synchronization is performed before transmitting image information, the receiving side uses its own fixed frequency oscillator such as a crystal oscillator.
The variable phase signal on the transmitting side can also be regenerated on the receiving side.

On the other hand, if one line is completely white, the line can pass even if the signal frame is shortened. Therefore, by considering the one-line all-white signal frame and the line signal frame containing image information separately, and making the one-line all-white signal frame shorter than the line signal frame containing image information, transmission is possible. Time can be compressed. However, if the above transmission method is adopted, once the receiving side makes a mistake in phase signal reproduction, it will not be possible to achieve phase synchronization with image information transmitted thereafter, and the transmitted original will not be able to be reproduced.

In order to cope with the above-mentioned drawbacks, the present invention aims to provide a phase synchronization recovery method for quickly recovering phase synchronization when phase signal reproduction is erroneously performed. The present invention will be explained below based on the drawings.

FIG. 1 is a block diagram showing an embodiment of the phase regeneration method including the phase synchronization recovery method of the present invention, and FIG. 2 is a waveform diagram thereof. 1 is a variable frequency divider, which is composed of a variable counter 2 and a T-type flip-flop (hereinafter referred to as T-FF) 3; 162 waves and 377
By inverting TFF3 for each wave, the frequency becomes 36Hz as shown in Figure 2 a.
get the signal.

Note that the timing of this signal is matched by the transmission phase signal at the time of interface inputted from the terminal 14. On the other hand, a baseband signal b (FIG. 2b) transmitted from a facsimile transmitter is inputted from terminal 5.
This baseband signal is transmitted in a 36 Hz signal frame when one line contains image information and when it does not contain 6 Hz image information (one line is completely white). In FIG. 2b, the hatched area is the image signal, and the hatched vertical line is the discrimination signal indicating that one line is completely white. Here, a discrimination signal is inserted to discriminate the signal frame with one line margin, but as another discrimination method, (
Various methods can be considered, such as 1) deleting a part of the blanking interval, and (2) replacing part of the information that existed in the blanking interval with another signal, and it does not matter which method is used for determination. .

This baseband signal b and the clock from terminal 4 are input to AND gate 6, and its output is input to phase width counter 7.
Enter.

The phase width counter 7 counts the input signal (output from the AND gate 6) only when the signal c is at a high level. signal c
is the same as either signal a or signal 1,
It is switched by signal g. Note that signal a, signal 1, and signal g will be described later. This phase width counter 7
Now, it is checked whether the received phase signal and the transmitted phase signal match. If it is determined that the phase width is correct, that is, it is clearly a transmission phase signal, the phase width detection signal d(
Output Figure 2 d). When the phase width detection signal d is input to the discrimination signal detection circuit 8, the discrimination signal detection circuit 8 starts detecting a discrimination signal representing one line white from the baseband signal b. When the discrimination signal is detected here, the discrimination signal detection circuit 8 outputs the discrimination signal detection signal f (FIG. 2 f), and clears the counter 9 used for forming the reception phase.

The counter 9 normally counts the 36 Hz signal a generated by the variable frequency divider 1 and clears it every 6 waves. The contents of the count are shown in FIG. 2h. Note that the counter content 01 matches the timing of the transmission phase signal input from the terminal 14 at the time of synchronization. The decoder 10 outputs only when the counter 9 is cleared, that is, when the count becomes O. When this output and the 36 Hz signal a are input to the AND gate 11, the output signal 1 (FIG. 2) becomes the received phase signal. As described above, the transmission phase signal becomes 6H.
Even when changing from z (when one line includes image information) to 36 Hz (when one line is completely white) or vice versa, the reception phase signal can be synchronized with the transmission phase signal.

Next, a case where the discrimination signal detection circuit 8 cannot detect the discrimination signal will be explained.

If the discrimination signal detection circuit 8 does not output the signal when it should output as shown in FIG. 2 f1, the counter 9 will not be cleared and will continue to count. Then, the received phase signal stands at the position shown in FIG. 2, 11. This received phase signal 11 passes through a switching circuit 12 and is sent to a phase width counter 7 as a signal c.
(C1 in Figure 2). However, at this time, the phase of the baseband signal b sent from the transmitting side is not input, so a phase width undetected signal e (signal e1 in Figure 2) is output, and the signal e1 causes a flip-flop (hereinafter referred to as F.
Switching to. In other words, phase width detection is performed at 36 Hz. F. Fl3 keeps the signal g at high level until the discrimination signal detection signal F2 is input, and then becomes low level, and the content of the output signal c of the switching circuit is switched from signal a to signal 1 again. At the same time, the discrimination signal detection signal F2 clears the counter 9, and is ANDed with the signal a to generate a reception phase signal.

Only at this time does the received phase signal return to normal. In FIG. 2j, the "correct" part indicates that the transmitting phase and the receiving phase are synchronized, and the "erroneous" part indicates that they are not synchronized. As explained above, in the facsimile transmission method (in which the signal frame for one completely white line is transmitted by making it shorter than the signal frame for a line containing image information), when the transmitting phase and the receiving phase deviate, the transmitting phase signal is The phase recovery method of the present invention is characterized in that the phase width counter and the all-white discrimination signal are used to detect and restore synchronization. It is highly reliable.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the phase regeneration method including the phase synchronization recovery method of the present invention, and FIG. 2 is a waveform diagram thereof. 7... Phase width counter, 8... Discrimination signal detection circuit, 13... Flip-flop, 12
...Switching circuit.

Claims (1)

[Claims] 1 In the facsimile analog transmission system, which shortens the signal frame for a completely white line by processing it so that it can be determined as a signal frame for a line containing black information, thereby reducing transmission time, a mismatch in phase synchronization occurs. is detected, monitors the transmission phase signal width and the discrimination signal created by the signal processing at the phase interval of the white line signal frame, and forms the reception phase signal again based on the transmission phase signal when both are detected. A phase synchronization return method characterized by: