JPS6031377B2 - Line skip pulse transmission detection method in facsimile equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a line skip pulse transmission detection method in a facsimile machine.

Facsimile machines that use the so-called analog transmission method, which directly transmits the image signal obtained from the original without compression encoding, are equipped with a so-called line skip function that skips the margins of the original and transmits it, in order to shorten the transmission time. In many cases.

A facsimile transmitter equipped with such a function generally reads the content of the line image signal obtained by pre-scanning the original, and if the image signal after a certain line is from the margin of the original, that line is read. A skip flag signal indicating that the subsequent lines will be skipped is placed in the phase signal period of the first line, and a line skip pulse and the image signal period following that phase signal period are used to cause each subsequent line to be skipped on the receiving side. Then, each signal is transmitted to the receiving side.

At this time, in order to efficiently shorten the transmission time when a large number of lines to be skipped continue, it is desirable to be able to transmit as many line skip pulses as possible during the above-mentioned image signal period. From this point of view, conventionally, a line skip pulse is sent out immediately after the skip flag signal is sent out, and the skip pulse is detected on the receiving side using the receiving side phase signal as a time reference.

However, although the phase signal on the receiving side is phase-matched with the phase signal on the transmitting side, a slight phase matching error is allowed between the two, and this error may cause a malfunction in skip pulse detection. may occur. That is, as shown in FIG. 1, the skip flag signal F sent from the transmitting side and the line skip pulses S, , S2 (
If the receiving side phase signal Pr advances in phase with respect to Fig. 1 A), the flag signal F may be mistakenly detected as a skip pulse, and if the phase signal Pr lags in phase, There is a risk that the first line skip pulse S, will not be detected. Furthermore, although facsimile signals are transmitted via telephone lines using appropriate carrier waves, the attenuation and delay characteristics of telephone lines are not flat over the entire facsimile zone. There is also a problem that unnecessary signals are generated when demodulating, and these are erroneously detected as skip pulses.

That is, in Figure 2, if A is a skip pulse created on the transmitting side, this is modulated and transmitted, and then demodulated on the receiving side to become the signal at the beginning, which becomes the signal at C after waveform shaping. Therefore, the pulses in the front twill and rear green parts of this signal are also detected as skip pulses. In this case, the demodulated signal on the receiving side is, for example, AM (especially AM-PM) of the VSB (residual single sideband) system used in facsimile communication.
If demodulation is used, high frequency components corresponding to the rising edge of the pulse will appear on the lower side of the transmission band, and in telephone lines, the attenuation characteristics become better as the frequency goes lower. This is because high-frequency components of the facsimile signal, such as the rising edge of the pulse, are emphasized. Therefore, the present invention takes these points into consideration and proposes a line skip pulse transmission detection method that allows line skip pulses to be detected without malfunction on the receiving side.The details thereof will be explained below. First, on the transmitting side, as in the case of the conventional example described above, a skip flag signal is sent out during the transmitting side phase signal period, and a line skip pulse is sent out during the box signal period following the phase signal period. However, in the present invention, as shown in FIG. A major feature is that the blanking period length is selected to be at least twice the maximum phase matching error that can be tolerated on the receiving side. On the other hand, on the receiving side, the received signal as described above [Figure 1 2]
After the trailing edge of the receiving side phase signal Pr (see Figure 1 or C), a waiting period A is provided which is approximately equal to or longer than the maximum phase matching error of the planking period B, and this period The detection operation of line skip pulses S, S2, etc. is started after the passage of A, and this output operation is performed by sampling at a timing approximately in the center of each of the skip pulses, and the detection operation is performed when the last pulse of the sampling output is Another major feature of the present invention is that it is stopped after a certain period of time has elapsed from the time it was derived. Now, to explain the reason why the planking period B and the waiting period A are selected as described above, as can be seen from FIG. In order to prevent the skip flag signal F from being accidentally detected as a line skip pulse in the case of matching, the waiting period A must be longer than the time equivalent to the maximum phase matching error △7 between the receiving side phase signal Pr and the transmitting side phase signal Pt. Must be selected.

This is because the skip flag signal F is transmitted over the entire transmission side phase signal period Pt. On the other hand, assuming case C when the receiving side phase signal Pr is delayed with the waiting period A set as shown here, in order to be able to always detect the first line skip pulse S, in this case,
The planking period B is B>△70A=2△? In other words, it is sufficient to select at least twice the maximum phase matching error. In addition, in order to detect line skip pulses at approximately the center timing of each pulse, it is necessary to avoid erroneously detecting unnecessary pulses in the front twill area and rear green area in Figure 2 (c), and to avoid sampling. The reason why the detection operation is stopped after a certain period of time has elapsed since the last output pulse is derived is to prevent transmission noise from being detected as a skip pulse.

Next, a method of transmitting and detecting the skip flag signal F and line skip pulses S, S2, etc. as described above will be explained in detail. The skip clock signal F is created by reading scan, and then the line skip pulse generated one by one for each line scan is sent out through an appropriate delay circuit. The operation of only the side will be described in detail with reference to the time chart of FIG.

In Fig. 3, 1 is an input terminal on the receiving side, and the transmitting side phase signal received before the image signal is supplied to the phase signal generation circuit 2 through this terminal, and is generated here. Phase matching is performed with the receiving side phase signal.

When this phase matching is completed, facsimile signal transmission is started, and the image signal, line skip pulse, etc. are transmitted from the transmitting side together with the transmitting side phase signal. Therefore, if the signal D in FIG. 4 is now transmitted to the terminal 1 (where D represents the waveform after demodulation), this signal is the receiving side phase signal from the phase signal generation circuit 2. P
The skip flag signal F inserted into the phase signal period is extracted by being gated by the gate circuit 3 using r, and is detected by the flag signal detection circuit 4.

In this case, the flag signal F changes the carrier wave of the phase signal period in which this number is inserted to a frequency (for example, 1
650HZ), so it is easy to detect. In addition, FIG. 4 shows a case where the receiving side phase signal Pr has a phase error .DELTA. with respect to the transmitting side phase signal Pt'. When the flag signal F is detected by the detection circuit 4, the first timer circuit 6 outputs an output T after a period of time 7 equal to the above-mentioned waiting period A has elapsed from the trailing edge of the phase signal Pr, and the change point is detected by the output. The circuit 7 and a third timer circuit 14, which will be described later, are triggered.

When triggered, the change point detection circuit 7 sequentially detects the rising points of the output D of the demodulation circuit 5 which receives the received signal as input.
Therefore, the line skip pulse S in the demodulated output D,
, Sn appears at the timing of each leading edge of the detection circuit 7, and the second timer circuit 8 appears at each pulse.
is triggered repeatedly. When this second timer circuit 8 is triggered, from that point on, the skip pulses S, ~S
After 72 hours, which is approximately the reverse of the pulse width of n, the pulse T
2 and supplies this pulse to the sampling circuit 9. The output pulse K of the detection circuit 7 is also a third timer.
Reset the circuit 14.

This third timer circuit 14 is designed to output an output after 73 hours have elapsed from the time it is triggered, and the third timer circuit 14 is a time 7 corresponding to the blanking period of the received signal D. and skip pulses S, , S2, etc. are selected to be larger than the inter-pulse intervals. Therefore, the third timer circuit 14 does not output any output pulses while the pulses K are continuously being output. The sampling circuit 9 is configured to sample the output D of the demodulation circuit 5 using the output pulse L of the second timer circuit 8, and therefore its output is the skip pulse S, .
It becomes like S for Sn.

This sampling output pulse S is inputted to one of the first and second counting/memory circuits 11 and 12 via a switching circuit 10 which is switched for each receiving side phase signal Pr. The first and second counting/memory circuits 11 and 12 count and store the number of sampling output pulses derived within one picture signal period, and when one count is stored, the other is stored in the previous picture signal period. The number of clock pulses equal to the number of pulses obtained is derived, and these pulses are supplied to a drive circuit (not shown) for a sub-scanning pulse motor.

At this time, the reason why the sampling output pulse is temporarily stored as described above will be explained later.

Then, when the output pulse corresponding to the last skip pulse Sn is output from the sampling circuit 9, a pulse L is output from the third timer circuit 14 after 3 hours have elapsed from that point, and this pulse causes the change point detection circuit 7 to Operation is stopped. This ends the line skip pulse detection operation within one picture signal period. that time,
When the last skip pulse Sn is the last one that can be transmitted within one picture signal period, for example, the 18th one,
The output date appears in the judgment circuit 13 that detects it, and this output causes the third timer circuit 14 and the change point detection circuit 7
will be stopped. Therefore, in this case, when the last skip pulse Sn is detected, the detection operation is immediately terminated without waiting for 73 hours to pass. Thereafter, the above operation is repeated for every millet where the skip flag signal F is detected. By the way, the reason why the sampling output pulse S is stored once as described above is because the box signal for each line that is sequentially demodulated by the demodulation circuit 5 is not sequentially recorded in real time. This is because the fractional signal is stored once and recorded when the next line is received, but since this point is not related to the gist of the present invention, further explanation will be omitted.

Furthermore, the reason why the skip pulse detection operation is terminated based on the output date of the determination circuit 13 is that there is no need to keep the device in operation after the output date appears; This is because if it is left in the active state, unnecessary external noise may cause it to malfunction. In addition, if the time lengths 7o, 7, etc. of the planking period B and waiting period A mentioned above are exemplified for a mid-range machine that complies with CCITT's Glo standard, the allowable phase error is 1.
Since the line equivalent time is said to be within 2% of a second, 7o is approximately the same as the phase signal period length, 8-seconds, and 4-m, which is approximately the same as the phase signal period length. .

Furthermore, if the number of line skip pulses that can be transmitted within one picture signal period is 18, the pulse width and pulse interval are 4.17 m seconds and 8.3 h seconds, respectively.
The delay times ↑2 and ↑3 of the timer circuits 8 and 14 may be approximately ah seconds and 10 to 12 h seconds, respectively. Since the line skip pulse transmission detection method of the present invention is as described above, the skip flag signal will not be mistakenly detected as a line skip pulse on the receiving side, and the line skip pulse will not be reliably detected. Furthermore, even if the received line skip pulse is subject to transmission distortion or the like, it can be detected accurately.

In addition, especially when the skip pulse detection operation is stopped after a certain period of time from the time when the last pulse of the line skip pulse detection sampling pulse is derived, it is possible to eliminate the malfunction of detecting transmission noise as a skip pulse. It can be completely removed and can be used in facsimile machines to great advantage.

[Brief explanation of the drawing]

Fig. 1 is a simple time chart for explaining the transmission detection method of the conventional method and the present invention, Fig. 2 is a diagram showing the waveform after receiving and demodulating the line skip pulse, and Fig. 3 is a diagram showing the transmission detection method of the present invention. FIG. 4 is a diagram showing a schematic configuration of the receiving side of the adopted facsimile IJ device, and FIG. 4 is a time chart for explaining its operation. DESCRIPTION OF SYMBOLS 1...Input terminal, 2...Phase signal generation circuit, 3...Gate circuit, 4...Skip flag signal detection circuit, 5...Demodulation circuit, 6... ...・First timer circuit, 7... Change point detection circuit, 8...
second timer circuit, 9...sampling circuit,
10... Switching circuit, 11, 12... First and second counting and storage circuit, 13... Judgment circuit, 14...
...Third timer circuit. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. When a document is pre-scanned and read one line at a time and the transmission and recording of image signals after a certain line obtained thereby are skipped, it is possible to skip the transmission and recording of image signals after this line. In a facsimile device that sends out a skip flag signal indicated during a phase signal period, and sends out a line skip pulse for skipping each line after that line during an image signal period, the transmitting side sends out the skip flag signal. The line skip pulse is sent after a blanking period corresponding to at least twice the maximum phase matching error on the receiving side has elapsed from the point in time, and when the receiving side detects the skip flag signal, from the trailing edge of the receiving side phase signal. The skip pulse detection operation is started after a time corresponding to approximately 1/2 of the blanking period has elapsed, and the detection operation is performed by siping each of the skip pulses at approximately the center timing thereof. A line-skip pulse transmission detection method in a facsimile machine, which is characterized by: 2. The line-skip pulse transmission detection method according to claim 1, wherein the detection operation is stopped after a certain period of time has elapsed from the time when the sampling output pulses derived at certain intervals disappear.