JPS59122176A - Facsimile picture signal synchronizing system - Google Patents

Abstract

PURPOSE:To prevent a delay from being caused between a phase signal and a picture signal by utilizing a frame clock for taking synchronism of the picture to minimize the deterioration of the transmission efficiency without requiring any highly accurate crystal oscillator even in an independent synchronism system. CONSTITUTION:U and D are incoming and outgoing transmission lines respectively, a transmission/receiving circuit 10 includes a frame synchronism circuit and a strobe clock signal PC is generated separately from a facsimile signal period. In taking the synchronism of a picture signal, a control circuit 11 controls the step with an opposite transmission side. Then, the main control circuit 11 outputs a signal K to synchronize a counter 12. The counter 12 takes a frame pulse (f) to a clock input for counter and its output is ANDed at an AND circuit 14 together with a phase signal (g) and a strobe signal PC and the result is led to a detecting circuit 15, which checks an output pulse width to discriminate whether or not the synchronism is taken.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for ensuring signal synchronization after frame synchronization of facsimile image signals.

In switching equipment that exchanges digital audio signals (PCM (M number)), in addition to the audio signal, a synchronization signal and a control signal are added to form one transmission unit (frame) and the audio signal is transmitted. When attempting to perform facsimile communication by exchanging facsimile signals using a switching device,
In order to reduce the cost of facsimile machines, a method has been considered in which the number of bits in the portion corresponding to the voice signal is increased to achieve high-speed transmission without using complicated means such as redundancy compression/expansion.

In this case, the original signal of the facsimile signal is the facsimile signal before redundancy compression or after expansion, and synchronization of facsimile images becomes a problem. That is, since it is an original signal, the phase signal indicating the end of the - line cannot be inserted into the facsimile signal as a unique pattern.

In such a case, an image phase synchronization method using independent synchronization is generally used, for example, 02 facunmilli according to the CCITT recommendation. There are three drawbacks to the independent synchronization method: The first is that a highly accurate crystal oscillator is required to maintain synchronization after establishing image phase synchronization.

The second point is that a large width is required to reliably identify a phase signal from transmission noise. That is, since the phase signal is no longer necessary after synchronization is established, the wider the phase signal width, the lower the transmission efficiency will be. Thirdly, as shown in Figure 5, the original phase signal (a) is passed through an integrating circuit such as a low-frequency wave transducer in order to distinguish the phase signal from noise etc. The difference is that the phase signal is delayed by Td and differs from the original phase signal in the position occupied in the image signal. That is, when recording the received image (11) on recording paper, the effective recording width is narrowed because it deviates by Td, and the amount of TdO is also not constant due to environmental changes, so it has the disadvantage that a precise effective recording width cannot be set. .

On the other hand, a method may also be considered in which the phase signal is transmitted independently of the image signal using the synchronization signal or control signal of the frame.1. In this case, the signal transmission format is unique to facsimile signals, and cannot be adopted if audio signal transmission is also considered.

The purpose of the present invention is to minimize the deterioration of transmission efficiency without requiring a high-precision crystal oscillator even with an independent synchronization method.
An object of the present invention is to provide a facsimile image signal synchronization method that does not cause a delay between a phase signal and an image signal.

Examples of the present invention will be described in detail below.

FIG. 1 is a block diagram for explaining the present invention in detail. In Figure 1, DX is an exchange device that has the function of exchanging digital signals, FAX is a facsimile terminal device that captures and records facsimile images, and DX is a telephone and C
0FX is the facsimile office line interface section CO, I that performs redundancy compression/expansion/modulation/demodulation of 7-ac 7mm signals.
The facsimile signal processing device sIP, which is composed of the F and the network control unit NCU, is an additional information printing device used to additionally record service information outside the margin of the facsimile screen. Telephone equipment, facsimile terminal FAX, FAX 7
The central office line interface unit C0FX and the additional information printing device SIP are connected to the switching device DX by an extension transmission line (approximately 1- at the longest). Switched connections in the system are performed in pairs, one for voice calls and one for facsimile communications. That is, in the embodiment of the present invention, since the FAX 7mm terminal device is not equipped with dialing and calling functions, the connection is made by a telephone, and the F81 communication is realized following the voice call connection. However, since the voice signal and the facsimile signal are connected through separate routes, it is possible to carry out voice calls and facsimile communications simultaneously. The facsimile signal processing device C0FX is connected to the extension line and at the same time to the public telephone line Co (central office line).When using the central office line CO, it goes without saying that voice calls and facsimile communications are Since this cannot be done at the same time, the voice communication path must be established before switching to facsimile communication.

Telephone ALG and facsimile I that make up this system
J terminal device F'AX, facsimile signal processing device ゛6C
The OFX and the additional information printing device SIP can be expanded according to the frequency of use, and the optimum/stem configuration can be configured according to the user's requirements.

FIG. 2 is a diagram for explaining the format of signals when performing extension line transmission. (a) shows exchange equipment DX, telephone equipment, and facsimile terminal equipment FAX.

This indicates the transmission format of voice information or facsimile information transmitted between the facsimile signal processing device C0FX and the additional information printing device 5IP (hereinafter referred to as the terminal), and P is the part on which the encoded voice signal or facsimile signal is loaded. , S is a part for transmitting dial information, monitoring information, etc. between the switching device DX and the terminal, DI to D5 (D bit) is a part for transmitting mutual control information from terminal to terminal, Fo to F5 (Fbit, To) are unique patterns (OIO) to synchronize the system.
This is the part that transmits the information. S and D Bi,
Each position of the target can be automatically identified by detecting this unique pattern. A unit consisting of F, P, and S or D is called a frame, and the transmission time of an l frame is 125 microseconds, but the S bit is transmitted once every 6 frames as shown in (b), and the D bit is transmitted once every 6 frames. , and are transmitted five times in six frames as shown in (C). The switching device DX and each terminal are actually connected by four wires, two of which transmit downlink information from the switching device DX to each terminal, and the other two wires from each terminal to the switching device DX. Convey information upstream. That is,
The transmission method is full duplex communication format. (d) shows one frame of audio information, where the audio signal is composed of 8 bits. (e) shows one frame of facsimile information, where the facsimile signal consists of 32 bits, four times as many as the voice signal. Transmission in this digital format is not performed in all parts of this system; in Figure 1, the voice signal connected from switching equipment DX to central office line CO is a decoded analog signal; In the case of a telephone with a general configuration, an analog voice signal is transmitted between the telephone stack and the telephone exchange device DX, which is encoded in the exchange device DX and passes through the 1u1 channel switch and H. .

In the system described above, the present invention is particularly concerned with the facsimile terminal FAX and the no-acne ξ
terminal device FAX, or facsimile terminal device F
AX and facsimile signal processing device C0FX or facsimile terminal device FAX and additional information printing device 'S I
This is a method of image signal synchronization when facsimile communication is performed between P. The image signal synchronization method will be described in detail below using FIGS. 3 and 4. FIG. 3 is a diagram for explaining the waveforms of each part in FIG. 4, and FIG. 4 is a block diagram showing the parts related to the embodiment of the present invention in the facsimile terminal FAX. U and D in FIG. 4 are an upstream transmission path and a downstream transmission path, and the transmitter/receiver circuit 10 includes a known 7-rem synchronization circuit. The frame clock shown in (f) (Fig. 2 (a)
(a clock generated at the F bit position) or a strobe clock (pC) indicating the facsimile signal period, that is, the period P in FIG. 2(a). When performing image signal synchronization, first the main control circuit 1
1 to perform procedure control with the other party's transmitting side and to ensure that it is time to perform image signal synchronization work. This is done using D bits as explained in the previous example. After this confirmation, the main control circuit 11 issues a signal to the counter circuit 12 to start synchronization work, and during the synchronization work, a phase signal as shown in Figure 3 (b) is sent from the transmitting side. . This phase signal is made less susceptible to noise by dropping the high frequency part in the integrating circuit 13 as shown in Figure 3 (b).
A reset pulse for the counter circuit 12 as shown in (i) is output. Initially, the counter circuit 12 outputs a phase signal in a state different from the phase signal of (b)) as shown in A of FIG. 3(j), but at time B, it is reset by the reset pulse (1), Frame pulse (f) for counting
:+7 is input, so counting is restarted from point C, and phase number 48 like D is output. The output of the counter circuit 12 is ANDed by the AND circuit 14 together with the received phase signal (Fig. 3 (ω)) and strobe signal (pc).
is taken and guided to the verification circuit 15. The detection circuit 15 checks the pulse width in the same manner as the integration circuit 13, and
If the pulse width is equal to or greater than the specified value, it is reported that the main control circuit ILK phase is synchronized. At that point, the main control circuit 11 outputs a signal (■ in FIG. 3) to the counter circuit 12 to stop the synchronization operation, and at the same time requests the sending side to send a standard signal using the D bit.

In the system according to the present invention, facsimile terminal device FA
Since the target of transmission is an XtdA4 version original, the number of pixels in the main scanning line is 1728 bits. On the other hand, in order to stably transmit the facsimile signal, 3 bits in one frame of the facsimile signal are used as control signals, so the number of pixels that can be transmitted in one frame is 29 bits. Therefore, to transmit one line, 59 frames and 1
Although 7 frames are required, in the embodiment of the present invention, 60 frames constitute one line in synchronization with the frame clock.

In this way, synchronization with the frame clock provides three advantages. First, since the frame clock is of course also supplied to the transmitting side and the phase signal is created, a high-precision crystal oscillator is not required. The second is 12 bits, which is 29 bits minus 17 bits, as seen from the operation of the previously explained embodiment.It does not have to be 12 bits, and the entire frame can be applied to the phase signal during synchronization work, so Discrimination from noise is advantageous in that only 12 bits are responsible for reducing transmission efficiency during image transmission. Third, since it is not directly synchronized with the received phase signal but synchronized with the frame clock, there is no deviation from the image signal as explained in Figure 5, and the recording effective width can be set precisely. That is the point.

The above description has been made with reference to A4 size originals, but even for originals of different sizes, the number of unnecessary bits related to transmission efficiency may differ, but the basic advantages remain the same.

As explained above, according to the present invention, since images are synchronized using frame chromatography, a high-precision crystal oscillator is not required despite the independent synchronization method.
This has the advantage that there is little deterioration in transmission efficiency and that the effective recording width of the image can be precisely set.

[Brief explanation of the drawing]

Figure 1 is a basic diagram for explaining the outline of the system to which the present invention relates, Figure 2 is a time chart for explaining the format of the transmission signal used in the present invention, and Figure 3 is an embodiment of the present invention. FIG. 4 is a time chart for explaining the details of the present invention, and FIG. 5 is a time chart for explaining the drawbacks of the conventional synchronization system. Patent applicant: Iwasaki Tsushinki Co., Ltd. Agent: Inuzuka: 1 person from outside the university

Claims (1)

[Claims] To send and receive facsimile signals in frames,
A facsimile image signal synchronization method characterized in that the main scanning period is determined to be an integral multiple of the frame period, and after frame synchronization is established on the receiving side, phase synchronization is ensured by a counter that takes the frame clock as an argument.