JPS58117770A - Switching contol system for high and low speed modem - Google Patents

Abstract

PURPOSE:To simplify the switching control at a reception station side, by receiving one line's share of a picture signal at a high speed MODEM and switching the reception to a control signal if normal reception is not done. CONSTITUTION:The data of each line produced at a reading circuit 4 is compressed at a compression circuit 5 and transmitted to a transmission line 3 via a communication control circuit 6, an MODEM7 and a network controller 8. The transmitted signal is led to a communication circuit 12 via a network controller 10 and an MODEM11 in a reception station 2, a line data compressed from reception frame information is picked up at the circuit 12 and converted into a conventional line data at a decoding circuit 13 and given to a recording circuit 14. The picture signal is transmitted at the high speed MODEM and the control signal is at the low speed MODEM, and whether or not the reception of one line's share of the picture signal is normally done is decided, and only when the normal reception is not done, the transmission of the control signal is performed in the low speed mode.

Description

[Detailed description of the invention] Technical field of invention The present invention is a high-speed/low-speed modem switching control method.

In particular, in a facsimile transmission system where control signals are sent and received using a low-speed modem and image signals are transmitted using a dual-speed modem, is there a speed-limiting modem? This invention relates to a high-speed/low-speed modem switching control system that simplifies control on the receiving station side by switching to receiving a control signal when one line of an image signal is not received correctly.

(B) Technical Background and Problems In high-speed facsimile machines used in subscriber telephone lines, it is necessary to take into consideration the conditions of transmission lines and other conditions in order to achieve reliable transmission and reception of control signals and high-speed transmission of image signals. In this method, a method (CCITT T30 recommendation) is adopted in which a low-speed modem is used for the transmission controller 11 and a high-speed modem is used for the image signal.

FIG. 1(A) f'1T30 transmission control assistance control manual operation example is shown. In the figure, high-speed modems are used for transmission of image signals indicated by diagonal lines, and are marked C, Dis, DC8, CFR, and EOP.
.

Control signals such as MCF and DCN are transmitted and received using a low-speed modem. When transmitting and receiving control signals, in order to ensure reliable transmission and reception, if the transmission or reception is defective, the control signal is retransmitted up to three times, including the first time.

Because of this failure, when the receiving side sends out the control signal CFR shown in FIG.
As shown in the figure, there are cases in which an image signal is sent to the receiving side by a high-speed modem, and cases in which a control signal DC8 is sent by a low-speed modem as shown in FIG. 1(E). That is, with the receiving side sending out the control signal CFR,
Sender 7! /X If the control signal CFR2 is correctly received, an image signal is sent out using the pot speed modem as shown in the diagram in the first garden. However, if the transmitting side cannot receive the control signal C)'R, the transmitting side sends the control signal DC8 three times in a manner that lasts for one frame period using a low-speed modem as shown in Figure 1 (B1). It is transmitted three times in total at intervals of about seconds.For this reason, from the receiving side, there is a state in which the image signal is being transmitted electronically by a high-speed modem as shown in the diagram in the first park, and a state in which the image signal is transmitted electronically by the As shown in Figure (B), there is a state in which the control signal DC8 is sent by a low-speed modem.

Conventionally, in order to deal with such a situation, on the receiving side, it was necessary to check whether one line of the image signal can be correctly received from the reception by the low-speed modem, and whether the synchronization signal of the control signal can be extracted from the reception by the low-speed modem. A method has been adopted in which both are monitored in parallel. However, in the case of the conventional method, the program processing and hardware configuration were complicated in order to monitor both in parallel.

(C) Purpose and structure of the invention The purpose of the present invention is to solve the above points.
The purpose is to simplify switching control so that reception by a high-speed modem is performed, and if the reception is insufficient, switching to reception of control signals is performed.

Therefore, the high-speed/low-speed modem switching control system of the present invention is configured to transmit and receive control signals for facsimile transmission and reception using a low-speed modem, and to transmit image signals using a high-speed modem. Subsequently, there can be either a mode in which an image signal is transmitted by the high-speed modem, or a mode in which a control signal is transmitted by a low-speed modem instead of the image signal, and in the latter mode, the control signal is In a facsimile transmission system that is designed to be retransmitted, the receiving side decodes the received signal for one line, assuming that it is from the above-mentioned high-speed modem.
a decoding circuit that determines whether the line is correctly received; a first carrier detection section that detects the presence or absence of a carrier corresponding to the high-speed modem; and a second carrier detection section that detects the presence or absence of a carrier corresponding to the low-speed modem. The image signal is controlled to receive the image signal on the condition that one line is normally received by the decoding circuit, and the one line is received normally. The present invention is characterized in that control is performed such that the control signal is received on the condition that the first carrier detection section and the second carrier detection section both detect no carrier. This will be explained below with reference to the drawings.

(1) Embodiment of the invention Fig. 2 shows the configuration of an embodiment of the invention, Fig. 3 Fi 1
The figure represents one embodiment of a determination mode in the illustrated mode determination section.

In FIG. 1, 1 represents a transmitting station, 2 a receiving station, and 3 a transmission line. Further, 4 is a reading circuit that generates line data as a scan result, 5 is a compression circuit that compresses data, 6 is a communication control circuit that generates frame information, and 7 8 represents a modem, 8 represents a network control device, and 9 represents a control unit. Further, 10 is a network control device, 11 is a modem, 12Fi communication control circuit for decoding frame information, and 13 is a decoding circuit for returning compressed line data to normal 2-in data. 14 is a recording circuit, 15 is a control unit, 16t is a high-speed modem carrier detection unit, 17 is a low-speed modem carrier detection unit, and 18 is a mode determination unit that determines whether the mode is an image signal reception mode or a control signal reception mode. The determining element 19 is a counter that detects whether the number of bits corresponding to 6 (1-)in is a predetermined value.

As is well known in the art, the line data of each line generated by the reading circuit 4 is data compressed in the compression circuit 5. Then, the communication control circuit 6 generates frame information, and the result is sent to the transmission line 3 via the modem 7 and network control device 8.

On the other hand, at the receiving station 2, the transmitted signal is guided to the communication control circuit 12 via the network side #device 10 and the modem 11. The communication control unit f12 extracts compressed line data from the received frame information, and the decoding circuit 13 converts it back to normal line data and sends it to the recording circuit 1.
Supply to 4.

In the case of the present invention, as described above, the image signal is transmitted using a high-speed modem, and the control signal is transmitted using a low-speed modem. If any of the above is sent to you,
There is a carrier corresponding to each modem, and the carrier is detected by the carrier detection section 16 or 17. Further, regarding the signal received by the high-speed modem and decoded by the decoding circuit 13, the counter 19 determines whether or not a predetermined bit amount exists, regarding the signal as an image signal corresponding to one line.
detected by. In other words, if it is an image signal,
The counter 19 counts the number of bits corresponding to one line.

In the case of the present invention, based on the state of carrier detection by the carrier detection sections 16 and 17 described above and the state of one line reception by the counter 19, the mode determination section 18 determines whether to receive an image signal or to receive a control signal. Let's decide whether to do it or not.

FIG. 3 shows an embodiment of the determination mode for this purpose.

That is, (1) It is checked whether the carrier (CD) is detected (f/) in at least one of the carrier detection sections 16 and 17.

(2) If it is detected, it means that something is being sent, and it is assumed that it is received from a high-speed modem, and - signal 1
Try decoding the part corresponding to the line.

(3) As a result, if the number of bits for one line is counted by the counter 19 shown in FIG. 2, it is determined that the image signal from the high-speed modem is being transmitted, and image signal decoding and recording begin.

(4) If the counter 19 is not counting correctly, the carrier detection units 16 and 17 check whether a state in which no carrier is detected occurs. When this state occurs, it assumes that the control signal is being sent using a low-speed modem and receives the control signal. If one of the carriers is present, try decoding one line again.

Since it is necessary to supplement the above item (4), we will add some additional explanation.

As shown in Fig. 1 (53), when the control signal DC8 is sent, the control signal DO8 exists for about 1 second, and after a break of about 3 seconds, the control signal DO8 is sent again. There is. As shown in FIG. 3, after the carrier (CD) is turned on, it takes H.2 minutes to determine whether or not one line of the image signal has been correctly received. For this reason, by the time it is determined that one line has not been correctly received, the first transmission of the control signal DO8 has generally been completed. In this case, carriers that support low-speed modems are also dropping. Of course, under such conditions, there are no carriers that support high-speed modems. therefore.

It is determined that a control signal has been sent, and the control signal receiving mode is set to correctly receive the next control signal DC8. Incidentally, if the image signal is being sent by a high-speed modem, the number of carriers will not drop by four in one printing machine.

(E) As described in detail, in the present invention, on the receiving side,
First, I treat it as an image signal and try to receive it. This facilitates monitoring on the receiving side and simplifies the control mode.

[Brief explanation of drawings]

1(A) and 1(B) are explanatory diagrams for explaining the prerequisite problem of the present invention, FIG. 2 is an embodiment of the configuration of the present invention, and FIG. This shows an example embodiment. In the figure, 1 is a transmitting station, 2 is a receiving station, 4 is a reading circuit, 5 is a compression circuit, 6.12 is a communication control circuit, 7.11 is a modem,
13 is a decoding circuit; 16 and 17 are respective carrier detection units;
18/ri mode determination unit and 19#'i counter which detects the number of bits for 1247 image signals. Patent applicant Fujitsu Limited

Claims (1)

[Claims] A mode in which a control signal for facsimile transmission and reception is transmitted and received using a low-speed modem, and an image signal is transmitted electronically using a high-speed modem, and the image signal is transmitted electronically by the high-speed modem subsequent to the transmission and reception of the control signal. In a facsimile transmission system in which the control signal is retransmitted in the latter case, the receiving side , a decoding circuit decodes one line of the received signal by decoding it as being from the high-speed modem, and determines whether or not the corresponding one line is correctly received; and a first circuit that detects the presence or absence of a carrier corresponding to the high-speed modem. It is provided with at least a carrier detection section and a second carrier detection section that detects the presence or absence of a carrier corresponding to the low-speed modem, and the above-mentioned image data is processed on the condition that one line is normally received by the above-mentioned decoding circuit. Control is performed on the manner in which the signal is received, and a state occurs in which neither the first carrier detection unit nor the second carrier detection unit detects a carrier because the one line is not received normally. A high-speed/low-speed modem switching control method in which control is performed to receive the above-mentioned standard @ flight number on the condition that