Patent Publication Number: US-6335803-B1

Title: Facsimile communication system

Description:
This is a divisional of Ser. No. 09/082,609, which was filed on May 20, 1998 and is now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates to a facsimile communication apparatus for allowing a plurality of facsimile machines designed for general telephone networks to communicate with each other via a data communication network, such as a local area network (LAN), and to a program recording unit which stores a program used in the facsimile communication apparatus. This invention also relates to a facsimile communication apparatus for allowing a plurality of facsimile machines to communicate with each other in real time via an Internet Protocol network (referred to as an IP network) based on the IETF (Internet Engineering Task Force), and to a program recording unit storing a program for controlling the facsimile communication apparatus. 
     2. Description of the Related Art 
     FIG. 1 illustrates a conventional facsimile communication system using a data communication network, such as an LAN. The transmission side facsimile machine  1  is a G3 facsimile machine designed for general telephone networks, which is categorized according to the T.30 Recommendation standardized by the ITU-T (International Telecommunications Union, Telecommunication Standardization Department). The facsimile machine  1  is connected to the facsimile communication apparatus  10 A via a telephone network  2 . The facsimile communication apparatus (i.e., the gateway)  10 A converts the communication protocol between the telephone network  2  and the LAN  4 . The LAN  4  is further connected to another facsimile communication apparatus (i.e., gateway)  10 B, to which the receiving side facsimile machine  7  is connected via a telephone network  6 . The facsimile machines  1  and  7  have the same standard, and they can mutually transmit and receive image information via the telephone networks. The facsimile communication apparatus  10 B has the same structure as the facsimile communication apparatus  10 A, and the explanation on it will be omitted. 
     As shown in FIG. 2, the facsimile communication apparatus  10 A has a terminal accommodation circuit  3   a,  to which a plurality of facsimile machines  1   a  through  1 n are connected via the corresponding telephone lines  2   a,    2   b , . . . ,  2   n  of the telephone network  2 . The terminal accommodation circuit  3   a  is connected to a switch circuit  3   b  which selects the line which is currently requesting a facsimile transmission from among the telephone lines  2   a  through  2   n . A CODEC  3   c  is connected to the switch circuit  3   b  in order to terminate the selected line. The CODEC  3   c  is a encoder/decoder which converts analog signals received from the telephone line  2   a  into digital signals, and which decodes digital signals into analog signals in order to output data to the telephone line  2   a.    
     The terminal accommodation circuit  3   a , the switch circuit  3   b  and the CODEC  3   c  are connected to the CPU  3   e  via a common bus  3   d . The CPU  3   e  controls the overall operations of the facsimile communication apparatus  10 A. A memory  3   f  and a LAN control circuit  3   g  are also connected to the common bus  3   d . The memory  3   f  temporarily stores digitized information prior to transmitting the digitized information. The LAN control circuit  3   g  performs data transfer in a packet format to and from another facsimile communication apparatus  10 B via the LAN  4 . 
     The facsimile machine  1  of FIG. 1 is connected to the facsimile machine  7  via the telephone line  2 , the facsimile communication apparatus  10 A, the LAN  4 , the facsimile communication apparatus  10 B, and the telephone line  6 , in that order. If pixel information is transmitted from the facsimile machine  1   a  of FIG. 2 to the facsimile machine  7 , the pixel data read by the facsimile machine  1   a  from the original document is encoded according to a prescribed coding rule. The encoded pixel data is modulated by, for example, a 9600 bps MODEM installed in the facsimile machine  1   a  to produce an analog signal in the voice frequency band. The analog signal is transmitted to the facsimile communication apparatus  10 A through the telephone line  2   a . The CODEC  3   c  of the facsimile communication apparatus  10 A samples the analog signal supplied via the telephone line  2   a  based on a sampling signal of, for example, 8 KHz, and converts the sampled analog signal into an 8-bit digital signal for each sampling. 
     Thus, the analog signal is converted into a 64 Kbps digital signal by the CODEC  3   c , which is then read by the CPU  3   e  via the common bus  3   d . The CPU  3   e  edits the digital signal into a packet data of a predetermined size, and temporarily stores the packet data in the memory  3   f . The packet data stored in the memory  3   f  is read out by the LAN control circuit  3   g , and transmitted to the receiving side facsimile communication apparatus  10 B via the LAN  4 . In the facsimile communication apparatus  10 B, the packet data received from the LAN control circuit  3   g  is temporarily stored in a memory. Then, the stored data is read out by a CPU corresponding to the CPU  3   e , and supplied to a CODEC corresponding to the CODEC  3   c , which converts the data into an analog signal and outputs the analog signal to the facsimile machine  7  via the telephone network  6 . Thus, t-he analog signal transmitted from the facsimile machine  1   a  is converted into a digital signal by the CODEC  3   c  of the facsimile communication apparatus  10 A, and transferred as a packet data to the receiving side facsimile communication apparatus  10 B via the LAN  4 . 
     However, the conventional facsimile communication system has several problems. 
     Because the transfer path of the LAN  4  is divided into a plurality of channels in order to transfer the data in a packet format, the transfer delay time of the packet data is not constant. In addition, if the traffic of the LAN  4  is heavy, the packet data may be lost half way through the transmission path. For these reasons, the analog signals which are being decoded by the CODEC  3   c  of the receiving side facsimile communication apparatus  10 B may sometimes be interrupted and, as a result, wrong data is received by the receiving side facsimile machine  7 . 
     Furthermore, although the inherent data transfer rate between the facsimiles machines  1   a  and  7  is, for example, 9600 bps, the data is transferred at 64 Kbps in the LAN  4 , which is inefficient from the standpoint of data transfer capacity. 
     SUMMARY OF THE INVENTION 
     Therefore, the object of the invention is to overcome the problems in the prior art, and to provide a facsimile communication system that can perform facsimile communication in an efficient manner from the standpoint of data transfer capacity with little transfer errors. 
     In order to achieve the object, in the first aspect of the invention, a facsimile communication apparatus comprises: facsimile procedure controller that receives and transmits control information and pixel information from and to facsimile machines connected to the facsimile communication apparatus according to a predetermined procedure; a first information converter that converts the control information and the pixel information received from the facsimile machines into a control packet signal and a pixel packet signal of predetermined formats; data transmitter/receiver that transmits the control packet signal and the pixel packet signal produced by the first information converter via a data communication network, and that receives a control packet signal and a pixel packet signal transmitted via the data communication network; and a second information converter that converts the control packet signal and the pixel packet signal received by the data transmitter/receiver into control information and pixel information which are to be output to a receiving side facsimile machine. The facsimile communication apparatus may further comprise a memory which stores a predetermined amount of pixel packet signals received by the data transmitter/receiver and which outputs the stored signals to the second information converter when the predetermined amount of signals are accumulated. 
     In the second aspect of the invention, a facsimile communication apparatus comprises: means for calling the receiving side facsimile machine based on a request for connection to the receiving side facsimile machine as received from the data communication network; means for temporarily storing the image data transmitted from the transmission side facsimile machine via the data communication network in a memory; means for starting transmission of the image data to the receiving side facsimile machine when a data-receiving control signal representing the acceptability of image data is received from the receiving side facsimile machine, provided that a desirable amount of image data is stored in the memory at the time of receipt of the data-receiving control signal; and waiting controller for transmitting a prescribed wait control signal to the receiving side facsimile machine in order to have the receiving side facsimile machine stand by if the desirable amount of image data has not been stored in the memory at the time of receipt of the receiving control signal representing the acceptability of the image data from the receiving side facsimile machine. 
     In still another aspect of the invention, a program recording unit for storing a program for controlling a facsimile communication apparatus is provided. This program recording unit comprises: means for causing the facsimile communication apparatus to call the receiving side facsimile machine based on a request for connection to the receiving side facsimile machine received from the data communication network; means for causing the facsimile communication apparatus to temporarily store the image data transmitted from the transmission side facsimile machine via the data communication network in the memory; means for causing the facsimile communication apparatus to start transmitting the image data to the receiving side facsimile machine when the facsimile communication apparatus receives a data-receiving control signal that represents the acceptability of image data of the receiving side facsimile machine, provided that a desirable amount of image data is stored in the memory at the time of receipt of the data-receiving control signal; and waiting controller for causing the facsimile communication apparatus to transmit a prescribed wait control signal to the receiving side facsimile machine in order to have the receiving side facsimile machine stand by if the desirable amount of image data has not been stored in the memory at the time of receipt of the receiving control signal representing the acceptability of the image data from the receiving side facsimile machine. 
     The waiting controller comprise determination means for determining whether or not the receiving side facsimile machine can stand by, while maintaining a data reception mode, if the desirable amount of image data has not been accumulated in the memory at the time of receipt of the data-receiving control signal. If it is determined that the receiving side facsimile machine can wait in the data reception mode, then waiting means causes the facsimile communication apparatus to wait for further storage of image data until the desirable amount of image data is stored in the memory. On the other hand, if it is determined that the receiving side facsimile machine is not able to wait in the data reception mode, wait control signal transmitter causes the facsimile communication apparatus to transmit the wait control signal to the receiving side facsimile machine. 
     The desirable amount of image data stored in the memory can be calculated by multiplying the transmission rate of the image data determined by negotiation between the transmission side facsimile machine and the receiving side facsimile machine by a predetermined time stored in advance. Alternatively, the desirable amount of image data can also be calculated by multiplying the communication rate determined by negotiation between the transmission side facsimile machine and the receiving side facsimile machine by a predetermined time stored in advance. The transmission side facsimile machine and the receiving side facsimile machine are G3 facsimile machines categorized based on the T.30 Recommendation. In this case, the data-receiving control signal is a data-receivable state confirmation signal CFR according to the T.30 Recommendation, and the wait control signal is a transmission site identification signal TSI according to the T.30 Recommendation. 
     The contents of patent application H9-131812 filed in Japan on May 22, 1997 and a patent application filed in Japan on Apr. 22, 1998, the application number is not yet assigned, are incorporated hereinto by reference. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and objects will be apparent from the following detailed description with reference to the attached drawings, wherein: 
     FIG. 1 illustrates a conventional facsimile communication system; 
     FIG. 2 is a hardware block diagram of a conventional facsimile communication apparatus; 
     FIG. 3 is a hardware block diagram of the facsimile communication apparatus according to a first embodiment of the invention; 
     FIG. 4 shows an example of control sequence of the facsimile communication apparatus of the first embodiment; 
     FIG. 5 shows an example of control sequence of the facsimile communication apparatus, which follows the control sequence shown in FIG. 4; 
     FIG. 6 is a hardware block diagram of the facsimile communication apparatus according to a second embodiment; 
     FIG. 7 shows the facsimile communication sequence according to a third embodiment of the invention; 
     FIG. 8 is a flowchart showing the operation of the facsimile communication apparatus  10 B according to a fourth embodiment; and 
     FIG. 9 is a hardware structural diagram of the facsimile communication apparatus according to the fourth embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     1. First Embodiment 
     FIG. 3 illustrates the facsimile communication apparatus  10 A according to the first embodiment of the invention. The facsimile communication apparatus  10 B has the same structure. The basic structure of the entire communication system that involves the facsimile communication apparatus  10 A and a plurality of facsimile machines is the same as that shown in FIG. 1, and the explanation will be omitted. A plurality of G3 facsimile machines  1   a  through  1   n , which are standardized according to ITU-T Recommendation T.30, are connected to the facsimile communication apparatus  10 A via the corresponding switchboard telephone lines  2   a  through  2   n.  The facsimile machine  1   a  reads pixel data from the original, and encodes it according to a prescribed coding rule in order to create pixel information PINF, which is then transmitted to a receiving side facsimile machine  7  via the telephone network  2 . The facsimile machine  1   a  also receives the pixel information PINF sent from another facsimile machine, and decodes it to reproduce the original pixel data and to output the transmitted image. In addition to the transfer of pixel data, the facsimile machine  1   a  transmits and receives several types of control information CINF to and from other facsimile machines. 
     A part of the control information CINF is transferred as a tone signal of, for example, 1850 Hz, while the rest of the control information CINF and the pixel information PINF are transferred as, for example, 9600 bps digital signals. The 9600 pbs digital signal is modulated to produce a voice-band analog signal (of, for example, 1800 Hz carrier frequency) by the MODEM built into the facsimile machine  1   a.  This analog signal is transferred to and from the facsimile communication apparatus  10 A via the telephone line  2   a.    
     The facsimile communication apparatus  10 A has a terminal accommodation circuit  11  for connecting a plurality of facsimile machines  1   a  through in via the telephone switchboard lines  2   a  through  2   n . The terminal accommodation circuit  11  is connected to a switch circuit  12 , which selects the line that is requesting facsimile transmission from among the telephone lines  2   a  through  2   n . The switch circuit  12  is connected to facsimile procedure controller(i.e., a procedure control circuit  13  and a facsimile procedure controller  14 ), which terminates the selected line. 
     The procedure control circuit  13  has a modem  13   a  which has the same standard as the built-in modem of facsimile machine  1   a . The modem  13   a  demodulates the analog signal received from the telephone line  2   a  to reproduce the original digital signal. The modem  13   a  also modulates the digital signal addressed to the facsimile machine  1   a  to produce an analog signal, and outputs the analog signal to the telephone line  2   a . The procedure control circuit  13  is connected to the facsimile procedure controller  14  which executes the transfer control procedure according to the Recommendation T.30, as in facsimile machine  1   a.    
     In other words, the facsimile procedure controller  14  decodes the control information CINF, which was sent from the facsimile machine  1   a  and received by the procedure control circuit  13 . Then, the facsimile procedure controller  14  produces response control information CINF, and sends it back to the facsimile machine la via the procedure control circuit  13 . The control information CINF and the pixel information PINF that are to be transmitted to the addressed facsimile machine  7  are output from the facsimile procedure controller  14  to the first information converter (i.e., the connection/transfer controller)  15 . 
     The connection/transfer controller  15  edits the control information CINF and the pixel information PINF supplied from the facsimile procedure controller  14  into packets of predetermined formats, and produces a control packet signal CPKT and a pixel packet signal PCKT which are to be transmitted via the LAN  4 . The connection/transfer controller  15  is connected to a memory  16  for temporarily storing the generated control packet signal CPKT and pixel packet signal PCKT. When receiving a facsimile from another facsimile machine, the connection/transfer controller  15  functions as a second information converter. That is, during the receiving operation, the control packet signal CPKT and the pixel packet signal PPKT sent via the LAN  4  are also temporarily stored in the memory  16 . When the amount of received pixel packet signal PPKT reaches a predetermined amount, the connection/transfer controller  15  reads out said predetermined amount of pixel packet signal PPKT, converts the pixel packet signal PPKT and the received control packet signal CPKT into pixel information PINF and control information CINF, and output the pixel information PINF and the control information CINF to the facsimile procedure controller  14 . 
     A data transmitter/receiver (that is, a LAN controller  17  and a LAN control circuit  18 ) are also connected to the connection/transfer controller  15 . The LAN controller  17  controls a protocol, such as TCP/IP (Transport Control Protocol/Internet Protocol), for data transfer to and from the LAN  4 . The LAN controller  17  is connected to the LAN control circuit  18  which is physically connected to the LAN  4  in order to transmit and receive control packet signals CPKT and pixel packet signals PPKT. 
     FIG. 4 shows a part of the control sequence of the facsimile communication apparatuses  10 A and  10 B, according to the first embodiment, up to transmission of a sheet of pixel information. Each element of the facsimile communication apparatus  10 A is denoted by a numerical symbol and a suffix A, while each element of the facsimile communication apparatus  10 B is denoted by a numerical symbol and a suffix B. First of all, when a call-out signal is sent from the facsimile machine  1   a  to the facsimile communication apparatus  10 A via the telephone line  2   a  (S 50 ), the terminal accommodation circuit  11 A detects the call-out, and informs the connection/transfer controller  15 A of the occurrence of call-out. The connection/transfer controller  15 A instructs the LAN controller  17 A to connect to the LAN  4 . Then, the LAN controller  17 A transmits an address inquiry signal based on TCP/IP to the LAN  4  (S 52 ). 
     When a confirmation response signal is returned to the facsimile communication apparatus  10 A via the LAN  4  (S 54 ), the facsimile communication apparatus  10 A transmits a connection request signal to the receiving side facsimile communication apparatus  10 B (S 56 ). Based on this connection request, the facsimile communication apparatus  10 B calls the addressed facsimile machine  7  via the telephone line  6 , and outputs a call-in signal to the facsimile machine  7  (S 58 ). When the facsimile machine  7  responds to the call-in signal, a response signal is transmitted to the facsimile communication apparatus  10 B (S 60 ). Upon receiving this response signal from the facsimile machine  7 , the facsimile communication apparatus  10 B transmits a call-connection response signal to the facsimile communication apparatus  10 A via the LAN  4  (S 62 ). Upon receiving the call-connection response signal, the facsimile communication apparatus  10 A sends a response signal to the facsimile machine  1   a  (S 64 ). At this point in time, the facsimile machine  1   a  is connected to the facsimile machine  7  via the telephone line  2 , the facsimile communication apparatus  10 A, the LAN  4 , the facsimile communication apparatus  10 B, and the telephone line  6 . 
     Then, the receiving side facsimile machine  7  successively transmits a non-standard function signal NSF, a called site identification signal CSI, and a digital identification signal DIS, which are portions of control information CINF, based on the ITU-T Recommendation T.30 (S 66 ). The facsimile procedure controller  14 B of the facsimile communication apparatus  10 B receives and decodes these signals, and supplies the decoded signals to the connection/transfer controller  15 B. The connection/transfer controller  15 B edits these signals into a control packet signal CPKT (NSF/CSI/DIS), and transmits the control packet signal to the LAN  4  via the LAN controller  17 B and the LAN control circuit  18 B (S 68 ). 
     In the transmission side facsimile communication apparatus  10 A, the LAN control circuit  18 A receives the control packet signal CPKT (NSF/CSI/DIS) sent via the LAN  4 , and outputs this control packet signal to the connection/transfer controller  15 A via the LAN controller  17 A. The connection/transfer controller  15 A decomposes the control packet signal (NSF/CSI/DIS) into three type of control information CINF, namely, a non-standard function signal NSF, a called site identification signal CSI, and a digital identification signal DIS. Then, the negligible non-standard function signal NSF is abandoned, while the called site identification signal CSI and the digital identification signal DIS are output to the facsimile-procedure controller  14 A. 
     The facsimile procedure controller  14 A controls the procedure control circuit  13  so that it transmits the called site identification signal CSI and the digital identification signal DIS, which comprise control information CINF, to the transmission side facsimile machine  1   a  via the telephone line  2  (S 70 ). Upon receiving the called site identification signal CSI and the digital identification signal DIS transmitted from the receiving side facsimile machine  7 , the facsimile machine  1   a  outputs a transmission site identification signal TSI and a digital command signal DCS, which are control information CINF (S 72 ). 
     When the control information CINF, which contains the transmission site identification signal TSI and the digital command signal DCS, is received by the facsimile communication apparatus  10 A via the telephone line  2 , these signals are edited into a control packet signal CPKT (TSI/DCS), which is then transmitted to the facsimile communication apparatus  10 B via the LAN  4  (S 74 ). The facsimile communication apparatus  10 B decomposes the received control packet signal CPKT (TSI/DCS) into a transmission site identification signal TSI and a digital command signal DCS, and successively transmits these signals to the facsimile machine  7  via the telephone line  6  (S 76 ). At this point in time, a facsimile communication link is established between the facsimile machines  1   a  and  7 . 
     After the facsimile communication link is established, the transmission side facsimile machine  1   a  transmits a training check signal TCF, which is control information CINF for training the pixel-information receiving modem  13   a , to the facsimile communication apparatus  10 A (S 78 ). The training check signal is used only in the analog-signal section, and it is not necessary for the LAN  4 . Accordingly, when the training of the modem  13   a  of the procedure control circuit  13 A is completed, the modem  13   a  returns a confirmation return signal CFR, which is control information CINF and informs of the fact that the modem  13   a  is ready to receive the pixel information, to the facsimile machine  1   a  (S 80 ). The same operation is performed in the receiving side facsimile communication apparatus  10 B. The modem  13   a  of the procedure control circuit  13 B sends a training check signal TCF to the facsimile machine  7  (S 82 ). When the training of the modem of the facsimile machine  7  is completed, the facsimile machine  7  returns a confirmation response signal CFR to the facsimile communication apparatus  10 B (S 84 ). At this time, the facsimile machine  1   a  starts transmitting the pixel information PINF. 
     The pixel data read by the facsimile machine  1   a  is encoded according to the coding rule based on the recommendation T.30 to create pixel information PINF. The produced pixel information PINF is modulated to produce an analog signal of the voice band by the 9600 bps modem built into the facsimile machine  1   a,  and this analog signal is transmitted to the facsimile communication apparatus  10 A via the telephone line  2  (S 86 ). The received analog signal is demodulated into digital form by the modem  13   a  of the procedure control circuit  13 . This demodulated pixel information PINF is supplied to the connection/transfer controller  15 A via the facsimile procedure controller  14 A, converted into a pixel packet signal PPKT, and transmitted to the LAN  4  via the LAN controller  17 A and the LAN control circuit  18 A (S 88 ). 
     The pixel packet signal PPKT sent via the LAN  4  is received at the LAN control circuit  18 B and the LAN controller  17 B of the facsimile communication apparatus  10 B, and is supplied to the connection/transfer controller  15 B. The connection/transfer controller  15 B converts the pixel packet signal PPKT into pixel information PINF, and temporarily stores the pixel information PINF in the memory  16 B. When the amount of pixel information PINF accumulated in the memory  16 B reaches a predetermined amount (for example, a data amount corresponding to a page), that amount of pixel information PINF is read out by the facsimile procedure controller  14 B, and is transmitted to the receiving side facsimile machine  7  by the procedure control circuit  13 B via the telephone line  6  (S 90 ). 
     FIG. 5 shows the communication sequence following the sequence of FIG. 4 (that is, after the completion of transmission of a page of pixel information from the facsimile machine  1   a ). When the transmission side facsimile machine  1   a  has transmitted a page of pixel information PINF, it generates a multi-page signal MPS, which is control information CINF (S 92 ). The facsimile procedure controller  14 A of the facsimile communication apparatus  10 A decodes this control information CINF, and outputs the decoded signal to the communication/transfer controller  15 A. The communication/transfer controller  15 A edits the multi-page signal MPS into a control packet signal CPKT (MPS), and outputs the control packet signal CPKT (MPS) to the LAN  4  via the LAN controller  17 A and the LAN control circuit  18 A (S 94 ). 
     This control packet signal CPKT (MPS) sent via the LAN  4  is received at the LAN control circuit  18 B and the LAN controller  17 B of the facsimile communication apparatus  10 B, and is supplied to the communication/transfer controller  15 B. The communication/transfer controller  15 B converts the received control packet signal CPKT (MPS) into a multi-page signal MPS, and outputs it to the facsimile procedure controller  14 B. This multi-page signal MPS is output from the facsimile procedure controller  14 B to the receiving side facsimile machine  7  via the procedure control circuit  13 B and the telephone line  6  (S 96 ). Upon receiving the multi-page signal MPS, the facsimile machine  7  outputs a message confirmation signal MCF, which is control information CINF, to the facsimile communication apparatus  10 B (S 98 ). 
     The facsimile communication apparatus  10 B edits the message confirmation signal MCF into a control packet signal CPKT (MCF), and transmits it to the facsimile communication apparatus  10 A via the LAN  4  (S 100 ). The facsimile communication apparatus  10 A converts the received control packet signal CPKT (MCF) into a message confirmation signal MCF, and transmits it to the facsimile machine  1   a  via the telephone line  2  (S 102 ). Upon receiving the message confirmation signal MCF, the facsimile machine  1   a  starts transmitting the pixel data of the next page as the pixel information PINF in the same manner as the first page was transmitted. 
     When the facsimile machine  1   a  is finished transmitting all the pixel information PINF, the facsimile machine  1   a  outputs an end-of-procedure signal EOP, which is control information CINF (S 110 ). The facsimile communication apparatus  10 A edits this end-of-procedure signal EOP into a control packet signal CPKT (EOP), and sends the control packet signal CPKT (EOP) to the facsimile communication apparatus  10 B via the LAN  4  (S 112 ). Upon receiving the control packet signal CPKT (EOP), the facsimile communication apparatus  10 B converts this packet signal into an end-of-procedure signal EOP, and sends it to the receiving side facsimile machine  7  via the telephone line  6  (S 114 ) When the facsimile machine  7  receives the end-of-procedure signal EOP, it returns a message confirmation signal MCF (S 116 -S 120 ). 
     When the facsimile machine  1   a  receives the message confirmation signal MCF from the facsimile machine  7 , it generates a disconnection command signal DCN, which is control information CINF (S 122 ). The facsimile communication apparatus  10 A edits the disconnection command signal DCN into a control packet signal CPKT (DCN), and transmits it to the facsimile communication apparatus  10 B via the LAN  4  (S 124 ). The facsimile communication apparatus  10 B converts the control packet signal CPKT (DCN) into a disconnection command signal DCN, and sends it to the receiving side facsimile machine  7  via the telephone line  6  (S 126 ). At this point of time, facsimile communication between the facsimile machines  1   a  and  7  is finished. 
     After finishing the communication, the facsimile machines la and  7  disconnect themselves from the telephone lines  2  and  6 , respectively (S 128 ). These disconnected states are reported to the facsimile communication apparatuses  10 A and  10 B, whereby the facsimile communication apparatuses  10 A and  10 B disconnect themselves from the LAN  4  (S 130 ). As has been described above, each of the facsimile communication apparatuses  10 A and  10 B has a procedure control circuit  13  having a modem  13   a , which is the same standard as the facsimile machine  1   a,  and a facsimile procedure controller  14  which executes a transfer control procedure according to the recommendation T.30. 
     These elements allow the control information CINF and the pixel information PINF to be transferred between the facsimile machine  1   a  and the facsimile communication apparatus  10 A according to the facsimile procedure, and they also allow the control packet signal CPKT and the pixel packet signal PPKT to be transferred between the facsimile communication apparatuses  10 A and  10 B according to the procedure of the LAN  4 . Transmitted data is temporarily stored in the memory, and a predetermined amount of data is output to the receiving side facsimile machine. Thus, facsimile communication is achieved via data communication networks, such as the LAN  4 , with little transmission errors and by efficiently using transfer capacity. 
     2. Second Embodiment 
     FIG. 6 is a hardware block diagram of the facsimile communication apparatus  10 A according to the second embodiment of the invention. The facsimile communication apparatus  10 B also has the same structure as that shown in FIG.  6 . In this embodiment, the facsimile communication apparatus  10 A has a CPU  37  in place of the facsimile procedure controller  14 , the LAN controller  17 , and the communication/transfer controller  15 . The facsimile communication apparatus  10 A also has a CD-ROM driver  34  for reading out a program from a CD-ROM  36 , and a hard disc drive  38  for storing the program read out from the CD-ROM  36 . The program stored in the hard disc drive  38  is read out by the memory  16 , and is executed. In this specification and in the appended claims, portable recording media including the CD-ROM  36 , fixed storing apparatuses including the hard disc drive  38 , and volatile storing devices including the memory  16  are all referred to as program recording units. 
     The program stored in the program recording unit may be executed directly by the CPU  37 , or it may be decoded prior to being executed by the CPU  37  if it is stored in an encoded format. The program stored in the CD-ROM  36  has program modules for causing the CPU  37  to execute the operations performed by the facsimile procedure controller  14 , the connection/transfer controller  15 , and the LAN  4 , shown in FIG.  3 . Based on these program modules, the CPU  37  performs the same operations as the facsimile communication apparatus  10 A shown in FIGS. 3 thru  5 . In this embodiment, the operations of the facsimile communication apparatus  10 A can be easily changed by simply changing the CD-ROM  36 . 
     3. Third Embodiment 
     In the third embodiment, an IP network (Internet Protocol network)  50  according to the IETF (Internet Engineering Task Force) is used as the data communication network in place of the LAN  4  shown in FIG.  1 . The “IP network” includes both the Internet and intranets. The facsimile communication apparatus  10 A according to this embodiment has an IP network control circuit and an IP network controller in place of the LAN control circuit  18  and the LAN controller  17  shown in FIG.  3 . The other hardware structure is the same as that shown in FIG. 3, and the explanation will be omitted. 
     FIG. 7 shows a part of the control sequence of the facsimile machine  1   a,  according to the third embodiment, up to transmission of a sheet of pixel information to the facsimile machine  7 . The facsimile machines  1   a  and  7  are connected to the facsimile communication apparatuses  10 A and  10 B via the telephone lines  2  and  6 , respectively, as in the first embodiment. When the facsimile communication apparatus  10 A receives a request for connection to the facsimile machine  7  from the facsimile machine  1   a  (S 200 ), the facsimile communication apparatus  10 A accesses the address information storing device  16  (S 202 ) to obtain the IP address of the facsimile communication apparatus  10 B, to which the facsimile machine  7  is connected (S 204 ). Then, the facsimile communication apparatus  10 A requests the facsimile communication apparatus  10 B to connect itself to the facsimile machine  7  (S 206 ) In response to this request, the facsimile communication apparatus  10 B connects itself to the facsimile machine  7  (S 208  and S 210 ). Upon the establishment of the connection between the facsimile communication apparatus  10 B and the facsimile machine  7 , the facsimile communication apparatuses  10 A and  10 B cooperate to provide a communication path between the facsimile machines  1   a  and  7 . 
     As in the first embodiment, when the facsimile machine  1   a  receives a connection response signal (S 212  and S 214 ), followed by a non-standard function signal NSF, a called site identification signal CSI, and a digital identification signal DIS (S 216  through S 220 ), from the facsimile machine  7  via the facsimile communication apparatuses  10 A and  10 B, the facsimile machine  1   a  transmits a transmission site identification signal TSI, a digital command signal DCS, and a training check signal TCF (S 222 ). Then, upon receiving a receipt-ready confirmation signal CFR from the facsimile communication apparatus  10 A (S 224 ), the facsimile machine  1   a  starts transmitting the pixel data (S 230 ). Prior to this, the facsimile communication apparatus  10 A transfers the transmission site identification signal TSI and the digital command signal DCS to the facsimile communication apparatus  10 B (S 226 ) upon transmitting the receipt-ready confirmation signal to the facsimile machine  1   a  (S 224 ). 
     While the facsimile machine  1   a  is transmitting the pixel data (S 230 ), the receiving side facsimile communication apparatus  10 B and the facsimile machine  7  are transferring control signals to each other (S 228  and S 234  through S 242 ). In other words, the receiving side facsimile communication apparatus  10 B stores the pixel data sent from the facsimile machine  1   a  via the facsimile communication apparatus  10 A in the memory  3   f , while it transfers control signals to and receives control signals from the facsimile machine  7  (S 232 ). 
     The facsimile communication apparatus  10 B starts transferring the pixel data to the facsimile machine  7  after a predetermined amount of pixel data has been stored in the memory (S 246 ) in order to avoid undesirable interruption of the communication between the facsimile machines  1   a  and  7 , which generally occurs due to a transfer delay arising in the IP network  50 . Prior to this, if a predetermined amount of data has not been accumulated in the memory when the facsimile communication apparatus  10 B receives the receipt-ready confirmation signal CFR (S 242 ), the negotiation sequence—that is, transmission of the transmission side identification signal TSI, the digital command signal DCS, and the receipt-ready confirmation signal CFR to the facsimile machine  7  (S 230  through S 242 )—is repeated in order to gain time for further accumulation of pixel data in the memory  3   f.    
     According to the third embodiment, the facsimile communication apparatus  10 B can start transmission of pixel data after a sufficient amount of pixel data is accumulated in the memory  3   f . Accordingly, even if the communication rate of the IP network  50  drops due to an increase in traffic, the facsimile communication apparatus  10 B can continuously convert the pixel data read out from the memory  3   f  into analog signals machine  7  at a constant rate. If the pixel data is lost, the lost data can be retransmitted to the facsimile communication apparatus  10 A, during which the pixel data read out from the memory  3   f  are continuously transmitted to the receiving side facsimile machine  7  without cutting off communication. Thus, this arrangement can prevent an unexpected shutoff of the communication between the facsimile communication apparatus  10 B and the facsimile machine  7  due to a decrease in communication rate or data loss. 
     4. Fourth Embodiment 
     In the previous embodiment (i.e., the third embodiment), the facsimile communication apparatus  10 B stores a predetermined amount of pixel data in the memory  3   f . However, if the communication rate between the facsimile communication apparatus and the facsimile machine  7  is relatively slow, it takes time to transmit the pixel data stored in the memory  3   f  to the facsimile machine  7 . In such a case, it is not necessary to store a great amount of pixel data in the memory  3   f . In view of this, too much pixel data in excess of a desirable amount may occasionally be accumulated in the memory in the third embodiment. In addition, a sequence lag which generally arises between the transmission side facsimile machine  1   a  and the receiving side facsimile machine  7  becomes large and, as a result, a communication error is likely to occur in the transmission side facsimile machine  1  at a page boundary due to response wait time-out. 
     Furthermore, in the third embodiment, the facsimile communication apparatus  10 B repeats the negotiation sequence (S 212  through S 216 ) if a predetermined amount of pixel data has not been accumulated in the memory at the time of receipt of a CFR from the receiving side facsimile machine  7 . During this negotiation sequence, too much pixel data exceeding the desirable amount is accumulated because the negotiation sequence generally takes time. This also causes a sequence lag between the transmission side facsimile machine  1   a  and the receiving side facsimile machine  7 , and the time when the receiving side facsimile machine  7  has fully received a page of pixel data is delayed. As a result, a communication error may occur at a page boundary in the transmission side facsimile machine  1   a  due to response wait time-out. In order to overcome these problems, a real-time facsimile communication system which can absorb a delay in the IP network and allow stable and highly successful communication is provided in the fourth embodiment. 
     FIG. 8 shows the operation flow of the facsimile communication apparatus  10 B according to the fourth embodiment. The facsimile communication apparatus  10 B has a standard hardware structure as in the third embodiment. When the facsimile communication apparatus  10 B receives a request for connection to the facsimile machine  7  from the facsimile communication apparatus  10 A, it informs the facsimile machine  7  of the occurrence of call-in, and connects itself to the facsimile machine  7  (S 300 ). Then, the facsimile communication apparatus  10 B reads the communication rate between the facsimile machines  1  and  7  from the control signal DCS received from the facsimile machine  1   a,  and calculates the minimum amount of pixel data that must be stored in the memory in order to continuously transmit the pixel information to the facsimile machine  7  for a predetermined period of time (S 302 ). Then, the facsimile communication apparatus  10 B transmits a transmission site identification signal TSI, a digital command signal DCS, and a training check signal TCF to the facsimile machine  7  for the purpose of communication training with the facsimile machine  7  (S 304 ). When the facsimile communication apparatus  10 B receives pixel data from the facsimile communication apparatus  10 A (S 306 ), it stores the pixel data in the memory  3   f  (S 308 ). 
     If the facsimile communication apparatus  10 B has already received a control signal CFR from the facsimile machine  7  (S 310 ), it determines if the minimum necessary amount of pixel data calculated in S 302  has been accumulated in the memory  3   f  (S 312 ). If so, the facsimile communication apparatus  10 B starts transmitting the pixel data to the facsimile machine  7  (S 314 ). Meanwhile, the receiving side facsimile machine  7  transmits a receiving-ready confirmation signal CFR, and if it does not receive any pixel data even after a predetermined period of time T has passed since the transmission of the receiving-ready confirmation signal CFR, it again transmits a non-standard function signal NSF according to the Recommendation T.30. The facsimile communication apparatus  10 B stores the predetermined time T (from the transmission of the receiving-ready confirmation signal CFR to immediately before the transmission of the non-standard function signal NSF) in advance. 
     If the minimum necessary amount of pixel data has not been accumulated in the memory in S 312 , the facsimile communication apparatus  10 B determines whether said predetermined time T has already elapsed (S 316 ). 
     If time T has not passed yet in S 316 , the process returns to S 306 , and the pixel data is continuously stored in the memory  3   f . If time T has already passed in S 316 , the facsimile communication apparatus  10 B sets a flag that represents the receiving sate of the receiving-ready confirmation signal CFR to “No Receipt” (S 318 ), and the process returns to the training sequence (S 304 ). Accordingly to this operation flow, the communication procedure does not have to return to the transmission of the non-standard function signal NFS, and the facsimile machine  7  can start receiving the pixel data earlier. 
     FIG. 9 illustrates an example of software function of the facsimile communication apparatus  10 B according to the fourth embodiment of the invention. The facsimile communication apparatus  10 B has an executing unit  22   a  and a data unit  22   b  as structural elements of the software. The executing unit  22   a  comprises an IP communication controller (IPC)  30 , an IP data analyzer (DAL)  31 , a facsimile communication controller (FCL)  32 , a pixel data storage controller (STM)  33 , and a timing controller (TQM)  34 . The data unit  22   b  comprises a pixel data storage  40  and a pixel data storage amount manager  41 . The pixel data storage  40  stores pixel data information together with data representing the current storage amount of pixel data. The pixel data storage amount manager  41  stores the optimum transmission time that is converted from the optimum storage amount of pixel data. The facsimile communication apparatus  10 A has the same structure as the facsimile communication apparatus  10 B, and further explanation will be omitted. 
     The operation of the major elements of the receiving side facsimile communication apparatus  10 B, which are performed during the operation flow shown in FIG. 8, will be explained with reference to FIG.  9 . When the IP communication controller  30  receives IP data from the transmission side facsimile communication apparatus  10 A via the IP network  50 , it requests the IP data analyzer  31  to analyze the IP data. If the received IP data is a T.30 signal consisting of control signals TSI and DCS as a result of the analysis, the IP data analyzer  31  requests the facsimile communication controller  32  to send this IP data to the facsimile machine  7 . The facsimile communication controller  32  transfers the control signals TSI and DCS to the facsimile machine  7  and, at the same time, it obtains from the DCS the communication rate of the facsimile communication which is to take place in this sequence, and reports the communication rate to the pixel data storage controller  33 . 
     On the other hand, if the received IP data is pixel data, then the IP data analyzer  31  requests the pixel data storage controller  33  to temporarily store this IP data. In response to this request, the pixel data storage controller  33  stores the IP data in the pixel data storage  41  and, at the same time, it updates the storage amount information. The pixel data storage controller  33  reads out the optimum data transmission time from the pixel data storage manager  41 , calculates the optimum amount of pixel data that should be stored by multiplying the communication rate by the optimum transmission time, and stores this optimum value in the pixel data storage manager  41 . When the facsimile communication controller  32  receives the CFR from the receiving side facsimile machine  7 , it inquires of the pixel data storage controller  33  as to whether or not the optimum amount of pixel data has already been stored. 
     The pixel data storage controller  33  reads out the optimum pixel-data storage amount from the pixel data storage manager  41  and, at the same time, it reads the amount of pixel data that has been stored in the pixel data storage  40  by that point of time and compares it with the optimum value. If the optimum amount of pixel data has already been accumulated, the pixel data storage controller  33  informs the facsimile communication controller  32  that the pixel data can now be transmitted. The facsimile communication controller  32  requests the pixel data storage controller  33  to read out the pixel data, and it starts transferring the pixel data to the facsimile machine  7 . On the other hand, if the optimum amount of pixel data has not been accumulated in the comparison step, then the facsimile communication controller  32  instructs the timing controller  34  to restart the facsimile communication controller  32  after a predetermined time interval, and the process is interrupted. 
     The timing controller  34  restarts the facsimile communication controller  32  after a predetermined time, and the facsimile communication controller  32  again inquires of the pixel data storage controller  33  as to whether the optimum amount of pixel data has been accumulated. These steps are repeated until the optimum amount of pixel data has been accumulated in the data storage  40 . During the interruption, the facsimile communication controller  32  does not transmit any signals or pixel data to the receiving side facsimile machine  7 . 
     If no pixel data is transmitted to the receiving side facsimile machine  7 , even after a predetermined period of time has passed since the transmission of the receiving-ready confirmation signal CFR, the facsimile machine again transmits a non-standard function signal NSF according to the Recommendation T.30. The timing controller  34  stores in advance the time T from the transmission of the receiving-ready confirmation signal to immediately before the transmission of the non-standard function signal NSF, and if time T has elapsed, it informs the facsimile communication controller  32  of the time limit. Then, the facsimile communication controller  32  restarts from the step of transmitting a transmission site identification signal TSI to the receiving side facsimile machine  7 , and allows the pixel data to be continuously stored. This operation flow can allow the receiving side facsimile machine  7  to finish receiving the pixel data earlier, as compared with the case in which the process returns to the retransmission of the non-standard function signal NSF. 
     According to this embodiment, the minimum and necessary amount of pixel data, which is determined by the communication rate negotiated between the transmission side facsimile machine  1   a  and the receiving side facsimile machine  7 , is stored. This arrangement can prevent a transmission site identification signal TSI from being transmitted as much as possible before the minimum necessary amount of pixel data is accumulated, even after the receipt of the receiving-ready confirmation signal TSI. Consequently, accumulation of excessive amount of pixel data, as well as communication errors due to inappropriate accumulation of pixel data, can be prevented. Thus, a stable and real-time facsimile communication can be achieved. 
     Although the present invention has been described with reference to the specific embodiments, the present invention is not limited to these embodiments, and it will be apparent to those skilled in the art that there are many changes and substitutions which can be made without departing from the scope of the invention. 
     Examples of such changes and substitutions are listed below. 
     (a) Although the LAN  4  or the IP network  50  are used as data communication networks in the embodiment, other types of data communication networks can be used. 
     (b) The facsimile procedure controller  14 , the connection/transfer controller  15 , and the LAN controller  17  have been described as independent elements in the embodiment. However, these elements may be realized as software executed by a single CPU. This can facilitate the hardware structure of the facsimile communication apparatus  10 . 
     (c) Even if the facsimile machines  1   a  and  7  employ non-standard procedures which are not based on Recommendation T.30, continuous pixel data transmission can be achieved, without interrupting the facsimile communication, by adjusting the pixel data transmission timing as described in the embodiments. 
     Because the facsimile communication apparatus according to the first invention has a memory for temporarily storing a predetermined amount of pixel packet signals received via a data communication network, stable facsimile communication can be maintained without an unexpected breakup in the middle of transmission, even if the data-transfer rate differs between the transmission side facsimile machine  1   a  and the receiving side facsimile machine  7 . In addition, a mechanism for absorbing a delay in the UP network and for preventing excessive amount of accumulation of pixel data is provided and, consequently, a facsimile communication system having a high communication-success rate (with little communication error) can be achieved.