CA2276775C

CA2276775C - Data communication device and data communication method

Info

Publication number: CA2276775C
Application number: CA002276775A
Authority: CA
Inventors: Takafumi Higuchi
Original assignee: Matsushita Graphic Communication Systems Inc
Current assignee: Panasonic System Solutions Japan Co Ltd
Priority date: 1997-11-05
Filing date: 1998-11-05
Publication date: 2001-10-02
Anticipated expiration: 2018-11-05
Also published as: JPH11146171A; EP0973323A4; JP3426122B2; US6606375B2; DE69836906D1; HK1023247A1; US6449349B1; US20020181679A1; DE69836906T2; CN1158852C; WO1999023814A1; EP0973323B1; BR9806845A; CA2276775A1; KR100339167B1; EP0973323A1; CN1243632A; ATE352168T1; KR20000069871A

Abstract

Control information on the modem for each address is stored. At the time of communication, the modem used is operated in accordance with the stored control information and a pre-communication procedure is simplified to transmit data. If the simplified pre-communication procedure does not progress normally, the procedure is changed to a second communication procedure with a slower speed after a predetermined lapse of time to continue the communication. If abnormality occurs after the simplified pre-communication procedure, the control information stored in a memory means are erased/updated. Therefore, the time for the pre-communication procedure is shortened and, further, the mounted shortened procedure function always operates properly even if the error rate of the communication is high or the line characteristics are changed.

Description

DESCRIPTION
DATA COMMUNICATION APPARATUS AND DATA COMMUNICATION
METHOD
Technical Field The present invention relates to a data communi-cation apparatus and a data communication method, which shortens the time needed for a previous-procedure to be performed prior to data communication using a modem, such as facsimile communication.
Background Art Recently, in data communication apparatus, data communication using a V.34 modem (33.6 kbps), which is conformed to recommends of the ITU-T. The ITU-T
also recommends T30 ANEXF (so-called Super G3) as facsimile communication standards using the V.34 mo-dem for facsimile apparatuses. A previous-procedure for facsimile communication is carried out according to the standards procedure, after which communication of image data is executed.
Such a communication protocol will be explained based on the sequence chart illustrated in FIG. 1.
FIG. 1 is a control signal view for a communication protocol for facsimile communication according to prior art.
Referring to FIG. 1, reference character 19a de-notes a communication procedure for selecting a modu-lation mode from among a V34 half-duplex, V34 full duplex, V17 half-duplex, etc. Reference character 19b denotes a communication procedure for line probing to check a line and determine various kinds of parameters. Reference character 19c denotes a communication procedure for modem training. Refer-ence character 19d denotes a communication procedure for setting a modem parameter. Reference character 19e denotes a communication procedure for exchanging a facsimile control signal. And, reference character 19f denotes a data communication procedure for the primary channel. The upper side in the diagram is a sequence for a caller modem, and the lower side is a sequence on an answer modem, and the sequences pro-gress from left to right.
The above communication protocols will be speci-fically described as follows:
First, in the communication procedure 19a for se-lecting a modulation mode, the selection of a modula-tion mode and communication procedure, which permit communication between a caller modem and an answer modem, through a V.21 modem (300 bps, full-duplex), is carried out after a line connection is established.
A facsimile apparatus using a V.34 modem selects a V.34 modem as the modulation mode and facsimile com-munication as a communication procedure.
After that, in the communication procedure 19b for line probing, the caller modem transmits a line probing tone. The line probing tone is received by the answer modem, a line inspection is carried out, and a training parameter is selected based on the re-sult of the line inspection.
In the communication procedure 19c for modem training, the caller modem sends training signals based on the training parameter selected under the line probing communication procedure 19b, while the answer modem receives the training signals, learns a filter coefficient for an adaptive equalizer for com-pensating the line characteristic and checks the re-ception quality of the training signals.
In the communication procedure 19d for selecting a modem parameter, modem parameters are negotiated between the caller modem and the answer modem in full-duplex communication at 1200 bps. As a result, an optimal modem parameter is selected from the modem parameters preset in the apparatus, the result of the line inspection and the inspection of the reception quality of the training signals.
In the communication procedure 19e for a fac-simile control signal, negotiation of facsimile con-trol signals NSF, CSI, DIS, TSI, DCS, CFR, etc. is executed in full duplex communication at 1200 bps.
Then, in the data communication procedure 19f, image data is transmitted from the caller modem in half-duplex communication at 2400 bps to 33. 6 kbps.

Image data is received by the answer modem. In the case of performing communication at the maximum com-munication rate of 33. 6 kbps, image data can trans-mit in approximately three seconds per a sheet of paper of size A4.
The caller and answer modes, which execute the aforementioned communication protocol, carry out com-munication in accordance with the training parameter selected under the communication procedure 19b for communication line probing and the modem parameter selected under the communication procedure 19d for selection of a modem parameter. To compensate the line characteristic, the receiver modem executes com-munication using the filter coefficient that has learned in the modem training 19b. This ensures op-timal data communication according to the line qual-ity.
However, the above-described prior art structure involves five channels of a procedure before starting sending image data after line establishment, and thus requires about 7 seconds. By contrast, since elec-tric transmission of a single sheet of image data at the maximum communication rate of 33.6 kbps takes about 3 seconds, the procedures requires over 60~ of the entire time of 11 seconds required for transmis-sion of one sheet of an original including the later-procedure about 1 second. This time needed for the previous-procedure gets greater as the number of transmission/reception lines increases, and generates wasteful time and communication cost.

5 Disclosure of Invention In consideration of the above-mentioned problems, an object of the present invention is to provide a data communication apparatus which can shorten time for setting various kinds of parameters of a modem and time f or a previous-procedure including time for modem training before the image transmission.
Also, an object of the present invention is to provide a data communication apparatus such that a supported short previous-procedure function appropri-ately operates even when a communication error rate is high or line characteristics are changed.
More specifically, there is provided a data com-munication apparatus comprising:
storing means for storing various kinds of modem control information for each destination in associa-tion with an operation key;
calling means for generating a call to said des-tination by a transmission command from said opera-tion key to start communication; and communication control means for transmitting a shift notify signal indicative of the shift to a pre-vious-procedure for short communication in a case of communication using said calling means, thereafter controlling the modem based on said various kinds of control information so as to shorten a previous-procedure and carry out data transmission.
The data communication apparatus according to the first aspect of the present invention comprise stor-ing means for storing various kinds of modem control information for each destination in associate with an operation key;
calling means for generating a call to said des-tination by a transmission command from said opera-tion key to start communication; and communication control means for transmitting a shift notify signal indicative of a shift to a short previous-procedure in a case of communication using said calling means, thereafter controlling the modem based on said various kinds of control information so as to shorten a previous-procedure and carry out data transmission.
According to the above-mentioned structure, com-munication to the destination registered in the op-eration key is executed in the short previous-procedure based on control information stored in storing means, so that an operator can shorten commu-nication time by considerably simple operation.
Since it is unnecessary to obtain modem control in-formation suitable for the destination by communica-tion in the previous-procedure, time required for a previous-procedure can be greatly shortened. Control information described here is time for modem parame-ter or modem training.
The second aspect of the present invention, in the data communication apparatus of the first aspect, the communication control means transmits the shift notify signal that indicates shift to a short previ-ous-procedure in place of a calling menu signal, re-sponse to a deformed answer signal incoming from an answer side apparatus with respect to a calling sig-nal transmitted in previous-procedure conformed to Recommendation ITU/V.34.
According to the above-described structure, the apparatus in answer side receives either the calling menu signal in V.34 protocol or the shift notify sig-nal indicating shift to the short previous-procedure.
Since the apparatus has only to identify these sig-nals, the apparatus can receive the shift notify sig-nal to the short previous-procedure without requiring a greatly change in a receiving signal processing circuit.
The third aspect of the present invention, in the data communication apparatus of the first or second aspect, the communication control means confirms whether or not various kinds of the modem control in-formation are stored in said storing means prior to the shift to the short previous-procedure, and ex-ecutes the short previous-procedure only when said control information is stored.
According to the above-mentioned structure, con-s trol of communication control means can be simply carried out. Namely, communication control means check a writing state of storing means, and select whether or not control information is written to storing means, so that communication control means may change the ON/OFF state of short previous-procedure, easily.
The forth aspect of the present invention, in the data communication apparatus of the first or second aspect, the data communication apparatus farther com-prises parameter registering means for storing vari-ous kinds of the modem control information obtained in the previous-procedure executed with respect to the destination registered in said storing means in a state that only destination information corresponding to said operation key is stored in said storing means.
According to the above-described structure, if the destination information has only to be registered correspond to the operation key, control information actually obtained in communication with the destina tion in the normal previous-procedure is automati-cally stored, and subsequent communication can be automatically executed in the short previous-procedure. Therefore, this gives a good operability to the operator.
Destination information described here is one that specifies the destination such as a destina-tion's name, a telephone number, ID information.
The fifth aspect of the present invention, the data communication apparatus of the forth aspect, the apparatus further comprises error detecting means for detecting an error of communication, and the parame-ter registering means does not execute the registra-tion of control information when error detecting means detects an error in the previous-procedure for registering the parameter for short previous-procedure.
The above-described parameter registering means in the ffifth aspect automatically registers various kinds of the modem control information obtained in the previous-procedure. However, if control informa-tion in the previous-procedure where a error has been occurred is registered, there is a high possibility that an error will occur again. For this reason, registration of control information is not carried out. Since the short previous-procedure is not ex-ecuted in next communication, there can be avoided a case in which communication time is increased due to the short previous-procedure execution error.
The six aspect of the present invention, in the data communication apparatus of the fifth aspect, the parameter registering means executes once stores con-trol information obtained in the normal previous-procedure in said storing means, after which said 5 control information is erased, thereby executing processing in which no registration of control infor-mation is carried out.
According to the above-mentioned structure, since processing for prohibiting registration of parameter 10 (control information) to be carried out first and processing for erasing control information registered in storing means can be executed in the same process-ing flow, simplification of processing and software can be improved.
The seven aspect of the present invention, the data communication apparatus of one to six aspect, when the short previous-procedure proceeds abnormally, said communication control means performs a shift to communication by the normal previous-procedure or second communication procedure having low communica-tion speed so as to continue communication after a lapse of a predetermined period of time.
According to the above-mentioned structure, when the short previous-procedure does not normally pro-ceed within a predetermined period of time, communi-cation in the other communication procedure whose communication speed is low is continued. For this reason, there can be avoided a case in which a commu-nication error occurs by failure in the short proce-dure. In this case, the communication protocol to be shifted may be a communication protocol whose commu-nication speed is the same as that of the short pre-vious-procedure execution time or a communication protocol whose communication speed is lower than that of the short previous-procedure execution time.
The eight aspect of the present invention, the data communication apparatus of the seven aspect, the second communication procedure is a communication protocol according to Recommendation ITU/T.30, and the predetermined period is time for which NSF/CSI/DIS signals of T.30 can be received twice or more after shift to the second communication proce-dure.
According to the above-mentioned structure, in the case of failure in the short previous-procedure, shift to T.30 communication procedure is carried out, and a standby state for a control signal of 300 bps is set. NSF/CSI/DIS signals are repeatedly transmit-ted. For this reason, even if first reception of a control signal ends in failure, at least two signal reception times can be ensured not to generate a com-munication error. Therefore, even if the apparatus on the destination is changed to one, which is not equipped with the short previous-procedure, or the short previous-procedure ends in failure, shift to T.30 protocol can be surely executed.
The nine aspect of the present invention, the da-to communication apparatus of the one to six aspect, when the short previous-procedure does not proceeds normally, the communication control means change the procedure from the short previous-procedure to a sec-and communication procedure having low communication speed so as to continue communication after the num-ber of retrial times of said short previous-procedure reaches a fixed value.
Although the shift to the second communication procedure was executed after a lapses of a predeter-mined period of time in the seven aspect, the shift to the second communication procedure is executed by the number of retrials of the short previous-procedure in the nine aspect.
The ten aspect of the present invention, in the data communication apparatus of the one to fourth as-pect, the apparatus further comprises error detecting means for detecting an error of communication, where-in when said error detecting means detects an error after starting execution of the short previous-procedure, said communication control means maintains destination information stored in said storing means on one hand and erases only the corresponding various kinds of control information in said storing means on the other hand.
In other words, if some error occurs after the start of executing the short previous-procedure and control information used at this time is used in the future, there is a high possibility that an error will occur again. For this reason, such information is erased. Such communication error occurring after the start of executing the short previous-procedure can be applied to both a case in which the previous-procedure is executing and a case in which data com-munication is executing after the previous-procedure is accomplished. However, treatment of control in-formation thereafter differs, depending on whether or not the short previous-procedure is ended The eleven aspect of the present invention, in the data communication apparatus of the seven aspect, the apparatus further comprises parameter registering means for executing a normal previous-procedure in the same call so as to newly store various kinds of the modem control information obtained in the ex-ecuted normal previous-procedure in said storing means when the short previous-procedure does not pro-ceeds normally.
According to the above-mentioned structure, con-trol information stored in storing means is automati-cally updated in the same call. Therefore, next com-munication is started in the short previous-procedure.

There is a case in which an error occurs again based on updated control information. However, if such oc-currence of error is repeated, the execution of the short previous-procedure itself is prohibited as de-scribed later.
The twelve aspect of the present invention, in the data communication apparatus of the ten aspect, the error detecting means determines an error of com-munication when a data transmission error rate of communication obtained after executing the short pre-vious-procedure or the normal communication previous-procedure increases to a predetermined value or more.
According to the above-described structure, for example, when the error gradually increases during communication, control information registered in storing means is determined as an unsuitable parame-ter. This is particularly useful for a case in which line characteristic is better than a normal case at a parameter registration time.
The thirteen aspect of the present invention, in the data communication apparatus of the ten aspect, the error detecting means determines an error of com-munication when a data transmission error rate of communication obtained after executing the short pre-vious-procedure or the normal previous-procedure is lower than a data transmission error rate of a commu-nication protocol whose speed is slower than communi-cation speed.
According to the above-described structure, there can be avoided a disadvantage in which communication is repeated at communication speed which is lower 5 than the normal communication speed. In contrast to the previous case, this is particularly useful for a case in which line characteristic is worse than a normal case at a parameter registration time.
The fourteen aspect of the present invention, in 10 the data communication apparatus of the twelve aspect or thirteen aspect, the apparatus further comprises parameter registering means for storing various kinds of the modem control information obtained in a next normal previous-procedure executed with respect to 15 the destination in said storing means after erasing control information from said storing means.
According to the above-mentioned structure, next communication is executed in the normal previous-procedure. At this time, registration of modem con-trol information is automatically performed, and next communication is automatically executed in the short previous-procedure.
The fifteen aspect of the present invention, in the data communication apparatus of the first to fourth aspect, when the number of error generations of the short previous-procedure or an error rate to the number of short previous-procedure executions ex-ceeds a predetermined value, the short previous-procedure with respect to the destination in subse-quent communication is prohibited from being executed.
According to the above-mentioned structure, there can be avoided a case in which the short previous-procedure is executed in accordance with control in-formation having a high error rate to generate an er-ror repeatedly. The error rate may be calculated at the time when the short previous-procedure execution time reaches a predetermined value, or the number of errors may be simply counted. When the error rate is high, the execution of the short previous-procedure is prohibited at the earliest time, so that the num-ber of times of executing waste short previous-procedure can be reduced.
To count the number of errors, as described in aspect sixteen, the apparatus comprises an error counter for counting a number of error generations of short previous-procedure, wherein said error counter counts up every time when various kinds of control information stored in said storing means are erased.
The seventeen aspect of the present invention, in the data communication apparatus of the sixteen as-pect, the error counter determines whether or not communication is one that is started in the short previous-procedure before counting up, and the error counter executes no counting operation when a result of said determination is no.
According to the above-mentioned structure, the error counter can surely perform the counting opera-tion. Particularly, in a case where control informa-tion is erased from storing means in the normal com-munication protocol as described in aspect ten, the counting operation of the error counter is prohibited, so that no error occurs in the count value.
The eighteen aspect of the present invention, in the data communication apparatus of the fifteen as-pect, the communication control means confirms wheth-er or not various kinds of the modem control informa-tion are registrable in said storing means prior to the shift to the short previous-procedure, and ex-ecutes no short previous-procedure when various kinds of the modem control information are non-registrable.
According to the above-described structure, when the error often occurs in the short previous-procedure, registration of control information to storing means is prohibited so that the execution of the short previous-procedure itself is prevented. At this time, if registration of control information to storing means is prohibited, the modem parameter is stored, after which communication in the normal com-munication protocol is started. Therefore, a waste short previous-procedure in which the error occurs again is not executed.

The nineteen aspect of the present invention, in the data communication apparatus of the eighteen as-pect, the apparatus further comprises parameter reg-istering means for storing various kinds of the modem control information obtained in the normal previous-procedure, wherein prohibition of executing the short previous-procedure is carried out by prohibiting said various kinds of the modem control information from being written to said parameter registering means.
According to the above-mentioned structure, for example, the prohibition of various kinds of modem control information to storing means by parameter registration means based on software, thereby making it possible to prohibit the short previous-procedure from being executed easily.
The twenty aspect of the present invention, in the data communication apparatus of the first to fourth aspect, the apparatus further comprises op-erating means for changing a destination's name stored in said storing means or a destination's tele-phone number; and memory controlling means for auto-matically erasing all information of a relevant in-formation storing area including modem control infor-mation stored in association with said destination's telephone number when there is a change in said des-tination's telephone number input by said operating means.

According to the above-mentioned structure, the parameter can be registered in association with a new destination's telephone number. When the telephone number is changed, the line characteristic is also changed in many cases. However, control information can be erased and updated in a state that the opera-for has no awareness thereof. Control information to be erased here includes short previous-procedure reg-istration prohibition information, that is, all in-formation stored in association with the destina-tion's telephone number.
The twenty-one aspect of the present invention, in the data communication apparatus of the first to fourth aspect, the apparatus further comprises op-erating means for inputting an identification code peculiar to a self-apparatus; and memory controlling means for automatically erasing all information of a relevant information storing area including modem control information stored in association with all telephone numbers destination-registered when there is a change in said identification code input by said operating means.
According to the above-mentioned structure, when the telephone number of the self-apparatus is changed, all information including control information and short previous-procedure registration prohibition in-formation can be automatically erased without execut-ing the operation by the operator.
The twenty-two aspect of the present invention, the apparatus further comprises parameter registering means for storing various kinds of the modem control 5 information obtained in a next normal previous-procedure executed with respect to a destination in said storing means in a state that only the destina-tion corresponding to an operation key is stored in storing means. Thereby, the automatic registration 10 of parameter can be executed with respect to storing means in which control information has been automati-cally erased in next communication.
The twenty-three aspect of the present invention, the apparatus further comprises memory control means 15 for automatically erasing all information of a rele-want information storing area including modem control information stored in association with all telephone numbers destination-registered when an error continu-ously occurs in the short previous-procedure executed 20 with respect to a plurality of destinations.
According to the above-mentioned structure, on the presumption that the reason why a continuous er-ror occurs in the short previous-procedure lies in a change in the kind of line to which the self-apparatus is connected, the execution of the short previous-procedure can be prohibited. Therefore, in subsequent communication, the normal communication is sequentially executed, and new control information can be registered.
The twenty-four aspect of the present invention, in the data communication apparatus of the first to fourth aspect, said control information is deleted from said storing means after a lapse of a predeter-mined period of time from registration of control in-formation to said storing means so as to execute an update of control information by parameter register-ing means.
According to the above-mentioned structure, modem control information to be registered in memory means can be maintained to an optimal state.
The twenty-five aspect of the present invention, in the data communication apparatus of the first to twenty-four aspect, the apparatus further comprises memory control means for rewriting the modem control information registered in said storing means, where-in every time when a normal previous-procedure is ex-ecuted to acquire modem control information, said memory control means adds modem control information newly acquired, corrects the modem control informa-tion registered in said storing means so as to be recorded again.
According to the above-mentioned structure, since the parameter is corrected and learned for each com-munication so as to be maintained to be an optimal value, suitable communication having short communica-tion time, high communication speed, and a low error rate can be carried out while using the short previ-ous-procedure.
The twenty-six aspect of the present invention, in the data communication apparatus of the first to twenty-four aspect, suitable modem control informa-tion is calculated based on a plurality of modem con-trol information obtained by repeating execution of a normal previous-procedure a plurality of times, and said calculated control information is registered in said storing means.
According to the above-mentioned structure, since initial registration of modem control information to be registered in storing means can be adjusted and registered, a probability of success of the short previous-procedure can be improved.
Brief Description of Drawings FIG. 1 is a control signal view showing a commu-nication protocol using a V. 34 modem according to prior art;
FIG. 2 is a basic structural block diagram of a facsimile apparatus to which a data communication ap-paratus according to a first embodiment of the pre-sent invention is applied;
FIG. 3 is a structural view showing a function of a digital signal processor of the data communication apparatus according to the first embodiment;
FIG. 4 is an explanatory diagram showing tones of a line probing tone signal of the data communication apparatus according to the first embodiment;
FIG. 5 is a block diagram of a training reception section of the data communication apparatus according to the first embodiment;
FIG. 6 is an explanatory diagram illustrating calculation of an optimal training time of the data communication apparatus according to the first em-bodiment;
FIG. 7 is a flowchart showing a control operation at the time of calling of the data communication ap-paratus according to the first embodiment;
FIG. 8 is a memory structural diagram of a short previous-procedure registration memory of the data communication apparatus according to the first em-bodiment;
FIG. 9 is a flowchart illustrating a control op-eration at the time of answering of the data communi-cation apparatus according to the first embodiment;
FIG. 10 is a flowchart showing a control proce-dure at the time of registering a short previous-procedure of the data communication apparatus accord-ing to the first embodiment;
FIG. 11 is a control signal chart at the time of executing the short previous-procedure of the data communication apparatus according to the first em-bodiment;
FIG. 12 is a flowchart illustrating an update processing of a modem parameter of the data communi-cation apparatus according to the first embodiment when the short previous-procedure is registered;
FIG. 13 is a flowchart illustrating a check proc-essing of a storage parameter of the data communica-tion apparatus according to the first embodiment;
FIG. 14 is a flowchart illustrating a modem parameter registration prohibit processing of the da-to communication apparatus according to the first em-bodiment;
FIG. 15 is a flowchart illustrating processing of a case in which a destination name is changed accord-ing to the data communication apparatus of the first embodiment of the present invention;
FIG. 16 is a flowchart illustrating processing of a case in which a telephone number of an destination is changed according to the data communication appa-ratus of the first embodiment of the present inven-tion;
FIG. 17 is a flowchart illustrating processing of a case in which an ID information of a self-station is changed according to the data communication appa-ratus of the first embodiment of the present inven-tion;
FIG. 18 is a flowchart illustrating an outline of an operation of a recipient's apparatus a flowchart illustrating processing of a case in which a telepho-5 ne number of an destination is changed according to the data communication apparatus of the first embodi-ment of the present invention; and FIG. 19 is a flowchart illustrating a control protocol of a data communication apparatus according 10 to a second embodiment of the present invention.
Best Mode for Carrying Out the Invention (First Embodiment) A data communication apparatus according to a 15 first embodiment of the present invention will be specifically described with reference to the accom panying drawings. FIG. 2 is a basic block diagram of a facsimile apparatus to which the present invention is applied.
20 Referring to FIG. 2, reference character 101 is a scanning section for scanning an original image. A
printing section 102 records and outputs the received image. A control section 103 performs the control of the entire apparatus and carries out control to en-25 code and decode image signals and execute a communi-cation protocol.
A modem 104 implements every modulation and de-modulation in a facsimile communication protocol that is specified in T.30 ANEXF of the ITU-T. The modem 104 comprises a digital signal processor (DSP) 104a for performing modem's signal processing and an analog front end section 104b serving as both A/D
conversion and D/A conversion functions.
A network control unit (NCU) 105 controls dialing and calling to a line 106. An operation section 107 comprises various kinds of key input switches, such as dial keys and a start key, and a display unit for displaying information. Various kinds of operations of the apparatus are performed through this operation section 107.
A memory 108 stores various kinds of information for execution of a short previous-procedure in the case of communicating with a communication destina-tion, which has a short previous-procedure function.
In this embodiment, information like a telephone num-ber and a modem parameter is stored in the memory 108 as shown in FIG. 8 to be described later.
A modem parameter includes a power reduction val-ue indicative of signal power and a time data indica-tive of a training time, and performs various selec-tions, such as carrier frequency selection for selec-tively setting either a high level or a low level, preemphasis filter selection, symbol rate selection for selectively setting five levels of rates that are transmitted for an eye pattern and selection of a training constellation point.
The functional structure of the digital signal processor 104a of the modem 104 is explained with reference to FIG. 3.
A modem control section 201 controls interface with the control section 103 and the modem 104 and various modem functions. The modem control section 201 comprises a plurality of functional sections to be explained below, and these functions are executed by normal software.
A tonal transmission functional section 202 transmits various tonal signals in accordance with communication protocols. A tonal detecting section 203 identifies a tonal signal sent from a communica-tion destination.
A V.21 modem 204 is a modem that is conformity with Recommendation V.21 of the ITU-T (300 bps, full-duplex). An INFO modem 205 is a modem that is con-fortuity with Recommendation V.34 of the ITU-T (600 bps, full-duplex), and which is used in a start pro-cedure in the communication protocol for line probing and a short previous-procedure.
A control channel modem functional section 206 is a modem that is specified by Recommendation V.34 of the ITU-T (1200 bps or 2400 bps, full-duplex), and is used in setting a modem parameter for a primary channel modem and in a communication protocol for a facsimile control signal.
A primary channel modem functional section 207 is a main channel modem, that is specified by Recommen-dation V.34 of the ITU-T (2400 bps to 33.6 kbps, half-duplex), and is used in communicating image data.
A line probing transmission functional section 208 transmits line probing tones, which are specified by Recommendation V.34. The line probing tone are combined signals of 21 kinds of tonal signals of 150 Hz to 3750 Hz as shown in FIG. 4.
A line probing reception functional section 209 receives the line probing tones from a communication destination and carries out a line inspection. More specifically, the line probing reception module func-tional section 209 performs spectrum analysis on the received signals using the fast Fourier transform al-gorithm to select the optimal symbol rate and carrier frequency for the primary channel modem 207 and other modem parameters.
A training transmission functional section 210 transmits training signals for the V.34 modem. A
training reception functional section 211 receives the training signals from a communication destination and learns a filter coefficient of an adaptive equal-izer to compensate line distortion.
Next, the training signal reception functional section 211 will be discussed with reference to the block diagram of FIG. 5.
A demodulator 401 converts a received training signal Sp, which has undergone A/D conversion in the analog front end section 104b, to a complex baseband signal Yb from the passband. An adaptive equalizer 402 compensates line distortion with respect to the baseband signal Yb and outputs a received signal Yr.
A decision circuit 403 determines a decision point Yd and outputs it. The decision point Yd is used to de-termine the amount of shift of a point on an eye pat-tern of a received signal Yr. A subtracter 404 sub-tracts the decision point Yd from the received signal Yr and outputs an error signal Er. Note that Yb, Yr, Yd and Er are complex signals. The error signal Er is supplied to the adaptive equalizer 402. The adap-tive equalizer 402 learns such an internal filter co-efficient as to reduce this error signal Er. The learned internal filter coefficient is used as a re-ception filter coefficient in the primary channel mo-dem 207.
An absolute value unit 405 computes an absolute value with respect to the error signal Er.
An LPF 406 is a low-pass for smoothing the output signal Ea of the absolute value unit 405. The output signal of the LPF 406 is an EQM signal, which repre sents the degree of compensation for the line distor tion of the adaptive equalizer 402. The smaller this EQM signal is, the more sufficiently the line distor-tion is compensated.
An equalization ability analyzing section 407 5 analyzes the ability of the adaptive equalizer 402 to compensate the line distortion from the EQM signal.
The equalization ability analyzing section 407 ob-serves the amount of change in the EQM signal from the beginning of training as shown in FIG. 6, and 10 computes the time, at which the absolute value of the amount of change becomes smaller than a given value, as the optimal training time. Also, the equalization analyzing module 407 also computes the ratio (SN) of the training signal power to noise power as a final 15 value of the EQM signal. The optimal training time is an absolute value from the origin of the point in the eye pattern. The noise power is an error in the point in the eye pattern.
The optimal training time is used as the training 20 time in executing a short previous-procedure. On the other hand, the SN ratio is used in selecting the data transfer rate of the primary channel modem 207.
Note that no computation of the optimal training time is executed when a short previous-procedure is car-25 tied out.
The operation of the above-structured data commu-nication apparatus will be discussed below.

First of all, the operation of a caller modem for carrying out transmission will be discussed. FIG. 7 is a flowchart illustrating a control operation of a facsimile apparatus according to this embodiment at the time of calling.
In step (hereinafter referred to as ST) 601, calling is initiated in accordance with the telephone number of a transmission destination and a transmis-sion start instruction from the operation section 107.
Then, the memory 108 is searched to check if the telephone number of the transmission destination is registered for a short previous-procedure. When reg-istration is not made, the flow proceeds to step S602 to make dialing.
In ST603, facsimile communication is carried out in a normal communication protocol based on T.30 AN-EXF of the ITU-T.
In ST604, if it is confirmed whether or not the facsimile apparatus on the answering side has a short previous-procedure function. This confirmation is carried out by detecting a flag denoting that commu-nication by short previous-procedure is possible in a field for a non-standard procedure signal NSF includ-ed in a facsimile control signal.
Then, if it is confirmed that the facsimile ap-paratus on the answer side has a short previous-procedure function in step 5604, normal communication is performed on the calling side, and registration for various kinds of parameters necessary for execut-ing the short previous-procedure is executed. The contents to be registered in the short previous-procedure includes, for example, selection informa-tion such as power reduction value and a carrier, and selection information such as optimal training time and non-linear distortion compensation. The contents to be registered for a short previous-procedure are stored in the memory 108 in accordance with the memo-ry structure of the short previous-procedure regis-tration memory illustrated in FIG. 8.
Note that communication in a normal communication protocol is carried out in ST606 when no flag showing that communication by the short previous-procedure is possible is detected in ST604.
Also, in ST607 to ST608, a dial call is made and a communication by short previous-procedure is car-ried out in a case where the short previous-procedure is registered in ST601. In the short previous-procedure, a modem parameter in the short previous-procedure registration memory 108 is sent to the transmission destination in the start procedure to execute the transmission operation according to the modem parameter. This eliminates the need for nego-tiation with the receiver, so that communication time can be reduced.

In ST609, the presence or absence of a communica-tion error is determined. If there is no communica-tion error, the flow proceeds to ST610. In ST610, the rate of data errors in communication is deter-mined, and when there are not many data errors, the process will be terminated. This error rate decision may be made based on the number of resends in, for example, ECM.
If it is determined that there is a communication error in ST611 and that there are many data errors in ST610, the contents of the short previous-procedure registered for the transmission destination are erased from the memory 108, after which the process will be terminated.
The reason why a communication control protocol is executed in accordance with various communication parameters, which have been prestored in association with destination telephone numbers in the above man-ner, is based on the following consideration.
Generally, facsimile apparatuses are often con-nected one to a single line. As communication is of-ten carried out in the same mode with respect to the same communication destination, therefore, a control protocol for exchanging the data communication mode need not be executed every time communication is car-ried out if the previous communication mode is stored in a transmitting apparatus and a receiving apparatus.

Because the quality of a telephone line has been improved due to the recent widespread of digital ex-changes, therefore, there becomes no difference in the line characteristic, which originates from a dif-ference in connection paths. As a result, similar line characteristic and communication quality are al-ways provided for the same communication destination.
If previous modem parameters are stored, it is unne-cessary to conduct a communication protocol associat-ed with line probing for each communication.
Further, the training time, which is set in ac-cordance with the learning time for the filter coef-ficient of the adaptive equalizer of a receiving ap-paratus, is generally set to the length that can be adapted for every line. When communication is imple-mented over a line with a high communication quality, the learning time for the filter coefficient can be shorter than the normally set one, so that the train-ing time may be wasted. In view of the above, reduc-tion in the execution time of a previous-procedure is realized by carrying out the previous-procedure using a prestored communication parameter.
Next, the operation of the receiver of an answer modem will be explained. FIG. 9 presents a flowchart illustrating a control operation for a previous-procedure at the time a facsimile apparatus according to this embodiment receives an incoming signal.

In ST 801, after receiving a reception command sent over the line 106, a deformed answer tone ANSam is transmitted.
In ST 802, it is detected whether to receive a 5 quick tonal signal (QTS) indicating a short previous-procedure or a call menu signal CM from the caller modem, while sending the ANSam signal.
In ST 803 and ST 804, communication is executed by a short previous-procedure using a registered com-10 munication parameter when the QTS signal is detected, while communication is executed by a normal previous-procedure according to the T.30 ANEXF of the ITU-T
when the CM signal is detected. When the receiver is equipped with a function to conduct a short previous-15 procedure, a short previous-procedure registration flag indicating that the self-apparatus has the short previous-procedure function and the optimal training time are described in the non-standard protocol sig-nal NSF field of the facsimile control signal when 20 communication is carried in the normal protocol. The transmitter registers a short previous-procedure for this receiver based on the information in the NSF
field.
Next, the flow of processing for executing the 25 short previous-procedure registration in the appara-tus on the calling side will be explained along the flowchart shown in FIG. 10. The previous-procedure to register the short previous-procedure is carried out in accordance with a normal communication proto-col according to Recommendation V.34 already ex-plained.
In ST901 to 902, the transmitter carries out dial calling and CNG transmission, and waits for incoming a deformed answer tone ANSam to be transmitted from the receiver.
In ST903 to ST905, a control protocol is executed in a conventional G3 protocol (300 bps) when the de-formed answer tone ANSam is not detected in ST902.
On the other hand, when the deformed answer tone ANS-am is detected in ST902, it is further determined whether or not a modem parameter corresponding to the receiver destination is registered in the memory 108.
When the modem parameter corresponding to the re-ceiver destination is not registered therein in ST904, the short previous-procedure of V.34 is executed.
This short previous-procedure will be described later.
In ST906 to ST909, the communication procedure 19a for selecting a modulation mode, the communica-tion procedure 19b for line, the communication proce-dure 19c for modem training, and the communication procedure 19d for setting a modem parameter are ex-ecuted to perform control channel reception, after which the facsimile control procedure is executed.
In ST910, in the facsimile control procedure, it is determined whether or not there is a flag, which shows that the receiver is equipped with a function to execute a short previous-procedure in the NSF
(nonstandard protocol) field transmitted from the re-ceiver. Although various kinds of nonstandard func-tions relating to the execution of V.34 communication protocol can be set in the NSF field, this is not re-lated to the present invention and the explanation will be omitted.
When the receiver is equipped with a function to execute a short previous-procedure in ST911 to ST914, it is confirmed whether or not the calling is origi-nated by the memory key operation. In the case of YES, it is confirmed whether or not a modem parameter can be registered, after which various kinds of modem parameters in ST906 to ST909 are registered in asso-ciation with the destination of the memory key and shifts to V.34 communication protocol. If registra-tion processing for modem parameters is prohibited in ST912, storage processing for various kinds of modem parameters is not executed in ST913.
Moreover, after communication is executed in a communication protocol of any one of ST903, ST905, ST915, a storage parameter of storing means is check-ed in ST915. In other words, if there is a high er-ror possibility that a short previous-procedure will not succeed within guard time, the modem parameter of the memory 108 is erased, and the update for storage parameter is carried out as required. The check for storage parameter and the update therefor will be de-scribed later.
When the receiver is not equipped with a func-tion to execute a short previous-procedure in NSF, the protocol shifts to V.34 communication protocol directly. Even when the calling is not generated by the memory key operation, the protocol shifts to V.34 communication protocol. The reason is that an area for a modem parameter registration is preset in the memory in the case of the dial calling due to the memory key and no parameter storing area is provided in the case of the dial calling due to the normal 10-button keypad operation.
Thus, the communication protocol at the registra-tion of a short previous-procedure is carried out in the normal protocol as recommended by the T.30 ANEXF
of the ITU-T, various kinds of modem parameters are registered in the memory 108 of the caller modem, so that communication can be implemented using the reg-istered parameter from the next time.
A communication protocol in the case of carrying out the above short previous-procedure will now be discussed specifically.
FIG. 11 is a control signal chart for a communi-cation protocol at the time of executing a short pre-vious-procedure, and illustrates a communication process from the establishment of a line connection up to communication of image data. After a line con-nection is established, a communication procedure l0a for initiating a short previous-procedure is per-formed, after which a communication procedure lOb for modem training is executed in accordance with regis-tered time, and a communication procedure lOc for setting a modem parameter, a communication procedure lOd for a facsimile control signal and a data commu-nication procedure l0e for sending data (image data) will be carried out.
First of all, the communication procedure l0a for initiating a short previous-procedure will be ex-plained. A caller modem sends a caller number iden-tification signal CNG, and an answer modem sends a deformed answer tone ANSam. After detecting this de-formed answer tone ANSam, the caller modem sends a quick tonal signal QTS, and sends tones B and QINFO
upon detection of a response signal tone A from the answer modem. After detecting the quick tonal signal QTS from the caller modem, the answer modem sends the tone A and receives the QINFO from the caller modem.
This quick tonal signal QTS indicates a signal to command shift to the short previous-procedure. The quick tonal signal QTS is a repeated pattern of "001100110011...". The reason why such a tonal sig-nal pattern is used is to permit the receiver to clearly distinguish the received the quick tonal sig-nal QTS from a signal pattern of the flag sequence ("011110") and the tonal signal pattern of the call 5 menu signal CM (2-bit start bits "10," 8-bit data and stop bit of "1"), which are defined by Recommendation T.30 of the ITU-T. Moreover, as the quick tonal sig-nal QTS has the same modulation system as the call menu signal CM, the receiver modem can easily dis-10 criminate whether the communication is to be imple-mented in a short previous-procedure or a normal pre-vious-procedure, depending on whether the incoming tonal signal is the quick tonal signal QTS or the call menu signal CM.
15 As explained in FIG. 7, in the QINFO sequence, communication is carried out with V.21 modem 204 (300 bps, full-duplex) in accordance with the contents registered in the short previous-procedure registra-tion memory for each communication destination's 20 telephone number, i.e., in accordance with the train-ing parameter (INFOOh) at a short previous-procedure registration time, the optimal training time and the selected contents for non-linear distortion compensa-tion. The use of the above QINFO sequence can delete 25 signals CM, JM, CJ of communication procedure l0a and the line probing procedure 19b shown in FIG. 1, which are needed in the normal previous-procedure. Also, modem training time can be shortened. As a result, time required for previous-procedure can be shortened by amount of time corresponding to the above deletion and the reduction in the modem training time.
In the next communication procedure lOc for modem training, training the calling side apparatus and the answering side apparatus is performed in accordance with the training parameter (INFOOh) of the QINFO se-quence and the optimal training time. Since the op-timal training time is necessary minimum time regis-tered in advance, this results in time reduction in previous-procedure.
In the communication procedure lOd for setting a modem parameter, the MPH for the answer modem is set based on the QINFO-based selection of non-linear dis-tortion compensation and information on the SN ratio computed in the communication procedure lOc for modem training. Therefore, this sequence can also shorten time.
The facsimile control procedure l0e and the data communication procedure lOf are the same as the nor-mal V.34 communication protocol.
The communication protocol in the short previous-procedure is carried out in such a manner that the communication procedure for starting the short previ-ous-procedure is executed in an exclusive procedure and the communication procedure for modem training and the subsequent communication procedures are basi-cally performed in accordance with the recommendation for T.30 ANEXF of the ITU-T, thereby realizing the reduction in the entire communication time.
In the normal case, the aforementioned short pre-vious-procedure is registered and executed, thereby realizing the reduction in communication time.
However, in the above-explained short previous procedure, if various kinds of modem parameters are once registered to a specif is destination, the commu nication by the short previous-procedure mode is al-ways executed in the subsequent communication. For this reason, if a registered modulation mode of the destination's receiver is changed and the line char-acteristic is changed, the sequence for executing the updating is omitted. This causes a problem in which the set value of the modem parameter cannot be updat-ed in accordance with the changed modulation mode and line characteristic. More specifically, the modula-tion mode and the line characteristic vary in the following cases, and there often occurs a case in which a normal short previous-procedure cannot be ex-ecuted with the registered modem parameter.
The communication apparatus on the receiver side, which is equipped with the short previous-procedure, is replaced with another apparatus, which is not equipped with the short previous-procedure.

The registered destination is a representative telephone, and the kind of destination's apparatus is changed every time when connection is made.
The communication time zone and an LCR function exert an influence upon the change in the communica-tion path.
Transoceanic communication is carried out via submarine cable or satellite.
The present invention has been structured such that requirement on the registration of the modem parameter for a short previous-procedure and the up-date on the registration are dynamically changeable in accordance with such circumstances. Thereby, a problem in which success of a short previous-procedure is not attained or a bit rate is reduced can be avoided to the greatest extent practicable.
Next, an update processing for a modem parameter, which has been once registered in a short previous-procedure, will be explained along the flowchart shown in FIG. 12. FIG. 12 is a flowchart explaining the processing when the transmitter fails in the re-covery by the modem and a shift to a short previous-procedure cannot be made.
In ST1101 to ST1102, the transmitter carries out dial calling and CNG transmission, and waits for in-coming a deformed answer tone ANSam to be transmitted from the receiver. When the deformed answer tone ANSam is not detected, this means that the receiver does not support V.34 communication protocol, and the protocol shifts to the conventional G3 protocol.
In ST1103 to ST1104, it is checked whether or not a modem parameter is registered in the memory 108.
When the modem parameter is not registered therein, the protocol is shift to a normal V.34 communication protocol.
In ST1105 to ST1108, a guard timer starts count-ing for 15 seconds, after which the transmitter ex-ecutes a short previous-procedure. In other words, a quick tonal signal QTS is transmitted and a communi-cation procedure l0a for initiating a short previous-procedure is executed. Thereafter, a communication procedure lOc for modem training is executed. At this time, it is detected whether or not the short previous-procedure proceeds to a control channel, that is, a communication procedure lOd for setting a modem parameter.
When the short previous-procedure proceeds to the control channel and the setting of the modem parame-ter is completed before a time-out of the guard timer, the communication procedure proceeds to a communica-tion procedure l0e for a facsimile control, and V.34 communication protocol is executed. The control channel described here is the sequences lOd and l0e shown in FIG. 11.

In ST1109, when the time-out of the guard timer occurs, the apparatus on the transmitter side is in a signal reception waiting mode of 300 bps, that is, T.

30 NSF/CSI/DIS reception standby state. The time-out 5 occurs when a state in which there is no response of a PPh signal from the apparatus on the receiver side is continued and passed for 15 seconds even though the modem proceeds the procedure from the transmis-sion of the QINFO signal to that of the PPh signal 10 and executes recovery processing.
In ST1111 to ST1113, check processing for the parameter registered in the memory 108 is executed, after which the received NSF or DIS is inspected so as to conform whether or not the apparatus on the re-15 ceiver side supports V.8 communication protocol.
When the apparatus on the receiver side does not sup-port V.8 communication protocol, the procedure is shift to a conventional G3 protocol.
Although the above check processing for the 20 parameter in ST1111 will be described later, the mo-dem parameter of the memory 108 is erased and its up-date is carried out as required as described later when the short previous-procedure does not succeed within guard time.
25 Thus, when the short previous-procedure does not normally proceed within 15 seconds, a shift to the signal waiting mode of 300 bps is carried out. The reason will be explained as follows:
Specifically, when the apparatus on the receiver side is not equipped with the short previous-procedure function, there is a high possibility that NSF signal of 300 bps, DIS signal, etc. will be transmitted. For this reason, the apparatus receives these signals, and executes the G3 communication pro-tocol, thereby continuing communication. This proc-essing can avoid the worst case in which a communica-tion error occurs.
Moreover, the reason why the guard time is set to seconds will be explained as follows:
Specifically, in T.30 protocol, it is defined that the transmission of NSF/CSI/DIS is repeated for 15 35 seconds, and the interval among NSF/CSI/DIS is 3 seconds. Although the length of NSF/CSI/DIS differs, depending on the length of NSF, the length is normal-ly tens of octets and is within the range of 3 to 5 seconds. If a shift to T.30 protocol is carried out after a lapse of 15 seconds from the start of commu-nication, the apparatus on the transmitter side can receive NSF/CSI/DIS signals a plurality of times. In a case of the f allure in the short previous-procedure, NSF/CSI/DIS signals must be received at least twice to receive these signals without fail. For this rea-son, the guard time, which is required for the above reception, is reserved and determined. This can surely avoid the worst case in which the short previ-ous-procedure ends in failure and the shift to T. 30 protocol cannot be carried out.
In view of avoiding the communication error, it is possible to use a method in which a number of times of retrying a short previous-procedure and a number of times of transmitting a specific signal are counted in place of guard time.
In ST1114, a shift to processing B is carried out to execute normal V.34 protocol when it is deter mined that the apparatus on the receiver side sup ports V.8 communication protocol in ST1112.
Processing B is one that executes V.34 protocol and short previous-procedure registration processing at the same time. The shift to processing B makes it possible to acquire the modem parameter again and to improve reduction in communication time by execution of communication in a short previous-procedure in the subsequent communication even if the short previous-procedure does not normally proceed.
In ST1111, the modem parameter of memory 108 was erased when the modem f ailed in the recovery and the time-out of guard time occurred. The reason can be explained as follows:
Specifically, if the contents of memory 108 re-mains cleared, a short previous-procedure is not ex-ecuted in a next communication and a normal previous-procedure is carried out. If an error in executing the short previous-procedure this time lies in the other reason and not the reason that the receiver does not support the short previous-procedure, no short previous-procedure can be preferably executed in the subsequent communication.
According to the present invention, processing B, that is registration processing for a short previous-procedure shown in FIG. 10 is repeated. Thereby, V.34 normal protocol is executed with respect to the receiver, and short previous-procedure registration processing for registering a modem parameter is car-ried out.
In the above series of processing, when an error is occurred at a normal V.34 protocol execution time, the procedure is shifted to T.30 protocol so as to continue the communication. While, when an error is occurred at a short previous-procedure execution time, V.34 protocol is retried to update the modem parame-ter. In this case, the execution of the short previ-ous-procedure shows that communication has been actu-ally performed in a short previous-procedure previ-ously though the error is generated. Therefore, there is a high possibility that the short previous-procedure will be normally executable again by the update of the modem parameter. For the above reason, try processing is carried out at the short previous-procedure execution time as mentioned above.
Next, check processing for a storaged parameter in ST1111 will be explained along the flowchart shown by FIG . 13 . When an error is occurred in communica-tion at a short previous-procedure execution time or a normal previous-procedure execution time, this se-quence erases the modem parameter registered in ac-cordance with the circumstances and stops the modem parameter registration processing at the time when an error rate reaches a fixed value or more. This is based on the consideration in which it is no use of repeating the registration of the modem parameter when communication cannot be normally made even if the registration of modem parameter is tried a fixed number of times. Processing for trying a short pre-vious-procedure registration is repeated up to the set number of times.
In ST1201 to ST1202, the short previous procedure is once registered, after which a short previous-procedure execution counter is incremented every time V.34 protocol is executed.
In ST1203 to ST1207, when the short previous-procedure is normally ended, the modem parameter stored in the memory 108 is erased. The erase of the modem parameter is specifically carried out in the following cases:
First, the erase of the modem parameter is car-ried out when the modem fails in the recovery. That is a case in which ANSam is detected and the quick tonal signal QTS is sent from the apparatus on the transmitter side but the signal does not reach the 5 control channel. This is because communication time at no short previous-procedure execution becomes shorter when an error is generated again at a next short previous-procedure execution time.
Second, the erase of the modem parameter is car 10 ried out when an error is generated in the establish ment of control channel. That is a case in which the communication previous-procedure is completed but an image information channel connection ends in failure and a trouble, which is caused at a control signal 15 exchanging time between pages such as MPS after the image information channel. There is a high possibil-ity that both cases will be ascribable to the fact that the modem parameter is not appropriately set.
Third, the erase of the modem parameter is car 20 ried out when a transmission error often occurs dur ing communication so that a bit rate is considerably reduced. For example, there is a case in which a line condition is extremely good at a modem parameter setting time but poor in an actual communication.
25 Particularly, since transoceanic communication is carried out via submarine cable or satellite, a qual-ity of line often differs between a modem parameter registration time and an actual communication time.
In such a case, communication speed in a state that the set modem parameter is not used seems to be im-proved. The determination of the reduction in bit rate may be performed by detecting an error rate in communication and sequentially comparing the detected error with an error rate prestored at a communication start time.
Fourth, the erase of the modem parameter is car ried out when the transmission bit rate is lower than a reference value. In this case, 14.4 kbps of V.17 communication protocol is used as a reference value, and the registered modem parameter is erased when the bit rate is less than the reference value. This is because the communication speed in V.17 protocol is faster than the communication speed in V.34 protocol in accordance with the registered modem parameter.
In any process of communication started in the short previous-procedure and any process of communi cation at a normal V.34 protocol execution time, the memory 108 is erased and the modem parameter is not registered when the aforementioned communication troubles exist.
In ST1208 to ST1209, it is conf armed whether or not communication is carried out in a short previous procedure. When communication is carried out in the short previous-procedure, a short previous-procedure error counter is incremented. When communication is not carried out in a short previous-procedure, a shift to next procedure is carried out without incre menting the count value . The count value is used in the following processing.
In ST1210 to ST1211, it is checked whether or not the number of execution times of short previous-procedure reaches 10. Then, it is determined whether or not a count value of a short previous-procedure error number counter is a fixed value or more at the time when the counter counts up. This determination may be executed based on whether or not an error rate exceeds a fixed value and not based on the cumulative number of times of error generation. For example, in a case where the error rate is determined every time when the number of execution times of short previous procedure reaches 15, two counters each having a four-bit structure may be prepared. For this reason, this determination can be carried out with a register of one bit.
In ST1212 to ST1214, when the error rate is the fixed value or more in ST1211, the registration of modem parameter is prohibited, and the clear of the short previous-procedure execution counter and that of the short previous-procedure error counter are executed. In this case, the modem parameter regis-tered in storing means is erased such that no short previous-procedure is executed in the subsequent com-munication.
When communication error is occurred in communi cation in which the short previous-procedure is exe cuted, the memory 108 is set to be in a vacant state so as to try register the modem parameter continu-ously in communication including next and after. As a result, when the short previous-procedure error reaches the fixed value or more, a shift to registra-tion processing of a modem parameter for a short pre-vious-procedure is prohibited such that no short pre-vious-procedure can be executed. While, when the ex-ecution of short previous-procedure ends in failure, the above is unfavorable since it takes more time than normal communication.
Next, a modification of the above registration prohibition function for a modem parameter will be explained along a flowchart shown in FIG. 14. In the flowchart of FIG. 13, the error rate is computed at the time when the number of execution times of short previous-procedure reaches 10. While, in the flow-chart of FIG. 14, when the number of error times reaches a fixed value or more, the registration func-tion for a modem parameter is stopped even if the number of execution times of short previous-procedure is before 10. Since the first half of processing of FIG. 14 is the same as that of processing of FIG. 13, the explanation will be omitted.
In ST1301 to ST1302 of FIG. 14, when the short previous-procedure error counter exceeds the fixed value or more, the registration function for a modem parameter is stopped.
In ST1303 to ST1305, when the short previous procedure execution counter reaches 10, the clear of the short previous-procedure execution counter and that of the short previous-procedure error counter are executed.
In other words, by the aforementioned processing, for example, in a case where the number of error times is four or more, this surely exceeds a prede-termined error rate at the time when the counter counts up. Since the modem parameter is not regis-tered even before the short previous-procedure execu-tion counter reaches 10, it is possible to avoid a case in which a modem parameter with low precision is registered. By this processing, in the subsequent communication, the short previous-procedure is not executed.
Next, the following will explain processing for a case in which a destination address and a telephone number is changed when the destination address and the modem parameter are already registered in a sin-gle button dialing and an abbreviated dialing. FIG.
15 is a flowchart showing processing when there is a change in a name of destination address.
In ST1401 to ST1403, a dial input is carried out and a name of destination is input, after which it is determined whether or not the modem parameter stored 5 in the memory 108 is erased.
In ST1404 to ST1407, the stored parameter is erased when the determination result in ST1403 is YES.
Next, if the parameter registration to the memory 108 is prohibited, the prohibition is cancelled. Then, 10 the clear of the short previous-procedure execution counter and that of the short previous-procedure er-ror counter are sequentially executed.
On the other hand, when it is determined that the storaged parameter is not erased in ST1403, the 15 contents registered in the memory 108 are stored as they are. This prevents all of the contents of the memory including the registered modem parameter from being erased when the change of the name is simply registered. Therefore, since it is unnecessary to 20 newly execute processing for a short previous-procedure registration at a next communication time, communication can be carried out without extra commu-nication time.
FIG. 16 is a flowchart showing processing for a 25 case in which a destination's telephone number is changed.
In ST1501 to ST1502, a telephone number is input and it is determined whether or not there is a change in the telephone number.
In ST1503 to ST1506, if there is the change in the input telephone number, the storaged parameter is automatically erased. If the parameter registration to the memory 108 is prohibited, the prohibition is cancelled. Then, the clear of the short previous-procedure execution counter and that of the short previous-procedure error counter are executed. The change of the telephone number seems to occur in a case where the apparatus on the receiver side is changed or a case where a line is changed. Therefore, the reason why the prohibition is cancelled is to provide the destination where the execution of the short previous-procedure is once prohibited the op-portunity to perform communication in a short previ-ous-procedure again and to shorten communication time.
While, if there is no change in the telephone number in ST1502, the contents registered in the mem ory 108 are stored as they are, the destination is input in such a state, and processing is ended. In this case, similar to processing of the flowchart of FIG. 15, since it is unnecessary to newly execute processing for a short previous-procedure registra-tion at a next communication time, communication can be carried out without extra communication time.
In processing shown in FIG. 15 and processing shown in FIG. 16, a selective operation is performed.
This carries out the erase of the contents of the memory including the parameter automatically when there is the change in the telephone number input by an operator. On the other hand, when there is no change in the telephone number, the operator is urged to input the destination, after which a standby sta-tus whether or not the storage parameter is erased is set.
In this case, the change of the telephone number seems to occur in a case where the apparatus on the receiver side is moved or a case where a line is changed. Therefore, the reason why the contents of the memory including the parameter is automatically carried out when there is a change in the telephone number is the need for updating the modem parameter in a next communication.
On the other hand, when there is no change in the telephone number, there is included a case in which a name of destination's organization is simply changed. For this reason, a method in which either case is manually selected is left.
Next, the following will explain an operation for a storaged parameter of the memory 108 when there is a change in ID information of a self-station with reference to FIG. 17. Processing of FIGS. 15 and 16 is one, which is related to how the storage parameter registered is processed when there is a change in the apparatus on the destination side where one-touch key etc., is registered. In contrast, processing of FIG.
17 is described on the assumption that there would be a change in a telephone number of the self-apparatus.
In many cases, the change in the telephone num-ber of the self-apparatus involves a change in a line to be connected. More specifically, the line is of-ten changed from an analog line to an ISDN. It can be considered that this case carries a change in line characteristics in most cases. In order to deal with such a case, the following processing is carried out.
In ST1601 to ST1603, a character ID and a nu meric ID are continuously input, and it is determined whether or not the input numeric ID is changed.
In ST1604 to ST1607, when the input numeric ID
is changed, the storage parameter of all destinations key registered is erased. Then, if the parameter registration to the memory 108 is prohibited, the prohibition is cancelled. Further, the clear of the short previous-procedure execution counter and that of the short previous-procedure error counter are carried out.
Thereby, the parameter of the memory 108 is cleared, but the destination already registered is unchanged. For this reason, update processing for a modem parameter is sequentially executed for each destination in the subsequent communication.
In the aforementioned processing, the memory clear is automatically executed. However, there is a case in which a manual execution of the memory clear is needed. For example, a terminal such as a termi-nal adapter is newly connected between data communi-cation and a line, or the connected terminal is changed. In such a case, there is no change in the telephone number, but the line characteristic is changed. For this reason, it is needed that the mo-dem parameters of all destinations be cleared and up-dated.
Moreover, if a continuous error occurs with re spect to a plurality of destinations in the short previous-procedure, there is a high possibility that the line to which the self-apparatus will be changed from the analog line to ISDN. For this reason, in such a case, only the registered destination can be maintained as it is, and control information corre-sponding to all destinations such as registered modem parameters can be all erased and updated and regis-tered. This makes it possible to avoid a disadvan-tage in which the waste short previous-procedure is repeated.
The above explained the apparatus on the trans-mitter side.
Next, an outline of an operation of the appara-tus on the receiver side will be explained along the flowchart of FIG. 18.
In ST1701 to ST1702, the apparatus transmits a deformed answer signal ANSam to a caller number iden-5 tification signal CNG incoming from the apparatus on the transmitter side, and detects a quick tonal (QTS) signal sent from the apparatus on the transmitter side.
In ST1703 to ST1704, when a call menu signal CM
10 is detected without detecting QTS in ST1702, normal V.34 communication protocol is carried out.
In ST1705 to ST1706, when QTS signal is received in ST1702, the guard timer starts counting for 15 seconds and instructs the self-modem to execute the 15 short previous-procedure.
In ST1707 to ST1708, it is confirmed whether or not the communication by previous-procedure reaches the establishment of a control channel through a mo-dem training sequence, after which the control chan-20 nel sequence is executed.
In ST1709 to ST1710, the counting up of the guard timer is detected, and when the guard timer counts up, communication is carried out in G3 proto-col of 300 bps. When no CM signal is detected in 25 ST1703, that is, the transmitter does not support on-ly V.17 protocol or less, communication is similarly carried out in G3 protocol.

Thus, the reason why guard time for 15 seconds is provided even in the apparatus on the receiver side is to adapt to processing for the apparatus on the transmitter side. Namely, in the apparatus on the transmitter side, when the communication by pre-vious-procedure does not reach the control channel during 15 seconds, a mode is changed to one that re-ceives NSF/CSI/DIS of 300 bps to proceed G3 protocol.
For this reason, there is no meaning in standby time for more than 15 seconds, and the apparatus on the receiver side moves to G3 protocol.
In the aforementioned first embodiment, after a lapse of a predetermined period of time from the reg-istration of control information to storing means, control information can be deleted from storing means so as to execute an update of control information by parameter registering means. This makes it possible to maintain modem control information registered in storing means in an optimal state. In this case, the update period can be counted from registration time of each destination or all destinations registered may be updated at the same time by a fixed timer.
Moreover, the first embodiment explained that the registration of control information to storing means was carried out in one normal communication.
However, memory control means for rewriting the modem control information registered in storing means may be provided. Ever time when normal communication pre-protocol is executed to acquire modem control in-formation, modem control information newly acquired may be added, the modem control information regis-tered in storing means may be corrected and recorded again by memory control means.
Furthermore, in consideration of the history of a plurality of times of communication, an average value of parameters obtained in the plurality of times of communication is calculated and suitable control information is registered instead of the point that registration of control information to storing means is performed one time. This further improves a probability of success of the short previ ous-procedure.
Moreover, since the correcting and learning of the parameter are carried out for each communication, the modem parameter can be maintained to have an op-timal value. As a result, suitable communication having short communication time, high communication speed, and a low error rate can be carried out while using the short previous-procedure. As a rule for a parameter correction, for example, there is a method in which the main parameter of each of registered control information and new control information is plotted in a multi-dimensional space and the center of gravity of each parameter is searched so as to ob-tain its middle point. In this case, it is better to assign weights to data to be appropriately used, de-pending on the number of execution times of the past short previous-procedure. Further, to improve cor-rection accuracy, the parameter to be used as correc-tion data may be limited to be within a fixed range.
(Second embodiment) A data communication apparatus according to a second embodiment of the invention will be described with reference to a flowchart illustrated in FIG. 19.
While registration of a short previous-procedure is conducted in association with a destination's telephone number at the time of dialing on the appa-ratus on the transmitter side, the second embodiment uses a caller telephone number informing service by an exchange, which has recently started, to register a modem parameter on the apparatus on the receiver side in association with the caller telephone number.
Referring to FIG. 19, in ST1801 to ST1803, when a receiver side is informed of a telephone number from the transmitter side through the caller telephone number informing service, the receiver side searches telephone numbers registered in the memory in a sin-gle button dialing and an abbreviated dialing to check whether or not there is there is a correspond-ing telephone number.
In ST1804 to ST1806, short previous-procedure communication is carried out when there is the corre-sponding telephone number, and normal protocol commu-nication carried out when there is no corresponding telephone number.
In the embodiment, either the transmitting appa-ratus or the receiving apparatus registers informa-tion such as the modem parameter, the optimal train-ing time and the modulation mode in the memory. But, the transmitting apparatus and the receiving appara-tus may both register those information in the memo-ries. This allows the transmitting apparatus and the receiving apparatus to skip the communication proto-col 19a of FIG. 19 and start from the communication protocol 19b upon reception of an incoming signal.
In this case, the time for the pre-communication pro-tocol is further shortened because such information need not be exchanged in the communication protocol.
According to this invention, as discussed above, a modem parameter and optimal training time for a mo-dem are stored in association with a destination's telephone number, so that in the subsequent communi-cation, the communication pre-protocol can be per-formed in accordance with the stored modem parameter and optimal training time. It is therefore possible to largely shorten the time for the pre-communication protocol.
Moreover, when a communication error rate high or there is a change in line characteristics, an update of a parameter can be suitably executed and an execu-tion of a short previous-procedure can be prohibited, so that the short previous-procedure can be executed 5 in an appropriate state while avoiding a case in which communication time increases due to the presence of short previous-procedure functions.

Claims

1. A data communication apparatus comprising:
storing means for storing various kinds of modem control information each destination in association with an operation key;
calling means for calling a call to said destination by a transmission command from said operation key to start communication; and communication control means for transmitting a shift notify signal that indicates shift to a short previous-procedure in a case of communication using said calling means, thereafter controlling the modem based on said various kinds of control information so as to shorten a previous-procedure and carry out data transmission.

2. The data communication apparatus according to claim 1, wherein said communication control means transmits the shift notify signal in place of a calling menu signal, response to a deformed answer signal with respect to a calling signal conformed to Recommendation ITU/V.34, said deformed answer signal incoming from a receiver side.

3. The data communication apparatus according to claim 1, wherein said communication control means checks whether or not the various kinds of the modem control information are stored in said storing means before shifting to the short previous-procedure, and executes the short previous-procedure only when said control information is stored.

4. The data communication apparatus according to claim 1, further comprising parameter registering means for storing various kinds of modem control information obtained in the previous-procedure in communication with the destination, in a state that said storing means is stored only destination information corresponding to said operation key.

5. The data communication apparatus according to claim 4, wherein said parameter registering means executes no registration of control information for the short previous-procedure when an error is detected in a normal procedure.

6. The data communication apparatus according to claim 5, wherein said parameter registering means registers a control information obtained in the normal previous-procedure in said storing means, and erases the control information, thereby control information is not registered.

7. The data communication apparatus according to claim 1, wherein when the short previous-procedure does not proceed, said communication control means shift to the normal previous-procedure or second communication procedure having low communication speed so as to continue communication after a predetermined time.

8. The data communication apparatus according to claim 7, wherein said second communication procedure is a communication protocol according to Recommendation ITU/T.30, and said predetermined time is time for which NSF/CSI/DIS signals of T.30 can be received twice or more after shifting to the second communication procedure.

9. The data communication apparatus according to claim 1, wherein when the short previous-procedure does not proceed, said communication control means performs shifts the procedure from the short previous-procedure to the second communication procedure having low communication speed so as to continue communication after the number of retrial times of said short previous-procedure reaches a fixed value.

10. The data communication apparatus according to claim 1, further comprising error detecting means for detecting an error of communication, wherein when said error detecting means detects an error after starting execution of the short previous-procedure, said communication control means maintains destination information in said storing means on one hand and erases only the corresponding various kinds of modem control information on the other hand.

11. The data communication apparatus according to claim 7, further comprising parameter registering means for executing communication in a normal previous-procedure in the same call so as to newly store various kinds of the modem control information obtained in said normal previous-procedure in said storing means when the short previous-procedure doesnot proceed.

12. The data communication apparatus according to claim 10, wherein said error detecting means determines abnormality of communication when a data transmission error rate of communication increases to a predetermined value or more, after executing the short previous-procedure or the normal previous-procedure.

13. The data communication apparatus according to claim 10, wherein said error detecting means determines abnormality of communication when a data transmission error rate of communication is lower than a data transmission error rate of a communication protocol whose speed is slower than communication speed, after executing the short previous-procedure or the normal previous-procedure.

14. The data communication apparatus according to claim 12, further comprising parameter registering means for storing various kinds of the modem control information obtained in a next normal previous-procedure executed with respect to the destination in said storing means after erasing the control information from said storing means.

15. The data communication apparatus according to claim 1, when error generated time of the short previous-procedure or an error rate based on executed time of the short previous-procedure regarding to the same destination exceeds a predetermined value, the short previous-procedure is prohibited from being executed, in next communication to the same destination.

16. The data communication apparatus according to claim 15, further comprising an error counter for counting a number of error generations of short previous-procedure, wherein said error counter counts up every time when various kinds of control information in said storing means are erased.

17. The data communication apparatus according to claim 16, wherein said error counter determines whether or not the communication is started in the short previous-procedure before counting up, and said error counter don't count up when a result of said determination is no.

18. The data communication apparatus according to claim 15, wherein said communication control means checks whether or not various kinds of the modem control information are registrable in said storing means before the shift to the short previous-procedure, and executes no short previous-procedure when various kinds of the modem control information are non-registrable.

19. The data communication apparatus according to claim 18, further comprising parameter registering means for storing various kinds of the modem control information obtained in the normal previous-procedure, wherein the short previous-procedure is prohibited by prohibiting said various kinds of the modem control information from storing in said storing means.

20. The data communication apparatus according to claim 1, further comprising operating means for changing a destination's name or a destination's telephone number stored in said storing means; and memory controlling means for automatically erasing all information of a relevant information store area including modem control information stored in association with said destination's telephone number when said destination's telephone number is changed by said operating means.

21. The data communication apparatus according to claim 1, further comprising operating means for inputting a unique identification code of said data communication apparatus; and memory controlling means for automatically erasing all information of a relevant information store area including modem control information stored in association with all telephone numbers when said unique identification code is changed by said operating means.

22. The data communication apparatus according to claim 20, further comprising parameter registering means for storing various kinds of the modem control information obtained in a next normal previous-procedure executed with respect to a destination in said storing means in a state that said storing means stores only the destination corresponding to an operation key.

23. The data communication apparatus according to claim 1, further comprising memory control means for automatically erasing all information of a relevant information store area including modem control information stored in association with all telephone numbers when an error continuously occurs in the short previous-procedure executed with respect to a plurality of destinations.

24. The data communication apparatus according to claim 1, wherein said control information is deleted from said storing means after a predetermined time from registration of control information in said storing means so as to execute an update of control information by parameter registering means.

25. The data communication apparatus according to claim 1, further comprising memory control means for rewriting the modem control information in said storing means, wherein every time when a normal previous-procedure is executed to acquire modem control information, said memory control means adds new modem control information, corrects the modem control information in said storing means based on said new modem control information, and records again the corrected modem control information in said storing means.

26. The data communication apparatus according to claim 1, wherein suitable modem control information is calculated based on a plurality of modem control information obtained by a plurality of repetition of a normal previous-procedure, and said calculated control information is registered in said storing means.

27. A data communication method comprising the steps of:
storing various kinds of control information for each destination in association with an operation key;
generating a call to said destination by a transmission command from said operation key to start communication; and transmitting a shift notify signal indicative of shift to a short previous-procedure, thereafter controlling a modem based on said various kinds of control information so as to shorten a communication pre-protocol and carry out data transmission.