JPH09163033A - Data communication method, data communication system, and device on call originating side - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the occurrence of a communication protocol error due to a charging pulse. SOLUTION: In this data communication method, the charging pulse is detected by a charging pulse detection circuit 20 after the start of connection to a public telephone line 30, and a CPU 10 calculates the generation period of the charging pulse, and thereafter, data transmission/reception is stopped just before the generation timing of the charging pulse predicted based on the generation perod and is restarted after the end of generation of the charging pulse.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to data communication using a public telephone line, such as a public telephone, in which a charge is collected when a charging pulse is generated.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 2-90865 discloses an invention for preventing deterioration of image quality of a facsimile image due to charging pulse noise generated during facsimile communication. This is done by analyzing the telephone number of the other party, knowing the charging pulse generation period, and stopping the data transmission at the timing of the charging pulse generation.

[0003]

However, in order to analyze the telephone number (area code) of the other party to know the charging pulse generation period, a table storing the correspondence between the telephone number and the charging pulse generation period is stored. Must be prepared as a database. When the call charge is changed, the billing pulse generation period is changed, so that the above-mentioned database needs to be updated each time.

Further, in a communication protocol other than the facsimile, if the protocol requires a response to the transmission command, it is possible that the transmission command or the response may be lost due to the influence of the charging pulse. In this case, a communication protocol error occurs and normal communication cannot be performed.

The present invention has been made to solve the above-mentioned problems, and it is possible to predict the charging pulse generation timing without a database by measuring the actual charging pulse interval after the start of communication. It is possible to eliminate the occurrence of a communication protocol error due to the charging pulse.

[0006]

Means for Solving the Problems and Effects of the Invention The invention according to claim 1 made in order to achieve the above object, uses a public line in which a charge is collected by the generation of a charging pulse, and data is collected. In a data communication method for performing communication, a charging pulse is detected after the connection to the public line is started, the generation cycle of the charging pulse is calculated, and thereafter, the generation timing of the charging pulse predicted based on the generation cycle is calculated. The data communication method is characterized in that the data transmission / reception is stopped immediately before and the data transmission / reception is restarted after the generation of the charging pulse.

According to this data communication method, the billing pulse is detected after the connection to the public line is started and the billing pulse generation period is calculated. Therefore, as in the conventional case, the telephone number and the billing pulse generation period are different from each other. It is not necessary to prepare a table that stores the correspondence relationship as a database, so
There is no need to update the database each time the call charge changes.

Data transmission / reception is stopped immediately before the charging pulse generation timing predicted based on the generation cycle, and data transmission / reception is restarted after the charging pulse is generated. Therefore, the transmission command or response is affected by the charging pulse. It is possible to eliminate the occurrence of communication protocol error such as missing. Preventing such a communication error also leads to minimizing the extension of the connection time due to the communication retry.

The following are examples of effective data communication systems to which such a data communication method is applied. First, as described in claim 2, the first data communication system uses the public line in which the charge is collected by the generation of the charging pulse, to perform the data communication between the calling side device and the called side device. In the data communication system for performing the above-mentioned operation, the calling side device calculates the generation cycle of the charging pulse based on the charging pulse detecting means for detecting the charging pulse and the charging pulse detected by the charging pulse detecting means. Generation cycle calculation means and transmission / reception control for stopping transmission / reception of data immediately before the generation timing of the charging pulse predicted based on the generation cycle calculated by the generation cycle calculation means, and restarting data transmission / reception after the generation of the charging pulse Means and the transmission / reception control means to suspend the transmission of data, the transmission interruption information is added to the transmission data immediately before the interruption. And a transmission interruption information notifying means for notifying the called equipment, whereas, the called device,
It is characterized by further comprising reception control means for interrupting the reception of data and restarting the reception of the data after a lapse of a predetermined time when the transmission interruption information is notified from the calling side device.

Further, as described in claim 3, the second data communication system uses the public line in which the charge is collected by the generation of the charging pulse, to connect the calling side device and the called side device. In a data communication system for performing data communication between terminals, the calling side device generates a charging pulse based on the charging pulse detecting means for detecting the charging pulse and the charging pulse detected by the charging pulse detecting means. A generation cycle calculating means for calculating a cycle, data transmission / reception is stopped immediately before the charging pulse generation timing predicted based on the generation cycle calculated by the generation cycle calculation means, and data transmission / reception is restarted after the generation of the charging pulse. Transmission / reception control means, and generation cycle notification means for notifying the called side device of the generation cycle calculated by the generation cycle calculation means, On the other hand, the called side device suspends data transmission and reception immediately before the generation timing of the charging pulse predicted based on the generation period notified by the calling side device, and transmits and receives data after the generation of the charging pulse ends. It is characterized by comprising a transmission / reception control means for restarting.

In the first data communication system according to the second aspect, in the calling side device, the generation cycle calculating means calculates the generation cycle of the charging pulse based on the charging pulse detected by the charging pulse detecting means. For example, it may be calculated by measuring the generation intervals of the first and second charging pulses after off-hook. Then, the transmission / reception control means stops the data transmission / reception immediately before the charging pulse generation timing predicted based on the calculated generation period, and restarts the data transmission / reception after the charging pulse generation ends.

When the transmission / reception control means suspends the data transmission, the transmission suspension information notifying means adds the transmission suspension information to the transmission data immediately before the suspension and notifies the called side device. Then, in the called side device notified of the transmission interruption information from the calling side device, the reception control means interrupts the reception of the data, and resumes the reception of the data after a lapse of a predetermined time.

Thus, when data communication is performed between the calling side device and the called side device, it is possible to prevent the adverse effect of the charging pulse regardless of which is transmitting or receiving the data. Further, in the second data communication system according to claim 3, in the calling side device, the generation cycle calculation means calculates the generation cycle of the charging pulse based on the charging pulse detected by the charging pulse detection means. Then, the transmission / reception control means stops the data transmission / reception immediately before the charging pulse generation timing predicted based on the calculated generation period, and restarts the data transmission / reception after the charging pulse generation ends.

Further, the generation cycle notifying means notifies the called side device of the generation cycle calculated by the generation cycle calculating means. Then, the transmission / reception control means of the called side device stops the transmission / reception of data immediately before the generation timing of the charging pulse predicted based on the generation period notified by the calling side device, and transmits / receives the data after the generation of the charging pulse. Is restarted.

Here, the difference between the first data communication system and the second data communication system described above will be clarified. Both the first and second data communication systems,
The same is true in that control is performed such that data transmission / reception is stopped immediately before the charging pulse generation timing predicted based on the calculated generation period, and data transmission / reception is restarted after the charging pulse generation ends.

However, in the first data communication system,
When the calling device interrupts the data transmission (that is, every time it interrupts), it adds the transmission interruption information to the transmission data immediately before the interruption and notifies the called device, so the called device does not When the transmission interruption information is notified, the reception of the data is interrupted and the reception of the data is restarted after the elapse of a predetermined time. That is, the interruption of data reception is executed based on the transmission interruption information from the calling side device, every time the transmission interruption information is received.

On the other hand, in the second data communication system, since the generation cycle calculated by the issuing side device is notified to the called side device, once the notification is received, the called side device is notified of the occurrence period. Data transmission / reception is controlled separately based on the cycle. Further, as the calling side device which is effective in the above-mentioned first data communication system, as shown in claim 4, the called side device is used by using the public line in which the charge is collected by the generation of the charging pulse. In a calling side device that performs data communication with the device, a charging pulse detecting means for detecting a charging pulse, and the generation cycle of the charging pulse is calculated based on the charging pulse detected by the charging pulse detecting means. And a transmission / reception control for stopping transmission / reception of data immediately before the generation timing of the charging pulse predicted based on the generation cycle calculated by the generation cycle calculation means and resuming transmission / reception of data after the generation of the charging pulse. Means and the transmission / reception control means interrupt the transmission of data, the transmission interruption information is added to the transmission data immediately before the interruption, and the incoming call is received. Include those characterized by comprising a transmission interruption information notifying means for notifying the device.

As a calling side device which is effective in the above-mentioned second data communication system, as shown in claim 5, a public line in which a charge is collected by generation of a charging pulse is used. In a calling side device that performs data communication with a called side device, charging pulse detection means for detecting a charging pulse, and generation of the charging pulse based on the charging pulse detected by the charging pulse detection means A generation cycle calculating means for calculating a cycle, data transmission / reception is stopped immediately before the charging pulse generation timing predicted based on the generation cycle calculated by the generation cycle calculation means, and data transmission / reception is restarted after the generation of the charging pulse. Transmission / reception control means, and generation cycle notification means for notifying the called side device of the generation cycle calculated by the generation cycle calculation means. Include those wherein and.

The operation of these calling side devices has been described in the description of the operation of the above-mentioned first and second data communication systems, and will not be repeated here.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram of a data communication system according to an embodiment. This data communication system roughly includes a terminal device 1 that functions as a calling side device or a called side device, a public telephone line 30 as a public line, and a called side device or a calling side device in some cases. It is composed of a functioning partner station 50.

The terminal device 1 has a CPU 10 as a control means for controlling the operation of the entire terminal device.
In the PU 10, a RAM 12 that is a work area of the operation program of the CPU 10, a ROM 14 that stores the operation program of the CPU 10, and a public telephone line 30
Connection / disconnection of the line between the modem 16 that transmits and receives data to and from the modem of the partner station 50 that is the communication partner, and the network
And NCU (Network Control Unit) 18 for dialing, and CPU for detecting the presence or absence of a charging pulse
The charging pulse detection circuit 20 for notifying 10 is connected.

The CPU 10 uses the modem 16 based on a call request received from a personal computer or the like connected from the outside.
And control the NCU 18. When the terminal device 1 functions as a calling side device, the CPU 10 includes an “occurrence period calculation means”, a “transmission / reception control means”, a “transmission interruption information notification means” or a claim 3 according to claim 2. It corresponds to the "occurrence period notifying means" shown in. On the other hand, when the terminal device 1 functions as a called side device, the "reception control means" according to claim 2 or the "transmission / reception control means" according to claim 3
Is equivalent to

Of course, the partner station 50, which is the partner of communication, basically has each of such means. However, for example, when the partner station 50 is configured to function only as a called side device, The above-mentioned "occurrence period calculating means", "transmission / reception control means", "transmission interruption information notifying means", and "occurrence period notifying means" may not be provided.

Next, the operation of the data communication system of this embodiment will be described with the terminal device 1 side as the main focus. FIG.
6 is a flowchart showing a process executed by the calling side device, here, a process executed by the CPU 10 when the terminal device 1 becomes the calling side device.

First, off-hook is performed in the first step S1, and dial processing is executed in the subsequent step S2. The presence or absence of the charging pulse is determined by the interrupt process shown in the flowchart of FIG. 4. In connection with this, in S3, the interrupt counter is cleared (cnt = 0) and the interrupt is permitted. After the process of S3 is completed, the process proceeds to S4.

In S4, the operation after dialing of a general modem is performed. That is, processing such as confirmation of the own station and the partner station and setting of the communication speed by the training sequence is performed.
In subsequent S5, data is transmitted / received, and after the communication is completed, S6
On-hook to disconnect the line.

Similarly, FIG. 3 is a flowchart showing the operating state of the called side device (for example, the partner station 50 shown in FIG. 1). In the first step S11, a ringing tone is detected, and in the subsequent step S12, it goes off hook. Since the charging side does not detect the charging pulse, there is no processing corresponding to S3 in FIG. S
The processing of 13 to S15 is the same as the processing (S4 to S6 of FIG. 2) of the calling side device (in this case, the terminal device 1), and therefore description thereof will be omitted.

Next, the interrupt processing executed by the terminal device 1 when the charging pulse occurs will be described with reference to FIG. In the first step S20, the interrupt counter cnt
When the interrupt counter cnt is "0", the process proceeds to S21, and when the interrupt counter cnt is not "0", the process proceeds to S23.

S21 and S22 executed subsequently
Is a process executed when the first billing pulse is detected after the off-hook. In S21, the interrupt counter is incremented (cnt = cnt + 1), and S22 is executed.
Then, the reference time t1 for measuring the charging pulse period T is stored. After the processing of S22, this interrupt processing is exited.

On the other hand, the processing of S23 to S25 is executed when the second charging pulse is detected after the off-hook. In S23, the current time t2 is measured, and the subsequent S24.
Then, the time t1 measured last time is subtracted from the time t2 measured this time to obtain the charging pulse period T (T = t2-t
1). Then, in S25, the interruption of the charging pulse is prohibited, and then this interruption processing is finished.

Here, the calling side device (for example, the terminal device 1)
The data communicated between the called device and the called device (for example, the partner station 50) will be described. 7 and 8 show HDLC (high
level data link control procedure) is an example of a communication format, FIG. 7 is a data block format, and FIG. 8 is a frame format. In this example, 256 bytes of data form one frame as shown in FIG. 8, and 32 frames form one block as shown in FIG.

The flag shown in FIG. 8 is a data pattern for synchronizing the modems on the transmitting side and the receiving side, and is a pattern that does not appear in the original data. Therefore, when receiving data other than the flag pattern after receiving the flag pattern, the receiving modem can determine that the data is the head data of the original data (control in this example).

The FCS (frame check sequence) is data for checking a CRC error on a frame-by-frame basis, and normally a modem chip automatically transmits the data. The control field defines various data defined by the communication protocol such as data attributes.

In the present embodiment, "transmission interruption information" is defined in the control field. In order to avoid the charging pulse, the data transmitting side informs the data receiving side of "transmission interruption" in the control field of the frame sent immediately before the generation timing of the charging pulse, and interrupts the data transmission. After receiving the HDLC frame, the data receiving side
If "transmission interruption" is set in the control field, the reception is temporarily interrupted, and the reception is restarted at a predetermined timing. The reason why the data receiving side suspends the reception is to facilitate synchronization when resuming.

FIG. 9 shows a transmission frame in the case where communication is performed by avoiding the timing of the charging pulse. Here, a communication speed of 7200 bps will be described as an example. H
The data of one block of DLC is (256 + 3 + 2 + 2)
× 32 = 8416 bytes, and the time required for this transmission / reception is 8416 × 8/7200 = about 9.35 seconds.
Depending on the characteristics of the modem chip, in HDLC mode,
When a charging pulse is generated during data reception, it is often the case that the HDLC frame sent after the generation of the charging pulse cannot be received. Therefore, for example, if a charging pulse occurs during the first frame communication of HDLC, all the remaining 31 frames cannot be received, and a wasteful time of about 9.35 seconds occurs.

Based on such a premise, the flow chart of FIG. 5 shows the HDLC block transmission operation in the case where the data transmission side (in this case, the terminal device 1 as the calling side device) takes a charging pulse countermeasure. It will be described with reference to FIG.
In the first step S31, the frame number FN to be transmitted
O is initialized, and the current time t3 is measured in subsequent S32.

After measuring the current time t3 in S32,
At 33, the difference (t2 + T-t3) between the time when the next charging pulse is generated and the current time is obtained, and the step to be shifted is determined according to the difference. That is, the difference is 1.5
If it is smaller than the second, the processing proceeds to S39, if it is larger than 1.8 seconds, the processing proceeds to S35, and if it is 1.5 seconds or more and 1.8 seconds or less, the processing proceeds to S34.

In S34, "transmission interruption information" is set in the control field of the frame to be transmitted,
Then, the process proceeds to S35. In step S35, the FNO frame is transmitted, and in step S36, the completion of the transmission is awaited. When the transmission is completed, the process proceeds to S37.

In S37, the number of transmission frames is incremented (FNO = FNO + 1). And S38 continues
Then, it is determined whether or not the transmission of all frames is completed, and if completed, the HDLC block transmission is terminated.
On the other hand, in S39, when the difference between the time when the next charging pulse is generated and the current time is smaller than 1.5 seconds is determined in S33, the transmission is interrupted until the charging pulse is generated, and if it is detected, The process proceeds to S40. In S40, the time when the charging pulse is generated is stored as t2.

Here, the calculation method of 1.5 seconds and 1.8 seconds used in the determination of S33 will be described with reference to FIG. In the case of 7200 bps, the time required to transmit one frame is (256 + 3 + 2 + 2) × 8/7200 = about 0.3 seconds. Also, the charging pulse is about 1 second,
In the present embodiment, it is assumed that the billing pulse is detected at the last timing of the 1 second. Furthermore, a margin of 0.2 seconds is provided to prevent the influence of measurement error and the like. When the total time of these becomes about 1.5 seconds, if the process of S32 of FIG. 5 is executed at the timing [A] in FIG. 10, two frames can still be transmitted before the charging pulse is generated. Further, if the process of S32 is executed at the timing of [B], only one frame can be sent before the charging pulse is generated, so "transmission interruption information" is set in the frame to be sent. And
If the process of S32 is executed at the timing of [C], no more frames can be sent before the charging pulse is generated, so the generation of the charging pulse is awaited.

On the other hand, the process of receiving the HDLC block when the data receiving side (in this case, the called station 50 which is the called side device) takes measures against the charging pulse will be described with reference to the flowchart of FIG. In the first step S41, the frame number to be received is initialized, and in the subsequent S42, frame reception is started. Then, in S43, the completion of the frame reception is waited, and when the reception is completed, the process proceeds to S44. In S44, the number of received frames is incremented (FNO = FNO + 1).

In the subsequent S45, the number of received frames is determined, and if reception of all frames is completed (S45).
45: YES), this reception process ends, but if it is still necessary to receive (S45: NO), the process proceeds to S46. In S46, it is determined whether or not the "transmission interruption information" in the control field of the frame just sent is set (S46: N).
O), and returns to S42. On the other hand, if it is set (S4
(6: YES), the process proceeds to S47, and the reception is temporarily stopped to facilitate synchronization. Then, after waiting for a predetermined time (here, 1 second) in S48, the process proceeds to S42 and the reception is restarted again.

As described above, in the data communication system according to the present embodiment, the terminal device 1 as the calling side device detects the charging pulse and calculates the charging pulse generation period based on the detected charging pulse. Then, the data transmission / reception is stopped immediately before the charging pulse generation timing predicted based on the calculated generation period, and the data transmission / reception is restarted after the charging pulse generation ends. Further, when the data transmission is interrupted, the transmission interruption information is added to the transmission data immediately before the interruption, and the destination station 50 which is the called side device is notified. Then, the partner station 50 that has received the notification interrupts the data reception, and resumes the data reception after the elapse of a predetermined time.

Thus, when data communication is performed between the terminal device 1 as the calling side device and the partner station 50 as the called side device, it is possible to prevent the adverse effect of the charging pulse. In the above embodiment, when the terminal device 1 as the calling side device interrupts the data transmission (that is, every time the data is interrupted), the transmission interruption information is added to the transmission data immediately before the interruption, and the incoming call is received. In order to notify the partner station 50 as the side device, the partner station 50 interrupts the data reception when the transmission interruption information is notified, and resumes the data reception after a lapse of a predetermined time. That is, the interruption of data reception is executed based on the transmission interruption information from the terminal device 1 each time the transmission interruption information is received.

Assuming that the terminal device 1 shown in FIG. 1 is a calling side device and cannot transmit data, and the partner station 50 is a called side device and only receives data, the calling side device is Only a certain terminal device 1 needs to have the function of detecting the charging pulse or calculating the generation period. Of course, if the partner station 50 also functions as a calling side device and also transmits data, it is necessary to have a function of detecting a charging pulse or calculating a generation period.

It is also possible to consider another system which can serve as the data transmission side without having the function of detecting the charging pulse or calculating the generation period. That is, the calling device
If the generation cycle of the charging pulse is calculated, the generation cycle may be notified to the called side apparatus, and the called side apparatus may separately control transmission / reception of data based on the notified generation cycle. Good.

That is, when the data is interrupted (that is,
In a system in which transmission interruption information is added to the transmission data immediately before the interruption at each interruption and the called apparatus is notified, the called apparatus is based on the transmission interruption information (that is, the information is used as a trigger). ), The reception of data is interrupted.
On the other hand, in the case of the other system, once the generation period notified from the calling side device is received, the called side device then separately transmits and receives data based on the notified period. Can be controlled. In the above-described embodiment, when the generation cycle of the charging pulse is calculated in the terminal device 1 as the calling side device, it may be notified to the partner station 50 as the called side device.

For example, when a karaoke terminal acquires new song data from an information center as in a so-called communication karaoke system, not only song data transmitted from the information center but also identification information transmitted from the karaoke terminal and Since there is a certain amount of log information and the like, it is not preferable that the charging pulse signal is adversely affected during transmission. Therefore, in such a case, it is better that both the calling side device and the called side device execute predetermined transmission / reception control based on the charging pulse generation period T. Therefore, for example, when the period T is calculated at the karaoke terminal which is the calling side device, it is preferable to use a system that immediately transmits the period T to the information center.

The present invention is not limited to such embodiments as described above, and can be carried out in various modes without departing from the scope of the present invention. For example, in the above embodiment, taking the case of 7200 bps as an example, the time required to transmit one frame is (256 + 3 + 2 + 2) ×
8/7200 = about 0.3 seconds is adopted. At other communication speeds, the time required to transmit this one frame changes. For example, in the case of 2400 bps, (256+
3 + 2 + 2) × 8/2400 = about 0.9 seconds.

Further, regarding the calculation of the charging pulse period,
You may make it measure several times and correct an error.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a data communication system according to an embodiment.

FIG. 2 is a flowchart showing an operation of a terminal device as a calling side device.

FIG. 3 is a flowchart showing an operation at a partner station as a called side device.

FIG. 4 is a flowchart showing an interrupt process in the terminal device.

FIG. 5 is a flowchart showing a transmission operation in the terminal device.

FIG. 6 is a flowchart showing a receiving operation at a partner station.

FIG. 7 is an explanatory diagram of a format of an HDLC data block.

FIG. 8 is an explanatory diagram of a format of an HDLC frame.

FIG. 9 is an explanatory diagram of a transmission frame when communication is performed at a timing other than the charging pulse timing.

FIG. 10 shows 1.5 seconds and 1. used in the process of FIG.
It is explanatory drawing of the calculation method of 8 seconds.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Terminal device 10 ... CPU 12 ... RAM 14 ... ROM 16 ... Modem 18 ... NCU (Network control unit) 20 ... Charging pulse detection circuit 30 ... Public telephone line 50 ... Partner station

Claims (5)

[Claims] 1. A data communication method for performing data communication using a public line in which a charge is collected by generation of a charging pulse, wherein the charging pulse is detected after the connection to the public line is started,
The generation cycle of the charging pulse is calculated, and thereafter, transmission / reception of data is stopped immediately before the generation timing of the charging pulse predicted based on the generation cycle,
A data communication method characterized in that data transmission / reception is restarted after the generation of a charging pulse. 2. A data communication system for performing data communication between a calling side device and a called side device by using a public line in which a charge is collected by generation of a charging pulse, wherein the calling side device. The charging pulse detecting means for detecting the charging pulse, the generation cycle calculating means for calculating the generation cycle of the charging pulse based on the charging pulse detected by the charging pulse detecting means, and the generation cycle calculating means. Transmission / reception control means for stopping data transmission / reception just before the generation timing of the charging pulse predicted based on the calculated generation cycle and resuming data transmission / reception after the generation of the charging pulse, and transmission / reception of data by the transmission / reception control means. In the case of interruption, notification of transmission interruption information is sent to the called device by adding transmission interruption information to the transmission data immediately before interruption. On the other hand, the callee device interrupts data reception when the caller device notifies the transmission interruption information, and resumes data reception after a predetermined time elapses. A data communication system comprising a control means. 3. A data communication system for performing data communication between a calling side device and a called side device by using a public line in which a charge is collected by generation of a charging pulse, wherein the calling side device. The charging pulse detecting means for detecting the charging pulse, the generation cycle calculating means for calculating the generation cycle of the charging pulse based on the charging pulse detected by the charging pulse detecting means, and the generation cycle calculating means. A transmission / reception control unit that stops transmission / reception of data immediately before the generation timing of the charging pulse predicted based on the calculated generation period and restarts transmission / reception of data after the generation of the charging pulse; and the generation period calculated by the generation period calculation unit. And a generation cycle notifying unit for notifying the callee side device of the occurrence cycle, wherein the callee side device is notified by the caller side device. It stops the transmission and reception of data immediately before the generation timing of the charging pulses predicted on the basis of the generation period, the data communication system, characterized in that it comprises a transmission and reception control means for resuming the transmission and reception of data after the occurrence completion of charging pulses. 4. A billing pulse detection for detecting a billing pulse in a calling side device that performs data communication with a called side device by using a public line in which a charge is collected by generating a billing pulse. Means, a generation cycle calculation means for calculating a generation cycle of the charging pulse based on the charging pulse detected by the charging pulse detection means, and a charging pulse predicted based on the generation cycle calculated by the generation cycle calculation means. Transmission / reception control means for stopping transmission / reception of data immediately before the generation timing and resuming transmission / reception of data after the generation of the charging pulse, and in the case of interrupting data transmission by the transmission / reception control means, the transmission data immediately before the interruption A calling side device, further comprising transmission interruption information notifying means for adding transmission interruption information and notifying the called side device. 5. A billing pulse detection for detecting a billing pulse in a calling side device that performs data communication with a called side device by using a public line whose fee is collected by generating a billing pulse. Means, a generation cycle calculation means for calculating a generation cycle of the charging pulse based on the charging pulse detected by the charging pulse detection means, and a charging pulse predicted based on the generation cycle calculated by the generation cycle calculation means. Transmission / reception control means for stopping transmission / reception of data immediately before the generation timing and resuming transmission / reception of data after the generation of the charging pulse, and generation cycle notification means for notifying the called side device of the generation cycle calculated by the generation cycle calculation means. And a calling side device.