JPH05130271A - Data communication method and tone signal eliminating device used for it - Google Patents

Abstract

PURPOSE:To expand the degree of freedom of environment setting for data communication by eliminating a specific tone signal so as not to input the signal to a terminal equipment when the tone signal is sent from an exchange in a telephone line network to the terminal equipment. CONSTITUTION:In the data communication method using a telephone line network 2, a tone signal elimination device 5 is provided between a communication terminal equipment 3 and a telephone line 21. When a specific tone signal S2 is sent from an exchange 20 in the telephone line network 2 to the communication terminal equipment 3, the tone signal S2 is eliminated before being inputted to the communication terminal equipment 3. Thus, when the communication terminal equipment 3 and the telephone line network 2 are connected, it is not required to select the telephone line on which the tone signal S2 is not superimposed, resulting in being a communication fault. Thus, the degree of freedom of the environment setting for data communication is expanded. Furthermore, for example, when the portable communication terminal equipment is connected to a telephone line of a moving destination to implement data communication, a limit in the communication in terms of location is relaxed.

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 telephone line network as a communication line. In recent years, facsimile machines and personal computers having communication functions have spread, and existing telephone line networks (public telephone line networks and dedicated telephone line networks) originally constructed for telephone calls (personal information exchange).
Data communication using is becoming widespread. And, such data communication is expected to become more and more popular as restrictions on using telephone lines are eased and become easier.

[0002]

2. Description of the Related Art In data communication using a telephone line which is an analog line, information in digital form is transmitted by a modem (voice band modem) in the form of an analog signal obtained by modulating each carrier for transmission and reception. As a modulation method, a frequency shift keying method (FSK) or a phase shift keying method (PSK) is generally used.

[0003]

In the telephone line network, various services (processing contents) provided by exchanges (local exchanges or private branch exchanges) are provided for the convenience of subscribers and efficient operation of the network. In some of these services, the exchange sends a specific tone signal to the communication terminal device during a call to notify or warn the subscriber.

For example, for a telephone line registered to enjoy a call waiting service (called "call waiting service" in the NTT subscriber telephone service) that enables interruption of a call between two parties by a third party. When an interrupt request is made, a tone signal is sent to notify that effect.

However, in a telephone line provided with a service accompanied by transmission of such a tone signal, the transmission signal is disturbed due to the superposition of the tone signal, and a communication abnormality occurs.
Cannot be used for data communication.

[0006] In other words, conventionally, when setting an environment for data communication, as a telephone line for connecting a communication terminal device, a line in which a tone signal that hinders communication is not transmitted, that is, a line in which a service to be enjoyed is limited. There was a problem that it had to be provided.

For this reason, when one telephone line is shared for telephone calls and data communications, various services are not provided, and the convenience of telephone calls is impaired. Even if the communication terminal device is a portable type, the telephone line provided at the destination is often an unusable line, and the use place (access point) of the communication terminal device is limited.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to increase the degree of freedom of environment setting for data communication.

[0009]

In order to solve the above-mentioned problems, the method according to the invention of claim 1 is as follows, as shown in FIG.
In the data communication method using the telephone line network 2 as a communication line, when a specific tone signal S2 is sent from the exchange 20 in the telephone line network 2 to the communication terminal device 30, the tone signal S2 is used as the communication terminal. The device 3 is removed so as not to be input.

A device according to the invention of claim 2 is a telephone line 2
1. A line side interface unit 51 for separating a signal input via 1 into a DC component SDC and an AC component SAC, and a level for detecting the presence or absence of superposition of a specific tone signal S2 based on the signal level of the AC component SAC. Detector 51
And a filter unit 54 having a frequency characteristic that allows the specific tone signal S2 to pass, and the AC component SAC is added to the filter unit 54 only when the level detector 51 detects the superposition of the tone signal S2. Switching section 53 for outputting the output signal S of the filter section 54
54 and a tone signal removing unit 55 that outputs a signal S55 corresponding to the level difference between the AC component SAC, a signal S55 output from the tone signal removing unit 55, and the DC component SDC to synthesize the communication terminal device. 3 and a terminal-side interface unit 56 for outputting to 3.

[0011]

The specific tone signal S2 emitted by the exchange 20 in the telephone line network 2 is removed by the tone signal removing device 5 provided between the communication terminal device 3 and the telephone line 21.

That is, the signal (original signal) transmitted from the exchange 20 to the communication terminal device 3 via the telephone line 21 is:
First, the line side interface unit 51 of the tone signal removing device 5 separates the DC component SDC and the AC component SAC.

The AC component SAC is applied to the filter unit 54 via the switching unit 53, whose signal level is detected by the level detecting unit 51 and which is closed only when the tone signal S2 is superposed. The tone signal S2 is extracted from the AC component SAC by the filter unit 54, and the extracted tone signal S2 is added to the tone signal removing unit 55.

The tone signal removing section 55 equivalently performs a process of reducing the AC component SAC by the level of the tone signal S2, thereby removing the tone signal S2. After that, the terminal side interface unit 56 combines the output signal S55 of the tone signal removing unit 55 and the previously separated DC component SDC, and sends the combined signal to the communication terminal device 3 as communication information.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram schematically showing the structure of a main part of a communication system 1 according to the present invention. The communication system 1 includes an exchange 20 and subscriber telephone lines 21, 22 accommodated therein.
A public telephone line network (hereinafter, simply referred to as “network”) 2 composed of 23, a communication terminal device 3 such as a personal computer connected to the network 2 via a subscriber telephone line 21, and a network 2 via a subscriber telephone line 22. The host computer 4 and the like connected to the.

Communication terminal device 3 and host computer 4
Are network control units (NCU) for automatic transmission and reception
And a modem for data communication by an analog transmission method.

The subscriber telephone line 21 is a line to which a call waiting service is provided, and a tone signal removing device 5 described later is provided between the communication terminal device 3 and the subscriber telephone line 21.

In such a communication system 1, for example, a call is made by the communication terminal device 3 side, a call is made to the host computer 4 by the exchange 20, and a host computer 4
The subscriber telephone lines 21 and 22 are connected through a series of processes similar to those at the time of a call, such as a response, and data communication is performed between the communication terminal device 3 and the host computer 4. In the call connection process by the exchange 20 at this time, a call and a data communication are not distinguished.

Now, during the data communication, the subscriber telephone line 23
It is assumed that a call is made to the subscriber telephone line 21 by the telephone 6 connected to. In such a case, since the subscriber telephone line 21 is normally connected (non-vacant state), the exchange 20 only sends the busy tone to the subscriber telephone line 23. However, in the communication system 1, since the subscriber telephone line 21 is a line for providing the call waiting service as described above, the exchange 20 sends the tone signal S2 to the subscriber telephone line 21 to notify the interruption request.

Therefore, at this time, for example, if the information signal S1 is being transmitted from the host computer 4 to the communication terminal device 3, the mixed signal S12 in which the tone signal S2 is superimposed on the information signal S1 is transmitted to the subscriber telephone line 21. It becomes a signal (an input signal viewed from the communication terminal device 3 side).

However, if the mixed signal S12 is directly input to the communication terminal device 3, the communication terminal device 3 may perform erroneous demodulation or disable demodulation, and information may not be transmitted normally.

Therefore, the communication system 1 of the present embodiment is provided with the tone signal removing device 5, whereby a signal obtained by removing the tone signal S2 from the mixed signal S12, that is, the information signal S1 corresponding to the normal information is transmitted to the communication terminal. Input to the device 3.

FIG. 2 is a block diagram showing the configuration of the tone signal removing device 5, and FIG. 3 is a voltage waveform diagram showing the operation of each part of the tone signal removing device 5. The tone signal removing device 5 uses the subscriber telephone line 21 to insert the device 5 into the communication path.
Side and the communication terminal device 3 side, a pair of interface units 51 and 56, a level detection unit 52 for detecting the tone signal S2, a filter unit including an active filter having a frequency characteristic for transmitting the tone signal S2, and the like. 54, a switching unit 53 including an analog switch for adding only the mixed signal S12 on which the tone signal S2 is superimposed to the filter unit 54, and a signal corresponding to the level difference between the mixed signal S12 and the tone signal S2.
And a tone signal removing section 55 for outputting as.

Each of the interface units 51 and 56 is composed of a signal separation / synthesis unit 60 composed of a capacitor C and a choke coil L, and a 2-wire to 4-wire conversion unit 61 composed of a hybrid coil or an electronic circuit including an active element. ing.

The signal separating / combining unit 60 is used for two-way communication between the communication terminal device 3 and the host computer 4 from the subscriber telephone line 21 side (host computer 4 side) or the communication terminal device 3 side. The transmission signal inputted to the DC component SDC and the AC component SAC are temporarily separated, and each component SD is used for sending the transmission signal to the communication terminal device 3 side or the subscriber telephone line 21 side.
C and SAC are synthesized.

That is, the signal separation / synthesis unit 60 branches the AC component SAC to be subjected to signal processing and the DC component SDC related to a so-called DC loop formed between the communication terminal device 3 and the exchange 20, and In order to prevent the tone signal removing device 5 from affecting the DC loop,
The DC component SDC is provided to substantially bypass the tone signal removing device 5.

In the tone signal removing device 5, the 2-line to 4-line converting section 61 divides the AC component SAC into a reception signal (a signal requiring tone signal removal) and a transmission signal viewed from the communication terminal device 3 side. It is provided.

Further, the tone signal removing section 55 of the present embodiment.
Is a voltage follower unit 551 inserted for preventing backflow of a signal in the transmission line LR on the reception side connecting between the 2-wire to 4-wire conversion units 61, the voltage follower unit 551 and the filter unit 54 described above. Inverting amplifier 552 inserted between the output terminals of the
Consists of.

In the tone signal removing device 5, an amplifier 57 is provided in the transmission line LR (between the interface section 51 and the voltage follower section 551), and each 2-wire to 4-wire converting section 61 is connected. An amplifier 57 is provided in the transmission line LT on the transmitting side, and these amplifiers 57 and 58 attenuate the signal inside the tone signal removing device 5 (internal loss).
The signal is amplified to compensate for this.

The operation of the tone signal removing device 5 will be described below, focusing on reception as seen from the communication terminal device 3 side.
When performing data communication, the host computer 4 operates as shown in FIG.
Based on the serial digital information (data) shown in (a), an information signal S1 shown in FIG. 3 (b) is generated by, for example, a frequency shift keying method, and the information signal S1 is sent to the communication terminal device 3. ..

At all times, the tone signal removing device 5 is
The information signal S1 input via the subscriber telephone line 21 is sent to the communication terminal device 3 as it is without any substantial processing.

Now, as shown in FIG. 3C, time t1
In, it is assumed that a predetermined tone signal S2 (the frequency and the signal level of which are predetermined) relating to the call waiting service is superimposed on the information signal S1. In addition,
Usually, the signal level (maximum amplitude) of the information signal S1 is smaller than that of the tone signal S2.

When the tone signal S2 is superimposed on the information signal S1, the AC component SAC output from the interface section 51 to the transmission line LR is the mixed signal S1 shown in FIG. 3 (d).
It becomes 2.

At this time, the level detector 52 outputs the tone detection signal S52 at the time t2 when the signal level of the mixed signal S12 is out of the preset level range Vr. The tone detection signal S52 is continuously output while the tone signal S2 is superposed thereafter. Such an operation of the level detection unit 52 can be realized by combining a window comparator and a logic circuit, for example.

Upon receiving the tone detection signal S52, the switching section 53 closes the signal path. As a result, the mixed signal S
12 joins the filter unit 54. As shown in FIG. 3E, the filter unit 54 outputs the frequency component corresponding to the tone signal S2 in the mixed signal S12 as the signal S54. That is, the signal S54 corresponds to the tone signal S2 slightly attenuated by the internal loss of the filter unit 54.

Inversion amplification section 552 of tone signal removal section 55
Is a signal S obtained by appropriately amplifying and phase inversion of the signal S54.
552 [see FIG. 3 (f)] is output. And the signal S
When 552 is superimposed on the mixed signal S12 that has passed through the voltage follower unit 551, the tone signal S2 and the signal S552 cancel each other, so that the mixed signal S12 changes to the tone signal S2.
The tone signal removing unit 55 outputs the signal S55 (see FIG. 3 (g)) from which the tone signal has been removed.

Here, the switching unit 53 is not provided, and
It is conceivable that the signal component of the frequency corresponding to the tone signal S2 is always removed by directly adding the signal from the line-to-four-line converting unit 61 to the filter unit 54. Then, the tone signal is added to the information signal S1. A problem occurs when a signal component having the same frequency as S2 is included. Therefore, the tone signal removing device 5 is provided with the level detecting unit 52 and the switching unit 53, and the tone signal removing unit 55 is configured to substantially function only when the tone signal S2 is superimposed.

It should be noted that there is a slight deviation between the timing t1 at which the tone signal S2 is superimposed and the timing t2 at which the tone detection signal S52 is output (that is, the timing at which the tone signal S2 is removed), which causes FIG. 3 (g). As shown in, the signal S55 may be a slightly disturbed signal, but in reality, the period in which the disturbance occurs is extremely shorter than the 1-bit time T, so that there is no problem in demodulation.

After that, the signal S55 goes through the 2-line to 4-line converting section 61 and the signal separating / combining section 60 of the interface section 56 in this order, and is superimposed on the DC component SDC.
Is sent to the communication terminal device 3.

According to the above-described embodiment, since the subscriber telephone line 21 related to the call waiting service can be used for data communication without any hindrance, the subscriber telephone line 21 does not impair the convenience of the call due to the enjoyment of the call waiting service. Can be shared for calls and data communications.

In the above embodiment, the tone signal removing section 55 is not limited to the above configuration. For example, a phase inverter and an amplifier may be provided instead of the inverting amplifier 552. Further, the tone signal removing unit 55 is configured by a differential amplifier, and the output signal S54 of the filter unit 54 and the mixed signal S
A signal corresponding to the level difference from 12 may be taken out as the information signal S1.

In the above-described embodiment, the tone signal removing device 5 makes the level range Vr serving as the reference for detection by the level detecting section 52 and the frequency specification of the filter section 54 variable, and the frequency and the signal are changed according to the type of service. It is possible to selectively remove various tone signals S2 having defined levels. That is, in addition to the call waiting service, a so-called three-minute call service provided in, for example, a private branch telephone exchange network provided in a general company (for the purpose of reducing communication costs, the caller is notified of the elapse of the call time every three minutes). It is possible to remove the tone signal related to the notification service).

In the above embodiment, the tone detection signal S
Based on 52, superimposition of the tone signal S12 (that is, generation of an interrupt request from a third party) may be displayed. According to this, the operator of the communication terminal device 3 knows the occurrence of the interrupt request, and after taking interruption of the data communication, it is possible to take a measure such as responding to a third party using a telephone or the like attached to the communication terminal device 3. it can. It is also possible to send the tone detection signal S52 to the communication terminal device 3 and cause the communication terminal device 3 to execute a process for responding to a third party. In addition, the circuit configuration of the tone signal removing device 5 can be variously changed by appropriately providing an amplifier, a phase correction means, an impedance matching means, etc.

Although the tone signal removing device 5 is provided separately from the communication terminal device 3 in the above embodiment, the tone signal removing device 5 is provided, for example, in the communication terminal device 3.
May be incorporated into the modem of

[0045]

According to the present invention, when connecting a communication terminal device and a telephone line network, it is not necessary to select a telephone line on which a tone signal that hinders communication is not superimposed. The degree of freedom can be expanded.
In addition, for example, when a portable communication terminal device is connected to a destination telephone line to perform data communication, it is possible to ease restrictions on the location of communication.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of a main part of a communication system according to the present invention.

FIG. 2 is a block diagram showing a configuration of a tone signal removing device.

FIG. 3 is a voltage waveform diagram showing an operation of each unit of the tone signal removing apparatus.

[Explanation of symbols]

 2 Public telephone line network (telephone line network) 20 Switch 3 Communication terminal device S2 Tone signal 21 Subscribed telephone line (telephone line) 51 Interface part (line side interface part) 52 Level detection part 53 Switching part 54 Filter part 55 Tone signal removal 56 Interface section (terminal side interface section)

Claims (2)

[Claims] 1. A data communication method using a telephone line network (2) as a communication line, wherein a specific tone signal (S2) is sent from an exchange (20) in the telephone line network (2) to a communication terminal device (3). ) Is sent, the tone signal (S2) is removed so as not to be input to the communication terminal device (3). 2. A line side interface section (51) for separating a signal inputted through a telephone line (21) into a direct current component (SDC) and an alternating current component (SAC), and a signal of the alternating current component (SAC). A level detection unit (52) for detecting the presence or absence of superposition of a specific tone signal (S2) according to a level; a filter unit (54) having a frequency characteristic for passing the specific tone signal (S2); Tone signal (S2) by the level detector (52)
Of the alternating current component (SAC) only when the superposition of
And a signal (S5) corresponding to the level difference between the output signal (S54) of the filter unit (54) and the AC component (SAC).
5) for outputting the tone signal removing unit (55) and the signal (S) output from the tone signal removing unit (55).
55) and the direct current component (SDC) are combined and output to the communication terminal device (3).
A tone signal removing apparatus comprising: