JP2001061006A - Low-pass filter circuit and device for telephone line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable simultaneous use of data communication and sound communi cation by constituting a low-pass filter and a device for telephone line of two inductors electrically inserted between a telephone line socket and a telephone set and a capacitor serially inserted to those two inductors. SOLUTION: This low-pass filter and a device for telephone line are constituted of two inductors L electrically inserted between the telephone line socket and the telephone set and the capacitor C serially inserted to those two inductors L. Effects such as relative suppression of fluctuation of an impedance of a modem from the viewpoint of the telephone line, improvement of attenuation of a data signal and suppression of leakage of the data signal to the telephone set are obtained by the low-pass filter circuit when the data communication using a splitterless ADSL system and the conventional sound communication are simultaneously used under a condition that plural telephone line sockets exist on one telephone line. As a result, simultaneous use of the data communication using the splitterless ADSL system and the conventional sound communication is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ITU-T standardized specification (Splitterless Asymmetric Digital Subscriber).
r Line Transceiver; a splitterless ADSL system).

[0002]

2. Description of the Related Art In communication using a conventional telephone line,
It was impossible to transmit and receive data signals and voice signals simultaneously. However, in recent years, ADSL which transmits and receives data signals using a frequency band higher than an audio signal band
With the development of the technology, practical use for simultaneously transmitting and receiving a data signal and a voice signal is being studied.

ADSL includes two types of systems, one that requires a device called a splitter for distributing data signals and voice signals at the telephone line entrance of a subscriber's home, and the other that does not require a splitter. ADSL is
It is said that a telephone or a modem can be directly connected to the telephone line and used. ADSL that does not require this splitter is called splitterless ADSL.

[0004]

However, when there are a plurality of telephone lines on a single telephone line, the splitterless ADSL has a form in which a modem and a telephone are connected in parallel on the same line. The relative value of the impedance of the modem viewed from the line side varies depending on the number of connected telephones and the impedance value of the telephone.

[0005] At this time, data transmission characteristics are affected, and it is difficult to transmit and receive data signals using a modem.

Accordingly, an object of the present invention is to provide a low-pass filter circuit and apparatus for a telephone line which can solve the above-mentioned problems and can simultaneously use data communication and voice communication.

[0007]

In the present invention, it is possible to improve the transmission characteristics of a data signal by a low-pass filter device for a telephone line comprising an inductor L and a capacitor C as shown in FIG. The result was obtained. That is, as shown in the frequency response characteristic of FIG. 2, by designing the inductor in the filter device installed on the telephone side to have a high impedance characteristic in the data communication band, relative to the telephone line side. Even when the impedance value of the modem can be suppressed from being varied, and a capacitor is inserted in series with the inductor even in a state where the inductor has a high impedance, a low-pass filter device for a telephone line that can simultaneously use audio signals can be obtained.

That is, the present invention is a telephone line low-pass filter circuit comprising two inductors electrically inserted between a telephone line port and a telephone, and a capacitor inserted in series with the two inductors.

Further, the present invention is the above-mentioned low-pass filter circuit for a telephone line, which passes only an audio signal among a data signal (25 kHz to 552 kHz) and an audio signal (up to 4 kHz) transmitted through the telephone line.

Further, the present invention is a telephone line low-pass filter device using the above-mentioned telephone line low-pass filter circuit.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

First, in the case where a plurality of telephone lines are present on one telephone line, a state in which one modem and three telephones are connected to the same line is described in ITU-TG.
3 (a), 4 (a), 5
(A) and FIG. 6 (a) show an electronic circuit diagram.

FIGS. 3 (a) and 5 (a) show a measurement system when the low-pass filter device of the present invention is not inserted between the telephone line port and the telephone, and FIG. 4 (a). ,
FIG. 6A shows a measurement system in a case where the low-pass filter device of the present invention is inserted between a telephone line port and a telephone.

The telephone A shown in FIGS. 5 (a) and 6 (a)
Is 600Ω.

First, in the measurement system shown in FIGS. 3A and 4A, the telephone A is not used, the telephones B and C are in use, and the modems are also in use. This is a case where the voice signal and the data signal are oscillating. FIGS. 3B and 4B show attenuation characteristics of the data signal measured at the home modem point in this case.

3 (b) and 4 (b), a comparison is made between the case where the low-pass filter device of the present invention is not mounted on the telephone side and the case where the low-pass filter device of the present invention is mounted. By doing so, it can be confirmed that the attenuation characteristics of the data signal have been improved.

In the measurement system shown in FIGS. 5A and 6A, the telephone A is not used, the telephones B and C are in use, and the data signal is oscillated from the modem to the central office. It is. FIGS. 5B and 6B show attenuation characteristics of the telephone A and the data signal in this case.

5 (b) and 6 (b), the case where the low-pass filter device of the present invention is not mounted on the telephone and the case where the low-pass filter device of the present invention is mounted is compared with the case where the low-pass filter device of the present invention is mounted. By doing so, it can be seen that the amount of data signal leaking into the telephone can be suppressed.

[0019]

As described above, as described above, the telephone line
In the case where data communication using the splitterless ADSL system and conventional voice communication are used simultaneously under the condition that a plurality of telephone lines exist on one line, the low-pass filter device of the present invention uses Thus, effects such as suppression of variation in the impedance value of the relative modem, improvement in attenuation of the data signal, and suppression of leakage of the data signal into the telephone can be obtained. As a result, simultaneous use of data communication using a splitterless ADSL system and conventional voice communication becomes possible.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a low-pass filter device for a telephone line according to the present invention.

FIG. 2 is a diagram showing a frequency response of an impedance value of a low-pass filter for telephone lines of the present invention at a terminating resistance of 600Ω.

FIG. 3 is a diagram showing an electronic circuit of a measurement system and attenuation characteristics of a data signal when the low-pass filter for telephone lines according to the embodiment of the present invention is not used. FIG. 3A is an electronic circuit diagram of a measurement system, and FIG. 3B is a diagram illustrating attenuation characteristics of a data signal.

FIG. 4 is a diagram showing an electronic circuit of a measurement system and an attenuation characteristic of a data signal when the telephone line low-pass filter according to the embodiment of the present invention is used. FIG. 4A is an electronic circuit diagram of a measurement system, and FIG. 4B is a diagram illustrating attenuation characteristics of a data signal.

FIG. 5 is a view showing an electronic circuit of a measurement system, a telephone A, and an attenuation characteristic of a data signal when the telephone line low-pass filter according to the embodiment of the invention is not used. FIG. 5A is an electronic circuit diagram of a measurement system, and FIG. 5B is a diagram illustrating attenuation characteristics of a data signal.

FIG. 6 shows an electronic circuit of a measurement system and a telephone A when the low-pass filter for telephone lines according to the embodiment of the present invention is used.
FIG. 7 is a diagram illustrating attenuation characteristics of data signals. FIG. 6A is an electronic circuit diagram of a measurement system, and FIG. 6B is a diagram illustrating an attenuation characteristic of a data signal.

[Explanation of symbols]

 L inductor C capacitor

Claims (3)

[Claims] 1. A low-pass filter circuit for a telephone line, comprising: two inductors electrically inserted between a telephone line port and a telephone; and a capacitor inserted in series with the two inductors. 2. The low-pass filter circuit for a telephone line according to claim 1, wherein only the audio signal of the data signal and the audio signal transmitted through the telephone line is passed. 3. A low-pass filter device for telephone lines using the low-pass filter circuit for telephone lines according to claim 1.