JP2001077649A - Low-pass filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-pass filter circuit for a telephone line free of the occurrence of tipping in a voice signal band. SOLUTION: In a low-pass filter circuit, consisting of plural inductors and plural capacitors, an inductor and a parallel circuit consisting of an inductor and a capacitor are connected serially, a capacitor C1 and C2 are connected in parallel, and switches S1 and S2 are connected serially to the respective parallel-connected capacitors C1 and C2. When a telephone set is in a speaking state, the switches S1 and S2 are connected, and when the telephone set is in a no speaking state, the switches S1 and S2 are disconnected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for connection between a telephone or an ADSL modem and a telephone line mainly used in a full-rate Asymmetric Digital Subscriber Line system (hereinafter referred to as a full-rate ADSL system). The present invention relates to a low-pass filter circuit for a telephone line.

[0002]

2. Description of the Related Art In conventional data communication using a telephone line, it has been impossible to transmit and receive a data signal and a voice signal at the same time. An ADSL system that performs the above has been developed and its practical application is under study.

[0003] Among these ADSL systems, a full-rate ADSL system is a Plain Old Telephone that mixes and distributes a data signal and a voice signal to a telephone station and a subscriber's house.
A frequency filter device called a service splitter (hereinafter, POTS splitter) is required.

As shown in FIG. 6, conventionally, when a plurality of telephones and an ADSL modem are connected in a general household, a telephone line is branched to each telephone and ADSL modem via one POTS splitter. You. A low-pass filter circuit 5 is provided in the POTS splitter.

FIG. 3 is a diagram showing a low-pass filter circuit included in a conventional POTS splitter. Configuration of the low-pass filter circuit includes an inductor and an inductor, though a capacitor parallel circuit is connected in series, and further, a configuration in which the capacitor C ₁ and C ₂ are connected in parallel.

[0006]

However, the conventional POT
Since the installation of the S splitter requires installation work by a specialized technician, it was necessary to request a telephone company. That is, it was difficult for the user to install the POTS splitter by himself.

After the telephone line is branched, the conventional POTS
When the splitter is inserted between each telephone line opening and the telephone, tipping occurs in the audio signal band as shown in FIG.

[0008] The tipping in this audio signal band is performed by PO
This occurs when a TS splitter is connected between a telephone line port and a plurality of telephones for each telephone. This is because the POTS connected to the phone
This is due to the resonance phenomenon of the inductors L ₁ and L ₂ and the capacitors C ₁ and C ₂ in the low-pass filter circuit in the splitter, which hinders the conventional telephone service.

Accordingly, an object of the present invention is to provide a low-pass filter circuit for a telephone line in which chipping does not occur in an audio signal band.

[0010]

Therefore, the low-pass filter circuit according to the present invention connects each capacitor connected in parallel to each other only in a telephone call, so that the capacitor works in series with each capacitor. Then, each switch is inserted.

By linking each of the switches with the telephone, each switch is closed only during telephone communication, and functions as a splitter. Further, when the telephone is not talking, each switch is in an open state, so that no capacitor is connected. As a result, no tipping occurs in the audio signal band.

As described above, by using the switch in the low-pass filter circuit, the connection state of the capacitor can be changed in accordance with the use condition of the telephone, and the low-pass filter circuit can function as the low-pass filter circuit only during telephone conversation. This allows you to split the phone line into multiple
A splitter can be connected between the telephone line port and the telephone, and a low-pass filter circuit for telephone lines that does not cause tipping in an audio signal band can be realized.

That is, the present invention relates to a low-pass filter circuit comprising a plurality of inductors and a plurality of capacitors, wherein the low-pass filter circuit has a configuration in which an inductor, a parallel circuit of an inductor and a capacitor are connected in series. On the other hand, a capacitor is connected in parallel connection, and each capacitor connected in parallel is a low-pass filter circuit in which a switch is connected in series.

Further, according to the present invention, when the low-pass filter circuit is inserted between a telephone line port and a telephone, and the telephone is in a talking state, the switch is in a conductive state. This is a low-pass filter circuit that is turned off.

Further, the present invention is the low-pass filter circuit, wherein the switch is a photoelectric switch in the low-pass filter circuit.

Further, the present invention is a low-pass filter circuit in which the low-pass filter circuit is inserted between one telephone line and a plurality of telephones for each telephone.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A low pass filter circuit according to an embodiment of the present invention will be described below.

FIG. 1 shows a low-pass filter circuit according to the present invention. FIG. 1A shows a configuration of a low-pass filter circuit when the telephone is not used, and FIG. 1B shows a configuration of the low-pass filter circuit when the telephone is used.

The low-pass filter circuit shown in FIG. 1 (a), FIG. 1 (b), the capacitor _{C 1} and capacitor C
_2, in which the switch S ₁ and switch S ₂ has been inserted in series. Here, switch _{S 1} and the switch _{S 2} is,
It works in conjunction with a telephone.

That is, when the telephone is not used, the switch S ₁
Switch S ₂ is turned off, and at the time of phone used, switch S ₁ and switch S ₂ is such that the conduction state, to set the operation of each switch.

For example, the switch S₁And switch S₂Is
A photoelectric switch or the like is used. In this case, when using a telephone
Detects the line current level in the telephone
S₁, S ₂Are conducted.

[0022] Here, in the state of FIG. 1 (a), the switch _{S 1} and switch _{S 2} is a non-conducting state, the capacitor _C 1, _{C 2} is in the state of the filter circuit is not connected. Therefore, it does not function as a low-pass filter circuit.

Further, when the phone use, detects a line current or the like, using a photoelectric switch or the like, the switch S ₁ and switch S ₂ to a conductive state, functions as a low-pass filter circuit shown in FIG. 1 (b) I do. FIG. 2 shows the measurement results of the insertion loss characteristics in the audio signal band at this time. FIG.
It can be seen that no tipping is observed in the audio signal band.

As described above, when a full-rate ADSL system and a plurality of telephones are connected to a telephone line, the low-pass filter circuit of the present invention is inserted between the telephone line port and each telephone so that the audio signal band is tipped. Therefore, the high-speed data transmission service using the ADSL system and the conventional telephone service can be used simultaneously.

Further, the low-pass filter circuit of the present invention can be installed by the user himself and does not require any installation work by the telephone company, so that an effect of promoting the spread of the ADSL service can be expected.

[0026]

As described above, according to the present invention, it is possible to provide a telephone line low-pass filter circuit which does not cause chipping in an audio signal band.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a low-pass filter circuit according to an embodiment of the present invention. FIG. 1A is a diagram showing a low-pass filter circuit when switches S ₁ and S ₂ are in a non-conductive state.
(B) is a diagram showing a low-pass filter circuit when the switch S ₁ and S ₂ is conductive.

FIG. 2 is a diagram showing insertion loss characteristics in an audio signal band when the low-pass filter circuit of the present invention is inserted between a telephone line port and a telephone.

FIG. 3 is an explanatory diagram of a low-pass filter circuit in a conventional POTS splitter.

FIG. 4 is a diagram showing insertion loss characteristics in an audio signal band when a conventional low-pass filter circuit is inserted between a telephone line port and a telephone.

FIG. 5 is a diagram showing a method for connecting a low-pass filter circuit of the present invention to a telephone.

FIG. 6 is a diagram showing a method for connecting a conventional low-pass filter circuit to a telephone.

[Explanation of symbols]

 1,2,3,4,5 Low pass filter circuit 10,11 Telephone line

Claims (4)

[Claims] 1. A low-pass filter circuit comprising a plurality of inductors and a plurality of capacitors, wherein the low-pass filter circuit has a configuration in which an inductor, a parallel circuit of an inductor and a capacitor are connected in series,
It is a configuration in which a capacitor is connected in parallel connection,
A low-pass filter circuit, wherein a switch is connected in series to each of the capacitors connected in parallel. 2. The low-pass filter circuit according to claim 1, which is inserted between a telephone line port and a telephone. When the telephone is in a talking state, the switch is in a conductive state, and when the telephone is in a non-talking state, the switch is in a non-talking state. Is a low-pass filter circuit that is in a non-conductive state. 3. The low-pass filter circuit according to claim 1, wherein said switch is a photoelectric switch. 4. The low-pass filter circuit according to claim 1, wherein the low-pass filter circuit is inserted between one telephone line and a plurality of telephones for each of the telephones. Filter circuit.