JPH0774710A - Audio line input circuit - Google Patents

Abstract

PURPOSE:To prevent production of unpleasant noise due to external noise by detecting it that a line input section is not connected to an external side so as to bypass the external noise picked up by a signal line. CONSTITUTION:When a line input section 1 is not connected to an external side, a connection detection section 6 detects it that the line input section 1 is not connected to the external side to provide an output of a detection signal 3. Thus, a noise path section 5 bypasses an external noise 22 picked up by a signal line between the line input section 1 and an amplifier section 2 to prevent the noise from being received by the amplifier section 2. Since no signal is inputted from the amplifier section 2 to a voice signal processing section 3, no output is produced from a voice output section 4 and then the output section 4 does not generate undesired noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio line input circuit, and more particularly to a means for removing external noise superimposed on an analog signal input from the outside.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing an example of a conventional audio line input circuit.

A conventional audio line input circuit is shown in FIG.
As shown in, the line input unit 11 for inputting an analog signal from the outside and the analog signal 3 from the line input unit 11
Amplifier unit 12 that amplifies 1 and outputs an analog signal 34
And an audio signal processing unit 13 which inputs the analog signal 34 and processes the signal to output an audio signal 35, and an audio output unit 14 which inputs the audio signal 35 and outputs an audio.

The operation of the conventional audio line input circuit configured as described above is such that when the line input section 11 is connected to the outside, the analog signal 31 from the line input section 11 is amplified by the amplifier section 12. Signal 3
4 is input to the audio signal processing unit 13, and the audio signal processing unit 13
In (1), voice processing is performed and the voice is output from the voice output unit 14.

When the line input section 11 is not connected to the outside, there is no analog signal output from the line input section 11, so the input of the amplifier section 12 is in the open state, and the line input section 11 and the amplifier section 12 are connected to each other. A small amount of extraneous noise 32 rides on the signal line between the two, is amplified by the amplifier unit 12, and is output as noise from the voice output unit 14 via the voice signal processing unit 13.

[0006]

As described above, in the conventional audio line input circuit, when the line input section is not connected to the outside, a minute line on the signal line between the line input section and the amplifier section is provided. Since the external noise is output as noise from the voice output unit, it has a drawback that annoying noise is generated.

[0007]

A first audio line input circuit of the present invention comprises a line input section for inputting an analog signal from the outside, an amplifier section for amplifying an analog signal from the line input section, and the line. Bypasses external noise captured by a signal line between the line input section and the amplifier section by a connection detection section that detects the input section when it is not connected to the outside and a detection signal from the connection detection section. And a noise bypass section for

A second audio line input circuit according to the present invention includes a line input section having a connection detecting section for inputting an analog signal from the outside and detecting the analog signal when it is not connected to the outside, and the line input section from the line input section. An amplifier unit that amplifies the analog signal and a noise bypass unit that bypasses external noise captured by a signal line between the line input unit and the amplifier unit by a detection signal from the connection detection unit are provided.

A third audio line input circuit of the present invention comprises a line input section for inputting an analog signal from the outside,
When the line input unit is not connected to the outside, a connection detection unit that detects it, and an external noise captured by a signal line between the line input unit and the amplifier unit by a detection signal from the connection detection unit, And an amplifier unit that amplifies the analog signal from the line input unit when the line input unit is bypassed and the line input unit is connected to the outside.

[0010]

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

FIG. 1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, the line input section 1 inputs an analog signal from the outside and outputs an analog signal 21. The connection detection unit 6 detects the connection state of the line input unit 1, and when the line input unit 1 is not connected to the outside,
The detection signal 23 is output. The noise bypass section 5 is connected in series between the line input section 1 and the amplifier section 2, and when the detection signal 23 from the connection detection section 6 is input,
The external noise 22 captured by the signal line between the line input section 1 and the amplifier section 2 is bypassed. The amplifier section 2 amplifies the analog signal 21 from the line input section 1 and outputs an analog signal 24. The audio signal processing unit 3 inputs the analog signal 24, processes the signal, and outputs an audio signal 25. The voice output unit 4 inputs the voice signal 25 and outputs a voice.

Next, the operation of the audio line input circuit configured as described above will be described.

When the line input section 1 is connected to the outside, the connection detecting section 6 detects that the line input section 1 is connected to the outside and does not output the detection signal 3. Therefore, the noise bypass section 5 transmits the analog signal 21 from the line input section 1 to the amplifier section 2, and the amplifier section 2 amplifies it and sends it to the audio signal processing section 3 as an analog signal 24. The audio signal processing unit 3 performs the audio processing and sends the audio signal 25 to the audio output unit 4, and the audio output unit 4 outputs the audio from the audio signal 25.

When the line input section 1 is not connected to the outside, the connection detecting section 6 detects that the line input section 1 is not connected to the outside and outputs the detection signal 3. Therefore, the noise bypass section 5 bypasses the external noise 22 captured by the signal line between the line input section 1 and the amplifier section 2 and prevents it from being input to the amplifier section 2. Therefore, since the audio signal processing unit 3 does not input any signal from the amplifier unit 2, there is no output to the audio output unit 4, and the audio output unit 4 does not generate unnecessary noise.

In the above-mentioned embodiment, the connection detecting section may be included in the line input section.
Also, the noise bypass section may be included in the amplifier section.

[0017]

As described above, the audio line input circuit according to the present invention has a connection detecting section for detecting that the line input section is not connected to the outside, and a line input section according to a signal from the connection detecting section. By providing a noise bypass section that bypasses the external noise captured by the signal line between the amplifier and the amplifier section, when the line input section is not connected to the outside, annoying noise due to minute external noise on the signal line There is an effect that it is possible to prevent the occurrence.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a conventional audio line input circuit.

[Explanation of symbols]

 1 ・ 11 Line input section 2 ・ 12 Amplifier section 3 ・ 13 Audio signal processing section 4 ・ 14 Audio output section 5 Noise bypass section 6 Connection detection section 21 ・ 31 Analog signal 22 ・ 32 External noise 23 Detection signal 24 ・ 34 Analog signal 25.35 audio signal

Claims (3)

[Claims] 1. A line input section for inputting an analog signal from the outside, a connection detection section for detecting the line input section when the line input section is not connected to the outside, and an analog signal from the line input section. An audio line input circuit comprising: an amplifier section; and a noise bypass section that bypasses external noise captured by a signal line between the line input section and the amplifier section by a detection signal from the connection detection section. . 2. A line input section for inputting an analog signal from the outside, which has a connection detecting section for detecting it when not connected to the outside, and an amplifier section for amplifying the analog signal from the line input section. An audio line input circuit comprising: a noise bypass unit that bypasses external noise captured by a signal line between the line input unit and the amplifier unit according to a detection signal from the connection detection unit. 3. A line input section for inputting an analog signal from the outside, a connection detecting section for detecting the line input section when the line input section is not connected to the outside, and the line according to a detection signal from the connection detecting section. The amplifier unit for bypassing external noise captured by the signal line between the input unit and the amplifier unit and amplifying the analog signal from the line input unit when the line input unit is connected to the outside. An audio line input circuit characterized by.