JPH0533865B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hands-free telephone communication device that is a telephone that uses a microphone and a speaker instead of a handset.

[Conventional technology]

Conventionally, in this type of hands-free communication device, howling occurs due to acoustic coupling between a speaker and a microphone, and various methods have been used to prevent howling.

Generally, howling has been prevented by lowering the microphone level (volume) with a fixed gain when receiving a call, and by lowering the speaker level (volume) when transmitting a call. Furthermore, when the user was transmitting and receiving calls at the same time, and when neither transmitting nor receiving calls, the state was the same as when receiving a call.

[Problem that the invention seeks to solve]

The above-mentioned conventional hands-free communication device is in a receiving state when neither transmitting nor receiving calls, and when starting to transmit, raises the microphone level and lowers the speaker level. The drawback is that the sound quality at the beginning of a conversation is poor.

In addition, since the volume level from the speaker is not directly detected by the microphone, as a measure to prevent howling, the level (volume) of the microphone or speaker must be lowered with a certain gain in advance, regardless of the installation position of the microphone or speaker. There is. Therefore, there is a drawback that the installation positions of the microphone and speaker must be determined in advance.

An object of the present invention is to provide a hands-free telephone device that can adjust the microphone level of a hands-free telephone and, in particular, detects the surrounding sound volume and always maintains an optimal volume without causing howling.

[Means for solving problems]

The hands-free telephone device of the present invention is a hands-free telephone device which is equipped with a speaker in a receiver circuit and a microphone in a transmitter circuit instead of a handset of a telephone set. an adder for adding the amplified inaudible signal to the audio signal of the receiving circuit; and means for detecting the level of the inaudible signal in the audio signal of the transmitting circuit. , means for attenuating the audio signal of the transmitting circuit in proportion to the level of the detected inaudible signal.

[Effect]

Therefore, according to the present invention, it is possible to control the amplification of the inaudible signal depending on the level of the incoming audio signal, and to control the attenuation of the outgoing audio signal depending on the level of the inaudible signal. .

〔Example〕

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

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

As shown in FIG. 1, the hands-free communication device includes a receiving circuit Rv and a transmitting circuit Tm.
The receiver circuit Rv is sequentially connected in series with a receiver 1, an amplifier 2, an audible range (300Hz to 3KHz) band filter 3, and an amplifier 4, and is also connected to an analog adder 5. The branch output of the bandpass filter 3 is connected to a variable amplifier 10 connected to an oscillator 9 with an inaudible frequency (30KHz) via an analog-to-digital converter 7 and a processing unit 8 such as a CPU. The output of the variable amplifier 10 is connected to an analog adder 5, and the output of the adder 10 is connected to a wideband speaker 6 for receiving calls.

The transmission circuit Tm is connected in series with a highly sensitive microphone 11 for transmission, an amplifier 12, a 300Hz to 3KHz band filter 13, and a variable attenuator 14, while the branch outputs of the amplifier 12 are connected in series. High gain 30KHz bandpass filter 17, amplifier 1
8. Connected to an analog-to-digital converter 19 and a processing unit 16 such as a CPU, the output of the processing unit 16 is connected to a variable attenuator 14, and the output of the variable attenuator 14 is connected to a transmitter 15. has been done.

Next, the operation shown in FIG. 1 will be explained. Receiving circuit Rv
Then, the signal input from the receiver 1 passes through the amplifier 2 and the bandpass filter 3 and is divided into two parts.
One is sent through an amplifier 4 to an analog adder 5, and the other is sent through a converter 7 to a processing unit 8 for signal level detection.

The processing unit 8 sends an amplification control signal rc to the variable amplifier 10 to amplify and control the inaudible signal f0, which is a sine wave signal of 30 KHz in the inaudible range, output from the oscillator 9. Here, the inaudible signal f0 amplified to a value proportional to the received audio signal level is sent to the analog adder 5 and added to the audio signal from the amplifier 4, and is output as audio from the high-band speaker 6. be done.

In the transmitter circuit Tm, a highly sensitive microphone 11
The input signal passes through the amplifier 12 and is divided into two parts, one of which is passed through the band filter 1 as an audio signal.
3 and is sent to the variable attenuator 14, and the other one passes through a 30KHz high gain bandpass filter 17 and an amplifier 18 to the converter 1 in order to detect the level of the inaudible signal f0.
Based on the signal from the converter 19, the processing unit 16 sends an attenuation control signal tc to the variable attenuator 14.

The audio signal from the bandpass filter 13 is attenuated to an appropriate value by a variable attenuator 14 and sent to a transmitter 15.

Here, to summarize the above-mentioned embodiment, this embodiment has the following:
The receiver circuit Rv side is equipped with an inaudible signal amplifying means Gn and an adder 5, and the transmitting circuit Tm side is equipped with an inaudible signal detecting means Dt and a variable attenuator 1.
4, a sound wave of an inaudible signal f0 having a frequency in the inaudible range is added to the receiving audio signal to make the speaker 6 sound, and surrounding sounds are collected by the transmitting microphone 11, and the inaudible signal f0 is added to the receiving audio signal. By sensing only the sound wave level, the variable attenuator 14 is controlled and the microphone level is adjusted.

〔Effect of the invention〕

As explained above, the present invention adds a signal in the inaudible range to the voice received from the speaker, thereby making it possible to distinguish between voice signals from different sources, the voice from the caller and the voice from the speaker.
This has the effect of effectively preventing howling. In addition, when neither transmitting nor receiving calls, the microphone has the best sensitivity to the extent that it does not cause howling, which has the effect of maintaining the best volume at the beginning of a conversation.

Furthermore, there is an effect that a certain degree of freedom can be obtained in the placement locations of the speakers and microphones.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. 1... Receiver, 2, 4, 12, 18... Amplifier, 3, 13... Bandpass filter, 5... Analog adder, 6... Broadband speaker, 7, 19...
Converter, 8, 16...processing unit, 9...oscillator, 10...variable amplifier, 11...high sensitivity microphone, 14...variable attenuator, 15...transmitter, 17...high gain band filter.

Claims (1)

[Scope of Claims] 1. A receiving unit that converts a received signal from a communication line into an audio signal, an oscillator that receives the audio signal and generates an inaudible signal, and a receiver that converts the inaudible signal according to the level of the audio signal. a variable amplifier that amplifies the amplified inaudible signal, an adder that adds the amplified inaudible signal to the audio signal, and a speaker that outputs the added signal; a microphone that collects the inaudible signal; a bandpass filter that detects the inaudible signal from the collected signal;
1. A hands-free communication device, comprising: a transmitter section including a variable attenuator that attenuates the transmitted voice according to the level of the detected inaudible signal.