JPH01303846A - Hands-free telephone set - Google Patents

Abstract

PURPOSE:To prevent singing from being generated by being equipped with a singing identifying means, which identifies a normal voice from the voice at the time of the singing generation, and prevents the generation of the singing with dropping the gain of a receiving amplifier at once at the time of the singing generation. CONSTITUTION:Singing identifying means 35 to 38 to identify the normal sound signal from a singing signal, and an AC amplifier 25 to make variable the gain due to a control signal from the singing identifying means 35-38 are provided. The normal voice of the output of a transmitting microphone 21 is identified from the voice at the time of the singing generation by the singing identifying means 35-38, and the gain of the AC amplifier 25 is controlled so as to be dropped at once at the time of the singing generation. Thus, the singing generation can be prevented, and simultaneously, communication is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a hands-free telephone that is designed to prevent the hands-free telephone from ringing.

[Conventional technology]

FIG. 3 is a block diagram showing a conventional hands-free telephone. In the figure, 21 is a transmitting microphone (hereinafter referred to as a transmitting microphone), 22 is a preamplifier, and 23 is a switch that is turned ON10 FF under the control of the sequential control circuit 34. ,2
4 is a transmitting AC amplifier that amplifies the audio signal to an appropriate level; 25 is a receiving AC amplifier that amplifies the input signal from the telephone line;
N10 FF switch, 27 is speaker amplifier,
28 is a speaker that emits sound; 29 is a comparator 3 that receives the received voice signal and outputs it after filtering;
2, a receiving signal processing circuit compares the threshold level and determines whether there is a syllabic signal;
numeral 31 is a comparator, and 34 is a transmitting signal processing circuit that outputs whether or not there is a syllable signal input to the transmitting section; The control circuit 33 is a speech network that converts two lines of the telephone line into four lines.

Next, the operation will be explained. The voice input converted by the transmitting microphone 21 is amplified by the preamplifier 22,
The audio signal is converted to an appropriate audio level by the AC amplifier 24 via the switch 23, and sent out to the telephone line via the speech network 33.

Conversely, the voice input from the other party is sent via the telephone line to the speech network 33. AC amplifier 25° switch 26. Speaker amplifier 27. It is output as audio through the speaker 28.

On the other hand, the output of the preamplifier 22 is filtered by the transmitting signal processing circuit 30, the threshold levels are compared by the comparator 31, and the result of whether or not there is a syllabic signal input is sequentially output to the control circuit 34.

Similarly, the reception signal processing circuit 29 performs filter processing, the comparator 32 compares threshold levels, and the result of whether or not there is a syllabic signal input to the AC amplifier 25 for reception is sequentially output to the control circuit 34. .

The sequential control circuit 34 closes the switch 23 when there is a syllabic signal on the transmitter and closes the switch 26 when there is a syllabic signal on the receiver.

If there is a signal on both, only one of the switches 23, 28 will close based on a predetermined priority.

That is, when both switches 23 and 26 are closed simultaneously, a closed loop is formed by the acoustic coupling from the speaker 28 to the transmitting microphone 21 and the leakage of the speech network 33, and when the loop gain exceeds a certain level, a sound is generated. . In order to prevent this problem, either the switch 23 or the switch 26 is always left open to prevent the formation of a closed loop and prevent the generation of noise.

[Problem to be solved by the invention]

Conventional hands-free telephones are configured as described above, so it is not possible to receive a call while the call is being sent, and the response time required to switch the switch 23 or 26 cannot be ignored in practical terms, making it difficult to have a natural conversation. There were problems such as interference.

This invention has been made to solve the above-mentioned problems, and aims to provide a hands-free telephone that can prevent ringing and simultaneously transmit and receive calls.

[Means to solve the problem]

The hands-free telephone according to the present invention is provided with a ringing discrimination means for distinguishing between a normal voice signal and a ringing signal, and an AC amplifier whose gain is varied by a control signal from the ringing discrimination means.

(Function) The sound identification means of the present invention distinguishes between normal voice and sound at the time of sound generation from the output of the transmitting microphone, and when the sound occurs, the gain of the AC amplifier is controlled to temporarily lower the gain and the sound is emitted. Preventing sound generation.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
In the figure, 35 is a rectifier attached to the output of the preamplifier 22, and its output signal is converted into a DC signal by an integrator 36. 37 is a differentiating circuit that detects the amount of variation in the output of the integrator 36; 38 is a differentiating circuit that monitors the amount of variation in the integrator 36 detected by the differentiating circuit 37, and reduces the gain of the AC amplifier 25 when the amount of variation in the integrator 36 is detected by the differentiating circuit 37; It is a comparator.

That is, rectifier 35. Integrator 36. Differential circuit 37. The comparator 38 constitutes a sound identifying means.

Note that in FIG. 1, the switches 23 and 23 shown in FIG.
26, comparators 31, 32, transmitting signal processing circuit 30
, the sequential control signal 34 is omitted. The other configurations are the same as in FIG. 3.

Next, the operation will be explained. In general, human voice signals are alternating current signals with irregular amplitude and period, as shown in Figure 2 (a), whereas ringing is an oscillation phenomenon in a closed loop, so Figure 2 (b) As shown in the figure, the waveform is close to a sine wave, and the amplitude and period are both more regular than human voice signals.

Therefore, as shown in FIG. 1, after half-wave rectification of the AC signal from the preamplifier 22 by the rectifier 35,
When the voltage is converted into a DC potential by the differentiating circuit 37 and the variation in the potential is detected by the differentiating circuit 37, the output of the differentiating circuit 37 decreases significantly because the amplitude and period of the ringing sound have little variation as described above.

This is detected by the comparator 38, and the AC amplifier 2
If the gain of 5 is lowered, the generation of noise can be prevented.

Further, in this case, since the gain of the AC amplifier 25 is only lowered, the receiving and transmitting paths are not cut off by the switches 23 and 26 as shown in FIG. 3, so that the transmitting and receiving signals can be transmitted and received at the same time.

(Effects of the Invention) As described above, according to the present invention, the sound discriminating means distinguishes the normal sound output from the transmitting microphone from the sound at the time of sound generation, and the gain of the AC amplifier when the sound occurs. Since the device is configured to be controlled so as to lower the noise level all at once, it is possible to prevent the occurrence of ringing noise and also to be able to transmit and receive calls at the same time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a hands-free telephone according to an embodiment of the present invention, FIG. 2(a) is a waveform diagram of an audio signal for explaining the operation of the above embodiment, and FIG. 2(b) is a diagram of the same embodiment as above. FIG. 3 is a block diagram of a conventional hands-free telephone. 21 is a transmitting microphone, 22 is a preamplifier, 24 is an AC amplifier for transmitting, 25 is an AC amplifier for receiving, 28 is a speaker, 33 is a speech network, 35 is a rectifier, 36 is an integrator, 37 is a differentiation circuit, 38 is a comparator, and 35 to 38 are sound identification means. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Patent applicant Mitsubishi Electric Co., Ltd. Agent Patent attorney 1) Hiroshi Sawa (2 others) OJ Figure 3

Claims (1)

[Claims] A transmitter microphone that converts voice into a telephone signal, a preamplifier that amplifies the telephone signal converted by the transmitter microphone, and a transmitter that maintains an appropriate transmitting level for transmitting the telephone signal to the telephone line via a speech network. AC for
an AC amplifier for receiving calls that amplifies the voice signal from the telephone line via the speech network;
A speaker that converts the audio signal amplified by the AC amplifier into audio, and a speaker that distinguishes between normal audio and audio at the time of sound generation from the output of the preamplifier and the A for receiving the call when the sound occurs.
This hands-free telephone is equipped with a ringing identification means for preventing the generation of ringing by temporarily lowering the gain of a C amplifier.