JPH09200320A - Cordless telephone set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speak in a natural state without newly adding any circuit such as an echo canceler for preventing a sidetone from being heard. SOLUTION: An audio signal inputted from a microphone 401 of a cordless telephone set (hand set) is transmitted through a compressor 404, scramble 405 and RF module 408 to a base unit, and the sidetone returned from a subscriber's line is received by the RF module 408, passed through a descramble 406 and an expander 407 and reproduced from a speaker 402. On the other hand, the audio signal outputted from the compressor 404 is suitably amplified by an attenuator 410 and outputted to the speaker 402. As a result, since the sidetone practically having no delay time is heard from the speaker 402, the delayed and returned sidetone can be ignored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cordless telephone set, and more particularly to a low power cordless telephone set connected to an outside line via a master unit.

[0002]

2. Description of the Related Art A block diagram of a cordless telephone system is shown in FIG.
Shown in This system is used by fixing it on a desk or the like and has a function similar to a dedicated wired telephone (107 to 1).
10) and connecting devices (103 to 106) corresponding to the master unit
The main device (102) that accommodates the

The sidetone is the voice returned from the outside line of the voice transmitted from the cordless handset to the outside line, and the volume of this sidetone is adjusted by the line interface part in the main unit so as to be an appropriate volume. Is designed.

FIG. 2 shows a simple block diagram of the voice flow of the cordless telephone system of FIG. Hereinafter, the flow of sidetones during a call with an outside line will be described.

Microphone (20) of a handset (cordless telephone)
The voice input to 1) is scrambled in the signal processing IC (203) to have confidentiality with a compressor (204) that compresses the level fluctuation of the voice signal in order to increase the S / N ratio of the voice signal. The signal is processed in (205) and then output to the RF module (208). The audio signal is
It is FM-modulated by the RF module and transmitted to the connection device as a radio wave through the antenna (209).

The connection device receives the radio wave transmitted from the slave unit by the antenna (210), and the RF module (211).
After demodulating into an audio signal by, the signal is output to the signal processing IC (212). The signal processing IC performs signal processing such as descrambling (213) for deciphering the secret and expander (214) for expanding the compressed level fluctuation to the original level fluctuation and outputs it to the main device. The audio signal sent to the main unit is output to the line via the line interface (217).

The voice signal returned from the line as a side tone is output to the connection device through the line interface of the main device. The connection device performs signal processing such as compressor (216) and scramble (215) on the audio signal by the signal processing IC, FM-modulates by the RF module, and then transmits to the slave unit.

The slave unit demodulates the received radio wave into an audio signal, then performs signal processing such as descrambling (206) and expander (207) in the signal processing IC, and outputs it to the receiver (202).

As a result, the voice input to the microphone is output to the line through signal processing such as compressor → scramble → FM modulation → FM demodulation → descramble → expander, and the voice returned from the line as sidetone is The signal is again output from the receiver of the slave unit through signal processing such as compressor → scramble → FM modulation → FM demodulation → descramble → expander.

The sidetone of the cordless telephone of the system shown in FIG. 1 is heard from the receiver of the handset through the above route.

[0011]

In the low power cordless telephone, the voice input to the microphone passes through various signal processing circuits before returning as a side tone as in the conventional example.

[0012] These are signal processes generally performed to improve the S / N ratio of voice and provide confidentiality.

However, particularly when the voice passes through a signal processing circuit such as a compressor or an expander, the output voice is delayed by several ms to tens of ms with respect to the input voice. When such signal processing is performed, it becomes impossible to eliminate the delay although there is a degree of difference. In addition, signal processing such as scrambling and descrambling also causes delay in voice.

Even if the voice of the transmitted voice is transmitted to the other party with a delay of several ms to several tens of ms, the other party does not feel the actual voice at the same time, so it does not feel unnatural, but the side tone returns from the line. Since it is my own voice that comes in, my voice comes to be delayed, and it sounds like an echo to the user.

[0015]

DISCLOSURE OF THE INVENTION The present invention provides a cordless telephone which enables a telephone call in a natural state without adding a circuit such as an echo canceller so that a delayed side tone cannot be heard. Is what you are trying to do.

In order to solve this problem, the present invention has the following structure. That is, a low-power cordless telephone that uses a compander that compresses the level fluctuation of a voice signal at the time of transmission and expands so that the original level fluctuation is received at the time of reception. And a means for outputting the extracted audio signal to the receiver of the slave unit, and the voice input to the microphone of the slave unit while in a call state with the subscriber line is stored in the slave unit. Substantially no delay time is generated, but is generated as sidetone.

According to a preferred embodiment of the present invention,
It is preferable that the cordless telephone further comprises scramble means for scrambling the audio signal output from the compressor. This causes more delay time, and the effect of the present invention becomes remarkable.

Further, it is preferable that the output means includes an amplification means for amplifying the audio signal extracted by the extraction means.

As a result, it becomes possible to make the audible sound actually returned negligible.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 4 is a block diagram of the slave unit in the embodiment. The drawing is a block diagram of a cordless telephone slave unit used as an extension telephone in the cordless telephone system as shown in FIG. 1, and is applied to the block diagram of the cordless telephone device of FIG. That is, the configuration of the main device has not been changed.

In the following, the flow of the sidetone when the cordless handset of the embodiment has a line and a call state in the illustrated configuration will be described.

The voice input to the microphone (401) of the slave unit is stored in the signal processing IC (403) as a compressor (404) which compresses the level fluctuation of the voice signal in order to increase the S / N ratio of the voice signal. The signal is processed by the scramble (405) for giving confidentiality, and then the RF module (20
It is output to 8). The audio signal is FM by the RF module.
It is modulated and transmitted to the connection device by radio waves through the antenna (209).

The connection device receives the radio wave transmitted from the slave unit, demodulates it into a voice signal, and then descrambles the signal processing IC to decipher the secret signal and expands the compressed level fluctuation to the original level fluctuation. It performs signal processing such as and outputs it to the main unit. The audio signal sent to the main unit is output to the line via the line interface.

The voice signal returned from the line as a side tone is output to the connection device through the line interface of the main device. The connection device performs signal processing such as compressor and scramble on the audio signal by the signal processing IC, FM-modulates by the RF module, and then transmits to the slave unit.

The slave unit demodulates the received radio wave into an audio signal, then performs signal processing such as descrambling (406) and expander (407) in the signal processing IC, and outputs it to the receiver (402). The sidetone returning from the line is heard through the above route.

On the other hand, in the embodiment of the present invention, the sound input to the microphone of the slave unit as another side sound is taken out from the output section of the compressor, and the attenuator circuit (4
In step 10), the side tone to be adjusted to an appropriate amplitude and output to the receiver of the handset is added.

FIG. 5 shows how the sidetone actually sounds in the embodiment.

In the figure, reference numeral 501 represents an audio signal input to the microphone, and it is assumed that a certain signal is input to the microphone.

When such a voice is input during a call with the line, the side tone returned from the line is 50.
The waveform becomes as shown in Fig. 2 and is delayed with respect to the input voice. This time difference between 501 and 502 causes the sidetone to feel like an echo.

The waveform of reference numeral 503 is obtained by extracting the sound input to the microphone of the slave unit from the output section of the compressor 404,
It is the waveform of the attenuator output section after being input to the attenuator 410 and having its amplitude adjusted. This waveform is the same as the output waveform of the compressor in FIG. 3, and its amplitude is adjusted by the attenuator so that it becomes appropriate as a side tone.

Reference numeral 504 indicates a sidetone output to the receiver of the slave unit. This is the sum of the sidetone (502) returned from the line and the sidetone (503) generated inside the slave unit. The side tone coming back from the actual line
By generating the sidetone in the slave unit by the method as shown in FIG. 4 despite the delay, the sidetone is made natural without feeling the delay.

The attenuator 410 is the compressor 4
Since the voice extracted from 04 is sufficiently amplified as compared with the sidetone returned through the line, the human auditory sense does not make the audible noise through the line annoying.

As described above, according to the present embodiment, the low-power cordless telephone expands (expands) the voice signal level fluctuations at the time of transmission by compressing (compressing) the data and transmitting it to the original level fluctuations at the time of reception. In a cordless telephone system that performs signal processing such as
The problem that the side tone is delayed and returns when the line is in a call and sounds like an echo is that the sound input to the microphone of the cordless handset is extracted at the output of the compressor. Having it heard from the receiver has the effect of providing natural sidetones in an inexpensive way.

[0035]

As described above, according to the present invention, it is possible to talk in a natural state without adding a new circuit such as an echo canceller so that delayed sidetones cannot be heard. .

[0036]

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a cordless telephone system.

FIG. 2 is a diagram for explaining a flow of sidetone.

FIG. 3 is a diagram showing input / output waveforms of a compressor.

FIG. 4 is a block configuration diagram of a child device according to the embodiment.

FIG. 5 is a diagram showing side sounds and output waveforms of a compressor in the embodiment.

[Explanation of symbols]

 101 station line 102 main device 103-6 connecting device 107-110 slave device 201, 401 microphone 202, 402 receiver 203, 212, 403 signal processing IC 204, 216, 404 compressor 205, 215, 405 scramble 206, 213, 406 de Scramble 207, 214, 407 Expander 208, 211, 408 RF module 209, 210, 409 Antenna 217 Line interface 218 Subscriber line 410 Attenuator 501 Microphone input waveform 502 Sidetone from line 503 Sidetone 504 actually generated in slave unit 504 Actual Sidetone of

Claims (3)

[Claims] 1. A low-power cordless telephone using a compander that compresses a level fluctuation of a voice signal at the time of transmission and transmits the compressed signal so that the original level fluctuation is received at the time of reception, which is output from a compressor of a slave unit. And an output means for outputting the extracted audio signal to the receiver of the slave unit, and outputs the audio input to the microphone of the slave unit when in a call state with the subscriber line, A cordless telephone characterized in that a delay time is not substantially generated in a slave unit, and a side tone is generated. 2. The cordless telephone according to claim 1, further comprising scrambling means for scrambling the audio signal output from the compressor. 3. The cordless telephone according to claim 1, wherein the output means includes amplification means for amplifying the audio signal extracted by the extraction means.