JPH06252796A - Cordless telephone set - Google Patents

Abstract

PURPOSE:To secure a clear voice while suppressing noises of an output signal. CONSTITUTION:A signal received by an antenna 1 is subjected to prescribed signal processing and the processed signal is given to a demodulator 11, in which a voice signal is demodulated and a voice signal from the demodulator 11 is sent to a squelch circuit 12 and a variable filter 13. Then the squelch circuit 12 converts the voice signal into an electric signal and impresses the signal to switches SW1, SW2 being components of the variable filter 13 as a noise squelch level and the switches SW1, SW2 are turned on when the noise squelch level is a prescribed level or over and the switches SW1, SW2 are turned off when the noise squelch level is a prescribed level or below. Thus, the switches SW1, SW2 are turned off when a voice signal of the variable filter 13 is larger and a frequency band of the voice signal from a demodulator 11 is set higher with the frequency pass band set to be nearly 3kHz, the output voice signal is made clear and when the voice signal is smaller, the switches SW1, SW2 are turned on the frequency pass band is set lower, and the frequency band of the voice signal from the demodulator 11 gets lower and noise at the output is suppressed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to cordless telephones.

[0002]

2. Description of the Related Art Conventionally, a cordless telephone handset extracts a voice signal from a signal received from a base unit, applies a low pass filter to the voice signal, cuts the voice signal near the high frequency side 3 kHz of a voice frequency band, and then uses a speaker or the like. It was outputting.

[0003]

However, in the above-mentioned conventional apparatus, when the signal received from the parent device is small, noise is generated in the high frequency side of the audio frequency band when the audio signal is taken out. Since this noise is generated at less than 3 kHz, it cannot be cut by the low-pass filter, and when it is output from a speaker or the like, there is a problem that the noise is severe and the voice is hard to hear.

Further, if the pass band of the low-pass filter is lowered in order to solve the above-mentioned problem, there is a problem that clear voice cannot be secured in normal times and it becomes difficult to hear.

An object of the present invention is to provide a cordless telephone in which noise is not generated even when the signal received from the master unit is small and a clear voice can be secured in normal time.

[0006]

In a cordless telephone having a master unit connected to a telephone line and a slave unit wirelessly connected to the master unit, the slave unit detects the strength of a signal received from the master unit. And a control means for varying the pass band of the received signal based on the detection result from the detection means.

[0007]

Therefore, when the signal received from the master unit is large, the detection means detects that the received signal is strong, and accordingly, the control means sets the pass band of the received signal to be high. When the signal received from the parent device is small, the detection unit detects that the received signal is weak, and accordingly, the control unit sets the pass band of the received signal to be low.

That is, when the signal received from the parent device is large, noise does not occur. Therefore, the pass band of the signal is set high to ensure clear voice at the time of output, and the signal received from the parent device is small. In this case, since noise is generated, it is possible to suppress the generation of noise at the time of output by setting the pass band of the signal low.

[0009]

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

FIG. 1 is a block diagram showing an outline of a cordless telephone handset which is an embodiment of the present invention, and FIG. 2 is a block diagram showing an outline of a cordless telephone base unit which is an embodiment of the present invention. 3 is a circuit diagram of the variable filter in FIG.

1 to 3, 1 is an antenna for receiving a signal transmitted from a base unit, 2 is a filter circuit for passing a specific frequency of the signal received by the antenna 1, and 3 is received by the antenna 1. The first local oscillator 4 generates a variable frequency for converting the generated signal to the first intermediate frequency, and the first local oscillator 3 receives the signal from the filter circuit 2.
First variable frequency conversion from the first to intermediate frequency conversion
Mixer, 5 is a filter that passes the first intermediate frequency, 6 is the first
It is a first intermediate amplifier that performs selective amplification of an intermediate frequency.

Reference numeral 7 is a second local oscillator for generating a fixed frequency for converting the first intermediate frequency into the second intermediate frequency, and 8
Is a second mixer for converting the intermediate frequency from the first intermediate amplifier 6 into a second intermediate frequency by the fixed frequency from the second local oscillator 7, 9 is a filter for passing the second intermediate frequency, and 10 is a second intermediate frequency. The second intermediate amplifier performs selective amplification.

Reference numeral 11 is a demodulator which extracts a voice signal from the second intermediate frequency from the second intermediate amplifier, and 12 is a squelch circuit which converts the voice signal extracted by the demodulator 11 into an electric signal and sends it out as a noise squelch level. Yes,
The noise squelch level is inversely proportional to the audio signal, such as Low when the audio signal is large and High when the audio signal is small. 1
Reference numeral 3 is a variable filter that allows the audio signal from the demodulator 11 to pass through. As shown in FIG.
1 and R2, capacitors C1, C2, C3 and C4, and switches SW1 and SW2 that are turned on and off according to the noise squelch level from the squelch circuit 12, and the frequency pass band has resistors R1 and R2 and capacitors C1 and C2. , C3, C4.

Reference numeral 14 is a low frequency amplifier that amplifies the audio signal from the variable filter 13 to a signal level sufficient to drive the speaker 15.

Reference numeral 21 denotes an antenna for transmitting a signal to the child device, 2
Reference numeral 2 denotes a wireless unit that transmits and receives signals to and from the slave unit, and 23 decompresses the signal received by the wireless unit 22 and sends the signal to the speaker 24 or the telephone line, and at the same time compresses the signal from the microphone 25 or the telephone line to the wireless unit. A call unit for sending to 22; a control unit for controlling the entire system; and a key operation unit for performing various operations.

The squelch circuit 12 includes a detection means and a control means.

Next, the reception operation of the slave unit having the above configuration will be described. The signal transmitted from the antenna 21 of the master unit is received by the antenna 1 of the slave unit and sent to the filter circuit 2. Here, the received signal passes through only a specific frequency and is sent to the first mixer 4, and is converted into the first intermediate frequency by the variable frequency from the first local oscillator 3 in the first mixer 4, and then the filter 5 Is sent to the first intermediate amplifier 6 and is selectively amplified here.

Then, the first intermediate frequency thus selectively amplified is converted into the second intermediate frequency by the fixed frequency from the second local oscillator 7 in the second mixer 8, and then the second intermediate amplifier via the filter 9. It is sent to 10, where it is selectively amplified. The second intermediate frequency thus selectively amplified is demodulated by the demodulator 11
To the squelch circuit 12 and the variable filter 13 after being demodulated into an audio signal.

The squelch circuit 12 converts this audio signal into an electric signal and applies it as a noise squelch level to the switches SW1 and SW2 constituting the variable filter 13. The switches SW1 and SW2 are turned on when the applied noise squelch level is equal to or higher than a predetermined level, and are turned off otherwise. Therefore, the frequency pass band of the variable filter 13 is set to about 3 kHz by the resistors R1 and R2 and the capacitors C1 and C2 when on, and the resistors R1 and R2 and the capacitors C1, C2, C3 and C when off.
4 and the capacitors C3 and C4 are connected in parallel to the capacitors C1 and C2, so that they are set lower than 3 kHz.

On the other hand, the audio signal sent to the variable filter 13 passes only a specific frequency here. At this time, if the audio signal has reached a predetermined value, the noise squelch level is below the predetermined level, so that the switches SW1 and SW2 forming the variable filter 13 are turned off and the audio frequency band is cut near the high frequency side 3 kHz, If the audio signal has not reached the predetermined level, the noise squelch level is higher than the predetermined level, so that the switches SW1 and SW2 forming the variable filter 13 are turned on, and the audio frequency band is cut off at a frequency lower than 3 kHz.

The audio signal passed through the variable filter 13 is amplified to a predetermined level by the low frequency amplifier 15 and then output from the speaker 16.

In this embodiment, the received signal is modulated into a voice signal, and then the voice signal is converted into an electric signal and controlled as a noise squelch level. However, the received signal is converted into an electric signal and the noise squelch is converted. You may control as a level.

[0023]

As described above, according to the present invention, when the signal from the master unit is a small signal in which noise is generated, the frequency pass band of the variable filter can be set low to suppress the generation of noise. When a large signal without noise is generated, a clear voice can be secured by setting the frequency pass band of the variable filter high.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a slave unit of a cordless telephone which is an embodiment of the present invention.

FIG. 2 is a block diagram showing an outline of a base unit of a cordless telephone which is an embodiment of the present invention.

FIG. 3 is a circuit diagram of a variable filter in FIG.

[Explanation of symbols]

 1 Antenna 2 Filter Circuit 3 1st Local Oscillator 4 1st Mixer 5 Filter 6 1st Intermediate Amplifier 7 2nd Local Oscillator 8 2nd Mixer 9 Filter 10 2nd Local Oscillator 11 Demodulator 12 Squelch Circuit 13 Variable Filter 14 Low frequency amplifier 15 speaker

Claims (1)

[Claims] 1. A cordless telephone having a master unit connected to a telephone line and a slave unit wirelessly connected to the master unit, wherein the slave unit includes detection means for detecting the strength of a signal received from the master unit. A cordless telephone, which is provided with a control unit for varying a pass band of the received signal based on a detection result from the detection unit.