JP3261012B2 - Hands-free telephone equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hands-free telephone device connected to a digital line or an analog line, and more particularly to the prevention of echo or howling.

[0002]

2. Description of the Related Art Conventionally, various types of telephone devices have been used, and among them, there is a hands-free telephone device that allows a user to talk without holding a handset. In particular, in a car phone, a driver often operates a steering wheel or the like while driving, so that this hands-free phone device is often employed.

Here, in a hands-free telephone device, since a relatively loud sound is output from a speaker, the sound goes around the microphone, and so-called howling tends to occur.

That is, in the case of a two-wire / four-wire conversion unit, especially in the case of a car telephone, when a connection is made from a car telephone line to a general public line, four lines are converted into two lines. , The signal is likely to be reflected, and by this reflection, the transmission signal input from the microphone wraps around the reception signal and is supplied to the speaker. Then, the output sound from the speaker is input to the microphone to form a loop. If the other party is also a hands-free telephone, a loop may be formed via both telephones.

In a hands-free telephone device connected to an analog line, the time delay in such a signal loop can be almost ignored, and the same signal is sequentially amplified and output, causing howling.

On the other hand, in a digital line, a time-division multiplexing (TDMA) system is used for communication, and A / D conversion, compression, demodulation, and D / A conversion are performed.
sec), and howling hardly occurs. However, when the transmission signal wraps around the reception signal due to reflection due to the time delay, the signal is output from the speaker with a predetermined time delay and recognized as an echo. In other words, there is a problem that since the voice of one's own voice is heard with a delay, it is very difficult to talk due to harshness, and the volume of the received voice overlaps with the received voice, making it difficult to hear the received voice.

[0007] In the case of a hands-free telephone device connected to an analog line, a howling canceller is used, which detects a communication state and attenuates an input signal (transmission signal) from a microphone other than during transmission by an attenuator. I have. According to this howling canceller, even if the output sound from the speaker goes around the microphone, the signal is not attenuated but attenuated, so that the occurrence of howling is prevented.

As described above, howling can be prevented in a hands-free telephone device connected to an analog line by using a howling canceller.

On the other hand, in a hands-free telephone device connected to a digital line, an echo canceller is used which detects a communication state and attenuates a signal (received signal) supplied to a speaker other than during a call by an attenuator.
Thereby, an unpleasant echo can be canceled.

[0010]

However, in the conventional hands-free telephone, there is no idea to secure the communication quality regardless of whether the telephone is connected to an analog line or a digital line. On the other hand, if a simple circuit can be added without using an expensive echo canceller and a connection can be made to both digital and analog devices, it is possible to supply a device that is highly versatile and low-cost.

There has been a demand for a hands-free telephone device capable of ensuring a sufficient communication quality even when connected to such a digital or analog line.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a hands-free telephone device that can secure a sufficient communication quality even when connected to a digital or analog line.

[0013]

SUMMARY OF THE INVENTION The present invention relates to a digital / analog hands-free telephone device which can be used when connected to either a digital line or an analog line, and attenuates the signal level of a received signal. A receiving-side attenuator (24) for guiding to a speaker, a transmitting-side attenuator (22) for attenuating a signal level of a transmission signal from a microphone, and a determination unit for determining whether a connected line is a digital line or an analog line. And control means for increasing at least the attenuation of the transmitting-side attenuator when the determination result of the determination means is a digital line, compared to when the determination result is an analog line. . In another aspect, when the determination result of the determination unit is a digital line, the attenuation of the reception-side attenuator and the transmission-side attenuator is made larger than when the determination result is an analog line.

The control means, when it is determined from the determination result by the determination means that the line to be connected is a digital line, performs a reception interrupt control for turning off the reception-side attenuator when a reception signal is input, and When it is determined that the line to be transmitted is an analog line, it is preferable to perform a transmission interruption control for turning on the receiving-side attenuator when a transmission signal is input. Further, the control means turns on the receiving-side attenuator at the time of transmission signal input and determines the time for which the receiving-attenuator is kept on when the connection line is determined to be a digital line based on the determination result by the determination unit. Performs transmission interruption control from the end of transmission to after a delay time.When it is determined that the connected line is an analog line, the receiver attenuator is turned on when a transmission signal is input, and the receiver attenuator is kept on. The transmission interruption time from the end of the transmission to the end of the delay time, and the discrimination means, when the discrimination result of the discrimination means is a digital line, than when the discrimination result is an analog line. However, it is preferable to increase the delay time. Further, it is preferable that a control means is provided for increasing the attenuation of only the transmitting-side attenuator when the determination result of the determination means is a digital line, compared to when the determination result is an analog line.

[0015]

In the hands-free telephone, the sound output from the speaker goes around the microphone. If the line to be connected is a digital line, TD
It adopts the MA (time division multiplex) method and the like, and there is a delay in communication. Therefore, when the transmission signal returns to the receiving side due to reflection, it becomes an echo. Therefore, there is a demand for canceling echo when connected to a digital line.

On the other hand, in an analog line, there is almost no time delay in transmitting a voice signal. Therefore, the return of the audio signal due to reflection is repeated, and howling tends to occur, and there is a demand to cancel this howling.

In particular , the determination means determines whether the line to which the device is connected is a digital line or an analog line. Then, the control means adjusts the amount of attenuation of the reception signal and the transmission signal according to the obtained determination result. Therefore, when the telephone device is connected to a digital line, control is performed so as to cancel echo, and when the telephone device is connected to an analog line, control is performed so as to cancel howling. It can be performed.

Further, when the line to be connected is a digital line, the receiving side attenuator and receiving the interrupt, except when reception is turned on and allowed to attenuate the received signal. Therefore, even if the transmission signal returns as an echo, the echo is not output from the speaker, and suitable echo cancellation can be performed.

On the other hand, if the line to be connected is an analog line, a transmission interrupt for turning on the receiving attenuator at the time of transmission is set. Therefore, it is possible to prevent the transmission signal from being output from the speaker, and to achieve effective howling cancellation.

[0020]

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

[Structure of Embodiment] FIG. 1 is a block diagram showing the structure of the embodiment. A microphone 3 and a speaker 4 are connected to the wireless telephone 1 via a telephone computer 2.

The voice of the caller is converted into an electric signal (sending signal) by the microphone 3 and supplied to the wireless telephone 1 via the telephone computer 2. The wireless telephone 1 converts a transmission signal into a predetermined radio signal and transmits the signal. Then, this transmission radio wave is received by the base station and transmitted to the other party's telephone via a normal exchange.

On the other hand, a signal from the other party's telephone is received by the wireless telephone 1 via the exchange and the base station. The wireless telephone 1 supplies the received reception signal to the speaker 4 via the telephone computer 2, and the reception voice is output from the speaker 4.

The telephone computer 2 has therein a transmitting side amplifier 21, a transmitting side attenuator 22, a receiving side amplifier 23, a receiving side attenuator 24, and a transmission / reception determination section 2.
5, a CPU 26 and a digital / analog setting switch 27.

The transmission signal from the microphone 3 is supplied to a transmission amplifier 21 of the telephone computer 2. The transmitting side amplifier 21 performs a predetermined amplification process on the transmitting side signal and supplies the signal to the transmitting side attenuator 22. The transmission side attenuator 22 performs a predetermined attenuation process on the transmission signal and supplies the signal to the wireless telephone 1. Then, the output signal of the transmitting side attenuator 22 is supplied to the wireless telephone 1.

On the other hand, the reception signal supplied from the wireless telephone 1 is subjected to a predetermined attenuation process in the reception-side attenuator 24 of the telephone computer 2 and then received.
And is supplied to the speaker 4.

The CPU 26 is connected to the wireless telephone 1 by a downstream serial signal line 31 and an upstream serial signal line 32.
Various data are exchanged by using 1, 32.

The hands-free telephone device of the present invention has the above-described configuration.
Controls the attenuation of the transmitting-side attenuator 22 and the receiving-side attenuator 24 depending on whether the line to which is connected is a digital line or an analog line. Here, the determination of whether the connected line is digital or analog will be described first.

[Determination of Digital / Analog] Whether the line to be connected is a digital line or an analog line is usually determined by the CPU 26 based on data supplied from the wireless telephone 1.

That is, when the telephone computer recognizes that the power switch (accessory switch ACC for supplying power to various devices in the case of a vehicle) is turned on, it notifies the wireless telephone 1 of this. Wireless telephone 1
Supplies various information about the telephone call to the telephone computer 2, such as information about the system reset and information about the reception level. The information includes "system display". The data "system display" is transmitted by the wireless telephone 1 only when the connected line is a digital line. Therefore, the CPU 26 of the telephone computer 2 determines whether the connected line is a digital line or an analog line by checking whether the "system display" data is sent.

In this embodiment, a digital / analog setting switch 27 operated manually is provided.
The type of line to which the CPU 26 is connected can also be determined based on the setting of the digital / analog setting switch 27. That is, on the assumption that the user operates the digital / analog setting switch 27 according to the line to be used, the type of the line to be connected to the CPU 26 is determined according to the operation state of the digital / analog setting switch 27. Is also good.

The CPU 26 controls the attenuation of the transmitting-side attenuator 22 and the receiving-side attenuator 24 based on the determination result. So, about this,
This will be described below.

"Determination of transmission and reception" The transmission / reception determination unit 25 determines whether the telephone is transmitting or receiving.
The transmission / reception determination unit 25 detects the level of the transmission signal input from the microphone 3 or the level of the reception signal supplied from the wireless telephone to the reception-side attenuator 24, and this level is equal to or higher than a predetermined level. Thus, it is possible to determine whether a call is being transmitted or received. In particular, the voice of a human is from about 300 Hz to about 3000 Hz, and the level of a signal in this frequency range may be detected. In addition, 5
The range may be about 00 to 1500 Hz. Then, the determination result is supplied to the CPU 26. Therefore, the CPU 26
In the above, it is possible to determine whether a call is being transmitted or received.

[Operation of First Embodiment] The operation of the first embodiment will be described with reference to the flowchart of FIG. First, the CPU 26 determines whether the connected line is a digital line or an analog line (S11). In the case of a digital line, the attenuation of the transmitting-side attenuator 22 and the receiving-side attenuator 24 is set to a relatively large amount of attenuation B.
(For example, 20 dB) (S12). next,
It is determined whether the current attenuation control of the attenuators 22 and 24 is a transmission interruption (S13). If it is a transmission interruption, it is changed to a reception interruption (S14), and if it is a reception interruption, the process is terminated as it is.

On the other hand, in S11, if the connected line is an analog line, the attenuation of the transmitting-side attenuator 22 and the receiving-side attenuator 24 is set to a relatively small amount of attenuation B '(for example, 12 dB). S1
5). Next, it is determined whether the current attenuation control of the attenuators 22 and 24 is a reception interruption (S16). If it is a reception interruption, the transmission interruption is changed (S1).
7) If the transmission interrupt has already occurred, the processing is terminated as it is.

In this way, if the connected line is a digital line, the signal attenuation is set to be large, and the reception interrupt is set. If the connected line is an analog line, the signal attenuation is set. Set the attenuation to a small value and set the transmission interrupt.

Here, the attenuation control of the transmitting side attenuator 22 and the receiving side attenuator 24 will be described with reference to FIG.

First, if the connected line is a digital line, the transmitting side attenuator is off and the receiving side attenuator is on during transmission. Here, when a reception signal indicating that a call is being received is input, the receiver attenuator is turned off and the transmitter attenuator is turned on. by this,
It is possible to sufficiently amplify and output the received signal during reception,
In addition, since the signal is greatly attenuated except during the reception, the echo caused by the transmission signal delayed from the reception signal can be effectively canceled.

When the connected line is an analog line, the transmitting side attenuator 22 is turned off only when a transmission signal indicating that transmission is in progress is input. The receiver attenuator 24 is turned on only during transmission. This allows
Howling can be prevented, and an attenuator is usually inserted on the transmitting side, so that good communication can be performed without running noise or the like of the vehicle being transmitted to the other party.

Further, the echo can be sufficiently attenuated by setting the attenuation of the attenuators 22 and 24 on the transmitting side and the receiving side to be large when connected to the digital line. On the other hand, by setting the attenuation of the transmitting-side and receiving-side attenuators 22 and 24 to such a small amount as to prevent howling when connected to the analog line, it is possible to prevent howling from occurring, Since the amount of attenuation can be set to the minimum necessary, it is possible to perform an optimal hands-free call as an analog line.

[Second Embodiment] Next, the operation of the second embodiment will be described with reference to FIG. In the second embodiment, the receiving-side attenuator remains at the transmission interruption even if the line to be connected is a digital line.

That is, it is determined whether the connected line is a digital line (S21). If the line is a digital line, the transmitting side and the receiving side attenuators 22, 24 are set to a relatively large value B (for example, 20 dB). Set (S22)
At the same time, the delay time is set to a relatively long time A (S23). On the other hand, if the connected line is an analog line in S21, the transmitting side and the receiving side attenuators 22 and 24 are set to a relatively small value B '(for example, 12 dB) (S24) and the delay is set. The time is set to a relatively small time A '(S25).

Therefore, as shown in FIG. 5, when the line to be connected is a digital line, the time during which the receiving-side attenuator 24 is kept on is A hours after the end of the transmission. As a result, an echo that returns after a relatively long time can be cut with a delay time suitable for the echo.

On the other hand, when the line to be connected is analog, the delay time when the receiving-side attenuator 24 is kept on is set to A 'time. As a result, preparation for waiting for the next reception after transmission is completed can be made in a short time. According to the second embodiment, the transmission interruption is also performed in the case of the digital line, and the reception side attenuator 24 is in the off state in the normal state, but the transmission side attenuator 22 is in the off state.
It is on . Therefore, it is possible to prevent the in-vehicle noise from being heard by the other party, and to prevent the beginning of the voice from the other party from being interrupted or the sound from being suddenly output at the start of the reception and giving an unnatural feeling.

[Other Configurations] In the first and second embodiments described above, in S12 and S22, both the transmitting side and the receiving side attenuators 22 and 24 are set to relatively large values. However, the receiver attenuator 24
May be set as is and the attenuation amount of only the transmitting side attenuator 22 may be set to be large. In this way, it is possible to cancel only the echo that can be heard when the voice of the call partner returns to the call partner via the speaker and the microphone on the vehicle side. The echo that can be heard by the other party is the most significant problem, and this problem is solved by controlling and attenuating only the attenuator 22 on the transmitting side.

Further, the hands-free telephone device of the present invention can be used not only for automobile telephones but also for various telephone devices.

[0047]

As described above, according to the present invention,
The attenuation of the received signal and / or the transmitted signal is adjusted according to whether the line to be connected is a digital line or an analog line. Therefore, when the telephone device is connected to a digital line, the echo can be canceled, and when the telephone device is connected to an analog line, the amount of attenuation becomes a necessary minimum, so that a suitable call can be made.

[0048] Also, when the line to be connected is a digital line, the receiving side attenuator except when reception is turned on and allowed to attenuate the received signal. Therefore, even if the transmission signal returns as an echo, the echo is not output from the speaker, and suitable echo cancellation can be performed. on the other hand,
If the line to be connected is an analog line, the receiver attenuator is turned on during transmission. Therefore, a good telephone call can be made without in-vehicle noise being transmitted to the other party.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an embodiment.

FIG. 2 is a flowchart showing the operation of the first embodiment.

FIG. 3 is a timing chart showing the operation of the first embodiment.

FIG. 4 is a flowchart showing the operation of the second embodiment.

FIG. 5 is a timing chart showing the operation of the second embodiment.

[Explanation of symbols]

1 wireless telephone, 2 telephone computer, 3 microphone, 4 speakers, 21 transmitting amplifier, 2
2 Sender-side attenuator, 23 Receiver-side amplifier, 24
Receiving-side attenuator, 25 Transmission / reception determination unit, 26 C
PU.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroaki Shimizu 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-2-60269 (JP, A) JP-A-5-205 55951 (JP, A) JP-A-2-301355 (JP, A) JP-A-2-246656 (JP, A) JP-A-2-147958 (JP, U) (58) Fields investigated (Int. ^7, DB name) H04M 1/00 H04M 1/24 H04M 1/58 - 1/62 H04M 1/66 - 1/78

Claims (5)

(57) [Claims] 1. A digital-to-analog shared hands-free telephone device that can be used when connected to either a digital line or an analog line, and attenuates the signal level of a received signal to a speaker. (24), a transmitting-side attenuator (22) for attenuating the signal level of the transmission signal from the microphone, determining means for determining whether the connected line is a digital line or an analog line, and determining results of the determining means. Control means for increasing at least the attenuation of the transmitting-side attenuator when the result of the determination is a digital line compared to when the result of the determination is an analog line. 2. A digital-to-analog shared hands-free telephone device that can be used when connected to either a digital line or an analog line, and attenuates the signal level of a received signal to a speaker. (24), a transmitting-side attenuator (22) for attenuating the signal level of the transmission signal from the microphone, determining means for determining whether the connected line is a digital line or an analog line, and determining results of the determining means. Control means for increasing the attenuation of the receiving-side attenuator and the transmitting-side attenuator when the result of the determination is a digital line, as compared to when the result of the determination is an analog line; . 3. The apparatus according to claim 1, wherein the control unit determines that a connected line is a digital line based on a result of the determination performed by the determination unit, and that the control unit controls a receiving side when a reception signal is input. A hands-free telephone device for performing a reception interruption control for turning off an attenuator, and performing a transmission interruption control for turning on a reception-side attenuator when a transmission signal is input, when it is determined that a line to be connected is an analog line; . 4. The apparatus according to claim 1, wherein the control unit determines that a connected line is a digital line based on a result of the determination by the determination unit, and that the control unit controls a receiving side when a transmission signal is input. Turn on the attenuator, perform transmission interrupt control to keep the receiving attenuator on for a period of time from the end of transmission to after the delay time.When it is determined that the connected line is an analog line, Turn on the receiving-side attenuator, perform transmission interruption control to make the time to keep the receiving-side attenuator on from the end of transmission to after the delay time, and the determination means includes:
A hands-free telephone device characterized in that the delay time is made longer when the result of the determination is a digital line than when the result of the determination is an analog line. 5. The apparatus according to claim 1, wherein when the determination result of the determination unit is a digital line, the attenuation amount of only the transmission-side attenuator is larger than when the determination result is an analog line. A hands-free telephone device, comprising: