JP2000101485A - Voice communication device with echo canceller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a speech transmission characteristic that is always satisfactory, regardless of the kinds of communication line. SOLUTION: A transmission signal line is provided with a speech transmission amplifier 19, consisting of a variable gain amplifier, a control circuit 30A discriminates a transmission loss of a line of a connection destination based on information related to a type of line or a transmission loss informed from a master set(MS) in terms of a control signal and compares the discriminated transmission loss with a transmission loss of a reference analog telephone line and sets variably a gain of the speech transmission amplifier 109, depending on the comparison result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice communication device having an echo canceller.

[0002]

2. Description of the Related Art Some voice communication devices have a hands-free call mode, in addition to a handset call mode in which a call is made using a handset. In the hands-free call mode, a speaker and a microphone for hands-free call are provided separately from the handset, and the hands-free call speaker and the microphone can be used in place of the handset to make a call. The use of the hands-free call mode allows the speaker to freely use both hands during a call, which is very convenient.

[0003] However, when a hands-free call is performed, a received voice output from a speaker is reflected on a wall or a ceiling and spills over to a microphone, which may generate an acoustic echo. This acoustic echo is extremely undesirable, particularly in voice communication devices such as digital telephone devices having relatively large transmission delays, resulting in remarkable deterioration in speech quality.

Therefore, an echo canceller is used in this type of apparatus. The echo canceller estimates the characteristics of the acoustic echo path using an adaptive filter and generates a pseudo echo having the same characteristics as the acoustic echo path. Then, the pseudo echo is subtracted from the transmission signal to cancel the acoustic echo component included in the transmission signal.

However, in order to completely cancel the acoustic echo using only the echo canceller, a large-scale and complicated circuit is required, and the cost is high. For this reason, in general, when designing an echo canceller, the upper limit of the cancellation amount is set arbitrarily, and acoustic echoes up to the set upper limit are canceled. This allows the echo canceller to be relatively simple, small, and inexpensive. In addition, the acoustic echo transmitted to the transmission signal path without being completely canceled is attenuated by the transmission loss of the communication line or the like, so that the side tone characteristics do not deteriorate on the communication partner side and the communication quality is good. Is kept.

However, the transmission loss of a communication line differs depending on the type. For example, the transmission loss of an extension connected via a private branch exchange or a key telephone main unit is generally smaller than the transmission loss of an analog subscriber line of a public telephone network. Even in the same public telephone network, the transmission loss of a digital line such as ISDN is smaller than that of an analog subscriber line. For this reason, depending on the type of communication line used, the acoustic echo that cannot be completely canceled by the echo canceller is sent to the terminal device of the other party without receiving sufficient attenuation, and as a result, the side tone characteristics of the other party deteriorate. There was a case.

On the other hand, in the hands-free call mode, for example, when the surrounding noise is loud or when a call is made at a position slightly away from the apparatus, the volume of the received voice may be increased by operating the volume. However, a speaker for hands-free communication built in the device is generally small and has a low output, so that when an excessive reception signal is applied, the received voice is distorted. Also, when a loud reception sound is output from the speaker, the sound pressure of the device vibrates the housing or the like of the device, so that a so-called chattering sound is generated.

[0008] When the distortion of the received voice is increased or the chattering noise is generated as described above, an erroneous learning is performed by the echo canceller, and an appropriate echo canceling process is not performed. In addition, if the input level of the acoustic echo to the microphone is increased due to the output of a loud received voice, the echo canceller cannot identify whether the input transmitted signal is the original transmitted signal or the acoustic echo. ,
As a result, appropriate cancel processing cannot be performed.

[0009]

As described above, in the conventional wired telephone device with an echo canceller, the acoustic echo that cannot be completely canceled by the echo canceller is not sufficiently attenuated depending on the type of the communication line connected. Is sent to the terminal device of the other party, and as a result, there is a problem that the side tone characteristics of the other party deteriorate.

[0010] In addition, if an attempt is made to increase the reception volume,
Since the wraparound to the microphone is increased, the distortion of the reception output is further increased, and a chattering sound is generated, there is a concern that erroneous learning is performed in the echo canceller and an appropriate echo cancellation process is not performed.

A first object of the present invention is to provide a voice communication device with an echo canceller that can always obtain good transmission characteristics regardless of the type of communication line. It is to be.

A second object of the present invention is to provide a voice communication device with an echo canceller that does not malfunction even when the received sound volume is increased. A third object is to provide an echo canceller which can prevent malfunction of the echo canceller even when the reception sound volume is increased, and suppresses the level of an acoustic echo returning to the other party to maintain good transmission quality. It is to provide a voice communication device.

[0013]

SUMMARY OF THE INVENTION In order to achieve the first object, the present invention provides a speaker for loudspeaking and outputting a received voice corresponding to a received voice signal, and a loudspeaker for collecting and transmitting a transmitted voice. A microphone that outputs a signal, and an echo canceller that estimates a sound echo path from the speaker to the microphone, generates a pseudo echo based on the estimation result, and subtracts the pseudo echo from the transmission signal,
In a voice communication device with an echo canceller that performs voice communication with a communication partner by selectively using a plurality of types of communication lines having different transmission losses, a transmission signal path between the echo canceller and the communication line is provided. A transmission gain variable means is provided and the gain control means is provided, and the gain control means variably controls the gain of the transmission gain variable means according to the type of the selected communication line. It is composed.

Specifically, when connected to a communication network having a function of notifying the transmission loss of the communication line, the gain control means adjusts the transmission gain variable according to the transmission loss notified from the communication network. A configuration for variably controlling the gain of the means;
When the user has a function of selecting and specifying a communication line by key operation, the gain control means variably controls the gain of the transmission gain variable means in accordance with the type of communication line selected and specified by the key operation. Configuration.

Therefore, according to the present invention, an appropriate transmission loss is inserted each time according to the type of communication line to be connected and the amount of transmission loss. For example, when a communication line having a smaller transmission loss than an analog subscriber line of a public telephone network is selected, such as an extension of a private branch exchange system or a key telephone system, the transmission line is larger than when an analog subscriber line is selected. Transmission loss is inserted. For this reason, the acoustic echo that cannot be completely canceled by the echo canceller is sufficiently attenuated by the transmission loss before being sent to the communication device of the other party. Therefore, it is possible to maintain good sidetone characteristics of the other party.

On the other hand, in order to achieve the second object, the present invention provides a speaker for loudspeaking and outputting a received voice corresponding to a received voice signal, and collects a transmitted voice and outputs a corresponding transmitted signal. A voice communication device with an echo canceller comprising a microphone and an echo canceller for estimating an acoustic echo path from the speaker to the microphone, generating a pseudo echo based on the estimation result, and subtracting the pseudo echo from the transmission signal. A variable reception gain means for variably controlling the gain of a received voice signal input to the speaker; and stopping the operation of the echo canceller when the gain of the variable reception gain control means exceeds a predetermined threshold value. And echo canceller control means for causing

Therefore, according to the present invention, when the user increases the reception volume by operating the volume, the operation of the echo canceller is automatically stopped when the reception gain exceeds the threshold. For this reason, even if an excessive reception signal is applied to the speaker and the received voice is distorted, or if the sound pressure of the device causes the housing of the device to vibrate and generate a so-called chattering sound, this causes the echo canceller to malfunction. No more worries. In addition, even if a loud reception sound is output from the speaker, the echo canceller malfunctions even if it becomes impossible to determine whether the input transmission signal is an original transmission signal or an acoustic echo. Don't worry.

Further, in order to achieve the third object, the present invention provides a voice switch between an echo canceller and a communication line, and a control means for the voice switch. When the gain exceeds a predetermined value, the voice switch is controlled to insert a predetermined amount of loss into the transmission signal path in conjunction with the stop of the operation of the echo canceller.

Therefore, according to the present invention, even if the echo canceller stops its operation due to the output of the received sound of a large volume, even if a high-level acoustic echo is output without being canceled by the echo canceller, the acoustic echo remains the above-mentioned sound. Suppressed by switch. For this reason, the sidetone characteristics of the communication partner device are favorably maintained.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a schematic configuration diagram of an information communication system according to a first embodiment of the present invention. The public telephone network NW has subscriber lines SL1 to S
The telephones TEL1 to TELn are connected via Ln, respectively, and the digital key telephone system is connected via the subscriber line SLk. The digital key telephone system includes a main unit MS and digital key telephones DKT1 to DK connected to the main unit MS via extensions DL1 to DLm formed of digital transmission lines, respectively.
Tm.

The main unit MS is a digital key telephone D
It has a function of switching connection between KT1 to DKTm and the public telephone network NW and between digital key telephones DKT1 to DKTm, respectively, and further has various service functions for digital key telephones DKT1 to DKTm such as transfer and answering machine. .

By the way, the digital key telephone D
KT1 to DKTm are configured as follows. FIG. 2 is a circuit block diagram showing the configuration. Since the digital key telephones DKT1 to DKTm have the same configuration, the digital key telephone DKT1 will be described here as an example.

The transmission circuit 11 is connected to the extension DL1. The transmission circuit 11 performs multiplex transmission of a digital communication signal and a control signal with the main apparatus MS. This transmission circuit 1
The digital reception signal received at 1 is first amplified by the reception amplifier 12 and then input to the digital / analog converter (D / A) 13 via the echo canceller 20. Then, after being converted to an analog signal by the D / A 13, the signal is supplied to a speaker 15 via a speaker amplifier 14, and the speaker 15 outputs a received voice as a received voice. The receiving amplifier 12 is composed of a variable gain amplifier, and the receiving gain is variably controlled by the control circuit 30A according to the volume operation of the key input unit 31.

On the other hand, the transmitted voice of the speaker is collected by a microphone 16 and converted into a transmitted signal, and then input to an analog / digital converter (A / D) 18 via a microphone amplifier 17. After being converted to a digital transmission signal by the A / D 18, the echo canceller 2
Input to 0.

The echo canceller 20 includes an adaptive filter 2
1 and a computing unit 22. The adaptive filter 21 is composed of, for example, a transversal filter. The filter generates a pseudo echo based on the digital reception signal and tap coefficients stored in a tap coefficient memory (not shown). The arithmetic unit 22 performs digital arithmetic processing for subtracting the pseudo echo generated by the adaptive filter 21 from the digital transmission signal output from the A / D 18. The adaptive filter 21 has a tap coefficient updating function, and performs a process of updating the tap coefficients stored in the tap coefficient memory based on the residual echo output from the computing unit 22.

The digital transmission signal output from the echo canceller 20 is input to the transmission circuit 11 via the transmission amplifier 19, and transmitted from the transmission circuit 11 to the main unit MS.

The digital key telephone DKT1 of this embodiment uses a variable gain amplifier as the transmission amplifier 19. Further, the control circuit 30A is newly provided with a transmission volume variable control function in addition to the various control functions relating to outgoing / incoming calls, telephone calls, and the like, and the above-described reception volume control function.

The transmission volume variable control function is performed by the main unit MS.
The gain control of the transmission amplifier 19 is performed according to the control information notified from. That is, the main unit MS has a function of determining the type of line to which the digital key telephone DKT1 is connected or the transmission loss for each line, and the determination result is notified to the digital key telephone DKT1 by a control signal. The transmission volume variable control function determines the transmission loss of the connected line according to the content of the control signal sent from the main unit MS. Then, the transmission loss is compared with the transmission loss of the reference analog subscriber line, and the gain of the transmission amplifier 19 is variably controlled in accordance with the comparison result. Keep it constant.

With such a configuration, for example, assume that the digital key telephone DKT1 has started a call with the telephone TEL1 connected to the public telephone network NW.
Then, prior to the start of the call, the main unit MS sends the subscriber lines SLk, S to the digital key telephone DKT1.
Information about the type of L1 or transmission loss is notified by a control signal. In the digital key telephone DKT1, when the control circuit 30A receives the control signal, the control circuit 30A determines the transmission loss of the connected line based on the content of the control signal and compares the transmission loss with the transmission loss of the reference analog telephone line. Then, the gain of the transmission amplifier 19 is controlled according to the result.

For example, since the line currently connected is the subscriber line SLk or SL1 of the public telephone network NW, that is, an analog telephone line, the difference between the transmission loss notified from the main unit MS and the reference transmission loss is as follows. And therefore the control circuit 30
A sets the gain value for the analog telephone line in the transmission amplifier 19. Therefore, when a call is started thereafter, the transmission signal level is adjusted to a level suitable for an analog telephone line by the transmission amplifier 19 and then transmitted.

On the other hand, it is assumed that digital key telephone DKT1 has started a call with another digital key telephone DKT2. In this case, information about the type of digital extension DL2 or transmission loss is notified from the main unit MS to the digital key telephone DKT1 by a control signal prior to the start of the call. Here, the transmission loss of the digital extension DL2 is generally smaller than the transmission loss of the analog telephone line. For this reason, the control circuit 30A sets a gain value smaller than the gain value for the analog telephone line by the transmission loss difference in the transmission amplifier 19.

Accordingly, the transmission signal level is adjusted by the transmission amplifier 19 to a level corresponding to the transmission loss of the digital extension DL2, that is, adjusted to a level smaller than that of an analog telephone line and transmitted. Therefore, even if the acoustic echo of the received voice cannot be completely canceled by the echo canceller 20, this acoustic echo is transmitted to the digital key telephone DKT2 of the other party after its level is suppressed by the transmission amplifier 19. Therefore, in the digital key telephone DKT2 of the other party, the sidetone characteristic does not deteriorate due to the echo wraparound.

As described above, in the first embodiment, the transmission amplifier 19 including a variable gain amplifier is provided in the transmission signal path,
The control circuit 30A determines the transmission loss of the connection destination line based on the information on the line type or the transmission loss notified by the control signal from the main device MS, and determines the transmission loss and the transmission loss of the reference analog telephone line. Are compared, and the gain of the transmission amplifier 19 is variably set according to the comparison result.

Therefore, even when using different types of lines, or when using the same type of lines but different transmission loss amounts, the level of the transmission signal transmitted to the device of the other party is kept below a certain level. can do. For this reason, even if the echo cannot be completely canceled by the echo canceller 20, this echo is sufficiently suppressed regardless of the line and transmitted to the partner device. For this reason, it is possible to maintain good sidetone characteristics of the communication partner device.

The first embodiment can be modified as follows. For example, a digital key telephone is generally provided with an outside line transmission button and an extension line transmission button. Therefore, a configuration may be adopted in which the type of the line is determined from the transmission button operated at the time of transmission, and the transmission gain is set according to the determination result.

FIG. 3 is a circuit block diagram showing a digital key telephone having such a configuration. 2, the same parts as those in FIG. 2 are denoted by the same reference numerals, and detailed description is omitted.

The key input section is provided with an outside line transmission button 32 and an extension line transmission button 33. Control circuit 30B
Determines which of the outside line transmission button 32 and the extension line transmission button 33 has been operated at the time of transmission. When the outside line transmission button 32 is operated, the transmission amplifier according to the transmission loss of the analog telephone lines SLk, SL1 to SLn is set in the transmission amplifier 19. On the other hand, when the extension transmission button 33 is operated, the transmission gain according to the transmission loss of the digital extensions DL1 to DLm is set in the transmission amplifier 19.

With such a configuration, the digital key telephones DKT1 to DKTm can be used even if the main unit MS does not receive information on the line type or the transmission loss.
, An optimal transmission loss is set independently.

As another configuration, it is conceivable that the present invention is applied to an analog key telephone. FIG. 4 is a circuit block diagram showing the configuration, and the same parts as those in FIG. 2 are denoted by the same reference numerals.

The main unit (not shown) and the analog key telephone unit are connected by an analog extension AL1. The analog extension AL1 is composed of a communication signal line and a control line which are independent from each other.

The communication signal transmitted from the main unit arrives at the key telephone via the communication signal line of the analog extension AL1. This call signal is input to an analog / digital converter (A / D) 34 via a hybrid circuit 36, where it is converted into a digital reception signal and then input to the echo canceller 20 via the reception amplifier 12. On the other hand, the digital transmission signal output from the echo canceller 20 is input to a digital / analog converter (D / A) 35 via the transmission amplifier 19, where it is converted into an analog transmission signal and then hybridized. Circuit 3
6 to the analog extension AL1.

On the other hand, the control signal generated in the main unit arrives at the key telephone through the control line of the analog extension AL1, and is input to the control circuit 30C. The control circuit 30C determines the transmission loss of the connection destination line based on the information on the line type or the transmission loss notified by the control signal, and sends the optimum transmission gain according to the transmission loss to the transmission amplifier 19. Set.

With such a configuration, for example, even when the transmission loss of the subscriber lines SL1 to SLn used for external calls and the transmission loss of the analog extensions AL1 to ALm used for internal calls are different, for example, a public telephone Even if the network is ISDN and the transmission loss of the digital subscriber line is different from the transmission loss of the analog extension, an optimum transmission gain can be set for each line.

(Second Embodiment) A second embodiment according to the present invention
In the embodiment, when a volume operation such that the reception volume exceeds a predetermined threshold is performed, the operation of the echo canceller is stopped to prevent a malfunction of the echo canceller, and at the same time, the voice switch is set to the reception mode. By setting, the transmission loss is inserted into the transmission path, so that the acoustic echo that has passed through the echo canceller is not transmitted to the other party's device at a high level.

FIG. 5 is a circuit block diagram showing a configuration of a digital key telephone apparatus according to a second embodiment of the present invention. In this figure, the same parts as those in FIG. 2 are denoted by the same reference numerals.

A digital extension DL is sent from a main unit (not shown).
The digital communication signal arriving via the transmission circuit 1
After being received at 1, the signal is input to the voice switch 40 via the receiving amplifier 12 and the automatic gain control (AGC) circuit. The digital reception signal passing through the voice switch 40 is input to the digital / analog converter (D / A) 13 via the echo canceller 20.
Here, after being converted into an analog reception signal, the signal is supplied to a speaker 15 via a speaker amplifier 14A, and is output from the speaker 15.

The receiving amplifier 12 is composed of a variable gain amplifier, and the receiving gain is variably controlled by the control circuit 30D according to the volume operation of the key input unit 31.
The AGC circuit 12A sets the maximum value of the signal level output from the receiving amplifier 12, so that the level of the digital receiving signal does not exceed the dynamic range of the D / A 13.

On the other hand, the transmission voice of the speaker is collected by the microphone 16 and converted into a transmission signal, and then input to the analog / digital converter (A / D) 18 via the microphone amplifier 17. After being converted to a digital transmission signal by the A / D 18, the echo canceller 2
Input to 0.

The echo canceller 20 has an adaptive filter 2
1 and a computing unit 22. The adaptive filter 21 is composed of, for example, a transversal filter. The filter generates a pseudo echo based on the digital reception signal and tap coefficients stored in a tap coefficient memory (not shown). The arithmetic unit 22 performs digital arithmetic processing for subtracting the pseudo echo generated by the adaptive filter 21 from the digital transmission signal output from the A / D 18. The adaptive filter 21 has a tap coefficient updating function, and performs a process of updating the tap coefficients stored in the tap coefficient memory based on the residual echo output from the calculator 22.

The digital transmission signal output from the echo canceller 20 is subsequently input to the voice switch 40. The voice switch 40 includes a reception level detector 41
, A transmission level detector 42, a comparator 43, a reception attenuator 44, and a transmission attenuator 45. The comparator 43 compares the average of the received signal level detected by the received level detector 41 with the average of the transmitted signal level detected by the transmitted level detector 42,
Thus, it is determined whether the apparatus is in the receiving state or the transmitting state. Then, as a result of the comparison, the loss is inserted in the transmission path by the transmission attenuator 45 in the reception state, while the loss is inserted in the reception path by the reception attenuator 44 in the transmission state.

The digital transmission signal output from the voice switch 40 is amplified by the transmission amplifier 19A, then input to the transmission circuit 11, and transmitted from the transmission circuit 11 to a main unit (not shown).

Incidentally, in the digital key telephone according to the present embodiment, the speaker amplifier 14A disposed immediately before the speaker 15 is constituted by a variable gain amplifier. This speaker amplifier 14A outputs a high-volume received voice without being affected by the dynamic range of the D / A 13 when a volume operation for increasing the received voice volume beyond a predetermined level is performed in the key input unit 31. The gain is variably controlled by the control circuit 30D.

FIG. 6 shows an example of the configuration of the speaker amplifier 14A. In this configuration, when the control signal output from control circuit 30D is at "L" (GND) level, the gain of speaker amplifier 14A is r3 / r2 times. On the other hand, when the control signal output from the control circuit 30D is at “H” (VDD) level, the speaker amplifier 14
The gain of A is r3 / (r1 + r2) times. Control circuit 3
In the case of 0D, the control signal is normally set to "H" level, and when the gain of the receiving amplifier 12 exceeds the threshold value due to an increase in the receiving volume, the control signal is set to "L" level to increase the gain of the speaker amplifier 14A. .

The control circuit 30D has a first received sound volume control function and a second received sound volume control function. The first receiving volume control function is a function of variably controlling the gain of the receiving amplifier 12 in accordance with the volume operation of the key input unit 31. The second receiving volume control function is to control the speaker amplifier 14 when the gain of the receiving amplifier 12 exceeds a predetermined threshold value in accordance with the volume operation of the key input unit 31.
The gain of A is increased to increase the receiving sound volume, and the operation of the echo canceller 20 is stopped. At the same time, the voice switch 40 is forcibly set to the receiving state to insert a loss into the transmission path.

Next, the operation of the apparatus configured as described above will be described. FIG. 7 is a flowchart showing a receiving sound volume control procedure and control contents by the control circuit 30D. The control circuit 30A monitors whether or not a volume operation has been performed in step 7a. In this state, it is assumed that the speaker has performed a volume up operation. Then, the control circuit 30A proceeds from step 7b to step 7c, where it adds the variable step width A to the value of the volume set value register SPVOL. At the same time, in step 7d, the voice switch insertion loss amount setting register VSL is set.
The variable step width A is also added to the value of OSS. Then, the value of the volume set value register SPVOL is changed to the maximum value VMA.
X, and if it does not reach the maximum value VMAX, step 7
j, and the SPVOL value is set to the threshold value GT.
Compare with H.

As a result of this comparison, if the value of SPVOL is smaller than the threshold value GTH, VSLOSS is determined in step 7k.
Is set in the voice switch 40, and in step 71, the gain ratt of the receiving amplifier 12 is set to the value SP.
Set to the value of VOL. In step 7m, the control signal level for the speaker amplifier 14A is set to "H". In step 7n, the echo canceller 20 is set to the operating state, and then the reception volume control routine ends.

Thereafter, each time the volume up operation is performed, the above control is repeatedly executed, whereby the gain of the receiving amplifier 12 gradually increases and the receiving sound volume gradually increases.

When the value of SPVOL becomes equal to or greater than the threshold value GTH, the control circuit 30D shifts from step 7j to step 7f, where the variable step width B is added to the value of VSLOSS, and after this addition, Is set to the voice switch 40. At the same time, in step 7g, the gain ratt of the receiving amplifier 12 is set to the value of SPVOL. In step 7h, the speaker amplifier 1
After setting the control signal level for 4A to "L" and setting the echo canceller 20 to the non-operation state in step 7i, the reception volume control routine ends.

Therefore, when the gain of the receiving amplifier 12 reaches the threshold value GTH, the further gain increase of the receiving amplifier 12 is stopped, and the gain of the speaker amplifier 14A is set to a value larger than the normal time. Therefore, the speaker 1
From 5 on, the received voice having a large received sound volume is output without being restricted by the upper limit value defined by the AGC circuit 12A. For this reason, the speaker can clearly hear the received voice even when the ambient noise is extremely loud or at a position away from the telephone.

At this time, the operation of the echo canceller 20 is stopped. For this reason, even if the received voice itself is distorted due to the output of the received voice having a large volume, or if a chattering sound is generated from the speaker 15 or the housing, there is no fear that the echo canceller 20 malfunctions due to this. Furthermore, since a large transmission loss is inserted into the transmission path by the voice switch 40, the acoustic echo that has passed through the echo canceller 20 as it is is sufficiently attenuated in the voice switch 40. Therefore, there is no fear that the acoustic echo is directly transmitted to the other party to cause howling.

As a result of the volume up operation,
When the value of SPVOL reaches the maximum value VMAX, the control circuit 30A unconditionally proceeds from step 7e to step 7f.
And the variable step width B is changed to the value of VSLOSS.
And the value after the addition is set in the voice switch 40. At the same time, the gain ratt of the receiving amplifier 12 is set to the value of SPVOL in step 7g, and the control signal level for the speaker amplifier 14A is set to "L" in step 7h.
After setting the echo canceller 20 to the non-operation state with
The reception volume control routine ends.

When the speaker performs the volume down operation, the control circuit 30A shifts from step 7b to step 7o, where the value of SPVOL is subtracted by the variable step width A. Step 7r
Then, the value of VSLOSS is also subtracted by the variable step width A. Then, the value of SPVOL after the subtraction is compared with a threshold value GTH in step 7j, and this threshold value GTH
If less than TH, steps 7k to 7n
, The process of reducing the transmission loss in the voice switch 40, the process of reducing the gain of the receiving amplifier 12, the process of setting the control signal given to the speaker amplifier 14A to the "H" level, and returning the echo canceller 20 to the operating state. Is performed.

As described above, according to the second embodiment, when the volume operation for increasing the gain of the receiving amplifier 12 to the threshold GTH or more is performed, the receiving amplifier 1
By setting the gain of the speaker amplifier 14A to a value larger than the normal time instead of the gain increase of 2, the speaker 15 is not restricted by the upper limit value defined by the AGC circuit 12A, and A received voice with a large received sound volume can be loudspeaked without exceeding the dynamic range of the D / A 13. For this reason, the speaker can clearly hear the received voice even when the ambient noise is extremely loud or at a position away from the telephone.

Also, by stopping the operation of the echo canceller 20 at the same time, even if the received voice itself is distorted due to the output of the received voice with a large volume, or if the loudspeaker 15 or the housing generates chattering sound, Thus, there is no fear that the echo canceller 20 malfunctions.

Further, at the same time, a large transmission loss is inserted into the transmission path by the voice switch 40, so that the acoustic echo that has passed through the echo canceller 20 as it is can be sufficiently attenuated by the voice switch 40. Thus, it is possible to reliably prevent howling from occurring in the communication partner device.

The above operation and effect will be described more specifically. It is now assumed that the initial value when the power of the telephone is turned on is SPVOL = 0 dB, VSLOSS = 6 dB, the variable step width of the volume A = 3 dB, VMAX = 15 dB, GTH = 15 dB, and the expected erasure amount of the echo canceller = 21 dB.

The gain of the speaker amplifier 14A is
The control signal is set to 10 dB when it is at the "H" level, and 13 dB when the control signal is at the "L" level. The gain of the AGC circuit is set so that the output of the D / A 13 has an upper limit of -10 dBV. Note that D / A13 and A / D1
The gains of 8 are each 0 dB.

When used in the initial state, the gain of the speaker amplifier 14A is 10 dB, VSLOSS is 6 dB, SP
VOL is 0 dB. At this time, the reception gain up to the speaker 15 is 10 dB, but when the reception signal input from the communication partner is large, the gain is adjusted so that the maximum signal level input to the speaker 15 becomes 0 dBV due to the level limitation of the AGC circuit. You. At this time, the echo returned to the call partner is 21 dB which is the amount of erasure of the echo canceller 20.
And 6 dB, which is the transmission loss of the voice switch 40, attenuates 27 dB and returns to the other party.

In this state, it is assumed that the volume operation is performed to reduce SPVOL to 12 dB. Then, the gain of the speaker amplifier 14A is 10 dB and the VSLOSS is 18
dB and SPVOL are 12 dB. At this time, the reception gain up to the speaker 15 is 22 dB, but when the reception signal input level from the other party is large, the maximum reception signal level input to the speaker 15 is set to 0 dBV due to the level limitation of the AGC circuit 12A. The gain is adjusted.
Therefore, the maximum output level of the speaker 15 becomes the same as the initial state. Of course, when the reception signal input level from the other party is low, a larger loudspeaker reception sound volume can be obtained as compared with the initial state. At this time, the echo returning to the call partner is the amount of elimination 21 d by the echo canceller 20.
B and the transmission loss 18 dB due to the voice switch 40 attenuate 39 dB. Therefore, howling does not occur on the telephone of the other party.

In this case, since the transmission loss of the voice switch 40 is as large as 18 dB, it is difficult to obtain a sense of simultaneous communication. However, this is the same with a conventional loudspeaker equipped with a voice switch, and is practically large. It doesn't matter.

Further, by operating the volume, SPVOL
Is set to 15 dB. In this case, the speaker amplifier 1
The gain of 4A is 13 dB, and a large amplification gain is obtained. Further, since the operation of the echo canceller 20 is stopped, VSLOSS is 42 dB and SPVOL is 15 dB. At this time, the reception gain up to the speaker 15 is 28d.
B, and the gain is adjusted so that the maximum level of the reception signal input to the speaker 15 is 3 dBV even when the reception signal input level from the other party is high. For this reason,
The maximum output level of the speaker 15 becomes higher than the initial state. Also, at this time, the echo returned to the call partner is attenuated by 42 dB due to the transmission loss of the voice switch 40.
Howling does not occur on the other party's telephone.

In this case, the transmission loss of the voice switch 40 is as large as 42 dB, but the difference is less perceptually intelligible than in the case where the transmission loss of the voice switch 40 is 18 dB. It is possible to realize a loud receiving operation with a certain volume.

The present invention is not limited to the above embodiments. For example, in each of the above embodiments, the key telephone was described as an example. However, the present invention may be applied to a general wired loudspeaker or a personal computer having a telephone function. The present invention may be applied to a telephone or the like.
In short, the present invention can be applied to any voice communication device having an echo canceller.

In each of the above embodiments, the case where the control circuit is constituted by a microcomputer has been described. For example, by using a digital signal processor such as a DSP, the control circuit and the telephone circuit can be integrated into one LSI.
It may be constituted as.

In addition, the type of the line, the detection method of the line transmission loss, the circuit configuration of the device, the receiving volume control procedure and the contents thereof can be variously modified without departing from the gist of the present invention.

[0076]

As described in detail above, according to the present invention,
A transmission gain variable means is provided in a transmission signal path between the echo canceller and the communication line, and the transmission line has a gain control means. The gain control means allows the transmission to be performed in accordance with the type of communication line used. Since the gain of the gain varying means is variably controlled, it is possible to provide a voice communication device with an echo canceller that can always obtain good transmission characteristics regardless of the type of communication line.

According to another aspect of the present invention, the receiving gain variable means for variably controlling the gain of the receiving voice signal input to the speaker, and the gain of the receiving gain variable control means exceeding a predetermined threshold value Provided with the echo canceller control means for stopping the operation of the echo canceller, it is possible to provide a voice communication device with an echo canceller that can prevent the malfunction of the echo canceller even when the reception volume is increased. .

According to still another aspect of the present invention, a voice switch is provided between the echo canceller and the communication line, and a control unit is provided. The control unit controls the gain of the reception gain variable unit to a predetermined value. If exceeded,
In conjunction with the stop of the operation of the echo canceller, by controlling the voice switch to insert a predetermined amount of loss in the transmission signal path, the echo canceller does not malfunction even when the reception sound volume is increased. In addition, it is possible to provide a voice communication device with an echo canceller capable of suppressing the level of an acoustic echo returning to the other party and maintaining good transmission quality.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an information communication system according to a first embodiment of the present invention.

FIG. 2 is a circuit block diagram showing a configuration of the digital key telephone according to the first embodiment of the present invention.

FIG. 3 is a circuit block diagram of a digital key telephone showing a modification of the first embodiment.

FIG. 4 is a circuit block diagram of an analog key telephone which is another modification of the first embodiment.

FIG. 5 is a circuit block diagram showing a configuration of a digital key telephone according to a second embodiment of the present invention.

6 is a circuit diagram showing a configuration of a speaker amplifier provided in the digital key telephone shown in FIG.

7 is a flowchart showing a receiving sound volume control procedure and control contents in a control circuit of the digital key telephone shown in FIG. 5;

[Description of Signs] NW: Public telephone network SL1 to SLn, SLk: Subscriber line TEL1 to TELn: Telephone MS: Main unit of digital key telephone system DL1 to DLm: Digital extension DKT1 to DKTm: Digital key telephone 11: Transmission circuit 12: Receiver amplifier 12A: Automatic gain control (AGC) circuit 13: Digital / analog converter (D / A) 14, 14A: Speaker amplifier 15: Speaker 16: Microphone 17: Microphone amplifier 18: Analog / digital converter (A / D) 19,19A ... Transmission amplifier 20 ... Echo canceller 21 ... Adaptive filter 22 ... Calculator 30A, 30B, 30C, 30D ... Control circuit 31 ... Key input unit 32 ... Outline transmission button 33 ... Extension transmission button 40 ... Voice Switch 41: Receiving level detector 4 ... transmitting level detector 43 ... comparator 44 ... reception amplifier 45 ... microphone attenuator

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K027 AA03 BB03 DD10 5K046 DD13 HH11 HH61 HH69 HH72 HH79 5K067 AA23 FF38 HH07

Claims (5)

[Claims] A speaker for loudspeaking and outputting a received voice corresponding to a received voice signal, a microphone for collecting a transmitted voice and outputting a corresponding transmitted signal, and an acoustic echo path from the speaker to the microphone are estimated. And an echo canceller for generating a pseudo echo based on the estimation result and subtracting the pseudo echo from the transmission signal, and selectively communicating with a communication partner by using a plurality of types of communication lines having different transmission losses. A voice communication device with an echo canceller that performs voice communication between the echo canceller and a communication line. And a gain control means for variably controlling the gain of the transmission gain variable means. 2. When connected to a communication network having a function of notifying a transmission loss of a communication line, the gain control means:
2. The voice communication device with an echo canceller according to claim 1, wherein a gain of said transmission gain variable means is variably controlled according to a transmission loss notified from said communication network. 3. When the user has a function of selecting and specifying a communication line by a key operation, the gain control means includes a function of the transmission gain variable means according to a type of the communication line selected and specified by the key operation. The voice communication device with an echo canceller according to claim 1, wherein the gain is variably controlled. 4. A speaker for loudspeaking and outputting a received voice corresponding to a received voice signal, a microphone for collecting a transmitted voice and outputting a corresponding transmitted signal, and an acoustic echo path from the speaker to the microphone is estimated. In the voice communication apparatus equipped with an echo canceller, which generates a pseudo echo based on the estimation result and subtracts the pseudo echo from the transmission signal, the gain of the received voice signal input to the speaker is varied. An echo canceller comprising: a receiving gain variable means for controlling; and an echo canceller controlling means for stopping the operation of the echo canceller when a gain of the receiving gain variable means exceeds a predetermined value. With voice communication device. 5. A voice switch provided between the echo canceller and a communication line, wherein the voice switch inserts a loss into one of a reception signal path and a transmission signal path according to a result of comparison between the reception signal level and the transmission signal level. When the gain of the receiving gain variable means exceeds a predetermined value, in conjunction with the stop of the operation of the echo canceller, the voice switch is controlled to insert a predetermined amount of loss into the transmission signal path. 5. The voice communication device with an echo canceller according to claim 4, further comprising: a voice switch control unit that performs the operation.