JPS6085664A - Conference telephone set - Google Patents

Abstract

PURPOSE:To optimize the performance of switching and conversation in response to the connected number of devices by providing a level detection measuring circuit to a conference telephone set, processing the operation of side tone coupling loss and storing it and controlling a variable gain amplifier circuit based on the data so as to prevent transmission blocking. CONSTITUTION:Slave devices 1011-101n are connected in parallel with a host device 100. In measuring the side tone coupling loss, the host device 100 turns on a manual switch 17 so as to transmit measuring mode information to the slave devices through a transceiver 16. The received signal from a terminal 9 is outputted to a terminal 8 while being brought into the same level as a normal acoustic coupling amount by a loop including a pesudo acoustic coupling circuit 19 in the selected slave device. On the other hand, the signal of the standard level is transmitted from a standard signal generating circuit 18 to the terminal 8 in the host device, a control circuit 5 operates a side coupling loss amount by using the level measured by an A/D converter 12 and the level at the terminal 8 and stores it respectively to the host and slave devices respectively. This is made the same with other slave devices. All the devices restore at this point of time the insertion loss of control variable loss circuits 4, 13 to the normal loss control so as to make the gain of a channel stable.

Description

[Detailed Description of the Invention] [Technical Field to which the Invention Pertains] The present invention enables participants in remote conference rooms connected by communication lines to have hands-free conferences with each other using microphones and speakers installed in the conference room. The present invention relates to a conference telephone device for making telephone calls. In particular, the present invention relates to howling prevention in a conference telephone device equipped with a variable gain amplifier circuit.

[Description of prior art]

Conventionally, in this type of hands-free conference telephone device using a microphone and a speaker, a variable gain +111m circuit used to prevent the howling phenomenon caused by acoustic coupling between the microphone and the speaker has been used to prevent sound from being collected by the microphone. The level of the transmitted audio signal is compared with the level of the received signal from the other party, and the channel with the higher audio signal level is carved to eliminate loss and obtain a steady gain. It operates so that a loss is inserted into the communication path where the level is lower. Therefore, in conventional conference telephone devices using variable gain amplifier circuits, the circuit system is fixed, assuming that the amount of sidetone coupling loss due to the attenuation of the communication line and the number of conference phones connected by the communication line is within a certain range. As a result, even under conditions that were better than expected, the interactivity did not improve at all, and under conditions that were worse than expected, the outgoing audio signal level was lower than the level of the outgoing audio signal. Because the signal level is high, the variable gain amplifier circuit malfunctions due to the own transmitted voice, resulting in a serious drawback in that the call is interrupted (call blocking phenomenon). Here, the amount of sidetone coupling loss refers to the level difference between an audio signal sent from a conference telephone device and when this audio signal is returned due to acoustic coupling between the micropon and the speaker of the other party's conference telephone device. .

[Purpose of the invention]

The present invention eliminates the above-mentioned drawbacks and provides optimum communication even under conditions where the amount of sidetone coupling loss changes due to fluctuations in attenuation of the communication line and increase/decrease in the number of conference telephone devices connected to the communication line. The purpose of the present invention is to provide a conference telephone device that provides high performance (interactivity).

[Features of the invention]

In order to prevent ringing and echoes caused by acoustic coupling between a microphone and a speaker, the present invention aims to reduce the level of a transmitting signal picked up by a microphone and the level of a receiving signal sent from the other party, for example, a conference room. By comparing the magnitudes, the output of the variable loss circuit and level detection circuit, which inserts loss, is set as a steady gain for the communication path with a higher signal level, while for the communication path with a lower signal level. The standard A level detection and measurement circuit consisting of a signal generation circuit, a pseudo-acoustic coupling circuit, a pseudo-acoustic coupling switching circuit, and a manual switch is provided. One of the conference telephone devices having such a measurement function is designated as a main device, and the other conference telephone device is designated as a slave device. The signal level sent from the transmitting line end of the main device is measured at the level that reaches the receiving line end of the main device via a plurality of slave devices connected to the communication line. For this purpose, the control circuit is driven by the manual switch to make the control circuit recognize that the measurement operation is being performed, and the transmitting signal switching circuit is switched to the standard signal generation circuit side for a certain period of time, and the main device is switched to the standard signal generation circuit side. A standard signal is output from the transmitting end, and in a slave device connected by a communication line, the normal communication circuit is disconnected and the amount of acoustic coupling loss from the speaker to the microbond, that is, the amount of acoustic coupling loss, and the electrical Switch to a pseudo-acoustic coupling circuit that is replaced with an equalization level. This is measured by the slave device and the main device of each station as appropriate under the control of the control circuit 11. Thereby, in the control circuit, the amount of deflection of the transmitting signal to the receiving end, including the amount of attenuation of the line, is calculated and the deflection data is stored. After the measurement operation is completed, the main device switches the transmitting signal input switching circuit to the transmitting line terminal side, and the slave device returns from the pseudo loop circuit to the speaking circuit to enter the talking state, and the control circuit Transmitting and receiving signals generated during a phone call are processed through the level detection circuit using at least one of the signal levels input to the control circuit and the stored data of the amount of sidetone coupling loss. The comparison operation of the level detection circuit output in the variable gain amplifier circuit is controlled to minimize the difference in the transmitting/receiving switching level, and the loss control of the variable loss circuit of the communication path is also performed to reduce the sidetone coupling loss. The loss amount is determined and controlled based on the amount data.

That is, the present invention provides a microphone, a transmission variable gain amplification means for amplifying the output signal of the microphone,
A transmission terminal to which the output of the variable gain amplification means is connected;
A receiving terminal, a receiving variable gain amplifying means for amplifying the signal of the receiving terminal, a speaker driven by the output of the variable gain amplifying means, and a control for controlling the gain j# of the two variable gain amplifying means. one main device including a circuit, a data transmitting means for transmitting a control signal output from the control 311 circuit to the transmitting terminal, a microphone, and a variable gain for transmitting to amplify the output/output signal of the microphone. an amplifying means, a transmitting terminal to which the output of the variable gain amplifying means is connected, a receiving terminal, a variable gain amplifying circuit stage for reception that amplifies the signal at the receiving terminal, and a circuit driven by the output of the variable gain amplifying means. one or more slave devices including a speaker, a control circuit for controlling the gains of the two variable gain amplifying means, and data receiving means for receiving a control signal arriving at the receiving terminal and applying it to the control circuit. The signal at the transmission terminal of the main device is transmitted to each reception terminal of the slave device, and the signal at the transmission terminal of the slave device is transmitted to each reception terminal of the slave device other than the main device and its slave device. In a conference telephone device connected by a transmission line such that The slave device is equipped with a measuring means for measuring the signal, and the slave device transmits a signal arriving at its receiving terminal to its transmitting terminal.
The control circuit of the main device is equipped with a pseudo-acoustic coupling circuit that can pseudo-couple the state in which the speaker of the slave device and the microbon are acoustically coupled as an electric signal, and the control circuit of the main device has a pseudo-acoustic coupling circuit that can be activated by manual operation. means for switching the main device to a measurement mode, and means for outputting a measurement mode switching control signal to the data transmission means when switched to measurement mode 1-'; Means is provided for switching the slave device to the measurement mode upon receiving the measurement mode switching control signal from the data receiving means, and when switched to the measurement mode, the main device receives the output signal from the microphone. Above jr4
The secondary device is configured to send the output of the quasi-signal generating circuit to the transmitting terminal, and the signals of the speaker and microbond are cut off, and the quasi-acoustic coupling circuit transmits the output of the quasi-acoustic coupling circuit to the receiving terminal and the transmitting terminal. The control circuit of the main device calculates the gains of the two variable gain amplification means with respect to the level of the signal measured by the measurement means, and sets the gains to the two variable gain amplification means. 1 is a block diagram of a main device according to an embodiment of the present invention. In FIG. 1, a transmission signal from a microphone 1 is connected to a microphone amplifier 2. In FIG.

The output of the microphone amplifier 2 is connected to an analog digital converter 3 and a digitally controlled variable loss circuit 4. A digital signal of a transmission signal from the analog-to-digital converter 3 is connected to a control circuit 5. The output of the digitally controlled variable loss circuit 4 is connected to the break contact of the analog switch 6. A common contact of the analog switch 6 is connected to a transmitting channel amplifier 7. The output of the transmitting channel amplifier 7 is connected to the transmitting line terminal 8, and a transmitting signal is sent from the transmitting line terminal 8. A receiving channel amplifier 10 is connected to the receiving line terminal 9 through which the transmitting signal is received. The output of the receiving channel amplifier 10 is connected to an analog-to-digital converter 12 and a digitally controlled variable loss circuit 13. The digital signal of the reception signal from the analog-to-digital converter 12 is connected to the control circuit 5, and the control signal from the control circuit 5 is transmitted to the digitally controlled variable loss circuit 4.
13. Digitally controlled variable loss circuit 13
The output of is connected to the speaker amplifier 14. The output of the speaker amplifier 14 is connected to a speaker 15, and a reception signal is sent from the speaker 15. The input/output of the control signal of the control circuit 5 is the serial/parallel conversion type data transmitter/receiver 1
Connected to 6. The output of the serial-to-parallel conversion type data transceiver 16 is connected to the sending line terminal 8, and the input of the serial-to-parallel conversion type data transceiver 16 is connected to the receiving line terminal 9.

A manual switch 17 for measuring the sidetone coupling loss is connected to the control circuit 5. A control signal from the control circuit 5 is connected to the analog switch 6. A make contact of the analog switch 6 is connected to one input of the standard signal generating circuit 18, and the other input of the standard signal generating circuit 18 is grounded.

FIG. 2 is a block diagram of a slave device according to an embodiment of the present invention. In FIG. 2, a transmission signal from a microphone 1 is connected to a microbon amplifier 2. In FIG.

The output of the microphone amplifier 2 is connected to an analog-to-digital converter 3 and a digitally controlled variable loss circuit 4. A digital signal of a transmission signal from the analog-to-digital converter 3 is connected to a control circuit 5. The output of the digitally controlled variable loss circuit 4 is connected to the break contact of the analog switch 111. A common contact of the analog switch 111 is connected to the transmitting channel amplifier 7. The output of the transmitting channel amplifier 7 is connected to the transmitting line terminal 8, and a transmitting signal is sent from the transmitting line terminal 8. A receiving channel amplifier 10 is connected to the receiving line terminal 9 through which the transmitting signal is received. The output of the receiving channel amplifier 1o is connected to a common contact of the analog switch 112. A break contact of the analog switch 112 is connected to the analog-to-digital converter 12 and the digitally controlled variable loss circuit 13. The digital signal of the transmitting signal from the analog-to-digital converter 12 is connected to the control circuit 5, and the control signal from the control circuit 5 is connected to the digitally controlled variable loss circuit 4.13. The output of the digitally controlled variable loss circuit 13 is connected to a speaker amplifier 14. The output of the speaker amplifier is connected to the speaker 10, and the speaker 10 sends out a transmission signal. A control signal from the control circuit 5 is connected to a serial-to-parallel conversion data transmitter/receiver 16 . The output of the serial-to-parallel conversion type data transceiver 16 is connected to the sending line terminal 8, and the input of the serial-to-parallel conversion type data transceiver 16 is connected to the receiving line terminal 9. Control signals from the control circuit 5 are connected to the analog switches 111 and 112 and the pseudo-acoustic coupling circuit 19, respectively.

The input and output of the pseudo-acoustic coupling circuit 19 are connected to the make contacts of the analog switches 112 and 112, respectively.

FIG. 3 is a block configuration diagram showing a state in which a main device and a slave device of the present invention are connected via a communication line. In FIG. 3, conference telephone devices 101□ to 101N are respectively connected to the main device 100 via communication lines consisting of a communication path and a receiving communication path. Main device 100 and slave device 1011
~101N are connected to a conference microphone 105 and a conference speaker 106, respectively.

Here, the features of the present invention are as shown in FIGS. 1 and 2.
In the figure, part of the level detection measurement circuit and control circuit is surrounded by a dashed line. That is, the analog switch 6, manual switch I7, serial-to-parallel conversion data transmitter/receiver 16, and standard signal generation circuit 1 in FIG.
8 and a part of the control circuit 5, and a part of the serial-to-parallel conversion type data transmitter/receiver 16, analog switches 111 and 112, pseudo-acoustic coupling circuit 19, and a part of the control circuit 5 in FIG. It is a part.

The main device 100 and the slave devices 1011 to LOIN include a microphone 1, a microphone amplifier 2, an analog-to-digital converter 3.12, and a digitally controlled variable loss circuit 4.
13, consisting of a control circuit 5, a transmitting line amplifier 7, a transmitting line terminal 8, a receiving line terminal 9, a receiving line amplifier 10, a speaker amplifier 14, a speaker 15, and each level detection measurement circuit of the present invention. .

The operation of the conference telephone device having such a configuration will be explained. In FIGS. 1 and 2, in a normal conversation state, the analog switches 6, 111, and 112 are connected to the states shown in the figures, and the analog transmission signal sent from the microphone 1 through the microphone amplifier 2 is The analog-to-digital converter 3 converts the signal into a digital signal, which is then input to the control circuit 5 as data.

Similarly, the reception signal is converted into a digital signal by the analog-to-digital converter 12 through the reception line amplifier 10, and is input into the control circuit 5 as data.

The control circuit 5 compares the levels of both data and performs arithmetic processing to be described later. For example, if it is determined that the transmitted signal is larger than the received signal, the control circuit 5 controls the digitally controlled variable loss circuit 4. .13 control is performed to remove loss so that the speech gain on the sending channel becomes a steady gain, while inserting loss into the receiving channel. As a result, the audio signal picked up by the microphone 1 passes through the digitally controlled variable loss circuit 4 without loss, is amplified to the line output level by the transmitting line amplifier 7, and is then sent to the transmitting line terminal 8. be done.

On the other hand, when the device is in the transmitting state, the receiving basket input signal is amplified by the receiving channel amplifier 10, and is amplified by the digitally controlled variable loss circuit 13 in a predetermined manner to prevent howling. The signal is attenuated, power amplified by the speaker amplifier 14, and then applied to the speaker 15.

Conversely, when the level of the received signal is higher than the level of the transmitted signal, loss is inserted into the digitally controlled variable loss circuit 4 of the transmitting system by the same operation as described above. Then, the loss is removed in the digitally controlled variable loss circuit 13 of the receiver system so that a steady gain is obtained. The above control enables normal loudspeaker calls.

The transmission signal from microphone 1 is the transmission line end.

The manual switch 17 is used to measure the level of the reception signal sent from the slave 8 to the communication line and transmitted to the reception terminal 9 via the slave device connected to the communication line, that is, the amount of sidetone coupling loss. This can be done by manipulating.

Once the manual switch 17 of the main device 100 is closed,
The control circuit 5 of Dosei W100 transmits measurement mode information from the communication line through the serial-parallel conversion type data transmitter/receiver 16 to slave devices 10h to 1014 connected to the communication line.
Send to.

In the slave devices 1011 to 1014, this information is received by the serial-parallel conversion type data transmitter/receiver 16 and sent to the control circuit 5. In one slave device selected by this signal, the control circuit 5 controls the analog switch llz, 112 to separate the speech path group and connect it to the pseudo-acoustic coupling circuit 19.

In the pseudo-acoustic coupling circuit 19, each of the Western clothes [1
From 0h to 10IN, the circuit is configured to electrically equalize the amount of acoustic coupling between the sound generated from the speaker 15 and the microphone 1, that is, the amount of acoustic coupling loss.

On the other hand, in slave devices other than the selected one, the analog switch llz is controlled to connect the pseudo acoustic coupling circuit 1 from the communication path.
Control is performed to connect to 9. As a result, the main device 10
The slave device selected by 0 is now the slave device 10 in FIG.
11, in the slave device 1011, the received signal input from the receiving line terminal 9 is sent to the receiving channel amplifier 10-
The pseudo acoustic coupling circuit 19 becomes a loop connected to the transmitting line terminal 8 through the transmitting line amplifier 7, and becomes a gain loop with the same level of acoustic coupling from the speaker 15 to the microphone 1 in normal use. The other slave devices 1012 to 101N are electrically disconnected from the main device 100.

On the other hand, in the main device 100, the analog switch 6 is controlled and connected to the standard signal generation circuit 18, and a standard level signal is sent from the transmission line terminal 8.

When the above operations are completed, the control circuit 5 of the main device 100 calculates the side including the line gain level from the level ER measured by the analog-to-digital converter 12 and the standard signal level ST sent to the transmission line terminal 8. The acoustic coupling loss amount β is as follows.

β=ER−3゜The amount of sidetone coupling loss is calculated from the above formula, and this value is written into the memory circuit in the control circuit 5, and the calculated value is connected to the serial-parallel conversion type data transmitter/receiver 16. The data is sent to the slave device 1011 located in the slave device 1011, and is simultaneously written to the storage circuit in the control circuit 5 of the slave device 1011.

When the writing of the above data is completed, the main device 100 sends a control signal to the slave device 1011 and the slave device 1012, and each control circuit 5 controls the analog switch 112 in the slave device 1011. Device 1
00, and the analog switch 112 is controlled so that the slave device 1012 forms a loop circuit using the pseudo-acoustic coupling circuit 5.

Hereinafter, the same control as described above is performed for the main device 100 and the slave device 10.
11 to 101N are measured, and the data is written to the storage device in the control circuit 5.

At the time when the measurement of sidetone coupling ID loss with all the slave devices 1011 to 10IN is completed, the control circuit 5 of the main device 100 controls the analog switch 6, and also controls each of the slave devices 1011 to 101N. By controlling the analog switches 111 to 112 in the circuit 5 and returning the insertion loss of the digitally controlled variable loss circuit 4.13 to the loss control of the normal call state, it is possible to make a normal hands-free conference call. Become.

As described above, the sidetone coupling loss amount β including the line gain level is calculated and stored in the control circuit 5, and the measurement is completed.

In the control circuit 5 according to the present invention, the minimum insertion loss amount and the transmit/receive switching reference level, which are determined corresponding to the sidetone coupling loss amount β written in the storage circuit, are set by arithmetic processing and control is performed.

That is, the insertion loss of the digitally controlled variable loss circuit 4.13 is controlled by the minimum insertion amount and the optimum transmitting/receiving switching reference level according to the sidetone coupling loss amount β, and the actual level of the transmitting/receiving signal is controlled. By performing comparison and calculation with , it is possible to prevent the above-mentioned call blocking and to perform stable control.

The control circuit 5 can be easily realized using a microcomputer system.

After the device of the present invention measures the amount of sidetone viscosity loss, it automatically shifts to a normal conversation state and automatically performs calculation control based on the data. However, according to the customer's wishes, after the data is measured, the measured data is displayed and the data can be read again by human operation.

It is also possible to provide a device that is flexible in that it can be set using any of the following methods.

〔Effect of the invention〕

As explained above, the present invention provides a level detection and measurement circuit in a conference telephone device, processes and stores sidetone coupling loss amount, and controls a variable gain amplifier circuit using the stored data. Regardless of the acoustic conditions of the conference in which the conference phone is set up, there will be no blocking phenomenon, and it will be possible to switch between sending and receiving calls depending on the number of connected conference telephone devices. It has an excellent effect that can be rubbed to ensure that the sex is always optimal.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a main device according to an embodiment of the present invention. FIG. 2 is a block diagram of a slave device according to an embodiment of the present invention. FIG. 3 is a block configuration diagram showing a state in which a main device and a slave device of the present invention are connected via a communication line. 1...Microphone, 2...Microphone amplifier,
3.12...Analog-digital converter, 4.13.
... Digitally controlled variable loss circuit, 5... Control circuit, 6.11... Analog switch, 7... Sending line amplifier, 8... Sending line terminal, 9... Receiving line. Terminal, 10... Receiving channel amplifier, 14... Speaker amplifier, 15... Speaker, 16... Serial-parallel conversion data transmitter/receiver, 17... Manual switch, 1
8...Standard signal generation circuit, 19 pseudo acoustic coupling circuit, 1
00...Main device, 1011-101N...Slave device,
105...Microphone for conference phone, 106...Speaker for conference phone.

Claims (1)

[Claims] (11) A microphone, a variable gain amplification means for transmission that amplifies the output signal of this microphone, a transmission terminal to which the output of this variable gain amplification means is connected, a reception terminal, and this reception terminal. a receiving variable gain amplification means for amplifying the signal of the above, a speaker driven by the output of the variable gain amplification means, a control circuit for controlling the gains of the two variable gain amplification means, and an output of the control circuit. one main device including a data transmitting means for transmitting a control signal to the transmitting terminal, a micropon, a variable gain amplifying means for transmission that amplifies the output signal of the microphone, and an output of the variable gain amplifying means. A transmitting terminal and a receiving terminal connected to each other, a receiving variable gain amplifying means for amplifying the signal of the receiving terminal, a speaker driven by the output of the variable gain amplifying means, and a speaker driven by the output of the variable gain amplifying means; one or more slave devices including a control circuit for controlling gain and data receiving means for receiving a control signal arriving at the receiving terminal and providing it to the control circuit; A conference telephone device coupled by a transmission line such that a signal is transmitted to each reception terminal of the slave device, and a signal at a transmission terminal of the slave device is transmitted to each reception terminal of a slave device other than the main device and its slave device. In the main device, the main device is equipped with four standard signal generation circuits for sending a standard signal level to its transmitting terminal, and a measuring means for measuring the level of the signal arriving at its receiving terminal, and the slave device is equipped with: , a pseudo-acoustic coupling circuit capable of coupling a signal arriving at its reception terminal to its transmission terminal in a pseudo-electrical signal in a state in which the speaker and microphone of the slave device are acoustically coupled; The control circuit of the main device includes means for switching the main device to a measurement mode activated by manual operation, and means for outputting a measurement mode switching control signal to the data transmission means when switched to the measurement mode, The control circuit of the slave device includes means for switching the slave device to the measurement mode upon receiving the measurement mode switching control signal from the data receiving means, and when the slave device is switched to the measurement mode, the master device switches the slave device to the measurement mode. - The slave device is configured to send the output of the standard signal generation circuit to the transmission terminal in place of the output signal of the microphone, and the slave device has its speaker and microphone signals cut off, and the pseudo acoustic coupling circuit The control circuit of the main device is connected between the receiving terminal and the transmitting terminal.
A conference telephone device characterized by comprising means for calculating the gains of two variable gain amplifying means for the level of the signal measured by the measuring means and setting the gains to the two variable gain amplifying means.