JPS60121869A - Conference telephone set - Google Patents

Abstract

PURPOSE:To enhance communication properties by calculating acoustic coupling losses in a conference telephone terminal and losses to be inserted into a sound switch circuit from the number of simultaneously connected stations and controlling the sound switch circuit in accordance with the calculated value. CONSTITUTION:In accordance with an approximate acoustic coupling loss written in a measured value control circuit and the number of simultaneously connected stations, a measurement control circuit 7 calculates inserted losses inserted into respective sound switches 4-1-4-n, and controls inserted losses of the circuits 4-1-4-n according to the operated result. After the circuit 7 has terminated measurement and calculation, a termination signal is transmitted to a control circuit 8. When the circuit 8 receives the termination signal, transmission of noises to an inner band noise generation transmission circuit 6 is stopped, and changeover switches 5-1-5-n are controlled so that transmitting paths 9-1- 9-n will be connected to the side of the circuits 4-1-4-n.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to a conference telephone system that connects a plurality of terminals to each other. In particular, the present invention relates to a conference telephone device that is equipped with a microphone and a speaker in the same room, and has an audio switch that prevents the howling phenomenon that occurs between them.

[Description of prior art]

Conventionally, in a conference telephone device in which a plurality of hands-free conference telephone terminals of this type with a microphone and a speaker are combined so that calls can be made between each terminal, a howling phenomenon occurs due to acoustic coupling between the terminal's microphone and the speaker. The voice switch circuit used to prevent this problem compares the magnitude of the transmitting voice signal level with the magnitude of the received signal level, and removes the loss for the channel with the higher signal level, increasing the steady-state gain. It operates so that a loss is inserted into the communication path where the signal level is lower.

In general, the smaller the amount of loss inserted into the voice switch circuit, the more natural the naturalness of mutual communication is maintained, and the larger the amount of loss in the voice switch, the more ``drops in conversation'' occur and the interactivity deteriorates.

The amount of loss injected into the audio switch circuit of a conventional conference phone device is determined by the maximum number of terminals the device can connect and the worst-case acoustic coupling between the speaker and micropon at each terminal. It is fixed at a large value that can reliably prevent howling even in the case of Therefore, even if the actual number of simultaneously connected terminals and the acoustic coupling loss between the speaker and the micropon in each terminal were better than the assumed worst-case values, there was a serious drawback that the interactivity deteriorated at all. .

[Purpose of the invention]

The present invention does not deal with the worst value of audio coupling and give a fixed loss, but instead adjusts the loss to each terminal according to the number of conference terminals connected simultaneously and the acoustic coupling loss of the speaker to microphone of each conference telephone terminal. 141 to the audio switch circuit of each terminal
To provide a conference telephone device which can further improve conversational performance by setting the loss caused by people to an appropriate IJJ level.

[Features of the invention]

The present invention provides a plurality of transmitting path terminals each connected to a plurality of conference telephone terminals, a plurality of receiving path terminals respectively connected to the plurality of conference telephone terminals, and a signal from each transmitting path terminal. A two-way bridge circuit couples the signal, and a Uemachi channel terminal and '
cy, (or) an audio switch circuit that is connected between the receiving line terminal and the bidirectional bridge circuit and causes a loss to the passing signal, wherein the audio switching circuit provides a loss to the passing signal. A first means is configured to variably control the loss caused, and transmits a test signal of a predetermined level to each of the sending path terminals under the control of the control circuit, and a first means that sends a test signal of a predetermined level to each of the sending path terminals under the control of the control circuit; and a second means for measuring and storing the signal level of the transmitter, and in the measurement mode, a test signal is sent from the first means to each transmitting line terminal, and the signal level appearing at the receiving line terminal at this time is It is controlled to be measured and stored by the second means, and in the call mode, the loss of the voice switch circuit is controlled according to the value stored in the second means. shall be.

Zunawaji is a conference telephone device that combines multiple conference terminals so that conference participants can talk to conference participants in remote locations using microphones and speakers. In a conference telephone device having an audio switch circuit that adjusts the received audio signal level and the transmitted audio signal level so as to prevent howling caused by acoustic coupling between the speaker and the speaker, from the speaker of the terminal that forms the loop that causes howling. An in-band noise generation and transmission circuit is provided to automatically measure the approximate acoustic coupling loss to the microphone by operating a measurement preset switch for each terminal on the conference telephone equipment side, and the noise is transmitted to each terminal. Measure this in-band noise level and the loop noise level where the in-band noise amplified by the speakers of each terminal (11) goes around the microphone and is sent to the receiving channel again, and based on these measurement values, the sending level and the receiving level The number of simultaneously connected terminals is measured by detecting the difference between the acoustic coupling loss and the feedback noise level of the approximate terminal described above, and based on this measurement result, the signal level of the voice switch circuit is determined. a measurement control circuit that controls the adjustment amount (insertion loss amount); a switching circuit that switches between the output of the in-band noise sending circuit and the transmission signal from the bidirectional bridge circuit and connects it to the transmission path; Contains a preset switch for measurement.When this switch is operated, the output of the in-band noise reproduction and transmission circuit described in 2 is connected to the transmission line only when the approximate acoustic coupling loss of each terminal is being measured. In order to control the switching circuit and measure the approximate acoustic coupling loss, the in-band noise generation and transmission circuit described in 2.
In order to generate and transmit noise, and for the measurement control circuit described in Section 2, measure the approximate acoustic coupling loss and the number of connected terminals for each terminal, and based on the measurement results, It is characterized in that it is constructed with a control circuit that operates to control the signal level control amount of the circuit, and can improve the interactivity as a conference phone.

[Explanation based on examples]

Next, a conference telephone device according to an embodiment of the present invention will be explained based on the drawings.

The figure is a block diagram showing the configuration of a conference telephone device according to an embodiment of the present invention. The conference telephone device 1 connects a transmission path 9 to conference telephone terminals 2-1 to 2-n located at n1llil mutually distant locations.
-1 to 9-n and reception channels 10-1 to 10-n, respectively. Telephone lines, exchanges, two-line lines, etc. may be inserted in the transmitting lines 9-1 to 9-n and receiving lines 10-1 to 10-n, but they are simply shown as four-line lines here. . This conference phone terminal 2-1~
2-n are each equipped with microphones 11-1 to ILn and speakers 12-1 to 12-n.

The conference telephone device 1 includes the receiving channels 10-1 to 10-.
Audio switch circuits 4-1 to 4- connected to n respectively
n, a bidirectional Brinon circuit 3 connected to the audio switch circuits 4-1 to 4-n and input/output, and an input side connected to the audio switch circuits 4-1 to 4-n. 9
= switching circuits 5-1 to 5 whose output sides are connected to 1 to 9-n
- B, sending channels 9-1 to 9-n and receiving channels 1o-1 to
Each audio switch circuit receives input from 10-n 4-1 to 4
-n measurement control circuit 7 and this measurement control circuit 7
The image 17 includes a control circuit 8 connected to input and output the control circuit 8, and an in-band noise generation/sending circuit 6 which receives output from the control circuit 8 and outputs to each switching circuit 5-1 to 5-n. It is being

The operation of the apparatus according to the embodiment of the present invention configured as described above will be explained. In the device according to the embodiment of the present invention, each conference telephone terminal 2-
]~2-n from the speakers 12-1-12-n,
α is the acoustic coupling +i loss to the microphones 11-1 to 11-n, and Ps is the transmission output to each conference phone terminal 2-1 to 2-n.
, the number of callers from each conference telephone terminal 2-1 to 2-n is P.
Let r be the approximate acoustic coupling loss α = Ps −
It is measured as Pr.

When a preset and a tossona (not shown) included in the control circuit 8 are operated, the control circuit 8 controls the transmission channels 9-1 to 9-n.
The switching circuits 5-1 to 5-n are controlled so that the in-band ♀ is connected to the sound generation and transmission circuit 6, and the noise is output to the in-band IL sound generation and transmission circuit 6. Control.

By this control, the noise transmitted from the in-band noise generation and transmission circuit 6 is amplified by the speakers 11-1-11-n of each of the conference telephone terminals 2-1 to 2-n. This amplified noise includes a spectrum in a wide range of the transmission frequency band of the conference telephone device 1, and is collected by the microphones 12-1 to 12-n, and transmitted to the respective receiving channels 10-1 to 12-n. 10-n.

The measurement control circuit 7 is started by a measurement start signal from the control circuit 8, and transmits voice output to each terminal at points Sl, S2, ---3n in the figure, and R1, R2, ---17+4.
The power of the receiver from each terminal at the point is detected by a circuit including a rectifying and smoothing circuit or an A/D converter (not shown), and the acoustic coupling loss at each conference telephone terminal 2-1 to 2-n is approximated. In addition to calculating the coupling loss D', the number of receiving channels (the number of simultaneously connected terminals) in which there is human power is calculated from the size of the receiver's power level, and the measured value is stored in a measured value storage circuit (not shown) in the control circuit 8. It's crowded.

In general, the amount of gain control required to prevent howling in a conference telephone system, that is, the device that should be inserted into the voice switch circuit, is
It is determined by the acoustic coupling loss of -1 to 12-n and the microphones 11-1 to 11-n and the number of simultaneously connected terminals.

The measurement control circuit 7 is based on the theory of ``dual series'' and records measured values 4.
Based on the approximate acoustic coupling loss written in one circuit and the number of simultaneously connected terminals, each audio switch circuit 4-1 to 4-n
Calculate the insertion loss to be inserted into each of the voice switches based on the calculation result.

The insertion loss of child circuits 4-1 to 4-n is controlled.

The measurement control circuit 7 sends a completion signal to the control circuit 8 after completing the measurement and calculation. Further, the control circuit 8
When the end signal from the measurement control circuit 7 is received, the in-band noise generation and transmission circuit 6 is made to stop transmitting the second noise, and the transmission paths 91 to 9-n are connected to the voice switch circuit 4. Switching circuit 5-1 to be connected to -1 to 4-n side
~5-n is controlled.

With the above two operations, the measurement and calculation of the approximate acoustic coupling loss of each terminal and the number of simultaneously connected terminals, and the insertion loss/liligt inserted into each audio switch circuit are completed, and the device becomes ready for communication. .

Next, the operation of the device according to the embodiment of the present invention in the call state will be explained. In the figure, a case will be explained in which, for example, a speech voice is added to the microphone 12-1 of the conference telephone terminal 2-1. The audio signal picked up by the microphone 12-1 is amplified by the amplifier of the conference telephone terminal 2-1, and is applied to the receiver terminal of the audio switch circuit 4-1 of this device.

The voice switch circuit 11-1 compares the level of the transmitting human power signal from the bidirectional bridge circuit 3 and the level of the receiving human power signal from the receiving channel 10-1, and assigns it to the channel with the higher signal level, resulting in a steady gain. 1B loss, which is controlled by the measurement control circuit 7 shown in -, is inserted in line with the communication path where the signal and the bell are small. Other audio switch circuit 4-2
, -------4-n are performed in the same manner.

Therefore, the audio switch circuit 4-1 is connected to the conference telephone terminal 2-
The receiver's power from 1 is amplified with a steady gain and added to the receiver's power of the bidirectional circuit 3. On the other hand, voice suinochi circuit 4-
The ID loss calculated by the measurement control circuit 7 is inserted into the transmission path No. 1.

The bidirectional bridge circuit 3 distributes the signal to the transmitter terminals of the voice switch circuits 4-2, . . . 4-n at the same level as the receiver input signal applied from the voice switch circuit 4-1. 73 voice switch circuit 4-2, -------4-n receives the human power signal for transmitting voice distributed from the bidirectional bridge circuit 3, amplifies this signal with a steady gain, and transmits the human power signal for transmitting voice 1♂89-2. , -9-n4
Send this. On the other hand, the loss calculated by the measurement control circuit 7 is inserted into the receiving path of the audio switching circuits 4-2 and -40. The microphone audio signal of the conference telephone terminal 2-1 sent to the transmission paths 4-2, ---4-n is transmitted to the speaker 12-2-- of the conference telephone terminal 2-2 ---=2-n. 12-
The sound will be amplified at n.

Conference call & i: J end 22, -2-n microbon 8
A similar operation occurs when a voice is added to each conference phone I7i!
It is possible to make calls between non-Japanese people.

As described above, the conference telephone device of the present invention can always set the insertion 1B loss of the audio switch to an optimal value according to the approximate acoustic coupling loss of each conference terminal and the number of simultaneously connected stations.

[9) Effects of the Invention] As explained above, the present invention measures the approximate acoustic coupling loss and the number of simultaneously connected stations in each conference telephone terminal, and
By calculating the lfJ loss to be inserted into each voice switch circuit necessary to prevent ringing in a conference call from the measured value, and controlling each voice switch circuit based on the calculated value, There is a good way to achieve the best call quality.

[Brief explanation of drawings]

The figure is a block diagram showing the configuration of a conference telephone device according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Conference telephone device, 2-1 to 2-11... Conference telephone terminal, 3... Bidirectional bridge circuit, 4-1 to 4-n
...Audio switch circuit, 5-1 to 5-n...Switching circuit, 6...In-band i゛11 sound generation and sending circuit, 7...
Measurement control circuit, 8... control circuit, 9-1 to 9-n- sending path, 10-1-IQ-n=- receiving path, 11-1 to 1
1-n...Microphone, 12-1 to 12-n...
speaker.

Claims (1)

[Scope of Claims] fil A plurality of sending path terminals each connected to a plurality of conference telephone terminals, a plurality of receiving path terminals respectively connected to the plurality of conference telephone devices, and a signal of each sending path terminal, respectively. a bidirectional bridge circuit coupled to a signal on the receiving line terminal; and a bidirectional bridge circuit coupled to the sending line terminal and/or the receiving line to prevent howling due to acoustic coupling in the conference telephone terminal when there is a signal on the sending line terminal. In a conference telephone device equipped with an audio switch circuit that is connected between a terminal and a two-way bridge circuit and that causes a loss in the passing signal, the audio switch circuit has a voice switch circuit that causes a loss in the passing signal. a first means for sending a test signal of a predetermined level to each of the transmitting path terminals under the control of the control circuit; & a second means for measuring and storing the signal level of the transmitter, and in the measurement mode, transmitting a test signal from the first means to each transmission line terminal,
At this time, the signal level appearing at the receiving line terminal is measured and recorded by the second means, and in the talk mode, the signal level appearing at the receiving line terminal is measured and recorded by the second means. A conference telephone device characterized in that it is configured such that II4 loss of the audio switch circuit is controlled.