JPH0495451A - Conference call equipment - Google Patents

Abstract

PURPOSE:To allow the conference call equipment to be immune to noises by integrating an expander, an attenuator, a compressor and further an adder into one pattern recognition device ROM so as to decrease the number of times of signal transmission reception. CONSTITUTION:A transmission speech from a telephone set 11 of a conference participant is converted into a digital signal by a CODEC 12, subject to time division exchange by a time division exchange circuit 13 and the result is fed to a digital conference call circuit 23. The digital signal sent to the circuit 23 is fed to a latch circuit 21, to which latches till all voice data of conference participants to be added are sent and when the data are arranged entirely the latched voice data are outputted to a pattern recognition device 22. The recognition device 22 outputs the data which is already calculated for each process of expansion, addition, attenuation and compression in advance corresponding to the input signal. The output data is fed to the CODEC 12 via the time division exchange circuit 13, restored into an analog signal as the reception call of conference participants.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a conference call device used in private digital electronic exchanges, digital key telephone main devices, and the like.

BACKGROUND OF THE INVENTION The following are the main types of conference call systems generally used in private digital electronic exchanges and the like.

1) Simple addition method 2) Maximum value control method 3) Chairman type method 1) Simple addition method is as shown in Figure 2 (a).
This is a method in which the transmitting calls of conference participants B and C other than the conference participants are added together by an adder 1 and counted as their own received calls. In the maximum value control method (2), as shown in FIG. 2(b), the level determiner 2 selects the person B who speaks the loudest among the conference participants, and calculates the level of each conference participant A, B, and C. This is a method for receiving calls. 3)
The chairperson type method is a method in which a chairperson C is selected from among the conference participants and a speaker B is selected by operating the call selector 4 by dialing etc., as shown in Fig. 2 (cl). ) simple addition method is often used.

There are two ways to implement a simple addition conference call circuit: an analog type and a digital type.

An example of an analog type configuration is shown in FIG. The voices of speakers A, B, and C that have passed through the telephone set 5 are digitized by a codec 6, and the analog signal converted into an analog signal by a codec 7 is generated by an analog adder 8 configured using an OP amplifier or the like. be. In the analog type, in a private digital electronic exchange, etc., the -degree digital signal is returned to an analog signal by the codec 7, and after addition, it is sent to the codec 7 again.
It is not used much at present because it needs to be converted into a digital signal and the system requires circuits for the number of conference groups needed at one time.

An example of a digital type configuration is shown in FIG. The voices of each speaker are added together as digital signals. The digital type is currently the mainstream method for in-house digital electronic exchanges and the like.

The operation of the digital simple addition method will be explained below with reference to FIG.

The conference participants' telephone calls (analog signals) are converted into digital signals (PCM code voice data) by a codec (encoder/decoder) 12, and are time-division exchanged by a time-division exchange circuit 13. and sent to the digital conference call circuit 14. The digital signal sent to the digital conference call circuit 14 is first subjected to non-linear to linear conversion (expansion) in the expander 15. (The PCM code (μ law, A law) is a nonlinear signal.) The digital signal with the first expansion is then held in the latch circuit 16, and the latch circuit 16 captures the audio data of the conference participants to be added. The audio data held at that point is added to adder 1.
7, and the adder 17 adds the input audio data. For example, if there are three participants in the conference, the audio data of the other three people other than the receiver are taken in, and if there are four participants in the conference, the audio data of the other three people other than the receiver are captured and added. If the audio data is simply added, the volume will be louder by the amount of the addition, and the volume will not be optimal, so the added audio data will be sent to the attenuator 18, where the volume will be adjusted (attenuated).

The attenuated audio data is further input to the compressor 19, subjected to line-to-nonlinear conversion, and decoded into a digital signal (PCM code). This decoded digital signal is sent to the codec 12 through the time division switching circuit 13, and converted back into an analog signal to be received by the conference participants, and through this process, a conference call can be made. Since the expander 15, attenuator 18, and one compressor are a kind of slam recognizer, R
It is often composed of OM. Note that the adder 17 is
A method of configuring a high-speed arithmetic unit such as an SP (digital signaling processor) and including the decompressor 15, compressor 19, and attenuator 18 therein, or improving the addition speed when there are many conference participants. There are ways to achieve this.

Further, the digital conference call circuit system is efficient because by operating the adders sequentially, one adder can add the audio data of a plurality of conference groups.

Problems to be Solved by the Invention However, the conventional digital conference call circuit described above has the following problems.

1) It is necessary to prepare an expander, attenuator, compressor, and multiple pattern recognizers, resulting in a large number of component parts.

2) Adder and multiple pattern recognizers (stretchers, attenuators,
It is necessary to send and receive signals to and from the compressor many times,
It is easily affected by noise due to simultaneous operations, etc.

3) As the number of conference call participants increases, the adder configuration becomes more complex.

4) When a DSP is used, the circuit scale increases.

The present invention solves these conventional problems, and aims to provide an excellent digital conference call device that has fewer circuit components, is small in circuit scale, and is resistant to noise. be.

Means for Solving the Problems In order to achieve the above object, the present invention decompresses and decompresses digital audio data in the digital simple addition method in advance.
A pattern recognizer (ROM) in which calculation results of addition, attenuation, and compression are written is provided, and digital audio data held by a latch circuit is supplied to the pattern recognizer.

[However, the operation in the above configuration is as follows. Digital audio data from conference participants is held in a latch circuit, and when all the audio data to be added is captured, it is supplied to the pattern recognizer, and by reading out the calculation results that have been calculated and stored in the pattern recognizer in advance. Processing is performed through predetermined expansion, addition, attenuation, and compression processes. Therefore, the number of times signals are transmitted and received is reduced, making it less susceptible to noise, and the circuit configuration becomes extremely simple.

Embodiment FIG. 1 shows the configuration of an embodiment of the present invention. The same parts in FIG. 1 as in FIG. 4 are given the same reference numerals. 21 is a latch circuit that holds audio data (digital signals) sent from conference participants (telephones), and when all of the conference participants' audio data to be added is taken in, the expander, attenuator,
A pattern recognizer that combines a compressor and an adder (
ROM) 22. It is assumed that the pattern recognizer 22 is composed of a ROM in which the processes of expansion, addition, attenuation, and compression are calculated and written in advance for the input audio data pattern sent therein.

Next, the operation of the above embodiment will be explained.

Transmissions (analog signals) from conference participants' telephones 11 are converted into digital signals (PCM code: voice data) by a codec 12, time-division exchanged by a time-division exchange circuit 13, and sent to a digital conference call circuit 23. Sent. The digital signal sent to the digital conference call circuit 23 is first sent to the latch circuit 21. Latch circuit 2
1, the voice data of the conference participants to be added is held until all the voice data of the conference participants are sent in, and when all the voice data is collected, the held voice data is output to the pattern recognizer 22. The pattern recognizer 22 calculates in advance the expansion, addition, attenuation, and compression processes corresponding to the input signal and outputs written data. This ratio data is sent to the time division switching circuit 13.
The signal is then sent to the codec 12, where it is converted back into an analog signal and received by conference participants.

In this way, according to the above embodiment, the digital conference call circuit 23 can be constructed from only the latch 21 circuit and the pattern recognizer 22, and the advantage is that the circuit can be constructed from a small number of components. have

Furthermore, in the digital conference call circuit 23 of the present invention, the number of times the signal is transmitted and received with the pattern recognizer 22 is once.
It has the advantage of being resistant to noise.

Effects of the Invention As is clear from the above embodiments, the present invention has the following effects.

1) By combining the expander, attenuator, compressor, and adder into one pattern recognizer (ROM), it is possible to reduce the number of times signals are sent and received, making it less susceptible to noise. You can.

2) By combining the expander, attenuator, compressor, and adder into one pattern recognizer (ROM), the circuit scale can be reduced.

3) Since the adder is included in the pattern recognizer, the number of circuit components is reduced and the circuit configuration becomes simple.

4. Brief description of the figures FIG. 1 is a schematic block diagram showing an embodiment of the conference call device of the present invention, and FIG. 2 is an explanatory diagram of each conventional conference call system.
(al is simple addition method, (bl is maximum value control method, (c
1 is a conceptual diagram showing a chairperson type system, FIG. 3 is a schematic block diagram of a conventional analog conference call circuit, and FIG. 4 is a schematic block diagram of a conventional digital conference call circuit.

11...Telephone, 12...Codec, 13...
Time division switching circuit, 14... digital conference call circuit,
15...Extender, 16...Latch circuit, 17...Adder, 18...Attenuator, 19...Compressor, 21...
・Latch circuit, 22... Pattern recognizer, 23...
Digital conference call circuit.

Name of agent: Patent attorney Takahaka Awano mistress No. figure / (a) (b-n Ku ■

Claims (1)

[Claims] A conference system comprising means for converting input audio into a digital signal, a latch circuit for holding the digital signal, and a pattern recognizer that has stored in advance the results of expansion, addition, attenuation, and compression operations based on the input audio data. Telephone device.