JPH05206897A - Voice conference equipment for two-wire line - Google Patents

Abstract

PURPOSE:To provide the 2-wire line use voice conference equipment preventing a ring tone caused in a closed loop. CONSTITUTION:A circuit 4 shifting a frequency of a transmission signal is provided in a transmission circuit from an echo canceller circuit 3 till a hybrid circuit 5, and a circuit 4 shifting a frequency of the transmission signal passing through a hybrid circuit 5 is provided between the hybrid circuit 5 and the echo canceller 2 in a reception circuit. Thus, the production of a ring tone is prevented by shifting the frequency of the signal in closed loops 1,2 causing bypass of the transmission signal to the reception circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-line type voice conference device.

[0002]

2. Description of the Related Art In a conventional two-line type voice conference device,
As shown in FIG. 2, the hybrid circuit 5 connected to the two-wire line, the transmission circuit for guiding the transmission signal from the microphone 1 to the hybrid circuit (H) 5, and the hybrid circuit 5 coming from the two-wire line through the hybrid circuit 5. An echo canceller circuit (EC) which is connected between a receiving circuit for guiding the received signal to the speaker 9 and a transmitting circuit and a receiving circuit, and for canceling an echo signal generated when the received signal sneak into the microphone 1 from the speaker 9 by acoustic coupling. ) 3, and an echo canceller circuit (EC) 10 for canceling a signal that passes from the transmission circuit through the hybrid circuit 5 to the reception circuit.

Further, since the transmission signal from the other party passes through the two-wire system and suffers line loss, a receiving amplifier 7 for amplifying the transmission signal is provided.

[0004]

However, in the above-mentioned conventional device, as shown in FIG. 2, a closed loop 1 and a closed loop 2 are generated due to the hybrid circuit 5 used for connecting the two-wire line. May cause ringing.

Further, since the closed loop 2 passes through the two-wire line, the loop gain does not increase due to the line loss and the ringing is unlikely to occur. The signal that wraps around and the reception signal are added and amplified by the reception amplifier 7, and the loop gain increases. Furthermore, since the loss that occurs in the closed loop 1 is only in the hybrid circuit 5, there is a problem that a sound is produced.

The present invention has been made in view of the above-mentioned conventional circumstances. Therefore, the object of the present invention is to solve the above-mentioned problems inherent in the prior art and prevent the ringing sound generated in the closed loop 1. To provide a new two-line voice conference device.

[0007]

In order to achieve the above object, a two-wire line audio conference apparatus according to the present invention comprises a hybrid circuit connected to a two-line line and a transmission signal generated from a microphone. A transmission circuit for guiding to a hybrid circuit, a reception circuit for guiding a reception signal coming from the two-wire line through the hybrid circuit to a speaker, and a reception signal connected between the transmission circuit and the reception circuit, the reception signal being emitted from the speaker to the microphone. A first shift circuit that has an echo canceller circuit for canceling an echo signal that wraps around due to coupling, and that is provided on the way from the echo canceller circuit in the transmission circuit to the hybrid circuit and that shifts the frequency of the transmission signal. , The transmission signal is provided on the way from the hybrid circuit in the receiving circuit to the echo canceller circuit. It is characterized in that a second shift circuit for shifting the frequency of the head circuit comes goes around through the signal.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the accompanying drawings with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

Referring to FIG. 1, a transmission signal emitted from a microphone 1 of a device 1 is transmitted to an analog-digital converter (A / D) 2, an echo canceller circuit (EC) 3, a frequency shift circuit (UP) 4. After passing through the transmission circuit provided, it is sent to the two-wire line via the hybrid circuit (H) 5. The received signal coming from the device 2 through the two-wire line passes through the receiving circuit including the frequency shift circuit (UP) 4, the amplifier 7 and the digital-analog converter (D / A) 8 and is reproduced as voice by the speaker 9. To be done.

A major feature of the present invention is that the frequency of the closed loop 1 generated by the transmission signal coming from the hybrid circuit 5 and passing through the reception circuit is changed by the frequency shift circuit (UP) 4, so that the same frequency is maintained in the closed loop 1. Is no longer present and the sound is prevented.

Frequency shift circuits 4 and 6 of devices 1 and 2
Realizes a normal call by using a combination of UP shift and DOWN shift.

The UP shift of the frequency shift circuit is
This is a circuit that adds 1 Hz to the signal frequency.
The shift is a circuit that subtracts 1 Hz from the signal frequency.

The echo canceller circuit (E
C) 3 is an echo canceller for canceling indoor echo, that is, an echo generated by acoustic coupling from the speaker 9 to the microphone 1 as shown by the broken line arrow A in FIG.

[0015]

As described above, according to the present invention,
In a device connected to a two-wire line, the effect of preventing the generation of ringing noise can be obtained by shifting the frequency of the signal in the closed loop in which the transmission signal passes through the hybrid circuit and wraps around to the reception circuit.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Microphone 2 ... Analog-digital converter (A / D) 3, 10 ... Echo canceller circuit (EC) 4 ... Frequency shift circuit (UP) 5 ... Hybrid circuit 6 ... Frequency shift circuit (DOWN) 7 ... Amplification circuit 8 … Digital-analog converter (D / A) 9… Speaker

Claims (2)

[Claims] 1. A hybrid circuit connected to a two-wire line, a transmission circuit for guiding a transmission signal emitted from a microphone to the hybrid circuit, and a reception signal for arriving from the line through the hybrid circuit to a speaker. Audio for a two-wire line having a receiving circuit and an echo canceller connected between the transmitting circuit and the receiving circuit for canceling an echo signal generated when the received signal circulates from the speaker to the microphone by acoustic coupling. In the conference device, a first shift circuit provided in the way from the echo canceller circuit in the transmission circuit to the hybrid circuit, for shifting the frequency of the transmission signal, and a hybrid circuit in the reception circuit to the echo canceller circuit are provided. Provided on the way, the transmission signal passes through the hybrid circuit And a second shift circuit for shifting the frequency of an incoming signal. 2. A voice conferencing device of another type, wherein the first and second shift circuits are composed of a circuit pair for adding a predetermined frequency to a signal frequency, and are connected to the voice conferencing device by the two-wire line. 2. The two-wire line audio conference apparatus according to claim 1, further comprising a shift circuit configured to subtract a predetermined frequency from a signal frequency.