JPH05300559A - Voice quality assuring system for private branch exchange of public exclusive connection - Google Patents

Abstract

PURPOSE:To improve the talking voice quality by providing an automatic gain controller and an echo canceler between the central office line trunk and private line trunk of a private branch exchange PBX. CONSTITUTION:An echo canceler 6 erases the echoes which are produced when the voice signals sent from a private line 2 are returned by a 2/4-wire converting circuit 8 of a central office line trunk 4 and a 2/4-wire converting circuit 10 included in an office exchange of a public network 1. An automatic gain controller 7 is included in a channel reaching to the line 2 from the network 1 and keeps a fixed talking level. That is, the reduced talking level is compensated by the controller 7 for the voice signals sent from the network 1. Thus the compensated voice signals are sent to the line 2. Furthermore the voice signals sent to the network 1 from the line 2 are erased by the canceler 6 even though these signals are returned by both circuits 8 and 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice quality compensation system for a private branch exchange in a public private connection for connecting a public network and a private line.

[0002]

2. Description of the Related Art At present, a public connection for voice is not implemented, and no consideration is given to voice quality compensation when it is implemented.

[0003]

When the public network and the leased line are connected, the following voice is not considered because the method for compensating the voice quality in the connection between the public network and the leased line is not considered at present. Quality problems occur.

In an analog public network using a general telephone, there is a transmission loss of up to about 25 dB. Therefore, when a public network-dedicated line or public network-dedicated line-public network connection is made, there is a transmission loss in the public network. It is conceivable that the transmission loss on the leased line may accumulate and the call level may drop significantly, making it difficult to hear the voice of the other party. Further, the transmission delay time also increases due to the accumulation of the public network and the dedicated line, and thus echo may easily occur.

Therefore, an object of the present invention is to eliminate such a problem, to compensate for a transmission loss when connecting a public network and a leased line, and to eliminate an echo due to a transmission delay. It is to provide a voice quality assurance method for a private branch exchange in a public-private connection that compensates for the above.

[0006]

The voice quality assurance system for a private branch exchange in the public private connection according to the solution of the present invention for solving the above problems is a public private connection for connecting a public network and a private line. The switch is provided with an automatic gain controller for compensating the level of a voice signal coming from the public network and an echo canceller for canceling an echo generated in a 2-wire to 4-wire conversion circuit.

[0007]

EXAMPLE An example of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram of an embodiment of the present invention. In FIG. 1, the analog public network 1 is a 2-wire to 4-wire conversion circuit 9 such as a hybrid circuit, as shown in a simplified manner for explanation. A two-wire line that is a subscriber line and a four-wire line that is a transmission line are connected to each other by a line 10. This public network 1 is a private branch exchange (Private branch).
Anch exchange; hereinafter referred to as PBX) 3 is connected to the dedicated line 2. The PBX 3 has the following structure.
A two-line to four-line conversion circuit 8 of a station line trunk 4 connected to the public network 1 and an echo canceller 6 are connected so that a signal converted into a four-line system by the two-line to four-line conversion circuit 8 can be exchanged. Further, the signal output from the echo canceller 6 is input and connected to the automatic gain controller 7. The signal output from the automatic gain controller 7 is input to the dedicated line trunk 5 and further connected to the dedicated line trunk 5 so as to be output to the dedicated line 2. On the other hand, the signal input from the dedicated line 2 via the dedicated line trunk 5 is connected via the echo canceller 6 so as to be input to the other terminal of the 2-line to 4-line conversion circuit 8 of the station line trunk 4. , And public network 1
It is connected to be output to.

The operation of the above arrangement will be described below. In the echo canceller 6, the voice signal coming from the private line 2 side is returned by the 2-line-4 line conversion circuit 8 of the station line trunk 4 and the 2-line-4 line conversion circuit 10 in the central office switch in the public network 1. It has the function of canceling the echo generated by this. Further, the automatic gain controller 7 is in the speech path from the public network 1 to the leased line 2 and has a function of maintaining a certain speech level, for example, -15 dBm. As a result, the speech level of the voice signal coming from the public network 1 is compensated by the automatic gain controller 7, and then the voice signal is sent to the leased line 2. Further, even if the voice signal sent from the private line 2 side to the public network 1 is returned by the 2-wire to 4-wire conversion circuits 8 and 10, it is erased by the echo canceller 6, so that an echo is sent to the private line 2 side. There is no such thing. As described above, since the automatic gain controller 7 and the echo canceller 6 are provided, the automatic gain controller 7 compensates the speech level of the voice signal lowered in the public network 1 and the 2-wire to 4-wire conversion circuits 8 and 10 are provided. Since the echo cancelled by the echo canceller 6 is returned, the public-private connection capable of good voice communication can be realized.

[0009]

As described above, according to the present invention, by providing the automatic gain controller and the echo canceller between the PBX local line trunk and the private line trunk in the public exclusive connection, the speech level due to the transmission loss in the public network is reduced. It is possible to compensate for the decrease, and since the echo canceller cancels the echo generated by the accumulation of transmission delays between the public network and the leased line, a better voice call can be realized.

[Brief description of drawings]

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

[Explanation of Codes] 1 public network 2 private line 3 PBX 4 office line trunk 5 private line trunk 6 echo canceller 7 automatic gain controller 8, 9, 10 2-wire to 4-wire conversion circuit

Claims (1)

[Claims] 1. An automatic gain controller for compensating a level of a voice signal coming from the public network, and a 2-wire to 4-wire conversion circuit in a private branch exchange capable of connecting a public network and a private line. A voice quality assurance system for a private branch exchange in a public-private connection, which is provided with an echo canceller for canceling the echo generated in.