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Title:
VOICE QUALITY ASSURING SYSTEM FOR PRIVATE BRANCH EXCHANGE OF PUBLIC EXCLUSIVE CONNECTION
Document Type and Number:
Japanese Patent JPH05300559
Kind Code:
A
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.


Inventors:
KIKUCHI OSAMU
Application Number:
JP1992000104287
Publication Date:
November 12, 1993
Filing Date:
April 23, 1992
Export Citation:
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Assignee:
NEC CORP
International Classes:
H04B3/23; H04Q3/42; H04Q3/58; (IPC1-7): H04Q3/58; H04B3/23; H04Q3/42
Domestic Patent References:
JPH03255800A1991-11-14
JPS61256854A1986-11-14
JPH04207794A1992-07-29
Attorney, Agent or Firm:
岩佐 義幸