Title:
ECHO CANCELLER
Document Type and Number:
Japanese Patent JP3250439
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To attain natural 2-way speech by suppressing howling or echo in the case of hand-free speech in telephone speech and avoiding one-way speech.
SOLUTION: A microcomputer 16 receives transmission voice amplification data from an A/D converter 15 and multiplex a reference constant with the data. The transmission voice amplification data are given to the microcomputer 16, which provides an output of corresponding PWM control signal to a transmission voice signal level control circuit 19. Furthermore, the result of multiplication is subtracted from the reference constant. The reference constant is selected so that the total gain in the path of a reception voice signal level control circuit 12 and a transmission voice signal level control circuit 19 is the '1' or below. The subtracted PWM control signal is given to reception voice signal level control circuit 12, in which the level is reduced and a resulting reception voice amplification signal is fed to a reception output amplifier 13.
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Inventors:
Yoshi Kenji Oka
Shuji Horii
Shuji Horii
Application Number:
JP32016195A
Publication Date:
January 28, 2002
Filing Date:
December 08, 1995
Export Citation:
Assignee:
Matsushita Electric Industrial Co., Ltd
International Classes:
H03H21/00; H03H17/00; H04B3/23; H04M1/60; (IPC1-7): H04B3/23; H03H17/00; H03H21/00; H04M1/60
Domestic Patent References:
| JP6229227A | ||||
| JP678046A | ||||
| JP662104A | ||||
| JP677857A | ||||
| JP1311794A |
Attorney, Agent or Firm:
Fumio Iwahashi (2 others)
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