Kokusai Denshin Denwa Kabushiki Kaisha

Masayuki Takeuchi

Akira Sato

Sotokichi Shintani

Masaru Fukai

Masamichi Niiya

An adaptive control type echo suppressor which compares the levels of voice signals of sending and receiving paths by a first comparator with each other and cuts off the sending path to suppress an echo when the level of the voice signal of the receiving path is higher than the level of the voice signal of the sending path. A control loop is provided for applying the voice signal from the receiving path to a second comparator via a variable loss circuit for comparing the peak of the integrated value of the same with the peak level of the integrated value of the voice signal of the sending path to effect adaptive control of the variable loss circuit by the output of the second comparator in a manner to reduce the output of the second comparator to zero. Each of the integrated values are obtained under a relatively long time constant characteristic to prevent influence of noise of the sending and the receiving paths, and the output of the variable loss circuit is applied as the voice signal of the receiving path to the first comparator.

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Hino, Japan

Masayuki Takeuchi