05640450 is referenced by 78 patents and cites 10 patents.

A speech circuit is disclosed which solves the serious problem of the degradation of the articulation of received speech voice in conventional circuits and permits pleasant communications at places where the background noise level is high. The circuit has a construction in which an input signal from a microphone is attenuated in correspondence to the background noise level to form a sidetone signal and a received speech signal from a speech channel is amplified in correspondence to the background noise level to form a new received speech signal.

Title
Speech circuit controlling sidetone signal by background noise level
Application Number
8/492753
Publication Number
5640450
Application Date
June 21, 1995
Publication Date
June 17, 1997
Inventor
Osamu Watanabe
Sendai
JP
Agent
Emmanuel J Burns & Lobato P C Lobato
Assignee
Kokusai Electric
JP
IPC
H04M 1/58
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