The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 09, 1997
Filed:
Jan. 28, 1994
Shinichi Suizu, Tokyo, JP;
Yuji Umemoto, Tokyo, JP;
Kabushiki Kaisha Toshiba, Kawasaki, JP;
Abstract
A dual mode mobile telephone apparatus includes an echo canceler. In a hands-free conversation mode, a received speech output from a loudspeaker is input to a microphone by circulate cross talk and transmitted to the destination side so that an acoustic echo may be generated. The echo canceler cancels the acoustic echo. A center clipper for eliminating a residual echo signal having a level lower than a preset level is provided at the output side of the echo canceler. Enabling/disabling operations of the center clipper are controlled in accordance with a volume control level for a reception signal and transmission/reception state detection signal from a voice switching circuit which controls gains of reception channel and transmission channel in the opposite directions.