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:
Jan. 30, 1990
Filed:
Jan. 17, 1989
Takao Suzuki, Tokyo, JP;
Yuichi Shiraki, Tokyo, JP;
Osamu Noguchi, Tokyo, JP;
Yasuo Shoji, Tokyo, JP;
Oki Electric Industry Co., Ltd., Tokyo, JP;
Abstract
A digital speech interpolation (DSI) system serves multiple PCM channels by multiplexing them to a single PCM signal, detecting the presence of speech on individual channels according to an adaptive power threshold, removing silent portions of the channel signals, and recombining them into a signal with fewer channels. A central echo canceler is provided between the DSI transmitter and the multiplexer, thus eliminating the need for a separate echo protection device at each terminal. The central echo canceler provides information to the speech detector enabling the speech dectector to avoid updating the adaptive power threshold when center clipping or double-talk occurs, thus preventing erratic speech detection performance. The speech detector also has a hangover controller that prevents speech dropouts by prolonging speech dectect intervals by an amount that is adjusted according to the length of the interval, and according to the current adaptive power threshold; this form of control enables a constant activity ratio to be maintained under varying noise levels. Benefits include improved communication quality and reduced system cost.