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:
Mar. 15, 1977
Filed:
Aug. 22, 1975
Takashi Araseki, Tokyo, JA;
Kazuo Ochiai, Tokyo, JA;
Nippon Electric Company, Ltd., Tokyo, JA;
Abstract
An echo suppressor employed in systems interconnecting a two-wire circuit with a four-wire circuit for substantially eliminating 'talker's echo' and for selectively attenuating the calling party's voice signal when the called party at the two-wire line begins speaking. The signal levels of signals on both paths of the four-wire circuit are measured to extract the maximum values of the signals for succeeding time intervals. The extracted value of the outgoing path signal is divided by the extracted value of the incoming path signal to generate an attenuation factor value. This value is multiplied by the value of the voice signal in the incoming path to generate an estimated leakage level signal. When this level is greater than the signal level in the output path (i.e. when there is no outgoing voice signal) the outgoing path is disconnected to prevent a talker's echo signal from being transmitted thereby. When the signal on the outgoing path is greater than the estimated leakage level signal the outgoing path is not disconnected, and an attenuation circuit in the incoming path is activated to attenuate signals in the incoming path. Delay means are provided to prevent the disconnection of the outgoing path at the initial and terminal ends of a voice signal.