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:
Apr. 23, 1985
Filed:
Dec. 07, 1981
Masakazu Nishino, Yokohama, JP;
Hisashi Fujisaki, Tokyo, JP;
Nippon Telegraph & Telephone Public Corporation, Tokyo, JP;
Nippon Electric Co., Ltd., Tokyo, JP;
Abstract
A loudspeaking telephone system has a voice switch circuit in which voice signals on transmission and reception speech channels are respectively detected to produce control signals, and these control signals are compared to judge the levels of the voice signals on both the speech channels so that the switching between both the channels is effected under the control of loss of variable attenuators inserted in both the speech channels. The control signals corresponding to the voice signals on both the transmission and reception speech channels are converted through analog-to-digital conversion into digital values which are suitable for arithmetic operation. The arithmetic operation is such that the losses of the variable attenuators are automatically controlled in accordance with the use conditions of the loudspeaking telephone system to minimum values which can prevent the howling, transmitting blocking and receiving blocking.