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. 10, 1985
Filed:
Dec. 01, 1982
Yuichi Morikawa, Zushi, JP;
Kazuo Saito, Yokohama, JP;
Eiichi Amada, Kokubunji, JP;
Hirotoshi Shirasu, Yokohama, JP;
Nippon Telegraph & Telephone Public Corp., Tokyo, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
For the purpose of realizing a line circuit, especially a two-wire four-wire conversion circuit of a telephone exchange in the form of LSI and providing the conversion circuit with an impedance which is suitable to a side tone characteristic of the telephone set, in a line circuit composed of a hybrid circuit wherein the four-wire input line is connected to the two-wire subscriber line via a buffer amplifier and a terminating impedance and in addition the four-wire output line is connected to the output of a subtractor which subtracts an input signal of the four-wire input line passed through a filter circuit from a signal fed from the two-wire subscriber line, the terminating impedance is formed by a resistor component and in addition a feedback circuit having such a transfer characteristic that the impedance of the line circuit seen from the two-wire subscriber line side will become a specified complex impedance is installed between a line which couples the two-wire subscriber line to the subtractor and an input of the buffer amplifier.