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:
Aug. 31, 1982
Filed:
Aug. 18, 1980
Nippon Telegraph and Telephone Public Corporation, Tokyo, JP;
Nippon Tsushin Kogyo Kabushiki Kaisha, Kawasaki, JP;
Abstract
A key telephone system comprises a main equipment connected to at least one set of central office (CO) lines and capable of connecting thereto a plurality of key telephones. The main equipment includes a dual tone multifrequency (DTMF) sending circuit common to the key telephones, and the respective key telephones are connected to the main equipment through six wiring cables forming a pair of two-way voice frequency talking circuits and one two-way data transmitting circuit. A plurality of switching matrixes are included in the main equipment for selectively connecting the CO lines and the talking circuits, and also connecting the data transmitting circuit through the DTMF sending circuit to the CO lines and one of the talking circuits in the key telephone, whereby respective functions of hand-free talk-back and off-hook signalling during intercom talking, and speaker monitoring function during CO line talking are performable.
Data source: USPTO (United States Patent and Trademark Office) public patent records. Weekly synchronization. How IDiyas builds this profile