Patents by Inventor Tetsuya Hiraji

Tetsuya Hiraji has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Key telephone system
    Patent number: 4935957
    Abstract: A key telephone system has an oscillation preventing circuit comprising a termination impedance element, said circuit is a switching element and connected between the ground and another circuit which includes an impedance compensating circuit, therein. The switching element is turned ON upon oscillation of the impedance compensating circuit due to any remarkable impedance fluctuation in the signal transmission line, thereby effectively suppressing such oscillation of the impedance compensating circuit to maintain a favorable transmission efficiency.
    Type: Grant
    Filed: June 6, 1989
    Date of Patent: June 19, 1990
    Assignees: Nitsuko Limited, Nippon Telegraph and Telephone Corporation
    Inventors: Kinzi Tanaka, Kuniaki Shimoseki, Tetsuya Hiraji, Yoshiji Tanimoto, Minoru Okumura