Patents by Inventor Hachishiro Kawamura

Hachishiro Kawamura 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).

  • Patent number: 4000375
    Abstract: An automatic call transfer circuit for a plurality of telephones which are connected in parallel respectively between a pair of telephone lines, relay coils each one of which is connected with a different one of the telephones respectively and condensers each one of which is connected in parallel with a different one of the relay coils respectively. Energizing of each one of the relay coils makes it possible to use only the telephone which is connected to the energized relay coil. The circuit further comprises a current holding circuit which has at least one Zener diode for holding a current between the telephone lines at a moment of call transfer between the telephones in a telephone conversation where the current is flowing in a prescribed single direction.
    Type: Grant
    Filed: February 20, 1975
    Date of Patent: December 28, 1976
    Inventor: Hachishiro Kawamura