Patents by Inventor DeWitt Paul Smith

DeWitt Paul Smith 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).

  • Telephone subscriber line circuit
    Patent number: 4056691
    Abstract: A communication line interface circuit including a floating current source supplying a constant current substantially independent of loop length is disclosed. The line interface circuit is provided with circuitry for line supervision and the detection of dial pulse signaling.
    Type: Grant
    Filed: January 5, 1977
    Date of Patent: November 1, 1977
    Assignee: Bell Telephone Laboratories, Incorporated
    Inventors: Laimons Freimanis, Harry Edward Mussman, DeWitt Paul Smith
  • Telephone line battery feed circuit
    Patent number: 4007335
    Abstract: A telephone line battery feed circuit for supplying talking current to a subscriber subset and at the same time reducing common mode interference signals. The inputs of a differential operational amplifier are coupled to a telephone line and the outputs of the differential operational amplifier are coupled to a battery feed circuit. The battery feed circuit provides talking current to the subscriber subset and the differential operational amplifier presents a high impedance between the battery and the telephone line to differential voice signals while at the same time presenting a low impedance between the telephone line and the battery for common mode interference signals thereby reducing the latter.
    Type: Grant
    Filed: November 12, 1975
    Date of Patent: February 8, 1977
    Assignee: Bell Telephone Laboratories, Incorporated
    Inventors: Irvine Keers Hetherington, DeWitt Paul Smith