Patents by Inventor Stephen D. Alvey

Stephen D. Alvey 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).

  • Interface circuits for connection to non-dedicated telephone lines
    Patent number: 4378470
    Abstract: Receive and transmit paths, for example for frequency shift keyed signals, are coupled to an interface circuit including a line transformer which is permanently connected to the telephone line via a high impedance. The effect of this high impedance on received signals is counteracted by an amplifier and/or a tuned circuit comprising a winding of the transformer. Switches in the interface circuit, responsive to received signals, serve to by-pass the high impedance, and reduce the gain of the amplifier and/or eliminate the effect of the tuned circuit, to permit normal coupling of signals between the telephone line and the receive and transmit paths.
    Type: Grant
    Filed: March 25, 1981
    Date of Patent: March 29, 1983
    Assignee: Northern Telecom Limited
    Inventors: Tapio H. Murto, Stephen D. Alvey