Patents by Inventor Edward G. T. Johnson

Edward G. T. Johnson 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).

  • Electret microphone circuit
    Patent number: 4361735
    Abstract: An electroacoustic transducer for a microphone comprises an electret wherein an additional capacitance substantially greater than the capacitance normally inherent in the electret is connected in parallel with the electret. The additional capacitance may be of the order of 10 times greater than the capacitance normally inherent in the electret and may be produced inherently in the transducer or by a separate component connected to the transducer.
    Type: Grant
    Filed: May 5, 1980
    Date of Patent: November 30, 1982
    Assignee: The Post Office
    Inventors: Edward G. T. Johnson, Adrian J. Morgan
  • Audio teleconferencing
    Patent number: 4237339
    Abstract: An electro-acoustic terminal unit for use in an audio teleconferencing system comprises a loudspeaker and one or more microphones each having a sensitivity which is directionally dependent and exhibits at least one null or substantially null position. The loudspeaker and microphones are rigidly mounted on a boom and the microphones are so located and orientated relative to the loudspeaker that the null position is directed towards the loudspeaker.
    Type: Grant
    Filed: October 18, 1978
    Date of Patent: December 2, 1980
    Assignee: The Post Office
    Inventors: John G. Bunting, Robin C. Cross, David R. Guard, Ian S. Groves, Edward G. T. Johnson, Alan E. Stevens