Patents by Inventor James L. Lignell

James L. Lignell 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).

  • Presence detecting system with self-checking
    Patent number: 3970846
    Abstract: This invention relates to presence sensing systems and more particularly to such systems which utilize beams of radiant energy, such as light beams, to detect the presence of a person or an object within a predetermined space. Additionally the invention relates to presence detecting systems combined with self-checking means to ensure that the detection system is operating properly.
    Type: Grant
    Filed: August 15, 1974
    Date of Patent: July 20, 1976
    Assignee: Xenex Corporation
    Inventors: George L. Schofield, Jr., James L. Lignell