Patents by Inventor Andrew James Drysdale

Andrew James Drysdale 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 line integrity monitoring system
    Patent number: 6014426
    Abstract: A system for monitoring for integrity of a telephone line connected between a central monitoring station and a subscriber's equipment which comprises a first module for initiating transmission of an identification code from the subscriber's equipment along the telephone line to be monitored to the central monitoring station during an incoming ringing signal; a recognition module response to said transmitted identification code for recognizing the identification code; and a second module for dropping the line after said transmitted identification codes has been recognized and before the line has been picked up.
    Type: Grant
    Filed: December 15, 1997
    Date of Patent: January 11, 2000
    Assignee: Pyronix Limited
    Inventors: Andrew James Drysdale, Juan Sebastian Herrera