Patents by Inventor Havelin D. St. John

Havelin D. St. John 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).

  • Magnetically linked theft sensing system
    Patent number: 4973945
    Abstract: A theft sensing system which provides an output signal and actuation of an alarm upon cut off of its electrical power source. The system includes an oscillator which provides an output signal. The amplitude of the oscillator signal is modulated responsive to disconnection of an appliance from its power source. A signal level detector provides an output signal when the modulation amplitude varies beyond a predetermined level. The output signal from the level detector indicates disconnection of the appliance from a AC power source and is used to provide an alarm and permanently disable the appliance.
    Type: Grant
    Filed: October 10, 1989
    Date of Patent: November 27, 1990
    Inventor: Havelin D. St. John